// SPDX-License-Identifier: Apache-2.0

/*
 * Copyright 2021, Offchain Labs, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

pragma solidity ^0.8.7;

import "../libraries/IGasRefunder.sol";

import "@openzeppelin/contracts/access/Ownable.sol";

/**
 * @notice DEPRECATED - only for classic version, see new repo (https://github.com/OffchainLabs/nitro/tree/master/contracts)
 * for new updates
 */
contract GasRefunder is IGasRefunder, Ownable {
    mapping(address => bool) public allowedContracts;
    mapping(address => bool) public allowedRefundees;
    address public disallower;

    struct CommonParameters {
        uint128 maxRefundeeBalance;
        uint32 extraGasMargin;
        uint8 calldataCost;
        uint64 maxGasTip;
        uint64 maxGasCost;
        uint32 maxSingleGasUsage;
    }

    CommonParameters public commonParams;

    enum CommonParameterKey {
        MAX_REFUNDEE_BALANCE,
        EXTRA_GAS_MARGIN,
        CALLDATA_COST,
        MAX_GAS_TIP,
        MAX_GAS_COST,
        MAX_SINGLE_GAS_USAGE
    }

    enum RefundDenyReason {
        CONTRACT_NOT_ALLOWED,
        REFUNDEE_NOT_ALLOWED,
        REFUNDEE_ABOVE_MAX_BALANCE,
        OUT_OF_FUNDS
    }

    event RefundedGasCosts(
        address indexed refundee,
        address indexed contractAddress,
        bool indexed success,
        uint256 gas,
        uint256 gasPrice,
        uint256 amountPaid
    );
    event RefundGasCostsDenied(
        address indexed refundee,
        address indexed contractAddress,
        RefundDenyReason indexed reason,
        uint256 gas
    );
    event Deposited(address sender, uint256 amount);
    event Withdrawn(address initiator, address destination, uint256 amount);
    event ContractAllowedSet(address indexed addr, bool indexed allowed);
    event RefundeeAllowedSet(address indexed addr, bool indexed allowed);
    event DisallowerSet(address indexed addr);
    event CommonParameterSet(CommonParameterKey indexed parameter, uint256 value);

    constructor() Ownable() {
        commonParams = CommonParameters({
            maxRefundeeBalance: 0, // no limit
            extraGasMargin: 4000, // 4k gas
            calldataCost: 12, // Between 4 for zero bytes and 16 for non-zero bytes
            maxGasTip: 2 gwei,
            maxGasCost: 120 gwei,
            maxSingleGasUsage: 2e6 // 2 million gas
        });
    }

    function setDisallower(
        address addr
    ) external onlyOwner {
        disallower = addr;
        emit DisallowerSet(addr);
    }

    function allowContracts(
        address[] calldata addresses
    ) external onlyOwner {
        setContractsAllowedImpl(addresses, true);
    }

    function disallowContracts(
        address[] calldata addresses
    ) external {
        require(msg.sender == owner() || msg.sender == disallower, "NOT_AUTHORIZED");
        setContractsAllowedImpl(addresses, false);
    }

    function setContractsAllowedImpl(address[] calldata addresses, bool allow) internal {
        for (uint256 i = 0; i < addresses.length; i++) {
            address addr = addresses[i];
            allowedContracts[addr] = allow;
            emit ContractAllowedSet(addr, allow);
        }
    }

    function allowRefundees(
        address[] calldata addresses
    ) external onlyOwner {
        setRefundeesAllowedImpl(addresses, true);
    }

    function disallowRefundees(
        address[] calldata addresses
    ) external {
        require(msg.sender == owner() || msg.sender == disallower, "NOT_AUTHORIZED");
        setRefundeesAllowedImpl(addresses, false);
    }

    function setRefundeesAllowedImpl(address[] calldata addresses, bool allow) internal {
        for (uint256 i = 0; i < addresses.length; i++) {
            address addr = addresses[i];
            allowedRefundees[addr] = allow;
            emit RefundeeAllowedSet(addr, allow);
        }
    }

    function setMaxRefundeeBalance(
        uint128 newValue
    ) external onlyOwner {
        commonParams.maxRefundeeBalance = newValue;
        emit CommonParameterSet(CommonParameterKey.MAX_REFUNDEE_BALANCE, newValue);
    }

