// SPDX-License-Identifier: MIT OR Apache-2.0
pragma solidity >=0.6.11;
pragma experimental ABIEncoderV2;

// ============ Internal Imports ============
import {Home} from "../Home.sol";
import {Version0} from "../Version0.sol";
import {XAppConnectionManager, TypeCasts} from "../XAppConnectionManager.sol";
import {IMessageRecipient} from "../../interfaces/IMessageRecipient.sol";
import {GovernanceMessage} from "./GovernanceMessage.sol";
// ============ External Imports ============
import {Initializable} from "@openzeppelin/contracts/proxy/Initializable.sol";
import {SafeMath} from "@openzeppelin/contracts/math/SafeMath.sol";
import {TypedMemView} from "@summa-tx/memview-sol/contracts/TypedMemView.sol";

contract GovernanceRouter is Version0, Initializable, IMessageRecipient {
    // ============ Libraries ============

    using SafeMath for uint256;
    using TypedMemView for bytes;
    using TypedMemView for bytes29;
    using GovernanceMessage for bytes29;

    // ============ Immutables ============

    uint32 public immutable localDomain;
    // number of seconds before recovery can be activated
    uint256 public immutable recoveryTimelock;

    // ============ Public Storage ============

    // timestamp when recovery timelock expires; 0 if timelock has not been initiated
    uint256 public recoveryActiveAt;
    // the address of the recovery manager multisig
    address public recoveryManager;
    // the local entity empowered to call governance functions, set to 0x0 on non-Governor chains
    address public governor;
    // domain of Governor chain -- for accepting incoming messages from Governor
    uint32 public governorDomain;
    // xAppConnectionManager contract which stores Replica addresses
    XAppConnectionManager public xAppConnectionManager;
    // domain -> remote GovernanceRouter contract address
    mapping(uint32 => bytes32) public routers;
    // array of all domains with registered GovernanceRouter
    uint32[] public domains;

    // ============ Upgrade Gap ============

    // gap for upgrade safety
    uint256[43] private __GAP;

    // ============ Events ============

    /**
     * @notice Emitted a remote GovernanceRouter address is added, removed, or changed
     * @param domain the domain of the remote Router
     * @param previousRouter the previously registered router; 0 if router is being added
     * @param newRouter the new registered router; 0 if router is being removed
     */
    event SetRouter(
        uint32 indexed domain,
        bytes32 previousRouter,
        bytes32 newRouter
    );

    /**
     * @notice Emitted when the Governor role is transferred
     * @param previousGovernorDomain the domain of the previous Governor
     * @param newGovernorDomain the domain of the new Governor
     * @param previousGovernor the address of the previous Governor; 0 if the governor was remote
     * @param newGovernor the address of the new Governor; 0 if the governor is remote
     */
    event TransferGovernor(
        uint32 previousGovernorDomain,
        uint32 newGovernorDomain,
        address indexed previousGovernor,
        address indexed newGovernor
    );

    /**
     * @notice Emitted when the RecoveryManager role is transferred
     * @param previousRecoveryManager the address of the previous RecoveryManager
     * @param newRecoveryManager the address of the new RecoveryManager
     */
    event TransferRecoveryManager(
        address indexed previousRecoveryManager,
        address indexed newRecoveryManager
    );

    /**
     * @notice Emitted when recovery state is initiated by the RecoveryManager
     * @param recoveryManager the address of the current RecoveryManager who initiated the transition
     * @param recoveryActiveAt the block at which recovery state will be active
     */
    event InitiateRecovery(
        address indexed recoveryManager,
        uint256 recoveryActiveAt
    );

    /**
     * @notice Emitted when recovery state is exited by the RecoveryManager
     * @param recoveryManager the address of the current RecoveryManager who initiated the transition
     */
    event ExitRecovery(address recoveryManager);

    modifier typeAssert(bytes29 _view, GovernanceMessage.Types _type) {
        _view.assertType(uint40(_type));
        _;
    }

