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pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

contract LiquidityPool {
    IERC20 public token0;
    IERC20 public token1;

uint256 public reserve0;
    uint256 public reserve1;

constructor(address _token0, address _token1) {
        token0 = IERC20(_token0);
        token1 = IERC20(_token1);

// Initial liquidity (needs to be added separately)
        //  This example omits the initial liquidity addition for brevity.
    }

function addLiquidity(uint256 _amount0, uint256 _amount1) external {
        require(_amount0 > 0 && _amount1 > 0, "Amounts must be greater than zero");

// Transfer tokens to the contract
        token0.transferFrom(msg.sender, address(this), _amount0);
        token1.transferFrom(msg.sender, address(this), _amount1);

// Update reserves
        reserve0 += _amount0;
        reserve1 += _amount1;
    }

function swap(address _tokenIn, uint256 _amountIn, address _tokenOut, uint256 _amountOutMin) external {
        require(_amountIn > 0 && _amountOutMin > 0, "Amounts must be greater than zero");

IERC20 tokenIn = IERC20(_tokenIn);
        IERC20 tokenOut = IERC20(_tokenOut);

//Transfer tokens to the contract
        tokenIn.transferFrom(msg.sender, address(this), _amountIn);

uint256 amountOut;
        if (_tokenIn == address(token0) ) {
            // Calculate amountOut using constant product formula (x * y = k)
            amountOut = (_amountIn * reserve1) / (reserve0 + _amountIn);
            require(amountOut >= _amountOutMin, "Insufficient output amount");
            reserve0 += _amountIn;
            reserve1 -= amountOut;
        } else if (_tokenIn == address(token1)) {
            amountOut = (_amountIn * reserve0) / (reserve1 + _amountIn);
            require(amountOut >= _amountOutMin, "Insufficient output amount");
            reserve1 += _amountIn;
            reserve0 -= amountOut;
        } else {
            revert("Invalid token");
        }

// Transfer output tokens
        tokenOut.transfer(msg.sender, amountOut);
    }

function getReserves() external view returns (uint256, uint256) {
        return (reserve0, reserve1);
    }
}