// File: contracts/ERC721StakingPoolFactory.sol



// SPDX-License-Identifier: AGPL-3.0
pragma solidity ^0.8.11;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";

import { Ownable } from "./lib/Ownable.sol";

import { ERC721StakingPool } from "./ERC721StakingPool.sol";
import { ClonesWithCallData } from "./lib/ClonesWithCallData.sol";

/// @title StakingPoolFactory
/// @author zefram.eth
/// @notice Factory for deploying ERC20StakingPool and ERC721StakingPool contracts cheaply
contract ERC721StakingPoolFactory is Ownable {
    /// -----------------------------------------------------------------------
    /// Library usage
    /// -----------------------------------------------------------------------

    using ClonesWithCallData for address;

    /// -----------------------------------------------------------------------
    /// Events
    /// -----------------------------------------------------------------------

    event CreateERC721StakingPool(ERC721StakingPool stakingPool);

    /// -----------------------------------------------------------------------
    /// Immutable parameters
    /// -----------------------------------------------------------------------

    /// @notice The contract used as the template for all ERC721StakingPool contracts created
    ERC721StakingPool public immutable erc721StakingPoolImplementation;

    /// maintain a mapping stakeToken contract => staking contract
    mapping(ERC721 => ERC721StakingPool) public erc721StakingContractMap;

    constructor(ERC721StakingPool erc721StakingPoolImplementation_) {
        erc721StakingPoolImplementation = erc721StakingPoolImplementation_;
    }

    /// @notice Creates an ERC721StakingPool contract
    /// @dev Uses a modified minimal proxy contract that stores immutable parameters in code and
    /// passes them in through calldata. See ClonesWithCallData.
    /// @param rewardToken The token being rewarded to stakers
    /// @param stakeToken The token being staked in the pool
    /// @param DURATION The length of each reward period, in seconds
    /// @return stakingPool The created ERC721StakingPool contract
    function createERC721StakingPool(
        address rewardToken,
        ERC721 stakeToken,
        uint64 DURATION
    ) external onlyOwner returns (ERC721StakingPool stakingPool) {
        bytes memory ptr;
        ptr = new bytes(48);
        assembly {
            mstore(add(ptr, 0x20), shl(0x60, rewardToken))
            mstore(add(ptr, 0x34), shl(0x60, stakeToken))
            mstore(add(ptr, 0x48), shl(0xc0, DURATION))
        }

        stakingPool = ERC721StakingPool(address(erc721StakingPoolImplementation).cloneWithCallDataProvision(ptr));
        stakingPool.initialize(msg.sender);
        erc721StakingContractMap[stakeToken] = stakingPool;

        emit CreateERC721StakingPool(stakingPool);
    }
}

// File: @openzeppelin/contracts/token/ERC721/ERC721.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC721/ERC721.sol)

pragma solidity ^0.8.0;

import "./IERC721.sol";
import "./IERC721Receiver.sol";
import "./extensions/IERC721Metadata.sol";
import "../../utils/Address.sol";
import "../../utils/Context.sol";
import "../../utils/Strings.sol";
import "../../utils/introspection/ERC165.sol";

/**
 * @dev Implementation of https://eips.ethereum.org/EIPS/eip-721[ERC721] Non-Fungible Token Standard, including
 * the Metadata extension, but not including the Enumerable extension, which is available separately as
 * {ERC721Enumerable}.
 */
contract ERC721 is Context, ERC165, IERC721, IERC721Metadata {
    using Address for address;
    using Strings for uint256;

    // Token name
    string private _name;

    // Token symbol
    string private _symbol;

    // Mapping from token ID to owner address
    mapping(uint256 => address) private _owners;

    // Mapping owner address to token count
    mapping(address => uint256) private _balances;

    // Mapping from token ID to approved address
    mapping(uint256 => address) private _tokenApprovals;

    // Mapping from owner to operator approvals
    mapping(address => mapping(address => bool)) private _operatorApprovals;

    /**
     * @dev Initializes the contract by setting a `name` and a `symbol` to the token collection.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
        return
            interfaceId == type(IERC721).interfaceId ||
            interfaceId == type(IERC721Metadata).interfaceId ||
            super.supportsInterface(interfaceId);
    }

    /**
     * @dev See {IERC721-balanceOf}.
     */
    function balanceOf(address owner) public view virtual override returns (uint256) {
        require(owner != address(0), "ERC721: balance query for the zero address");
        return _balances[owner];
    }

    /**
     * @dev See {IERC721-ownerOf}.
     */
    function ownerOf(uint256 tokenId) public view virtual override returns (address) {
        address owner = _owners[tokenId];
        require(owner != address(0), "ERC721: owner query for nonexistent token");
        return owner;
    }

    /**
     * @dev See {IERC721Metadata-name}.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev See {IERC721Metadata-symbol}.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev See {IERC721Metadata-tokenURI}.
     */
    function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {
        require(_exists(tokenId), "ERC721Metadata: URI query for nonexistent token");

        string memory baseURI = _baseURI();
        return bytes(baseURI).length > 0 ? string(abi.encodePacked(baseURI, tokenId.toString())) : "";
    }

    /**
     * @dev Base URI for computing {tokenURI}. If set, the resulting URI for each
     * token will be the concatenation of the `baseURI` and the `tokenId`. Empty
     * by default, can be overriden in child contracts.
     */
    function _baseURI() internal view virtual returns (string memory) {
        return "";
    }

    /**
     * @dev See {IERC721-approve}.
     */
    function approve(address to, uint256 tokenId) public virtual override {
        address owner = ERC721.ownerOf(tokenId);
        require(to != owner, "ERC721: approval to current owner");

        require(
            _msgSender() == owner || isApprovedForAll(owner, _msgSender()),
            "ERC721: approve caller is not owner nor approved for all"
        );

        _approve(to, tokenId);
    }

    /**
     * @dev See {IERC721-getApproved}.
     */
    function getApproved(uint256 tokenId) public view virtual override returns (address) {
        require(_exists(tokenId), "ERC721: approved query for nonexistent token");

        return _tokenApprovals[tokenId];
    }

    /**
     * @dev See {IERC721-setApprovalForAll}.
     */
    function setApprovalForAll(address operator, bool approved) public virtual override {
        _setApprovalForAll(_msgSender(), operator, approved);
    }

    /**
     * @dev See {IERC721-isApprovedForAll}.
     */
    function isApprovedForAll(address owner, address operator) public view virtual override returns (bool) {
        return _operatorApprovals[owner][operator];
    }

