// File: ./contracts/oracle/OraclePassThrough.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity ^0.8.4;

import {Decimal} from "../external/Decimal.sol";
import {CoreRef} from "./../refs/CoreRef.sol";
import {IScalingPriceOracle} from "./IScalingPriceOracle.sol";
import {IOraclePassThrough} from "./IOraclePassThrough.sol";
import {Ownable} from "@openzeppelin/contracts/access/Ownable.sol";

/// @notice contract that passes all price calls to the Scaling Price Oracle
/// The Scaling Price Oracle can be changed if there is a decision to change how data is interpolated
/// without needing all contracts in the system to be upgraded, only this contract will have to change where it points
/// @author Elliot Friedman
contract OraclePassThrough is IOraclePassThrough, Ownable {
    using Decimal for Decimal.D256;

    /// @notice reference to the scaling price oracle
    IScalingPriceOracle public override scalingPriceOracle;

    constructor(IScalingPriceOracle _scalingPriceOracle) Ownable() {
        scalingPriceOracle = _scalingPriceOracle;
    }

    /// @notice updates the oracle price
    /// @dev no-op, ScalingPriceOracle is updated automatically
    /// added for backwards compatibility with OracleRef
    function update() public {}

    // ----------- Getters -----------

    /// @notice function to get the current oracle price for the OracleRef contract
    function read()
        external
        view
        override
        returns (Decimal.D256 memory price, bool valid)
    {
        uint256 currentPrice = scalingPriceOracle.getCurrentOraclePrice();

        price = Decimal.from(currentPrice).div(1e18);
        valid = true;
    }

    /// @notice function to get the current oracle price for the entire system
    function getCurrentOraclePrice() external view override returns (uint256) {
        return scalingPriceOracle.getCurrentOraclePrice();
    }

    /// @notice function to get the current oracle price for the entire system
    function currPegPrice() external view override returns (uint256) {
        return scalingPriceOracle.getCurrentOraclePrice();
    }

    // ----------- Governance only state changing api -----------

    /// @notice function to update the pointer to the scaling price oracle
    /// requires approval from all parties on multisig to update
    function updateScalingPriceOracle(IScalingPriceOracle newScalingPriceOracle)
        external
        override
        onlyOwner
    {
        IScalingPriceOracle oldScalingPriceOracle = scalingPriceOracle;
        scalingPriceOracle = newScalingPriceOracle;

        emit ScalingPriceOracleUpdate(
            oldScalingPriceOracle,
            newScalingPriceOracle
        );
    }
}

// File: ./contracts/external/Decimal.sol



/*
    Copyright 2019 dYdX Trading Inc.
    Copyright 2020 Empty Set Squad <emptysetsquad@protonmail.com>
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at
    http://www.apache.org/licenses/LICENSE-2.0
    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
*/

pragma solidity ^0.8.4;

import "@openzeppelin/contracts/utils/math/SafeMath.sol";

/**
 * @title Decimal
 * @author dYdX
 *
 * Library that defines a fixed-point number with 18 decimal places.
 */
library Decimal {
    using SafeMath for uint256;

    // ============ Constants ============

    uint256 private constant BASE = 10**18;

    // ============ Structs ============

    struct D256 {
        uint256 value;
    }

    // ============ Static Functions ============

    function zero() internal pure returns (D256 memory) {
        return D256({value: 0});
    }

    function one() internal pure returns (D256 memory) {
        return D256({value: BASE});
    }

    function from(uint256 a) internal pure returns (D256 memory) {
        return D256({value: a.mul(BASE)});
    }

    function ratio(uint256 a, uint256 b) internal pure returns (D256 memory) {
        return D256({value: getPartial(a, BASE, b)});
    }

    // ============ Self Functions ============

    function add(D256 memory self, uint256 b)
        internal
        pure
        returns (D256 memory)
    {
        return D256({value: self.value.add(b.mul(BASE))});
    }

    function sub(D256 memory self, uint256 b)
        internal
        pure
        returns (D256 memory)
    {
        return D256({value: self.value.sub(b.mul(BASE))});
    }

    function sub(
        D256 memory self,
        uint256 b,
        string memory reason
    ) internal pure returns (D256 memory) {
        return D256({value: self.value.sub(b.mul(BASE), reason)});
    }

    function mul(D256 memory self, uint256 b)
        internal
        pure
        returns (D256 memory)
    {
        return D256({value: self.value.mul(b)});
    }

    function div(D256 memory self, uint256 b)
        internal
        pure
        returns (D256 memory)
    {
        return D256({value: self.value.div(b)});
    }

    function pow(D256 memory self, uint256 b)
        internal
        pure
        returns (D256 memory)
    {
        if (b == 0) {
            return from(1);
        }

