// File: contracts/EmissionController.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import {IERC20} from "@openzeppelin/contracts/interfaces/IERC20.sol";
import {Math} from "@openzeppelin/contracts/utils/math/Math.sol";

import {Epoch} from "./utils/Epoch.sol";
import {IGaugeVoter} from "./interfaces/IGaugeVoter.sol";
import {IRegistry} from "./interfaces/IRegistry.sol";
import {IEmissionController} from "./interfaces/IEmissionController.sol";

contract EmissionController is IEmissionController, Epoch {
    IRegistry public registry;

    uint256 public ratePerEpoch;
    mapping(address => address) public tokenStakingPool;

    event RateUpdated(uint256 old, uint256 rate);

    constructor(address _registry, uint256 _ratePerEpoch)
        Epoch(7 days, block.timestamp, 0)
    {
        registry = IRegistry(_registry);
        ratePerEpoch = _ratePerEpoch;
    }

    function allocateEmission() external override checkEpoch {
        uint256 mahaBalance = IERC20(registry.maha()).balanceOf(address(this));

        // figure out how much tokens to send
        uint256 balanceToSend;

        // if a rate was not set, then we send everything in the contract
        if (ratePerEpoch == 0)
            balanceToSend = mahaBalance;

            // if a rate was set, then we send as much as we can
        else balanceToSend = Math.min(mahaBalance, ratePerEpoch);

        require(balanceToSend > 0, "no maha to send");

        // approve token and notify the gauge voter
        IERC20(registry.maha()).transfer(registry.gaugeVoter(), balanceToSend);
        IGaugeVoter(registry.gaugeVoter()).notifyRewardAmount(balanceToSend);
    }

    function updateRate(uint256 epochRate) external onlyOwner {
        emit RateUpdated(ratePerEpoch, epochRate);
        ratePerEpoch = epochRate;
    }
}

// File: @openzeppelin/contracts/interfaces/IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (interfaces/IERC20.sol)

pragma solidity ^0.8.0;

import "../token/ERC20/IERC20.sol";

// File: @openzeppelin/contracts/utils/math/Math.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (utils/math/Math.sol)

pragma solidity ^0.8.0;

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a >= b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow.
        return (a & b) + (a ^ b) / 2;
    }

    /**
     * @dev Returns the ceiling of the division of two numbers.
     *
     * This differs from standard division with `/` in that it rounds up instead
     * of rounding down.
     */
    function ceilDiv(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b - 1) / b can overflow on addition, so we distribute.
        return a / b + (a % b == 0 ? 0 : 1);
    }
}

// File: contracts/utils/Epoch.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import {Math} from "@openzeppelin/contracts/utils/math/Math.sol";
import {SafeMath} from "@openzeppelin/contracts/utils/math/SafeMath.sol";
import {Operator} from "./Operator.sol";
import {IEpoch} from "../interfaces/IEpoch.sol";

contract Epoch is IEpoch, Operator {
  using SafeMath for uint256;

  uint256 private period;
  uint256 private startTime;
  uint256 private lastExecutedAt;

  /* ========== CONSTRUCTOR ========== */

  constructor(
    uint256 _period,
    uint256 _startTime,
    uint256 _startEpoch
  ) {
    require(_startTime >= block.timestamp, "Epoch: invalid start time");
    period = _period;
    startTime = _startTime;
    lastExecutedAt = startTime.add(_startEpoch.mul(period));
  }

  /* ========== Modifier ========== */

  modifier checkStartTime() {
    require(block.timestamp >= startTime, "Epoch: not started yet");
    _;
  }

  modifier checkEpoch() {
    require(block.timestamp > startTime, "Epoch: not started yet");
    require(_callable(), "Epoch: not allowed");
    _;
    lastExecutedAt = block.timestamp;
  }

  function _getLastEpoch() internal view returns (uint256) {
    return lastExecutedAt.sub(startTime).div(period);
  }

  function _getCurrentEpoch() internal view returns (uint256) {
    return Math.max(startTime, block.timestamp).sub(startTime).div(period);
  }

  function callable() external view override returns (bool) {
    return _callable();
  }

  function _callable() internal view returns (bool) {
    return _getCurrentEpoch() >= _getNextEpoch();
  }

  function _getNextEpoch() internal view returns (uint256) {
    if (startTime == lastExecutedAt) {
      return _getLastEpoch();
    }
    return _getLastEpoch().add(1);
  }