    /**
     * @dev See {IERC721-transferFrom}.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public virtual override {
        //solhint-disable-next-line max-line-length
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");

        _transfer(from, to, tokenId);
    }

    /**
     * @dev See {IERC721-safeTransferFrom}.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public virtual override {
        safeTransferFrom(from, to, tokenId, "");
    }

    /**
     * @dev See {IERC721-safeTransferFrom}.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
    ) public virtual override {
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");
        _safeTransfer(from, to, tokenId, _data);
    }

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * `_data` is additional data, it has no specified format and it is sent in call to `to`.
     *
     * This internal function is equivalent to {safeTransferFrom}, and can be used to e.g.
     * implement alternative mechanisms to perform token transfer, such as signature-based.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function _safeTransfer(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
    ) internal virtual {
        _transfer(from, to, tokenId);
        require(_checkOnERC721Received(from, to, tokenId, _data), "ERC721: transfer to non ERC721Receiver implementer");
    }

    /**
     * @dev Returns whether `tokenId` exists.
     *
     * Tokens can be managed by their owner or approved accounts via {approve} or {setApprovalForAll}.
     *
     * Tokens start existing when they are minted (`_mint`),
     * and stop existing when they are burned (`_burn`).
     */
    function _exists(uint256 tokenId) internal view virtual returns (bool) {
        return _owners[tokenId] != address(0);
    }

    /**
     * @dev Returns whether `spender` is allowed to manage `tokenId`.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function _isApprovedOrOwner(address spender, uint256 tokenId) internal view virtual returns (bool) {
        require(_exists(tokenId), "ERC721: operator query for nonexistent token");
        address owner = ERC721.ownerOf(tokenId);
        return (spender == owner || getApproved(tokenId) == spender || isApprovedForAll(owner, spender));
    }

    /**
     * @dev Safely mints `tokenId` and transfers it to `to`.
     *
     * Requirements:
     *
     * - `tokenId` must not exist.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function _safeMint(address to, uint256 tokenId) internal virtual {
        _safeMint(to, tokenId, "");
    }

    /**
     * @dev Same as {xref-ERC721-_safeMint-address-uint256-}[`_safeMint`], with an additional `data` parameter which is
     * forwarded in {IERC721Receiver-onERC721Received} to contract recipients.
     */
    function _safeMint(
        address to,
        uint256 tokenId,
        bytes memory _data
    ) internal virtual {
        _mint(to, tokenId);
        require(
            _checkOnERC721Received(address(0), to, tokenId, _data),
            "ERC721: transfer to non ERC721Receiver implementer"
        );
    }

    /**
     * @dev Mints `tokenId` and transfers it to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {_safeMint} whenever possible
     *
     * Requirements:
     *
     * - `tokenId` must not exist.
     * - `to` cannot be the zero address.
     *
     * Emits a {Transfer} event.
     */
    function _mint(address to, uint256 tokenId) internal virtual {
        require(to != address(0), "ERC721: mint to the zero address");
        require(!_exists(tokenId), "ERC721: token already minted");

        _beforeTokenTransfer(address(0), to, tokenId);

        _balances[to] += 1;
        _owners[tokenId] = to;

        emit Transfer(address(0), to, tokenId);

        _afterTokenTransfer(address(0), to, tokenId);
    }

    /**
     * @dev Destroys `tokenId`.
     * The approval is cleared when the token is burned.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     *
     * Emits a {Transfer} event.
     */
    function _burn(uint256 tokenId) internal virtual {
        address owner = ERC721.ownerOf(tokenId);

        _beforeTokenTransfer(owner, address(0), tokenId);

        // Clear approvals
        _approve(address(0), tokenId);

        _balances[owner] -= 1;
        delete _owners[tokenId];

        emit Transfer(owner, address(0), tokenId);

        _afterTokenTransfer(owner, address(0), tokenId);
    }

    /**
     * @dev Transfers `tokenId` from `from` to `to`.
     *  As opposed to {transferFrom}, this imposes no restrictions on msg.sender.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     *
     * Emits a {Transfer} event.
     */
    function _transfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual {
        require(ERC721.ownerOf(tokenId) == from, "ERC721: transfer from incorrect owner");
        require(to != address(0), "ERC721: transfer to the zero address");

        _beforeTokenTransfer(from, to, tokenId);

        // Clear approvals from the previous owner
        _approve(address(0), tokenId);

        _balances[from] -= 1;
        _balances[to] += 1;
        _owners[tokenId] = to;

        emit Transfer(from, to, tokenId);

        _afterTokenTransfer(from, to, tokenId);
    }

    /**
     * @dev Approve `to` to operate on `tokenId`
     *
     * Emits a {Approval} event.
     */
    function _approve(address to, uint256 tokenId) internal virtual {
        _tokenApprovals[tokenId] = to;
        emit Approval(ERC721.ownerOf(tokenId), to, tokenId);
    }

    /**
     * @dev Approve `operator` to operate on all of `owner` tokens
     *
     * Emits a {ApprovalForAll} event.
     */
    function _setApprovalForAll(
        address owner,
        address operator,
        bool approved
    ) internal virtual {
        require(owner != operator, "ERC721: approve to caller");
        _operatorApprovals[owner][operator] = approved;
        emit ApprovalForAll(owner, operator, approved);
    }

    /**
     * @dev Internal function to invoke {IERC721Receiver-onERC721Received} on a target address.
     * The call is not executed if the target address is not a contract.
     *
     * @param from address representing the previous owner of the given token ID
     * @param to target address that will receive the tokens
     * @param tokenId uint256 ID of the token to be transferred
     * @param _data bytes optional data to send along with the call
     * @return bool whether the call correctly returned the expected magic value
     */
    function _checkOnERC721Received(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
    ) private returns (bool) {
        if (to.isContract()) {
            try IERC721Receiver(to).onERC721Received(_msgSender(), from, tokenId, _data) returns (bytes4 retval) {
                return retval == IERC721Receiver.onERC721Received.selector;
            } catch (bytes memory reason) {
                if (reason.length == 0) {
                    revert("ERC721: transfer to non ERC721Receiver implementer");
                } else {
                    assembly {
                        revert(add(32, reason), mload(reason))
                    }
                }
            }
        } else {
            return true;
        }
    }

    /**
     * @dev Hook that is called before any token transfer. This includes minting
     * and burning.
     *
     * Calling conditions:
     *
     * - When `from` and `to` are both non-zero, ``from``'s `tokenId` will be
     * transferred to `to`.
     * - When `from` is zero, `tokenId` will be minted for `to`.
     * - When `to` is zero, ``from``'s `tokenId` will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual {}

