Contract Address Details

// Sources flattened with hardhat v2.19.2 https://hardhat.org

// SPDX-License-Identifier: MIT

// File @openzeppelin/contracts-upgradeable/utils/[email protected]

// Original license: SPDX_License_Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (utils/Address.sol)

pragma solidity ^0.8.1;

/**
 * @dev Collection of functions related to the address type
 */
library AddressUpgradeable {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     *
     * Furthermore, `isContract` will also return true if the target contract within
     * the same transaction is already scheduled for destruction by `SELFDESTRUCT`,
     * which only has an effect at the end of a transaction.
     * ====
     *
     * [IMPORTANT]
     * ====
     * You shouldn't rely on `isContract` to protect against flash loan attacks!
     *
     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
     * constructor.
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize/address.code.length, which returns 0
        // for contracts in construction, since the code is only stored at the end
        // of the constructor execution.

        return account.code.length > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://consensys.net/diligence/blog/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.8.0/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        (bool success, ) = recipient.call{value: amount}("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain `call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verify that a low level call to smart-contract was successful, and revert (either by bubbling
     * the revert reason or using the provided one) in case of unsuccessful call or if target was not a contract.
     *
     * _Available since v4.8._
     */
    function verifyCallResultFromTarget(
        address target,
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        if (success) {
            if (returndata.length == 0) {
                // only check isContract if the call was successful and the return data is empty
                // otherwise we already know that it was a contract
                require(isContract(target), "Address: call to non-contract");
            }
            return returndata;
        } else {
            _revert(returndata, errorMessage);
        }
    }

    /**
     * @dev Tool to verify that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason or using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            _revert(returndata, errorMessage);
        }
    }

    function _revert(bytes memory returndata, string memory errorMessage) private pure {
        // Look for revert reason and bubble it up if present
        if (returndata.length > 0) {
            // The easiest way to bubble the revert reason is using memory via assembly
            /// @solidity memory-safe-assembly
            assembly {
                let returndata_size := mload(returndata)
                revert(add(32, returndata), returndata_size)
            }
        } else {
            revert(errorMessage);
        }
    }
}


// File @openzeppelin/contracts-upgradeable/proxy/utils/[email protected]

// Original license: SPDX_License_Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (proxy/utils/Initializable.sol)

pragma solidity ^0.8.2;

/**
 * @dev This is a base contract to aid in writing upgradeable contracts, or any kind of contract that will be deployed
 * behind a proxy. Since proxied contracts do not make use of a constructor, it's common to move constructor logic to an
 * external initializer function, usually called `initialize`. It then becomes necessary to protect this initializer
 * function so it can only be called once. The {initializer} modifier provided by this contract will have this effect.
 *
 * The initialization functions use a version number. Once a version number is used, it is consumed and cannot be
 * reused. This mechanism prevents re-execution of each "step" but allows the creation of new initialization steps in
 * case an upgrade adds a module that needs to be initialized.
 *
 * For example:
 *
 * [.hljs-theme-light.nopadding]
 * ```solidity
 * contract MyToken is ERC20Upgradeable {
 *     function initialize() initializer public {
 *         __ERC20_init("MyToken", "MTK");
 *     }
 * }
 *
 * contract MyTokenV2 is MyToken, ERC20PermitUpgradeable {
 *     function initializeV2() reinitializer(2) public {
 *         __ERC20Permit_init("MyToken");
 *     }
 * }
 * ```
 *
 * TIP: To avoid leaving the proxy in an uninitialized state, the initializer function should be called as early as
 * possible by providing the encoded function call as the `_data` argument to {ERC1967Proxy-constructor}.
 *
 * CAUTION: When used with inheritance, manual care must be taken to not invoke a parent initializer twice, or to ensure
 * that all initializers are idempotent. This is not verified automatically as constructors are by Solidity.
 *
 * [CAUTION]
 * ====
 * Avoid leaving a contract uninitialized.
 *
 * An uninitialized contract can be taken over by an attacker. This applies to both a proxy and its implementation
 * contract, which may impact the proxy. To prevent the implementation contract from being used, you should invoke
 * the {_disableInitializers} function in the constructor to automatically lock it when it is deployed:
 *
 * [.hljs-theme-light.nopadding]
 * ```
 * /// @custom:oz-upgrades-unsafe-allow constructor
 * constructor() {
 *     _disableInitializers();
 * }
 * ```
 * ====
 */
abstract contract Initializable {
    /**
     * @dev Indicates that the contract has been initialized.
     * @custom:oz-retyped-from bool
     */
    uint8 private _initialized;

    /**
     * @dev Indicates that the contract is in the process of being initialized.
     */
    bool private _initializing;

    /**
     * @dev Triggered when the contract has been initialized or reinitialized.
     */
    event Initialized(uint8 version);

    /**
     * @dev A modifier that defines a protected initializer function that can be invoked at most once. In its scope,
     * `onlyInitializing` functions can be used to initialize parent contracts.
     *
     * Similar to `reinitializer(1)`, except that functions marked with `initializer` can be nested in the context of a
     * constructor.
     *
     * Emits an {Initialized} event.
     */
    modifier initializer() {
        bool isTopLevelCall = !_initializing;
        require(
            (isTopLevelCall && _initialized < 1) || (!AddressUpgradeable.isContract(address(this)) && _initialized == 1),
            "Initializable: contract is already initialized"
        );
        _initialized = 1;
        if (isTopLevelCall) {
            _initializing = true;
        }
        _;
        if (isTopLevelCall) {
            _initializing = false;
            emit Initialized(1);
        }
    }

