workbench_utils.py

"""Utility functions for Islandora Workbench.
"""

import os
import sys
import json
from json.decoder import JSONDecodeError
import csv
import openpyxl
import time
import string
import re
import copy
import logging
import datetime
import requests
import subprocess
import hashlib
import mimetypes
import collections
import urllib.parse
from pathlib import Path
from ruamel.yaml import YAML, YAMLError
from unidecode import unidecode
from progress_bar import InitBar
import edtf_validate.valid_edtf
import shutil
import itertools
import http.client


# Set some global variables.
yaml = YAML()

EXECUTION_START_TIME = datetime.datetime.now()
INTEGRATION_MODULE_MIN_VERSION = '1.0'
# Workaround for https://github.com/mjordan/islandora_workbench/issues/360.
http.client._MAXHEADERS = 10000
http_response_times = []
# Global lists of terms to reduce queries to Drupal.
checked_terms = list()
newly_created_terms = list()
# These are the Drupal field names on the standard types of media.
file_fields = [
    'field_media_file',
    'field_media_image',
    'field_media_document',
    'field_media_audio_file',
    'field_media_video_file']


def set_media_type(config, filepath, file_fieldname, csv_row):
    """Using either the 'media_type' or 'media_types_override' configuration
       setting, determine which media bundle type to use.

       Parameters
       ----------
       config : dict
           The configuration object defined by set_config_defaults().
       filepath: string
           The value of the CSV 'file' column.
        file_fieldname: string
            The name of the CSV column containing the filename (usually 'file').
        csv_row : OrderedDict
            The CSV row for the current item.
       Returns
       -------
       string
           A string naming the configured media type, e.g. 'image'.
    """
    if 'media_type' in config:
        return config['media_type']

    # Determine if the incomtimg filepath matches a registered eEmbed media type.
    oembed_media_type = get_oembed_url_media_type(config, filepath)
    if oembed_media_type is not None:
        return oembed_media_type

    if filepath.strip().startswith('http'):
        preprocessed_file_path = get_preprocessed_file_path(config, file_fieldname, csv_row)
        filename = preprocessed_file_path.split('/')[-1]
        extension = filename.split('.')[-1]
        extension_with_dot = '.' + extension
    else:
        extension_with_dot = os.path.splitext(filepath)[-1]

    extension = extension_with_dot[1:]
    normalized_extension = extension.lower()
    media_type = 'file'
    for types in config['media_types']:
        for type, extensions in types.items():
            if normalized_extension in extensions:
                media_type = type
    if 'media_types_override' in config:
        for override in config['media_types_override']:
            for type, extensions in override.items():
                if normalized_extension in extensions:
                    media_type = type

    # If extension isn't in one of the lists, default to 'file' bundle.
    return media_type


def get_oembed_url_media_type(config, filepath):
    """Since oEmbed remote media (e.g. remove video) don't have extensions, which we
       use to detect the media type of local files, we use remote URL patterns to
       detect if the value of the 'file' columns is an oEmbed media.

       Parameters
       ----------
       config : dict
           The configuration object defined by set_config_defaults().
       filepath: string
           The value of the CSV 'file' column.
       Returns
       -------
       mtype
           A string naming the detected media type, e.g. 'remote_video', or None
           if the filepath does not start with a configured provider URL.
    """
    for oembed_provider in config['oembed_providers']:
        for mtype, provider_urls in oembed_provider.items():
            for provider_url in provider_urls:
                if filepath.startswith(provider_url):
                    return mtype

    return None


def get_oembed_media_types(config):
    # Get a list of the registered oEmbed media types from config.
    media_types = list()
    for omt in config['oembed_providers']:
        keys = list(omt.keys())
        media_types.append(keys[0])
    return media_types


def set_model_from_extension(file_name, config):
    """Using configuration options, determine which Islandora Model value
       to assign to nodes created from files. Options are either a single model
       or a set of mappings from file extenstion to Islandora Model term ID.
    """
    if config['task'] != 'create_from_files':
        return None

    if 'model' in config:
        return config['model']

    extension_with_dot = os.path.splitext(file_name)[1]
    extension = extension_with_dot[1:]
    normalized_extension = extension.lower()
    for model_tids in config['models']:
        for tid, extensions in model_tids.items():
            if str(tid).startswith('http'):
                tid = get_term_id_from_uri(config, tid)
            if normalized_extension in extensions:
                return tid
            # If the file's extension is not listed in the config,
            # We use the term ID that contains an empty extension.
            if '' in extensions:
                return tid


def issue_request(
        config,
        method,
        path,
        headers=dict(),
        json='',
        data='',
        query={}):
    """Issue the HTTP request to Drupal. Note: calls to non-Drupal URLs
       do not use this function.
    """
    if not config['password']:
        message = 'Password for Drupal user not found. Please add the "password" option to your configuration ' + \
            'file or provide the Drupal user\'s password in your ISLANDORA_WORKBENCH_PASSWORD environment variable.'
        logging.error(message)
        sys.exit("Error: " + message)

    if config['check'] is False:
        if 'pause' in config and method in ['POST', 'PUT', 'PATCH', 'DELETE'] and value_is_numeric(config['pause']):
            time.sleep(int(config['pause']))

    headers.update({'User-Agent': config['user_agent']})

    # The trailing / is stripped in config, but we do it here too, just in case.
    config['host'] = config['host'].rstrip('/')
    if config['host'] in path:
        url = path
    else:
        # Since we remove the trailing / from the hostname, we need to ensure
        # that there is a / separating the host from the path.
        if not path.startswith('/'):
            path = '/' + path
        url = config['host'] + path

    if config['log_request_url'] is True:
        logging.info(method + ' ' + url)

    if method == 'GET':
        if config['log_headers'] is True:
            logging.info(headers)
        response = requests.get(
            url,
            allow_redirects=config['allow_redirects'],
            verify=config['secure_ssl_only'],
            auth=(config['username'], config['password']),
            params=query,
            headers=headers
        )
    if method == 'HEAD':
        if config['log_headers'] is True:
            logging.info(headers)
        response = requests.head(
            url,
            allow_redirects=config['allow_redirects'],
            verify=config['secure_ssl_only'],
            auth=(config['username'], config['password']),
            headers=headers
        )
    if method == 'POST':
        if config['log_headers'] is True:
            logging.info(headers)
        if config['log_json'] is True:
            logging.info(json)
        response = requests.post(
            url,
            allow_redirects=config['allow_redirects'],
            verify=config['secure_ssl_only'],
            auth=(config['username'], config['password']),
            headers=headers,
            json=json,
            data=data
        )
    if method == 'PUT':
        if config['log_headers'] is True:
            logging.info(headers)
        if config['log_json'] is True:
            logging.info(json)
        response = requests.put(
            url,
            allow_redirects=config['allow_redirects'],
            verify=config['secure_ssl_only'],
            auth=(config['username'], config['password']),
            headers=headers,
            json=json,
            data=data
        )
    if method == 'PATCH':
        if config['log_headers'] is True:
            logging.info(headers)
        if config['log_json'] is True:
            logging.info(json)
        response = requests.patch(
            url,
            allow_redirects=config['allow_redirects'],
            verify=config['secure_ssl_only'],
            auth=(config['username'], config['password']),
            headers=headers,
            json=json,
            data=data
        )
    if method == 'DELETE':
        if config['log_headers'] is True:
            logging.info(headers)
        response = requests.delete(
            url,
            allow_redirects=config['allow_redirects'],
            verify=config['secure_ssl_only'],
            auth=(config['username'], config['password']),
            headers=headers
        )

    if config['log_response_status_code'] is True:
        logging.info(response.status_code)

    if config['log_response_body'] is True:
        logging.info(response.text)

    response_time = response.elapsed.total_seconds()
    average_response_time = calculate_response_time_trend(config, response_time)

    log_response_time_value = copy.copy(config['log_response_time'])
    if 'adaptive_pause' in config and value_is_numeric(config['adaptive_pause']):
        # Pause defined in config['adaptive_pause'] is included in the response time,
        # so we subtract it to get the "unpaused" response time.
        if average_response_time is not None and (response_time - int(config['adaptive_pause'])) > (average_response_time * int(config['adaptive_pause_threshold'])):
            message = "HTTP requests paused for " + str(config['adaptive_pause']) + " seconds because request in next log entry " + \
                "exceeded adaptive threshold of " + str(config['adaptive_pause_threshold']) + "."
            time.sleep(int(config['adaptive_pause']))
            logging.info(message)
            # Enable response time logging if we surpass the adaptive pause threashold.
            config['log_response_time'] = True

    if config['log_response_time'] is True:
        parsed_query_string = urllib.parse.urlparse(url).query
        if len(parsed_query_string):
            url_for_logging = urllib.parse.urlparse(url).path + '?' + parsed_query_string
        else:
            url_for_logging = urllib.parse.urlparse(url).path
        if 'adaptive_pause' in config and value_is_numeric(config['adaptive_pause']):
            response_time = response_time - int(config['adaptive_pause'])
        response_time_trend_entry = {'method': method, 'response': response.status_code, 'url': url_for_logging, 'response_time': response_time, 'average_response_time': average_response_time}
        logging.info(response_time_trend_entry)
        # Set this config option back to what it was before we updated in above.
        config['log_response_time'] = log_response_time_value

    return response


def convert_semver_to_number(version_string):
    """Convert a Semantic Version number (e.g. Drupal's) string to a number. We only need the major
       and minor numbers (e.g. 9.2).

        Parameters
        ----------
        version_string: string
            The version string as retrieved from Drupal.
        Returns
        -------
        tuple
            A tuple containing the major and minor Drupal core version numbers as integers.
    """
    parts = version_string.split('.')
    parts = parts[:2]
    int_parts = [int(part) for part in parts]
    version_tuple = tuple(int_parts)
    return version_tuple


def get_drupal_core_version(config):
    """Get Drupal's version number.

        Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        Returns
        -------
        string|False
            The Drupal core version number string (i.e., may contain -dev, etc.).
    """
    url = config['host'] + '/islandora_workbench_integration/core_version'
    response = issue_request(config, 'GET', url)
    if response.status_code == 200:
        version_body = json.loads(response.text)
        return version_body['core_version']
    else:
        logging.warning(
            "Attempt to get Drupal core version number returned a %s status code", response.status_code)
        return False


def check_drupal_core_version(config):
    """Used during --check.
    """
    drupal_core_version = get_drupal_core_version(config)
    if drupal_core_version is not False:
        core_version_number = convert_semver_to_number(drupal_core_version)
    else:
        message = "Workbench cannot determine Drupal's version number."
        logging.error(message)
        sys.exit('Error: ' + message)
    if core_version_number < tuple([8, 6]):
        message = "Warning: Media creation in your version of Drupal (" + \
            drupal_core_version + \
            ") is less reliable than in Drupal 8.6 or higher."
        print(message)


def set_drupal_8(config):
    """Used for integration tests only, in which case it will either be True or False.
    """
    if config['drupal_8'] is not None:
        return config['drupal_8']

    drupal_8 = False
    drupal_core_version_string = get_drupal_core_version(config)
    if drupal_core_version_string is not False:
        drupal_core_version = convert_semver_to_number(drupal_core_version_string)
    else:
        message = "Workbench cannot determine Drupal's version number."
        logging.error(message)
        sys.exit('Error: ' + message)
    if drupal_core_version < tuple([8, 6]):
        drupal_8 = True
    return drupal_8


def check_integration_module_version(config):
    version = get_integration_module_version(config)

    if version is False:
        message = "Workbench cannot determine the Islandora Workbench Integration module's version number. It must be version " + \
            str(INTEGRATION_MODULE_MIN_VERSION) + ' or higher.'
        logging.error(message)
        sys.exit('Error: ' + message)
    else:
        version_number = convert_semver_to_number(version)
        minimum_version_number = convert_semver_to_number(INTEGRATION_MODULE_MIN_VERSION)
        if version_number < minimum_version_number:
            message = "The Islandora Workbench Integration module installed on " + config['host'] + " must be" + \
                " upgraded to version " + str(INTEGRATION_MODULE_MIN_VERSION) + '.'
            logging.error(message)
            sys.exit('Error: ' + message)
        else:
            logging.info("OK, Islandora Workbench Integration module installed on " + config['host'] + " is at version " + str(version) + '.')


def get_integration_module_version(config):
    """Get the Islandora Workbench Integration module's version number.

        Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        Returns
        -------
        string|False
            The version number string (i.e., may contain -dev, etc.) from the
            Islandora Workbench Integration module.
    """
    url = config['host'] + '/islandora_workbench_integration/version'
    response = issue_request(config, 'GET', url)
    if response.status_code == 200:
        version_body = json.loads(response.text)
        return version_body['integration_module_version']
    else:
        logging.warning(
            "Attempt to get the Islandora Workbench Integration module's version number returned a %s status code", response.status_code)
        return False


def ping_node(config, nid, method='HEAD', return_json=False):
    """Ping the node to see if it exists.

       Note that HEAD requests do not return a response body.

        Parameters
        ----------
        method: string
            Either 'HEAD' or 'GET'.
        return_json: boolean

        Returns
        ------
            True if method is HEAD and node was found, the response JSON response
            body if method was GET. False if request returns a non-allowed status code.
    """
    if value_is_numeric(nid) is False:
        nid = get_nid_from_url_alias(config, nid)
    url = config['host'] + '/node/' + str(nid) + '?_format=json'
    response = issue_request(config, method.upper(), url)
    allowed_status_codes = [200, 301, 302]
    if response.status_code in allowed_status_codes:
        if return_json is True:
            return response.text
        else:
            return True
    else:
        logging.warning("Node ping (%s) on %s returned a %s status code", method.upper(), url, response.status_code)
        return False


def ping_url_alias(config, url_alias):
    """Ping the URL alias to see if it exists. Return the status code.
    """
    url = config['host'] + url_alias + '?_format=json'
    response = issue_request(config, 'GET', url)
    return response.status_code


def ping_vocabulary(config, vocab_id):
    """Ping the node to see if it exists.
    """
    url = config['host'] + '/entity/taxonomy_vocabulary/' + vocab_id.strip() + '?_format=json'
    response = issue_request(config, 'GET', url)
    if response.status_code == 200:
        return True
    else:
        logging.warning("Node ping (HEAD) on %s returned a %s status code", url, response.status_code)
        return False


def ping_islandora(config, print_message=True):
    """Connect to Islandora in prep for subsequent HTTP requests.
    """
    # First, test a known request that requires Administrator-level permissions.
    url = config['host'] + '/islandora_workbench_integration/version'
    try:
        host_response = issue_request(config, 'GET', url)
    except requests.exceptions.Timeout as err_timeout:
        message = 'Workbench timed out trying to reach ' + \
            config['host'] + '. Please verify the "host" setting in your configuration ' + \
            'and check your network connection.'
        logging.error(message)
        logging.error(err_timeout)
        sys.exit('Error: ' + message)
    except requests.exceptions.ConnectionError as error_connection:
        message = 'Workbench cannot connect to ' + \
            config['host'] + '. Please verify the "host" setting in your configuration ' + \
            'and check your network connection.'
        logging.error(message)
        logging.error(error_connection)
        sys.exit('Error: ' + message)

    if host_response.status_code == 404:
        message = 'Workbench cannot detect whether the Islandora Workbench Integration module is ' + \
            'enabled on ' + config['host'] + '. Please ensure it is enabled and that its version is ' + \
            str(INTEGRATION_MODULE_MIN_VERSION) + ' or higher.'
        logging.error(message)
        sys.exit('Error: ' + message)

    not_authorized = [401, 403]
    if host_response.status_code in not_authorized:
        message = 'Workbench can connect to ' + \
            config['host'] + ' but the user "' + config['username'] + \
            '" does not have sufficient permissions to continue, or the credentials are invalid.'
        logging.error(message)
        sys.exit('Error: ' + message)

    if config['secure_ssl_only'] is True:
        message = "OK, connection to Drupal at " + config['host'] + " verified."
    else:
        message = "OK, connection to Drupal at " + config['host'] + " verified. Ignoring SSL certificates."
    if print_message is True:
        logging.info(message)
        print(message)


def ping_content_type(config):
    url = f"{config['host']}/entity/entity_form_display/node.{config['content_type']}.default?_format=json"
    return issue_request(config, 'GET', url).status_code


def ping_view_endpoint(config, view_url):
    """Verifies that the View REST endpoint is accessible.
    """
    """Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        view_url
            The View's REST export path.
        Returns
        -------
        int
            The HTTP response code.
    """
    return issue_request(config, 'HEAD', view_url).status_code


def ping_entity_reference_view_endpoint(config, fieldname, hander_settings):
    """Verifies that the REST endpoint of the View is accessible. The path to this endpoint
       is defined in the configuration file's 'entity_reference_view_endpoints' option.

       Necessary for entity reference fields configured as "Views: Filter by an entity reference View".
       Unlike Views endpoints for taxonomy entity reference fields configured using the "default"
       entity reference method, the Islandora Workbench Integration module does not provide a generic
       Views REST endpoint that can be used to validate values in this type of field.
    """
    """Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        fieldname: string
            The name of the Drupal field.
        handler_settings : dict
            The handler_settings values from the field's configuration.
            # handler_settings': {'view': {'view_name': 'mj_entity_reference_test', 'display_name': 'entity_reference_1', 'arguments': []}}
        Returns
        -------
        bool
            True if the REST endpoint is accessible, False if not.
    """
    endpoint_mappings = get_entity_reference_view_endpoints(config)
    if len(endpoint_mappings) == 0:
        logging.warning("The 'entity_reference_view_endpoints' option in your configuration file does not contain any field-Views endpoint mappings.")
        return False
    if fieldname not in endpoint_mappings:
        logging.warning('The field "' + fieldname + '" is not in your "entity_reference_view_endpoints" configuration option.')
        return False

    # E.g., "http://localhost:8000/issue_452_test?name=xxx&_format=json"
    url = config['host'] + endpoint_mappings[fieldname] + '?name=xxx&_format=json'
    response = issue_request(config, 'GET', url)
    if response.status_code == 200:
        return True
    else:
        logging.warning("View REST export ping (HEAD) on %s returned a %s status code", url, response.status_code)
        return False


def ping_media_bundle(config, bundle_name):
    """Ping the Media bunlde/type to see if it exists. Return the status code,
       a 200 if it exists or a 404 if it doesn't exist or the Media Type REST resource
       is not enabled on the target Drupal.
    """
    url = config['host'] + '/entity/media_type/' + bundle_name + '?_format=json'
    response = issue_request(config, 'GET', url)
    return response.status_code


def ping_remote_file(config, url):
    """Logging, exiting, etc. happens in caller, except on requests error.
    """
    sections = urllib.parse.urlparse(url)
    try:
        response = requests.head(url, allow_redirects=True, verify=config['secure_ssl_only'])
        return response.status_code
    except requests.exceptions.Timeout as err_timeout:
        message = 'Workbench timed out trying to reach ' + \
            sections.netloc + ' while connecting to ' + url + '. Please verify that URL and check your network connection.'
        logging.error(message)
        logging.error(err_timeout)
        sys.exit('Error: ' + message)
    except requests.exceptions.ConnectionError as error_connection:
        message = 'Workbench cannot connect to ' + \
            sections.netloc + ' while connecting to ' + url + '. Please verify that URL and check your network connection.'
        logging.error(message)
        logging.error(error_connection)
        sys.exit('Error: ' + message)


def get_nid_from_url_alias(config, url_alias):
    """Gets a node ID from a URL alias. This function also works
       canonical URLs, e.g. http://localhost:8000/node/1648.
    """
    """
        Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        url_alias : string
            The full URL alias (or canonical URL), including http://, etc.
        Returns
        -------
        int
            The node ID, or False if the URL cannot be found.
    """
    url = url_alias + '?_format=json'
    response = issue_request(config, 'GET', url)
    if response.status_code != 200:
        return False
    else:
        node = json.loads(response.text)
        return node['nid'][0]['value']


def get_mid_from_media_url_alias(config, url_alias):
    """Gets a media ID from a media URL alias. This function also works
       with canonical URLs, e.g. http://localhost:8000/media/1234.
    """
    """
        Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        url_alias : string
            The full URL alias (or canonical URL), including http://, etc.
        Returns
        -------
        int
            The media ID, or False if the URL cannot be found.
    """
    url = url_alias + '?_format=json'
    response = issue_request(config, 'GET', url)
    if response.status_code != 200:
        return False
    else:
        node = json.loads(response.text)
        return node['mid'][0]['value']


def get_node_title_from_nid(config, node_id):
    """Get node title from Drupal.

    """
    node_url = config['host'] + '/node/' + node_id + '?_format=json'
    node_response = issue_request(config, 'GET', node_url)
    if node_response.status_code == 200:
        node_dict = json.loads(node_response.text)
        return node_dict['title'][0]['value']
    else:
        return False


def get_field_definitions(config, entity_type, bundle_type=None):
    """Get field definitions from Drupal.

        Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        entity_type : string
            One of 'node', 'media', 'taxonomy_term', or 'paragraph'.
        bundle_type : string
            None for nodes (the content type can optionally be gotten from config),
            the vocabulary name, or the media type (image', 'document', 'audio',
            'video', 'file', etc.).
        Returns
        -------
        dict
            A dictionary with field names as keys and values arrays containing
            field config data. Config data varies slightly by entity type.
    """
    ping_islandora(config, print_message=False)
    field_definitions = {}

    if entity_type == 'node':
        bundle_type = config['content_type']
        fields = get_entity_fields(config, entity_type, bundle_type)
        for fieldname in fields:
            field_definitions[fieldname] = {}
            raw_field_config = get_entity_field_config(config, fieldname, entity_type, bundle_type)
            field_config = json.loads(raw_field_config)

            field_definitions[fieldname]['entity_type'] = field_config['entity_type']
            field_definitions[fieldname]['required'] = field_config['required']
            field_definitions[fieldname]['label'] = field_config['label']
            raw_vocabularies = [x for x in field_config['dependencies']['config'] if re.match("^taxonomy.vocabulary.", x)]
            if len(raw_vocabularies) > 0:
                vocabularies = [x.replace("taxonomy.vocabulary.", '') for x in raw_vocabularies]
                field_definitions[fieldname]['vocabularies'] = vocabularies
            # Reference 'handler' could be nothing, 'default:taxonomy_term' (or some other entity type), or 'views'.
            if 'handler' in field_config['settings']:
                field_definitions[fieldname]['handler'] = field_config['settings']['handler']
            else:
                field_definitions[fieldname]['handler'] = None
            if 'handler_settings' in field_config['settings']:
                field_definitions[fieldname]['handler_settings'] = field_config['settings']['handler_settings']
            else:
                field_definitions[fieldname]['handler_settings'] = None

            raw_field_storage = get_entity_field_storage(config, fieldname, entity_type)
            field_storage = json.loads(raw_field_storage)
            field_definitions[fieldname]['field_type'] = field_storage['type']
            field_definitions[fieldname]['cardinality'] = field_storage['cardinality']
            if 'max_length' in field_storage['settings']:
                field_definitions[fieldname]['max_length'] = field_storage['settings']['max_length']
            else:
                field_definitions[fieldname]['max_length'] = None
            if 'target_type' in field_storage['settings']:
                field_definitions[fieldname]['target_type'] = field_storage['settings']['target_type']
            else:
                field_definitions[fieldname]['target_type'] = None
            if field_storage['type'] == 'typed_relation' and 'rel_types' in field_config['settings']:
                field_definitions[fieldname]['typed_relations'] = field_config['settings']['rel_types']
            if 'authority_sources' in field_config['settings']:
                field_definitions[fieldname]['authority_sources'] = list(field_config['settings']['authority_sources'].keys())
            else:
                field_definitions[fieldname]['authority_sources'] = None
            if 'allowed_values' in field_storage['settings']:
                field_definitions[fieldname]['allowed_values'] = list(field_storage['settings']['allowed_values'].keys())
            else:
                field_definitions[fieldname]['allowed_values'] = None

        # title's configuration is not returned by Drupal so we construct it here. Note: if you add a new key to
        # 'field_definitions', also add it to title's entry here. Also add it for 'title' in the other entity types, below.
        field_definitions['title'] = {
            'entity_type': 'node',
            'required': True,
            'label': 'Title',
            'field_type': 'string',
            'cardinality': 1,
            'max_length': config['max_node_title_length'],
            'target_type': None,
            'handler': None,
            'handler_settings': None
        }

    if entity_type == 'taxonomy_term':
        fields = get_entity_fields(config, 'taxonomy_term', bundle_type)
        for fieldname in fields:
            field_definitions[fieldname] = {}
            raw_field_config = get_entity_field_config(config, fieldname, entity_type, bundle_type)
            field_config = json.loads(raw_field_config)
            field_definitions[fieldname]['entity_type'] = field_config['entity_type']
            field_definitions[fieldname]['required'] = field_config['required']
            field_definitions[fieldname]['label'] = field_config['label']
            # Reference 'handler' could be nothing, 'default:taxonomy_term' (or some other entity type), or 'views'.
            if 'handler' in field_config['settings']:
                field_definitions[fieldname]['handler'] = field_config['settings']['handler']
            else:
                field_definitions[fieldname]['handler'] = None
            if 'handler_settings' in field_config['settings']:
                field_definitions[fieldname]['handler_settings'] = field_config['settings']['handler_settings']
            else:
                field_definitions[fieldname]['handler_settings'] = None

            raw_field_storage = get_entity_field_storage(config, fieldname, entity_type)
            field_storage = json.loads(raw_field_storage)
            field_definitions[fieldname]['field_type'] = field_storage['type']
            field_definitions[fieldname]['cardinality'] = field_storage['cardinality']
            if 'max_length' in field_storage['settings']:
                field_definitions[fieldname]['max_length'] = field_storage['settings']['max_length']
            else:
                field_definitions[fieldname]['max_length'] = None
            if 'target_type' in field_storage['settings']:
                field_definitions[fieldname]['target_type'] = field_storage['settings']['target_type']
            else:
                field_definitions[fieldname]['target_type'] = None
            if 'authority_sources' in field_config['settings']:
                field_definitions[fieldname]['authority_sources'] = list(field_config['settings']['authority_sources'].keys())
            else:
                field_definitions[fieldname]['authority_sources'] = None
            if 'allowed_values' in field_storage['settings']:
                field_definitions[fieldname]['allowed_values'] = list(field_storage['settings']['allowed_values'].keys())
            else:
                field_definitions[fieldname]['allowed_values'] = None

        field_definitions['term_name'] = {
            'entity_type': 'taxonomy_term',
            'required': True,
            'label': 'Name',
            'field_type': 'string',
            'cardinality': 1,
            'max_length': 255,
            'target_type': None,
            'handler': None,
            'handler_settings': None
        }

    if entity_type == 'media':
        fields = get_entity_fields(config, entity_type, bundle_type)
        for fieldname in fields:
            field_definitions[fieldname] = {}
            raw_field_config = get_entity_field_config(config, fieldname, entity_type, bundle_type)
            field_config = json.loads(raw_field_config)
            field_definitions[fieldname]['media_type'] = bundle_type
            field_definitions[fieldname]['field_type'] = field_config['field_type']
            if 'file_extensions' in field_config['settings']:
                field_definitions[fieldname]['file_extensions'] = field_config['settings']['file_extensions']

            raw_field_storage = get_entity_field_storage(config, fieldname, entity_type)
            field_storage = json.loads(raw_field_storage)
            field_definitions[fieldname]['field_type'] = field_storage['type']
            field_definitions[fieldname]['cardinality'] = field_storage['cardinality']
            if 'max_length' in field_storage['settings']:
                field_definitions[fieldname]['max_length'] = field_storage['settings']['max_length']
            else:
                field_definitions[fieldname]['max_length'] = None
            if 'target_type' in field_storage['settings']:
                field_definitions[fieldname]['target_type'] = field_storage['settings']['target_type']
            else:
                field_definitions[fieldname]['target_type'] = None
            if 'allowed_values' in field_storage['settings']:
                field_definitions[fieldname]['allowed_values'] = list(field_storage['settings']['allowed_values'].keys())
            else:
                field_definitions[fieldname]['allowed_values'] = None

    if entity_type == 'paragraph':
        fields = get_entity_fields(config, entity_type, bundle_type)
        for fieldname in fields:
            # NOTE, WIP on #292. Code below copied from 'node' section above, may need modification.
            field_definitions[fieldname] = {}
            raw_field_config = get_entity_field_config(config, fieldname, entity_type, bundle_type)
            field_config = json.loads(raw_field_config)

            field_definitions[fieldname]['entity_type'] = field_config['entity_type']
            field_definitions[fieldname]['required'] = field_config['required']
            field_definitions[fieldname]['label'] = field_config['label']
            raw_vocabularies = [x for x in field_config['dependencies']['config'] if re.match("^taxonomy.vocabulary.", x)]
            if len(raw_vocabularies) > 0:
                vocabularies = [x.replace("taxonomy.vocabulary.", '') for x in raw_vocabularies]
                field_definitions[fieldname]['vocabularies'] = vocabularies
            # Reference 'handler' could be nothing, 'default:taxonomy_term' (or some other entity type), or 'views'.
            if 'handler' in field_config['settings']:
                field_definitions[fieldname]['handler'] = field_config['settings']['handler']
            else:
                field_definitions[fieldname]['handler'] = None
            if 'handler_settings' in field_config['settings']:
                field_definitions[fieldname]['handler_settings'] = field_config['settings']['handler_settings']
            else:
                field_definitions[fieldname]['handler_settings'] = None

            raw_field_storage = get_entity_field_storage(config, fieldname, entity_type)
            field_storage = json.loads(raw_field_storage)
            field_definitions[fieldname]['field_type'] = field_storage['type']
            field_definitions[fieldname]['cardinality'] = field_storage['cardinality']
            if 'max_length' in field_storage['settings']:
                field_definitions[fieldname]['max_length'] = field_storage['settings']['max_length']
            else:
                field_definitions[fieldname]['max_length'] = None
            if 'target_type' in field_storage['settings']:
                field_definitions[fieldname]['target_type'] = field_storage['settings']['target_type']
            else:
                field_definitions[fieldname]['target_type'] = None
            if field_storage['type'] == 'typed_relation' and 'rel_types' in field_config['settings']:
                field_definitions[fieldname]['typed_relations'] = field_config['settings']['rel_types']
            if 'authority_sources' in field_config['settings']:
                field_definitions[fieldname]['authority_sources'] = list(field_config['settings']['authority_sources'].keys())
            else:
                field_definitions[fieldname]['authority_sources'] = None
            if 'allowed_values' in field_storage['settings']:
                field_definitions[fieldname]['allowed_values'] = list(field_storage['settings']['allowed_values'].keys())
            else:
                field_definitions[fieldname]['allowed_values'] = None

    return field_definitions


def get_entity_fields(config, entity_type, bundle_type):
    """Get all the fields configured on a bundle.
    """
    if ping_content_type(config) == 404:
        message = f"Content type '{config['content_type']}' does not exist on {config['host']}."
        logging.error(message)
        sys.exit('Error: ' + message)
    fields_endpoint = config['host'] + '/entity/entity_form_display/' + entity_type + '.' + bundle_type + '.default?_format=json'
    bundle_type_response = issue_request(config, 'GET', fields_endpoint)
    # If a vocabulary has no custom fields (like the default "Tags" vocab), this query will
    # return a 404 response. So, we need to use an alternative way to check if the vocabulary
    # really doesn't exist.
    if bundle_type_response.status_code == 404 and entity_type == 'taxonomy_term':
        fallback_fields_endpoint = '/entity/taxonomy_vocabulary/' + bundle_type + '?_format=json'
        fallback_bundle_type_response = issue_request(config, 'GET', fallback_fields_endpoint)
        # If this request confirms the vocabulary exists, its OK to make some assumptions
        # about what fields it has.
        if fallback_bundle_type_response.status_code == 200:
            return []

    fields = []
    if bundle_type_response.status_code == 200:
        node_config_raw = json.loads(bundle_type_response.text)
        fieldname_prefix = 'field.field.' + entity_type + '.' + bundle_type + '.'
        fieldnames = [
            field_dependency.replace(
                fieldname_prefix,
                '') for field_dependency in node_config_raw['dependencies']['config']]
        for fieldname in node_config_raw['dependencies']['config']:
            fieldname_prefix = 'field.field.' + entity_type + '.' + bundle_type + '.'
            if re.match(fieldname_prefix, fieldname):
                fieldname = fieldname.replace(fieldname_prefix, '')
                fields.append(fieldname)
    else:
        message = 'Workbench cannot retrieve field definitions from Drupal. Please confirm that the Field, Field Storage, and Entity Form Display REST resources are enabled.'
        logging.error(message)
        sys.exit('Error: ' + message)

    return fields


def get_required_bundle_fields(config, entity_type, bundle_type):
    """Gets a list of required fields for the given bundle type.
    """
    """Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        entity_type : string
            One of 'node', 'media', or 'taxonomy_term'.
        bundle_type : string
            The (node) content type, the vocabulary name, or the media type ('image',
            'document', 'audio', 'video', 'file', etc.).

