// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract TokenSale {
    address payable public owner;
    

    // This mapping keeps track of users who have sent ETH to buy tokens.
    mapping(address => uint256) public buyers;

    // Event to emit when a purchase is made
    event Purchase(address indexed buyer, uint256 ethAmount);

    constructor() {
        owner = payable(msg.sender);
    }

    // Function to buy tokens
    function buyTokens() public payable {
        

        // Record the buyer's purchase.
        buyers[msg.sender] += msg.value;
        
        // Emit an event for the purchase
        emit Purchase(msg.sender, msg.value);
        
        
    }

    // Withdraw function for contract's owner to withdraw funds
    function withdraw() public {
        require(msg.sender == owner, "You are not the owner.");
        require(address(this).balance > 0, "The balance is zero.");
        
        uint256 balance = address(this).balance;
        owner.transfer(balance);
    }

    // Function to check the amount of ETH sent to the contract by a user
    function checkContribution(address user) public view returns (uint256) {
        return buyers[user];
    }
}

{
  "compilationTarget": {
    "TokenSale.sol": "TokenSale"
  },
  "evmVersion": "istanbul",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "ipfs"
  },
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "remappings": []
}