    /**
     * @dev A modifier that defines a protected reinitializer function that can be invoked at most once, and only if the
     * contract hasn't been initialized to a greater version before. In its scope, `onlyInitializing` functions can be
     * used to initialize parent contracts.
     *
     * A reinitializer may be used after the original initialization step. This is essential to configure modules that
     * are added through upgrades and that require initialization.
     *
     * When `version` is 1, this modifier is similar to `initializer`, except that functions marked with `reinitializer`
     * cannot be nested. If one is invoked in the context of another, execution will revert.
     *
     * Note that versions can jump in increments greater than 1; this implies that if multiple reinitializers coexist in
     * a contract, executing them in the right order is up to the developer or operator.
     *
     * WARNING: setting the version to 255 will prevent any future reinitialization.
     *
     * Emits an {Initialized} event.
     */
    modifier reinitializer(uint8 version) {
        require(!_initializing && _initialized < version, "Initializable: contract is already initialized");
        _initialized = version;
        _initializing = true;
        _;
        _initializing = false;
        emit Initialized(version);
    }

    /**
     * @dev Modifier to protect an initialization function so that it can only be invoked by functions with the
     * {initializer} and {reinitializer} modifiers, directly or indirectly.
     */
    modifier onlyInitializing() {
        require(_initializing, "Initializable: contract is not initializing");
        _;
    }

    /**
     * @dev Locks the contract, preventing any future reinitialization. This cannot be part of an initializer call.
     * Calling this in the constructor of a contract will prevent that contract from being initialized or reinitialized
     * to any version. It is recommended to use this to lock implementation contracts that are designed to be called
     * through proxies.
     *
     * Emits an {Initialized} event the first time it is successfully executed.
     */
    function _disableInitializers() internal virtual {
        require(!_initializing, "Initializable: contract is initializing");
        if (_initialized != type(uint8).max) {
            _initialized = type(uint8).max;
            emit Initialized(type(uint8).max);
        }
    }

    /**
     * @dev Returns the highest version that has been initialized. See {reinitializer}.
     */
    function _getInitializedVersion() internal view returns (uint8) {
        return _initialized;
    }

    /**
     * @dev Returns `true` if the contract is currently initializing. See {onlyInitializing}.
     */
    function _isInitializing() internal view returns (bool) {
        return _initializing;
    }
}


// File @openzeppelin/contracts-upgradeable/utils/[email protected]

// Original license: SPDX_License_Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.4) (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 ContextUpgradeable is Initializable {
    function __Context_init() internal onlyInitializing {
    }

    function __Context_init_unchained() internal onlyInitializing {
    }
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

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

    function _contextSuffixLength() internal view virtual returns (uint256) {
        return 0;
    }

    /**
     * @dev 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[50] private __gap;
}


// File @openzeppelin/contracts-upgradeable/access/[email protected]

// Original license: SPDX_License_Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (access/Ownable.sol)

pragma solidity ^0.8.0;


/**
 * @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 OwnableUpgradeable is Initializable, ContextUpgradeable {
    address private _owner;

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

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    function __Ownable_init() internal onlyInitializing {
        __Ownable_init_unchained();
    }

    function __Ownable_init_unchained() internal onlyInitializing {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

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

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby disabling 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);
    }

    /**
     * @dev 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[49] private __gap;
}


// File @openzeppelin/contracts-upgradeable/security/[email protected]

// Original license: SPDX_License_Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (security/Pausable.sol)

pragma solidity ^0.8.0;


/**
 * @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 PausableUpgradeable is Initializable, ContextUpgradeable {
    /**
     * @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.
     */
    function __Pausable_init() internal onlyInitializing {
        __Pausable_init_unchained();
    }

    function __Pausable_init_unchained() internal onlyInitializing {
        _paused = false;
    }

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

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    modifier whenPaused() {
        _requirePaused();
        _;
    }

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

    /**
     * @dev Throws if the contract is paused.
     */
    function _requireNotPaused() internal view virtual {
        require(!paused(), "Pausable: paused");
    }

    /**
     * @dev Throws if the contract is not paused.
     */
    function _requirePaused() internal view virtual {
        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());
    }

    /**
     * @dev 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[49] private __gap;
}


// File @openzeppelin/contracts-upgradeable/token/ERC20/extensions/[email protected]

// Original license: SPDX_License_Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.4) (token/ERC20/extensions/IERC20Permit.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 Permit extension allowing approvals to be made via signatures, as defined in
 * https://eips.ethereum.org/EIPS/eip-2612[EIP-2612].
 *
 * Adds the {permit} method, which can be used to change an account's ERC20 allowance (see {IERC20-allowance}) by
 * presenting a message signed by the account. By not relying on {IERC20-approve}, the token holder account doesn't
 * need to send a transaction, and thus is not required to hold Ether at all.
 *
 * ==== Security Considerations
 *
 * There are two important considerations concerning the use of `permit`. The first is that a valid permit signature
 * expresses an allowance, and it should not be assumed to convey additional meaning. In particular, it should not be
 * considered as an intention to spend the allowance in any specific way. The second is that because permits have
 * built-in replay protection and can be submitted by anyone, they can be frontrun. A protocol that uses permits should
 * take this into consideration and allow a `permit` call to fail. Combining these two aspects, a pattern that may be
 * generally recommended is:
 *
 * ```solidity
 * function doThingWithPermit(..., uint256 value, uint256 deadline, uint8 v, bytes32 r, bytes32 s) public {
 *     try token.permit(msg.sender, address(this), value, deadline, v, r, s) {} catch {}
 *     doThing(..., value);
 * }
 *
 * function doThing(..., uint256 value) public {
 *     token.safeTransferFrom(msg.sender, address(this), value);
 *     ...
 * }
 * ```
 *
 * Observe that: 1) `msg.sender` is used as the owner, leaving no ambiguity as to the signer intent, and 2) the use of
 * `try/catch` allows the permit to fail and makes the code tolerant to frontrunning. (See also
 * {SafeERC20-safeTransferFrom}).
 *
 * Additionally, note that smart contract wallets (such as Argent or Safe) are not able to produce permit signatures, so
 * contracts should have entry points that don't rely on permit.
 */
interface IERC20PermitUpgradeable {
    /**
     * @dev Sets `value` as the allowance of `spender` over ``owner``'s tokens,
     * given ``owner``'s signed approval.
     *
     * IMPORTANT: The same issues {IERC20-approve} has related to transaction
     * ordering also apply here.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `deadline` must be a timestamp in the future.
     * - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
     * over the EIP712-formatted function arguments.
     * - the signature must use ``owner``'s current nonce (see {nonces}).
     *
     * For more information on the signature format, see the
     * https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
     * section].
     *
     * CAUTION: See Security Considerations above.
     */
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    /**
     * @dev Returns the current nonce for `owner`. This value must be
     * included whenever a signature is generated for {permit}.
     *
     * Every successful call to {permit} increases ``owner``'s nonce by one. This
     * prevents a signature from being used multiple times.
     */
    function nonces(address owner) external view returns (uint256);