    function setExtraGasMargin(
        uint32 newValue
    ) external onlyOwner {
        commonParams.extraGasMargin = newValue;
        emit CommonParameterSet(CommonParameterKey.EXTRA_GAS_MARGIN, newValue);
    }

    function setCalldataCost(
        uint8 newValue
    ) external onlyOwner {
        commonParams.calldataCost = newValue;
        emit CommonParameterSet(CommonParameterKey.CALLDATA_COST, newValue);
    }

    function setMaxGasTip(
        uint64 newValue
    ) external onlyOwner {
        commonParams.maxGasTip = newValue;
        emit CommonParameterSet(CommonParameterKey.MAX_GAS_TIP, newValue);
    }

    function setMaxGasCost(
        uint64 newValue
    ) external onlyOwner {
        commonParams.maxGasCost = newValue;
        emit CommonParameterSet(CommonParameterKey.MAX_GAS_COST, newValue);
    }

    function setMaxSingleGasUsage(
        uint32 newValue
    ) external onlyOwner {
        commonParams.maxSingleGasUsage = newValue;
        emit CommonParameterSet(CommonParameterKey.MAX_SINGLE_GAS_USAGE, newValue);
    }

    receive() external payable {
        emit Deposited(msg.sender, msg.value);
    }

    function withdraw(address payable destination, uint256 amount) external onlyOwner {
        // It's expected that destination is an EOA
        // solhint-disable-next-line avoid-low-level-calls
        (bool success,) = destination.call{value: amount}("");
        require(success, "WITHDRAW_FAILED");
        emit Withdrawn(msg.sender, destination, amount);
    }

    function onGasSpent(
        address payable refundee,
        uint256 gasUsed,
        uint256 calldataSize
    ) external override returns (bool success) {
        uint256 startGasLeft = gasleft();

        uint256 ownBalance = address(this).balance;

        if (ownBalance == 0) {
            emit RefundGasCostsDenied(refundee, msg.sender, RefundDenyReason.OUT_OF_FUNDS, gasUsed);
            return false;
        }

        if (!allowedContracts[msg.sender]) {
            emit RefundGasCostsDenied(
                refundee, msg.sender, RefundDenyReason.CONTRACT_NOT_ALLOWED, gasUsed
            );
            return false;
        }
        if (!allowedRefundees[refundee]) {
            emit RefundGasCostsDenied(
                refundee, msg.sender, RefundDenyReason.REFUNDEE_NOT_ALLOWED, gasUsed
            );
            return false;
        }

        uint256 estGasPrice = block.basefee + commonParams.maxGasTip;
        if (tx.gasprice < estGasPrice) {
            estGasPrice = tx.gasprice;
        }
        if (commonParams.maxGasCost != 0 && estGasPrice > commonParams.maxGasCost) {
            estGasPrice = commonParams.maxGasCost;
        }

        // Retrieve these variables before measuring gasleft()
        uint256 refundeeBalance = refundee.balance;
        uint256 maxRefundeeBalance = commonParams.maxRefundeeBalance;
        uint256 maxSingleGasUsage = commonParams.maxSingleGasUsage;

        // Add in a bit of a buffer for the tx costs not measured with gasleft
        gasUsed +=
            startGasLeft + commonParams.extraGasMargin + (calldataSize * commonParams.calldataCost);
        // Split this up into two statements so that gasleft() comes after the storage loads
        gasUsed -= gasleft();

        if (maxSingleGasUsage != 0 && gasUsed > maxSingleGasUsage) {
            gasUsed = maxSingleGasUsage;
        }

        uint256 refundAmount = estGasPrice * gasUsed;
        if (maxRefundeeBalance != 0 && refundeeBalance + refundAmount > maxRefundeeBalance) {
            if (refundeeBalance > maxRefundeeBalance) {
                // The refundee is already above their max balance
                // emit RefundGasCostsDenied(
                //     refundee,
                //     msg.sender,
                //     RefundDenyReason.REFUNDEE_ABOVE_MAX_BALANCE,
                //     gasUsed
                // );
                return false;
            } else {
                refundAmount = maxRefundeeBalance - refundeeBalance;
            }
        }

        if (refundAmount > ownBalance) {
            refundAmount = ownBalance;
        }

        // It's expected that refundee is an EOA
        // solhint-disable-next-line avoid-low-level-calls
        (success,) = refundee.call{value: refundAmount}("");
        emit RefundedGasCosts(refundee, msg.sender, success, gasUsed, estGasPrice, refundAmount);
    }
}