        Returns
        -------
        list
            A list of Drupal field names that are configured as required for this bundle.
    """
    field_definitions = get_field_definitions(config, entity_type, bundle_type)
    required_drupal_fields = list()
    for drupal_fieldname in field_definitions:
        if 'entity_type' in field_definitions[drupal_fieldname] and field_definitions[drupal_fieldname]['entity_type'] == entity_type:
            if 'required' in field_definitions[drupal_fieldname] and field_definitions[drupal_fieldname]['required'] is True:
                required_drupal_fields.append(drupal_fieldname)
    return required_drupal_fields


def get_entity_field_config(config, fieldname, entity_type, bundle_type):
    """Get a specific fields's configuration.

       Example query for taxo terms: /entity/field_config/taxonomy_term.islandora_media_use.field_external_uri?_format=json
    """
    field_config_endpoint = config['host'] + '/entity/field_config/' + entity_type + '.' + bundle_type + '.' + fieldname + '?_format=json'
    field_config_response = issue_request(config, 'GET', field_config_endpoint)
    if field_config_response.status_code == 200:
        return field_config_response.text
    else:
        message = 'Workbench cannot retrieve field definitions from Drupal. Please confirm that the Field, Field Storage, and Entity Form Display REST resources are enabled.'
        logging.error(message)
        sys.exit('Error: ' + message)


def get_entity_field_storage(config, fieldname, entity_type):
    """Get a specific fields's storage configuration.

       Example query for taxo terms: /entity/field_storage_config/taxonomy_term.field_external_uri?_format=json
    """
    field_storage_endpoint = config['host'] + '/entity/field_storage_config/' + entity_type + '.' + fieldname + '?_format=json'
    field_storage_response = issue_request(config, 'GET', field_storage_endpoint)
    if field_storage_response.status_code == 200:
        return field_storage_response.text
    else:
        message = 'Workbench cannot retrieve field definitions from Drupal. Please confirm that the Field, Field Storage, and Entity Form Display REST resources are enabled.'
        logging.error(message)
        sys.exit('Error: ' + message)


def check_input(config, args):
    """Validate the config file and input data.
    """
    logging.info(
        'Starting configuration check for "%s" task using config file %s.',
        config['task'],
        args.config)

    ping_islandora(config, print_message=False)
    check_integration_module_version(config)

    rows_with_missing_files = list()

    base_fields = ['title', 'status', 'promote', 'sticky', 'uid', 'created']
    # Any new reserved columns introduced into the CSV need to be removed here. 'langcode' is a standard Drupal field
    # but it doesn't show up in any field configs.
    reserved_fields = ['file', 'media_use_tid', 'checksum', 'node_id', 'url_alias', 'image_alt_text', 'parent_id', 'langcode']
    entity_fields = get_entity_fields(config, 'node', config['content_type'])
    if config['id_field'] not in entity_fields:
        reserved_fields.append(config['id_field'])

    # Check the config file.
    tasks = [
        'create',
        'update',
        'delete',
        'add_media',
        'delete_media',
        'delete_media_by_node',
        'create_from_files',
        'create_terms',
        'export_csv',
        'get_data_from_view'
    ]
    joiner = ', '
    if config['task'] not in tasks:
        message = '"task" in your configuration file must be one of "create", "update", "delete", ' + \
            '"add_media", "delete_media", "delete_media_by_node", "create_from_files", "create_terms", "export_csv", or "get_data_from_view".'
        logging.error(message)
        sys.exit('Error: ' + message)

    config_keys = list(config.keys())
    config_keys.remove('check')

    # Check for presence of required config keys, which varies by task.
    if config['task'] == 'create':
        if config['nodes_only'] is True:
            message = '"nodes_only" option in effect. Media files will not be checked/validated.'
            print(message)
            logging.info(message)

        create_required_options = [
            'task',
            'host',
            'username',
            'password']
        for create_required_option in create_required_options:
            if create_required_option not in config_keys:
                message = 'Please check your config file for required values: ' + joiner.join(create_required_options) + '.'
                logging.error(message)
                sys.exit('Error: ' + message)
    if config['task'] == 'update':
        update_required_options = [
            'task',
            'host',
            'username',
            'password']
        for update_required_option in update_required_options:
            if update_required_option not in config_keys:
                message = 'Please check your config file for required values: ' + joiner.join(update_required_options) + '.'
                logging.error(message)
                sys.exit('Error: ' + message)
        update_mode_options = ['replace', 'append', 'delete']
        if config['update_mode'] not in update_mode_options:
            message = 'Your "update_mode" config option must be one of the following: ' + joiner.join(update_mode_options) + '.'
            logging.error(message)
            sys.exit('Error: ' + message)

    if config['task'] == 'delete':
        delete_required_options = [
            'task',
            'host',
            'username',
            'password']
        for delete_required_option in delete_required_options:
            if delete_required_option not in config_keys:
                message = 'Please check your config file for required values: ' + joiner.join(delete_required_options) + '.'
                logging.error(message)
                sys.exit('Error: ' + message)
    if config['task'] == 'add_media':
        add_media_required_options = [
            'task',
            'host',
            'username',
            'password']
        for add_media_required_option in add_media_required_options:
            if add_media_required_option not in config_keys:
                message = 'Please check your config file for required values: ' + joiner.join(add_media_required_options) + '.'
                logging.error(message)
                sys.exit('Error: ' + message)
    if config['task'] == 'delete_media':
        delete_media_required_options = [
            'task',
            'host',
            'username',
            'password']
        for delete_media_required_option in delete_media_required_options:
            if delete_media_required_option not in config_keys:
                message = 'Please check your config file for required values: ' + joiner.join(delete_media_required_options) + '.'
                logging.error(message)
                sys.exit('Error: ' + message)
    if config['task'] == 'delete_media_by_node':
        delete_media_by_node_required_options = [
            'task',
            'host',
            'username',
            'password']
        for delete_media_by_node_required_option in delete_media_by_node_required_options:
            if delete_media_by_node_required_option not in config_keys:
                message = 'Please check your config file for required values: ' + joiner.join(delete_media_by_node_required_options) + '.'
                logging.error(message)
                sys.exit('Error: ' + message)
    if config['task'] == 'export_csv':
        export_csv_required_options = [
            'task',
            'host',
            'username',
            'password']
        for export_csv_required_option in export_csv_required_options:
            if export_csv_required_option not in config_keys:
                message = 'Please check your config file for required values: ' + joiner.join(export_csv_required_options) + '.'
                logging.error(message)
                sys.exit('Error: ' + message)
        if config['export_csv_term_mode'] == 'name':
            message = 'The "export_csv_term_mode" configuration option is set to "name", which will slow down the export.'
            print(message)
    if config['task'] == 'create_terms':
        create_terms_required_options = [
            'task',
            'host',
            'username',
            'password',
            'vocab_id']
        for create_terms_required_option in create_terms_required_options:
            if create_terms_required_option not in config_keys:
                message = 'Please check your config file for required values: ' + joiner.join(create_terms_required_options) + '.'
                logging.error(message)
                sys.exit('Error: ' + message)
    if config['task'] == 'get_data_from_view':
        get_data_from_view_required_options = [
            'task',
            'host',
            'username',
            'password',
            'view_path']
        for get_data_from_view_required_option in get_data_from_view_required_options:
            if get_data_from_view_required_option not in config_keys:
                message = 'Please check your config file for required values: ' + joiner.join(get_data_from_view_required_options) + '.'
                logging.error(message)
                sys.exit('Error: ' + message)

    message = 'OK, configuration file has all required values (did not check for optional values).'
    print(message)
    logging.info(message)

    # Perform checks on get_data_from_view tasks. Since this task doesn't use input_dir, input_csv, etc.,
    # we exit immediately after doing these checks.
    if config['task'] == 'get_data_from_view':
        # First, ping the View.
        view_parameters = '&'.join(config['view_parameters']) if 'view_parameters' in config else ''
        view_url = config['host'] + '/' + config['view_path'].lstrip('/') + '?page=0&' + view_parameters

        view_path_status_code = ping_view_endpoint(config, view_url)
        if view_path_status_code != 200:
            message = f"Cannot access View at {view_url}."
            logging.error(message)
            sys.exit("Error: " + message)
        else:
            message = f'View REST export at "{view_url}" is accessible.'
            logging.info(message)
            print("OK, " + message)

        if config['export_file_directory'] is not None:
            if not os.path.exists(config['export_file_directory']):
                try:
                    os.mkdir(config['export_file_directory'])
                    os.rmdir(config['export_file_directory'])
                except Exception as e:
                    message = 'Path in configuration option "export_file_directory" ("' + config['export_file_directory'] + '") is not writable.'
                    logging.error(message + ' ' + str(e))
                    sys.exit('Error: ' + message + ' See log for more detail.')

        if config['export_file_media_use_term_id'] is False:
            message = f'Unknown value for configuration setting "export_file_media_use_term_id": {config["export_file_media_use_term_id"]}.'
            logging.error(message)
            sys.exit('Error: ' + message)

        # Check to make sure the output path for the CSV file is writable.
        if config['export_csv_file_path'] is not None:
            csv_file_path = config['export_csv_file_path']
        else:
            csv_file_path = os.path.join(config['input_dir'], os.path.basename(args.config).split('.')[0] + '.csv_file_with_data_from_view')
        csv_file_path_file = open(csv_file_path, "a")
        if csv_file_path_file.writable() is False:
            message = f'Path to CSV file "{csv_file_path}" is not writable.'
            logging.error(message)
            csv_file_path_file.close()
            sys.exit("Error: " + message)
        else:
            message = f'CSV output file location at {csv_file_path} is writable.'
            logging.info(message)
            print("OK, " + message)
            csv_file_path_file.close()

        if os.path.exists(csv_file_path):
            os.remove(csv_file_path)

        # If nothing has failed by now, exit with a positive, upbeat message.
        print("Configuration and input data appear to be valid.")
        logging.info('Configuration checked for "%s" task using config file "%s", no problems found.', config['task'], args.config)
        sys.exit()

    validate_input_dir(config)

    check_csv_file_exists(config, 'node_fields')

    # Check column headers in CSV file.
    csv_data = get_csv_data(config)
    csv_column_headers = csv_data.fieldnames

    # Check whether each row contains the same number of columns as there are headers.
    row_count = 0
    for row_count, row in enumerate(csv_data, start=1):
        extra_headers = False
        field_count = 0
        for field in row:
            # 'stringtopopulateextrafields' is added by get_csv_data() if there are extra headers.
            if row[field] == 'stringtopopulateextrafields':
                extra_headers = True
            else:
                field_count += 1
        if extra_headers is True:
            message = "Row " + str(row_count) + " (ID " + row[config['id_field']] + ") of the CSV file has fewer columns " +  \
                "than there are headers (" + str(len(csv_column_headers)) + ")."
            logging.error(message)
            sys.exit('Error: ' + message)
        # Note: this message is also generated in get_csv_data() since CSV Writer thows an exception if the row has
        # form fields than headers.
        if len(csv_column_headers) < field_count:
            message = "Row " + str(row_count) + " (ID " + row[config['id_field']] + ") of the CSV file has more columns (" +  \
                str(field_count) + ") than there are headers (" + str(len(csv_column_headers)) + ")."
            logging.error(message)
            sys.exit('Error: ' + message)
    if row_count == 0:
        message = "Input CSV file " + config['input_csv'] + " has 0 rows."
        logging.error(message)
        sys.exit('Error: ' + message)
    else:
        message = "OK, all " + str(row_count) + " rows in the CSV file have the same number of columns as there are headers (" + str(len(csv_column_headers)) + ")."
        print(message)
        logging.info(message)

    # Task-specific CSV checks.
    langcode_was_present = False
    if config['task'] == 'create':
        field_definitions = get_field_definitions(config, 'node')
        if config['id_field'] not in csv_column_headers:
            message = 'For "create" tasks, your CSV file must have a column containing a unique identifier.'
            logging.error(message)
            sys.exit('Error: ' + message)
        if config['nodes_only'] is False and 'file' not in csv_column_headers and config['paged_content_from_directories'] is False:
            message = 'For "create" tasks, your CSV file must contain a "file" column.'
            logging.error(message)
            sys.exit('Error: ' + message)
        if 'title' not in csv_column_headers:
            message = 'For "create" tasks, your CSV file must contain a "title" column.'
            logging.error(message)
            sys.exit('Error: ' + message)
        if 'output_csv' in config.keys():
            if os.path.exists(config['output_csv']):
                message = 'Output CSV already exists at ' + config['output_csv'] + ', records will be appended to it.'
                print(message)
                logging.info(message)
        if 'url_alias' in csv_column_headers:
            validate_url_aliases_csv_data = get_csv_data(config)
            validate_url_aliases(config, validate_url_aliases_csv_data)

        # Specific to creating aggregated content such as collections, compound objects and paged content. Currently, if 'parent_id' is present
        # in the CSV file 'field_member_of' is mandatory.
        if 'parent_id' in csv_column_headers:
            if ('field_weight' not in csv_column_headers):
                message = 'If ingesting paged content, or compound objects where order is required a "field_weight" column is required.'
                logging.info(message)
            if ('field_member_of' not in csv_column_headers):
                message = 'If your CSV file contains a "parent_id" column, it must also contain an empty "field_member_of" column.'
                logging.error(message)
                sys.exit('Error: ' + message)
        drupal_fieldnames = []
        for drupal_fieldname in field_definitions:
            drupal_fieldnames.append(drupal_fieldname)

        if len(drupal_fieldnames) == 0:
            message = 'Workbench cannot retrieve field definitions from Drupal. Please confirm that the Field, Field Storage, and Entity Form Display REST resources are enabled.'
            logging.error(message)
            sys.exit('Error: ' + message)

        if config['list_missing_drupal_fields'] is True:
            missing_drupal_fields = []
            for csv_column_header in csv_column_headers:
                if csv_column_header not in drupal_fieldnames and csv_column_header not in base_fields:
                    if csv_column_header not in reserved_fields and csv_column_header not in get_additional_files_config(config).keys():
                        if csv_column_header != config['id_field']:
                            missing_drupal_fields.append(csv_column_header)
            if len(missing_drupal_fields) > 0:
                missing_drupal_fields_message = ', '.join(missing_drupal_fields)
                logging.error("The following header(s) require a matching Drupal field name: %s.", missing_drupal_fields_message)
                sys.exit('Error: The following header(s) require a matching Drupal field name: ' + missing_drupal_fields_message + '.')

        # We .remove() CSV column headers for this check because they are not Drupal field names (including 'langcode').
        for reserved_field in reserved_fields:
            if reserved_field in csv_column_headers:
                csv_column_headers.remove(reserved_field)

        # langcode is a standard Drupal field but it doesn't show up in any field configs.
        if 'langcode' in csv_column_headers:
            csv_column_headers.remove('langcode')
            # Set this so we can validate langcode below.
            langcode_was_present = True

        # We .remove() CSV column headers that use the 'media:video:field_foo' media track convention.
        media_track_headers = list()
        for column_header in csv_column_headers:
            if column_header.startswith('media:'):
                media_track_headers.append(column_header)
        for media_track_header in media_track_headers:
            if media_track_header in csv_column_headers:
                csv_column_headers.remove(media_track_header)

        # We also validate the structure of the media track column headers.
        for media_track_header in media_track_headers:
            media_track_header_parts = media_track_header.split(':')
            if media_track_header_parts[0] != 'media' and len(media_track_header_parts) != 3:
                message = f'"{media_track_header}" is not a valide media track CSV header.'
                logging.error(message)
                sys.exit('Error: ' + message)

        # Check for the View that is necessary for entity reference fields configured
        # as "Views: Filter by an entity reference View" (issue 452).
        for csv_column_header in csv_column_headers:
            if csv_column_header in field_definitions and field_definitions[csv_column_header]['handler'] == 'views':
                if config['require_entity_reference_views'] is True:
                    entity_reference_view_exists = ping_entity_reference_view_endpoint(config, csv_column_header, field_definitions[csv_column_header]['handler_settings'])
                    if entity_reference_view_exists is False:
                        console_message = 'Workbench cannot access the View "' + field_definitions[csv_column_header]['handler_settings']['view']['view_name'] + \
                            '" required to validate values for field "' + csv_column_header + '". See log for more detail.'
                        log_message = 'Workbench cannot access the path defined by the REST Export display "' + \
                            field_definitions[csv_column_header]['handler_settings']['view']['display_name'] + \
                            '" in the View "' + field_definitions[csv_column_header]['handler_settings']['view']['view_name'] + \
                            '" required to validate values for field "' + csv_column_header + '". Please check your Drupal Views configuration.' + \
                            ' See the "Entity Reference Views fields" section of ' + \
                            'https://mjordan.github.io/islandora_workbench_docs/fields/#csv-fields-that-contain-drupal-field-data for more info.'
                        logging.error(log_message)
                        sys.exit('Error: ' + console_message)
                else:
                    message = f'"require_entity_reference_views" is set to "false" in your configuration file. Workbench will not validate values in your CSV file\'s "{csv_column_header}" column.'
                    print(message)
                    logging.warning(message +
                                    ' See the "Entity Reference Views fields" section of ' +
                                    'https://mjordan.github.io/islandora_workbench_docs/fields/#csv-fields-that-contain-drupal-field-data for more info.')

            if len(get_additional_files_config(config)) > 0:
                if csv_column_header not in drupal_fieldnames and csv_column_header not in base_fields and csv_column_header not in get_additional_files_config(config).keys():
                    if csv_column_header in config['ignore_csv_columns']:
                        continue
                    additional_files_entries = get_additional_files_config(config)
                    if csv_column_header in additional_files_entries.keys():
                        continue
                    logging.error('CSV column header %s does not match any Drupal, reserved, or "additional_files" field names.', csv_column_header)
                    sys.exit('Error: CSV column header "' + csv_column_header + '" does not match any Drupal, reserved, or "additional_files" field names.')
            else:
                if csv_column_header not in drupal_fieldnames and csv_column_header not in base_fields and csv_column_header:
                    if csv_column_header in config['ignore_csv_columns']:
                        continue
                    logging.error("CSV column header %s does not match any Drupal or reserved field names.", csv_column_header)
                    sys.exit('Error: CSV column header "' + csv_column_header + '" does not match any Drupal or reserved field names.')
        message = 'OK, CSV column headers match Drupal field names.'
        print(message)
        logging.info(message)

    # Check that Drupal fields that are required are in the CSV file (create task only).
    if config['task'] == 'create':
        required_drupal_fields_node = get_required_bundle_fields(config, 'node', config['content_type'])
        '''
        required_drupal_fields_node = []
        for drupal_fieldname in field_definitions:
            # In the create task, we only check for required fields that apply to nodes.
            if 'entity_type' in field_definitions[drupal_fieldname] and field_definitions[drupal_fieldname]['entity_type'] == 'node':
                if 'required' in field_definitions[drupal_fieldname] and field_definitions[drupal_fieldname]['required'] is True:
                    required_drupal_fields_node.append(drupal_fieldname)
        '''
        for required_drupal_field in required_drupal_fields_node:
            if required_drupal_field not in csv_column_headers:
                logging.error("Required Drupal field %s is not present in the CSV file.", required_drupal_field)
                sys.exit('Error: Field "' + required_drupal_field + '" required for content type "' + config['content_type'] + '" is not present in the CSV file.')
        message = 'OK, required Drupal fields are present in the CSV file.'
        print(message)
        logging.info(message)

        # Validate dates in 'created' field, if present.
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        if 'created' in csv_column_headers:
            validate_node_created_csv_data = get_csv_data(config)
            validate_node_created_date(validate_node_created_csv_data)
        # Validate user IDs in 'uid' field, if present.
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        if 'uid' in csv_column_headers:
            validate_node_uid_csv_data = get_csv_data(config)
            validate_node_uid(config, validate_node_uid_csv_data)

    if config['task'] == 'update':
        if 'node_id' not in csv_column_headers:
            message = 'For "update" tasks, your CSV file must contain a "node_id" column.'
            logging.error(message)
            sys.exit('Error: ' + message)
        if 'url_alias' in csv_column_headers:
            # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
            validate_url_aliases_csv_data = get_csv_data(config)
            validate_url_aliases(config, validate_url_aliases_csv_data)
        field_definitions = get_field_definitions(config, 'node')
        drupal_fieldnames = []
        for drupal_fieldname in field_definitions:
            drupal_fieldnames.append(drupal_fieldname)
        if 'title' in csv_column_headers:
            csv_column_headers.remove('title')
        if 'url_alias' in csv_column_headers:
            csv_column_headers.remove('url_alias')
        if 'image_alt_text' in csv_column_headers:
            csv_column_headers.remove('image_alt_text')
        if 'media_use_tid' in csv_column_headers:
            csv_column_headers.remove('media_use_tid')
        if 'file' in csv_column_headers:
            message = 'Error: CSV column header "file" is not allowed in update tasks.'
            logging.error(message)
            sys.exit(message)
        if 'node_id' in csv_column_headers:
            csv_column_headers.remove('node_id')

        # langcode is a standard Drupal field but it doesn't show up in any field configs.
        if 'langcode' in csv_column_headers:
            csv_column_headers.remove('langcode')
            # Set this so we can validate langcode below.
            langcode_was_present = True

        for csv_column_header in csv_column_headers:
            if csv_column_header not in drupal_fieldnames and csv_column_header not in base_fields:
                if csv_column_header in config['ignore_csv_columns']:
                    continue
                logging.error('CSV column header %s does not match any Drupal field names in the %s content type.', csv_column_header, config['content_type'])
                sys.exit('Error: CSV column header "' + csv_column_header + '" does not match any Drupal field names in the ' + config['content_type'] + ' content type.')
        message = 'OK, CSV column headers match Drupal field names.'
        print(message)
        logging.info(message)

    if config['task'] == 'add_media' or config['task'] == 'create' and config['nodes_only'] is False:
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        validate_media_use_tid(config)
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        validate_media_use_tid_values_csv_data = get_csv_data(config)
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        validate_media_use_tids_in_csv(config, validate_media_use_tid_values_csv_data)

        if config['fixity_algorithm'] is not None:
            allowed_algorithms = ['md5', 'sha1', 'sha256']
            if config['fixity_algorithm'] not in allowed_algorithms:
                message = "Configured fixity algorithm '" + config['fixity_algorithm'] + "' must be one of 'md5', 'sha1', or 'sha256'."
                logging.error(message)
                sys.exit('Error: ' + message)

        if config['validate_fixity_during_check'] is True and config['fixity_algorithm'] is not None:
            print("Performing local checksum validation. This might take some time.")
            if 'file' in csv_column_headers and 'checksum' in csv_column_headers:
                # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
                validate_checksums_csv_data = get_csv_data(config)
                if config['task'] == 'add_media':
                    row_id = 'node_id'
                else:
                    row_id = config['id_field']
                checksum_validation_all_ok = True
                for checksum_validation_row_count, checksum_validation_row in enumerate(validate_checksums_csv_data, start=1):
                    file_path = checksum_validation_row['file']
                    hash_from_local = get_file_hash_from_local(config, file_path, config['fixity_algorithm'])
                    if 'checksum' in checksum_validation_row:
                        if hash_from_local == checksum_validation_row['checksum'].strip():
                            logging.info('Local %s checksum and value in the CSV "checksum" field for file "%s" (%s) match.', config['fixity_algorithm'], file_path, hash_from_local)
                        else:
                            checksum_validation_all_ok = False
                            logging.warning('Local %s checksum and value in the CSV "checksum" field for file "%s" (named in CSV row "%s") do not match (local: %s, CSV: %s).',
                                            config['fixity_algorithm'], file_path, checksum_validation_row[row_id], hash_from_local, checksum_validation_row['checksum'])

                if checksum_validation_all_ok is True:
                    checksum_validation_message = "OK, checksum validation during complete. All checks pass."
                    logging.info(checksum_validation_message)
                    print(checksum_validation_message + " See the log for more detail.")
                else:
                    checksum_validation_message = "Not all checksum validation passed."
                    logging.warning(checksum_validation_message)
                    print("Warning: " + checksum_validation_message + " See the log for more detail.")

    if config['task'] == 'create_terms':
        # Check that all required fields are present in the CSV.
        field_definitions = get_field_definitions(config, 'taxonomy_term', config['vocab_id'])

        # Check here that all required fields are present in the CSV.
        required_fields = get_required_bundle_fields(config, 'taxonomy_term', config['vocab_id'])
        required_fields.insert(0, 'term_name')
        required_fields_check_csv_data = get_csv_data(config)
        missing_fields = []
        for required_field in required_fields:
            if required_field not in required_fields_check_csv_data.fieldnames:
                missing_fields.append(required_field)
        if len(missing_fields) > 0:
            message = 'Required columns missing from input CSV file: ' + joiner.join(missing_fields) + '.'
            logging.error(message)
            sys.exit('Error: ' + message)

        # Validate length of 'term_name'.
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        validate_term_name_csv_data = get_csv_data(config)
        for count, row in enumerate(validate_term_name_csv_data, start=1):
            if 'term_name' in row and len(row['term_name']) > 255:
                message = "The 'term_name' column in row for term '" + row['term_name'] + "' of your CSV file exceeds Drupal's maximum length of 255 characters."
                logging.error(message)
                sys.exit('Error: ' + message)

        validate_geolocation_values_csv_data = get_csv_data(config)
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        validate_geolocation_fields(config, field_definitions, validate_geolocation_values_csv_data)

        validate_link_values_csv_data = get_csv_data(config)
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        validate_link_fields(config, field_definitions, validate_link_values_csv_data)

        validate_authority_link_values_csv_data = get_csv_data(config)
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        validate_authority_link_fields(config, field_definitions, validate_authority_link_values_csv_data)

        validate_edtf_values_csv_data = get_csv_data(config)
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        validate_edtf_fields(config, field_definitions, validate_edtf_values_csv_data)

        validate_csv_field_cardinality_csv_data = get_csv_data(config)
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        validate_csv_field_cardinality(config, field_definitions, validate_csv_field_cardinality_csv_data)

        validate_csv_field_length_csv_data = get_csv_data(config)
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        validate_csv_field_length(config, field_definitions, validate_csv_field_length_csv_data)

        validate_taxonomy_field_csv_data = get_csv_data(config)
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        warn_user_about_taxo_terms = validate_taxonomy_field_values(config, field_definitions, validate_taxonomy_field_csv_data)
        if warn_user_about_taxo_terms is True:
            print('Warning: Issues detected with validating taxonomy field values in the CSV file. See the log for more detail.')

        validate_typed_relation_csv_data = get_csv_data(config)
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        warn_user_about_typed_relation_terms = validate_typed_relation_field_values(config, field_definitions, validate_typed_relation_csv_data)
        if warn_user_about_typed_relation_terms is True:
            print('Warning: Issues detected with validating typed relation field values in the CSV file. See the log for more detail.')

    if config['task'] == 'update' or config['task'] == 'create':
        field_definitions = get_field_definitions(config, 'node')
        validate_geolocation_values_csv_data = get_csv_data(config)
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        validate_geolocation_fields(config, field_definitions, validate_geolocation_values_csv_data)

        validate_link_values_csv_data = get_csv_data(config)
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        validate_link_fields(config, field_definitions, validate_link_values_csv_data)

        validate_authority_link_values_csv_data = get_csv_data(config)
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        validate_authority_link_fields(config, field_definitions, validate_authority_link_values_csv_data)

        validate_edtf_values_csv_data = get_csv_data(config)
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        validate_edtf_fields(config, field_definitions, validate_edtf_values_csv_data)

        validate_csv_field_cardinality_csv_data = get_csv_data(config)
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        validate_csv_field_cardinality(config, field_definitions, validate_csv_field_cardinality_csv_data)

        validate_csv_field_length_csv_data = get_csv_data(config)
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        validate_csv_field_length(config, field_definitions, validate_csv_field_length_csv_data)

        validate_text_list_fields_data = get_csv_data(config)
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        validate_text_list_fields(config, field_definitions, validate_text_list_fields_data)

        validate_taxonomy_field_csv_data = get_csv_data(config)
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        warn_user_about_taxo_terms = validate_taxonomy_field_values(config, field_definitions, validate_taxonomy_field_csv_data)
        if warn_user_about_taxo_terms is True:
            print('Warning: Issues detected with validating taxonomy field values in the CSV file. See the log for more detail.')