    /**
     * @dev Hook that is called after any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _afterTokenTransfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual {}
}

// File: contracts/lib/Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (access/Ownable.sol)
// extended with nominateNewOwner() and acceptOwnership()

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/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;
    address public nominatedOwner;

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

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

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

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

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

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

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

    /**
     * @dev more secure approach : nominate new owner,
     * then let nominated owner take ownership
     */
    function nominateNewOwner(address _nominatedOwner) external onlyOwner {
        nominatedOwner = _nominatedOwner;
        emit OwnerNominated(_nominatedOwner);
    }

    function acceptOwnership() external {
        require(msg.sender == nominatedOwner, "You must be nominated before you can accept ownership");
        _owner = nominatedOwner;
        nominatedOwner = address(0);
        emit OwnershipTransferred(_owner, nominatedOwner);
    }
}

// File: contracts/ERC721StakingPool.sol



// SPDX-License-Identifier: AGPL-3.0

pragma solidity ^0.8.4;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721Receiver.sol";
import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";

import { Clone } from "./lib/Clone.sol";
import { Ownable } from "./lib/Ownable.sol";
import { FullMath } from "./lib/FullMath.sol";

/// @title ERC721StakingPool
/// @author zefram.eth
/// @notice A modern, gas optimized staking pool contract for rewarding ERC721 stakers
/// with ERC20 tokens periodically and continuously
contract ERC721StakingPool is Ownable, Clone, IERC721Receiver {
    /// -----------------------------------------------------------------------
    /// Library usage
    /// -----------------------------------------------------------------------

    using SafeERC20 for ERC20;

    /// -----------------------------------------------------------------------
    /// Errors
    /// -----------------------------------------------------------------------

    error Error_ZeroOwner();
    error Error_AlreadyInitialized();
    error Error_NotRewardDistributor();
    error Error_AmountTooLarge();
    error Error_NotTokenOwner();
    error Error_NotStakeToken();

    /// -----------------------------------------------------------------------
    /// Events
    /// -----------------------------------------------------------------------

    event RewardAdded(uint256 reward);
    event Staked(address indexed user, uint256[] idList);
    event Withdrawn(address indexed user, uint256[] idList);
    event RewardPaid(address indexed user, uint256 reward);

    /// -----------------------------------------------------------------------
    /// Constants
    /// -----------------------------------------------------------------------

    uint256 internal constant PRECISION = 1e30;
    address internal constant BURN_ADDRESS = address(0xdead);

    /// -----------------------------------------------------------------------
    /// Storage variables
    /// -----------------------------------------------------------------------

    /// @notice The last Unix timestamp (in seconds) when rewardPerTokenStored was updated
    uint64 public lastUpdateTime;
    /// @notice The Unix timestamp (in seconds) at which the current reward period ends
    uint64 public periodFinish;

    /// @notice The per-second rate at which rewardPerToken increases
    uint256 public rewardRate;
    /// @notice The last stored rewardPerToken value
    uint256 public rewardPerTokenStored;
    /// @notice The total tokens staked in the pool
    uint256 public totalSupply;

    /// @notice Tracks if an address can call notifyReward()
    mapping(address => bool) public isRewardDistributor;
    /// @notice The owner of a staked ERC721 token
    mapping(uint256 => address) public ownerOf;

    /// @notice The amount of tokens staked by an account
    mapping(address => uint256) public balanceOf;
    /// @notice The rewardPerToken value when an account last staked/withdrew/withdrew rewards
    mapping(address => uint256) public userRewardPerTokenPaid;
    /// @notice The earned() value when an account last staked/withdrew/withdrew rewards
    mapping(address => uint256) public rewards;

    /// -----------------------------------------------------------------------
    /// Immutable parameters
    /// -----------------------------------------------------------------------

    /// @notice The token being rewarded to stakers
    function rewardToken() public pure returns (ERC20 rewardToken_) {
        return ERC20(_getArgAddress(0));
    }

    /// @notice The token being staked in the pool
    function stakeToken() public pure returns (ERC721 stakeToken_) {
        return ERC721(_getArgAddress(0x14));
    }

    /// @notice The length of each reward period, in seconds
    function DURATION() public pure returns (uint64 DURATION_) {
        return _getArgUint64(0x28);
    }

    /// -----------------------------------------------------------------------
    /// Initialization
    /// -----------------------------------------------------------------------

    /// @notice Initializes the owner, called by StakingPoolFactory
    /// @param initialOwner The initial owner of the contract
    function initialize(address initialOwner) external {
        if (owner() != address(0)) {
            revert Error_AlreadyInitialized();
        }
        if (initialOwner == address(0)) {
            revert Error_ZeroOwner();
        }

        _transferOwnership(initialOwner);
    }

    /// -----------------------------------------------------------------------
    /// User actions
    /// -----------------------------------------------------------------------

    /// @notice Stakes a list of ERC721 tokens in the pool to earn rewards
    /// @param idList The list of ERC721 token IDs to stake
    function stake(uint256[] calldata idList) external {
        /// -----------------------------------------------------------------------
        /// Validation
        /// -----------------------------------------------------------------------

        if (idList.length == 0) {
            return;
        }

        /// -----------------------------------------------------------------------
        /// Storage loads
        /// -----------------------------------------------------------------------

        uint256 accountBalance = balanceOf[msg.sender];
        uint64 lastTimeRewardApplicable_ = lastTimeRewardApplicable();
        uint256 totalSupply_ = totalSupply;
        uint256 rewardPerToken_ = _rewardPerToken(totalSupply_, lastTimeRewardApplicable_, rewardRate);

        /// -----------------------------------------------------------------------
        /// State updates
        /// -----------------------------------------------------------------------

        // accrue rewards
        rewardPerTokenStored = rewardPerToken_;
        lastUpdateTime = lastTimeRewardApplicable_;
        rewards[msg.sender] = _earned(msg.sender, accountBalance, rewardPerToken_, rewards[msg.sender]);
        userRewardPerTokenPaid[msg.sender] = rewardPerToken_;

        // stake
        totalSupply = totalSupply_ + idList.length;
        balanceOf[msg.sender] = accountBalance + idList.length;
        unchecked {
            for (uint256 i = 0; i < idList.length; i++) {
                ownerOf[idList[i]] = msg.sender;
            }
        }

