AMM流动性

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

interface IERC20 {
    function balanceOf(address account) external view returns (uint256);
    function transfer(address recipient, uint256 amount) external returns (bool);
    function allowance(address owner, address spender) external view returns (uint256);
    function approve(address spender, uint256 amount) external returns (bool);
    function totalSupply() external view returns (uint256);
    function decimals() external view returns (uint8);
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);

    // 添加safeTransferFrom方法
    function safeTransferFrom(address sender, address recipient, uint256 amount) external;
    function safeTransferFrom(address sender, address recipient, uint256 amount, bytes calldata data) external;
}

contract AMMPool {
    IERC20 public token; // ERC20 代币
    address public WETH; // WETH 地址
    uint256 public k; // 常数乘积

    constructor(IERC20 _token, address _WETH) {
        token = _token;
        WETH = _WETH;
        // 初始化常数乘积 k
        k = IERC20(WETH).balanceOf(address(this)) * _token.balanceOf(address(this));
    }

    // 添加流动性
    function deposit(uint256 _tokenAmount, uint256 _wethAmount) external {
        require(_tokenAmount * IERC20(WETH).balanceOf(address(this)) == _wethAmount * token.balanceOf(address(this)), "Invalid deposit amounts");
        token.safeTransferFrom(msg.sender, address(this), _tokenAmount);
        IERC20(WETH).safeTransferFrom(msg.sender, address(this), _wethAmount);
        k = IERC20(WETH).balanceOf(address(this)) * token.balanceOf(address(this));
    }

    // 移除流动性
    function withdraw(uint256 _tokenAmount, uint256 _wethAmount) external {
        require(token.balanceOf(address(this)) - _tokenAmount >= 0 && IERC20(WETH).balanceOf(address(this)) - _wethAmount >= 0, "Invalid withdraw amounts");
        token.transfer(msg.sender, _tokenAmount);
        IERC20(WETH).transfer(msg.sender, _wethAmount);
        k = IERC20(WETH).balanceOf(address(this)) * token.balanceOf(address(this));
    }

    // 交易功能
    function trade(uint256 _sellAmount, uint256 _buyAmount) external {
        require(_sellAmount <= token.balanceOf(msg.sender), "Insufficient token balance");
        require(_buyAmount <= IERC20(WETH).balanceOf(msg.sender), "Insufficient WETH balance");

        token.safeTransferFrom(msg.sender, address(this), _sellAmount);
        IERC20(WETH).safeTransferFrom(msg.sender, address(this), _buyAmount);

        uint256 newK = IERC20(WETH).balanceOf(address(this)) * token.balanceOf(address(this));
        uint256 diff = newK - k;
        require(diff == 0, "Invalid trade amounts");

        k = newK;
    }
}