        validate_typed_relation_csv_data = get_csv_data(config)
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        warn_user_about_typed_relation_terms = validate_typed_relation_field_values(config, field_definitions, validate_typed_relation_csv_data)
        if warn_user_about_typed_relation_terms is True:
            print('Warning: Issues detected with validating typed relation field values in the CSV file. See the log for more detail.')

        validate_media_track_csv_data = get_csv_data(config)
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        validate_media_track_fields(config, validate_media_track_csv_data)

        # Validate existence of nodes specified in 'field_member_of'. This could be generalized out to validate node IDs in other fields.
        # See https://github.com/mjordan/islandora_workbench/issues/90.
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        if config['validate_parent_node_exists'] is True:
            validate_field_member_of_csv_data = get_csv_data(config)
            for count, row in enumerate(validate_field_member_of_csv_data, start=1):
                if 'field_member_of' in csv_column_headers:
                    parent_nids = row['field_member_of'].split(config['subdelimiter'])
                    for parent_nid in parent_nids:
                        if len(parent_nid) > 0:
                            parent_node_exists = ping_node(config, parent_nid)
                            if parent_node_exists is False:
                                message = "The 'field_member_of' field in row with ID '" + row[config['id_field']] + \
                                    "' of your CSV file contains a node ID (" + parent_nid + ") that " + \
                                    "doesn't exist or is not accessible. See the workbench log for more information."
                                logging.error(message)
                                sys.exit('Error: ' + message)
        else:
            message = '"validate_parent_node_exists" is set to false. Node IDs in "field_member_of" that do not exist or are not accessible ' + \
                'will result in 422 errors in "create" and "update" tasks.'
            logging.warning(message)

        # Validate 'langcode' values if that field exists in the CSV.
        # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
        if langcode_was_present:
            validate_langcode_csv_data = get_csv_data(config)
            for count, row in enumerate(validate_langcode_csv_data, start=1):
                langcode_valid = validate_language_code(row['langcode'])
                if not langcode_valid:
                    message = "Row with ID " + row[config['id_field']] + " of your CSV file contains an invalid Drupal language code (" + row['langcode'] + ") in its 'langcode' column."
                    logging.error(message)
                    sys.exit('Error: ' + message)

    if config['task'] == 'delete':
        if 'node_id' not in csv_column_headers:
            message = 'For "delete" tasks, your CSV file must contain a "node_id" column.'
            logging.error(message)
            sys.exit('Error: ' + message)
    if config['task'] == 'add_media':
        if 'node_id' not in csv_column_headers:
            message = 'For "add_media" tasks, your CSV file must contain a "node_id" column.'
            logging.error(message)
            sys.exit('Error: ' + message)
        if 'file' not in csv_column_headers:
            message = 'For "add_media" tasks, your CSV file must contain a "file" column.'
            logging.error(message)
            sys.exit('Error: ' + message)
    if config['task'] == 'delete_media':
        if 'media_id' not in csv_column_headers:
            message = 'For "delete_media" tasks, your CSV file must contain a "media_id" column.'
            logging.error(message)
            sys.exit('Error: ' + message)
    if config['task'] == 'delete_media_by_node':
        if 'node_id' not in csv_column_headers:
            message = 'For "delete_media_by_node" tasks, your CSV file must contain a "node_id" column.'
            logging.error(message)
            sys.exit('Error: ' + message)

    # Check for existence of files listed in the 'file' column.
    if (config['task'] == 'create' or config['task'] == 'add_media') and config['nodes_only'] is False and config['paged_content_from_directories'] is False:
        # Temporary fix for https://github.com/mjordan/islandora_workbench/issues/478.
        if config['task'] == 'add_media':
            config['id_field'] = 'node_id'
        file_check_csv_data = get_csv_data(config)
        for count, file_check_row in enumerate(file_check_csv_data, start=1):
            file_check_row['file'] = file_check_row['file'].strip()
            # Check for empty 'file' values.
            if len(file_check_row['file']) == 0:
                message = 'CSV row with ID ' + file_check_row[config['id_field']] + ' contains an empty "file" value.'
                if config['strict_check'] is True and config['allow_missing_files'] is False:
                    logging.warning(message)
                    sys.exit('Error: ' + message)
                else:
                    if file_check_row[config['id_field']] not in rows_with_missing_files:
                        rows_with_missing_files.append(file_check_row[config['id_field']])
                        logging.warning(message)
            # Check for URLs.
            elif file_check_row['file'].startswith('http'):
                http_response_code = ping_remote_file(config, file_check_row['file'])
                if http_response_code != 200 or ping_remote_file(config, file_check_row['file']) is False:
                    message = 'Remote file "' + file_check_row['file'] + '" identified in CSV "file" column for record with ID "' \
                        + file_check_row[config['id_field']] + '" not found or not accessible (HTTP response code ' + str(http_response_code) + ').'
                    if config['strict_check'] is True and config['allow_missing_files'] is False:
                        logging.error(message)
                        sys.exit('Error: ' + message)
                    else:
                        if file_check_row[config['id_field']] not in rows_with_missing_files:
                            rows_with_missing_files.append(file_check_row[config['id_field']])
                            logging.error(message)
            # Check for files that cannot be found.
            else:
                if os.path.isabs(file_check_row['file']):
                    file_path = file_check_row['file']
                else:
                    file_path = os.path.join(config['input_dir'], file_check_row['file'])
                if not os.path.exists(file_path) or not os.path.isfile(file_path):
                    message = 'File "' + file_path + '" identified in CSV "file" column for record with ID field value "' \
                        + file_check_row[config['id_field']] + '" not found.'
                    if config['strict_check'] is True:
                        logging.error(message)
                        sys.exit('Error: ' + message)
                    else:
                        if file_check_row[config['id_field']] not in rows_with_missing_files:
                            rows_with_missing_files.append(file_check_row[config['id_field']])
                            logging.error(message)

        # @todo for issue 268: All accumulator variables like 'rows_with_missing_files' should be checked at end of
        # check_input() (to work with strict_check: false) in addition to at place of check (to work wit strict_check: true).
        if len(rows_with_missing_files) > 0:
            if config['allow_missing_files'] is True:
                message = 'OK, missing or empty CSV "file" column values detected, but the "allow_missing_files" configuration option is enabled.'
                print(message + " See the log for more information.")
                logging.info(message + " See log entries above for more information.")
        else:
            message = 'OK, files named in the CSV "file" column are all present.'
            print(message)
            logging.info(message)

        # Verify that all media bundles/types exist.
        if config['nodes_only'] is False:
            media_type_check_csv_data = get_csv_data(config)
            for count, file_check_row in enumerate(media_type_check_csv_data, start=1):
                filename_fields_to_check = ['file']
                if 'additional_files' in config and len(config['additional_files']) > 0:
                    additional_files_entries = get_additional_files_config(config)
                    filename_fields_to_check.extend(additional_files_entries.keys())
                for filename_field in filename_fields_to_check:
                    if len(file_check_row[filename_field]) != 0:
                        media_type = set_media_type(config, file_check_row[filename_field], filename_field, file_check_row)
                        media_bundle_response_code = ping_media_bundle(config, media_type)
                        if media_bundle_response_code == 404:
                            message = 'File "' + file_check_row[filename_field] + '" identified in CSV row ' + file_check_row[config['id_field']] + \
                                ' will create a media of type (' + media_type + '), but that media type is not configured in the destination Drupal.'
                            logging.error(message)
                            sys.exit('Error: ' + message)

                        # Check that each file's extension is allowed for the current media type. 'file' is the only
                        # CSV field to check here. Files added using the 'additional_files' setting are checked below.
                        media_type_file_field = config['media_type_file_fields'][media_type]
                        extension = os.path.splitext(file_check_row['file'])[1]
                        extension = extension.lstrip('.').lower()
                        media_type_file_field = config['media_type_file_fields'][media_type]
                        registered_extensions = get_registered_media_extensions(config, media_type, media_type_file_field)
                        if extension not in registered_extensions[media_type_file_field]:
                            message = 'File "' + file_check_row[filename_field] + '" in CSV row ' + file_check_row[config['id_field']] + \
                                ' does not have an extension allowed in the "' + media_type_file_field + '" field of the (' + media_type + ') media type.'
                            logging.error(message)
                            sys.exit('Error: ' + message)

    # Check existence of fields identified in 'additional_files' config setting, and the files named in those fields.
    # Also check for the acommpanying Media Use tid.
    if (config['task'] == 'create' or config['task'] == 'add_media') and config['paged_content_from_directories'] is False:
        if 'additional_files' in config and len(config['additional_files']) > 0:
            additional_files_entries = get_additional_files_config(config)
            additional_files_check_csv_data = get_csv_data(config)
            additional_files_fields = additional_files_entries.keys()
            additional_files_fields_csv_headers = additional_files_check_csv_data.fieldnames
            if config['nodes_only'] is False:
                for additional_file_field in additional_files_fields:
                    if additional_file_field not in additional_files_fields_csv_headers:
                        message = 'CSV column "' + additional_file_field + '" registered in the "additional_files" configuration setting is missing from your CSV file.'
                        logging.error(message)
                        sys.exit('Error: ' + message)

            # Verify media use tids.
            # @todo: add the 'rows_with_missing_files' method of accumulating invalid values (issue 268).
            for additional_files_media_use_field, additional_files_media_use_tid in additional_files_entries.items():
                validate_media_use_tid_in_additional_files_setting(config, additional_files_media_use_tid, additional_files_media_use_field)

            if config['nodes_only'] is False and config['allow_missing_files'] is False:
                for count, file_check_row in enumerate(additional_files_check_csv_data, start=1):
                    for additional_file_field in additional_files_fields:
                        if len(file_check_row[additional_file_field]) == 0:
                            message = 'CVS row ' + file_check_row[config['id_field']] + ' contains an empty "' + additional_file_field + '" value.'
                            logging.error(message)
                            sys.exit('Error: ' + message)
                        file_check_row[additional_file_field] = file_check_row[additional_file_field].strip()
                        if file_check_row[additional_file_field].startswith('http'):
                            http_response_code = ping_remote_file(config, file_check_row[additional_file_field])
                            if http_response_code != 200 or ping_remote_file(config, file_check_row[additional_file_field]) is False:
                                message = 'Remote file ' + file_check_row[additional_file_field] + ' identified in CSV "' + additional_file_field + '" column for record with ID ' \
                                    + file_check_row[config['id_field']] + ' not found or not accessible (HTTP response code ' + str(http_response_code) + ').'
                                logging.error(message)
                                sys.exit('Error: ' + message)
                        if os.path.isabs(file_check_row[additional_file_field]):
                            file_path = file_check_row[additional_file_field]
                        else:
                            file_path = os.path.join(config['input_dir'], file_check_row[additional_file_field])
                        if not file_check_row[additional_file_field].startswith('http'):
                            if not os.path.exists(file_path) or not os.path.isfile(file_path):
                                message = 'File ' + file_path + ' identified in CSV "' + additional_file_field + '" column for record with ID ' \
                                    + file_check_row[config['id_field']] + ' not found.'
                                logging.error(message)
                                sys.exit('Error: ' + message)

                            # @todo: validate extensions of files added using 'additional_files' here - issue 126.

                message = 'OK, files named in the CSV "' + additional_file_field + '" column are all present.'
                print(message)
                logging.info(message)
            empty_file_values_exist = False
            if config['nodes_only'] is False and config['allow_missing_files'] is True:
                additional_files_check_csv_data = get_csv_data(config)
                additional_file_fields_for_message = []
                for count, file_check_row in enumerate(additional_files_check_csv_data, start=1):
                    for additional_file_field in additional_files_fields:
                        if len(file_check_row[additional_file_field]) == 0:
                            empty_file_values_exist = True
                        else:
                            if file_check_row[additional_file_field].startswith('http'):
                                http_response_code = ping_remote_file(config, file_check_row[additional_file_field])
                                if http_response_code != 200 or ping_remote_file(config, file_check_row[additional_file_field]) is False:
                                    message = 'Remote file ' + file_check_row[additional_file_field] + ' identified in CSV "' + additional_file_field + '" column for record with ID field value ' \
                                        + file_check_row[config['id_field']] + ' not found or not accessible (HTTP response code ' + str(http_response_code) + ').'
                                    logging.error(message)
                                    sys.exit('Error: ' + message)
                            else:
                                if os.path.isabs(file_check_row[additional_file_field]):
                                    file_path = file_check_row[additional_file_field]
                                else:
                                    file_path = os.path.join(config['input_dir'], file_check_row[additional_file_field])
                                if not os.path.exists(file_path) or not os.path.isfile(file_path):
                                    message = 'File ' + file_path + ' identified in CSV "' + additional_file_field + '" column not found.'
                                    logging.error(message)
                                    sys.exit('Error: ' + message)
                        if '"' + additional_file_field + '"' not in additional_file_fields_for_message:
                            additional_file_fields_for_message.append('"' + additional_file_field + '"')
                if empty_file_values_exist is True:
                    message = 'OK, files named in the CSV ' + ', '.join(additional_file_fields_for_message) + ' column(s) are all present; the "allow_missing_files" ' + \
                        'option is enabled and empty ' + ', '.join(additional_file_fields_for_message) + ' values exist.'
                    print(message)
                    logging.info(message)
                else:
                    message = 'OK, files named in the CSV ' + ', '.join(additional_file_fields_for_message) + ' column(s) are all present.'
                    print(message)
                    logging.info(message)

    if config['task'] == 'create' and config['paged_content_from_directories'] is True:
        if 'paged_content_page_model_tid' not in config:
            message = 'If you are creating paged content, you must include "paged_content_page_model_tid" in your configuration.'
            logging.error('Configuration requires "paged_content_page_model_tid" setting when creating paged content.')
            sys.exit('Error: ' + message)
        paged_content_from_directories_csv_data = get_csv_data(config)
        for count, file_check_row in enumerate(paged_content_from_directories_csv_data, start=1):
            dir_path = os.path.join(config['input_dir'], file_check_row[config['id_field']])
            if not os.path.exists(dir_path) or os.path.isfile(dir_path):
                message = 'Page directory ' + dir_path + ' for CSV record with ID "' + file_check_row[config['id_field']] + '"" not found.'
                logging.error(message)
                sys.exit('Error: ' + message)
            page_files = os.listdir(dir_path)
            if len(page_files) == 0:
                message = 'Page directory ' + dir_path + ' is empty.'
                print("Warning: " + message)
                logging.warning(message)
            for page_file_name in page_files:
                if config['paged_content_sequence_separator'] not in page_file_name:
                    message = 'Page file ' + os.path.join(dir_path, page_file_name) + ' does not contain a sequence separator (' + config['paged_content_sequence_separator'] + ').'
                    logging.error(message)
                    sys.exit('Error: ' + message)

        print('OK, page directories are all present.')

    # Check for bootstrap scripts, if any are configured.
    bootsrap_scripts_present = False
    if 'bootstrap' in config and len(config['bootstrap']) > 0:
        bootsrap_scripts_present = True
        for bootstrap_script in config['bootstrap']:
            if not os.path.exists(bootstrap_script):
                message = "Bootstrap script " + bootstrap_script + " not found."
                logging.error(message)
                sys.exit('Error: ' + message)
            if os.access(bootstrap_script, os.X_OK) is False:
                message = "Bootstrap script " + bootstrap_script + " is not executable."
                logging.error(message)
                sys.exit('Error: ' + message)
        if bootsrap_scripts_present is True:
            message = "OK, registered bootstrap scripts found and executable."
            logging.info(message)
            print(message)

    # Check for shutdown scripts, if any are configured.
    shutdown_scripts_present = False
    if 'shutdown' in config and len(config['shutdown']) > 0:
        shutdown_scripts_present = True
        for shutdown_script in config['shutdown']:
            if not os.path.exists(shutdown_script):
                message = "shutdown script " + shutdown_script + " not found."
                logging.error(message)
                sys.exit('Error: ' + message)
            if os.access(shutdown_script, os.X_OK) is False:
                message = "Shutdown script " + shutdown_script + " is not executable."
                logging.error(message)
                sys.exit('Error: ' + message)
        if shutdown_scripts_present is True:
            message = "OK, registered shutdown scripts found and executable."
            logging.info(message)
            print(message)

    # Check for preprocessor scripts, if any are configured.
    preprocessor_scripts_present = False
    if 'preprocessors' in config and len(config['preprocessors']) > 0:
        preprocessor_scripts_present = True
        for preprocessor_script in config['preprocessors']:
            if not os.path.exists(preprocessor_script):
                message = "Preprocessor script " + preprocessor_script + " not found."
                logging.error(message)
                sys.exit('Error: ' + message)
            if os.access(preprocessor_script, os.X_OK) is False:
                message = "Preprocessor script " + preprocessor_script + " is not executable."
                logging.error(message)
                sys.exit('Error: ' + message)
        if preprocessor_scripts_present is True:
            message = "OK, registered preprocessor scripts found and executable."
            logging.info(message)
            print(message)

    # Check for the existence and executableness of post-action scripts, if any are configured.
    if config['task'] == 'create' or config['task'] == 'update' or config['task'] == 'add_media':
        post_action_scripts_configs = ['node_post_create', 'node_post_update', 'media_post_create']
        for post_action_script_config in post_action_scripts_configs:
            post_action_scripts_present = False
            if post_action_script_config in config and len(config[post_action_script_config]) > 0:
                post_action_scripts_present = True
                for post_action_script in config[post_action_script_config]:
                    if not os.path.exists(post_action_script):
                        message = "Post-action script " + post_action_script + " not found."
                        logging.error(message)
                        sys.exit('Error: ' + message)
                    if os.access(post_action_script, os.X_OK) is False:
                        message = "Post-action script " + post_action_script + " is not executable."
                        logging.error(message)
                        sys.exit('Error: ' + message)
            if post_action_scripts_present is True:
                message = "OK, registered post-action scripts found and executable."
                logging.info(message)
                print(message)

    if config['task'] == 'export_csv':
        if 'node_id' not in csv_column_headers:
            message = 'For "export_csv" tasks, your CSV file must contain a "node_id" column.'
            logging.error(message)
            sys.exit('Error: ' + message)

        export_csv_term_mode_options = ['tid', 'name']
        if config['export_csv_term_mode'] not in export_csv_term_mode_options:
            message = 'Configuration option "export_csv_term_mode_options" must be either "tid" or "name".'
            logging.error(message)
            sys.exit('Error: ' + message)

        if config['export_file_directory'] is not None:
            if not os.path.exists(config['export_csv_file_path']):
                try:
                    os.mkdir(config['export_file_directory'])
                    os.rmdir(config['export_file_directory'])
                except Exception as e:
                    message = 'Path in configuration option "export_file_directory" ("' + config['export_file_directory'] + '") is not writable.'
                    logging.error(message + ' ' + str(e))
                    sys.exit('Error: ' + message + ' See log for more detail.')

        if config['export_file_media_use_term_id'] is False:
            message = f'Unknown value for configuration setting "export_file_media_use_term_id": {config["export_file_media_use_term_id"]}.'
            logging.error(message)
            sys.exit('Error: ' + message)

    # @todo issue 268: All checks for accumulator variables like 'rows_with_missing_files' should go here.
    if len(rows_with_missing_files) > 0 and config['strict_check'] is False:
        if config['allow_missing_files'] is False:
            logging.error('Missing or empty CSV "file" column values detected. See log entries above.')
            # @todo issue 268: Only exit if one or more of the checks have failed (i.e. do not exit on each check).
            sys.exit('Error: Missing or empty CSV "file" column values detected. See the log for more information.')

    # If nothing has failed by now, exit with a positive, upbeat message.
    print("Configuration and input data appear to be valid.")
    logging.info('Configuration checked for "%s" task using config file "%s", no problems found.', config['task'], args.config)

    if config['secondary_tasks'] is None:
        sys.exit(0)
    else:
        for secondary_config_file in config['secondary_tasks']:
            print("")
            print('Running --check using secondary configuration file "' + secondary_config_file + '"')
            if os.name == 'nt':
                # Assumes python.exe is in the user's PATH.
                cmd = ["python", "./workbench", "--config", secondary_config_file, "--check"]
            else:
                cmd = ["./workbench", "--config", secondary_config_file, "--check"]
            output = subprocess.run(cmd)

        sys.exit(0)


def get_registered_media_extensions(config, media_bundle, field_name_filter=None):
    """For the given media bundle, gets a list of file extensions registered in Drupal's
       "Allowed file extensions" configuration for each field that has this setting.
    """
    """Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        bundle_type : string
            The (node) content type, the vocabulary name, or the media type (image',
            'document', 'audio', 'video', 'file', etc.).
        field_name_filter: string
            If not None, filter the return value to just that field; if the field is
            not a key in the return dict, return False.
        Returns
        -------
        dict
            A dictionary with one key per media bundle field name that has registered exensions.
            Each key has as its value a list of file extensions, without leading periods,
            registered for those fields in Drupal. All extensions are lower case.
    """
    registered_extensions = dict()
    media_field_definitions = get_field_definitions(config, 'media', media_bundle)
    for field_name, field_def in media_field_definitions.items():
        if 'file_extensions' in field_def:
            registered_extensions[field_name] = re.split(r'\s+', field_def['file_extensions'])
            for i in range(len(registered_extensions[field_name])):
                registered_extensions[field_name][i] = registered_extensions[field_name][i].lower()

    if field_name_filter is not None and field_name_filter in registered_extensions:
        return {field_name_filter: registered_extensions[field_name_filter]}
    elif field_name_filter is not None and field_name_filter not in registered_extensions:
        return False
    else:
        return registered_extensions


def check_input_for_create_from_files(config, args):
    """Validate the config file and input data if task is 'create_from_files'.
    """
    if config['task'] != 'create_from_files':
        message = 'Your task must be "create_from_files".'
        logging.error(message)
        sys.exit('Error: ' + message)

    logging.info('Starting configuration check for "%s" task using config file %s.', config['task'], args.config)

    ping_islandora(config, print_message=False)

    config_keys = list(config.keys())
    unwanted_in_create_from_files = [
        'check',
        'delimiter',
        'subdelimiter',
        'allow_missing_files',
        'paged_content_from_directories',
        'delete_media_with_nodes',
        'allow_adding_terms']
    for option in unwanted_in_create_from_files:
        if option in config_keys:
            config_keys.remove(option)
    joiner = ', '
    # Check for presence of required config keys.
    create_required_options = [
        'task',
        'host',
        'username',
        'password']
    for create_required_option in create_required_options:
        if create_required_option not in config_keys:
            message = 'Please check your config file for required values: ' + joiner.join(create_required_options) + '.'
            logging.error(message)
            sys.exit('Error: ' + message)

    # Check existence of input directory.
    if os.path.exists(config['input_dir']):
        message = 'OK, input directory "' + config['input_dir'] + '" found.'
        print(message)
        logging.info(message)
    else:
        message = 'Input directory "' + config['input_dir'] + '"" not found.'
        logging.error(message)
        sys.exit('Error: ' + message)

    # Validate length of 'title'.
    files = os.listdir(config['input_dir'])
    for file_name in files:
        filename_without_extension = os.path.splitext(file_name)[0]
        if len(filename_without_extension) > int(config['max_node_title_length']):
            message = 'The filename "' + filename_without_extension + \
                '" exceeds Drupal\'s maximum length of ' + config['max_node_title_length'] + ' characters and cannot be used for a node title.'
            logging.error(message)
            sys.exit('Error: ' + message)

    # Check that either 'model' or 'models' are present in the config file.
    if ('model' not in config and 'models' not in config):
        message = 'You must include either the "model" or "models" option in your configuration.'
        logging.error(message)
        sys.exit('Error: ' + message)

    # If nothing has failed by now, exit with a positive message.
    print("Configuration and input data appear to be valid.")
    logging.info(
        'Configuration checked for "%s" task using config file %s, no problems found.',
        config['task'],
        args.config)
    sys.exit(0)


def log_field_cardinality_violation(field_name, record_id, cardinality):
    """Writes an entry to the log during create/update tasks if any field values
       are sliced off. Workbench does this if the number of values in a field
       exceeds the field's cardinality. record_id could be a value from the
       configured id_field or a node ID.
    """
    logging.warning(
        "Adding all values in CSV field %s for record %s would exceed maximum number of allowed values (%s). Skipping adding extra values.",
        field_name,
        record_id,
        cardinality)


def validate_language_code(langcode):
    # Drupal's language codes.
    codes = ['af', 'am', 'ar', 'ast', 'az', 'be', 'bg', 'bn', 'bo', 'bs',
             'ca', 'cs', 'cy', 'da', 'de', 'dz', 'el', 'en', 'en-x-simple', 'eo',
             'es', 'et', 'eu', 'fa', 'fi', 'fil', 'fo', 'fr', 'fy', 'ga', 'gd', 'gl',
             'gsw-berne', 'gu', 'he', 'hi', 'hr', 'ht', 'hu', 'hy', 'id', 'is', 'it',
             'ja', 'jv', 'ka', 'kk', 'km', 'kn', 'ko', 'ku', 'ky', 'lo', 'lt', 'lv',
             'mg', 'mk', 'ml', 'mn', 'mr', 'ms', 'my', 'ne', 'nl', 'nb', 'nn', 'oc',
             'pa', 'pl', 'pt-pt', 'pt-br', 'ro', 'ru', 'sco', 'se', 'si', 'sk', 'sl',
             'sq', 'sr', 'sv', 'sw', 'ta', 'ta-lk', 'te', 'th', 'tr', 'tyv', 'ug',
             'uk', 'ur', 'vi', 'xx-lolspeak', 'zh-hans', 'zh-hant']
    if langcode in codes:
        return True
    else:
        return False


def clean_csv_values(row):
    """Performs basic string cleanup on CSV values.
    """
    for field in row:
        # Replace smart/curly quotes with straight ones.
        row[field] = row[field].replace('“', '"').replace('”', '"')
        row[field] = row[field].replace("‘", "'").replace("’", "'")

        # Strip leading and trailing whitespace.
        row[field] = str(row[field]).strip()
    return row


def truncate_csv_value(field_name, record_id, field_config, value):
    """Drupal will not accept field values that have a length that
       exceeds the configured maximum length for that field. 'value'
       here is a field subvalue.
    """
    if isinstance(value, str) and 'max_length' in field_config:
        max_length = field_config['max_length']
        if max_length is not None and len(value) > int(max_length):
            original_value = value
            value = value[:max_length]
            logging.warning(
                'CSV field value "%s" in field "%s" (record ID %s) truncated at %s characters as required by the field\'s configuration.',
                original_value,
                field_name,
                record_id,
                max_length)
    return value


def get_node_field_values(config, nid):
    """Get a node's field data so we can use it during PATCH updates,
       which replace a field's values.
    """
    node_url = config['host'] + '/node/' + nid + '?_format=json'
    response = issue_request(config, 'GET', node_url)
    node_fields = json.loads(response.text)
    return node_fields


def get_target_ids(node_field_values):
    """Get the target IDs of all entities in a field.
    """
    target_ids = []
    for target in node_field_values:
        target_ids.append(target['target_id'])
    return target_ids


def get_additional_files_config(config):
    """Converts values in 'additional_files' config setting to a simple
       dictionary for easy access.
    """
    additional_files_entries = dict()
    if 'additional_files' in config and len(config['additional_files']) > 0:
        for additional_files_entry in config['additional_files']:
            for additional_file_field, additional_file_media_use_tid in additional_files_entry.items():
                additional_files_entries[additional_file_field] = additional_file_media_use_tid
    return additional_files_entries


def split_typed_relation_string(config, typed_relation_string, target_type):
    """Fields of type 'typed_relation' are represented in the CSV file
       using a structured string, specifically namespace:property:id,
       e.g., 'relators:pht:5'. 'id' is either a term ID or a node ID. This
       function takes one of those strings (optionally with a multivalue
       subdelimiter) and returns a list of dictionaries in the form they
       take in existing node values. ID values can also be term names (strings)
       and term URIs (also strings, but in the form 'http....').