        /// -----------------------------------------------------------------------
        /// Effects
        /// -----------------------------------------------------------------------

        unchecked {
            for (uint256 i = 0; i < idList.length; i++) {
                stakeToken().safeTransferFrom(msg.sender, address(this), idList[i]);
            }
        }

        emit Staked(msg.sender, idList);
    }

    /// @notice Withdraws staked tokens from the pool
    /// @param idList The list of ERC721 token IDs to stake
    function withdraw(uint256[] calldata idList) external {
        /// -----------------------------------------------------------------------
        /// Validation
        /// -----------------------------------------------------------------------

        if (idList.length == 0) {
            return;
        }

        /// -----------------------------------------------------------------------
        /// Storage loads
        /// -----------------------------------------------------------------------

        uint256 accountBalance = balanceOf[msg.sender];
        uint64 lastTimeRewardApplicable_ = lastTimeRewardApplicable();
        uint256 totalSupply_ = totalSupply;
        uint256 rewardPerToken_ = _rewardPerToken(totalSupply_, lastTimeRewardApplicable_, rewardRate);

        /// -----------------------------------------------------------------------
        /// State updates
        /// -----------------------------------------------------------------------

        // accrue rewards
        rewardPerTokenStored = rewardPerToken_;
        lastUpdateTime = lastTimeRewardApplicable_;
        rewards[msg.sender] = _earned(msg.sender, accountBalance, rewardPerToken_, rewards[msg.sender]);
        userRewardPerTokenPaid[msg.sender] = rewardPerToken_;

        // withdraw stake
        balanceOf[msg.sender] = accountBalance - idList.length;
        // total supply has 1:1 relationship with staked amounts
        // so can't ever underflow
        unchecked {
            totalSupply = totalSupply_ - idList.length;
            for (uint256 i = 0; i < idList.length; i++) {
                // verify ownership
                address tokenOwner = ownerOf[idList[i]];
                if (tokenOwner != msg.sender || tokenOwner == BURN_ADDRESS) {
                    revert Error_NotTokenOwner();
                }

                // keep the storage slot dirty to save gas
                // if someone else stakes the same token again
                ownerOf[idList[i]] = BURN_ADDRESS;
            }
        }

        /// -----------------------------------------------------------------------
        /// Effects
        /// -----------------------------------------------------------------------

        unchecked {
            for (uint256 i = 0; i < idList.length; i++) {
                stakeToken().safeTransferFrom(address(this), msg.sender, idList[i]);
            }
        }

        emit Withdrawn(msg.sender, idList);
    }

    /// @notice Withdraws specified staked tokens and earned rewards
    function exit(uint256[] calldata idList) external {
        /// -----------------------------------------------------------------------
        /// Validation
        /// -----------------------------------------------------------------------

        if (idList.length == 0) {
            return;
        }

        /// -----------------------------------------------------------------------
        /// Storage loads
        /// -----------------------------------------------------------------------

        uint256 accountBalance = balanceOf[msg.sender];
        uint64 lastTimeRewardApplicable_ = lastTimeRewardApplicable();
        uint256 totalSupply_ = totalSupply;
        uint256 rewardPerToken_ = _rewardPerToken(totalSupply_, lastTimeRewardApplicable_, rewardRate);

        /// -----------------------------------------------------------------------
        /// State updates
        /// -----------------------------------------------------------------------

        // give rewards
        uint256 reward = _earned(msg.sender, accountBalance, rewardPerToken_, rewards[msg.sender]);
        if (reward > 0) {
            rewards[msg.sender] = 0;
        }

        // accrue rewards
        rewardPerTokenStored = rewardPerToken_;
        lastUpdateTime = lastTimeRewardApplicable_;
        userRewardPerTokenPaid[msg.sender] = rewardPerToken_;

        // withdraw stake
        balanceOf[msg.sender] = accountBalance - idList.length;
        // total supply has 1:1 relationship with staked amounts
        // so can't ever underflow
        unchecked {
            totalSupply = totalSupply_ - idList.length;
            for (uint256 i = 0; i < idList.length; i++) {
                // verify ownership
                address tokenOwner = ownerOf[idList[i]];
                if (tokenOwner != msg.sender || tokenOwner == BURN_ADDRESS) {
                    revert Error_NotTokenOwner();
                }

                // keep the storage slot dirty to save gas
                // if someone else stakes the same token again
                ownerOf[idList[i]] = BURN_ADDRESS;
            }
        }

        /// -----------------------------------------------------------------------
        /// Effects
        /// -----------------------------------------------------------------------

        // transfer stake
        unchecked {
            for (uint256 i = 0; i < idList.length; i++) {
                stakeToken().safeTransferFrom(address(this), msg.sender, idList[i]);
            }
        }
        emit Withdrawn(msg.sender, idList);

        // transfer rewards
        if (reward > 0) {
            rewardToken().safeTransfer(msg.sender, reward);
            emit RewardPaid(msg.sender, reward);
        }
    }

    /// @notice Withdraws all earned rewards
    function getReward() external {
        /// -----------------------------------------------------------------------
        /// Storage loads
        /// -----------------------------------------------------------------------

        uint256 accountBalance = balanceOf[msg.sender];
        uint64 lastTimeRewardApplicable_ = lastTimeRewardApplicable();
        uint256 totalSupply_ = totalSupply;
        uint256 rewardPerToken_ = _rewardPerToken(totalSupply_, lastTimeRewardApplicable_, rewardRate);

        /// -----------------------------------------------------------------------
        /// State updates
        /// -----------------------------------------------------------------------

        uint256 reward = _earned(msg.sender, accountBalance, rewardPerToken_, rewards[msg.sender]);

        // accrue rewards
        rewardPerTokenStored = rewardPerToken_;
        lastUpdateTime = lastTimeRewardApplicable_;
        userRewardPerTokenPaid[msg.sender] = rewardPerToken_;

        // withdraw rewards
        if (reward > 0) {
            rewards[msg.sender] = 0;

            /// -----------------------------------------------------------------------
            /// Effects
            /// -----------------------------------------------------------------------

            rewardToken().safeTransfer(msg.sender, reward);
            emit RewardPaid(msg.sender, reward);
        }
    }

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

    /// @notice The latest time at which stakers are earning rewards.
    function lastTimeRewardApplicable() public view returns (uint64) {
        return block.timestamp < periodFinish ? uint64(block.timestamp) : periodFinish;
    }

