Adapting an Existing AMM

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;

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

contract MyPropPair {
    address public immutable token0;
    address public immutable token1;

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

    function getAmountOut(bool zeroForOne, uint256 amountIn)
        external view returns (uint256 amountOut)
    {
        amountOut = _price(zeroForOne, amountIn);
    }

    function swapExactIn(
        bool zeroForOne,
        uint256 amountIn,
        uint256 amountOutMin,
        address to,
        uint256 deadline
    ) external payable returns (uint256 amountOut) {
        if (deadline != 0) require(block.timestamp <= deadline, "expired");
        (address tin, address tout) = zeroForOne ? (token0, token1) : (token1, token0);

        IERC20(tin).transferFrom(msg.sender, address(this), amountIn);
        amountOut = _price(zeroForOne, amountIn);
        require(amountOut >= amountOutMin, "slippage");
        IERC20(tout).transfer(to, amountOut);
    }

    function _price(bool zeroForOne, uint256 amountIn) internal view returns (uint256) {
        // oracle / curve / inventory logic
    }
}