    // ============ Modifiers ============

    modifier onlyReplica() {
        require(xAppConnectionManager.isReplica(msg.sender), "!replica");
        _;
    }

    modifier onlyGovernorRouter(uint32 _domain, bytes32 _address) {
        require(_isGovernorRouter(_domain, _address), "!governorRouter");
        _;
    }

    modifier onlyGovernor() {
        require(msg.sender == governor, "! called by governor");
        _;
    }

    modifier onlyRecoveryManager() {
        require(msg.sender == recoveryManager, "! called by recovery manager");
        _;
    }

    modifier onlyInRecovery() {
        require(inRecovery(), "! in recovery");
        _;
    }

    modifier onlyNotInRecovery() {
        require(!inRecovery(), "in recovery");
        _;
    }

    modifier onlyGovernorOrRecoveryManager() {
        if (!inRecovery()) {
            require(msg.sender == governor, "! called by governor");
        } else {
            require(
                msg.sender == recoveryManager,
                "! called by recovery manager"
            );
        }
        _;
    }

    // ============ Constructor ============

    constructor(uint32 _localDomain, uint256 _recoveryTimelock) {
        localDomain = _localDomain;
        recoveryTimelock = _recoveryTimelock;
    }

    // ============ Initializer ============

    function initialize(
        address _xAppConnectionManager,
        address _recoveryManager
    ) public initializer {
        // initialize governor
        address _governorAddr = msg.sender;
        bool _isLocalGovernor = true;
        _transferGovernor(localDomain, _governorAddr, _isLocalGovernor);
        // initialize recovery manager
        recoveryManager = _recoveryManager;
        // initialize XAppConnectionManager
        setXAppConnectionManager(_xAppConnectionManager);
        require(
            xAppConnectionManager.localDomain() == localDomain,
            "XAppConnectionManager bad domain"
        );
    }

    // ============ External Functions ============

    /**
     * @notice Handle Optics messages
     * For all non-Governor chains to handle messages
     * sent from the Governor chain via Optics.
     * Governor chain should never receive messages,
     * because non-Governor chains are not able to send them
     * @param _origin The domain (of the Governor Router)
     * @param _sender The message sender (must be the Governor Router)
     * @param _message The message
     */
    function handle(
        uint32 _origin,
        bytes32 _sender,
        bytes memory _message
    ) external override onlyReplica onlyGovernorRouter(_origin, _sender) {
        bytes29 _msg = _message.ref(0);
        if (_msg.isValidCall()) {
            _handleCall(_msg.tryAsCall());
        } else if (_msg.isValidTransferGovernor()) {
            _handleTransferGovernor(_msg.tryAsTransferGovernor());
        } else if (_msg.isValidSetRouter()) {
            _handleSetRouter(_msg.tryAsSetRouter());
        } else {
            require(false, "!valid message type");
        }
    }

    /**
     * @notice Dispatch calls locally
     * @param _calls The calls
     */
    function callLocal(GovernanceMessage.Call[] calldata _calls)
        external
        onlyGovernorOrRecoveryManager
    {
        for (uint256 i = 0; i < _calls.length; i++) {
            _dispatchCall(_calls[i]);
        }
    }

    /**
     * @notice Dispatch calls on a remote chain via the remote GovernanceRouter
     * @param _destination The domain of the remote chain
     * @param _calls The calls
     */
    function callRemote(
        uint32 _destination,
        GovernanceMessage.Call[] calldata _calls
    ) external onlyGovernor onlyNotInRecovery {
        // ensure that destination chain has enrolled router
        bytes32 _router = _mustHaveRouter(_destination);
        // format call message
        bytes memory _msg = GovernanceMessage.formatCalls(_calls);
        // dispatch call message using Optics
        Home(xAppConnectionManager.home()).dispatch(
            _destination,
            _router,
            _msg
        );
    }

    /**
     * @notice Transfer governorship
     * @param _newDomain The domain of the new governor
     * @param _newGovernor The address of the new governor
     */
    function transferGovernor(uint32 _newDomain, address _newGovernor)
        external
        onlyGovernor
        onlyNotInRecovery
    {
        bool _isLocalGovernor = _isLocalDomain(_newDomain);
        // transfer the governor locally
        _transferGovernor(_newDomain, _newGovernor, _isLocalGovernor);
        // if the governor domain is local, we only need to change the governor address locally
        // no need to message remote routers; they should already have the same domain set and governor = bytes32(0)
        if (_isLocalGovernor) {
            return;
        }
        // format transfer governor message
        bytes memory _transferGovernorMessage = GovernanceMessage
            .formatTransferGovernor(
                _newDomain,
                TypeCasts.addressToBytes32(_newGovernor)
            );
        // send transfer governor message to all remote routers
        // note: this assumes that the Router is on the global GovernorDomain;
        // this causes a process error when relinquishing governorship
        // on a newly deployed domain which is not the GovernorDomain
        _sendToAllRemoteRouters(_transferGovernorMessage);
    }

