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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (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 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 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/security/ReentrancyGuard.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (security/ReentrancyGuard.sol)

pragma solidity ^0.8.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        _nonReentrantBefore();
        _;
        _nonReentrantAfter();
    }

    function _nonReentrantBefore() private {
        // On the first call to nonReentrant, _status will be _NOT_ENTERED
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;
    }

    function _nonReentrantAfter() private {
        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

// File: @openzeppelin/contracts/token/ERC20/extensions/draft-IERC20Permit.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/draft-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.
 */
interface IERC20Permit {
    /**
     * @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].
     */
    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/token/ERC20/IERC20.sol



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

pragma solidity ^0.8.0;

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

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

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

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

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

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

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

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

// File: @openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";
import "../extensions/draft-IERC20Permit.sol";
import "../../../utils/Address.sol";

/**
 * @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 SafeERC20 {
    using Address for address;

    function safeTransfer(
        IERC20 token,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(
        IERC20 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(
        IERC20 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));
    }

    function safeIncreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        uint256 newAllowance = token.allowance(address(this), spender) + value;
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        unchecked {
            uint256 oldAllowance = token.allowance(address(this), spender);
            require(oldAllowance >= value, "SafeERC20: decreased allowance below zero");
            uint256 newAllowance = oldAllowance - value;
            _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
        }
    }

    function safePermit(
        IERC20Permit 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(IERC20 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");
        if (returndata.length > 0) {
            // Return data is optional
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (utils/Address.sol)