        D256 memory temp = D256({value: self.value});
        for (uint256 i = 1; i < b; i++) {
            temp = mul(temp, self);
        }

        return temp;
    }

    function add(D256 memory self, D256 memory b)
        internal
        pure
        returns (D256 memory)
    {
        return D256({value: self.value.add(b.value)});
    }

    function sub(D256 memory self, D256 memory b)
        internal
        pure
        returns (D256 memory)
    {
        return D256({value: self.value.sub(b.value)});
    }

    function sub(
        D256 memory self,
        D256 memory b,
        string memory reason
    ) internal pure returns (D256 memory) {
        return D256({value: self.value.sub(b.value, reason)});
    }

    function mul(D256 memory self, D256 memory b)
        internal
        pure
        returns (D256 memory)
    {
        return D256({value: getPartial(self.value, b.value, BASE)});
    }

    function div(D256 memory self, D256 memory b)
        internal
        pure
        returns (D256 memory)
    {
        return D256({value: getPartial(self.value, BASE, b.value)});
    }

    function equals(D256 memory self, D256 memory b)
        internal
        pure
        returns (bool)
    {
        return self.value == b.value;
    }

    function greaterThan(D256 memory self, D256 memory b)
        internal
        pure
        returns (bool)
    {
        return compareTo(self, b) == 2;
    }

    function lessThan(D256 memory self, D256 memory b)
        internal
        pure
        returns (bool)
    {
        return compareTo(self, b) == 0;
    }

    function greaterThanOrEqualTo(D256 memory self, D256 memory b)
        internal
        pure
        returns (bool)
    {
        return compareTo(self, b) > 0;
    }

    function lessThanOrEqualTo(D256 memory self, D256 memory b)
        internal
        pure
        returns (bool)
    {
        return compareTo(self, b) < 2;
    }

    function isZero(D256 memory self) internal pure returns (bool) {
        return self.value == 0;
    }

    function asUint256(D256 memory self) internal pure returns (uint256) {
        return self.value.div(BASE);
    }

    // ============ Core Methods ============

    function getPartial(
        uint256 target,
        uint256 numerator,
        uint256 denominator
    ) private pure returns (uint256) {
        return target.mul(numerator).div(denominator);
    }

    function compareTo(D256 memory a, D256 memory b)
        private
        pure
        returns (uint256)
    {
        if (a.value == b.value) {
            return 1;
        }
        return a.value > b.value ? 2 : 0;
    }
}

// File: ./contracts/refs/CoreRef.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity ^0.8.4;

import "./ICoreRef.sol";
import "@openzeppelin/contracts/security/Pausable.sol";

/// @title A Reference to Core
/// @author Fei Protocol
/// @notice defines some modifiers and utilities around interacting with Core
abstract contract CoreRef is ICoreRef, Pausable {
    ICore private immutable _core;
    IVolt private immutable _volt;
    IERC20 private immutable _vcon;

    /// @notice a role used with a subset of governor permissions for this contract only
    bytes32 public override CONTRACT_ADMIN_ROLE;

    constructor(address coreAddress) {
        _core = ICore(coreAddress);

        _volt = ICore(coreAddress).volt();
        _vcon = ICore(coreAddress).vcon();

        _setContractAdminRole(ICore(coreAddress).GOVERN_ROLE());
    }

    function _initialize() internal {} // no-op for backward compatibility

    modifier ifMinterSelf() {
        if (_core.isMinter(address(this))) {
            _;
        }
    }

    modifier onlyMinter() {
        require(_core.isMinter(msg.sender), "CoreRef: Caller is not a minter");
        _;
    }

    modifier onlyBurner() {
        require(_core.isBurner(msg.sender), "CoreRef: Caller is not a burner");
        _;
    }

    modifier onlyPCVController() {
        require(
            _core.isPCVController(msg.sender),
            "CoreRef: Caller is not a PCV controller"
        );
        _;
    }