    /// @notice The amount of reward tokens each staked token has earned so far
    function rewardPerToken() external view returns (uint256) {
        return _rewardPerToken(totalSupply, lastTimeRewardApplicable(), rewardRate);
    }

    /// @notice The amount of reward tokens an account has accrued so far. Does not
    /// include already withdrawn rewards.
    function earned(address account) external view returns (uint256) {
        return
            _earned(
                account,
                balanceOf[account],
                _rewardPerToken(totalSupply, lastTimeRewardApplicable(), rewardRate),
                rewards[account]
            );
    }

    /// @dev ERC721 compliance
    function onERC721Received(
        address,
        address,
        uint256,
        bytes calldata
    ) external view override returns (bytes4) {
        if (msg.sender != address(stakeToken())) {
            revert Error_NotStakeToken();
        }
        return this.onERC721Received.selector;
    }

    /// -----------------------------------------------------------------------
    /// Owner actions
    /// -----------------------------------------------------------------------

    /// @notice Lets a reward distributor start a new reward period. The reward tokens must have already
    /// been transferred to this contract before calling this function. If it is called
    /// when a reward period is still active, a new reward period will begin from the time
    /// of calling this function, using the leftover rewards from the old reward period plus
    /// the newly sent rewards as the reward.
    /// @dev If the reward amount will cause an overflow when computing rewardPerToken, then
    /// this function will revert.
    /// @param reward The amount of reward tokens to use in the new reward period.
    function notifyRewardAmount(uint256 reward) external {
        /// -----------------------------------------------------------------------
        /// Validation
        /// -----------------------------------------------------------------------

        if (reward == 0) {
            return;
        }
        if (!isRewardDistributor[msg.sender]) {
            revert Error_NotRewardDistributor();
        }

        /// -----------------------------------------------------------------------
        /// Storage loads
        /// -----------------------------------------------------------------------

        uint256 rewardRate_ = rewardRate;
        uint64 periodFinish_ = periodFinish;
        uint64 lastTimeRewardApplicable_ = block.timestamp < periodFinish_ ? uint64(block.timestamp) : periodFinish_;
        uint64 DURATION_ = DURATION();
        uint256 totalSupply_ = totalSupply;

        /// -----------------------------------------------------------------------
        /// State updates
        /// -----------------------------------------------------------------------

        // accrue rewards
        rewardPerTokenStored = _rewardPerToken(totalSupply_, lastTimeRewardApplicable_, rewardRate_);
        lastUpdateTime = lastTimeRewardApplicable_;

        // record new reward
        uint256 newRewardRate;
        if (block.timestamp >= periodFinish_) {
            newRewardRate = reward / DURATION_;
        } else {
            uint256 remaining = periodFinish_ - block.timestamp;
            uint256 leftover = remaining * rewardRate_;
            newRewardRate = (reward + leftover) / DURATION_;
        }
        // prevent overflow when computing rewardPerToken
        if (newRewardRate >= ((type(uint256).max / PRECISION) / DURATION_)) {
            revert Error_AmountTooLarge();
        }
        rewardRate = newRewardRate;
        lastUpdateTime = uint64(block.timestamp);
        periodFinish = uint64(block.timestamp + DURATION_);

        emit RewardAdded(reward);
    }

    /// @notice Lets the owner add/remove accounts from the list of reward distributors.
    /// Reward distributors can call notifyRewardAmount()
    /// @param rewardDistributor The account to add/remove
    /// @param isRewardDistributor_ True to add the account, false to remove the account
    function setRewardDistributor(address rewardDistributor, bool isRewardDistributor_) external onlyOwner {
        isRewardDistributor[rewardDistributor] = isRewardDistributor_;
    }

    /// -----------------------------------------------------------------------
    /// Internal functions
    /// -----------------------------------------------------------------------

    function _earned(
        address account,
        uint256 accountBalance,
        uint256 rewardPerToken_,
        uint256 accountRewards
    ) internal view returns (uint256) {
        return
            FullMath.mulDiv(accountBalance, rewardPerToken_ - userRewardPerTokenPaid[account], PRECISION) +
            accountRewards;
    }

    function _rewardPerToken(
        uint256 totalSupply_,
        uint256 lastTimeRewardApplicable_,
        uint256 rewardRate_
    ) internal view returns (uint256) {
        if (totalSupply_ == 0) {
            return rewardPerTokenStored;
        }
        return
            rewardPerTokenStored +
            FullMath.mulDiv((lastTimeRewardApplicable_ - lastUpdateTime) * PRECISION, rewardRate_, totalSupply_);
    }

    function _getImmutableVariablesOffset() internal pure returns (uint256 offset) {
        assembly {
            offset := sub(calldatasize(), add(shr(240, calldataload(sub(calldatasize(), 2))), 2))
        }
    }
}

// File: contracts/lib/ClonesWithCallData.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

library ClonesWithCallData {
    function cloneWithCallDataProvision(address implementation, bytes memory data) internal returns (address instance) {
        // unrealistic for memory ptr or data length to exceed 256 bits
        unchecked {
            uint256 extraLength = data.length + 2; // +2 bytes for telling how much data there is appended to the call
            uint256 creationSize = 0x43 + extraLength;
            uint256 runSize = creationSize - 11;
            uint256 dataPtr;
            uint256 ptr;
            // solhint-disable-next-line no-inline-assembly
            assembly {
                ptr := mload(0x40)

                // -------------------------------------------------------------------------------------------------------------
                // CREATION (11 bytes)
                // -------------------------------------------------------------------------------------------------------------

                // 3d          | RETURNDATASIZE        | 0                       | –
                // 61 runtime  | PUSH2 runtime (r)     | r 0                     | –
                mstore(ptr, 0x3d61000000000000000000000000000000000000000000000000000000000000)
                mstore(add(ptr, 0x02), shl(240, runSize)) // size of the contract running bytecode (16 bits)

                // creation size = 0b
                // 80          | DUP1                  | r r 0                   | –
                // 60 creation | PUSH1 creation (c)    | c r r 0                 | –
                // 3d          | RETURNDATASIZE        | 0 c r r 0               | –
                // 39          | CODECOPY              | r 0                     | [0-2d]: runtime code
                // 81          | DUP2                  | 0 c  0                  | [0-2d]: runtime code
                // f3          | RETURN                | 0                       | [0-2d]: runtime code
                mstore(add(ptr, 0x04), 0x80600b3d3981f300000000000000000000000000000000000000000000000000)

                // -------------------------------------------------------------------------------------------------------------
                // RUNTIME
                // -------------------------------------------------------------------------------------------------------------

