contract OVM_CrossDomainEnabled {
    // Messenger contract used to send and recieve messages from the other domain.
    address public messenger;

    /***************
     * Constructor *
     ***************/    
    constructor(
        address _messenger
    ) {
        messenger = _messenger;
    }

    /**********************
     * Function Modifiers *
     **********************/

    /**
     * @notice Enforces that the modified function is only callable by a specific cross-domain account.
     * @param _sourceDomainAccount The only account on the originating domain which is authenticated to call this function.
     */
    modifier onlyFromCrossDomainAccount(
        address _sourceDomainAccount
    ) {
        require(
            msg.sender == address(getCrossDomainMessenger()),
            "OVM_XCHAIN: messenger contract unauthenticated"
        );

        require(
            getCrossDomainMessenger().xDomainMessageSender() == _sourceDomainAccount,
            "OVM_XCHAIN: wrong sender of cross-domain message"
        );

        _;
    }
    
    /**********************
     * Internal Functions *
     **********************/

    /**
     * @notice Gets the messenger, usually from storage.  This function is exposed in case a child contract needs to override.
     * @return The address of the cross-domain messenger contract which should be used. 
     */
    function getCrossDomainMessenger()
        internal
        virtual
        returns(
            iAbs_BaseCrossDomainMessenger
        )
    {
        return iAbs_BaseCrossDomainMessenger(messenger);
    }

    /**
     * @notice Sends a message to an account on another domain
     * @param _crossDomainTarget The intended recipient on the destination domain
     * @param _data The data to send to the target (usually calldata to a function with `onlyFromCrossDomainAccount()`)
     * @param _gasLimit The gasLimit for the receipt of the message on the target domain.
     */
    function sendCrossDomainMessage(
        address _crossDomainTarget,
        bytes memory _data,
        uint32 _gasLimit
    ) internal {
        getCrossDomainMessenger().sendMessage(_crossDomainTarget, _data, _gasLimit);
    }
}
/**
 * @title OVM_CrossDomainEnabled
 * @dev Helper contract for contracts performing cross-domain communications
 *
 * Compiler used: defined by inheriting contract
 * Runtime target: defined by inheriting contract
 */
function sendCrossDomainMessage(
    address _crossDomainTarget,
    bytes memory _data,
    uint32 _gasLimit
) internal {
    getCrossDomainMessenger().sendMessage(_crossDomainTarget, _data, _gasLimit);
}

/**
 * @notice Sends a message to an account on another domain
 * @param _crossDomainTarget The intended recipient on the destination domain
 * @param _data The data to send to the target (usually calldata to a function with `onlyFromCrossDomainAccount()`)
 * @param _gasLimit The gasLimit for the receipt of the message on the target domain.
 */