    modifier onlyGovernorOrAdmin() {
        require(
            _core.isGovernor(msg.sender) || isContractAdmin(msg.sender),
            "CoreRef: Caller is not a governor or contract admin"
        );
        _;
    }

    modifier onlyGovernor() {
        require(
            _core.isGovernor(msg.sender),
            "CoreRef: Caller is not a governor"
        );
        _;
    }

    modifier onlyGuardianOrGovernor() {
        require(
            _core.isGovernor(msg.sender) || _core.isGuardian(msg.sender),
            "CoreRef: Caller is not a guardian or governor"
        );
        _;
    }

    modifier onlyGovernorOrGuardianOrAdmin() {
        require(
            _core.isGovernor(msg.sender) ||
                _core.isGuardian(msg.sender) ||
                isContractAdmin(msg.sender),
            "CoreRef: Caller is not governor or guardian or admin"
        );
        _;
    }

    // Named onlyTribeRole to prevent collision with OZ onlyRole modifier
    modifier onlyTribeRole(bytes32 role) {
        require(_core.hasRole(role, msg.sender), "UNAUTHORIZED");
        _;
    }

    // Modifiers to allow any combination of roles
    modifier hasAnyOfTwoRoles(bytes32 role1, bytes32 role2) {
        require(
            _core.hasRole(role1, msg.sender) ||
                _core.hasRole(role2, msg.sender),
            "UNAUTHORIZED"
        );
        _;
    }

    modifier hasAnyOfThreeRoles(
        bytes32 role1,
        bytes32 role2,
        bytes32 role3
    ) {
        require(
            _core.hasRole(role1, msg.sender) ||
                _core.hasRole(role2, msg.sender) ||
                _core.hasRole(role3, msg.sender),
            "UNAUTHORIZED"
        );
        _;
    }

    modifier hasAnyOfFourRoles(
        bytes32 role1,
        bytes32 role2,
        bytes32 role3,
        bytes32 role4
    ) {
        require(
            _core.hasRole(role1, msg.sender) ||
                _core.hasRole(role2, msg.sender) ||
                _core.hasRole(role3, msg.sender) ||
                _core.hasRole(role4, msg.sender),
            "UNAUTHORIZED"
        );
        _;
    }

    modifier hasAnyOfFiveRoles(
        bytes32 role1,
        bytes32 role2,
        bytes32 role3,
        bytes32 role4,
        bytes32 role5
    ) {
        require(
            _core.hasRole(role1, msg.sender) ||
                _core.hasRole(role2, msg.sender) ||
                _core.hasRole(role3, msg.sender) ||
                _core.hasRole(role4, msg.sender) ||
                _core.hasRole(role5, msg.sender),
            "UNAUTHORIZED"
        );
        _;
    }

    modifier onlyVolt() {
        require(msg.sender == address(_volt), "CoreRef: Caller is not VOLT");
        _;
    }

    /// @notice sets a new admin role for this contract
    function setContractAdminRole(bytes32 newContractAdminRole)
        external
        override
        onlyGovernor
    {
        _setContractAdminRole(newContractAdminRole);
    }

    /// @notice returns whether a given address has the admin role for this contract
    function isContractAdmin(address _admin)
        public
        view
        override
        returns (bool)
    {
        return _core.hasRole(CONTRACT_ADMIN_ROLE, _admin);
    }

    /// @notice set pausable methods to paused
    function pause() public override onlyGuardianOrGovernor {
        _pause();
    }

    /// @notice set pausable methods to unpaused
    function unpause() public override onlyGuardianOrGovernor {
        _unpause();
    }

    /// @notice address of the Core contract referenced
    /// @return ICore implementation address
    function core() public view override returns (ICore) {
        return _core;
    }

    /// @notice address of the Fei contract referenced by Core
    /// @return IFei implementation address
    function volt() public view override returns (IVolt) {
        return _volt;
    }

    /// @notice address of the Tribe contract referenced by Core
    /// @return IERC20 implementation address
    function vcon() public view override returns (IERC20) {
        return _vcon;
    }

    /// @notice volt balance of contract
    /// @return volt amount held
    function voltBalance() public view override returns (uint256) {
        return _volt.balanceOf(address(this));
    }