       Also, these values can (but don't need to) have an optional namespace
       in the term ID segment, which is the vocabulary ID string. These
       typed relation strings look like 'relators:pht:person:Jordan, Mark'.
       However, since we split the typed relation strings only on the first
       two :, the entire third segment is considered, for the purposes of
       splitting the value, to be the term.
    """
    return_list = []
    temp_list = typed_relation_string.split(config['subdelimiter'])
    for item in temp_list:
        item_list = item.split(':', 2)
        if value_is_numeric(item_list[2]):
            target_id = int(item_list[2])
        else:
            target_id = item_list[2]
        item_dict = {
            'target_id': target_id,
            'rel_type': item_list[0] + ':' + item_list[1],
            'target_type': target_type}
        return_list.append(item_dict)

    return return_list


def split_geolocation_string(config, geolocation_string):
    """Fields of type 'geolocation' are represented in the CSV file using a
       structured string, specifically lat,lng, e.g. "49.16667, -123.93333"
       or "+49.16667, -123.93333". This function takes one of those strings
       (optionally with a multivalue subdelimiter) and returns a list of
       dictionaries with 'lat' and 'lng' keys required by the 'geolocation'
       field type.
    """
    return_list = []
    temp_list = geolocation_string.split(config['subdelimiter'])
    for item in temp_list:
        item_list = item.split(',')
        # Remove any leading \ which might be in value if it comes from a spreadsheet.
        item_dict = {'lat': item_list[0].lstrip('\\').strip(), 'lng': item_list[1].lstrip('\\').strip()}
        return_list.append(item_dict)

    return return_list


def split_link_string(config, link_string):
    """Fields of type 'link' are represented in the CSV file using a structured string,
       specifically uri%%title, e.g. "https://www.lib.sfu.ca%%SFU Library Website".
       This function takes one of those strings (optionally with a multivalue subdelimiter)
       and returns a list of dictionaries with 'uri' and 'title' keys required by the
       'link' field type.
    """
    return_list = []
    temp_list = link_string.split(config['subdelimiter'])
    for item in temp_list:
        if '%%' in item:
            item_list = item.split('%%', 1)
            item_dict = {'uri': item_list[0].strip(), 'title': item_list[1].strip()}
            return_list.append(item_dict)
        else:
            # If there is no %% and title, use the URL as the title.
            item_dict = {'uri': item.strip(), 'title': item.strip()}
            return_list.append(item_dict)

    return return_list


def split_authority_link_string(config, authority_link_string):
    """Fields of type 'authority_link' are represented in the CSV file using a structured string,
       specifically source%%uri%%title, e.g. "viaf%%http://viaf.org/viaf/153525475%%Rush (Musical group)".
       This function takes one of those strings (optionally with a multivalue subdelimiter)
       and returns a list of dictionaries with 'source', 'uri' and 'title' keys required by the
       'authority_link' field type.
    """
    return_list = []
    temp_list = authority_link_string.split(config['subdelimiter'])
    for item in temp_list:
        if item.count('%%') == 2:
            item_list = item.split('%%', 2)
            item_dict = {'source': item_list[0].strip(), 'uri': item_list[1].strip(), 'title': item_list[2].strip()}
            return_list.append(item_dict)
        if item.count('%%') == 1:
            # There is no title.
            item_list = item.split('%%', 1)
            item_dict = {'source': item_list[0].strip(), 'uri': item_list[1].strip(), 'title': ''}
            return_list.append(item_dict)

    return return_list


def split_media_track_string(config, media_track_string):
    """Fields of type 'media_track' are represented in the CSV file using a structured string,
       specifically 'label:kind:srclang:path_to_vtt_file', e.g. "en:subtitles:en:path/to/the/vtt/file.vtt".
       This function takes one of those strings (optionally with a multivalue subdelimiter) and returns
       a list of dictionaries with 'label', 'kind', 'srclang', 'file_path' keys required by the
       'media_track' field type.
    """
    return_list = []
    temp_list = media_track_string.split(config['subdelimiter'])
    for item in temp_list:
        track_parts_list = item.split(':', 3)
        item_dict = {
            'label': track_parts_list[0],
            'kind': track_parts_list[1],
            'srclang': track_parts_list[2],
            'file_path': track_parts_list[3]}
        return_list.append(item_dict)

    return return_list


def validate_media_use_tid_in_additional_files_setting(config, media_use_tid_value, additional_field_name):
    """Validate whether the term ID registered in the "additional_files" config setting
       is in the Islandora Media Use vocabulary.
    """
    media_use_tids = []
    if (config['subdelimiter'] in str(media_use_tid_value)):
        media_use_tids = str(media_use_tid_value).split(config['subdelimiter'])
    else:
        media_use_tids.append(media_use_tid_value)

    for media_use_tid in media_use_tids:
        if not value_is_numeric(media_use_tid) and media_use_tid.strip().startswith('http'):
            media_use_tid = get_term_id_from_uri(config, media_use_tid.strip())
        if not value_is_numeric(media_use_tid) and not media_use_tid.strip().startswith('http'):
            media_use_tid = find_term_in_vocab(config, 'islandora_media_use', media_use_tid.strip())

        term_endpoint = config['host'] + '/taxonomy/term/' + str(media_use_tid).strip() + '?_format=json'
        headers = {'Content-Type': 'application/json'}
        response = issue_request(config, 'GET', term_endpoint, headers)
        if response.status_code == 404:
            message = 'Term ID "' + str(media_use_tid) + '" registered in the "additional_files" config option ' + \
                'for field "' + additional_field_name + '" is not a term ID (term doesn\'t exist).'
            logging.error(message)
            sys.exit('Error: ' + message)
        if response.status_code == 200:
            response_body = json.loads(response.text)
            if 'vid' in response_body:
                if response_body['vid'][0]['target_id'] != 'islandora_media_use':
                    message = 'Term ID "' + str(media_use_tid) + '" registered in the "additional_files" config option ' + \
                        'for field "' + additional_field_name + '" is not in the Islandora Media Use vocabulary.'
                    logging.error(message)
                    sys.exit('Error: ' + message)
            if 'field_external_uri' in response_body:
                if len(response_body['field_external_uri']) > 0 and response_body['field_external_uri'][0]['uri'] != 'http://pcdm.org/use#OriginalFile':
                    message = 'Warning: Term ID "' + str(media_use_tid) + '" registered in the "additional_files" config option ' + \
                        'for CSV field "' + additional_field_name + '" will assign an Islandora Media Use term that might ' + \
                        "conflict with derivative media. You should temporarily disable the Context or Action that generates those derivatives."
                else:
                    # There is no field_external_uri so we can't identify the term. Provide a generic message.
                    message = 'Warning: Terms registered in the "additional_files" config option ' + \
                        'for CSV field "' + additional_field_name + '" may assign an Islandora Media Use term that will ' + \
                        "conflict with derivative media. You should temporarily disable the Context or Action that generates those derivatives."
                    print(message)
                    logging.warning(message)


def validate_media_use_tid(config, media_use_tid_value_from_csv=None, csv_row_id=None):
    """Validate whether the term ID, term name, or terms URI provided in the
       config value for media_use_tid is in the Islandora Media Use vocabulary.
    """
    if media_use_tid_value_from_csv is not None and csv_row_id is not None:
        if len(str(media_use_tid_value_from_csv)) > 0:
            media_use_tid_value = media_use_tid_value_from_csv
            message_wording = ' in the CSV "media_use_tid" column '
    else:
        media_use_tid_value = config['media_use_tid']
        message_wording = ' in configuration option "media_use_tid" '

    media_use_terms = str(media_use_tid_value).split(config['subdelimiter'])
    for media_use_term in media_use_terms:
        if value_is_numeric(media_use_term) is not True and media_use_term.strip().startswith('http'):
            media_use_tid = get_term_id_from_uri(config, media_use_term.strip())
            if csv_row_id is None:
                if media_use_tid is False:
                    message = 'URI "' + media_use_term + '" provided ' + message_wording + ' does not match any taxonomy terms.'
                    logging.error(message)
                    sys.exit('Error: ' + message)
                if media_use_tid is not False and media_use_term.strip() != 'http://pcdm.org/use#OriginalFile':
                    message = 'Warning: URI "' + media_use_term + '" provided' + message_wording + \
                        "will assign an Islandora Media Use term that might conflict with derivative media. " + \
                        "You should temporarily disable the Context or Action that generates those derivatives."
                    print(message)
                    logging.warning(message)
            else:
                if media_use_tid is False:
                    message = 'URI "' + media_use_term + '" provided in "media_use_tid" field in CSV row ' + \
                        str(csv_row_id) + ' does not match any taxonomy terms.'
                    logging.error(message)
                    sys.exit('Error: ' + message)
                if media_use_tid is not False and media_use_term.strip() != 'http://pcdm.org/use#OriginalFile':
                    message = 'Warning: URI "' + media_use_term + '" provided in "media_use_tid" field in CSV row ' + \
                        str(csv_row_id) + "will assign an Islandora Media Use term that might conflict with " + \
                        "derivative media. You should temporarily disable the Context or Action that generates those derivatives."
                    logging.warning(message)

        elif value_is_numeric(media_use_term) is not True and media_use_term.strip().startswith('http') is not True:
            media_use_tid = find_term_in_vocab(config, 'islandora_media_use', media_use_term.strip())
            if csv_row_id is None:
                if media_use_tid is False:
                    message = 'Warning: Term name "' + media_use_term.strip() + '" provided in configuration option "media_use_tid" does not match any taxonomy terms.'
                    logging.warning(message)
                    sys.exit('Error: ' + message)
            else:
                if media_use_tid is False:
                    message = 'Warning: Term name "' + media_use_term.strip() + '" provided in "media_use_tid" field in CSV row ' + \
                        str(csv_row_id) + ' does not match any taxonomy terms.'
                    logging.warning(message)
                    sys.exit('Error: ' + message)
        else:
            # Confirm the tid exists and is in the islandora_media_use vocabulary
            term_endpoint = config['host'] + '/taxonomy/term/' + str(media_use_term.strip()) + '?_format=json'
            headers = {'Content-Type': 'application/json'}
            response = issue_request(config, 'GET', term_endpoint, headers)
            if response.status_code == 404:
                if csv_row_id is None:
                    message = 'Term ID "' + str(media_use_term) + '" used in the "media_use_tid" configuration option is not a term ID (term doesn\'t exist).'
                    logging.error(message)
                    sys.exit('Error: ' + message)
                else:
                    message = 'Term ID "' + str(media_use_term) + '" used in the "media_use_tid" field in CSV row ' + \
                        str(csv_row_id) + ' is not a term ID (term doesn\'t exist).'
                    logging.error(message)
                    sys.exit('Error: ' + message)
            if response.status_code == 200:
                response_body = json.loads(response.text)
                if csv_row_id is None:
                    if 'vid' in response_body:
                        if response_body['vid'][0]['target_id'] != 'islandora_media_use':
                            message = 'Term ID "' + \
                                str(media_use_term) + '" provided in configuration option "media_use_tid" is not in the Islandora Media Use vocabulary.'
                            logging.error(message)
                            sys.exit('Error: ' + message)
                    if 'field_external_uri' in response_body:
                        if response_body['field_external_uri'][0]['uri'] != 'http://pcdm.org/use#OriginalFile':
                            message = 'Warning: Term ID "' + media_use_term + '" provided in configuration option "media_use_tid" ' + \
                                "will assign an Islandora Media Use term that might conflict with derivative media. " + \
                                " You should temporarily disable the Context or Action that generates those derivatives."
                            print(message)
                            logging.warning(message)
                else:
                    if 'vid' in response_body:
                        if response_body['vid'][0]['target_id'] != 'islandora_media_use':
                            message = 'Term ID "' + \
                                str(media_use_term) + '" provided in the "media_use_tid" field in CSV row ' + \
                                str(csv_row_id) + ' is not in the Islandora Media Use vocabulary.'
                            logging.error(message)
                            sys.exit('Error: ' + message)
                    if 'field_external_uri' in response_body:
                        if response_body['field_external_uri'][0]['uri'] != 'http://pcdm.org/use#OriginalFile':
                            message = 'Warning: Term ID "' + media_use_term + '" provided in "media_use_tid" field in CSV row ' + \
                                str(csv_row_id) + " will assign an Islandora Media Use term that might conflict with " + \
                                "derivative media. You should temporarily disable the Context or Action that generates those derivatives."
                            print(message)
                            logging.warning(message)


def validate_media_use_tids_in_csv(config, csv_data):
    """Validate 'media_use_tid' values in CSV if they exist.
    """
    if config['task'] == 'add_media':
        csv_id_field = 'node_id'
    else:
        csv_id_field = config['id_field']

    for count, row in enumerate(csv_data, start=1):
        if 'media_use_tid' in row:
            delimited_field_values = row['media_use_tid'].split(config['subdelimiter'])
            for field_value in delimited_field_values:
                if len(field_value.strip()) > 0:
                    validate_media_use_tid(config, field_value, row[csv_id_field])


def preprocess_field_data(subdelimiter, field_value, path_to_script):
    """Executes a field preprocessor script and returns its output and exit status code. The script
       is passed the field subdelimiter as defined in the config YAML and the field's value, and
       prints a modified vesion of the value (result) back to this function.
    """
    cmd = subprocess.Popen([path_to_script, subdelimiter, field_value], stdout=subprocess.PIPE)
    result, stderrdata = cmd.communicate()

    return result, cmd.returncode


def execute_bootstrap_script(path_to_script, path_to_config_file):
    """Executes a bootstrap script and returns its output and exit status code.
    """
    cmd = subprocess.Popen([path_to_script, path_to_config_file], stdout=subprocess.PIPE)
    result, stderrdata = cmd.communicate()

    return result, cmd.returncode


def execute_shutdown_script(path_to_script, path_to_config_file):
    """Executes a shutdown script and returns its output and exit status code.
    """
    cmd = subprocess.Popen([path_to_script, path_to_config_file], stdout=subprocess.PIPE)
    result, stderrdata = cmd.communicate()

    return result, cmd.returncode


def execute_entity_post_task_script(path_to_script, path_to_config_file, http_response_code, entity_json=''):
    """Executes a entity-level post-task script and returns its output and exit status code.
    """
    cmd = subprocess.Popen([path_to_script, path_to_config_file, str(http_response_code), entity_json], stdout=subprocess.PIPE)
    result, stderrdata = cmd.communicate()

    return result, cmd.returncode


def create_file(config, filename, file_fieldname, node_csv_row, node_id):
    """Creates a file in Drupal, which is then referenced by the accompanying media.
           Parameters
           ----------
            config : dict
                The configuration object defined by set_config_defaults().
            filename : string
                The full path to the file (either from the 'file' CSV column or downloaded from somewhere).
            file_fieldname: string
                The name of the CSV column containing the filename.
            node_csv_row: OrderedDict
                E.g., OrderedDict([('file', 'IMG_5083.JPG'), ('id', '05'), ('title', 'Alcatraz Island').
            node_id: string
                The nid of the parent media's parent node.
            Returns
            -------
            int|bool|None
                The file ID (int) of the successfully created file; False if there is insufficient
                information to create the file or file creation failed, or None if config['nodes_only'] or
                config['allow_missing_files'] is True.
    """
    if config['nodes_only'] is True:
        return None

    if config['task'] == 'add_media' or config['task'] == 'create':
        if config['allow_missing_files'] and len(node_csv_row[file_fieldname].strip()) == 0:
            return None

    is_remote = False
    filename = filename.strip()

    if filename.startswith('http'):
        remote_file_http_response_code = ping_remote_file(config, filename)
        if remote_file_http_response_code != 200:
            return False

        filename_parts = urllib.parse.urlparse(filename)
        file_path = download_remote_file(config, filename, file_fieldname, node_csv_row, node_id)
        if file_path is False:
            return False
        filename = file_path.split("/")[-1]
        is_remote = True
    elif os.path.isabs(filename):
        file_path = filename
    else:
        file_path = os.path.join(config['input_dir'], filename)

    mimetype = mimetypes.guess_type(file_path)
    media_type = set_media_type(config, file_path, file_fieldname, node_csv_row)
    if media_type in config['media_type_file_fields']:
        media_file_field = config['media_type_file_fields'][media_type]
    else:
        logging.error('File not created for CSV row "%s": media type "%s" not recognized.', node_csv_row[config['id_field']], media_type)
        return False

    # Requests/urllib3 requires filenames used in Content-Disposition headers to be encoded as latin-1.
    # Since it is impossible to reliably convert to latin-1 without knowing the source encoding of the filename
    # (which may or may not have originated on the machine running Workbench, so sys.stdout.encoding isn't reliable),
    # the best we can do for now is to use unidecode to replace non-ASCII characters in filenames with their ASCII
    # equivalents (at least the unidecode() equivalents). Also, while Requests requires filenames to be encoded
    # in latin-1, Drupal passes filenames through its validateUtf8() function. So ASCII is a low common denominator
    # of both requirements.
    ascii_only = is_ascii(filename)
    if ascii_only is False:
        original_filename = copy.copy(filename)
        filename = unidecode(filename)
        logging.warning("Filename '" + original_filename + "' contains non-ASCII characters, normalized to '" + filename + "'.")

    file_endpoint_path = '/file/upload/media/' + media_type + '/' + media_file_field + '?_format=json'
    file_headers = {
        'Content-Type': 'application/octet-stream',
        'Content-Disposition': 'file; filename="' + filename + '"'
    }

    binary_data = open(file_path, 'rb')

    try:
        file_response = issue_request(config, 'POST', file_endpoint_path, file_headers, '', binary_data)
        if file_response.status_code == 201:
            file_json = json.loads(file_response.text)
            file_id = file_json['fid'][0]['value']
            # For now, we can only validate checksums for files named in the 'file' CSV column.
            # See https://github.com/mjordan/islandora_workbench/issues/307.
            if config['fixity_algorithm'] is not None and file_fieldname == 'file':
                file_uuid = file_json['uuid'][0]['value']
                hash_from_drupal = get_file_hash_from_drupal(config, file_uuid, config['fixity_algorithm'])
                hash_from_local = get_file_hash_from_local(config, file_path, config['fixity_algorithm'])
                if hash_from_drupal == hash_from_local:
                    logging.info('Local and Drupal %s checksums for file "%s" (%s) match.', config['fixity_algorithm'], file_path, hash_from_local)
                else:
                    print("Warning: local and Drupal checksums for '" + file_path + "' do not match. See the log for more detail.")
                    logging.warning('Local and Drupal %s checksums for file "%s" (named in CSV row "%s") do not match (local: %s, Drupal: %s).',
                                    config['fixity_algorithm'], file_path, node_csv_row[config['id_field']], hash_from_local, hash_from_drupal)
                if 'checksum' in node_csv_row:
                    if hash_from_local == node_csv_row['checksum'].strip():
                        logging.info('Local %s checksum and value in the CSV "checksum" field for file "%s" (%s) match.', config['fixity_algorithm'], file_path, hash_from_local)
                    else:
                        print("Warning: local checksum and value in CSV for '" + file_path + "' do not match. See the log for more detail.")
                        logging.warning('Local %s checksum and value in the CSV "checksum" field for file "%s" (named in CSV row "%s") do not match (local: %s, CSV: %s).',
                                        config['fixity_algorithm'], file_path, node_csv_row[config['id_field']], hash_from_local, node_csv_row['checksum'])
            if is_remote and config['delete_tmp_upload'] is True:
                containing_folder = os.path.join(config['input_dir'], re.sub('[^A-Za-z0-9]+', '_', node_csv_row[config['id_field']]))
                try:
                    # E.g., on Windows, "[WinError 32] The process cannot access the file because it is being used by another process"
                    shutil.rmtree(containing_folder)
                except PermissionError as e:
                    logging.error(e)

            return file_id
        else:
            logging.error('File not created, POST request to "%s" returned an HTTP status code of "%s" and a response body of %s.',
                          file_endpoint_path, file_response.status_code, file_response.content)
            return False
    except requests.exceptions.RequestException as e:
        logging.error(e)
        return False


def create_media(config, filename, file_fieldname, node_id, node_csv_row, media_use_tid=None):
    """Creates a media in Drupal.

           Parameters
           ----------
            config : dict
                The configuration object defined by set_config_defaults().
            filename : string
                The value of the CSV 'file' field for the current node.
            file_fieldname: string
                The name of the CSV column containing the filename.
            node_id: string
                The ID of the node to attach the media to. This is False if file creation failed.
            node_csv_row: OrderedDict
                E.g., OrderedDict([('file', 'IMG_5083.JPG'), ('id', '05'), ('title', 'Alcatraz Island').
            media_use_tid : int|str
                A valid term ID (or a subdelimited list of IDs) from the Islandora Media Use vocabulary.
            Returns
            -------
            int|False
                 The HTTP status code from the attempt to create the media, False if
                 it doesn't have sufficient information to create the media, or None
                 if config['nodes_only'] is True.
    """
    if config['nodes_only'] is True:
        return

    # media_type_for_oembed_check = set_media_type(config, filename, file_fieldname, node_csv_row)
    media_type = set_media_type(config, filename, file_fieldname, node_csv_row)

    if media_type in get_oembed_media_types(config):
        # file_result must be an integer.
        file_result = -1
    else:
        file_result = create_file(config, filename, file_fieldname, node_csv_row, node_id)

    if filename.startswith('http'):
        if file_result is False:
            return False
        filename = get_preprocessed_file_path(config, file_fieldname, node_csv_row, node_id, False)

    if isinstance(file_result, int):
        if 'media_use_tid' in node_csv_row and len(node_csv_row['media_use_tid']) > 0:
            media_use_tid_value = node_csv_row['media_use_tid']
        else:
            media_use_tid_value = config['media_use_tid']

        if media_use_tid is not None:
            media_use_tid_value = media_use_tid

        media_use_tids = []
        media_use_terms = str(media_use_tid_value).split(config['subdelimiter'])
        for media_use_term in media_use_terms:
            if value_is_numeric(media_use_term):
                media_use_tids.append(media_use_term)
            if not value_is_numeric(media_use_term) and media_use_term.strip().startswith('http'):
                media_use_tids.append(get_term_id_from_uri(config, media_use_term))
            if not value_is_numeric(media_use_term) and not media_use_term.strip().startswith('http'):
                media_use_tids.append(find_term_in_vocab(config, 'islandora_media_use', media_use_term.strip()))

        media_bundle_response_code = ping_media_bundle(config, media_type)
        if media_bundle_response_code == 404:
            message = 'File "' + filename + '" identified in CSV row ' + file_fieldname + \
                ' will create a media of type (' + media_type + '), but that media type is not configured in the destination Drupal.'
            logging.error(message)
            return False

        media_field = config['media_type_file_fields'][media_type]
        if media_type in get_oembed_media_types(config):
            if 'title' in node_csv_row:
                media_name = node_csv_row['title']
            else:
                media_name = get_node_title_from_nid(config, node_id)
                if not media_name:
                    message = 'Cannot access node " + node_id + ", so cannot get its title for use in media title. Using oEmbed URL instead.'
                    logging.warning(message)
                    media_name = filename
        else:
            media_name = os.path.basename(filename)

        if config['use_node_title_for_media']:
            if 'title' in node_csv_row:
                media_name = node_csv_row['title']
            else:
                media_name = get_node_title_from_nid(config, node_id)
                if not media_name:
                    message = 'Cannot access node " + node_id + ", so cannot get its title for use in media title. Using filename instead.'
                    logging.warning(message)
                    media_name = os.path.basename(filename)
        if config['use_nid_in_media_title']:
            media_name = f"{node_id}-Original File"
        if config['field_for_media_title']:
            media_name = node_csv_row[config['field_for_media_title']].replace(':', '_')

        # Create a media from an oEmbed URL.
        if media_type in get_oembed_media_types(config):
            media_json = {
                "bundle": [{
                    "target_id": media_type,
                    "target_type": "media_type",
                }],
                "status": [{
                    "value": True
                }],
                "name": [{
                    "value": media_name
                }],
                media_field: [{
                    "value": filename
                }],
                "field_media_of": [{
                    "target_id": int(node_id),
                    "target_type": 'node'
                }],
                "field_media_use": [{
                    "target_id": media_use_tids[0],
                    "target_type": 'taxonomy_term'
                }]
            }
        # Create a media from a local or remote file.
        else:
            media_json = {
                "bundle": [{
                    "target_id": media_type,
                    "target_type": "media_type",
                }],
                "status": [{
                    "value": True
                }],
                "name": [{
                    "value": media_name
                }],
                media_field: [{
                    "target_id": file_result,
                    "target_type": 'file'
                }],
                "field_media_of": [{
                    "target_id": int(node_id),
                    "target_type": 'node'
                }],
                "field_media_use": [{
                    "target_id": media_use_tids[0],
                    "target_type": 'taxonomy_term'
                }]
            }

        # Populate some media type-specific fields on the media. @todo: We need a generalized way of
        # determining which media fields are required, e.g. checking the media type configuration.
        if media_field == 'field_media_image':
            if 'image_alt_text' in node_csv_row and len(node_csv_row['image_alt_text']) > 0:
                alt_text = clean_image_alt_text(node_csv_row['image_alt_text'])
                media_json[media_field][0]['alt'] = alt_text
            else:
                alt_text = clean_image_alt_text(media_name)
                media_json[media_field][0]['alt'] = alt_text

        # extracted_text media must have their field_edited_text field populated for full text indexing.
        if media_type == 'extracted_text':
            if os.path.exists(filename):
                media_json['field_edited_text'] = list()
                extracted_text_file = open(filename, 'r', -1, 'utf-8')
                media_json['field_edited_text'].append({'value': extracted_text_file.read()})
            else:
                logging.error("Extracted text file %s not found.", filename)

        # Create media_track files here, since they should exist before we create the parent media.
        media_types_with_track_files = config['media_track_file_fields'].keys()
        valid_media_track_fields = list()
        if media_type in media_types_with_track_files:
            # Check for fields in node_csv_row that have names like 'media:video:field_track' and validate their contents.
            # Note: Does not validate the fields' configuration (--check does that).
            node_csv_field_names = list(node_csv_row.keys())
            if len(node_csv_field_names):
                media_track_fields = [x for x in node_csv_field_names if x.startswith('media:' + media_type)]
                # Should be just one field per media type.
                if len(media_track_fields) and media_type in config['media_track_file_fields']:
                    for media_track_field in media_track_fields:
                        if validate_media_track_value(node_csv_row[media_track_field]) is True:
                            valid_media_track_fields.append(media_track_field)

            # Create the media track file(s) for each entry in valid_potential_media_track_fields (there could be multiple track entries).
            if len(valid_media_track_fields):
                media_track_field_data = []
                # Should be just one field per media type.
                fully_qualified_media_track_field_name = valid_media_track_fields[0]
                media_track_entries = split_media_track_string(config, node_csv_row[fully_qualified_media_track_field_name])
                for media_track_entry in media_track_entries:
                    media_track_field_name_parts = fully_qualified_media_track_field_name.split(':')
                    create_track_file_result = create_file(config, media_track_entry['file_path'], media_track_field_name_parts[2], node_csv_row, node_id)
                    if create_track_file_result is not False and isinstance(create_track_file_result, int):
                        # /entity/file/663?_format=json will return JSON containing the file's 'uri'.
                        track_file_info_response = issue_request(config, 'GET', f"/entity/file/{create_track_file_result}?_format=json")
                        track_file_info = json.loads(track_file_info_response.text)
                        track_file_url = track_file_info['uri'][0]['url']
                        logging.info(f"Media track file {config['host'].rstrip('/')}{track_file_url} created from {media_track_entry['file_path']}.")
                        track_file_data = {
                            'target_id': track_file_info['fid'][0]['value'],
                            'kind': media_track_entry['kind'],
                            'label': media_track_entry['label'],
                            'srclang': media_track_entry['srclang'],
                            'default': False,
                            'url': track_file_url}
                        media_track_field_data.append(track_file_data)
                    else:
                        # If there are any failures, proceed with creating the parent media.
                        logging.error(f"Media track using {media_track_entry['file_path']} not created; create_file returned {create_track_file_result}.")

                # Set the "default" attribute of the first media track.
                media_track_field_data[0]['default'] = True
                media_json[media_track_field_name_parts[2]] = media_track_field_data

        media_endpoint_path = '/entity/media'
        media_headers = {
            'Content-Type': 'application/json'
        }
        try:
            media_response = issue_request(config, 'POST', media_endpoint_path, media_headers, media_json)
            if media_response.status_code != 201:
                logging.error('Media not created, POST request to "%s" returned an HTTP status code of "%s" and a response body of %s.',
                              media_endpoint_path, media_response.status_code, media_response.content)
                logging.error('JSON request body used in previous POST to "%s" was %s.', media_endpoint_path, media_json)

            if len(media_use_tids) > 1:
                media_response_body = json.loads(media_response.text)
                if 'mid' in media_response_body:
                    media_id = media_response_body['mid'][0]['value']
                    patch_media_use_terms(config, media_id, media_type, media_use_tids)
                else:
                    logging.error("Could not PATCH additional media use terms to media created from '%s' because media ID is not available.", filename)

            # Execute media-specific post-create scripts, if any are configured.
            if 'media_post_create' in config and len(config['media_post_create']) > 0:
                for command in config['media_post_create']:
                    post_task_output, post_task_return_code = execute_entity_post_task_script(command, config['config_file_path'], media_response.status_code, media_response.text)
                    if post_task_return_code == 0:
                        logging.info("Post media create script " + command + " executed successfully.")
                    else:
                        logging.error("Post media create script " + command + " failed.")

            return media_response.status_code
        except requests.exceptions.RequestException as e:
            logging.error(e)
            return False

    if file_result is False:
        return file_result

    if file_result is None:
        return file_result


def create_islandora_media(config, filename, file_fieldname, node_uri, node_csv_row, media_use_tid=None):
    """node_csv_row is an OrderedDict, e.g.
       OrderedDict([('file', 'IMG_5083.JPG'), ('id', '05'), ('title', 'Alcatraz Island').