                // 36          | CALLDATASIZE          | cds                     | –
                // 3d          | RETURNDATASIZE        | 0 cds                   | –
                // 3d          | RETURNDATASIZE        | 0 0 cds                 | –
                // 37          | CALLDATACOPY          | –                       | [0, cds] = calldata
                // 61          | PUSH2 extra           | extra                   | [0, cds] = calldata
                mstore(add(ptr, 0x0b), 0x363d3d3761000000000000000000000000000000000000000000000000000000)
                mstore(add(ptr, 0x10), shl(240, extraLength))

                // 60 0x38     | PUSH1 0x38            | 0x38 extra              | [0, cds] = calldata // 0x38 (56) is runtime size - data
                // 36          | CALLDATASIZE          | cds 0x38 extra          | [0, cds] = calldata
                // 39          | CODECOPY              | _                       | [0, cds] = calldata
                // 3d          | RETURNDATASIZE        | 0                       | [0, cds] = calldata
                // 3d          | RETURNDATASIZE        | 0 0                     | [0, cds] = calldata
                // 3d          | RETURNDATASIZE        | 0 0 0                   | [0, cds] = calldata
                // 36          | CALLDATASIZE          | cds 0 0 0               | [0, cds] = calldata
                // 61 extra    | PUSH2 extra           | extra cds 0 0 0         | [0, cds] = calldata
                mstore(add(ptr, 0x12), 0x603836393d3d3d36610000000000000000000000000000000000000000000000)
                mstore(add(ptr, 0x1b), shl(240, extraLength))

                // 01          | ADD                   | cds+extra 0 0 0         | [0, cds] = calldata
                // 3d          | RETURNDATASIZE        | 0 cds 0 0 0             | [0, cds] = calldata
                // 73 addr     | PUSH20 0x123…         | addr 0 cds 0 0 0        | [0, cds] = calldata
                mstore(add(ptr, 0x1d), 0x013d730000000000000000000000000000000000000000000000000000000000)
                mstore(add(ptr, 0x20), shl(0x60, implementation))

                // 5a          | GAS                   | gas addr 0 cds 0 0 0    | [0, cds] = calldata
                // f4          | DELEGATECALL          | success 0               | [0, cds] = calldata
                // 3d          | RETURNDATASIZE        | rds success 0           | [0, cds] = calldata
                // 82          | DUP3                  | 0 rds success 0         | [0, cds] = calldata
                // 80          | DUP1                  | 0 0 rds success 0       | [0, cds] = calldata
                // 3e          | RETURNDATACOPY        | success 0               | [0, rds] = return data (there might be some irrelevant leftovers in memory [rds, cds] when rds < cds)
                // 90          | SWAP1                 | 0 success               | [0, rds] = return data
                // 3d          | RETURNDATASIZE        | rds 0 success           | [0, rds] = return data
                // 91          | SWAP2                 | success 0 rds           | [0, rds] = return data
                // 60 0x36     | PUSH1 0x36            | 0x36 sucess 0 rds       | [0, rds] = return data
                // 57          | JUMPI                 | 0 rds                   | [0, rds] = return data
                // fd          | REVERT                | –                       | [0, rds] = return data
                // 5b          | JUMPDEST              | 0 rds                   | [0, rds] = return data
                // f3          | RETURN                | –                       | [0, rds] = return data

                mstore(add(ptr, 0x34), 0x5af43d82803e903d91603657fd5bf30000000000000000000000000000000000)
            }

            // -------------------------------------------------------------------------------------------------------------
            // APPENDED DATA (Accessible from extcodecopy)
            // (but also send as appended data to the delegatecall)
            // -------------------------------------------------------------------------------------------------------------

            extraLength -= 2;
            uint256 counter = extraLength;
            uint256 copyPtr = ptr + 0x43;
            // solhint-disable-next-line no-inline-assembly
            assembly {
                dataPtr := add(data, 32)
            }
            for (; counter >= 32; counter -= 32) {
                // solhint-disable-next-line no-inline-assembly
                assembly {
                    mstore(copyPtr, mload(dataPtr))
                }

                copyPtr += 32;
                dataPtr += 32;
            }
            uint256 mask = ~(256**(32 - counter) - 1);
            // solhint-disable-next-line no-inline-assembly
            assembly {
                mstore(copyPtr, and(mload(dataPtr), mask))
            }
            copyPtr += counter;
            // solhint-disable-next-line no-inline-assembly
            assembly {
                mstore(copyPtr, shl(240, extraLength))
            }
            // solhint-disable-next-line no-inline-assembly
            assembly {
                instance := create(0, ptr, creationSize)
            }
            require(instance != address(0), "create failed");
        }
    }
}

// File: @openzeppelin/contracts/token/ERC721/IERC721.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/IERC721.sol)

pragma solidity ^0.8.0;

import "../../utils/introspection/IERC165.sol";

/**
 * @dev Required interface of an ERC721 compliant contract.
 */
interface IERC721 is IERC165 {
    /**
     * @dev Emitted when `tokenId` token is transferred from `from` to `to`.
     */
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables `approved` to manage the `tokenId` token.
     */
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables or disables (`approved`) `operator` to manage all of its assets.
     */
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    /**
     * @dev Returns the number of tokens in ``owner``'s account.
     */
    function balanceOf(address owner) external view returns (uint256 balance);

    /**
     * @dev Returns the owner of the `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function ownerOf(uint256 tokenId) external view returns (address owner);

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be have been allowed to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

    /**
     * @dev Transfers `tokenId` token from `from` to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {safeTransferFrom} whenever possible.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

    /**
     * @dev Gives permission to `to` to transfer `tokenId` token to another account.
     * The approval is cleared when the token is transferred.
     *
     * Only a single account can be approved at a time, so approving the zero address clears previous approvals.
     *
     * Requirements:
     *
     * - The caller must own the token or be an approved operator.
     * - `tokenId` must exist.
     *
     * Emits an {Approval} event.
     */
    function approve(address to, uint256 tokenId) external;

    /**
     * @dev Returns the account approved for `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function getApproved(uint256 tokenId) external view returns (address operator);

    /**
     * @dev Approve or remove `operator` as an operator for the caller.
     * Operators can call {transferFrom} or {safeTransferFrom} for any token owned by the caller.
     *
     * Requirements:
     *
     * - The `operator` cannot be the caller.
     *
     * Emits an {ApprovalForAll} event.
     */
    function setApprovalForAll(address operator, bool _approved) external;

