Perform additional swap at the moment the 'transfer' function of a solidity contract is triggered

[aghering23]

Question: is it possible to perform an additional swap at the moment the 'transfer' function of a solidity contract is triggered?

Network: Ethereum
Uniswap Pair: V2

Case:
I have a smartcontract with an erc20 token and user swaps (w)eth for erc20, this triggers the 'transfer' function on the smartcontract. In the smartcontract 'transfer' function, i want to trigger an additional swap call where the smartcontract sells some of its erc20 to (w)eth. Using a modifier and conditions statements to prevent the initial call to infinite loop.

I have read some documentation on multicalls, but can't seem to find if this will work for uniswap v2 pairs

---

Solidity:
`// SPDX-License-Identifier: Unlicensed

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/token/ERC20/extensions/ERC20Burnable.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/Address.sol";

import "@uniswap/v2-core/contracts/interfaces/IUniswapV2Factory.sol";
import "@uniswap/v2-core/contracts/interfaces/IUniswapV2Pair.sol";
import "@uniswap/v2-periphery/contracts/interfaces/IUniswapV2Router01.sol";
import "@uniswap/v2-periphery/contracts/interfaces/IUniswapV2Router02.sol";

pragma solidity ^0.8.16;

contract SOL is ERC20, ERC20Burnable, Ownable {
using Address for address;

// IDEX - Interface Decentralised Exchange
address public IDEXFactory;
address public IDEXRouter;
address public IDEXWrapped;
address public IDEXPair;

uint256 public contractBalanceNative;
uint256 public contractBalanceToken;


constructor() ERC20("SOLIDITY6", "SOL6") {
    IDEXFactory = 0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f;
    IDEXRouter = 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D;
    IDEXWrapped = 0xc778417E063141139Fce010982780140Aa0cD5Ab;
            
    _approve(address(this), address(IDEXFactory), type(uint256).max);
    _approve(address(this), address(IDEXRouter), type(uint256).max);


    _mint(address(this), 1000 * 10 ** decimals());
    
    dexCreatePair();
}




bool inSwap;

modifier lockTheSwap {
    inSwap = true;
    _;
    inSwap = false;
}


function _transfer(address from, address to, uint256 amount) internal override returns (bool) {     
    
    require(from != address(0), "");
    require(to != address(0), "");
    require(_balances[from] - amount >= 0, "");

    if(inSwap)
    { 
        return _basicTransfer(from, to, amount); 
    }
    else
    {
        if (contractBalanceToken > 1000) { dexSellTokensForNativeLock(contractBalanceToken); }
        super._transfer(from, to, amount);
        return true;
    }
}






function _basicTransfer(address from, address to, uint256 amount) internal returns (bool) {
    
    _balances[from] = _balances[from] - amount;
    _balances[to] = _balances[to] + amount;
    emit Transfer(from, to, amount);
    return true;
}

function dexCreatePair() internal {
    
    address WETHaddress = IUniswapV2Router02(IDEXRouter).WETH();
    IDEXWrapped = WETHaddress;

    address uniswapV2Pair = IUniswapV2Factory(IDEXFactory).createPair(address(this), WETHaddress);
    IDEXPair = uniswapV2Pair;
}

function dexSellTokensForNativeLock(uint256 amountTokens) internal lockTheSwap {
    
    _approve(address(this), address(IDEXRouter), type(uint256).max);

    address[] memory path = new address[](2);
    path[0] = address(this);
    path[1] = IDEXWrapped;

    IUniswapV2Router02(IDEXRouter).swapExactTokensForETHSupportingFeeOnTransferTokens(amountTokens, 0, path, address(this), block.timestamp);
}

function _afterTokenTransfer() internal virtual {    
    contractBalanceCheck();
}

function contractBalanceCheck() public returns(uint, uint){        
    contractBalanceNative = address(this).balance;
    contractBalanceToken = balanceOf(address(this));
    return(contractBalanceNative, contractBalanceToken);
}

receive() external payable {}

}`