>>      receive() external payable {}
    function _buyQuote(address quoteToken, uint256 amountXIn, uint256 minReturn) internal returns (uint256 amountYOut) {
        require(msg.value >= amountXIn, "Insufficient msg.value");
//...

>>       if (msg.value > (amountXIn + fee + 1)) {
            (bool success, ) = payable(msg.sender).call{value: msg.value - amountXIn - fee - 1}("");
            require(success, "ETH transfer failed");
        }

        emit BuyQuote(quoteToken, amountXIn, amountYOut);
    }
