add ffi bindings for maps (#5)

CHANGELOG.md

@@ -1,5 +1,6 @@
 # Changelog
 
+- Add `map` module native JavaScript maps.
 - `promise.new` is added to enable creating promises with a delayed resolve.
 
 ## v0.5.0 - 2023-01-19

src/ffi.mjs

@@ -134,3 +134,22 @@ export function all_promises(...promises) {
     return Promise.all(promises);
   }
 }
+
+export function map_new() {
+  return new Map();
+}
+
+export function map_set(map, key, value) {
+  return map.set(key, value);
+}
+
+export function map_get(map, key) {
+  if (map.has(key)) {
+    return new Ok(map.get(key));
+  }
+  return new Error(undefined);
+}
+
+export function map_size(map) {
+  return map.size;
+}

src/gleam/javascript/map.gleam

@@ -0,0 +1,13 @@
+pub type Map(key, value)
+
+@external(javascript, "../../ffi.mjs", "map_new")
+pub fn new() -> Map(key, value)
+
+@external(javascript, "../../ffi.mjs", "map_set")
+pub fn set(a: Map(key, value), b: key, c: value) -> Map(key, value)
+
+@external(javascript, "../../ffi.mjs", "map_get")
+pub fn get(a: Map(key, value), b: key) -> Result(value, Nil)
+
+@external(javascript, "../../ffi.mjs", "map_size")
+pub fn size(a: Map(key, value)) -> Int

test/gleam/javascript/map_test.gleam

@@ -0,0 +1,27 @@
+import gleam/javascript/map
+import gleeunit/should
+
+pub fn map_size_test() {
+  let m = map.new()
+  should.equal(map.size(m), 0)
+
+  map.set(m, "a", 1)
+  should.equal(map.size(m), 1)
+
+  map.set(m, "b", 1)
+  should.equal(map.size(m), 2)
+
+  map.set(m, "b", 10)
+  should.equal(map.size(m), 2)
+}
+
+pub fn map_retrieve_test() {
+  let m = map.new()
+  should.equal(map.get(m, "a"), Error(Nil))
+
+  map.set(m, "a", 1)
+  should.equal(map.get(m, "a"), Ok(1))
+
+  map.set(m, "a", 2)
+  should.equal(map.get(m, "a"), Ok(2))
+}