    /**
     * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
     *
     * See {setApprovalForAll}
     */
    function isApprovedForAll(address owner, address operator) external view returns (bool);

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes calldata data
    ) external;
}

// File: @openzeppelin/contracts/token/ERC721/IERC721Receiver.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/IERC721Receiver.sol)

pragma solidity ^0.8.0;

/**
 * @title ERC721 token receiver interface
 * @dev Interface for any contract that wants to support safeTransfers
 * from ERC721 asset contracts.
 */
interface IERC721Receiver {
    /**
     * @dev Whenever an {IERC721} `tokenId` token is transferred to this contract via {IERC721-safeTransferFrom}
     * by `operator` from `from`, this function is called.
     *
     * It must return its Solidity selector to confirm the token transfer.
     * If any other value is returned or the interface is not implemented by the recipient, the transfer will be reverted.
     *
     * The selector can be obtained in Solidity with `IERC721.onERC721Received.selector`.
     */
    function onERC721Received(
        address operator,
        address from,
        uint256 tokenId,
        bytes calldata data
    ) external returns (bytes4);
}

// File: @openzeppelin/contracts/token/ERC721/extensions/IERC721Metadata.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/extensions/IERC721Metadata.sol)

pragma solidity ^0.8.0;

import "../IERC721.sol";

/**
 * @title ERC-721 Non-Fungible Token Standard, optional metadata extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
interface IERC721Metadata is IERC721 {
    /**
     * @dev Returns the token collection name.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the token collection symbol.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the Uniform Resource Identifier (URI) for `tokenId` token.
     */
    function tokenURI(uint256 tokenId) external view returns (string memory);
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (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 functionCall(target, data, "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");
        require(isContract(target), "Address: call to non-contract");

        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResult(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) {
        require(isContract(target), "Address: static call to non-contract");

        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResult(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) {
        require(isContract(target), "Address: delegate call to non-contract");

        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason 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 {
            // 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

                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/Strings.sol



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

pragma solidity ^0.8.0;

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

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

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

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

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

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



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

pragma solidity ^0.8.0;

import "./IERC165.sol";

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

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



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

pragma solidity ^0.8.0;

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

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/ERC20.sol)

pragma solidity ^0.8.0;

import "./IERC20.sol";
import "./extensions/IERC20Metadata.sol";
import "../../utils/Context.sol";

/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin Contracts guidelines: functions revert
 * instead returning `false` on failure. This behavior is nonetheless
 * conventional and does not conflict with the expectations of ERC20
 * applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20, IERC20Metadata {
    mapping(address => uint256) private _balances;

    mapping(address => mapping(address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;

    /**
     * @dev Sets the values for {name} and {symbol}.
     *
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5.05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless this function is
     * overridden;
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual override returns (uint8) {
        return 18;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address to, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _transfer(owner, to, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * NOTE: If `amount` is the maximum `uint256`, the allowance is not updated on
     * `transferFrom`. This is semantically equivalent to an infinite approval.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _approve(owner, spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * NOTE: Does not update the allowance if the current allowance
     * is the maximum `uint256`.
     *
     * Requirements:
     *
     * - `from` and `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     * - the caller must have allowance for ``from``'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) public virtual override returns (bool) {
        address spender = _msgSender();
        _spendAllowance(from, spender, amount);
        _transfer(from, to, amount);
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        address owner = _msgSender();
        _approve(owner, spender, _allowances[owner][spender] + addedValue);
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        address owner = _msgSender();
        uint256 currentAllowance = _allowances[owner][spender];
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(owner, spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `sender` to `recipient`.
     *
     * This internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     */
    function _transfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {
        require(from != address(0), "ERC20: transfer from the zero address");
        require(to != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(from, to, amount);

        uint256 fromBalance = _balances[from];
        require(fromBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[from] = fromBalance - amount;
        }
        _balances[to] += amount;

        emit Transfer(from, to, amount);

        _afterTokenTransfer(from, to, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

        _totalSupply += amount;
        _balances[account] += amount;
        emit Transfer(address(0), account, amount);

        _afterTokenTransfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        uint256 accountBalance = _balances[account];
        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
        unchecked {
            _balances[account] = accountBalance - amount;
        }
        _totalSupply -= amount;

        emit Transfer(account, address(0), amount);

        _afterTokenTransfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Spend `amount` form the allowance of `owner` toward `spender`.
     *
     * Does not update the allowance amount in case of infinite allowance.
     * Revert if not enough allowance is available.
     *
     * Might emit an {Approval} event.
     */
    function _spendAllowance(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        uint256 currentAllowance = allowance(owner, spender);
        if (currentAllowance != type(uint256).max) {
            require(currentAllowance >= amount, "ERC20: insufficient allowance");
            unchecked {
                _approve(owner, spender, currentAllowance - amount);
            }
        }
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}

    /**
     * @dev Hook that is called after any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * has been transferred to `to`.
     * - when `from` is zero, `amount` tokens have been minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens have been burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _afterTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

import "../IERC20.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));
        }
    }

    /**
     * @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: contracts/lib/Clone.sol



// SPDX-License-Identifier: BSD
pragma solidity ^0.8.4;

/// @title Clone
/// @author zefram.eth
/// @notice Provides helper functions for reading immutable args from calldata
contract Clone {
    /// @notice Reads an immutable arg with type address
    /// @param argOffset The offset of the arg in the packed data
    /// @return arg The arg value
    function _getArgAddress(uint256 argOffset) internal pure returns (address arg) {
        uint256 offset = _getImmutableArgsOffset();
        // solhint-disable-next-line no-inline-assembly
        assembly {
            arg := shr(0x60, calldataload(add(offset, argOffset)))
        }
    }

    /// @notice Reads an immutable arg with type uint256
    /// @param argOffset The offset of the arg in the packed data
    /// @return arg The arg value
    function _getArgUint256(uint256 argOffset) internal pure returns (uint256 arg) {
        uint256 offset = _getImmutableArgsOffset();
        // solhint-disable-next-line no-inline-assembly
        assembly {
            arg := calldataload(add(offset, argOffset))
        }
    }

    /// @notice Reads a uint256 array stored in the immutable args.
    /// @param argOffset The offset of the arg in the packed data
    /// @param arrLen Number of elements in the array
    /// @return arr The array
    function _getArgUint256Array(uint256 argOffset, uint64 arrLen) internal pure returns (uint256[] memory arr) {
        uint256 offset = _getImmutableArgsOffset();
        uint256 el;
        arr = new uint256[](arrLen);
        for (uint64 i = 0; i < arrLen; i++) {
            assembly {
                // solhint-disable-next-line no-inline-assembly
                el := calldataload(add(add(offset, argOffset), mul(i, 32)))
            }
            arr[i] = el;
        }
        return arr;
    }

