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pragma solidity ^0.8.0;

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

contract LiquidityPool {

mapping(address => uint256) public reserves;

// Event emitted when a swap occurs
    event Swap(
        address indexed sender,
        address indexed tokenIn,
        address indexed tokenOut,
        uint256 amountIn,
        uint256 amountOut
    );

// Function to add liquidity to the pool
    function addLiquidity(address _token, uint256 _amount) public {
        require(_amount > 0, "Amount must be greater than 0");
        
        // Transfer tokens from the user to the contract
        IERC20(_token).transferFrom(msg.sender, address(this), _amount);
        
        // Update reserves
        reserves[_token] += _amount;
    }

// Function to swap tokens
    function swap(
        address _tokenIn,
        address _tokenOut,
        uint256 _amountIn
    ) public returns (uint256 amountOut) {
        require(
            reserves[_tokenIn] > 0 && reserves[_tokenOut] > 0,
            "Insufficient liquidity"
        );
        require(_amountIn > 0, "Amount must be greater than 0");

// Transfer input tokens from the user to the contract
        IERC20(_tokenIn).transferFrom(msg.sender, address(this), _amountIn);

// Calculate output amount using a simple constant product formula
        // (This is a basic example and can be replaced with more sophisticated AMM formulas)
        amountOut = (_amountIn * reserves[_tokenOut]) / reserves[_tokenIn];

// Update reserves
        reserves[_tokenIn] += _amountIn;
        reserves[_tokenOut] -= amountOut;

// Transfer output tokens to the user
        IERC20(_tokenOut).transfer(msg.sender, amountOut);

// Emit the Swap event
        emit Swap(msg.sender, _tokenIn, _tokenOut, _amountIn, amountOut);
    }
}