MatchCalcs.sol

pragma solidity 0.8.19;

contract MatchCalcs {
    uint constant expScale = 1e18;
    
    struct Exp {
        uint mantissa;
    }

    function mulScalarTruncate(Exp memory a, uint scalar) pure external returns (uint) {
        return truncate(mulScalar(a, scalar));
    }

    function mulScalar(Exp memory a, uint scalar) pure internal returns (Exp memory) {
        uint256 scaledMantissa = mulUInt(a.mantissa, scalar);

        return Exp({mantissa: scaledMantissa});
    }

    function mulUInt(uint a, uint b) internal pure returns (uint) {
        if (a == 0) {
            return 0;
        }

        uint c = a * b;

        if (c / a != b) {
            return 0;
        } else {
            return c;
        }
    }

    function truncate(Exp memory exp) pure internal returns (uint) {
        // Note: We are not using careful math here as we're performing a division that cannot fail
        return exp.mantissa / expScale;
    }

    function getToWithdraw(uint256 amount, uint256 exchangeRate) pure external returns (uint) {
        return amount * (10 ** 18) / exchangeRate;
    }
}