    /**
     * @dev Returns the domain separator used in the encoding of the signature for {permit}, as defined by {EIP712}.
     */
    // solhint-disable-next-line func-name-mixedcase
    function DOMAIN_SEPARATOR() external view returns (bytes32);
}


// File @openzeppelin/contracts-upgradeable/token/ERC20/[email protected]

// Original license: SPDX_License_Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20Upgradeable {
    /**
     * @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-upgradeable/token/ERC20/utils/[email protected]

// Original license: SPDX_License_Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.3) (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;



/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20Upgradeable {
    using AddressUpgradeable for address;

    /**
     * @dev Transfer `value` amount of `token` from the calling contract to `to`. If `token` returns no value,
     * non-reverting calls are assumed to be successful.
     */
    function safeTransfer(IERC20Upgradeable token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    /**
     * @dev Transfer `value` amount of `token` from `from` to `to`, spending the approval given by `from` to the
     * calling contract. If `token` returns no value, non-reverting calls are assumed to be successful.
     */
    function safeTransferFrom(IERC20Upgradeable token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(IERC20Upgradeable token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        require(
            (value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    /**
     * @dev Increase the calling contract's allowance toward `spender` by `value`. If `token` returns no value,
     * non-reverting calls are assumed to be successful.
     */
    function safeIncreaseAllowance(IERC20Upgradeable token, address spender, uint256 value) internal {
        uint256 oldAllowance = token.allowance(address(this), spender);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, oldAllowance + value));
    }

    /**
     * @dev Decrease the calling contract's allowance toward `spender` by `value`. If `token` returns no value,
     * non-reverting calls are assumed to be successful.
     */
    function safeDecreaseAllowance(IERC20Upgradeable token, address spender, uint256 value) internal {
        unchecked {
            uint256 oldAllowance = token.allowance(address(this), spender);
            require(oldAllowance >= value, "SafeERC20: decreased allowance below zero");
            _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, oldAllowance - value));
        }
    }

    /**
     * @dev Set the calling contract's allowance toward `spender` to `value`. If `token` returns no value,
     * non-reverting calls are assumed to be successful. Meant to be used with tokens that require the approval
     * to be set to zero before setting it to a non-zero value, such as USDT.
     */
    function forceApprove(IERC20Upgradeable token, address spender, uint256 value) internal {
        bytes memory approvalCall = abi.encodeWithSelector(token.approve.selector, spender, value);

        if (!_callOptionalReturnBool(token, approvalCall)) {
            _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, 0));
            _callOptionalReturn(token, approvalCall);
        }
    }

    /**
     * @dev Use a ERC-2612 signature to set the `owner` approval toward `spender` on `token`.
     * Revert on invalid signature.
     */
    function safePermit(
        IERC20PermitUpgradeable token,
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal {
        uint256 nonceBefore = token.nonces(owner);
        token.permit(owner, spender, value, deadline, v, r, s);
        uint256 nonceAfter = token.nonces(owner);
        require(nonceAfter == nonceBefore + 1, "SafeERC20: permit did not succeed");
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20Upgradeable token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address-functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        require(returndata.length == 0 || abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     *
     * This is a variant of {_callOptionalReturn} that silents catches all reverts and returns a bool instead.
     */
    function _callOptionalReturnBool(IERC20Upgradeable token, bytes memory data) private returns (bool) {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We cannot use {Address-functionCall} here since this should return false
        // and not revert is the subcall reverts.

        (bool success, bytes memory returndata) = address(token).call(data);
        return
            success && (returndata.length == 0 || abi.decode(returndata, (bool))) && AddressUpgradeable.isContract(address(token));
    }
}


// File @openzeppelin/contracts-upgradeable/utils/structs/[email protected]

// Original license: SPDX_License_Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (utils/structs/EnumerableSet.sol)
// This file was procedurally generated from scripts/generate/templates/EnumerableSet.js.

pragma solidity ^0.8.0;