  // epoch
  function getLastEpoch() external view override returns (uint256) {
    return _getLastEpoch();
  }

  function getCurrentEpoch() external view override returns (uint256) {
    return Math.max(startTime, block.timestamp).sub(startTime).div(period);
  }

  function getNextEpoch() external view override returns (uint256) {
    return _getNextEpoch();
  }

  function nextEpochPoint() external view override returns (uint256) {
    return startTime.add(_getNextEpoch().mul(period));
  }

  // params
  function getPeriod() external view override returns (uint256) {
    return period;
  }

  function getStartTime() external view override returns (uint256) {
    return startTime;
  }

  /* ========== GOVERNANCE ========== */

  function setPeriod(uint256 _period) external onlyOperator {
    period = _period;
  }
}

// File: contracts/interfaces/IGaugeVoter.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import {IRegistry} from "./IRegistry.sol";

interface IGaugeVoter {
    function attachTokenToGauge(uint256 _tokenId, address account) external;

    function detachTokenFromGauge(uint256 _tokenId, address account) external;

    function emitDeposit(
        uint256 _tokenId,
        address account,
        uint256 amount
    ) external;

    function emitWithdraw(
        uint256 _tokenId,
        address account,
        uint256 amount
    ) external;

    function distribute(address _gauge) external;

    function registry() external view returns (IRegistry);

    function notifyRewardAmount(uint256 amount) external;

    event GaugeCreated(
        address indexed gauge,
        address creator,
        address indexed bribe,
        address indexed pool
    );
    event Voted(address indexed voter, uint256 tokenId, int256 weight);
    event Abstained(uint256 tokenId, int256 weight);
    event Deposit(
        address indexed lp,
        address indexed gauge,
        uint256 tokenId,
        uint256 amount
    );
    event Withdraw(
        address indexed lp,
        address indexed gauge,
        uint256 tokenId,
        uint256 amount
    );
    event NotifyReward(
        address indexed sender,
        address indexed reward,
        uint256 amount
    );
    event DistributeReward(
        address indexed sender,
        address indexed gauge,
        uint256 amount
    );
    event Attach(address indexed owner, address indexed gauge, uint256 tokenId);
    event Detach(address indexed owner, address indexed gauge, uint256 tokenId);
    event Whitelisted(
        address indexed whitelister,
        address indexed token,
        bool value
    );
}

// File: contracts/interfaces/IRegistry.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import {IAccessControl} from "@openzeppelin/contracts/access/IAccessControl.sol";

interface IRegistry is IAccessControl {
    event MahaChanged(address indexed whom, address _old, address _new);
    event VoterChanged(address indexed whom, address _old, address _new);
    event LockerChanged(address indexed whom, address _old, address _new);
    event GovernorChanged(address indexed whom, address _old, address _new);
    event StakerChanged(address indexed whom, address _old, address _new);
    event EmissionControllerChanged(
        address indexed whom,
        address _old,
        address _new
    );

    function maha() external view returns (address);

    function gaugeVoter() external view returns (address);

    function locker() external view returns (address);

    function staker() external view returns (address);

    function emissionController() external view returns (address);

    function governor() external view returns (address);

    function getAllAddresses()
        external
        view
        returns (
            address,
            address,
            address,
            address,
            address
        );

    function ensureNotPaused() external;

    function setMAHA(address _new) external;

    function setEmissionController(address _new) external;

    function setStaker(address _new) external;

    function setVoter(address _new) external;

    function setLocker(address _new) external;

    function setGovernor(address _new) external;
}

// File: contracts/interfaces/IEmissionController.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import {IEpoch} from "./IEpoch.sol";

interface IEmissionController is IEpoch {
    function allocateEmission() external;
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);

    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `from` to `to` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) external returns (bool);
}

// File: @openzeppelin/contracts/utils/math/SafeMath.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (utils/math/SafeMath.sol)

pragma solidity ^0.8.0;

// CAUTION
// This version of SafeMath should only be used with Solidity 0.8 or later,
// because it relies on the compiler's built in overflow checks.