       Returns the HTTP status code from the attempt to create the media, or False if
       it doesn't have sufficient information to create the media.
    """
    if config['nodes_only'] is True:
        return

    is_remote = False

    filename = filename.strip()
    if filename.startswith('http'):
        remote_file_http_reponse = ping_remote_file(config, filename)
        if remote_file_http_reponse != 200:
            return False
        file_path = download_remote_file(config, filename, file_fieldname, node_csv_row)
        if file_path is False:
            return False
        filename = file_path.split("/")[-1]
        is_remote = True
    elif os.path.isabs(filename):
        file_path = filename
    else:
        file_path = os.path.join(config['input_dir'], filename)

    mimetype = mimetypes.guess_type(file_path)
    media_type = set_media_type(config, filename, file_fieldname, node_csv_row)
    media_bundle_response_code = ping_media_bundle(config, media_type)
    if media_bundle_response_code == 404:
        message = 'File "' + filename + '" identified in CSV row ' + file_fieldname + \
            ' will create a media of type (' + media_type + '), but that media type is not configured in the destination Drupal.'
        logging.error(message)
        return False

    if 'media_use_tid' in node_csv_row and len(node_csv_row['media_use_tid']) > 0:
        media_use_tid_value = node_csv_row['media_use_tid']
    else:
        media_use_tid_value = config['media_use_tid']

    if media_use_tid is not None:
        media_use_tid_value = media_use_tid

    media_use_tids = []
    media_use_terms = str(media_use_tid_value).split(config['subdelimiter'])
    for media_use_term in media_use_terms:
        if value_is_numeric(media_use_term):
            media_use_tids.append(media_use_term)
        if not value_is_numeric(media_use_term) and media_use_term.strip().startswith('http'):
            media_use_tids.append(get_term_id_from_uri(config, media_use_term))
        if not value_is_numeric(media_use_term) and not media_use_term.strip().startswith('http'):
            media_use_tids.append(find_term_in_vocab(config, 'islandora_media_use', media_use_term.strip()))

    media_endpoint_path = '/media/' + media_type + '/' + str(media_use_tids[0])
    media_endpoint = node_uri + media_endpoint_path
    location = config['drupal_filesystem'] + os.path.basename(filename)
    media_headers = {
        'Content-Type': mimetype[0],
        'Content-Location': location
    }
    binary_data = open(file_path, 'rb')
    media_response = issue_request(config, 'PUT', media_endpoint, media_headers, '', binary_data)

    # Execute media-specific post-create scripts, if any are configured.
    if 'media_post_create' in config and len(config['media_post_create']) > 0:
        for command in config['media_post_create']:
            post_task_output, post_task_return_code = execute_entity_post_task_script(command, config['config_file_path'], media_response.status_code, media_response.text)
            if post_task_return_code == 0:
                logging.info("Post media create script " + command + " executed successfully.")
            else:
                logging.error("Post media create script " + command + " failed.")

    if is_remote and config['delete_tmp_upload'] is True:
        containing_folder = os.path.join(config['input_dir'], re.sub('[^A-Za-z0-9]+', '_', node_csv_row[config['id_field']]))
        shutil.rmtree(containing_folder)

    if media_response.status_code == 201:
        if 'location' in media_response.headers:
            # A 201 response provides a 'location' header, but a '204' response does not.
            media_uri = media_response.headers['location']
            logging.info("Media (%s) created at %s, linked to node %s.", media_type, media_uri, node_uri)
            media_id = media_uri.rsplit('/', 1)[-1]
            patch_media_fields(config, media_id, media_type, node_csv_row)

            if media_type == 'image':
                patch_image_alt_text(config, media_id, node_csv_row)

            if len(media_use_tids) > 1:
                patch_media_use_terms(config, media_id, media_type, media_use_tids)
    elif media_response.status_code == 204:
        if len(media_use_tids) > 1:
            patch_media_use_terms(config, media_id, media_type, media_use_tids)
        logging.warning(
            "Media created and linked to node %s, but its URI is not available since its creation returned an HTTP status code of %s",
            node_uri,
            media_response.status_code)
        logging.warning("Media linked to node %s base fields not updated.", node_uri)
    else:
        logging.error('Media not created, PUT request to "%s" returned an HTTP status code of "%s".', media_endpoint, media_response.status_code)

    binary_data.close()

    return media_response.status_code


def patch_media_fields(config, media_id, media_type, node_csv_row):
    """Patch the media entity with base fields from the parent node.
    """
    media_json = {
        'bundle': [
            {'target_id': media_type}
        ]
    }

    for field_name, field_value in node_csv_row.items():
        if field_name == 'created' and len(field_value) > 0:
            media_json['created'] = [{'value': field_value}]
        if field_name == 'uid' and len(field_value) > 0:
            media_json['uid'] = [{'target_id': field_value}]

    if len(media_json) > 1:
        if config['standalone_media_url'] is True:
            endpoint = config['host'] + '/media/' + str(media_id) + '?_format=json'
        else:
            endpoint = config['host'] + '/media/' + str(media_id) + '/edit?_format=json'
        headers = {'Content-Type': 'application/json'}
        response = issue_request(config, 'PATCH', endpoint, headers, media_json)
        if response.status_code == 200:
            logging.info("Media %s fields updated to match parent node's.", endpoint)
        else:
            logging.warning("Media %s fields not updated to match parent node's.", endpoint)


def patch_media_use_terms(config, media_id, media_type, media_use_tids):
    """Patch the media entity's field_media_use.
    """
    media_json = {
        'bundle': [
            {'target_id': media_type}
        ]
    }

    media_use_tids_json = []
    for media_use_tid in media_use_tids:
        media_use_tids_json.append({'target_id': media_use_tid, 'target_type': 'taxonomy_term'})

    media_json['field_media_use'] = media_use_tids_json
    if config['standalone_media_url'] is True:
        endpoint = config['host'] + '/media/' + str(media_id) + '?_format=json'
    else:
        endpoint = config['host'] + '/media/' + str(media_id) + '/edit?_format=json'
    headers = {'Content-Type': 'application/json'}
    response = issue_request(config, 'PATCH', endpoint, headers, media_json)
    if response.status_code == 200:
        logging.info("Media %s Islandora Media Use terms updated.", endpoint)
    else:
        logging.warning("Media %s Islandora Media Use terms not updated.", endpoint)


def clean_image_alt_text(input_string):
    ''' Strip out HTML markup to guard against CSRF in alt text.
    '''
    cleaned_string = re.sub('<[^<]+?>', '', input_string)
    return cleaned_string


def patch_image_alt_text(config, media_id, node_csv_row):
    """Patch the alt text value for an image media. Use the parent node's title
       unless the CSV record contains an image_alt_text field with something in it.
    """
    if config['standalone_media_url'] is True:
        get_endpoint = config['host'] + '/media/' + str(media_id) + '?_format=json'
    else:
        get_endpoint = config['host'] + '/media/' + str(media_id) + '/edit?_format=json'
    get_headers = {'Content-Type': 'application/json'}
    get_response = issue_request(config, 'GET', get_endpoint, get_headers)
    get_response_body = json.loads(get_response.text)
    field_media_image_target_id = get_response_body['field_media_image'][0]['target_id']

    for field_name, field_value in node_csv_row.items():
        if field_name == 'title':
            alt_text = clean_image_alt_text(field_value)
        if field_name == 'image_alt_text' and len(field_value) > 0:
            alt_text = clean_image_alt_text(field_value)

    media_json = {
        'bundle': [
            {'target_id': 'image'}
        ],
        'field_media_image': [
            {"target_id": field_media_image_target_id, "alt": alt_text}
        ],
    }

    if config['standalone_media_url'] is True:
        patch_endpoint = config['host'] + '/media/' + str(media_id) + '?_format=json'
    else:
        patch_endpoint = config['host'] + '/media/' + str(media_id) + '/edit?_format=json'
    patch_headers = {'Content-Type': 'application/json'}
    patch_response = issue_request(
        config,
        'PATCH',
        patch_endpoint,
        patch_headers,
        media_json)

    if patch_response.status_code != 200:
        logging.warning("Alt text for image media %s not updated.", patch_endpoint)


def remove_media_and_file(config, media_id):
    """Delete a media and the file associated with it.
    """
    # First get the media JSON.
    if config['standalone_media_url'] is True:
        get_media_url = config['host'] + '/media/' + str(media_id) + '?_format=json'
    else:
        get_media_url = config['host'] + '/media/' + str(media_id) + '/edit?_format=json'
    get_media_response = issue_request(config, 'GET', get_media_url)
    get_media_response_body = json.loads(get_media_response.text)

    # See https://github.com/mjordan/islandora_workbench/issues/446 for background.
    if 'message' in get_media_response_body and get_media_response_body['message'].startswith("No route found for"):
        message = f'Please visit {config["host"]}/admin/config/media/media-settings and uncheck the "Standalone media URL" option.'
        logging.error(message)
        sys.exit("Error: " + message)

    # See https://github.com/mjordan/islandora_workbench/issues/446 for background.
    if get_media_response.status_code == 403:
        message = f'If the "Standalone media URL" option at {config["host"]}/admin/config/media/media-settings is unchecked, clear your Drupal cache and run Workbench again.'
        logging.error(message)
        sys.exit("Error: " + message)

    for file_field_name in file_fields:
        if file_field_name in get_media_response_body:
            try:
                file_id = get_media_response_body[file_field_name][0]['target_id']
            except Exception as e:
                logging.error("Unable to get file ID for media %s (reason: %s); proceeding to delete media without file.", media_id, e)
                file_id = None
            break

    # Delete the file first.
    if file_id is not None:
        file_endpoint = config['host'] + '/entity/file/' + str(file_id) + '?_format=json'
        file_response = issue_request(config, 'DELETE', file_endpoint)
        if file_response.status_code == 204:
            logging.info("File %s (from media %s) deleted.", file_id, media_id)
        else:
            logging.error("File %s (from media %s) not deleted (HTTP response code %s).", file_id, media_id, file_response.status_code)

    # Delete any audio/video media_track files.
    media_bundle_name = get_media_response_body['bundle'][0]['target_id']
    if media_bundle_name in config['media_track_file_fields']:
        track_file_field = config['media_track_file_fields'][media_bundle_name]
        for track_file in get_media_response_body[track_file_field]:
            track_file_id = track_file['target_id']
            track_file_endpoint = config['host'] + '/entity/file/' + str(track_file_id) + '?_format=json'
            track_file_response = issue_request(config, 'DELETE', track_file_endpoint)
            if track_file_response.status_code == 204:
                logging.info("Media track file %s (from media %s) deleted.", track_file_id, media_id)
            else:
                logging.error("Media track file %s (from media %s) not deleted (HTTP response code %s).", track_file_id, media_id, track_file_response.status_code)

    # Then the media.
    if file_response.status_code == 204 or file_id is None:
        if config['standalone_media_url'] is True:
            media_endpoint = config['host'] + '/media/' + str(media_id) + '?_format=json'
        else:
            media_endpoint = config['host'] + '/media/' + str(media_id) + '/edit?_format=json'
        media_response = issue_request(config, 'DELETE', media_endpoint)
        if media_response.status_code == 204:
            logging.info("Media %s deleted.", media_id)
            return media_response.status_code
        else:
            logging.error("Media %s not deleted (HTTP response code %s).", media_id, media_response.status_code)
            return False

    return False


def get_csv_data(config, csv_file_target='node_fields', file_path=None):
    """Read the input CSV data and prepare it for use in create, update, etc. tasks.

       This function reads the source CSV file (or the CSV dump from Google Sheets or Excel),
       applies some prepocessing to each CSV record (specifically, it adds any CSV field
       templates that are registered in the config file, and it filters out any CSV
       records or lines in the CSV file that begine with a #), and finally, writes out
       a version of the CSV data to a file that appends .preprocessed to the input
       CSV file name. It is this .preprocessed file that is used in create, update, etc.
       tasks.
    """
    """Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        csv_file_target: string
            Either 'node_fields' or 'taxonomy_fields'.
        file_path: string
            The path to the file to check (applies only to vocabulary CSVs).
        Returns
        -------
        preprocessed_csv_reader
            The CSV DictReader object.
    """
    if csv_file_target == 'node_fields':
        file_path = config['input_csv']

    if os.path.isabs(file_path):
        input_csv_path = file_path
    elif file_path.startswith('http') is True:
        input_csv_path = os.path.join(config['input_dir'], config['google_sheets_csv_filename'])
        if not os.path.exists(input_csv_path):
            get_csv_from_google_sheet(config)
    elif file_path.endswith('.xlsx') is True:
        input_csv_path = os.path.join(config['input_dir'], config['excel_csv_filename'])
        if not os.path.exists(input_csv_path):
            get_csv_from_excel(config)
    else:
        input_csv_path = os.path.join(config['input_dir'], file_path)

    if not os.path.exists(input_csv_path):
        message = 'CSV file ' + input_csv_path + ' not found.'
        logging.error(message)
        sys.exit("Error: " + message)

    try:
        # 'utf-8-sig' encoding skips Microsoft BOM (0xef, 0xbb, 0xbf) at the start of files,
        # e.g. exported from Excel and has no effect when reading standard UTF-8 encoded files.
        csv_reader_file_handle = open(input_csv_path, 'r', encoding="utf-8-sig", newline='')
    except (UnicodeDecodeError):
        message = 'Error: CSV file ' + input_csv_path + ' must be encoded in ASCII or UTF-8.'
        logging.error(message)
        sys.exit(message)

    # 'restval' is what is used to populate superfluous fields/labels.
    csv_writer_file_handle = open(input_csv_path + '.preprocessed', 'w+', newline='', encoding='utf-8')
    csv_reader = csv.DictReader(csv_reader_file_handle, delimiter=config['delimiter'], restval='stringtopopulateextrafields')

    csv_reader_fieldnames = csv_reader.fieldnames
    confirmed = []
    duplicates = []
    for item in csv_reader_fieldnames:
        if item not in confirmed:
            confirmed.append(item)
        else:
            duplicates.append(item)
    if len(duplicates) > 0:
        message = "Error: CSV has duplicate header names - " + ', '.join(duplicates)
        logging.error(message)
        sys.exit(message)
    csv_reader_fieldnames = [x for x in csv_reader_fieldnames if x not in config['ignore_csv_columns']]

    tasks = ['create', 'update']
    # CSV field templates only apply to node CSV files, not vocabulary CSV files.
    if config['task'] in tasks and csv_file_target == 'node_fields' and 'csv_field_templates' in config and len(config['csv_field_templates']) > 0:
        # If the config file contains CSV field templates, append them to the CSV data.
        # Make a copy of the column headers so we can skip adding templates to the new CSV
        # if they're present in the source CSV. We don't want fields in the source CSV to be
        # stomped on by templates.
        csv_reader_fieldnames_orig = copy.copy(csv_reader_fieldnames)
        for template in config['csv_field_templates']:
            for field_name, field_value in template.items():
                if field_name not in csv_reader_fieldnames_orig:
                    csv_reader_fieldnames.append(field_name)
        csv_writer = csv.DictWriter(csv_writer_file_handle, fieldnames=csv_reader_fieldnames, delimiter=config['delimiter'])
        csv_writer.writeheader()
        row_num = 0
        unique_identifiers = []
        # We subtract 1 from config['csv_start_row'] so user's expectation of the actual
        # start row match up with Python's 0-based counting.
        if config['csv_start_row'] > 0:
            csv_start_row = config['csv_start_row'] - 1
        else:
            csv_start_row = config['csv_start_row']
        for row in itertools.islice(csv_reader, csv_start_row, config['csv_stop_row']):
            row_num += 1

            # Remove columns specified in config['ignore_csv_columns'].
            if len(config['ignore_csv_columns']) > 0:
                for column_to_ignore in config['ignore_csv_columns']:
                    if column_to_ignore in row:
                        del row[column_to_ignore]

            for template in config['csv_field_templates']:
                for field_name, field_value in template.items():
                    if field_name not in csv_reader_fieldnames_orig:
                        row[field_name] = field_value

            # Skip CSV records whose first column begin with #.
            if not list(row.values())[0].startswith('#'):
                try:
                    unique_identifiers.append(row[config['id_field']])
                    csv_writer.writerow(row)
                except (ValueError):
                    # Note: this message is also generated in check_input().
                    message = "Row " + str(row_num) + " (ID " + row[config['id_field']] + ') of the CSV file "' + input_csv_path + '" ' + \
                              "has more columns (" + str(len(row)) + ") than there are headers (" + \
                              str(len(csv_reader.fieldnames)) + ').'
                    logging.error(message)
                    print('Error: ' + message)
                    sys.exit(message)
        repeats = set(([x for x in unique_identifiers if unique_identifiers.count(x) > 1]))
        if len(repeats) > 0:
            message = "Duplicate identifiers in column " + config['id_field'] + " found: " + str(repeats)
            logging.error(message)
            sys.exit("Error: " + message)
    else:
        csv_writer = csv.DictWriter(csv_writer_file_handle, fieldnames=csv_reader_fieldnames, delimiter=config['delimiter'])
        csv_writer.writeheader()
        row_num = 0
        # We subtract 1 from config['csv_start_row'] so user's expectation of the actual
        # start row match up with Python's 0-based counting.
        if config['csv_start_row'] > 0:
            csv_start_row = config['csv_start_row'] - 1
        else:
            csv_start_row = config['csv_start_row']
        for row in itertools.islice(csv_reader, csv_start_row, config['csv_stop_row']):
            row_num += 1
            # Remove columns specified in config['ignore_csv_columns'].
            if len(config['ignore_csv_columns']) > 0:
                for column_to_ignore in config['ignore_csv_columns']:
                    if column_to_ignore in row:
                        del row[column_to_ignore]

            # Skip CSV records whose first column begin with #.
            if not list(row.values())[0].startswith('#'):
                try:
                    csv_writer.writerow(row)
                except (ValueError):
                    # Note: this message is also generated in check_input().
                    message = "Row " + str(row_num) + " (ID " + row[config['id_field']] + ') of the CSV file "' + input_csv_path + '" ' + \
                              "has more columns (" + str(len(row)) + ") than there are headers (" + \
                              str(len(csv_reader.fieldnames)) + ').'
                    logging.error(message)
                    sys.exit('Error: ' + message)

    csv_writer_file_handle.close()
    preprocessed_csv_reader_file_handle = open(input_csv_path + '.preprocessed', 'r', encoding='utf-8')
    preprocessed_csv_reader = csv.DictReader(preprocessed_csv_reader_file_handle, delimiter=config['delimiter'], restval='stringtopopulateextrafields')
    return preprocessed_csv_reader


def find_term_in_vocab(config, vocab_id, term_name_to_find):
    """Query the Term from term name View using the vocab_id to see if term_name_to_find is
       is found in that vocabulary. If so, returns the term ID; if not returns False. If
       more than one term found, returns the term ID of the first one. Also populates global
       lists of terms (checked_terms and newly_created_terms) to reduce queries to Drupal.
    """
    """Parameters
    ----------
    config : dict
        The configuration object defined by set_config_defaults().
    vocab_id: string
        The vocabulary ID to use in the query to find the term.
    field_name: string
        The field's machine name.
    term_name_to_find: string
        The term name from CSV.
    Returns
    -------
    int|boolean
        The term ID, existing or newly created. Returns False if term name
        is not found (or config['validate_terms_exist'] is False).
    """
    if 'check' in config.keys() and config['check'] is True:
        if config['validate_terms_exist'] is False:
            return False

        # Attempt to detect term names (including typed relation taxonomy terms) that are namespaced. Some term names may
        # contain a colon (which is used in the incoming CSV to seprate the vocab ID from the term name). If there is
        # a ':', maybe it's part of the term name and it's not namespaced. To find out, split term_name_to_find
        # and compare the first segment with the vocab_id.
        if ':' in term_name_to_find:
            original_term_name_to_find = copy.copy(term_name_to_find)
            [tentative_vocab_id, tentative_term_name] = term_name_to_find.split(':', maxsplit=1)
            if tentative_vocab_id.strip() == vocab_id.strip():
                term_name_to_find = tentative_term_name
            else:
                term_name_to_find = original_term_name_to_find

        '''
        # Namespaced terms (inc. typed relation terms): if a vocabulary namespace is present, we need to split it out
        # from the term name. This only applies in --check since namespaced terms are parsed in prepare_term_id().
        # Assumptions: the term namespace always directly precedes the term name, and the term name may
        # contain a colon. See https://github.com/mjordan/islandora_workbench/issues/361 for related logic.
        namespaced = re.search(':', term_name_to_find)
        if namespaced:
            namespaced_term_parts = term_name_to_find.split(':')
            # Assumption is that the term name is the last part, and the namespace is the second-last.
            term_name_to_find = namespaced_term_parts[-1]
            vocab_id = namespaced_term_parts[-2]
        '''

        term_name_for_check_matching = term_name_to_find.lower().strip()
        for checked_term in checked_terms:
            if checked_term['vocab_id'] == vocab_id and checked_term['name_for_matching'] == term_name_for_check_matching:
                if value_is_numeric(checked_term['tid']):
                    return checked_term['tid']
                else:
                    return False

    for newly_created_term in newly_created_terms:
        if newly_created_term['vocab_id'] == vocab_id and newly_created_term['name_for_matching'] == term_name_to_find.lower().strip():
            return newly_created_term['tid']

    url = config['host'] + '/term_from_term_name?vocab=' + vocab_id.strip() + '&name=' + urllib.parse.quote_plus(term_name_to_find.strip()) + '&_format=json'
    response = issue_request(config, 'GET', url)
    if response.status_code == 200:
        term_data = json.loads(response.text)
        # Term name is not found.
        if len(term_data) == 0:
            if 'check' in config.keys() and config['check'] is True:
                checked_term_to_add = {'tid': None, 'vocab_id': vocab_id, 'name': term_name_to_find, 'name_for_matching': term_name_for_check_matching}
                if checked_term_to_add not in checked_terms:
                    checked_terms.append(checked_term_to_add)
            return False
        elif len(term_data) > 1:
            print("Warning: See log for important message about duplicate terms within the same vocabulary.")
            logging.warning(
                'Query for term "%s" found %s terms with that name in the %s vocabulary. Workbench is choosing the first term ID (%s)).',
                term_name_to_find,
                len(term_data),
                vocab_id,
                term_data[0]['tid'][0]['value'])
            if 'check' in config.keys() and config['check'] is True:
                checked_term_to_add = {'tid': term_data[0]['tid'][0]['value'], 'vocab_id': vocab_id, 'name': term_name_to_find, 'name_for_matching': term_name_for_check_matching}
                if checked_term_to_add not in checked_terms:
                    checked_terms.append(checked_term_to_add)
            return term_data[0]['tid'][0]['value']
        # Term name is found.
        else:
            if 'check' in config.keys() and config['check'] is True:
                checked_term_to_add = {'tid': term_data[0]['tid'][0]['value'], 'vocab_id': vocab_id, 'name': term_name_to_find, 'name_for_matching': term_name_for_check_matching}
                if checked_term_to_add not in checked_terms:
                    checked_terms.append(checked_term_to_add)
            return term_data[0]['tid'][0]['value']
    else:
        logging.warning('Query for term "%s" in vocabulary "%s" returned a %s status code', term_name_to_find, vocab_id, response.status_code)
        return False


def get_term_vocab(config, term_id):
    """Get the term's parent vocabulary ID and return it. If the term doesn't
       exist, return False.
    """
    url = config['host'] + '/taxonomy/term/' + str(term_id).strip() + '?_format=json'
    response = issue_request(config, 'GET', url)
    if response.status_code == 200:
        term_data = json.loads(response.text)
        return term_data['vid'][0]['target_id']
    else:
        logging.warning('Query for term ID "%s" returned a %s status code', term_id, response.status_code)
        return False


def get_term_name(config, term_id):
    """Get the term's name and return it. If the term doesn't exist, return False.
    """
    url = config['host'] + '/taxonomy/term/' + str(term_id).strip() + '?_format=json'
    response = issue_request(config, 'GET', url)
    if response.status_code == 200:
        term_data = json.loads(response.text)
        return term_data['name'][0]['value']
    else:
        logging.warning('Query for term ID "%s" returned a %s status code', term_id, response.status_code)
        return False


def get_term_uri(config, term_id):
    """Get the term's URI and return it. If the term or URI doesn't exist, return False.
       If the term has no URI, return None.
    """
    url = config['host'] + '/taxonomy/term/' + str(term_id).strip() + '?_format=json'
    response = issue_request(config, 'GET', url)
    if response.status_code == 200:
        term_data = json.loads(response.text)
        if 'field_external_uri' in term_data:
            uri = term_data['field_external_uri'][0]['uri']
            return uri
        elif 'field_authority_link' in term_data:
            uri = term_data['field_authority_link'][0]['uri']
            return uri
        else:
            logging.warning('Query for term ID "%s" does not have either a field_authority_link or field_exteral_uri field.', term_id)
            return None
    else:
        logging.warning('Query for term ID "%s" returned a %s status code', term_id, response.status_code)
        return False


def get_term_id_from_uri(config, uri):
    """For a given URI, query the Term from URI View created by the Islandora
       Workbench Integration module. Because we don't know which field each
       taxonomy uses to store URIs (it's either field_external_uri or field_authority_link),
       we need to check both options in the "Term from URI" View.
    """
    # Some vocabularies use this View.
    terms_with_uri = []
    term_from_uri_url = config['host'] + '/term_from_uri?_format=json&uri=' + uri.replace('#', '%23')
    term_from_uri_response = issue_request(config, 'GET', term_from_uri_url)
    if term_from_uri_response.status_code == 200:
        term_from_uri_response_body_json = term_from_uri_response.text
        term_from_uri_response_body = json.loads(term_from_uri_response_body_json)
        if len(term_from_uri_response_body) == 1:
            tid = term_from_uri_response_body[0]['tid'][0]['value']
            return tid
        if len(term_from_uri_response_body) > 1:
            for term in term_from_uri_response_body:
                terms_with_uri.append({term['tid'][0]['value']: term['vid'][0]['target_id']})
                tid = term_from_uri_response_body[0]['tid'][0]['value']
            print("Warning: See log for important message about use of term URIs.")
            logging.warning(
                'Term URI "%s" is used for more than one term (with these term ID/vocabulary ID combinations: ' +
                str(terms_with_uri) +
                '). Workbench is choosing the first term ID (%s)).',
                uri,
                tid)
            return tid

    # And some vocabuluaries use this View.
    term_from_authority_link_url = config['host'] + '/term_from_authority_link?_format=json&authority_link=' + uri.replace('#', '%23')
    term_from_authority_link_response = issue_request(config, 'GET', term_from_authority_link_url)
    if term_from_authority_link_response.status_code == 200:
        term_from_authority_link_response_body_json = term_from_authority_link_response.text
        term_from_authority_link_response_body = json.loads(term_from_authority_link_response_body_json)
        if len(term_from_authority_link_response_body) == 1:
            tid = term_from_authority_link_response_body[0]['tid'][0]['value']
            return tid
        elif len(term_from_authority_link_response_body) > 1:
            for term in term_from_authority_link_response_body:
                terms_with_uri.append({term['tid'][0]['value']: term['vid'][0]['target_id']})
                tid = term_from_authority_link_response_body[0]['tid'][0]['value']
            print("Warning: See log for important message about use of term URIs.")
            logging.warning(
                'Term URI "%s" is used for more than one term (with these term ID/vocabulary ID combinations: ' +
                str(terms_with_uri) +
                '). Workbench is choosing the first term ID (%s)).',
                uri,
                tid)
            return tid
        else:
            # URI does not match any term.
            return False

    # Non-200 response code.
    return False


def get_all_representations_of_term(config, vocab_id=None, name=None, term_id=None, uri=None):
    """Parameters
    ----------
    config : dict
        The configuration object defined by set_config_defaults().
    vocab_id: string
        The vocabulary ID to use in the query to find the term. Required if 'name' is the other arguments.
    name: string
        The term name.
    term_id: int
        The term ID. Does not require any other named arguments, since term IDs are unique.
    uri: string
        The term URI. Does not require any other named arguments, since term IDs (in theory) are unique.
    Returns
    -------
    dict/False
        A dictionary containing keys 'term_id', 'name', and 'uri. False if there is insufficient
        information to get all representations of the term.
    """
    if term_id is not None and value_is_numeric(term_id):
        name = get_term_name(config, term_id)
        uri = get_term_uri(config, term_id)
    elif name is not None:
        if vocab_id is None:
            return False
        term_id = find_term_in_vocab(config, vocab_id, name)
        uri = get_term_uri(config, term_id)
    elif uri is not None:
        term_id = get_term_id_from_uri(config, uri)
        name = get_term_name(config, term_id)

    return {'term_id': term_id, 'name': name, 'uri': uri}


def create_term(config, vocab_id, term_name, term_csv_row=None):
    """Adds a term to the target vocabulary. Returns the new term's ID
       if successful (or if the term already exists) or False if not.
    """
    """Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        vocab_id: string
            The vocabulary ID.
        term_name: string
            The term name from CSV.
        term_csv_row: OrderedDict
            ECSV row containing term field data. Only present if we are creating
            complex or child terms, not present for simple terms.
        Returns
        -------
        string|boolean
            The term ID, or False term was not created.
    """
    # Check to see if term exists; if so, return its ID, if not, proceed to create it.
    tid = find_term_in_vocab(config, vocab_id, term_name)
    if value_is_numeric(tid):
        logging.info('Term "%s" (term ID %s) already exists in vocabulary "%s".', term_name, tid, vocab_id)
        return tid

    if config['allow_adding_terms'] is False:
        logging.warning('To create new taxonomy terms, you must add "allow_adding_terms: true" to your configuration file.')
        return False

    if len(term_name) > 255:
        truncated_term_name = term_name[:255]
        message = 'Term "' + term_name + '"' + "provided in the CSV data exceeds Drupal's maximum length of 255 characters."
        message_2 = ' It has been trucated to "' + truncated_term_name + '".'
        logging.info(message + message_2)
        term_name = truncated_term_name

    term_field_data = get_term_field_data(config, vocab_id, term_name, term_csv_row)
    if term_field_data is False:
        # @todo: Failure details should be logged in get_term_field_data().
        logging.warning('Unable to create term "' + term_name + '" because Workbench could not get term field data.')
        return False

    # Common values for all terms, simple and complex.
    term = {
        "vid": [
           {
               "target_id": str(vocab_id),
               "target_type": "taxonomy_vocabulary"
           }
        ],
        "name": [
            {
                "value": term_name
            }
        ]
    }

    term.update(term_field_data)

    term_endpoint = config['host'] + '/taxonomy/term?_format=json'
    headers = {'Content-Type': 'application/json'}
    response = issue_request(config, 'POST', term_endpoint, headers, term, None)
    if response.status_code == 201:
        term_response_body = json.loads(response.text)
        tid = term_response_body['tid'][0]['value']
        logging.info('Term %s ("%s") added to vocabulary "%s".', tid, term_name, vocab_id)
        newly_created_term_name_for_matching = term_name.lower().strip()
        newly_created_terms.append({'tid': tid, 'vocab_id': vocab_id, 'name': term_name, 'name_for_matching': newly_created_term_name_for_matching})
        return tid
    else:
        logging.warning("Term '%s' not created, HTTP response code was %s.", term_name, response.status_code)
        return False


def get_term_field_data(config, vocab_id, term_name, term_csv_row):
    """Assemble the dict that will be added to the 'term' dict in create_term(). status, description,
       weight, parent, default_langcode, path fields are added here, even for simple term_name-only
       terms. Check the vocabulary CSV file to see if there is a corresponding row. If the vocabulary
       has any required fields, and any of them are absent, return False.
    """
    """Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        vocab_id: string
            The vocabulary ID.
        term_name: string
            The term name from CSV.
        term_csv_row: OrderedDict
            ECSV row containing term field data.
        Returns
        -------
        dict|boolean
            The dict containing the term field data, or False if this is not possible.
            @note: reason why creating JSON is not possible should be logged in this function.
    """
    # 'vid' and 'name' are added in create_term().
    term_field_data = {
        "status": [
            {
                "value": True
            }
        ],
        "description": [
            {
                "value": "",
                "format": None
            }
        ],
        "weight": [
            {
                "value": 0
            }
        ],
        "parent": [
            {
                "target_type": "taxonomy_term",
                "target_id": None
            }
        ],
        "default_langcode": [
            {
                "value": True
            }
        ],
        "path": [
            {
                "alias": None,
                "pid": None,
                "langcode": "en"
            }
        ]
    }