/**
 * @dev Library for managing
 * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
 * types.
 *
 * Sets have the following properties:
 *
 * - Elements are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Elements are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```solidity
 * contract Example {
 *     // Add the library methods
 *     using EnumerableSet for EnumerableSet.AddressSet;
 *
 *     // Declare a set state variable
 *     EnumerableSet.AddressSet private mySet;
 * }
 * ```
 *
 * As of v3.3.0, sets of type `bytes32` (`Bytes32Set`), `address` (`AddressSet`)
 * and `uint256` (`UintSet`) are supported.
 *
 * [WARNING]
 * ====
 * Trying to delete such a structure from storage will likely result in data corruption, rendering the structure
 * unusable.
 * See https://github.com/ethereum/solidity/pull/11843[ethereum/solidity#11843] for more info.
 *
 * In order to clean an EnumerableSet, you can either remove all elements one by one or create a fresh instance using an
 * array of EnumerableSet.
 * ====
 */
library EnumerableSetUpgradeable {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.

    struct Set {
        // Storage of set values
        bytes32[] _values;
        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping(bytes32 => uint256) _indexes;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];

        if (valueIndex != 0) {
            // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.

            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;

            if (lastIndex != toDeleteIndex) {
                bytes32 lastValue = set._values[lastIndex];

                // Move the last value to the index where the value to delete is
                set._values[toDeleteIndex] = lastValue;
                // Update the index for the moved value
                set._indexes[lastValue] = valueIndex; // Replace lastValue's index to valueIndex
            }

            // Delete the slot where the moved value was stored
            set._values.pop();

            // Delete the index for the deleted slot
            delete set._indexes[value];

            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value) private view returns (bool) {
        return set._indexes[value] != 0;
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function _at(Set storage set, uint256 index) private view returns (bytes32) {
        return set._values[index];
    }

    /**
     * @dev Return the entire set in an array
     *
     * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
     * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
     * this function has an unbounded cost, and using it as part of a state-changing function may render the function
     * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
     */
    function _values(Set storage set) private view returns (bytes32[] memory) {
        return set._values;
    }

    // Bytes32Set

    struct Bytes32Set {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _add(set._inner, value);
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _remove(set._inner, value);
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(Bytes32Set storage set, bytes32 value) internal view returns (bool) {
        return _contains(set._inner, value);
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(Bytes32Set storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function at(Bytes32Set storage set, uint256 index) internal view returns (bytes32) {
        return _at(set._inner, index);
    }

    /**
     * @dev Return the entire set in an array
     *
     * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
     * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
     * this function has an unbounded cost, and using it as part of a state-changing function may render the function
     * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
     */
    function values(Bytes32Set storage set) internal view returns (bytes32[] memory) {
        bytes32[] memory store = _values(set._inner);
        bytes32[] memory result;

        /// @solidity memory-safe-assembly
        assembly {
            result := store
        }

        return result;
    }

    // AddressSet

    struct AddressSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value) internal returns (bool) {
        return _add(set._inner, bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value) internal returns (bool) {
        return _remove(set._inner, bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value) internal view returns (bool) {
        return _contains(set._inner, bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(AddressSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function at(AddressSet storage set, uint256 index) internal view returns (address) {
        return address(uint160(uint256(_at(set._inner, index))));
    }

    /**
     * @dev Return the entire set in an array
     *
     * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
     * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
     * this function has an unbounded cost, and using it as part of a state-changing function may render the function
     * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
     */
    function values(AddressSet storage set) internal view returns (address[] memory) {
        bytes32[] memory store = _values(set._inner);
        address[] memory result;

        /// @solidity memory-safe-assembly
        assembly {
            result := store
        }

        return result;
    }

    // UintSet

    struct UintSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(UintSet storage set, uint256 value) internal returns (bool) {
        return _remove(set._inner, bytes32(value));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(UintSet storage set, uint256 value) internal view returns (bool) {
        return _contains(set._inner, bytes32(value));
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function at(UintSet storage set, uint256 index) internal view returns (uint256) {
        return uint256(_at(set._inner, index));
    }

    /**
     * @dev Return the entire set in an array
     *
     * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
     * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
     * this function has an unbounded cost, and using it as part of a state-changing function may render the function
     * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
     */
    function values(UintSet storage set) internal view returns (uint256[] memory) {
        bytes32[] memory store = _values(set._inner);
        uint256[] memory result;

        /// @solidity memory-safe-assembly
        assembly {
            result := store
        }

        return result;
    }
}


// File contracts/Staking/Staking.sol

// Original license: SPDX_License_Identifier: MIT
pragma solidity =0.8.18;




/**
 * @title Staking
 * @author gotbit
 * @notice Contract for staking tokens in order to earn rewards.