    /// @notice vcon balance of contract
    /// @return vcon amount held
    function vconBalance() public view override returns (uint256) {
        return _vcon.balanceOf(address(this));
    }

    function _burnVoltHeld() internal {
        _volt.burn(voltBalance());
    }

    function _mintVolt(address to, uint256 amount) internal virtual {
        if (amount != 0) {
            _volt.mint(to, amount);
        }
    }

    function _setContractAdminRole(bytes32 newContractAdminRole) internal {
        bytes32 oldContractAdminRole = CONTRACT_ADMIN_ROLE;
        CONTRACT_ADMIN_ROLE = newContractAdminRole;
        emit ContractAdminRoleUpdate(
            oldContractAdminRole,
            newContractAdminRole
        );
    }
}

// File: ./contracts/refs/ICoreRef.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity ^0.8.4;

import "../core/ICore.sol";

/// @title CoreRef interface
/// @author Fei Protocol
interface ICoreRef {
    // ----------- Events -----------

    event CoreUpdate(address indexed oldCore, address indexed newCore);

    event ContractAdminRoleUpdate(
        bytes32 indexed oldContractAdminRole,
        bytes32 indexed newContractAdminRole
    );

    // ----------- Governor only state changing api -----------

    function setContractAdminRole(bytes32 newContractAdminRole) external;

    // ----------- Governor or Guardian only state changing api -----------

    function pause() external;

    function unpause() external;

    // ----------- Getters -----------

    function core() external view returns (ICore);

    function volt() external view returns (IVolt);

    function vcon() external view returns (IERC20);

    function voltBalance() external view returns (uint256);

    function vconBalance() external view returns (uint256);

    function CONTRACT_ADMIN_ROLE() external view returns (bytes32);

    function isContractAdmin(address admin) external view returns (bool);
}

// File: ./contracts/core/ICore.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity ^0.8.4;

import {IPermissions} from "./IPermissions.sol";
import {IVolt, IERC20} from "../volt/IVolt.sol";

/// @title Core Interface
/// @author Fei Protocol
interface ICore is IPermissions {
    // ----------- Events -----------
    event VoltUpdate(IERC20 indexed _volt);
    event VconUpdate(IERC20 indexed _vcon);

    // ----------- Getters -----------

    function volt() external view returns (IVolt);

    function vcon() external view returns (IERC20);
}

// File: ./contracts/core/IPermissions.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity ^0.8.4;

import "@openzeppelin/contracts/access/AccessControl.sol";
import "./IPermissionsRead.sol";

/// @title Permissions interface
/// @author Fei Protocol
interface IPermissions is IAccessControl, IPermissionsRead {
    // ----------- Governor only state changing api -----------

    function createRole(bytes32 role, bytes32 adminRole) external;

    function grantMinter(address minter) external;

    function grantBurner(address burner) external;

    function grantPCVController(address pcvController) external;

    function grantGovernor(address governor) external;

    function grantGuardian(address guardian) external;

    function revokeMinter(address minter) external;

    function revokeBurner(address burner) external;

    function revokePCVController(address pcvController) external;

    function revokeGovernor(address governor) external;

    function revokeGuardian(address guardian) external;

    // ----------- Revoker only state changing api -----------

    function revokeOverride(bytes32 role, address account) external;

    // ----------- Getters -----------

    function GUARDIAN_ROLE() external view returns (bytes32);

    function GOVERN_ROLE() external view returns (bytes32);

    function BURNER_ROLE() external view returns (bytes32);

    function MINTER_ROLE() external view returns (bytes32);

    function PCV_CONTROLLER_ROLE() external view returns (bytes32);
}

// File: ./contracts/core/IPermissionsRead.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity ^0.8.4;

/// @title Permissions Read interface
/// @author Fei Protocol
interface IPermissionsRead {
    // ----------- Getters -----------

    function isBurner(address _address) external view returns (bool);

    function isMinter(address _address) external view returns (bool);

    function isGovernor(address _address) external view returns (bool);

    function isGuardian(address _address) external view returns (bool);

    function isPCVController(address _address) external view returns (bool);
}

// File: ./contracts/volt/IVolt.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity ^0.8.4;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

/// @title FEI stablecoin interface
/// @author Fei Protocol
interface IVolt is IERC20 {
    // ----------- Events -----------

    event Minting(
        address indexed _to,
        address indexed _minter,
        uint256 _amount
    );

    event Burning(
        address indexed _to,
        address indexed _burner,
        uint256 _amount
    );

    event IncentiveContractUpdate(
        address indexed _incentivized,
        address indexed _incentiveContract
    );

