openzeppelin-contracts/contracts/governance/extensions/GovernorTimelockControlUpgradeable.sol

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (governance/extensions/GovernorTimelockControl.sol)

pragma solidity ^0.8.0;

import "./IGovernorTimelockUpgradeable.sol";
import "../GovernorUpgradeable.sol";
import "../TimelockControllerUpgradeable.sol";
import "../../proxy/utils/Initializable.sol";

/**
 * @dev Extension of {Governor} that binds the execution process to an instance of {TimelockController}. This adds a
 * delay, enforced by the {TimelockController} to all successful proposal (in addition to the voting duration). The
 * {Governor} needs the proposer (and ideally the executor) roles for the {Governor} to work properly.
 *
 * Using this model means the proposal will be operated by the {TimelockController} and not by the {Governor}. Thus,
 * the assets and permissions must be attached to the {TimelockController}. Any asset sent to the {Governor} will be
 * inaccessible.
 *
 * WARNING: Setting up the TimelockController to have additional proposers besides the governor is very risky, as it
 * grants them powers that they must be trusted or known not to use: 1) {onlyGovernance} functions like {relay} are
 * available to them through the timelock, and 2) approved governance proposals can be blocked by them, effectively
 * executing a Denial of Service attack. This risk will be mitigated in a future release.
 *
 * _Available since v4.3._
 */
abstract contract GovernorTimelockControlUpgradeable is Initializable, IGovernorTimelockUpgradeable, GovernorUpgradeable {
    TimelockControllerUpgradeable private _timelock;
    mapping(uint256 => bytes32) private _timelockIds;

    /**
     * @dev Emitted when the timelock controller used for proposal execution is modified.
     */
    event TimelockChange(address oldTimelock, address newTimelock);

    /**
     * @dev Set the timelock.
     */
    function __GovernorTimelockControl_init(TimelockControllerUpgradeable timelockAddress) internal onlyInitializing {
        __GovernorTimelockControl_init_unchained(timelockAddress);
    }

    function __GovernorTimelockControl_init_unchained(TimelockControllerUpgradeable timelockAddress) internal onlyInitializing {
        _updateTimelock(timelockAddress);
    }

    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override(IERC165Upgradeable, GovernorUpgradeable) returns (bool) {
        return interfaceId == type(IGovernorTimelockUpgradeable).interfaceId || super.supportsInterface(interfaceId);
    }

    /**
     * @dev Overriden version of the {Governor-state} function with added support for the `Queued` status.
     */
    function state(uint256 proposalId) public view virtual override(IGovernorUpgradeable, GovernorUpgradeable) returns (ProposalState) {
        ProposalState status = super.state(proposalId);

        if (status != ProposalState.Succeeded) {
            return status;
        }

        // core tracks execution, so we just have to check if successful proposal have been queued.
        bytes32 queueid = _timelockIds[proposalId];
        if (queueid == bytes32(0)) {
            return status;
        } else if (_timelock.isOperationDone(queueid)) {
            return ProposalState.Executed;
        } else if (_timelock.isOperationPending(queueid)) {
            return ProposalState.Queued;
        } else {
            return ProposalState.Canceled;
        }
    }

    /**
     * @dev Public accessor to check the address of the timelock
     */
    function timelock() public view virtual override returns (address) {
        return address(_timelock);
    }

    /**
     * @dev Public accessor to check the eta of a queued proposal
     */
    function proposalEta(uint256 proposalId) public view virtual override returns (uint256) {
        uint256 eta = _timelock.getTimestamp(_timelockIds[proposalId]);
        return eta == 1 ? 0 : eta; // _DONE_TIMESTAMP (1) should be replaced with a 0 value
    }

    /**
     * @dev Function to queue a proposal to the timelock.
     */
    function queue(
        address[] memory targets,
        uint256[] memory values,
        bytes[] memory calldatas,
        bytes32 descriptionHash
    ) public virtual override returns (uint256) {
        uint256 proposalId = hashProposal(targets, values, calldatas, descriptionHash);

        require(state(proposalId) == ProposalState.Succeeded, "Governor: proposal not successful");

        uint256 delay = _timelock.getMinDelay();
        _timelockIds[proposalId] = _timelock.hashOperationBatch(targets, values, calldatas, 0, descriptionHash);
        _timelock.scheduleBatch(targets, values, calldatas, 0, descriptionHash, delay);

        emit ProposalQueued(proposalId, block.timestamp + delay);

        return proposalId;
    }

    /**
     * @dev Overriden execute function that run the already queued proposal through the timelock.
     */
    function _execute(
        uint256, /* proposalId */
        address[] memory targets,
        uint256[] memory values,
        bytes[] memory calldatas,
        bytes32 descriptionHash
    ) internal virtual override {
        _timelock.executeBatch{value: msg.value}(targets, values, calldatas, 0, descriptionHash);
    }

    /**
     * @dev Overriden version of the {Governor-_cancel} function to cancel the timelocked proposal if it as already
     * been queued.
     */
    function _cancel(
        address[] memory targets,
        uint256[] memory values,
        bytes[] memory calldatas,
        bytes32 descriptionHash
    ) internal virtual override returns (uint256) {
        uint256 proposalId = super._cancel(targets, values, calldatas, descriptionHash);

        if (_timelockIds[proposalId] != 0) {
            _timelock.cancel(_timelockIds[proposalId]);
            delete _timelockIds[proposalId];
        }

        return proposalId;
    }

    /**
     * @dev Address through which the governor executes action. In this case, the timelock.
     */
    function _executor() internal view virtual override returns (address) {
        return address(_timelock);
    }

    /**
     * @dev Public endpoint to update the underlying timelock instance. Restricted to the timelock itself, so updates
     * must be proposed, scheduled, and executed through governance proposals.
     *
     * CAUTION: It is not recommended to change the timelock while there are other queued governance proposals.
     */
    function updateTimelock(TimelockControllerUpgradeable newTimelock) external virtual onlyGovernance {
        _updateTimelock(newTimelock);
    }

    function _updateTimelock(TimelockControllerUpgradeable newTimelock) private {
        emit TimelockChange(address(_timelock), address(newTimelock));
        _timelock = newTimelock;
    }

    /**
     * This empty reserved space is put in place to allow future versions to add new
     * variables without shifting down storage in the inheritance chain.
     * See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
     */
    uint256[48] private __gap;
}