CHI Token Gas Rebate Contract

GasSaver.sol

// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.7.0;

interface IFreeFromUpTo {
    function freeFromUpTo(address from, uint256 value) external returns (uint256 freed);
}

contract GasSaver {
    IFreeFromUpTo chi;

    constructor (IFreeFromUpTo _chi) public {
        chi = _chi;
    }

    modifier discountCHI {
        uint256 gasStart = gasleft();
        _;
        uint256 gasSpent = 21000 + gasStart - gasleft() + 16 * msg.data.length;
        chi.freeFromUpTo(msg.sender, (gasSpent + 14154) / 41130);
    }
}