pragma solidity ^0.8.1;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @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
     * ====
     *
     * [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://diligence.consensys.net/posts/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/v0.5.11/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/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/structs/EnumerableSet.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (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.
 *
 * ```
 * 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 EnumerableSet {
    // 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/interfaces/ILiquidity.sol



// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.17;

/// @title Interface for Liquidity contract
interface ILiquidity {
  /// @dev Emitted when an address is added to the whitelist
  event AddedToWhitelist(address indexed _address);
  /// @dev Emitted when an address is removed from the whitelist
  event RemovedFromWhitelist(address indexed _address);
  /// @dev Emitted when tokens are withdrawn from the contract
  event Withdrawn(address indexed _token, uint256 _amount, address indexed _to);
  /// @dev Emitted when ETH is received by the contract
  event Received(address indexed _from, uint256 _amount);
  /// @dev Emitted when the position is changed
  event PositionChanged(
    uint256 indexed positionId,
    uint256 amount0,
    uint256 amount1,
    uint256 liquidity,
    int24 tickLower,
    int24 tickUpper
  );

  /// @notice Get the balance of token0 held by the contract
  /// @return The balance of token0
  function balanceOfToken0() external view returns (uint256);

  /// @notice Get the balance of token1 held by the contract
  /// @return The balance of token1
  function balanceOfToken1() external view returns (uint256);

  /// @notice Set the fee address for the contract
  /// @param _address The address to set as the fee address
  function setFeeAddress(address _address) external;

  /// @notice Withdraw tokens from the contract
  /// @param _token The token to withdraw
  /// @param _amount The amount to withdraw
  /// @param _to The address to send the withdrawn tokens
  function withdraw(address _token, uint256 _amount, address payable _to) external;

  /// @notice Close the current position
  function closePosition() external;

  /// @notice Change the position of the contract
  /// @param tickLower The new lower tick
  /// @param tickUpper The new upper tick
  /// @param withdrawToken0Amount The amount of token0 to withdraw
  /// @param withdrawToken1Amount The amount of token1 to withdraw
  /// @param withdrawToken0Destination The address to send the withdrawn token0
  /// @param withdrawToken1Destination The address to send the withdrawn token1
  function changePosition(
    int24 tickLower,
    int24 tickUpper,
    uint256 withdrawToken0Amount,
    uint256 withdrawToken1Amount,
    address payable withdrawToken0Destination,
    address payable withdrawToken1Destination
  ) external;

  /// @notice Make an emergency call to another contract
  /// @param contractToCall The address of the contract to call
  /// @param callData The calldata to use for the call
  function makeEmergencyCall(address contractToCall, bytes calldata callData) external;
}

// File: contracts/interfaces/IManager.sol



// SPDX-License-Identifier: GPL-3.0
pragma solidity ^0.8.17;

import "@openzeppelin/contracts/utils/structs/EnumerableSet.sol";

/// @title Interface to add allowed operator in addition to owner
abstract contract IManager {
    using EnumerableSet for EnumerableSet.AddressSet;
    EnumerableSet.AddressSet private managers;

    /// @notice Requires the sender to be a manager
    modifier onlyManager() {
        require(managers.contains(msg.sender), "You do not have rights");
        _;
    }

    /// @dev Emitted when a manager is added
    event ManagerAdded(address);
    /// @dev Emitted when a manager is removed
    event ManagerRemoved(address);

    /// @notice Add a manager
    /// @param _manager The address of the manager to add
    function addManager(address _manager) external virtual;

    /// @notice Remove a manager
    /// @param _manager The address of the manager to remove
    function removeManager(address _manager) external virtual;

    /// @dev Add a manager internally
    /// @param _manager The address of the manager to add
    function _addManager(address _manager) internal {
        require(_manager != address(0), "Address should not be empty");
        require(!managers.contains(_manager), "Already added");
        managers.add(_manager);
        emit ManagerAdded(_manager);

    }

    /// @dev Remove a manager internally
    /// @param _manager The address of the manager to remove
    function _removeManager(address _manager) internal {
        require(managers.contains(_manager), "Not exist");
        managers.remove(_manager);
        emit ManagerRemoved(_manager);
    }

    /// @notice Get the list of managers
    /// @return An array of manager addresses
    function getManagers() external view returns (address[] memory) {
        return managers.values();
    }
}

// File: contracts/interfaces/INonFungiblePositionManager.sol



// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.17;

interface INonFungiblePositionManager {
  struct MintParams {
    address token0;
    address token1;
    uint24 fee;
    int24 tickLower;
    int24 tickUpper;
    uint256 amount0Desired;
    uint256 amount1Desired;
    uint256 amount0Min;
    uint256 amount1Min;
    address recipient;
    uint256 deadline;
  }

  struct CollectParams {
    uint256 tokenId;
    address recipient;
    uint128 amount0Max;
    uint128 amount1Max;
  }

  struct DecreaseLiquidityParams {
    uint256 tokenId;
    uint128 liquidity;
    uint256 amount0Min;
    uint256 amount1Min;
    uint256 deadline;
  }

  struct PositionInfo {
    uint96 nonce;
    address operator;
    address token0;
    address token1;
    uint24 fee;
