ChatGPT swap token solidity

TokenSwap.sol

pragma solidity ^0.6.0;

import "https://github.com/OpenZeppelin/openzeppelin-solidity/contracts/token/ERC20/SafeERC20.sol";

contract TokenSwap {
    // The contract maintains a mapping of user accounts to their token balances
    mapping (address => uint256) public balances;

    // The contract maintains a reference to the ERC20 token contract
    // that is being swapped
    SafeERC20 token;

    // The contract maintains the current exchange rate for the swap
    uint256 public exchangeRate;

    constructor(address _tokenAddress, uint256 _exchangeRate) public {
        token = SafeERC20(_tokenAddress);
        exchangeRate = _exchangeRate;
    }

    // This function is called by users to initiate the token swap
    function swap(uint256 _amount) public {
        // Ensure the user has enough tokens to complete the swap
        require(balances[msg.sender] >= _amount, "Insufficient balance");

        // Calculate the number of tokens to receive in the swap
        uint256 tokensToReceive = _amount.mul(exchangeRate);

        // Transfer the tokens from the user to the contract
        token.transferFrom(msg.sender, address(this), _amount);

        // Update the user's balance in the contract
        balances[msg.sender] = balances[msg.sender].sub(_amount);

        // Transfer the tokens to the user
        token.transfer(msg.sender, tokensToReceive);
    }

    // This function can be called by anyone to view the current exchange rate
    function getExchangeRate() public view returns (uint256) {
        return exchangeRate;
    }
}