    // ----------- State changing api -----------

    function burn(uint256 amount) external;

    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    // ----------- Minter only state changing api -----------

    function mint(address account, uint256 amount) external;
}

// File: ./contracts/oracle/IScalingPriceOracle.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity ^0.8.4;

import {Decimal} from "../external/Decimal.sol";

/// @notice contract that receives a chainlink price feed and then linearly interpolates that rate over
/// a 1 month period into the VOLT price. Interest is compounded monthly when the rate is updated
/// @author Elliot Friedman
interface IScalingPriceOracle {
    /// @notice the time frame over which all changes in CPI data are applied
    /// 28 days was chosen as that is the shortest length of a month
    function TIMEFRAME() external view returns (uint256);

    /// @notice the maximum allowable deviation in basis points for a new chainlink oracle update
    /// only allow price changes by 20% in a month.
    /// Any change over this threshold in either direction will be rejected
    function MAXORACLEDEVIATION() external view returns (uint256);

    /// @notice get the current scaled oracle price
    /// applies the change smoothly over a 28 day period
    /// scaled by 18 decimals
    function getCurrentOraclePrice() external view returns (uint256);

    /// @notice current amount that oracle price is inflating/deflating by monthly in basis points
    function monthlyChangeRateBasisPoints() external view returns (int256);

    /// @notice oracle price. starts off at 1 scaled up by 18 decimals
    function oraclePrice() external view returns (uint256);

    /// @notice event when the monthly change rate is updated
    event CPIMonthlyChangeRateUpdate(
        int256 oldChangeRateBasisPoints,
        int256 newChangeRateBasisPoints
    );
}

// File: ./contracts/oracle/IOraclePassThrough.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity ^0.8.4;

import {Decimal} from "../external/Decimal.sol";
import {IScalingPriceOracle} from "./IScalingPriceOracle.sol";

/// @notice interface to get data from the Scaling Price Oracle
interface IOraclePassThrough {
    // ----------- Getters -----------

    /// @notice reference to the scaling price oracle
    function scalingPriceOracle() external view returns (IScalingPriceOracle);

    /// @notice function to get the current oracle price for the OracleRef contract
    function read()
        external
        view
        returns (Decimal.D256 memory price, bool valid);

    /// @notice function to get the current oracle price for the entire system
    function getCurrentOraclePrice() external view returns (uint256);

    /// @notice function to get the current oracle price for the entire system
    function currPegPrice() external view returns (uint256);

    // ----------- Governor only state changing api -----------

    /// @notice function to update the pointer to the scaling price oracle
    /// requires approval from both VOLT and FRAX governance to sign off on the change
    function updateScalingPriceOracle(IScalingPriceOracle newScalingPriceOracle)
        external;

    /// @notice event emitted when the scaling price oracle is updated
    event ScalingPriceOracleUpdate(
        IScalingPriceOracle oldScalingPriceOracle,
        IScalingPriceOracle newScalingPriceOracle
    );
}

// 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/utils/math/SafeMath.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (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 substraction 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: @openzeppelin/contracts/security/Pausable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (security/Pausable.sol)

pragma solidity ^0.8.0;

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

/**
 * @dev Contract module which allows children to implement an emergency stop
 * mechanism that can be triggered by an authorized account.
 *
 * This module is used through inheritance. It will make available the
 * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
 * the functions of your contract. Note that they will not be pausable by
 * simply including this module, only once the modifiers are put in place.
 */
abstract contract Pausable is Context {
    /**
     * @dev Emitted when the pause is triggered by `account`.
     */
    event Paused(address account);

    /**
     * @dev Emitted when the pause is lifted by `account`.
     */
    event Unpaused(address account);

    bool private _paused;

    /**
     * @dev Initializes the contract in unpaused state.
     */
    constructor() {
        _paused = false;
    }

    /**
     * @dev Returns true if the contract is paused, and false otherwise.
     */
    function paused() public view virtual returns (bool) {
        return _paused;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    modifier whenNotPaused() {
        require(!paused(), "Pausable: paused");
        _;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    modifier whenPaused() {
        require(paused(), "Pausable: not paused");
        _;
    }

    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    function _pause() internal virtual whenNotPaused {
        _paused = true;
        emit Paused(_msgSender());
    }