    /**
     * @notice Transfer recovery manager role
     * @dev callable by the recoveryManager at any time to transfer the role
     * @param _newRecoveryManager The address of the new recovery manager
     */
    function transferRecoveryManager(address _newRecoveryManager)
        external
        onlyRecoveryManager
    {
        emit TransferRecoveryManager(recoveryManager, _newRecoveryManager);
        recoveryManager = _newRecoveryManager;
    }

    /**
     * @notice Set the router address for a given domain and
     * dispatch the change to all remote routers
     * @param _domain The domain
     * @param _router The address of the new router
     */
    function setRouter(uint32 _domain, bytes32 _router)
        external
        onlyGovernor
        onlyNotInRecovery
    {
        // set the router locally
        _setRouter(_domain, _router);
        // format message to set the router on all remote routers
        bytes memory _setRouterMessage = GovernanceMessage.formatSetRouter(
            _domain,
            _router
        );

        _sendToAllRemoteRouters(_setRouterMessage);
    }

    /**
     * @notice Set the router address *locally only*
     * for the deployer to setup the router mapping locally
     * before transferring governorship to the "true" governor
     * @dev External helper for contract setup
     * @param _domain The domain
     * @param _router The new router
     */
    function setRouterLocal(uint32 _domain, bytes32 _router)
        external
        onlyGovernorOrRecoveryManager
    {
        // set the router locally
        _setRouter(_domain, _router);
    }

    /**
     * @notice Set the address of the XAppConnectionManager
     * @dev Domain/address validation helper
     * @param _xAppConnectionManager The address of the new xAppConnectionManager
     */
    function setXAppConnectionManager(address _xAppConnectionManager)
        public
        onlyGovernorOrRecoveryManager
    {
        xAppConnectionManager = XAppConnectionManager(_xAppConnectionManager);
    }

    /**
     * @notice Initiate the recovery timelock
     * @dev callable by the recovery manager
     */
    function initiateRecoveryTimelock()
        external
        onlyNotInRecovery
        onlyRecoveryManager
    {
        require(recoveryActiveAt == 0, "recovery already initiated");
        // set the time that recovery will be active
        recoveryActiveAt = block.timestamp.add(recoveryTimelock);
        emit InitiateRecovery(recoveryManager, recoveryActiveAt);
    }

    /**
     * @notice Exit recovery mode
     * @dev callable by the recovery manager to end recovery mode
     */
    function exitRecovery() external onlyRecoveryManager {
        require(recoveryActiveAt != 0, "recovery not initiated");
        delete recoveryActiveAt;
        emit ExitRecovery(recoveryManager);
    }

    // ============ Public Functions ============

    /**
     * @notice Check if the contract is in recovery mode currently
     * @return TRUE iff the contract is actively in recovery mode currently
     */
    function inRecovery() public view returns (bool) {
        uint256 _recoveryActiveAt = recoveryActiveAt;
        bool _recoveryInitiated = _recoveryActiveAt != 0;
        bool _recoveryActive = _recoveryActiveAt <= block.timestamp;
        return _recoveryInitiated && _recoveryActive;
    }

    // ============ Internal Functions ============

    /**
     * @notice Handle message dispatching calls locally
     * @param _msg The message
     */
    function _handleCall(bytes29 _msg)
        internal
        typeAssert(_msg, GovernanceMessage.Types.Call)
    {
        GovernanceMessage.Call[] memory _calls = _msg.getCalls();
        for (uint256 i = 0; i < _calls.length; i++) {
            _dispatchCall(_calls[i]);
        }
    }

    /**
     * @notice Handle message transferring governorship to a new Governor
     * @param _msg The message
     */
    function _handleTransferGovernor(bytes29 _msg)
        internal
        typeAssert(_msg, GovernanceMessage.Types.TransferGovernor)
    {
        uint32 _newDomain = _msg.domain();
        address _newGovernor = TypeCasts.bytes32ToAddress(_msg.governor());
        bool _isLocalGovernor = _isLocalDomain(_newDomain);
        _transferGovernor(_newDomain, _newGovernor, _isLocalGovernor);
    }