    int24 tickLower;
    int24 tickUpper;
    uint128 liquidity;
    uint256 feeGrowthInside0LastX128;
    uint256 feeGrowthInside1LastX128;
    uint128 tokensOwed0;
    uint128 tokensOwed1;
  }

  function positions(uint256 tokenId) external view returns (PositionInfo memory positionInfo);

  function mint(
    MintParams memory params
  ) external returns (uint256 tokenId, uint128 liquidity, uint256 amount0, uint256 amount1);

  function decreaseLiquidity(
    DecreaseLiquidityParams memory params
  ) external returns (uint256 amount0, uint256 amount1);

  function collect(CollectParams memory params) external returns (uint256 amount0, uint256 amount1);
}

// File: contracts/interfaces/IWETH.sol



// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.17;

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

interface IWETH {
  function balanceOf(address account) external view returns (uint256);

  function withdraw(uint amount) external;

  function deposit() external payable;

  function transferFrom(address src, address dst, uint wad) external returns (bool);
}

// File: contracts/interfaces/IWhitelist.sol



// SPDX-License-Identifier: GPL-3.0
pragma solidity ^0.8.17;

import "@openzeppelin/contracts/utils/structs/EnumerableSet.sol";

/**
 * @title Interface to add allowed operator in addition to owner
 */
abstract contract IWhitelist {
    using EnumerableSet for EnumerableSet.AddressSet;
    EnumerableSet.AddressSet private whitelist;

    event WhitelistAdded(address);
    event WhitelistRemoved(address);

    function isWhitelisted(address _address) public view returns (bool) {
        return whitelist.contains(_address);
    }

    function addWhitelist(address _address) external virtual;

    function removeWhitelist(address _address) external virtual;

    function _addWhitelist(address _address) internal {
        require(_address != address(0), "Address should not be empty");
        require(!whitelist.contains(_address), "Already added");
        whitelist.add(_address);
        emit WhitelistAdded(_address);

    }

    function _removeWhitelist(address _address) internal {
        require(whitelist.contains(_address), "Not exist");
        whitelist.remove(_address);
        emit WhitelistRemoved(_address);
    }

    function getWhitelist() external view returns (address[] memory) {
        return whitelist.values();
    }
}

// File: contracts/Liquidity.sol



// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.17;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";

import "./interfaces/IWETH.sol";
import "./interfaces/INonFungiblePositionManager.sol";
import "./interfaces/ILiquidity.sol";
import "./interfaces/IManager.sol";
import "./interfaces/IWhitelist.sol";

/// @title Liquidity Contract V1
/// @notice A contract to manage Uniswap V3 liquidity positions.
contract Liquidity is ILiquidity, IManager, IWhitelist, Ownable, ReentrancyGuard {
  using SafeERC20 for IERC20;

  address private constant WETH = 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2;
  uint128 private constant MAX_UINT_128 = type(uint128).max;
  uint256 private constant MAX_UINT_256 = type(uint256).max;
  uint24 private constant ACTION_DEADLINE = 600;

  INonFungiblePositionManager public immutable positionManager;
  address public immutable token0;
  address public immutable token1;
  uint24 public immutable fee;

  uint256 public positionId;
  address public feeAddress;

  /// @notice Constructs the Liquidity contract
  /// @param _token0 The address of token0
  /// @param _token1 The address of token1
  /// @param _fee The fee to be used
  /// @param _feeAddress The address to receive the fees
  /// @param _positionManager The address of the Uniswap V3 non-fungible position manager
  constructor(
    address _token0,
    address _token1,
    uint24 _fee,
    address _feeAddress,
    address _positionManager
  ) {
    require(_token0 != address(0), "Token0 address must be valid");
    require(_token1 != address(0), "Token1 address must be valid");
    require(_feeAddress != address(0), "Fee address must be valid");
    require(_positionManager != address(0), "Position manager address must be valid");

    token0 = _token0;
    token1 = _token1;
    fee = _fee;
    feeAddress = _feeAddress;
    positionManager = INonFungiblePositionManager(_positionManager);
  }

  /// @notice Receive ETH and wrap to WETH
  receive() external payable {
    if (msg.sender != WETH) {
      IWETH(WETH).deposit{value : msg.value}();
      emit Received(msg.sender, msg.value);
    }
  }

  /// @notice Add a new manager address
  /// @param _manager The address of the new manager
  function addManager(address _manager) external override onlyOwner {
    _addManager(_manager);
  }

  /// @notice Remove a manager address
  /// @param _manager The address of the manager to remove
  function removeManager(address _manager) external override onlyOwner {
    _removeManager(_manager);
  }

  /// @notice Get the balance of token0 held by the contract
  /// @return The balance of token0
  function balanceOfToken0() public view override returns (uint256) {
    return IERC20(token0).balanceOf(address(this));
  }

  /// @notice Get the balance of token1 held by the contract
  /// @return The balance of token1
  function balanceOfToken1() public view override returns (uint256) {
    return IERC20(token1).balanceOf(address(this));
  }

  /// @notice Add an address to the whitelist
  /// @param _address The address to be added to the whitelist
  function addWhitelist(address _address) public override onlyOwner {
    _addWhitelist(_address);
  }

  /// @notice Remove an address from the whitelist
  /// @param _address The address to be removed from the whitelist
  function removeWhitelist(address _address) public override onlyOwner {
    _removeWhitelist(_address);
  }

  /// @notice Set the fee address
  /// @param _address The address to receive fees
  function setFeeAddress(address _address) public override onlyOwner {
    feeAddress = _address;
  }