 * Any user can make multiple stakes. Reward earn period is practically unlimited.
 */

contract Staking is OwnableUpgradeable, PausableUpgradeable {
    using SafeERC20Upgradeable for IERC20Upgradeable;
    using EnumerableSetUpgradeable for EnumerableSetUpgradeable.UintSet;
    using EnumerableSetUpgradeable for EnumerableSetUpgradeable.AddressSet;

    // TYPES

    struct Stake {
        uint256 id;
        uint256 amount;
        uint256 earned;
        uint256 claimed;
        uint256 userRewardPerTokenPaid;
        address owner;
        uint32 timestamp;
        uint32 unstakedAtBlockNumber;
        uint32 unstakedAtBlockTimestamp;
    }

    // CONSTANTS

    uint256 public constant ACCURACY = 1e18;
    uint256 public constant TREASURY_STAKE_AMOUNT = 1; // 1 wei (to simplify calculations)
    uint256 public constant MIN_REWARDS_DURATION = 1 minutes; // 1 min
    uint256 public constant MAX_STAKE = 10 ** 30;
    // reward rate will not fall into overflow
    // even if reward is being added during 1000 min possible reward periods in a row
    uint256 public constant MAX_RATE = type(uint128).max / (1000 * MIN_REWARDS_DURATION);
    uint256 public constant MAX_REWARDS_DURATION = 10 * 365 days; // 10 years (to prevent overflow)

    // STATE VARIABLES

    IERC20Upgradeable public stakingToken;
    IERC20Upgradeable public rewardToken;

    uint128 public rewardRate;
    uint128 public rewardsRemaining;

    uint256 public rewardPerTokenStored;

    uint64 public periodFinish;

    // rewardsDuration is not  always equal to periodFinish - periodStart
    uint64 public rewardsDuration;

    uint64 public lastUpdateTime;

    // variable for correct reward calculations in case  of rewardsDuration changes
    uint64 public periodStart;

    // sum of all rewards distributed to users in all periods
    uint256 public cumulativeDistributedReward;
    // sum of claimed reawards in one current reward period
    uint256 public currentRewardPaid;
    // sum of claimed reawards in all reward periods
    uint256 public cumulativeRewardPaid;

    // sum of unused rewards by all users in all owner locks in the current period
    // unused reward is set = 0 in each notify
    uint256 public currentPeriodUnusedRewardsSum;

    uint256 public unusedRewardsExtracted;

    mapping(uint256 => Stake) public stakes;
    mapping(address => uint256[]) public userInactiveStakes;
    mapping(address => EnumerableSetUpgradeable.UintSet) private idsByUser;

    mapping(address => uint256) public userBalances;

    uint256 public globalId;

    // hide real total supply
    uint256 private totalSupplyInternal;
    // number of currenlty active stakes
    uint128 private numOfActiveStakesInternal;

    // first reward period creation timestamp
    uint128 public firstRewardPeriodStart;

    // active stake holder
    EnumerableSetUpgradeable.AddressSet private holders;

    bool public finished;

    // EVENTS

    event RewardAdded(uint256 reward);
    event Staked(
        address indexed user,
        uint256 indexed id,
        uint256 amount,
        uint256 totalSupply
    );
    event Withdrawn(
        address indexed user,
        uint256 indexed id,
        uint256 amount,
        uint256 totalSupply
    );
    event RewardPaid(address indexed user, uint256 indexed id, uint256 reward);
    event RewardsDurationUpdated(uint256 indexed newDuration);
    event Finished(address indexed recepient);
    event WithdrawnTokens(address indexed recepient, uint256 indexed amount);

    //  FUNCTIONS

    constructor() {
        _disableInitializers();
    }

    // external

    /// @notice Inits a new contract
    /// @param stakingToken_ staking token address
    /// @param rewardToken_ reward token address
    /// @param owner_ owner address
    function init(
        IERC20Upgradeable stakingToken_,
        IERC20Upgradeable rewardToken_,
        address owner_
    ) external initializer {
        require(address(stakingToken_) != address(0), 'Invalid address');
        require(address(rewardToken_) != address(0), 'Invalid address');
        require(owner_ != address(0), 'Invalid address');

        stakingToken = stakingToken_;
        rewardToken = rewardToken_;
        rewardsDuration = 365 days;

        _transferOwnership(owner_);
    }

    /// @dev Allows user to stake tokens
    /// @param amount of token to stake
    function stake(uint256 amount) external whenNotPaused {
        require(amount > 0, 'Cannot stake 0');
        require(amount <= MAX_STAKE, 'Stake amount too high');
        require(periodFinish > block.timestamp, 'Reward period not activated');

        // if no active stakers were previously => unstake owner stake to stop accumulating unused rewards
        if (totalSupply() == 0) {
            // change stakes[0].earned
            _updateReward(0, true);
            (, uint256 unusedRewards) = _withdrawInternal(0, address(this));
            currentPeriodUnusedRewardsSum += unusedRewards;
        } else {
            // do not change stakes[0]
            _updateReward(0, false);
        }

        // execute stake
        _stakeInternal(amount, msg.sender);

        emit Staked(msg.sender, globalId, amount, totalSupply());

        stakingToken.safeTransferFrom(msg.sender, address(this), amount);
    }

    /// @dev Allows user to withdraw staked tokens + claim earned rewards
    /// @param id Stake id
    function withdraw(uint256 id) external {
        _updateReward(id, true);
        // CHANGE STATE & EXECUTE ALL CHECKS
        (uint256 amount, uint256 reward) = _withdrawInternal(id, msg.sender);

        // if no active stakers left => create a owner stake to accumulate unused rewards
        if (totalSupply() == 0) {
            _stakeInternal(TREASURY_STAKE_AMOUNT, address(this));
        }

        emit Withdrawn(msg.sender, id, amount, totalSupply());

        // ALL TOKENS TRANSFERS -------------------------------------------------------

        // REWARDS

        emit RewardPaid(msg.sender, id, reward);

        if (reward != 0) {
            rewardToken.safeTransfer(msg.sender, reward);
        }

        // PRINCIPAL

        stakingToken.safeTransfer(msg.sender, amount);
    }

    /// @dev Allows user to claim earned rewards without unstaking the position
    /// @param id Stake id
    function claim(uint256 id) external {
        _updateReward(id, true);
        // CHANGE STATE & EXECUTE ALL CHECKS
        uint256 reward = _claimInternal(id, msg.sender);

        require(reward != 0, 'Nothing to claim');

        // ALL TOKENS TRANSFERS -------------------------------------------------------

        // REWARDS

        emit RewardPaid(msg.sender, id, reward);

        // reward != 0 due to technical design
        rewardToken.safeTransfer(msg.sender, reward);
    }

    /// @dev Allows owner to set new reward rate
    /// @param newRewardRate is amount of token weis will be distributed per second (rewards / rewardsDuration)
    function notifyRewardAmount(uint128 newRewardRate) external onlyOwner {
        _updateReward(0, false);