    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    function _unpause() internal virtual whenPaused {
        _paused = false;
        emit Unpaused(_msgSender());
    }
}

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



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

pragma solidity ^0.8.0;

import "./IAccessControl.sol";
import "../utils/Context.sol";
import "../utils/Strings.sol";
import "../utils/introspection/ERC165.sol";

/**
 * @dev Contract module that allows children to implement role-based access
 * control mechanisms. This is a lightweight version that doesn't allow enumerating role
 * members except through off-chain means by accessing the contract event logs. Some
 * applications may benefit from on-chain enumerability, for those cases see
 * {AccessControlEnumerable}.
 *
 * Roles are referred to by their `bytes32` identifier. These should be exposed
 * in the external API and be unique. The best way to achieve this is by
 * using `public constant` hash digests:
 *
 * ```
 * bytes32 public constant MY_ROLE = keccak256("MY_ROLE");
 * ```
 *
 * Roles can be used to represent a set of permissions. To restrict access to a
 * function call, use {hasRole}:
 *
 * ```
 * function foo() public {
 *     require(hasRole(MY_ROLE, msg.sender));
 *     ...
 * }
 * ```
 *
 * Roles can be granted and revoked dynamically via the {grantRole} and
 * {revokeRole} functions. Each role has an associated admin role, and only
 * accounts that have a role's admin role can call {grantRole} and {revokeRole}.
 *
 * By default, the admin role for all roles is `DEFAULT_ADMIN_ROLE`, which means
 * that only accounts with this role will be able to grant or revoke other
 * roles. More complex role relationships can be created by using
 * {_setRoleAdmin}.
 *
 * WARNING: The `DEFAULT_ADMIN_ROLE` is also its own admin: it has permission to
 * grant and revoke this role. Extra precautions should be taken to secure
 * accounts that have been granted it.
 */
abstract contract AccessControl is Context, IAccessControl, ERC165 {
    struct RoleData {
        mapping(address => bool) members;
        bytes32 adminRole;
    }

    mapping(bytes32 => RoleData) private _roles;

    bytes32 public constant DEFAULT_ADMIN_ROLE = 0x00;

    /**
     * @dev Modifier that checks that an account has a specific role. Reverts
     * with a standardized message including the required role.
     *
     * The format of the revert reason is given by the following regular expression:
     *
     *  /^AccessControl: account (0x[0-9a-f]{40}) is missing role (0x[0-9a-f]{64})$/
     *
     * _Available since v4.1._
     */
    modifier onlyRole(bytes32 role) {
        _checkRole(role, _msgSender());
        _;
    }

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

    /**
     * @dev Returns `true` if `account` has been granted `role`.
     */
    function hasRole(bytes32 role, address account) public view override returns (bool) {
        return _roles[role].members[account];
    }

    /**
     * @dev Revert with a standard message if `account` is missing `role`.
     *
     * The format of the revert reason is given by the following regular expression:
     *
     *  /^AccessControl: account (0x[0-9a-f]{40}) is missing role (0x[0-9a-f]{64})$/
     */
    function _checkRole(bytes32 role, address account) internal view {
        if (!hasRole(role, account)) {
            revert(
                string(
                    abi.encodePacked(
                        "AccessControl: account ",
                        Strings.toHexString(uint160(account), 20),
                        " is missing role ",
                        Strings.toHexString(uint256(role), 32)
                    )
                )
            );
        }
    }

    /**
     * @dev Returns the admin role that controls `role`. See {grantRole} and
     * {revokeRole}.
     *
     * To change a role's admin, use {_setRoleAdmin}.
     */
    function getRoleAdmin(bytes32 role) public view override returns (bytes32) {
        return _roles[role].adminRole;
    }

    /**
     * @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) public virtual override onlyRole(getRoleAdmin(role)) {
        _grantRole(role, account);
    }

    /**
     * @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) public virtual override onlyRole(getRoleAdmin(role)) {
        _revokeRole(role, account);
    }

    /**
     * @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 revoked `role`, emits a {RoleRevoked}
     * event.
     *
     * Requirements:
     *
     * - the caller must be `account`.
     */
    function renounceRole(bytes32 role, address account) public virtual override {
        require(account == _msgSender(), "AccessControl: can only renounce roles for self");