  /// @notice Close the current position
  function closePosition() public override onlyOwner {
    _closePosition();
  }

  /// @notice Change the current position
  /// @param _tickLower The lower tick boundary of the new position
  /// @param _tickUpper The upper tick boundary of the new position
  /// @param withdrawToken0Amount The amount of token0 to withdraw
  /// @param withdrawToken1Amount The amount of token1 to withdraw
  /// @param withdrawToken0Destination The address to send the withdrawn token0
  /// @param withdrawToken1Destination The address to send the withdrawn token1
  function changePosition(int24 _tickLower, int24 _tickUpper, uint256 withdrawToken0Amount, uint256 withdrawToken1Amount, address payable withdrawToken0Destination, address payable withdrawToken1Destination) public override onlyManager nonReentrant {
    if (positionId != 0) {
      _closePosition();
    }
    if (withdrawToken0Amount > 0) {
      withdraw(token0, withdrawToken0Amount, withdrawToken0Destination);
    }
    if (withdrawToken1Amount > 0) {
      withdraw(token1, withdrawToken1Amount, withdrawToken1Destination);
    }

    (uint256 tokenId, uint128 liquidity, uint256 amount0, uint256 amount1) = _openPosition(
      _tickLower,
      _tickUpper
    );
    emit PositionChanged(tokenId, amount0, amount1, liquidity, _tickLower, _tickUpper);
  }

  /// @notice Withdraw tokens from the contract
  /// @param _token The token to withdraw
  /// @param _amount The amount to withdraw
  /// @param _destination The address to send the withdrawn tokens
  function withdraw(
    address _token,
    uint256 _amount,
    address payable _destination
  ) public override onlyManager {
    require(isWhitelisted(_destination), "Address is not whitelisted");
    if (_token == WETH) {
      require(IWETH(_token).balanceOf(address(this)) >= _amount, "Not enough WETH balance");
      IWETH(_token).withdraw(_amount);
      if (_isContract(_destination)) {
        (bool success,) = _destination.call{value : _amount}("");
        require(success, "Ether transfer failed");
      } else {
        _destination.transfer(_amount);
      }
    } else {
      IERC20(_token).safeTransfer(_destination, _amount);
    }
  }
  /// @notice Make an emergency call to another contract
  /// @param contractToCall The address of the contract to call
  /// @param callData to send to the contract
  function makeEmergencyCall(
    address contractToCall,
    bytes calldata callData
  ) external override onlyOwner {
    (bool success, bytes memory result) = contractToCall.call(callData);
    if (!success) {
      // Next 5 lines from https://ethereum.stackexchange.com/a/83577
      if (result.length < 68) revert();
      assembly {
        result := add(result, 0x04)
      }
      revert(abi.decode(result, (string)));
    }
  }

  /// @dev Close the current position
  function _closePosition() private {
    INonFungiblePositionManager.CollectParams memory collectFeeParams = INonFungiblePositionManager
    .CollectParams(positionId, feeAddress, MAX_UINT_128, MAX_UINT_128);

    positionManager.collect(collectFeeParams);

    INonFungiblePositionManager.PositionInfo memory positionInfo = positionManager.positions(
      positionId
    );

    INonFungiblePositionManager.DecreaseLiquidityParams
    memory decreaseLiquidityParams = INonFungiblePositionManager.DecreaseLiquidityParams(
      positionId,
      positionInfo.liquidity,
      0,
      0,
      block.timestamp + ACTION_DEADLINE
    );

    positionManager.decreaseLiquidity(decreaseLiquidityParams);

    INonFungiblePositionManager.CollectParams
    memory collectLiquidityParams = INonFungiblePositionManager.CollectParams(
      positionId,
      address(this),
      MAX_UINT_128,
      MAX_UINT_128
    );

    positionManager.collect(collectLiquidityParams);
    positionId = 0;
  }

  /// @dev Open a new position
  /// @param _tickLower The lower tick boundary of the new position
  /// @param _tickUpper The upper tick boundary of the new position
  /// @return tokenId The token ID of the new position
  /// @return liquidity The liquidity of the new position
  /// @return amount0 The amount of token0 in the new position
  /// @return amount1 The amount of token1 in the new position
  function _openPosition(
    int24 _tickLower,
    int24 _tickUpper
  ) private returns (uint256 tokenId, uint128 liquidity, uint256 amount0, uint256 amount1) {
    require(_tickLower < _tickUpper, "Tick lower must be less than tick upper");
    uint256 amount0Desired = IERC20(token0).balanceOf(address(this));
    uint256 amount1Desired = IERC20(token1).balanceOf(address(this));
    _safeApprove(token0, address(positionManager), amount0Desired);
    _safeApprove(token1, address(positionManager), amount1Desired);

    // Create the position
    INonFungiblePositionManager.MintParams memory params = INonFungiblePositionManager.MintParams(
      token0,
      token1,
      fee,
      _tickLower,
      _tickUpper,
      amount0Desired,
      amount1Desired,
      0,
      0,
      address(this),
      block.timestamp + ACTION_DEADLINE
    );

    (tokenId, liquidity, amount0, amount1) = positionManager.mint(params);
    positionId = tokenId;
  }
  // @dev Safely approve another contract to spend tokens
  /// @param token The token to approve
  /// @param receiver The address of the contract to approve
  /// @param amount The amount to approve
  function _safeApprove(address token, address receiver, uint256 amount) private {
    uint256 allowed = IERC20(token).allowance(address(this), receiver);
    if (allowed < amount) {
      if (allowed != 0) {
        IERC20(token).safeApprove(receiver, 0);
      }
      IERC20(token).safeApprove(receiver, MAX_UINT_256);
    }
  }

  /// @dev Check if an address is a contract
  /// @param _addr The address to check
  /// @return Whether the address is a contract
  function _isContract(address _addr) private view returns (bool) {
    uint256 size;
    assembly {
      size := extcodesize(_addr)
    }
    return size > 0;
  }
}