    /**
     * @notice Handle message setting the router address for a given domain
     * @param _msg The message
     */
    function _handleSetRouter(bytes29 _msg)
        internal
        typeAssert(_msg, GovernanceMessage.Types.SetRouter)
    {
        uint32 _domain = _msg.domain();
        bytes32 _router = _msg.router();
        _setRouter(_domain, _router);
    }

    /**
     * @notice Dispatch message to all remote routers
     * @param _msg The message
     */
    function _sendToAllRemoteRouters(bytes memory _msg) internal {
        Home _home = Home(xAppConnectionManager.home());

        for (uint256 i = 0; i < domains.length; i++) {
            if (domains[i] != uint32(0)) {
                _home.dispatch(domains[i], routers[domains[i]], _msg);
            }
        }
    }

    /**
     * @notice Dispatch call locally
     * @param _call The call
     * @return _ret
     */
    function _dispatchCall(GovernanceMessage.Call memory _call)
        internal
        returns (bytes memory _ret)
    {
        address _toContract = TypeCasts.bytes32ToAddress(_call.to);
        // attempt to dispatch using low-level call
        bool _success;
        (_success, _ret) = _toContract.call(_call.data);
        // revert if the call failed
        require(_success, "call failed");
    }

    /**
     * @notice Transfer governorship within this contract's state
     * @param _newDomain The domain of the new governor
     * @param _newGovernor The address of the new governor
     * @param _isLocalGovernor True if the newDomain is the localDomain
     */
    function _transferGovernor(
        uint32 _newDomain,
        address _newGovernor,
        bool _isLocalGovernor
    ) internal {
        // require that the governor domain has a valid router
        if (!_isLocalGovernor) {
            _mustHaveRouter(_newDomain);
        }
        // Governor is 0x0 unless the governor is local
        address _newGov = _isLocalGovernor ? _newGovernor : address(0);
        // emit event before updating state variables
        emit TransferGovernor(governorDomain, _newDomain, governor, _newGov);
        // update state
        governorDomain = _newDomain;
        governor = _newGov;
    }

    /**
     * @notice Set the router for a given domain
     * @param _domain The domain
     * @param _newRouter The new router
     */
    function _setRouter(uint32 _domain, bytes32 _newRouter) internal {
        bytes32 _previousRouter = routers[_domain];
        // emit event at beginning in case return after remove
        emit SetRouter(_domain, _previousRouter, _newRouter);
        // if the router is being removed, remove the domain
        if (_newRouter == bytes32(0)) {
            _removeDomain(_domain);
            return;
        }
        // if the router is being added, add the domain
        if (_previousRouter == bytes32(0)) {
            _addDomain(_domain);
        }
        // update state with new router
        routers[_domain] = _newRouter;
    }

    /**
     * @notice Add a domain that has a router
     * @param _domain The domain
     */
    function _addDomain(uint32 _domain) internal {
        domains.push(_domain);
    }

    /**
     * @notice Remove a domain and its associated router
     * @param _domain The domain
     */
    function _removeDomain(uint32 _domain) internal {
        delete routers[_domain];
        // find the index of the domain to remove & delete it from domains[]
        for (uint256 i = 0; i < domains.length; i++) {
            if (domains[i] == _domain) {
                delete domains[i];
                return;
            }
        }
    }

    /**
     * @notice Determine if a given domain and address is the Governor Router
     * @param _domain The domain
     * @param _address The address of the domain's router
     * @return _ret True if the given domain/address is the
     * Governor Router.
     */
    function _isGovernorRouter(uint32 _domain, bytes32 _address)
        internal
        view
        returns (bool)
    {
        return _domain == governorDomain && _address == routers[_domain];
    }

    /**
     * @notice Determine if a given domain is the local domain
     * @param _domain The domain
     * @return _ret - True if the given domain is the local domain
     */
    function _isLocalDomain(uint32 _domain) internal view returns (bool) {
        return _domain == localDomain;
    }

    /**
     * @notice Require that a domain has a router and returns the router
     * @param _domain The domain
     * @return _router - The domain's router
     */
    function _mustHaveRouter(uint32 _domain)
        internal
        view
        returns (bytes32 _router)
    {
        _router = routers[_domain];
        require(_router != bytes32(0), "!router");
    }
}