        _notifyRewardAmount(newRewardRate);
    }

    /// @dev Allows owner to set previous reward rate
    function notifyRewardAmountPrevious() external onlyOwner {
        _updateReward(0, false);
        uint128 rate = rewardRate;
        require(rate != 0, 'Previous reward rate is too low');
        _notifyRewardAmount(rate);
    }

    /// @dev Allows owner to stop staking and extract extra liquidity
    /// @param recepient is the extra liquidity recepient
    function finish(address recepient) external onlyOwner {
        require(!finished, 'Finished');
        require(recepient != address(0), 'Zero recepient');
        uint256 periodFinishLocal = periodFinish;
        require(
            block.timestamp > periodFinishLocal && periodFinishLocal != 0,
            'Only after period end'
        );

        // lastTimeRewardApplicable == periodFinish  (period is already over)
        uint256 previousPeriodRewardDuration = periodFinishLocal - periodStart;

        // no need to unstake owner stake (no active reward period + all rewards are counted in getUnusedRewards())

        // update cumulative variables
        // use REAL previous period rewards duration here
        uint256 currentRewardDistributed = rewardRate * previousPeriodRewardDuration;

        cumulativeDistributedReward += currentRewardDistributed;
        cumulativeRewardPaid += currentRewardPaid;
        currentRewardPaid = 0;

        uint256 unusedReward = getUnusedRewards();

        uint256 unclaimedReward = cumulativeDistributedReward -
            cumulativeRewardPaid -
            unusedReward -
            unusedRewardsExtracted;

        IERC20Upgradeable rewardTokenLocal = rewardToken;
        IERC20Upgradeable stakingTokenLocal = stakingToken;

        uint256 rewardTokenBalance = rewardTokenLocal.balanceOf(address(this));
        uint256 stakingTokenBalance = stakingTokenLocal.balanceOf(address(this));

        finished = true;

        // unusedRewards - from contract
        // unclaimed rewards - on contract

        emit Finished(recepient);

        if (rewardTokenLocal == stakingTokenLocal) {
            uint256 supply = totalSupply();

            if (rewardTokenBalance - (supply + unclaimedReward) != 0) {
                rewardTokenLocal.safeTransfer(
                    recepient,
                    rewardTokenBalance - (supply + unclaimedReward)
                );
            }
        } else {
            if (rewardTokenBalance - unclaimedReward != 0) {
                rewardTokenLocal.safeTransfer(
                    recepient,
                    rewardTokenBalance - unclaimedReward
                );
            }

            uint256 supply = totalSupply();
            if (stakingTokenBalance - supply != 0) {
                stakingTokenLocal.safeTransfer(recepient, stakingTokenBalance - supply);
            }
        }
    }

    /// @dev Allows owner to stop staking and extract extra liquidity
    /// @param recepient is the extra liquidity recepient
    function withdrawOtherTokens(address token, address recepient) external onlyOwner {
        require(token != address(0), 'Invalid token');
        require(recepient != address(0), 'Zero recepient');
        require(token != address(stakingToken), 'Token == staking token');
        require(token != address(rewardToken), 'Token == reward token');

        uint256 balance = IERC20Upgradeable(token).balanceOf(address(this));
        require(balance != 0, 'Zero balance');

        emit WithdrawnTokens(recepient, balance);
        IERC20Upgradeable(token).safeTransfer(recepient, balance);
    }

    /// @dev Allows owner to set period of rewards distribution
    /// @param rewardsDuration_ is new rewardsDuration amount
    function setRewardsDuration(uint64 rewardsDuration_) external onlyOwner {
        require(block.timestamp > periodFinish, 'Previous period not complete');
        require(
            rewardsDuration_ >= MIN_REWARDS_DURATION,
            'Rewards duration is too short'
        );
        require(rewardsDuration_ <= MAX_REWARDS_DURATION, 'Rewards duration is too long');
        require(rewardsDuration_ != rewardsDuration, 'Rewards duration duplicate');
        rewardsDuration = rewardsDuration_;
        emit RewardsDurationUpdated(rewardsDuration_);
    }

    /// @dev Sets paused state for the contract (can be called by the owner only)
    /// @param state paused flag
    function setPaused(bool state) external onlyOwner {
        if (state) {
            _pause();
        } else {
            _unpause();
        }
    }

    // external view

    /// @dev Allows to view staking amount of selected user
    /// @param account to view balance
    /// @return balance of staking tokens for selected account
    function balanceOf(address account) external view returns (uint256) {
        return userBalances[account];
    }

    /// @dev Allows to view user`s stake ids quantity
    /// @param user user account
    /// @return length of user ids array
    function getUserStakeIdsLength(address user) external view returns (uint256) {
        return idsByUser[user].length();
    }

    /// @dev Allows to view if a user has a stake with specific id
    /// @param user user account
    /// @param id stake id
    /// @return bool flag (true if a user has owns the id)
    function hasStakeId(address user, uint256 id) external view returns (bool) {
        return idsByUser[user].contains(id);
    }

    /// @dev Allows to get a slice user stakes array
    /// @param user user account
    /// @param startIndex Starting index in user ids array
    /// @param length return array length
    /// @return Array-slice of user stakes
    function getUserStakesSlice(
        address user,
        uint256 startIndex,
        uint256 length
    ) external view returns (Stake[] memory) {
        require(length != 0, 'Zero length');
        require(
            startIndex + length <= idsByUser[user].length(),
            'Invalid startIndex + length'
        );
        Stake[] memory userStakes = new Stake[](length);
        for (uint256 i; i < length; ) {
            uint256 stakeId = idsByUser[user].at(i + startIndex);
            userStakes[i] = stakes[stakeId];
            userStakes[i].earned = earned(stakeId);

            unchecked {
                ++i;
            }
        }

        return userStakes;
    }

    /// @dev Allows to get a slice user stakes history array
    /// @param user user account
    /// @param startIndex Starting index in user ids array
    /// @param length return array length
    /// @return Array-slice of user stakes history
    function getUserInactiveStakesSlice(
        address user,
        uint256 startIndex,
        uint256 length
    ) external view returns (Stake[] memory) {
        require(length != 0, 'Zero length');
        require(
            startIndex + length <= userInactiveStakes[user].length,
            'Invalid startIndex + length'
        );
        Stake[] memory userStakes = new Stake[](length);

