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

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (governance/extensions/GovernorTimelockControl.sol)

pragma solidity ^0.8.19;

import {IGovernorTimelock} from "./IGovernorTimelock.sol";
import {IGovernor, Governor} from "../Governor.sol";
import {TimelockController} from "../TimelockController.sol";
import {IERC165} from "../../interfaces/IERC165.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.
 */
abstract contract GovernorTimelockControl is IGovernorTimelock, Governor {
    TimelockController 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.
     */
    constructor(TimelockController timelockAddress) {
        _updateTimelock(timelockAddress);
    }

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

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

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

        // core tracks execution, so we just have to check if successful proposal have been queued.
        bytes32 queueid = _timelockIds[proposalId];
        if (queueid == bytes32(0)) {
            return currentState;
        } else if (_timelock.isOperationPending(queueid)) {
            return ProposalState.Queued;
        } else if (_timelock.isOperationDone(queueid)) {
            // This can happen if the proposal is executed directly on the timelock.
            return ProposalState.Executed;
        } else {
            // This can happen if the proposal is canceled directly on the timelock.
            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);

        ProposalState currentState = state(proposalId);
        if (currentState != ProposalState.Succeeded) {
            revert GovernorUnexpectedProposalState(
                proposalId,
                currentState,
                _encodeStateBitmap(ProposalState.Succeeded)
            );
        }

        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 Overridden 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 {
        // execute
        _timelock.executeBatch{value: msg.value}(targets, values, calldatas, 0, descriptionHash);
        // cleanup for refund
        delete _timelockIds[proposalId];
    }

    /**
     * @dev Overridden version of the {Governor-_cancel} function to cancel the timelocked proposal if it as already
     * been queued.
     */
    // This function can reenter through the external call to the timelock, but we assume the timelock is trusted and
    // well behaved (according to TimelockController) and this will not happen.
    // slither-disable-next-line reentrancy-no-eth
    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);
        bytes32 timelockId = _timelockIds[proposalId];

        if (timelockId != 0) {
            // cancel
            _timelock.cancel(timelockId);
            // cleanup
            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(TimelockController newTimelock) external virtual onlyGovernance {
        _updateTimelock(newTimelock);
    }

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