basic-gas-tank-with-3074-invoker.sol

contract GasTank {

    mapping (address => uint) dappDespoit

    function execWithRefund(invokerAddress, authSig, gasLimit, dappAddress) {
        require(gasLimit * tx.gasPrice > dappDeposit[dappAddress]);
        const preGas = gas.left();
        invokerAddress.invoke(authSig);
        const postGas = gas.left();
        dappDeposit[dappAddress] -= (preGas - postGas) * tx.gasPrice;
    }
}