// SPDX-License-Identifier: MIT
// +build ovm
pragma solidity >0.5.0 <0.8.0;
pragma experimental ABIEncoderV2;

/* Interface Imports */
import {
    iBaseCustomCrossDomainMessenger
} from "./interfaces/iBaseCustomCrossDomainMessenger.sol";

/* Library Imports */
import {
    Lib_ReentrancyGuard
} from "@eth-optimism/contracts/build/contracts/libraries/utils/Lib_ReentrancyGuard.sol";

abstract contract BaseCustomCrossDomainMessenger is
    iBaseCustomCrossDomainMessenger,
    Lib_ReentrancyGuard
{
    /**********************
     * Contract Variables *
     **********************/

    mapping(bytes32 => bool) public relayedMessages;
    mapping(bytes32 => bool) public successfulMessages;
    mapping(bytes32 => bool) public sentMessages;
    uint256 public messageNonce;
    address public override xDomainMessageSender;

    /********************
     * Public Functions *
     ********************/

    /**
     * Sends a cross domain message to the target messenger.
     * @param _target Target contract address.
     * @param _message Message to send to the target.
     * @param _gasLimit Gas limit for the provided message.
     * @param _timelock Timelock (in seconds) for the provided message.
     */
    function sendMessage(
        address _target,
        bytes memory _message,
        uint32 _gasLimit,
        uint256 _timelock
    ) public override {
        bytes memory xDomainCalldata =
            _getXDomainCalldata(
                _target,
                msg.sender,
                _message,
                messageNonce,
                _timelock
            );

        messageNonce += 1;
        sentMessages[keccak256(xDomainCalldata)] = true;

        _sendXDomainMessage(xDomainCalldata, _gasLimit);
        emit SentMessage(xDomainCalldata);
    }

    /**********************
     * Internal Functions *
     **********************/

    /**
     * Generates the correct cross domain calldata for a message.
     * @param _target Target contract address.
     * @param _sender Message sender address.
     * @param _message Message to send to the target.
     * @param _messageNonce Nonce for the provided message.
     * @param _timelock Timelock (in seconds) for the provided message.
     * @return ABI encoded cross domain calldata.
     */
    function _getXDomainCalldata(
        address _target,
        address _sender,
        bytes memory _message,
        uint256 _messageNonce,
        uint256 _timelock
    ) internal pure returns (bytes memory) {
        return
            abi.encodeWithSignature(
                "relayMessage(address,address,bytes,uint256,uint256)",
                _target,
                _sender,
                _message,
                _messageNonce,
                _timelock
            );
    }

    /**
     * Sends a cross domain message.
     * @param _message Message to send.
     * @param _gasLimit Gas limit for the provided message.
     */
    function _sendXDomainMessage(bytes memory _message, uint256 _gasLimit)
        internal
        virtual
    {
        revert("Implement me in child contracts!");
    }
}