    # We're creating a simple term, with only a term name.
    if term_csv_row is None:
        return term_field_data
    # We're creating a complex term, with extra fields.
    else:
        # Importing the workbench_fields module at the top of this module with the
        # rest of the imports causes a circular import exception, so we do it here.
        import workbench_fields

        vocab_field_definitions = get_field_definitions(config, 'taxonomy_term', vocab_id.strip())

        # Build the JSON from the CSV row and create the term.
        vocab_csv_column_headers = term_csv_row.keys()
        for field_name in vocab_csv_column_headers:
            # term_name is the "id" field in the vocabulary CSV and not a field in the term JSON, so skip it.
            if field_name == 'term_name':
                continue

            # 'parent' field is present and not empty, so we need to look up the parent term. All terms
            # that are parents will have already been created back in workbench.create_terms() as long as
            # they preceded the children. If they come after the children in the CSV, we create the child
            # term anyway but log that the parent could not be found.
            if 'parent' in term_csv_row and len(term_csv_row['parent'].strip()) != 0:
                parent_tid = find_term_in_vocab(config, vocab_id, term_csv_row['parent'])
                if value_is_numeric(parent_tid):
                    term_field_data['parent'][0]['target_id'] = str(parent_tid)
                else:
                    # Create the term, but log that its parent could not be found.
                    message = 'Term "' + term_csv_row['term_name'] + '" added to vocabulary "' + vocab_id + '", but without its parent "' + \
                        term_csv_row['parent'] + '", which isn\'t present in that vocabulary (possibly hasn\'t been create yet?).'
                    logging.warning(message)

            # 'parent' is not a field added to the term JSON in the field handlers, so skip it.
            if field_name == 'parent':
                continue

            # Set 'description' and 'weight' JSON values if there are corresponding columns in the CSV.
            if 'weight' in term_csv_row and len(term_csv_row['weight'].strip()) != 0:
                if value_is_numeric(term_csv_row['weight']):
                    term_field_data['weight'][0]['value'] = str(term_csv_row['weight'])
                else:
                    # Create the term, but log that its weight could not be populated.
                    message = 'Term "' + term_csv_row['term_name'] + '" added to vocabulary "' + vocab_id + '", but without its weight "' + \
                        term_csv_row['weight'] + '", which must be an integer.'
                    logging.warning(message)

            # 'weight' is not a field added to the term JSON in the field handlers, so skip it.
            if field_name == 'weight':
                continue

            if 'description' in term_csv_row and len(term_csv_row['description'].strip()) != 0:
                term_field_data['description'][0]['value'] = term_csv_row['description']

            # 'description' is not a field added to the term JSON in the field handlers, so skip it.
            if field_name == 'description':
                continue

            # Assemble additional Drupal field structures for entity reference fields from CSV data.
            # Entity reference fields (taxonomy_term and node)
            if vocab_field_definitions[field_name]['field_type'] == 'entity_reference':
                entity_reference_field = workbench_fields.EntityReferenceField()
                term_field_data = entity_reference_field.create(config, vocab_field_definitions, term_field_data, term_csv_row, field_name)

            # Typed relation fields.
            elif vocab_field_definitions[field_name]['field_type'] == 'typed_relation':
                typed_relation_field = workbench_fields.TypedRelationField()
                term_field_data = typed_relation_field.create(config, vocab_field_definitions, term_field_data, term_csv_row, field_name)

            # Geolocation fields.
            elif vocab_field_definitions[field_name]['field_type'] == 'geolocation':
                geolocation_field = workbench_fields.GeolocationField()
                term_field_data = geolocation_field.create(config, vocab_field_definitions, term_field_data, term_csv_row, field_name)

            # Link fields.
            elif vocab_field_definitions[field_name]['field_type'] == 'link':
                link_field = workbench_fields.LinkField()
                term_field_data = link_field.create(config, vocab_field_definitions, term_field_data, term_csv_row, field_name)

            # Authority Link fields.
            elif vocab_field_definitions[field_name]['field_type'] == 'authority_link':
                authority_link_field = workbench_fields.AuthorityLinkField()
                term_field_data = authority_link_field.create(config, vocab_field_definitions, term_field_data, term_csv_row, field_name)

            # For non-entity reference and non-typed relation fields (text, integer, boolean etc.).
            else:
                simple_field = workbench_fields.SimpleField()
                term_field_data = simple_field.create(config, vocab_field_definitions, term_field_data, term_csv_row, field_name)

        return term_field_data


def get_term_uuid(config, term_id):
    """Given a term ID, get the term's UUID.
    """
    term_url = config['host'] + '/taxonomy/term/' + str(term_id) + '?_format=json'
    response = issue_request(config, 'GET', term_url)
    term = json.loads(response.text)
    uuid = term['uuid'][0]['value']

    return uuid


def create_url_alias(config, node_id, url_alias):
    json = {'path': [
            {'value': '/node/' + str(node_id)}
            ],
            'alias': [
            {'value': url_alias}
    ]
    }

    headers = {'Content-Type': 'application/json'}
    response = issue_request(
        config,
        'POST',
        config['host'] +
        '/entity/path_alias?_format=json',
        headers,
        json,
        None)
    if response.status_code != 201:
        logging.error(
            "URL alias '%s' not created for node %s, HTTP response code was %s (it might already exist).",
            url_alias,
            config['host'] +
            '/node/' +
            node_id,
            response.status_code)


def prepare_term_id(config, vocab_ids, field_name, term):
    """Checks to see if 'term' is numeric (i.e., a term ID) and if it is, returns it as
       is. If it's not (i.e., it's a string term name) it looks for the term name in the
       referenced vocabulary and returns its term ID if the term exists, and if it doesn't
       exist, creates the term and returns the new term ID.
    """
    """Parameters
    ----------
    config : dict
        The configuration object defined by set_config_defaults().
    vocab_ids: list
        The vocabulary IDs associated with the field handling code calling this function.
    field_name: string
        The field's machine name.
    term: string
        The term name from CSV.
    Returns
    -------
    int
        The term ID, existing or newly created.
"""
    term = str(term)
    term = term.strip()
    if value_is_numeric(term):
        return term
    # Special case: if the term starts with 'http', assume it's a Linked Data URI
    # and get its term ID from the URI.
    elif term.startswith('http'):
        # Note: get_term_id_from_uri() will return False if the URI doesn't match a term.
        tid_from_uri = get_term_id_from_uri(config, term)
        if value_is_numeric(tid_from_uri):
            return tid_from_uri
    else:
        if len(vocab_ids) == 1:
            # A namespace is not needed but it might be present. If there is,
            # since this vocabulary is the only one linked to its field,
            # we remove it before sending it to create_term().
            namespaced = re.search(':', term)
            if namespaced:
                [vocab_id, term_name] = term.split(':', maxsplit=1)
                if vocab_id == vocab_ids[0]:
                    tid = create_term(config, vocab_id.strip(), term_name.strip())
                    return tid
                else:
                    tid = create_term(config, vocab_ids[0].strip(), term.strip())
                    return tid
            else:
                tid = create_term(config, vocab_ids[0].strip(), term.strip())
                return tid
        else:
            # Term names used in multi-taxonomy fields. They need to be namespaced with
            # the taxonomy ID.
            #
            # If the field has more than one vocabulary linked to it, we don't know which
            # vocabulary the user wants a new term to be added to, and if the term name is
            # already used in any of the taxonomies linked to this field, we also don't know
            # which vocabulary to look for it in to get its term ID. Therefore, we always need
            # to namespace term names if they are used in multi-taxonomy fields.
            #
            # Split the namespace/vocab ID from the term name on ':'.
            if ':' in term:
                [tentative_vocab_id, term_name] = term.split(':', maxsplit=1)
                for vocab_id in vocab_ids:
                    if tentative_vocab_id == vocab_id:
                        tid = create_term(config, vocab_id.strip(), term_name.strip())
                        return tid
            else:
                tid = create_term(config, vocab_ids.strip(), term.strip())
                return tid

        # Explicitly return None if hasn't retured from one of the conditions above, e.g. if
        # the term name contains a colon and it wasn't namespaced with a valid vocabulary ID.
        return None


def get_field_vocabularies(config, field_definitions, field_name):
    """Gets IDs of vocabularies linked from the current field (could be more than one).
    """
    if 'vocabularies' in field_definitions[field_name]:
        vocabularies = field_definitions[field_name]['vocabularies']
        return vocabularies
    else:
        return False


def value_is_numeric(value):
    """Tests to see if value is numeric.
    """
    var = str(value)
    var = var.strip()
    if var.isnumeric():
        return True
    else:
        return False


def compare_strings(known, unknown):
    """Normalizes the unknown string and the known one, and compares
       them. If they match, returns True, if not, False. We could
       use FuzzyWuzzy or something but this is probably sufficient.
    """
    # Strips leading and trailing whitespace.
    known = known.strip()
    unknown = unknown.strip()
    # Converts to lower case.
    known = known.lower()
    unknown = unknown.lower()
    # Remove all punctuation.
    for p in string.punctuation:
        known = known.replace(p, ' ')
        unknown = unknown.replace(p, ' ')
    # Replaces whitespace with a single space.
    known = " ".join(known.split())
    unknown = " ".join(unknown.split())

    if unknown == known:
        return True
    else:
        return False


def get_csv_record_hash(row):
    """Concatenate values in the CSV record and get an MD5 hash on the
       resulting string.
    """
    serialized_row = ''
    for field in row:
        if isinstance(row[field], str) or isinstance(row[field], int):
            if isinstance(row[field], int):
                row[field] = str(row[field])
            row_value = row[field].strip()
            row_value = " ".join(row_value.split())
            serialized_row = serialized_row + row_value + " "

    serialized_row = bytes(serialized_row.strip().lower(), 'utf-8')
    hash_object = hashlib.md5(serialized_row)
    return hash_object.hexdigest()


def validate_input_dir(config):
    # Check existence input directory.
    if os.path.isabs(config['input_dir']):
        input_dir_path = config['input_dir']
    else:
        input_dir_path = os.path.abspath(config['input_dir'])
    if not os.path.exists(input_dir_path):
        message = 'Input directory specified in the "input_dir" configuration setting ("' + config['input_dir'] + '") not found.'
        logging.error(message)
        sys.exit('Error: ' + message)


def validate_csv_field_cardinality(config, field_definitions, csv_data):
    """Compare values in the CSV data with the fields' cardinality. Log CSV
       fields that have more values than allowed, and warn user if
       these fields exist in their CSV data.
    """
    # Temporary fix for https://github.com/mjordan/islandora_workbench/issues/443.
    if config['task'] == 'update':
        config['id_field'] = 'node_id'

    field_cardinalities = dict()
    csv_headers = csv_data.fieldnames
    for csv_header in csv_headers:
        if csv_header in field_definitions.keys():
            cardinality = field_definitions[csv_header]['cardinality']
            # We don't care about cardinality of -1 (unlimited).
            if int(cardinality) > 0:
                field_cardinalities[csv_header] = cardinality

    for count, row in enumerate(csv_data, start=1):
        for field_name in field_cardinalities.keys():
            if field_name in row:
                # Don't check for the subdelimiter in title.
                if field_name == 'title':
                    continue
                delimited_field_values = row[field_name].split(config['subdelimiter'])
                if field_cardinalities[field_name] == 1 and len(delimited_field_values) > 1:
                    if config['task'] == 'create':
                        message = 'CSV field "' + field_name + '" in record with ID ' + row[config['id_field']] + ' contains more values than the number '
                    if config['task'] == 'update':
                        message = 'CSV field "' + field_name + '" in record with node ID ' + row['node_id'] + ' contains more values than the number '
                    message_2 = 'allowed for that field (' + str(field_cardinalities[field_name]) + '). Workbench will add only the first value.'
                    print('Warning: ' + message + message_2)
                    logging.warning(message + message_2)
                if int(field_cardinalities[field_name]) > 1 and len(delimited_field_values) > field_cardinalities[field_name]:
                    if config['task'] == 'create':
                        message = 'CSV field "' + field_name + '" in record with ID ' + row[config['id_field']] + ' contains more values than the number '
                    if config['task'] == 'update':
                        message = 'CSV field "' + field_name + '" in record with node ID ' + row['node_id'] + ' contains more values than the number '
                    message_2 = 'allowed for that field (' + str(field_cardinalities[field_name]) + '). Workbench will add only the first ' + str(
                        field_cardinalities[field_name]) + ' values.'
                    print('Warning: ' + message + message_2)
                    logging.warning(message + message_2)


def validate_text_list_fields(config, field_definitions, csv_data):
    """For fields that are of "list_string" field type, check that values
       in CSV are in the field's "allowed_values" config setting.
    """
    # Temporary fix for https://github.com/mjordan/islandora_workbench/issues/443.
    if config['task'] == 'update':
        config['id_field'] = 'node_id'

    list_field_allowed_values = dict()
    csv_headers = csv_data.fieldnames
    for csv_header in csv_headers:
        if csv_header in field_definitions.keys():
            if 'allowed_values' in field_definitions[csv_header]:
                if field_definitions[csv_header]['allowed_values'] is not None:
                    list_field_allowed_values[csv_header] = field_definitions[csv_header]['allowed_values']

    for count, row in enumerate(csv_data, start=1):
        for field_name in list_field_allowed_values.keys():
            if field_name in row and len(row[field_name]) > 0:
                delimited_field_values = row[field_name].split(config['subdelimiter'])
                for field_value in delimited_field_values:
                    if field_name in list_field_allowed_values and field_value not in list_field_allowed_values[field_name]:
                        if config['task'] == 'create':
                            message = 'CSV field "' + field_name + '" in record with ID ' + \
                                row[config['id_field']] + ' contains a value ("' + field_value + '") that is not in the fields\'s allowed values.'
                        if config['task'] == 'update':
                            message = 'CSV field "' + field_name + '" in record with node ID ' + \
                                row[config['id_field']] + ' contains a value ("' + field_value + '") that is not in the fields\'s allowed values.'
                        print('Warning: ' + message)
                        logging.warning(message)


def validate_csv_field_length(config, field_definitions, csv_data):
    """Compare values in the CSV data with the fields' max_length. Log CSV
       fields that exceed their max_length, and warn user if
       these fields exist in their CSV data.
    """
    # Temporary fix for https://github.com/mjordan/islandora_workbench/issues/443.
    if config['task'] == 'update':
        config['id_field'] = 'node_id'

    field_max_lengths = dict()
    csv_headers = csv_data.fieldnames
    for csv_header in csv_headers:
        if csv_header in field_definitions.keys():
            if 'max_length' in field_definitions[csv_header]:
                max_length = field_definitions[csv_header]['max_length']
                # We don't care about max_length of None (i.e., it's not applicable or unlimited).
                if max_length is not None:
                    field_max_lengths[csv_header] = max_length

    for count, row in enumerate(csv_data, start=1):
        for field_name in field_max_lengths.keys():
            if field_name in row:
                delimited_field_values = row[field_name].split(config['subdelimiter'])
                for field_value in delimited_field_values:
                    field_value_length = len(field_value)
                    if field_name in field_max_lengths and len(field_value) > int(field_max_lengths[field_name]):
                        if config['task'] == 'create':
                            message = 'CSV field "' + field_name + '" in record with ID ' + \
                                row[config['id_field']] + ' contains a value that is longer (' + str(len(field_value)) + ' characters)'
                        if config['task'] == 'update':
                            message = 'CSV field "' + field_name + '" in record with node ID ' + \
                                row['node_id'] + ' contains a value that is longer (' + str(len(field_value)) + ' characters)'
                        message_2 = ' than allowed for that field (' + \
                            str(field_max_lengths[field_name]) + ' characters). Workbench will truncate this value prior to populating Drupal.'
                        print('Warning: ' + message + message_2)
                        logging.warning(message + message_2)


def validate_geolocation_fields(config, field_definitions, csv_data):
    """Validate lat,long values in fields that are of type 'geolocation'.
    """
    # Temporary fix for https://github.com/mjordan/islandora_workbench/issues/443.
    if config['task'] == 'update':
        config['id_field'] = 'node_id'

    geolocation_fields_present = False
    for count, row in enumerate(csv_data, start=1):
        for field_name in field_definitions.keys():
            if field_definitions[field_name]['field_type'] == 'geolocation':
                if field_name in row:
                    geolocation_fields_present = True
                    delimited_field_values = row[field_name].split(config['subdelimiter'])
                    for field_value in delimited_field_values:
                        if len(field_value.strip()):
                            if not validate_latlong_value(field_value.strip()):
                                message = 'Value in field "' + field_name + '" in row with ID ' + row[config['id_field']] + ' (' + field_value + ') is not a valid lat,long pair.'
                                logging.error(message)
                                sys.exit('Error: ' + message)

    if geolocation_fields_present is True:
        message = "OK, geolocation field values in the CSV file validate."
        print(message)
        logging.info(message)


def validate_link_fields(config, field_definitions, csv_data):
    """Validate values in fields that are of type 'link'.
    """
    # Temporary fix for https://github.com/mjordan/islandora_workbench/issues/443.
    if config['task'] == 'update':
        config['id_field'] = 'node_id'

    link_fields_present = False
    for count, row in enumerate(csv_data, start=1):
        for field_name in field_definitions.keys():
            if field_definitions[field_name]['field_type'] == 'link':
                if field_name in row:
                    link_fields_present = True
                    delimited_field_values = row[field_name].split(config['subdelimiter'])
                    for field_value in delimited_field_values:
                        if len(field_value.strip()):
                            if not validate_link_value(field_value.strip()):
                                message = 'Value in field "' + field_name + '" in row with ID ' + row[config['id_field']] + ' (' + field_value + ') is not a valid link field value.'
                                logging.error(message)
                                sys.exit('Error: ' + message)

    if link_fields_present is True:
        message = "OK, link field values in the CSV file validate."
        print(message)
        logging.info(message)


def validate_authority_link_fields(config, field_definitions, csv_data):
    """Validate values in fields that are of type 'authority_link'.
    """
    if config['task'] == 'create_terms':
        config['id_field'] = 'term_name'

    authority_link_fields_present = False
    for count, row in enumerate(csv_data, start=1):
        for field_name in field_definitions.keys():
            if field_definitions[field_name]['field_type'] == 'authority_link':
                if field_name in row:
                    authority_link_fields_present = True
                    delimited_field_values = row[field_name].split(config['subdelimiter'])
                    for field_value in delimited_field_values:
                        if len(field_value.strip()):
                            if not validate_authority_link_value(field_value.strip(), field_definitions[field_name]['authority_sources']):
                                message = 'Value in field "' + field_name + '" in row with ID "' + \
                                    row[config['id_field']] + '" (' + field_value + ') is not a valid authority link field value.'
                                logging.error(message)
                                sys.exit('Error: ' + message)

    if authority_link_fields_present is True:
        message = "OK, authority link field values in the CSV file validate."
        print(message)
        logging.info(message)


def validate_media_track_fields(config, csv_data):
    """Validate values in fields that are of type 'media_track'.
    """
    media_track_fields_present = False
    # Must accommodate multiple media track fields in the same CSV (e.g. audio and vidoe media in the
    # same CSV, each with its own track column). Therefore, we'll need to get the field definitions
    # for more than one media bundle.
    media_track_field_definitions = dict()
    csv_column_headers = copy.copy(csv_data.fieldnames)
    for column_header in csv_column_headers:
        if column_header.startswith('media:'):
            # Assumes well-formed column headers.
            media_bundle_name_parts = column_header.split(':')
            media_bundle_name = media_bundle_name_parts[1]
            if media_bundle_name not in config['media_track_file_fields']:
                message = 'Media type "' + media_bundle_name + '" in the CSV column header "' + column_header + \
                    '" is not registered in the "media_track_file_fields" configuration setting.'
                logging.error(message)
                sys.exit('Error: ' + message)

            media_track_field_definitions[media_bundle_name] = get_field_definitions(config, 'media', media_bundle_name)
            for count, row in enumerate(csv_data, start=1):
                for field_name in media_track_field_definitions[media_bundle_name].keys():
                    if media_track_field_definitions[media_bundle_name][field_name]['field_type'] == 'media_track':
                        fully_qualified_field_name = f"media:{media_bundle_name}:{field_name}"
                        if fully_qualified_field_name in row:
                            media_track_fields_present = True
                            delimited_field_values = row[fully_qualified_field_name].split(config['subdelimiter'])
                            for field_value in delimited_field_values:
                                if len(field_value.strip()):
                                    if validate_media_track_value(field_value) is False:
                                        message = 'Value in field "' + fully_qualified_field_name + '" in row with ID "' + \
                                            row[config['id_field']] + '" (' + field_value + ') has a media type is not a valid media track field value.'
                                        logging.error(message)
                                        sys.exit('Error: ' + message)

                                    # Confirm that the media bundle name in the column header matches the media type
                                    # of the file in the 'file' column.
                                    file_media_type = set_media_type(config, row['file'], 'file', row)
                                    if file_media_type != media_bundle_name:
                                        message = 'File named in the "file" field in row with ID "' + \
                                            row[config['id_field']] + '" (' + row['file'] + ') has a media type ' + \
                                            '(' + file_media_type + ') that differs from the media type indicated in the column header "' + \
                                            fully_qualified_field_name + '" (' + media_bundle_name + ').'
                                        logging.error(message)
                                        sys.exit('Error: ' + message)

                                # Confirm that config['media_use_tid'] and row-level media_use_term is for Service File (http://pcdm.org/use#ServiceFile).
                                if 'media_use_tid' in row:
                                    if row['media_use_tid'].startswith('http') and row['media_use_tid'] != 'http://pcdm.org/use#ServiceFile':
                                        message = f"{row['media_use_tid']} cannot be used as a \"media_use_tid\" value in your CSV when creating media tracks."
                                        logging.error(message)
                                        sys.exit('Error: ' + message)
                                    elif value_is_numeric(row['media_use_tid']):
                                        media_use_uri = get_term_uri(config, row['media_use_tid'])
                                        if media_use_uri != 'http://pcdm.org/use#ServiceFile':
                                            message = f"{row['media_use_tid']} cannot be used as a \"media_use_tid\" value in your CSV when creating media tracks."
                                            logging.error(message)
                                            sys.exit('Error: ' + message)
                                    else:
                                        # It's a term name.
                                        media_use_term_data = get_all_representations_of_term(config, vocab_id='islandora_media_use', name=row['media_use_tid'])
                                        if media_use_term_data['uri'] != 'http://pcdm.org/use#ServiceFile':
                                            message = f"{row['media_use_tid']} cannot be used as a \"media_use_tid\" in your CSV value when creating media tracks."
                                            logging.error(message)
                                            sys.exit('Error: ' + message)
                                else:
                                    media_use_term_data = get_all_representations_of_term(config, uri='http://pcdm.org/use#ServiceFile')
                                    if config['media_use_tid'] not in media_use_term_data.values():
                                        message = f"{config['media_use_tid']} cannot be used as a value in your configuaration's \"media_use_tid\" setting when creating media tracks."
                                        logging.error(message)
                                        sys.exit('Error: ' + message)

                                if config['nodes_only'] is False:
                                    if len(field_value.strip()):
                                        media_track_field_value_parts = field_value.split(':')
                                        media_track_file_path_in_csv = media_track_field_value_parts[3]
                                        if os.path.isabs(media_track_file_path_in_csv):
                                            media_track_file_path = media_track_file_path_in_csv
                                        else:
                                            media_track_file_path = os.path.join(config['input_dir'], media_track_file_path_in_csv)
                                        if not os.path.exists(media_track_file_path) or not os.path.isfile(media_track_file_path):
                                            message = 'Media track file "' + media_track_file_path_in_csv + '" in row with ID "' + \
                                                row[config['id_field']] + '" not found.'
                                            logging.error(message)
                                            sys.exit('Error: ' + message)

    if media_track_fields_present is True:
        message = "OK, media track field values in the CSV file validate."
        print(message)
        logging.info(message)


def validate_media_track_value(media_track_value):
    """Validates that the string in "media_track_value" has valid values in its subparts.
    """
    """Parameters
        ----------
        media_track_value : string
            The CSV value to validate.
        Returns
        -------
        boolean
            True if it does, False if not.
    """
    valid_kinds = ['subtitles', 'descriptions', 'metadata', 'captions', 'chapters']
    parts = media_track_value.split(':', 3)
    # First part, the label, needs to have a length; second part needs to be one of the
    # values in 'valid_kinds'; third part needs to be a valid Drupal language code; the fourth
    # part needs to end in '.vtt'.
    if len(parts) == 4 and len(parts[0]) > 0 and validate_language_code(parts[2]) and parts[1] in valid_kinds and parts[3].lower().endswith('.vtt'):
        return True
    else:
        return False


def validate_latlong_value(latlong):
    # Remove leading \ that may be present if input CSV is from a spreadsheet.
    latlong = latlong.lstrip('\\')
    if re.match(r"^[-+]?([1-8]?\d(\.\d+)?|90(\.0+)?),\s*[-+]?(180(\.0+)?|((1[0-7]\d)|([1-9]?\d))(\.\d+)?)$", latlong):
        return True
    else:
        return False


def validate_link_value(link_value):
    """Validates that the value in 'link_value' starts with either 'http://' or 'https://'
       and optionally contains the url/label delimiter '%%'.
    """
    """Parameters
        ----------
        link_value : string
            The URL.
        Returns
        -------
        boolean
            True if it does, False if not.
    """
    parts = link_value.split('%%', 1)
    if re.match(r"^https?://", parts[0]):
        return True
    else:
        return False


def validate_authority_link_value(authority_link_value, authority_sources):
    """Validates that the value in 'authority_link_value' has a 'source' and that the URI
       component starts with either 'http://' or 'https://'.
    """
    """Parameters
        ----------
        authority_link_value : string
            The authority link string, with a sourcea, URI, and optionally a title.
        authority_sources : list
            The list of authority sources (e.g. lcsh, cash, viaf, etc.) configured for the field.
        Returns
        -------
        boolean
            True if it does, False if not.
    """
    parts = authority_link_value.split('%%', 2)
    if parts[0] not in authority_sources:
        return False
    if re.match(r"^https?://", parts[1]):
        return True
    else:
        return False


def validate_term_name_length(term_name, row_number, column_name):
    """Checks that the length of a term name does not exceed
       Drupal's 255 character length.
    """
    term_name = term_name.strip()
    if len(term_name) > 255:
        message = 'CSV field "' + column_name + '" in record ' + row_number + \
            " contains a taxonomy term that exceeds Drupal's limit of 255 characters (length of term is " + str(len(term_name)) + ' characters).'
        message_2 = ' Term provided in CSV is "' + term_name + '".'
        message_3 = " Please reduce the term's length to less than 256 characters."
        logging.error(message + message_2 + message_3)
        sys.exit('Error: ' + message + ' See the Workbench log for more information.')


def validate_node_created_date(csv_data):
    """Checks that date_string is in the format used by Drupal's 'created' node property,
       e.g., 2020-11-15T23:49:22+00:00. Also check to see if the date is in the future.
    """
    # Temporary fix for https://github.com/mjordan/islandora_workbench/issues/443.
    if config['task'] == 'update':
        config['id_field'] = 'node_id'

    for count, row in enumerate(csv_data, start=1):
        for field_name, field_value in row.items():
            if field_name == 'created' and len(field_value) > 0:
                # matches = re.match(r'^\d{4}-\d\d-\d\dT\d\d:\d\d:\d\d[+-]\d\d:\d\d$', field_value)
                if not validate_node_created_date_string(field_value):
                    message = 'CSV field "created" in record with ID ' + \
                        row[config['id_field']] + ' contains a date "' + field_value + '" that is not formatted properly.'
                    logging.error(message)
                    sys.exit('Error: ' + message)

                now = datetime.datetime.now()
                # Remove the GMT differential at the end of the time string.
                date_string_trimmed = re.sub(
                    r'[+-]\d\d:\d\d$', '', field_value)
                created_date = datetime.datetime.strptime(date_string_trimmed, '%Y-%m-%dT%H:%M:%S')
                if created_date > now:
                    message = 'CSV field "created" in record with ID ' + \
                        row[config['id_field']] + ' contains a date "' + field_value + '" that is in the future.'
                    logging.error(message)
                    sys.exit('Error: ' + message)

    message = 'OK, dates in the "created" CSV field are all formated correctly and in the future.'
    print(message)
    logging.info(message)


def validate_node_created_date_string(created_date_string):
    if re.match(r"^\d{4}-\d\d-\d\dT\d\d:\d\d:\d\d[+-]\d\d:\d\d$", created_date_string):
        return True
    else:
        return False


def validate_edtf_fields(config, field_definitions, csv_data):
    """Validate values in fields that are of type 'edtf'.
    """
    # Temporary fix for https://github.com/mjordan/islandora_workbench/issues/443.
    if config['task'] == 'update':
        config['id_field'] = 'node_id'
    edtf_fields_present = False
    for count, row in enumerate(csv_data, start=1):
        for field_name in field_definitions.keys():
            if field_definitions[field_name]['field_type'] == 'edtf':
                if field_name in row:
                    edtf_fields_present = True
                    delimited_field_values = row[field_name].split(config['subdelimiter'])
                    for field_value in delimited_field_values:
                        if len(field_value.strip()):
                            valid = validate_edtf_date(field_value)
                            if valid is False:
                                message = 'Value in field "' + field_name + '" in row with ID ' + row[config['id_field']] + ' ("' + field_value + '") is not a valid EDTF date/time.'
                                logging.error(message)
                                sys.exit('Error: ' + message)

    if edtf_fields_present is True:
        message = "OK, EDTF field values in the CSV file validate."
        print(message)
        logging.info(message)


def validate_edtf_date(date):
    valid = edtf_validate.valid_edtf.is_valid(date.strip())
    return valid


def validate_url_aliases(config, csv_data):
    """Checks that URL aliases don't already exist.
    """
    for count, row in enumerate(csv_data, start=1):
        for field_name, field_value in row.items():
            if field_name == 'url_alias' and len(field_value) > 0:
                if field_value.strip()[0] != '/':
                    message = 'CSV field "url_alias" in record with ID ' + \
                        row[config['id_field']] + ' contains an alias "' + field_value + '" that is missing its leading /.'
                    logging.error(message)
                    sys.exit('Error: ' + message)

                alias_ping = ping_url_alias(config, field_value)
                # @todo: Add 301 and 302 as acceptable status codes?
                if alias_ping == 200:
                    message = 'CSV field "url_alias" in record with ID ' + \
                        row[config['id_field']] + ' contains an alias "' + field_value + '" that already exists.'
                    logging.error(message)
                    sys.exit('Error: ' + message)

    message = 'OK, URL aliases do not already exist.'
    print(message)
    logging.info(message)


def validate_node_uid(config, csv_data):
    """Checks that the user identified in the 'uid' field exists in Drupal. Note that
       this does not validate any permissions the user may have.
    """
    for count, row in enumerate(csv_data, start=1):
        for field_name, field_value in row.items():
            if field_name == 'uid' and len(field_value) > 0:
                # Request to /user/x?_format=json goes here; 200 means the user
                # exists, 404 means they do no.
                uid_url = config['host'] + '/user/' + str(field_value) + '?_format=json'
                uid_response = issue_request(config, 'GET', uid_url)
                if uid_response.status_code == 404:
                    message = 'CSV field "uid" in record with ID ' + \
                        row[config['id_field']] + ' contains a user ID "' + field_value + '" that does not exist in the target Drupal.'
                    logging.error(message)
                    sys.exit('Error: ' + message)

    message = 'OK, user IDs in the "uid" CSV field all exist.'
    print(message)
    logging.info(message)


def validate_taxonomy_field_values(config, field_definitions, csv_data):
    """Loop through all fields in field_definitions, and if a field
       is a taxonomy reference field, validate all values in the CSV
       data in that field against term IDs in the taxonomies referenced
       by the field. Does not validate Typed Relation fields
       (see validate_typed_relation_field_values()).
    """
    # Define a list to store names of CSV fields that reference vocabularies.
    fields_with_vocabularies = list()
    vocab_validation_issues = False
    # Get all the term IDs for vocabularies referenced in all fields in the CSV.
    for column_name in csv_data.fieldnames:
        if column_name in field_definitions:
            if field_definitions[column_name]['field_type'] == 'typed_relation':
                continue
            if 'vocabularies' in field_definitions[column_name]:
                vocabularies = get_field_vocabularies(config, field_definitions, column_name)
                # If there are no vocabularies linked to the current field, 'vocabularies'
                # will be False and will throw a TypeError.
                try:
                    num_vocabs = len(vocabularies)
                    if num_vocabs > 0:
                        fields_with_vocabularies.append(column_name)
                except BaseException:
                    message = 'Workbench cannot get vocabularies linked to field "' + column_name + '". Please confirm that field has at least one vocabulary.'
                    logging.error(message)
                    sys.exit('Error: ' + message)