/**
 * @dev Wrappers over Solidity's arithmetic operations.
 *
 * NOTE: `SafeMath` is generally not needed starting with Solidity 0.8, since the compiler
 * now has built in overflow checking.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            uint256 c = a + b;
            if (c < a) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b > a) return (false, 0);
            return (true, a - b);
        }
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
            // benefit is lost if 'b' is also tested.
            // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
            if (a == 0) return (true, 0);
            uint256 c = a * b;
            if (c / a != b) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a / b);
        }
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a % b);
        }
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        return a + b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        return a * b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator.
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b <= a, errorMessage);
            return a - b;
        }
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a / b;
        }
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a % b;
        }
    }
}

// File: contracts/utils/Operator.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import {Context, Ownable} from "@openzeppelin/contracts/access/Ownable.sol";

abstract contract Operator is Context, Ownable {
  address private _operator;

  event OperatorTransferred(
    address indexed previousOperator,
    address indexed newOperator
  );

  constructor() {
    _operator = _msgSender();
    emit OperatorTransferred(address(0), _operator);
  }

  function operator() public view returns (address) {
    return _operator;
  }

  modifier onlyOperator() {
    require(_operator == _msgSender(), "operator: caller is not the operator");
    _;
  }

  function isOperator() public view returns (bool) {
    return _msgSender() == _operator;
  }

  function transferOperator(address newOperator_) public onlyOwner {
    _transferOperator(newOperator_);
  }

  function _transferOperator(address newOperator_) internal {
    require(
      newOperator_ != address(0),
      "operator: zero address given for new operator"
    );
    emit OperatorTransferred(address(0), newOperator_);
    _operator = newOperator_;
  }
}

// File: contracts/interfaces/IEpoch.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

interface IEpoch {
  function callable() external view returns (bool);

  function getLastEpoch() external view returns (uint256);

  function getCurrentEpoch() external view returns (uint256);

  function getNextEpoch() external view returns (uint256);

  function nextEpochPoint() external view returns (uint256);

  function getPeriod() external view returns (uint256);

  function getStartTime() external view returns (uint256);
}

// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (access/Ownable.sol)

pragma solidity ^0.8.0;

import "../utils/Context.sol";

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

// File: @openzeppelin/contracts/utils/Context.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^0.8.0;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

// File: @openzeppelin/contracts/access/IAccessControl.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (access/IAccessControl.sol)

pragma solidity ^0.8.0;

/**
 * @dev External interface of AccessControl declared to support ERC165 detection.
 */
interface IAccessControl {
    /**
     * @dev Emitted when `newAdminRole` is set as ``role``'s admin role, replacing `previousAdminRole`
     *
     * `DEFAULT_ADMIN_ROLE` is the starting admin for all roles, despite
     * {RoleAdminChanged} not being emitted signaling this.
     *
     * _Available since v3.1._
     */
    event RoleAdminChanged(bytes32 indexed role, bytes32 indexed previousAdminRole, bytes32 indexed newAdminRole);

    /**
     * @dev Emitted when `account` is granted `role`.
     *
     * `sender` is the account that originated the contract call, an admin role
     * bearer except when using {AccessControl-_setupRole}.
     */
    event RoleGranted(bytes32 indexed role, address indexed account, address indexed sender);

    /**
     * @dev Emitted when `account` is revoked `role`.
     *
     * `sender` is the account that originated the contract call:
     *   - if using `revokeRole`, it is the admin role bearer
     *   - if using `renounceRole`, it is the role bearer (i.e. `account`)
     */
    event RoleRevoked(bytes32 indexed role, address indexed account, address indexed sender);

    /**
     * @dev Returns `true` if `account` has been granted `role`.
     */
    function hasRole(bytes32 role, address account) external view returns (bool);

    /**
     * @dev Returns the admin role that controls `role`. See {grantRole} and
     * {revokeRole}.
     *
     * To change a role's admin, use {AccessControl-_setRoleAdmin}.
     */
    function getRoleAdmin(bytes32 role) external view returns (bytes32);

    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function grantRole(bytes32 role, address account) external;

    /**
     * @dev Revokes `role` from `account`.
     *
     * If `account` had been granted `role`, emits a {RoleRevoked} event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function revokeRole(bytes32 role, address account) external;

    /**
     * @dev Revokes `role` from the calling account.
     *
     * Roles are often managed via {grantRole} and {revokeRole}: this function's
     * purpose is to provide a mechanism for accounts to lose their privileges
     * if they are compromised (such as when a trusted device is misplaced).
     *
     * If the calling account had been granted `role`, emits a {RoleRevoked}
     * event.
     *
     * Requirements:
     *
     * - the caller must be `account`.
     */
    function renounceRole(bytes32 role, address account) external;
}