        _revokeRole(role, account);
    }

    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event. Note that unlike {grantRole}, this function doesn't perform any
     * checks on the calling account.
     *
     * [WARNING]
     * ====
     * This function should only be called from the constructor when setting
     * up the initial roles for the system.
     *
     * Using this function in any other way is effectively circumventing the admin
     * system imposed by {AccessControl}.
     * ====
     *
     * NOTE: This function is deprecated in favor of {_grantRole}.
     */
    function _setupRole(bytes32 role, address account) internal virtual {
        _grantRole(role, account);
    }

    /**
     * @dev Sets `adminRole` as ``role``'s admin role.
     *
     * Emits a {RoleAdminChanged} event.
     */
    function _setRoleAdmin(bytes32 role, bytes32 adminRole) internal virtual {
        bytes32 previousAdminRole = getRoleAdmin(role);
        _roles[role].adminRole = adminRole;
        emit RoleAdminChanged(role, previousAdminRole, adminRole);
    }

    /**
     * @dev Grants `role` to `account`.
     *
     * Internal function without access restriction.
     */
    function _grantRole(bytes32 role, address account) internal virtual {
        if (!hasRole(role, account)) {
            _roles[role].members[account] = true;
            emit RoleGranted(role, account, _msgSender());
        }
    }

    /**
     * @dev Revokes `role` from `account`.
     *
     * Internal function without access restriction.
     */
    function _revokeRole(bytes32 role, address account) internal virtual {
        if (hasRole(role, account)) {
            _roles[role].members[account] = false;
            emit RoleRevoked(role, account, _msgSender());
        }
    }
}

// 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;
}

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



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

pragma solidity ^0.8.0;

/**
 * @dev String operations.
 */
library Strings {
    bytes16 private constant _HEX_SYMBOLS = "0123456789abcdef";

    /**
     * @dev Converts a `uint256` to its ASCII `string` decimal representation.
     */
    function toString(uint256 value) internal pure returns (string memory) {
        // Inspired by OraclizeAPI's implementation - MIT licence
        // https://github.com/oraclize/ethereum-api/blob/b42146b063c7d6ee1358846c198246239e9360e8/oraclizeAPI_0.4.25.sol

        if (value == 0) {
            return "0";
        }
        uint256 temp = value;
        uint256 digits;
        while (temp != 0) {
            digits++;
            temp /= 10;
        }
        bytes memory buffer = new bytes(digits);
        while (value != 0) {
            digits -= 1;
            buffer[digits] = bytes1(uint8(48 + uint256(value % 10)));
            value /= 10;
        }
        return string(buffer);
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
     */
    function toHexString(uint256 value) internal pure returns (string memory) {
        if (value == 0) {
            return "0x00";
        }
        uint256 temp = value;
        uint256 length = 0;
        while (temp != 0) {
            length++;
            temp >>= 8;
        }
        return toHexString(value, length);
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation with fixed length.
     */
    function toHexString(uint256 value, uint256 length) internal pure returns (string memory) {
        bytes memory buffer = new bytes(2 * length + 2);
        buffer[0] = "0";
        buffer[1] = "x";
        for (uint256 i = 2 * length + 1; i > 1; --i) {
            buffer[i] = _HEX_SYMBOLS[value & 0xf];
            value >>= 4;
        }
        require(value == 0, "Strings: hex length insufficient");
        return string(buffer);
    }
}

// File: @openzeppelin/contracts/utils/introspection/ERC165.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/introspection/ERC165.sol)

pragma solidity ^0.8.0;

import "./IERC165.sol";

/**
 * @dev Implementation of the {IERC165} interface.
 *
 * Contracts that want to implement ERC165 should inherit from this contract and override {supportsInterface} to check
 * for the additional interface id that will be supported. For example:
 *
 * ```solidity
 * function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
 *     return interfaceId == type(MyInterface).interfaceId || super.supportsInterface(interfaceId);
 * }
 * ```
 *
 * Alternatively, {ERC165Storage} provides an easier to use but more expensive implementation.
 */
abstract contract ERC165 is IERC165 {
    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return interfaceId == type(IERC165).interfaceId;
    }
}

// File: @openzeppelin/contracts/utils/introspection/IERC165.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/introspection/IERC165.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
interface IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @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 `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, 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 `sender` to `recipient` 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 sender,
        address recipient,
        uint256 amount
    ) external returns (bool);

    /**
     * @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);
}