    # If none of the CSV fields are taxonomy reference fields, return.
    if len(fields_with_vocabularies) == 0:
        return

    # Iterate through the CSV and validate each taxonomy fields's values.
    new_term_names_in_csv_results = []
    for count, row in enumerate(csv_data, start=1):
        for column_name in fields_with_vocabularies:
            if len(row[column_name]):
                new_term_names_in_csv = validate_taxonomy_reference_value(config, field_definitions, column_name, row[column_name], count)
                new_term_names_in_csv_results.append(new_term_names_in_csv)

    if True in new_term_names_in_csv_results and config['allow_adding_terms'] is True:
        if config['validate_terms_exist'] is True:
            print("OK, term IDs/names in CSV file exist in their respective taxonomies (and new terms will be created as noted in the Workbench log).")
        else:
            print("Skipping check for existence of terms (but new terms will be created as noted in the Workbench log).")
            logging.warning("Skipping check for existence of terms (but new terms will be created).")
    else:
        # All term IDs are in their field's vocabularies.
        print("OK, term IDs/names in CSV file exist in their respective taxonomies.")
        logging.info("OK, term IDs/names in CSV file exist in their respective taxonomies.")

    return vocab_validation_issues


def validate_vocabulary_fields_in_csv(config, vocabulary_id, vocab_csv_file_path):
    """Loop through all fields in CSV to ensure that all present fields match field
       from the vocab's field definitions, and that any required fields are present.
       Also checks that each row has the same number of columns as there are headers.
    """
    """Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        vocabulary_id : string
            The ID of the vocabulary to validate.
        vocab_csv_file_path: string
            Location of vocabulary CSV file.
    """
    csv_data = get_csv_data(config, 'taxonomy_fields', vocab_csv_file_path)
    csv_column_headers = copy.copy(csv_data.fieldnames)

    # Check whether each row contains the same number of columns as there are headers.
    row_count = 0
    for count, row in enumerate(csv_data, start=1):
        extra_headers = False
        field_count = 0
        row_count += 1
        for field in row:
            # 'stringtopopulateextrafields' is added by get_csv_data() if there are extra headers.
            if row[field] == 'stringtopopulateextrafields':
                extra_headers = True
            else:
                field_count += 1
        if extra_headers is True:
            message = "Row with ID " + row[config['id_field']] + ') of the vocabulary CSV file "' + \
                vocab_csv_file_path + '" has fewer columns than there are headers (' + str(len(csv_column_headers)) + ")."
            logging.error(message)
            sys.exit('Error: ' + message)
        # Note: this message is also generated in get_csv_data() since CSV Writer thows an exception if the row has
        # form fields than headers.
        if len(csv_column_headers) < field_count:
            message = "Row with term name '" + row['term_name'] + ') of the vocabulary CSV file "' + vocab_csv_file_path + \
                '" has more columns (' + str(field_count) + ") than there are headers (" + str(len(csv_column_headers)) + ")."
            logging.error(message)
            sys.exit('Error: ' + message)
    message = "OK, all " \
        + str(row_count) + ' rows in the vocabulary CSV file "' + vocab_csv_file_path + '" have the same number of columns as there are headers (' \
        + str(len(csv_column_headers)) + ').'
    print(message)
    logging.info(message)

    # Check that the required 'term_name' and 'parent' columns are present in the CSV, and that
    # any fields defined as required in the vocabulary are also present.
    field_definitions = get_field_definitions(config, 'taxonomy_term', vocabulary_id.strip())
    for column_name in csv_column_headers:
        # Check that 'term_name' and 'parent' are in the CSV.
        if 'term_name' not in csv_column_headers:
            message = 'Required column "term_name" not found in vocabulary CSV file "' + vocab_csv_file_path + '".'
            logging.error(message)
            sys.exit('Error: ' + message)
        if 'parent' not in csv_column_headers:
            message = 'Required column "parent" not found in vocabulary CSV file "' + vocab_csv_file_path + '".'
            logging.error(message)
            sys.exit('Error: ' + message)
        # Then vocabulary fields that are defined as required.
        field_definition_fieldnames = field_definitions.keys()
        for field in field_definition_fieldnames:
            if field_definitions[field]['required'] is True and field not in csv_data.fieldnames:
                message = 'Required column "' + field + '" not found in vocabulary CSV file "' + vocab_csv_file_path + '".'
                logging.error(message)
                sys.exit('Error: ' + message)

    # Check whether remaining fields in the vocabulary CSV are fields defined in the current vocabulary.
    if 'field_name' in csv_column_headers:
        csv_column_headers.remove('field_name')
    if 'parent' in csv_column_headers:
        csv_column_headers.remove('parent')
    for csv_field in csv_column_headers:
        if csv_field not in field_definitions.keys():
            message = 'CSV column "' + csv_field + '" in vocabulary CSV file "' + vocab_csv_file_path + '" is not a field in the "' + vocabulary_id + '" vocabulary.'
            logging.error(message)
            sys.exit('Error: ' + message)


def validate_typed_relation_field_values(config, field_definitions, csv_data):
    """Validate values in fields that are of type 'typed_relation'. Each CSV
       value must have this pattern: "string:string:int" or "string:string:string".
       If the last segment is a string, it must be term name, a namespaced term name,
       or an http URI.
    """
    # Temporary fix for https://github.com/mjordan/islandora_workbench/issues/443.
    if config['task'] == 'update':
        config['id_field'] = 'node_id'

    # Define a list to store CSV field names that contain vocabularies.
    fields_with_vocabularies = list()
    # Get all the term IDs for vocabularies referenced in all fields in the CSV.
    vocab_validation_issues = False
    for column_name in csv_data.fieldnames:
        if column_name in field_definitions:
            if 'vocabularies' in field_definitions[column_name]:
                vocabularies = get_field_vocabularies(config, field_definitions, column_name)
                # If there are no vocabularies linked to the current field, 'vocabularies'
                # will be False and will throw a TypeError.
                try:
                    num_vocabs = len(vocabularies)
                    if num_vocabs > 0:
                        fields_with_vocabularies.append(column_name)
                except BaseException:
                    message = 'Workbench cannot get vocabularies linked to field "' + column_name + '". Please confirm that field has at least one vocabulary.'
                    logging.error(message)
                    sys.exit('Error: ' + message)
                all_tids_for_field = []

    # If none of the CSV fields are taxonomy reference fields, return.
    if len(fields_with_vocabularies) == 0:
        return

    typed_relation_fields_present = False
    new_term_names_in_csv_results = []
    for count, row in enumerate(csv_data, start=1):
        for field_name in field_definitions.keys():
            if field_definitions[field_name]['field_type'] == 'typed_relation' and 'typed_relations' in field_definitions[field_name]:
                if field_name in row:
                    typed_relation_fields_present = True
                    delimited_field_values = row[field_name].split(config['subdelimiter'])
                    for field_value in delimited_field_values:
                        if len(field_value) == 0:
                            continue
                        # First check the required patterns.
                        if not re.match("^[a-zA-Z]+:[a-zA-Z]+:.+$", field_value.strip()):
                            message = 'Value in field "' + field_name + '" in row with ID ' + row[config['id_field']] + \
                                ' (' + field_value + ') does not use the pattern required for typed relation fields.'
                            logging.error(message)
                            sys.exit('Error: ' + message)

                        # Then, check to see if the relator string (the first two parts of the
                        # value) exist in the field_definitions[fieldname]['typed_relations'] list.
                        typed_relation_value_parts = field_value.split(':', 2)
                        relator_string = typed_relation_value_parts[0] + ':' + typed_relation_value_parts[1]
                        if relator_string not in field_definitions[field_name]['typed_relations']:
                            message = 'Value in field "' + field_name + '" in row with ID ' + row[config['id_field']] + \
                                ' contains a relator (' + relator_string + ') that is not configured for that field.'
                            logging.error(message)
                            sys.exit('Error: ' + message)

                    # Iterate through the CSV and validate the taxonomy term/name/URI in each field subvalue.
                    for column_name in fields_with_vocabularies:
                        if len(row[column_name]):
                            delimited_field_values = row[column_name].split(config['subdelimiter'])
                            delimited_field_values_without_relator_strings = []
                            for field_value in delimited_field_values:
                                # Strip the relator string out from field_value, leaving the vocabulary ID and term ID/name/URI.
                                term_to_check = re.sub('^[a-zA-Z]+:[a-zA-Z]+:', '', field_value)
                                delimited_field_values_without_relator_strings.append(term_to_check)

                            field_value_to_check = config['subdelimiter'].join(delimited_field_values_without_relator_strings)
                            new_term_names_in_csv = validate_taxonomy_reference_value(config, field_definitions, column_name, field_value_to_check, count)
                            new_term_names_in_csv_results.append(new_term_names_in_csv)

    if typed_relation_fields_present is True and True in new_term_names_in_csv_results and config['allow_adding_terms'] is True:
        print("OK, term IDs/names used in typed relation fields in the CSV file exist in their respective taxonomies (and new terms will be created as noted in the Workbench log).")
    else:
        if typed_relation_fields_present is True:
            # All term IDs are in their field's vocabularies.
            print("OK, term IDs/names used in typed relation fields in the CSV file exist in their respective taxonomies.")
            logging.info("OK, term IDs/names used in typed relation fields in the CSV file exist in their respective taxonomies.")

    return vocab_validation_issues


def validate_taxonomy_reference_value(config, field_definitions, csv_field_name, csv_field_value, record_number):
    this_fields_vocabularies = get_field_vocabularies(config, field_definitions, csv_field_name)
    this_fields_vocabularies_string = ', '.join(this_fields_vocabularies)

    new_term_names_in_csv = False

    # Allow for multiple values in one field.
    terms_to_check = csv_field_value.split(config['subdelimiter'])
    for field_value in terms_to_check:
        # If this is a multi-taxonomy field, all term names (not IDs or URIs) must be namespaced using the vocab_id:term_name pattern,
        # regardless of whether config['allow_adding_terms'] is True. Also, we need to accommodate terms that are namespaced
        # and also contain a ':'.
        if len(this_fields_vocabularies) > 1 and value_is_numeric(field_value) is False and not field_value.startswith('http'):
            split_field_values = field_value.split(config['subdelimiter'])
            for split_field_value in split_field_values:
                if ':' in field_value:
                    # If the : is present, validate that the namespace is one of the vocabulary IDs referenced by this field.
                    [tentative_namespace, tentative_term_name] = field_value.split(':', 1)
                    if tentative_namespace not in this_fields_vocabularies:
                        message = 'Vocabulary ID "' + tentative_namespace + '" used in CSV column "' + csv_field_name + '", row ' + str(record_number) + \
                            ' does not match any of the vocabularies referenced by the' + ' corresponding Drupal field (' + this_fields_vocabularies_string + ').'
                        logging.error(message)
                        sys.exit('Error: ' + message)
                else:
                    message = 'Term names in CSV field "' + csv_field_name + '" require a vocabulary namespace; CSV value '
                    message_2 = '"' + field_value + '" in row ' + str(record_number) + ' does not have one.'
                    logging.error(message + message_2)
                    sys.exit('Error: ' + message + message_2)

                validate_term_name_length(split_field_value, str(record_number), csv_field_name)

        # Check to see if field_value is a member of the field's vocabularies. First, check whether field_value is a term ID.
        if value_is_numeric(field_value):
            field_value = field_value.strip()
            term_in_vocabs = False
            for vocab_id in this_fields_vocabularies:
                term_vocab = get_term_vocab(config, field_value)
                if term_vocab == vocab_id:
                    term_in_vocabs = True
            if term_in_vocabs is False:
                message = 'CSV field "' + csv_field_name + '" in row ' + str(record_number) + ' contains a term ID (' + field_value + ') that is '
                if len(this_fields_vocabularies) > 1:
                    message_2 = 'not in one of the referenced vocabularies (' + \
                        this_fields_vocabularies_string + ').'
                else:
                    message_2 = 'not in the referenced vocabulary ("' + \
                        this_fields_vocabularies[0] + '").'
                logging.error(message + message_2)
                sys.exit('Error: ' + message + message_2)
        # Then check values that are URIs.
        elif field_value.strip().startswith('http'):
            field_value = field_value.strip()
            tid_from_uri = get_term_id_from_uri(config, field_value)
            if value_is_numeric(tid_from_uri):
                term_vocab = get_term_vocab(config, tid_from_uri)
                term_in_vocabs = False
                for vocab_id in this_fields_vocabularies:
                    if term_vocab == vocab_id:
                        term_in_vocabs = True
                if term_in_vocabs is False:
                    message = 'CSV field "' + csv_field_name + '" in row ' + str(record_number) + ' contains a term URI (' + field_value + ') that is '
                    if len(this_fields_vocabularies) > 1:
                        message_2 = 'not in one of the referenced vocabularies (' + this_fields_vocabularies_string + ').'
                    else:
                        message_2 = 'not in the referenced vocabulary ("' + this_fields_vocabularies[0] + '").'
                    logging.error(message + message_2)
                    sys.exit('Error: ' + message + message_2)
            else:
                message = 'Term URI "' + field_value + '" used in CSV column "' + csv_field_name + '" row ' + str(record_number) + ' does not match any terms.'
                logging.error(message)
                sys.exit('Error: ' + message)
        # Finally, check values that are string term names.
        else:
            new_terms_to_add = []
            for vocabulary in this_fields_vocabularies:
                tid = find_term_in_vocab(config, vocabulary, field_value)
                if value_is_numeric(tid) is False:
                    # Single taxonomy fields.
                    if len(this_fields_vocabularies) == 1:
                        if config['allow_adding_terms'] is True:
                            # Warn if namespaced term name is not in specified vocab.
                            if tid is False:
                                new_term_names_in_csv = True
                                validate_term_name_length(field_value, str(record_number), csv_field_name)
                                message = 'CSV field "' + csv_field_name + '" in row ' + str(record_number) + ' contains a term ("' + field_value.strip() + '") that is '
                                message_2 = 'not in the referenced vocabulary ("' + this_fields_vocabularies[0] + '"). That term will be created.'
                                if config['validate_terms_exist'] is True:
                                    logging.warning(message + message_2)
                        else:
                            new_term_names_in_csv = True
                            message = 'CSV field "' + csv_field_name + '" in row ' + \
                                str(record_number) + ' contains a term ("' + field_value.strip() + '") that is '
                            message_2 = 'not in the referenced vocabulary ("' + this_fields_vocabularies[0] + '").'
                            logging.error(message + message_2)
                            sys.exit('Error: ' + message + message_2)

                # If this is a multi-taxonomy field, all term names must be namespaced using the vocab_id:term_name pattern,
                # regardless of whether config['allow_adding_terms'] is True.
                if len(this_fields_vocabularies) > 1:
                    split_field_values = field_value.split(config['subdelimiter'])
                    for split_field_value in split_field_values:
                        # Check to see if the namespaced vocab is referenced by this field.
                        [namespace_vocab_id, namespaced_term_name] = split_field_value.split(':', 1)
                        if namespace_vocab_id not in this_fields_vocabularies:
                            message = 'CSV field "' + csv_field_name + '" in row ' + str(record_number) + ' contains a namespaced term name '
                            message_2 = '("' + namespaced_term_name.strip() + '") that specifies a vocabulary not associated with that field (' + namespace_vocab_id + ').'
                            logging.error(message + message_2)
                            sys.exit('Error: ' + message + message_2)

                        tid = find_term_in_vocab(config, namespace_vocab_id, namespaced_term_name)

                        # Warn if namespaced term name is not in specified vocab.
                        if config['allow_adding_terms'] is True:
                            if tid is False and split_field_value not in new_terms_to_add:
                                new_term_names_in_csv = True
                                message = 'CSV field "' + csv_field_name + '" in row ' + str(record_number) + ' contains a term ("' + namespaced_term_name.strip() + '") that is '
                                message_2 = 'not in the referenced vocabulary ("' + namespace_vocab_id + '"). That term will be created.'
                                if config['validate_terms_exist'] is True:
                                    logging.warning(message + message_2)
                                new_terms_to_add.append(split_field_value)

                                validate_term_name_length(split_field_value, str(record_number), csv_field_name)
                        # Die if namespaced term name is not specified vocab.
                        else:
                            if tid is False:
                                message = 'CSV field "' + csv_field_name + '" in row ' + str(record_number) + ' contains a term ("' + namespaced_term_name.strip() + '") that is '
                                message_2 = 'not in the referenced vocabulary ("' + namespace_vocab_id + '").'
                                logging.warning(message + message_2)
                                sys.exit('Error: ' + message + message_2)

    return new_term_names_in_csv


def write_to_output_csv(config, id, node_json, input_csv_row=None):
    """Appends a row to the CVS file located at config['output_csv'].
    """
    if config['task'] == 'create_from_files':
        config['id_field'] = 'ID'

    node_dict = json.loads(node_json)
    node_field_names = list(node_dict.keys())
    node_field_names.insert(0, 'node_id')
    node_field_names.insert(0, config['id_field'])
    # Don't include these Drupal fields in our output.
    fields_to_remove = [
        'nid',
        'vid',
        'created',
        'changed',
        'langcode',
        'default_langcode',
        'uid',
        'type',
        'revision_timestamp',
        'revision_translation_affected',
        'revision_uid',
        'revision_log',
        'content_translation_source',
        'content_translation_outdated']
    for field_to_remove in fields_to_remove:
        node_field_names.remove(field_to_remove)

    csvfile = open(config['output_csv'], 'a+', encoding='utf-8')

    if input_csv_row is not None and config['output_csv_include_input_csv'] is True:
        # Remove fields from the input CSV that would overwrite field data from the new node.
        input_csv_row_fieldnames = list(input_csv_row.keys())
        if 'title' in input_csv_row:
            input_csv_row_fieldnames.remove('title')
        if 'status' in input_csv_row:
            input_csv_row_fieldnames.remove('status')
        node_field_names.extend(input_csv_row_fieldnames)

    writer = csv.DictWriter(csvfile, fieldnames=node_field_names, lineterminator="\n")

    # Check for presence of header row, don't add it if it's already there.
    with open(config['output_csv']) as f:
        first_line = f.readline()
    if not first_line.startswith(config['id_field']):
        writer.writeheader()

    # Assemble the CSV record to write.
    row = dict()
    row[config['id_field']] = id
    row['node_id'] = node_dict['nid'][0]['value']
    row['uuid'] = node_dict['uuid'][0]['value']
    row['title'] = node_dict['title'][0]['value']
    row['status'] = node_dict['status'][0]['value']
    if input_csv_row is not None and config['output_csv_include_input_csv'] is True:
        # Remove columns from the input CSV that would overwrite field data from the new node.
        if 'title' in input_csv_row:
            del input_csv_row['title']
        if 'status' in input_csv_row:
            del input_csv_row['status']
        # Then append the input row to the new node data.
        row.update(input_csv_row)
    writer.writerow(row)
    csvfile.close()


def create_children_from_directory(config, parent_csv_record, parent_node_id, parent_title):
    drupal_8 = set_drupal_8(config)

    path_to_rollback_csv_file = get_rollback_csv_filepath(config)

    # These objects will have a title (derived from filename), an ID based on the parent's
    # id, and a config-defined Islandora model. Content type and status are inherited
    # as is from parent. The weight assigned to the page is the last segment in the filename,
    # split from the rest of the filename using the character defined in the
    # 'paged_content_sequence_separator' config option.
    parent_id = parent_csv_record[config['id_field']]
    page_dir_path = os.path.join(config['input_dir'], parent_id)
    page_files = os.listdir(page_dir_path)
    page_file_return_dict = dict()
    for page_file_name in page_files:
        filename_without_extension = os.path.splitext(page_file_name)[0]
        filename_segments = filename_without_extension.split(config['paged_content_sequence_separator'])
        weight = filename_segments[-1]
        weight = weight.lstrip("0")
        # @todo: come up with a templated way to generate the page_identifier,
        # and what field to POST it to.
        page_identifier = parent_id + '_' + filename_without_extension
        page_title = parent_title + ', page ' + weight

        node_json = {
            'type': [
                {'target_id': config['paged_content_page_content_type'],
                 'target_type': 'node_type'}
            ],
            'title': [
                {'value': page_title}
            ],
            'status': [
                {'value': config['published']}
            ],
            'field_member_of': [
                {'target_id': parent_node_id,
                 'target_type': 'node'}
            ],
            'field_weight': [
                {'value': weight}
            ]
        }

        # Add field_model if that field exists in the child's content type.
        entity_fields = get_entity_fields(config, 'node', config['paged_content_page_content_type'])
        if 'field_model' in entity_fields:
            node_json['field_model'] = [{'target_id': config['paged_content_page_model_tid'], 'target_type': 'taxonomy_term'}]

        if 'field_display_hints' in parent_csv_record:
            node_json['field_display_hints'] = [{'target_id': parent_csv_record['field_display_hints'], 'target_type': 'taxonomy_term'}]

        # Some optional base fields, inherited from the parent object.
        if 'uid' in parent_csv_record:
            if len(parent_csv_record['uid']) > 0:
                node_json['uid'] = [{'target_id': parent_csv_record['uid']}]

        if 'created' in parent_csv_record:
            if len(parent_csv_record['created']) > 0:
                node_json['created'] = [{'value': parent_csv_record['created']}]

        node_headers = {
            'Content-Type': 'application/json'
        }
        node_endpoint = '/node?_format=json'
        node_response = issue_request(config, 'POST', node_endpoint, node_headers, node_json, None)
        if node_response.status_code == 201:
            node_uri = node_response.headers['location']
            print('+ Node for child "' + page_title + '" created at ' + node_uri + '.')
            logging.info('Node for child "%s" created at %s.', page_title, node_uri)
            if 'output_csv' in config.keys():
                write_to_output_csv(config, page_identifier, node_response.text)

            node_nid = node_uri.rsplit('/', 1)[-1]
            write_rollback_node_id(config, node_nid, path_to_rollback_csv_file)

            page_file_path = os.path.join(parent_id, page_file_name)
            fake_csv_record = collections.OrderedDict()
            fake_csv_record['title'] = page_title
            fake_csv_record['file'] = page_file_path
            if drupal_8 is True:
                media_response_status_code = create_islandora_media(config, page_file_path, 'file', node_uri, fake_csv_record)
            else:
                media_response_status_code = create_media(config, page_file_path, 'file', node_nid, fake_csv_record)
            allowed_media_response_codes = [201, 204]
            if media_response_status_code in allowed_media_response_codes:
                if media_response_status_code is False:
                    logging.info("Media for %s not created.", page_file_path)
                    continue
                else:
                    logging.info("Media for %s created.", page_file_path)
        else:
            logging.warning('Node for page "%s" not created, HTTP response code was %s.', page_identifier, node_response.status_code)

        # Execute node-specific post-create scripts, if any are configured.
        if 'node_post_create' in config and len(config['node_post_create']) > 0:
            for command in config['node_post_create']:
                post_task_output, post_task_return_code = execute_entity_post_task_script(command, args.config, node_response.status_code, node_response.text)
                if post_task_return_code == 0:
                    logging.info("Post node create script " + command + " executed successfully.")
                else:
                    logging.error("Post node create script " + command + " failed with exit code " + str(post_task_return_code) + ".")


def get_rollback_csv_filepath(config):
    if config['timestamp_rollback'] is True:
        now_string = EXECUTION_START_TIME.strftime("%Y_%m_%d_%H_%M_%S")
        rollback_csv_filename = 'rollback.' + now_string + '.csv'
    else:
        rollback_csv_filename = 'rollback.csv'
    return os.path.join(config['input_dir'], rollback_csv_filename)


def write_rollback_config(config, path_to_rollback_csv_file):
    if config['timestamp_rollback'] is True:
        now_string = EXECUTION_START_TIME.strftime("%Y_%m_%d_%H_%M_%S")
        rollback_config_filename = 'rollback.' + now_string + '.yml'
    else:
        rollback_config_filename = 'rollback.yml'

    rollback_config_file = open(rollback_config_filename, "w")

    yaml.dump(
        {'task': 'delete',
            'host': config['host'],
            'username': config['username'],
            'password': config['password'],
            'input_dir': config['input_dir'],
            'input_csv': os.path.basename(path_to_rollback_csv_file)},
        rollback_config_file)


def prep_rollback_csv(config, path_to_rollback_csv_file):
    path_to_rollback_csv_file = get_rollback_csv_filepath(config)
    if os.path.exists(path_to_rollback_csv_file):
        os.remove(path_to_rollback_csv_file)
    rollback_csv_file = open(path_to_rollback_csv_file, "a+")
    rollback_csv_file.write("node_id" + "\n")
    rollback_csv_file.close()


def write_rollback_node_id(config, node_id, path_to_rollback_csv_file):
    path_to_rollback_csv_file = get_rollback_csv_filepath(config)
    rollback_csv_file = open(path_to_rollback_csv_file, "a+")
    rollback_csv_file.write(node_id + "\n")
    rollback_csv_file.close()


def get_csv_from_google_sheet(config):
    url_parts = config['input_csv'].split('/')
    url_parts[6] = 'export?gid=' + str(config['google_sheets_gid']) + '&format=csv'
    csv_url = '/'.join(url_parts)
    response = requests.get(url=csv_url, allow_redirects=True)

    if response.status_code == 404:
        message = 'Workbench cannot find the Google spreadsheet at ' + config['input_csv'] + '. Please check the URL.'
        logging.error(message)
        sys.exit('Error: ' + message)