        for (uint256 i; i < length; ) {
            uint256 stakeId = userInactiveStakes[user][i + startIndex];
            userStakes[i] = stakes[stakeId];

            unchecked {
                ++i;
            }
        }
        return userStakes;
    }

    /// @dev Allows to view user`s closed stakes quantity
    /// @param user user account
    /// @return length of user closed stakes array
    function getUserInactiveStakesLength(address user) external view returns (uint256) {
        return userInactiveStakes[user].length;
    }

    /// @dev Allows to view total cumulative unclaimed rewards (earned by all users)
    /// @return rewards (nominated in token weis)
    function getTotalRewards() external view returns (uint256) {
        if (totalSupply() != 0) {
            uint256 timePassed = lastTimeRewardApplicable() - periodStart;

            uint256 totalDistributedRewards = cumulativeDistributedReward;

            if (!finished) {
                totalDistributedRewards += rewardRate * timePassed;
            }

            uint256 totalClaimedRewards = cumulativeRewardPaid + currentRewardPaid;

            return
                totalDistributedRewards -
                totalClaimedRewards -
                getUnusedRewards() -
                unusedRewardsExtracted;
        } else {
            return 0;
        }
    }

    /// @dev Returns the approximate APR for a specific stake position not including penalties
    /// @return APR value multiplied by 10**18
    function getPotentialAPR() external view returns (uint256) {
        uint256 _tvl = totalSupply();

        if (_tvl == 0) return 0;
        // earned user value in tokens for one second including share (1e18 for accuracy)
        return (uint256(rewardRate) * ACCURACY * 365 days * 100) / (_tvl);
    }

    /// @dev Allows to view the number of stake holders
    /// @return length of stake holders array
    function getHoldersLength() external view returns (uint256) {
        return holders.length();
    }

    /// @dev Allows to get a slice of stake holders array
    /// @param startIndex Starting index in stake holders array
    /// @param length return array length
    /// @return Array-slice of stake holders
    function getHoldersSlice(
        uint256 startIndex,
        uint256 length
    ) external view returns (address[] memory) {
        require(length != 0, 'Zero length');
        require(startIndex + length <= holders.length(), 'Invalid startIndex + length');
        address[] memory holdersArray = new address[](length);
        for (uint256 i = 0; i < length; ) {
            holdersArray[i] = holders.at(i + startIndex);
            unchecked {
                ++i;
            }
        }
        return holdersArray;
    }

    /// @notice Returns the number of currently active stakes
    /// @dev Excludes the number of owner`s active stakes
    /// @return numOfActiveStakesInternal - number of active stakes, made by users
    function numOfActiveStakes() external view returns (uint256) {
        return numOfActiveStakesInternal - idsByUser[address(this)].length();
    }

    // public

    /// @notice Returns the user`s stakes total supply
    /// @dev Excludes reward owner stake supply
    /// @return totalSupplyInternal - total amount of staked tokens (in weis)
    function totalSupply() public view returns (uint256) {
        return totalSupplyInternal - userBalances[address(this)];
    }

    /// @dev Allows to view last action time in the contract
    /// @return timestamp of last action
    function lastTimeRewardApplicable() public view returns (uint64) {
        return block.timestamp < periodFinish ? uint64(block.timestamp) : periodFinish;
    }

    /// @dev Allows to view already distributed rewards
    /// @return rewardPerTokenStored for current moment
    function rewardPerToken() public view returns (uint256) {
        uint256 totalSupplyInternalLocal = totalSupplyInternal;
        // can be == 0 before the first owner stake in made
        if (totalSupplyInternalLocal == 0) {
            return rewardPerTokenStored;
        }

        // can not overflow here, rewardRate * duration * ACCURACY <= uint128_max * 10 ** 18 << uint256 max
        return
            rewardPerTokenStored +
            (((lastTimeRewardApplicable() - lastUpdateTime) *
                uint256(rewardRate) *
                ACCURACY) / totalSupplyInternalLocal);
    }

    /// @dev Allows to view current user earned rewards
    /// @param id to view rewards
    /// @return earnedAmount of rewards for selected user
    function earned(uint256 id) public view returns (uint256) {
        Stake storage _stake = stakes[id];
        if (_stake.unstakedAtBlockNumber == 0) {
            // ACTIVE STAKE => calculate amount + increase reward per token
            // can not overflow here, amount * (rewardRate * duration * ACCURACY / total supply)

            uint256 amount = _stake.amount;
            uint256 rewardPerTokenLocal = rewardPerToken();
            uint256 rewardPerTokenPaid = _stake.userRewardPerTokenPaid;
            uint256 reward = uint256(
                (amount * (rewardPerTokenLocal - rewardPerTokenPaid)) /
                    ACCURACY +
                    _stake.earned
            );

            return reward;
        }

        // INACTIVE STAKE
        return 0;
    }

    /// @notice Returns the amount of unused reward tokens
    /// @return reward tokens amount in weis
    function getUnusedRewards() public view returns (uint256) {
        // makes return amount always updated real time
        return earned(0) + currentPeriodUnusedRewardsSum;
    }

    // private

    /// @dev Allows to set reward rate
    /// @param newRewardRate is amount of token weis will be distributed per second (rewards / rewardsDuration)
    function _notifyRewardAmount(uint128 newRewardRate) private {
        require(!finished, 'Finished');
        require(newRewardRate <= MAX_RATE, 'Reward rate too high');

        // reward for the incoming period => use the new rewardsDuration
        uint64 rewardsDurationLocal = rewardsDuration;
        uint256 rewardRateOld = uint256(rewardRate);
        uint256 reward = uint256(newRewardRate) * uint256(rewardsDurationLocal);
        uint256 periodFinishOld = periodFinish;

        bool restakeOwnerPosition = true;
        if (firstRewardPeriodStart == 0) {
            // open owner stake in the first reward period (stake 1 wei to to accumulate unused rewards)
            _stakeInternal(TREASURY_STAKE_AMOUNT, address(this));

            firstRewardPeriodStart = uint128(block.timestamp);
            restakeOwnerPosition = false;
        }

        // update cumulative variables
        // add rewards from teh previous period => use previous reward period start
        uint256 currentRewardDistributed = periodFinishOld == 0
            ? 0
            : rewardRateOld * (lastTimeRewardApplicable() - periodStart);

        cumulativeDistributedReward += currentRewardDistributed;
        cumulativeRewardPaid += currentRewardPaid;