    # Sheets that aren't publicly readable return a 302 and then a 200 with a bunch of HTML for humans to look at.
    if response.content.strip().startswith(b'<!DOCTYPE'):
        message = 'The Google spreadsheet at ' + config['input_csv'] + ' is not accessible.\nPlease check its "Share" settings.'
        logging.error(message)
        sys.exit('Error: ' + message)

    input_csv_path = os.path.join(config['input_dir'], config['google_sheets_csv_filename'])
    open(input_csv_path, 'wb+').write(response.content)


def get_csv_from_excel(config):
    """Read the input Excel 2010 (or later) file and write it out as CSV.
    """
    if os.path.isabs(config['input_csv']):
        input_excel_path = config['input_csv']
    else:
        input_excel_path = os.path.join(config['input_dir'], config['input_csv'])

    if not os.path.exists(input_excel_path):
        message = 'Error: Excel file ' + input_excel_path + ' not found.'
        logging.error(message)
        sys.exit(message)

    excel_file_path = config['input_csv']
    wb = openpyxl.load_workbook(filename=input_excel_path)
    ws = wb[config['excel_worksheet']]

    headers = []
    header_row = ws[1]
    ws.delete_rows(0)
    for header_cell in header_row:
        headers.append(header_cell.value)

    records = []
    for row in ws:
        record = {}
        for x in range(len(header_row)):
            if headers[x] is not None and row[x] is not None:
                record[headers[x]] = row[x].value
        records.append(record)

    input_csv_path = os.path.join(config['input_dir'], config['excel_csv_filename'])
    csv_writer_file_handle = open(input_csv_path, 'w+', newline='', encoding='utf-8')
    csv_writer = csv.DictWriter(csv_writer_file_handle, fieldnames=headers)
    csv_writer.writeheader()
    for record in records:
        if (config['id_field'] in record or 'node_id' in record) and record[config['id_field']] is not None:
            csv_writer.writerow(record)
    csv_writer_file_handle.close()


def get_extension_from_mimetype(mimetype):
    # mimetypes.add_type() is not working, e.g. mimetypes.add_type('image/jpeg', '.jpg')
    # Maybe related to https://bugs.python.org/issue4963? In the meantime, provide our own
    # MIMETYPE to extension mapping for common types, then let mimetypes guess at others.
    map = {'image/jpeg': '.jpg',
           'image/jp2': '.jp2',
           'image/png': '.png',
           'audio/mpeg': '.mp3',
           'text/plain': '.txt',
           'application/octet-stream': '.bin'
           }
    if mimetype in map:
        return map[mimetype]
    else:
        return mimetypes.guess_extension(mimetype)


def get_deduped_file_path(path):
    """Given a file path, return a version of it that contains a version of
       the same name with an incremented integer inserted before the extension.
    """
    """Parameters
        ----------
        path : string
            The file path we want to dedupe.
        Returns
        -------
        string
            The deduped version of 'path', i.e., the original path with an
            underscore and an incremented digit inserted before the extension.
    """
    [base_path, extension] = os.path.splitext(path)

    numbers = re.findall(r"_\d+$", base_path)
    if len(numbers) == 0:
        incremented_path = base_path + '_1' + extension
    else:
        number = int(numbers[0].lstrip('_')) + 1
        base_path_parts = base_path.split('_')
        del base_path_parts[-1]
        incremented_path = '_'.join(base_path_parts) + '_' + str(number) + extension

    return incremented_path


def check_file_exists(config, filename):
    """Cconfirms file exists and is a file (not a directory).
       For remote/downloaded files, checks for a 200 response from a HEAD request.
    """
    """Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        filename: string
            The filename.
        Returns
        -------
        boolean
            True if the file exists, false if not.
    """
    # It's a remote file.
    if filename.startswith('http'):
        try:
            head_response = requests.head(filename, allow_redirects=True, verify=config['secure_ssl_only'])
            if head_response.status_code == 200:
                return True
            else:
                return False
        except requests.exceptions.Timeout as err_timeout:
            message = 'Workbench timed out trying to reach ' + filename + '. Details in next log entry.'
            logging.error(message)
            logging.error(err_timeout)
            return False
        except requests.exceptions.ConnectionError as error_connection:
            message = 'Workbench cannot connect to ' + filename + '. Details in next log entry.'
            logging.error(message)
            logging.error(error_connection)
            return False
    # It's a local file.
    else:
        if os.path.isabs(filename):
            file_path = filename
        else:
            file_path = os.path.join(config['input_dir'], filename)

        if os.path.exists(file_path) and os.path.isfile(file_path):
            return True


def get_preprocessed_file_path(config, file_fieldname, node_csv_row, node_id=None, make_dir=True):
    """For remote/downloaded files (other than from providers defined in config['oembed_providers]),
       generates the path to the local temporary copy and returns that path. For local files or oEmbed URLs,
       just returns the value of node_csv_row['file'].
    """
    """Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        file_fieldname: string
            The name of the CSV column containing the filename.
        node_csv_row : OrderedDict
            The CSV row for the current item.
        Returns
        -------
        string
            The path (absolute or relative) to the file.
    """
    file_path_from_csv = node_csv_row[file_fieldname].strip()
    if config['task'] == 'add_media':
        config['id_field'] = 'node_id'

    # Test whether file_path_from_csv is from one of the oEmbed providers
    # and if so, return it here.
    for oembed_provider in config['oembed_providers']:
        for provider_url, mtype in oembed_provider.items():
            if file_path_from_csv.startswith(provider_url):
                return file_path_from_csv

    # It's a remote file.
    if file_path_from_csv.startswith('http'):
        sections = urllib.parse.urlparse(file_path_from_csv)
        if config['task'] == 'add_media':
            subdir = os.path.join(config['input_dir'], re.sub('[^A-Za-z0-9]+', '_', 'nid_' + str(node_csv_row['node_id'])))
        else:
            subdir = os.path.join(config['input_dir'], re.sub('[^A-Za-z0-9]+', '_', node_csv_row[config['id_field']]))
        if make_dir:
            Path(subdir).mkdir(parents=True, exist_ok=True)

        if 'check' in config.keys() and config['check'] is True:
            os.rmdir(subdir)

        if config["use_node_title_for_media"]:
            # CSVs for add_media tasks don't contain 'title', so we need to get it.
            if config['task'] == 'add_media':
                node_csv_row['title'] = get_node_title_from_nid(config, node_csv_row['node_id'])
                if node_csv_row['title'] is False:
                    message = 'Cannot access node " + node_id + ", so cannot get its title for use in media filename. Using filename instead.'
                    logging.warning(message)
                    node_csv_row['title'] = os.path.basename(node_csv_row[file_fieldname].strip())

            filename = re.sub(r'\s+', '_', node_csv_row['title'])
            filename = re.sub('[^A-Za-z0-9]+', '_', filename)
            if filename[-1] == '_':
                filename = filename[:-1]
            downloaded_file_path = os.path.join(subdir, filename)
            extension = os.path.splitext(downloaded_file_path)[1]
        else:
            extension = os.path.splitext(sections.path)[1]
            filename = sections.path.split("/")[-1]
            downloaded_file_path = os.path.join(subdir, filename)

        if config['field_for_media_title']:
            filename = node_csv_row[config['field_for_media_title']]
            downloaded_file_path = os.path.join(subdir, filename)

        if config['use_nid_in_media_title']:
            filename = f"{node_id}-Original File"
            downloaded_file_path = os.path.join(subdir, filename)

        if extension == '':
            try:
                head_response = requests.head(file_path_from_csv, allow_redirects=True, verify=config['secure_ssl_only'])
                mimetype = head_response.headers['content-type']
                # In case servers return stuff beside the MIME type in Content-Type header.
                # Assumes they use ; to separate stuff and that what we're looking for is
                # in the first position.
                if ';' in mimetype:
                    mimetype_parts = mimetype.split(';')
                    mimetype = mimetype_parts[0].strip()
            except KeyError:
                mimetype = 'application/octet-stream'

            extension_with_dot = get_extension_from_mimetype(mimetype)
            downloaded_file_path = os.path.join(subdir, filename + extension_with_dot)

            # Check to see if a file with this path already exists; if so, insert an
            # incremented digit into the file path before the extension.
            if os.path.exists(downloaded_file_path):
                downloaded_file_path = get_deduped_file_path(downloaded_file_path)

        return downloaded_file_path
    # It's a local file.
    else:
        if os.path.isabs(file_path_from_csv):
            file_path = file_path_from_csv
        else:
            file_path = os.path.join(config['input_dir'], file_path_from_csv)
        return file_path


def get_node_media_ids(config, node_id, media_use_tids=[]):
    """Gets a list of media IDs for a node.
    """

    """Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        node_id : string
            The ID of the node to delete media from.
        media_use_tids : list
            Term IDs from the Islandora Media Use vocabulary. If present, media
            with one of these tids will be added to the returned list of media IDs.
            If empty, all media will be included in the returned list of media IDs.
        Returns
        -------
        list
            List of media IDs.
    """
    media_id_list = list()
    url = f"{config['host']}/node/{node_id}/media?_format=json"
    response = issue_request(config, 'GET', url)
    if response.status_code == 200:
        body = json.loads(response.text)
        for media in body:
            if len(media_use_tids) == 0:
                media_id_list.append(media['mid'][0]['value'])
            else:
                for media_use_tid_json in media['field_media_use']:
                    if media_use_tid_json['target_id'] in media_use_tids:
                        media_id_list.append(media['mid'][0]['value'])
        return media_id_list
    else:
        message = f'Attempt to get media for node ID {node_id} returned a {response.status_code} status code.'
        print("Error: " + message)
        logging.warning(message)
        return False


def download_remote_file(config, url, file_fieldname, node_csv_row, node_id):
    sections = urllib.parse.urlparse(url)
    try:
        response = requests.get(url, allow_redirects=True, verify=config['secure_ssl_only'])
    except requests.exceptions.Timeout as err_timeout:
        message = 'Workbench timed out trying to reach ' + \
            sections.netloc + ' while connecting to ' + url + '. Please verify that URL and check your network connection.'
        logging.error(message)
        logging.error(err_timeout)
        print('Error: ' + message)
        return False
    except requests.exceptions.ConnectionError as error_connection:
        message = 'Workbench cannot connect to ' + \
            sections.netloc + ' while connecting to ' + url + '. Please verify that URL and check your network connection.'
        logging.error(message)
        logging.error(error_connection)
        print('Error: ' + message)
        return False

    downloaded_file_path = get_preprocessed_file_path(config, file_fieldname, node_csv_row, node_id)

    f = open(downloaded_file_path, 'wb+')
    f.write(response.content)
    f.close()

    return downloaded_file_path


def download_file_from_drupal(config, node_id):
    '''WIP on https://github.com/mjordan/islandora_workbench/issues/492.
    '''

    """Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        node_id : string
            The ID of the node to delete media from.
        Returns
        -------
        file_name
            The downloaded file's name, or False if unable to download the file.
    """
    if config['export_file_directory'] is None:
        return False

    if not os.path.exists(config['export_file_directory']):
        try:
            os.mkdir(config['export_file_directory'])
        except Exception as e:
            message = 'Path in configuration option "export_file_directory" ("' + config['export_file_directory'] + '") is not writable.'
            logging.error(message + ' ' + str(e))
            sys.exit('Error: ' + message + ' See log for more detail.')
    else:
        message = 'Path in configuration option "export_file_directory" ("' + config['export_file_directory'] + '") already exists.'
        logging.info(message)

    media_list_url = f"{config['host']}/node/{node_id}/media?_format=json"
    media_list_response = issue_request(config, 'GET', media_list_url)
    if media_list_response.status_code == 200:
        try:
            media_list = json.loads(media_list_response.text)
        except json.decoder.JSONDecodeError as e:
            logging.error(f'Media query for node {node_id} produced the following error: {e}')
            return False
        if len(media_list) == 0:
            logging.warning(f'Node {node_id} has no media.')
            return False

        if str(config['export_file_media_use_term_id']).startswith('http'):
            config['export_file_media_use_term_id'] = get_term_id_from_uri(config, config['export_file_media_use_term_id'])

        if config['export_file_media_use_term_id'] is False:
            logging.error(f'Unknown value for configuration setting "export_file_media_use_term_id": {config["export_file_media_use_term_id"]}.')
            return False

        for media in media_list:
            for file_field_name in file_fields:
                if file_field_name in media:
                    if len(media[file_field_name]) and media['field_media_use'][0]['target_id'] == config['export_file_media_use_term_id']:
                        url_filename = os.path.basename(media[file_field_name][0]['url'])
                        downloaded_file_path = os.path.join(config['export_file_directory'], url_filename)
                        if os.path.exists(downloaded_file_path):
                            downloaded_file_path = get_deduped_file_path(downloaded_file_path)
                        f = open(downloaded_file_path, 'wb+')
                        # User needs to be anonymous since authenticated users are getting 403 responses. Probably something in
                        # Drupal's FileAccessControlHandler code is doing this.
                        file_download_response = requests.get(media[file_field_name][0]['url'], allow_redirects=True, verify=config['secure_ssl_only'])
                        if file_download_response.status_code == 200:
                            f.write(file_download_response.content)
                            f.close()
                            filename_for_logging = os.path.basename(downloaded_file_path)
                            logging.info(f'File "{filename_for_logging}" downloaded for node {node_id}.')
                            if os.path.isabs(config['export_file_directory']):
                                return downloaded_file_path
                            else:
                                return filename_for_logging
                        else:
                            message = f"File at {media[file_field_name][0]['url']} (part of media for node {node_id}) could " + \
                                f"not be downloaded (HTTP response code {file_download_response.status_code})."
                            logging.error(message)
                            return False
                    else:
                        logging.warning(f'Node {node_id} in new Summit has no files in "{file_field_name}".')
                        return False
                else:
                    continue
    else:
        logging.error(f'Attempt to fetch media list {media_list_url} returned an {r.status_code} HTTP response.')
        return False


def get_file_hash_from_drupal(config, file_uuid, algorithm):
    """Query the Integration module's hash controller at '/islandora_workbench_integration/file_hash'
       to get the hash of the file identified by file_uuid.
    """
    """Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        file_uuid : string
            The file's UUID.
        algorithm : string
            One of 'md5', 'sha1', or 'sha256'
        Returns
        -------
        string
            The requested hash.
    """
    url = config['host'] + '/islandora_workbench_integration/file_hash?file_uuid=' + file_uuid + '&algorithm=' + algorithm
    response = issue_request(config, 'GET', url)
    if response.status_code == 200:
        response_body = json.loads(response.text)
        return response_body[0]['checksum']
    else:
        logging.warning("Request to get %s hash for file %s returned a %s status code", algorithm, file_uuid, response.status_code)
        return False


def get_file_hash_from_local(config, file_path, algorithm):
    """Get the file's hash/checksum.
    """
    """Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        file_path : string
            The file's path.
        algorithm : string
            One of 'md5', 'sha1', or 'sha256'
        Returns
        -------
        string
            The requested hash.
    """
    if algorithm == 'md5':
        hash_object = hashlib.md5()
    if algorithm == 'sha1':
        hash_object = hashlib.sha1()
    if algorithm == 'sha256':
        hash_object = hashlib.sha256()

    with open(file_path, 'rb') as file:
        while True:
            chunk = file.read(hash_object.block_size)
            if not chunk:
                break
            hash_object.update(chunk)

    return hash_object.hexdigest()


def check_csv_file_exists(config, csv_file_target, file_path=None):
    """Confirms a CSV file exists.
    """
    """Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        csv_file_target: string
            Either 'node_fields' or 'taxonomy_fields'.
        file_path: string
            The path to the file to check (applies only to vocabulary CSVs).
        Returns
        -------
        string
            The absolute file path to the CSV file.
    """
    if csv_file_target == 'node_fields':
        if os.path.isabs(config['input_csv']):
            input_csv = config['input_csv']
        # For Google Sheets, the "extraction" is fired over in workbench.
        elif config['input_csv'].startswith('http'):
            input_csv = os.path.join(config['input_dir'], config['google_sheets_csv_filename'])
            message = "Extracting CSV data from " + config['input_csv'] + " (worksheet gid " + str(config['google_sheets_gid']) + ") to " + input_csv + '.'
            print(message)
            logging.info(message)
        elif config['input_csv'].endswith('xlsx'):
            input_csv = os.path.join(config['input_dir'], config['excel_csv_filename'])
            message = "Extracting CSV data from " + config['input_csv'] + " to " + input_csv + '.'
            print(message)
            logging.info(message)
        else:
            input_csv = os.path.join(config['input_dir'], config['input_csv'])

        if os.path.exists(input_csv):
            message = 'OK, CSV file ' + input_csv + ' found.'
            print(message)
            logging.info(message)
            return input_csv
        else:
            message = 'CSV file ' + input_csv + ' not found.'
            logging.error(message)
            sys.exit('Error: ' + message)
    if csv_file_target == 'taxonomy_fields':
        if os.path.isabs(file_path):
            input_csv = file_path
            '''
            # For Google Sheets, the "extraction" is fired over in workbench.
            elif config['input_csv'].startswith('http'):
                input_csv = os.path.join(config['input_dir'], config['google_sheets_csv_filename'])
                message = "Extracting CSV data from " + config['input_csv'] + " (worksheet gid " + str(config['google_sheets_gid']) + ") to " + input_csv + '.'
                print(message)
                logging.info(message)
            elif config['input_csv'].endswith('xlsx'):
                input_csv = os.path.join(config['input_dir'], config['excel_csv_filename'])
                message = "Extracting CSV data from " + config['input_csv'] + " to " + input_csv + '.'
                print(message)
                logging.info(message)
            '''
        else:
            input_csv = os.path.join(config['input_dir'], file_path)

        if os.path.exists(input_csv):
            message = 'OK, vocabulary CSV file ' + input_csv + ' found.'
            print(message)
            logging.info(message)
            return input_csv
        else:
            message = 'Vocabulary CSV file ' + input_csv + ' not found.'
            logging.error(message)
            sys.exit('Error: ' + message)


def get_csv_template(config, args):
    field_definitions = get_field_definitions(config, 'node')

    field_labels = collections.OrderedDict()
    field_labels['REMOVE THIS COLUMN (KEEP THIS ROW)'] = 'LABEL (REMOVE THIS ROW)'
    for field_name in field_definitions:
        if field_definitions[field_name]['label'] != '':
            field_labels[field_name] = field_definitions[field_name]['label']
        else:
            field_labels[field_name] = ''

    required = collections.OrderedDict()
    required['REMOVE THIS COLUMN (KEEP THIS ROW)'] = 'REQUIRED IN CREATE TASKS (REMOVE THIS ROW)'
    for field_name in field_definitions:
        if field_definitions[field_name]['required'] != '':
            if field_definitions[field_name]['required'] is True:
                required[field_name] = 'Yes'
            else:
                required[field_name] = 'No'
    required['title'] = 'Yes'
    required['uid'] = 'No'
    required['langcode'] = 'No'
    required['created'] = 'No'
    required[config['id_field']] = 'Yes'
    if config['nodes_only'] is True:
        required['file'] = 'Yes'
    else:
        required['file'] = 'No'

    mapping = dict()
    mapping['string'] = 'Free text'
    mapping['string_long'] = 'Free text'
    mapping['text'] = 'Free text'
    mapping['text_long'] = 'Free text'
    mapping['geolocation'] = '+49.16,-123.93'
    mapping['entity_reference'] = '100 [or term name or http://foo.com/someuri]'
    mapping['edtf'] = '2020-10-28'
    mapping['typed_relation'] = 'relators:art:30'
    mapping['integer'] = 100

    sample_data = collections.OrderedDict()
    sample_data['REMOVE THIS COLUMN (KEEP THIS ROW)'] = 'SAMPLE DATA (REMOVE THIS ROW)'
    sample_data[config['id_field']] = '0001'
    sample_data['file'] = 'myimage.jpg'
    sample_data['uid'] = '21'
    sample_data['langcode'] = 'fr'
    sample_data['created'] = '2020-11-15T23:49:22+00:00'
    sample_data['title'] = 'Free text'

    for field_name in field_definitions:
        if field_definitions[field_name]['field_type'] in mapping:
            sample_data[field_name] = mapping[field_definitions[field_name]['field_type']]
        else:
            sample_data[field_name] = ''

    csv_file_path = os.path.join(config['input_dir'], config['input_csv'] + '.csv_file_template')
    csv_file = open(csv_file_path, 'a+', encoding='utf-8')
    writer = csv.DictWriter(csv_file, fieldnames=sample_data.keys(), lineterminator="\n")
    writer.writeheader()
    # We want the labels and required rows to appear as the second and third rows so
    # add them before we add the sample data.
    writer.writerow(field_labels)
    writer.writerow(required)
    writer.writerow(sample_data)

    cardinality = collections.OrderedDict()
    cardinality['REMOVE THIS COLUMN (KEEP THIS ROW)'] = 'NUMBER OF VALUES ALLOWED (REMOVE THIS ROW)'
    cardinality[config['id_field']] = '1'
    cardinality['file'] = '1'
    cardinality['uid'] = '1'
    cardinality['langcode'] = '1'
    cardinality['created'] = '1'
    cardinality['title'] = '1'
    for field_name in field_definitions:
        if field_definitions[field_name]['cardinality'] == -1:
            cardinality[field_name] = 'unlimited'
        else:
            cardinality[field_name] = field_definitions[field_name]['cardinality']
    writer.writerow(cardinality)

    docs = dict()
    docs['string'] = 'Single-valued fields'
    docs['string_long'] = 'Single-valued fields'
    docs['text'] = 'Single-valued fields'
    docs['text_long'] = 'Single-valued fields'
    docs['geolocation'] = 'Geolocation fields'
    docs['entity_reference'] = 'Taxonomy reference fields'
    docs['edtf'] = 'EDTF fields'
    docs['typed_relation'] = 'Typed Relation fields'
    docs['integer'] = 'Single-valued fields'

    docs_tips = collections.OrderedDict()
    docs_tips['REMOVE THIS COLUMN (KEEP THIS ROW)'] = 'SECTION IN DOCUMENTATION (REMOVE THIS ROW)'
    docs_tips[config['id_field']] = 'Required fields'
    docs_tips['file'] = 'Required fields'
    docs_tips['uid'] = 'Base fields'
    docs_tips['langcode'] = 'Base fields'
    docs_tips['created'] = 'Base fields'
    docs_tips['title'] = 'Base fields'
    for field_name in field_definitions:
        if field_definitions[field_name]['field_type'] in docs:
            doc_reference = docs[field_definitions[field_name]['field_type']]
            docs_tips[field_name] = doc_reference
        else:
            docs_tips[field_name] = ''
    docs_tips['field_member_of'] = ''
    writer.writerow(docs_tips)

    csv_file.close()
    print('CSV template saved at ' + csv_file_path + '.')
    sys.exit()


def serialize_field_json(config, field_definitions, field_name, field_data):
    """Serializes JSON from a Drupal field into a string consistent with Workbench's CSV-field input format.
    """
    """Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        field_definitions : dict
            The field definitions object defined by get_field_definitions().
        field_name : string
            The Drupal fieldname/CSV column header.
        field_data : string
            Raw JSON from the field named 'field_name'.
        Returns
        -------
        string
            A string structured same as the Workbench CSV field data for the field type.
    """
    # Importing the workbench_fields module at the top of this module with the
    # rest of the imports causes a circular import exception, so we do it here.
    import workbench_fields

    # Entity reference fields (taxonomy term and node).
    if field_definitions[field_name]['field_type'] == 'entity_reference':
        serialized_field = workbench_fields.EntityReferenceField()
        csv_field_data = serialized_field.serialize(config, field_definitions, field_name, field_data)
    # Typed relation fields (currently, only taxonomy term)
    elif field_definitions[field_name]['field_type'] == 'typed_relation':
        serialized_field = workbench_fields.TypedRelationField()
        csv_field_data = serialized_field.serialize(config, field_definitions, field_name, field_data)
    # Geolocation fields.
    elif field_definitions[field_name]['field_type'] == 'geolocation':
        serialized_field = workbench_fields.GeolocationField()
        csv_field_data = serialized_field.serialize(config, field_definitions, field_name, field_data)
    # Link fields.
    elif field_definitions[field_name]['field_type'] == 'link':
        serialized_field = workbench_fields.LinkField()
        csv_field_data = serialized_field.serialize(config, field_definitions, field_name, field_data)
    # Authority Link fields.
    elif field_definitions[field_name]['field_type'] == 'authority_link':
        serialized_field = workbench_fields.AuthorityLinkField()
        csv_field_data = serialized_field.serialize(config, field_definitions, field_name, field_data)
    # Simple fields.
    else:
        serialized_field = workbench_fields.SimpleField()
        csv_field_data = serialized_field.serialize(config, field_definitions, field_name, field_data)

    return csv_field_data


def prep_node_ids_tsv(config):
    path_to_tsv_file = os.path.join(config['input_dir'], config['secondary_tasks_data_file'])
    if os.path.exists(path_to_tsv_file):
        os.remove(path_to_tsv_file)
    if len(config['secondary_tasks']) > 0:
        tsv_file = open(path_to_tsv_file, "a+", encoding='utf-8')
    else:
        return False

    # Write to the data file the names of config files identified in config['secondary_tasks']
    # since we need a way to ensure that only tasks whose names are registered there should
    # populate their objects' 'field_member_of'. We write the parent ID->nid map to this file
    # as well, in write_to_node_ids_tsv().
    for secondary_config_file in config['secondary_tasks']:
        tsv_file.write(secondary_config_file + "\t" + '' + "\n")
    tsv_file.close()


def write_to_node_ids_tsv(config, row_id, node_id):
    path_to_tsv_file = os.path.join(config['input_dir'], config['secondary_tasks_data_file'])
    tsv_file = open(path_to_tsv_file, "a+", encoding='utf-8')
    tsv_file.write(str(row_id) + "\t" + str(node_id) + "\n")
    tsv_file.close()


def read_node_ids_tsv(config):
    map = dict()
    path_to_tsv_file = os.path.join(config['input_dir'], config['secondary_tasks_data_file'])
    if config['secondary_tasks'] is not None:
        if not os.path.exists(path_to_tsv_file):
            message = 'Secondary task data file ' + path_to_tsv_file + ' not found.'
            print('Error: ' + message)
            logging.error(message)
            return map
            sys.exit()

    if os.path.exists(path_to_tsv_file):
        map_file = open(path_to_tsv_file, "r")
        entries = map_file.read().splitlines()
        for entry in entries:
            parts = entry.split("\t")
            map[parts[0]] = parts[1]

    return map


def csv_subset_warning(config):
    """Create a message indicating that the csv_start_row and csv_stop_row config
       options are present and that a subset of the input CSV will be used.
    """
    if config['csv_start_row'] != 0 or config['csv_stop_row'] is not None:
        message = f"Using a subset of the input CSV (will start at row {config['csv_start_row']}, stop at row {config['csv_stop_row']})."
        if config['csv_start_row'] != 0 and config['csv_stop_row'] is None:
            message = f"Using a subset of the input CSV (will start at row {config['csv_start_row']})."
        if config['csv_start_row'] == 0 and config['csv_stop_row'] is not None:
            message = f"Using a subset of the input CSV (will stop at row {config['csv_stop_row']})."
        print(message)
        logging.info(message)


def get_entity_reference_view_endpoints(config):
    """Gets entity reference View endpoints from config.
    """
    """Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        Returns
        -------
        dict
            Dictionary with Drupal field names as keys and View REST endpoints as values.
    """
    endpoint_mappings = dict()
    if 'entity_reference_view_endpoints' not in config:
        return endpoint_mappings

    for endpoint_mapping in config['entity_reference_view_endpoints']:
        for field_name, endpoint in endpoint_mapping.items():
            endpoint_mappings[field_name] = endpoint

    return endpoint_mappings


def get_percentage(part, whole):
    return 100 * float(part) / float(whole)


def calculate_response_time_trend(config, response_time):
    """Gets the average response time from the most recent 20 HTTP requests.
    """
    """Parameters
        ----------
        config : dict
            The configuration object defined by set_config_defaults().
        response_time : Response time of current request, in seconds.
            The string to test.
        Returns
        -------
        int|None
            The average response time of the most recent 20 requests.
    """
    http_response_times.append(response_time)
    if len(http_response_times) > 20:
        sample = http_response_times[-20:]
    else:
        sample = http_response_times
    if config['log_response_time_sample'] is True:
        logging.info("Response time trend sample: %s", sample)
    if len(sample) > 0:
        average = sum(sample) / len(sample)
        return average


def is_ascii(input):
    """Check if a string contains only ASCII characters.
    """
    """Parameters
        ----------
        input : str
            The string to test.
        Returns
        -------
        string
            True if all characters are within the ASCII character set,
            False otherwise.
    """
    return all(ord(c) < 128 for c in input)


def quick_delete_node(config, args):
    logging.info("--quick_delete_node task started for " + args.quick_delete_node)

    response = issue_request(config, 'GET', args.quick_delete_node + '?_format=json')
    if response.status_code != 200:
        message = f"Sorry, {args.quick_delete_node} can't be accessed. Please confirm the node exists and is accessible to the user defined in your Workbench configuration."
        logging.error(message)
        sys.exit("Error: " + message)

    node_id = get_nid_from_url_alias(config, args.quick_delete_node)
    if node_id is False:
        message = f"Sorry, {args.quick_delete_node} can't be accessed. Please confirm the node exists and is accessible to the user defined in your Workbench configuration."
        logging.error(message)
        sys.exit("Error: " + message)

    entity = json.loads(response.text)
    if 'type' in entity:
        if entity['type'][0]['target_type'] == 'node_type':
            # Delete the node's media first.
            if config['delete_media_with_nodes'] is True:
                media_endpoint = config['host'] + '/node/' + str(node_id) + '/media?_format=json'
                media_response = issue_request(config, 'GET', media_endpoint)
                media_response_body = json.loads(media_response.text)
                media_messages = []
                for media in media_response_body:
                    if 'mid' in media:
                        media_id = media['mid'][0]['value']
                        media_delete_status_code = remove_media_and_file(config, media_id)
                        if media_delete_status_code == 204:
                            media_messages.append("+ Media " + config['host'] + '/media/' + str(media_id) + " deleted.")

            # Then the node.
            node_endpoint = config['host'] + '/node/' + str(node_id) + '?_format=json'
            node_response = issue_request(config, 'DELETE', node_endpoint)
            if node_response.status_code == 204:
                if config['progress_bar'] is False:
                    print("Node " + args.quick_delete_node + " deleted.")
                logging.info("Node %s deleted.", args.quick_delete_node)
            if config['delete_media_with_nodes'] is True and config['progress_bar'] is False:
                if len(media_messages):
                    for media_message in media_messages:
                        print(media_message)
        else:
            message = f"{args.quick_delete_node} does not apear to be a node."
            logging.error(message)
            sys.exit("Error: " + message)
    else:
        message = f"{args.quick_delete_node} does not apear to be a node."
        logging.error(message)
        sys.exit("Error: " + message)

    sys.exit()


def quick_delete_media(config, args):
    logging.info("--quick_delete_mediatask started for " + args.quick_delete_media)

    if config['standalone_media_url'] is False and not args.quick_delete_media.endswith('/edit'):
        message = f"You need to add '/edit' to the end of your media URL (e.g. {args.quick_delete_media}/edit)."
        logging.error(message)
        sys.exit("Error: " + message)

    if config['standalone_media_url'] is True and args.quick_delete_media.endswith('/edit'):
        message = f"You need to remove '/edit' to the end of your media URL."
        logging.error(message)
        sys.exit("Error: " + message)

    ping_response = issue_request(config, 'GET', args.quick_delete_media + '?_format=json')
    if ping_response.status_code == 404:
        message = f"Cannot find {args.quick_delete_media}. Please verify the media URL and try again."
        logging.error(message)
        sys.exit("Error: " + message)

    entity = json.loads(ping_response.text)
    if 'mid' not in entity:
        message = f"{args.quick_delete_media} does not apear to be a media."
        logging.error(message)
        sys.exit("Error: " + message)

    media_id = get_mid_from_media_url_alias(config, args.quick_delete_media)
    media_delete_status_code = remove_media_and_file(config, media_id)
    if media_delete_status_code == 204:
        message = f"Media {args.quick_delete_media} and associated file deleted."
        print(message)
        logging.info(message)
    else:
        message = f"Media {args.quick_delete_media} and associated file not deleted. See Workbench log for more detail."
        print("Error: " + message)
        logging.error(message + f"HTTP response code was {media_delete_status_code}.")

    sys.exit()