        currentRewardPaid = 0;

        // update rate with the reward from the incoming period => use the updated rewards duration
        if (block.timestamp >= periodFinishOld) {
            // can not overflow here (MAX Numerator = Const * uint128_max * uint64),
            // Const < 100 <= num of reward periods, min period = 1 year
            rewardRate = uint128((reward + rewardsRemaining) / rewardsDurationLocal);
            // can not overfow here => MAX value = uint64_max - 1
            rewardsRemaining = uint128(
                (reward + rewardsRemaining) % rewardsDurationLocal
            );
        } else {
            uint64 remaining = uint64(periodFinishOld) - uint64(block.timestamp);
            uint256 leftover = remaining * rewardRateOld + rewardsRemaining;
            // can not overflow here (MAX Numerator = Const * uint128_max * uint64),
            // Const < 100 <= num of reward periods, min period = 1 year
            rewardRate = uint128((reward + leftover) / rewardsDurationLocal);
            // can not overfow here => MAX value = uint64_max - 1
            rewardsRemaining = uint128((reward + leftover) % rewardsDurationLocal);
        }

        uint256 rewardRateNew = rewardRate;

        require(rewardRateNew != 0, 'Actual reward rate is too low');

        // Ensure the provided reward amount is not more than the balance in the contract.
        // This keeps the reward rate in the right range, preventing overflows due to
        // very high values of rewardRate in the earned and rewardsPerToken functions;
        uint256 balance = address(rewardToken) == address(stakingToken)
            ? rewardToken.balanceOf(address(this)) - totalSupply()
            : rewardToken.balanceOf(address(this));

        bool updateUnusedReward = (totalSupply() == 0);
        uint256 unusedReward = getUnusedRewards();

        uint256 unclaimedReward = cumulativeDistributedReward -
            cumulativeRewardPaid -
            unusedReward -
            unusedRewardsExtracted;

        // unusedRewards are transferred to the owner in each notify
        currentPeriodUnusedRewardsSum = 0;
        // increase total unused rewards extracted after each period
        unusedRewardsExtracted += unusedReward;

        // if no active stakers were previously => unstake owner stake to stop accumulating unused rewards
        if (updateUnusedReward && restakeOwnerPosition) {
            _updateReward(0, true);
            // no update for cumulative unused reward here (already called getUnusedRewards() before, using earned())
            _withdrawInternal(0, address(this));
        }

        // Ensure the balance in the contract is more than the maximum reward + unclaimedRewards
        require(
            rewardRateNew * rewardsDurationLocal + unclaimedReward + unusedReward <=
                balance,
            'Provided reward too high'
        );

        lastUpdateTime = uint64(block.timestamp);
        periodFinish = uint64(block.timestamp) + rewardsDurationLocal;
        periodStart = uint64(block.timestamp);

        if (updateUnusedReward && restakeOwnerPosition) {
            _stakeInternal(TREASURY_STAKE_AMOUNT, address(this));
        }

        if (unusedReward != 0)
            IERC20Upgradeable(rewardToken).safeTransfer(owner(), unusedReward);

        emit RewardAdded(reward);
    }

    /// @dev Internal function for staking tokens
    /// @param amount of token to stake
    function _stakeInternal(uint256 amount, address interractor) private {
        totalSupplyInternal += amount;
        ++numOfActiveStakesInternal;

        uint256 newId;
        if (interractor != address(this)) {
            newId = ++globalId;
        }
        // else owner stake => newId = 0 (not to affect other stakes)

        stakes[newId] = Stake({
            id: newId,
            amount: amount,
            earned: 0,
            claimed: 0,
            userRewardPerTokenPaid: rewardPerTokenStored,
            owner: interractor,
            timestamp: uint32(block.timestamp),
            unstakedAtBlockNumber: 0,
            unstakedAtBlockTimestamp: 0
        });

        // add new holder if needed (address(this) should not be displayed in holders)
        if (userBalances[interractor] == 0 && interractor != address(this))
            holders.add(interractor);

        userBalances[interractor] += amount;
        idsByUser[interractor].add(newId);
    }

    /// @dev Internal function for withdrawing staked tokens + claim earned rewards
    /// @param id Stake id
    /// @param interractor Address which is supposed to be the stake owner
    /// @return amount - principal token amount, reward - reward token amount
    function _withdrawInternal(
        uint256 id,
        address interractor
    ) private returns (uint256 amount, uint256 reward) {
        Stake storage _stake = stakes[id];
        amount = _stake.amount;
        require(_stake.unstakedAtBlockNumber == 0, 'Already unstaked');
        require(_stake.owner == interractor, 'Called not by stake owner');

        totalSupplyInternal -= amount;
        userBalances[interractor] -= amount;

        --numOfActiveStakesInternal;

        // calculate the available rewards
        // increase the currentRewardPaid
        // earned = 0, increase claimed
        reward = _claimInternal(id, interractor);

        // address(this) should not be displayed in holders
        if (userBalances[interractor] == 0 && interractor != address(this))
            holders.remove(interractor);

        idsByUser[interractor].remove(id);

        if (interractor != address(this)) userInactiveStakes[interractor].push(id);

        stakes[id].unstakedAtBlockNumber = uint32(block.number);
        stakes[id].unstakedAtBlockTimestamp = uint32(block.timestamp);
    }

    function _claimInternal(
        uint256 id,
        address interractor
    ) private returns (uint256 reward) {
        Stake storage _stake = stakes[id];
        require(_stake.unstakedAtBlockNumber == 0, 'Already unstaked');
        require(_stake.owner == interractor, 'Called not by stake owner');

        // reward already updated
        reward = _stake.earned;

        if (reward != 0 && interractor != address(this)) {
            // CLAIM ALL EARNED REWARDS
            // update var only if claim by real user
            currentRewardPaid += reward;
        }

        if (reward != 0) {
            stakes[id].earned = 0;
            stakes[id].claimed += reward;
        }
    }

    /// @dev Update rewards pool information to correct rewards calculation for global varialbes and current stake
    /// @param id stake to update info for
    /// @param updateId flag, true when update stake struct
    function _updateReward(uint256 id, bool updateId) private {
        rewardPerTokenStored = rewardPerToken();
        lastUpdateTime = lastTimeRewardApplicable();

        if (updateId) {
            stakes[id].earned = earned(id);
            stakes[id].userRewardPerTokenPaid = rewardPerTokenStored;
        }
    }
}