    /// @notice Reads an immutable arg with type uint64
    /// @param argOffset The offset of the arg in the packed data
    /// @return arg The arg value
    function _getArgUint64(uint256 argOffset) internal pure returns (uint64 arg) {
        uint256 offset = _getImmutableArgsOffset();
        // solhint-disable-next-line no-inline-assembly
        assembly {
            arg := shr(0xc0, calldataload(add(offset, argOffset)))
        }
    }

    /// @notice Reads an immutable arg with type uint8
    /// @param argOffset The offset of the arg in the packed data
    /// @return arg The arg value
    function _getArgUint8(uint256 argOffset) internal pure returns (uint8 arg) {
        uint256 offset = _getImmutableArgsOffset();
        // solhint-disable-next-line no-inline-assembly
        assembly {
            arg := shr(0xf8, calldataload(add(offset, argOffset)))
        }
    }

    /// @return offset The offset of the packed immutable args in calldata
    function _getImmutableArgsOffset() internal pure returns (uint256 offset) {
        // solhint-disable-next-line no-inline-assembly
        assembly {
            offset := sub(calldatasize(), add(shr(240, calldataload(sub(calldatasize(), 2))), 2))
        }
    }
}

// File: contracts/lib/FullMath.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.8.0;

/// @title Contains 512-bit math functions
/// @notice Facilitates multiplication and division that can have overflow of an intermediate value without any loss of precision
/// @dev Handles "phantom overflow" i.e., allows multiplication and division where an intermediate value overflows 256 bits
library FullMath {
    /// @notice Calculates floor(a×b÷denominator) with full precision. Throws if result overflows a uint256 or denominator == 0
    /// @param a The multiplicand
    /// @param b The multiplier
    /// @param denominator The divisor
    /// @return result The 256-bit result
    /// @dev Credit to Remco Bloemen under MIT license https://xn--2-umb.com/21/muldiv
    function mulDiv(
        uint256 a,
        uint256 b,
        uint256 denominator
    ) internal pure returns (uint256 result) {
        unchecked {
            // 512-bit multiply [prod1 prod0] = a * b
            // Compute the product mod 2**256 and mod 2**256 - 1
            // then use the Chinese Remainder Theorem to reconstruct
            // the 512 bit result. The result is stored in two 256
            // variables such that product = prod1 * 2**256 + prod0
            uint256 prod0; // Least significant 256 bits of the product
            uint256 prod1; // Most significant 256 bits of the product
            assembly {
                let mm := mulmod(a, b, not(0))
                prod0 := mul(a, b)
                prod1 := sub(sub(mm, prod0), lt(mm, prod0))
            }

            // Handle non-overflow cases, 256 by 256 division
            if (prod1 == 0) {
                require(denominator > 0);
                assembly {
                    result := div(prod0, denominator)
                }
                return result;
            }

            // Make sure the result is less than 2**256.
            // Also prevents denominator == 0
            require(denominator > prod1);

            ///////////////////////////////////////////////
            // 512 by 256 division.
            ///////////////////////////////////////////////

            // Make division exact by subtracting the remainder from [prod1 prod0]
            // Compute remainder using mulmod
            uint256 remainder;
            assembly {
                remainder := mulmod(a, b, denominator)
            }
            // Subtract 256 bit number from 512 bit number
            assembly {
                prod1 := sub(prod1, gt(remainder, prod0))
                prod0 := sub(prod0, remainder)
            }

            // Factor powers of two out of denominator
            // Compute largest power of two divisor of denominator.
            // Always >= 1.
            uint256 twos = (type(uint256).max - denominator + 1) & denominator;
            // Divide denominator by power of two
            assembly {
                denominator := div(denominator, twos)
            }

            // Divide [prod1 prod0] by the factors of two
            assembly {
                prod0 := div(prod0, twos)
            }
            // Shift in bits from prod1 into prod0. For this we need
            // to flip `twos` such that it is 2**256 / twos.
            // If twos is zero, then it becomes one
            assembly {
                twos := add(div(sub(0, twos), twos), 1)
            }
            prod0 |= prod1 * twos;

            // Invert denominator mod 2**256
            // Now that denominator is an odd number, it has an inverse
            // modulo 2**256 such that denominator * inv = 1 mod 2**256.
            // Compute the inverse by starting with a seed that is correct
            // correct for four bits. That is, denominator * inv = 1 mod 2**4
            uint256 inv = (3 * denominator) ^ 2;
            // Now use Newton-Raphson iteration to improve the precision.
            // Thanks to Hensel's lifting lemma, this also works in modular
            // arithmetic, doubling the correct bits in each step.
            inv *= 2 - denominator * inv; // inverse mod 2**8
            inv *= 2 - denominator * inv; // inverse mod 2**16
            inv *= 2 - denominator * inv; // inverse mod 2**32
            inv *= 2 - denominator * inv; // inverse mod 2**64
            inv *= 2 - denominator * inv; // inverse mod 2**128
            inv *= 2 - denominator * inv; // inverse mod 2**256

            // Because the division is now exact we can divide by multiplying
            // with the modular inverse of denominator. This will give us the
            // correct result modulo 2**256. Since the precoditions guarantee
            // that the outcome is less than 2**256, this is the final result.
            // We don't need to compute the high bits of the result and prod1
            // is no longer required.
            result = prod0 * inv;
            return result;
        }
    }

    /// @notice Calculates ceil(a×b÷denominator) with full precision. Throws if result overflows a uint256 or denominator == 0
    /// @param a The multiplicand
    /// @param b The multiplier
    /// @param denominator The divisor
    /// @return result The 256-bit result
    function mulDivRoundingUp(
        uint256 a,
        uint256 b,
        uint256 denominator
    ) internal pure returns (uint256 result) {
        result = mulDiv(a, b, denominator);
        unchecked {
            if (mulmod(a, b, denominator) > 0) {
                require(result < type(uint256).max);
                result++;
            }
        }
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

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

    /**
     * @dev Moves `amount` tokens from the caller's account to `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);

    /**
     * @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);
}

// File: @openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20Metadata is IERC20 {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the symbol of the token.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the decimals places of the token.
     */
    function decimals() external view returns (uint8);
}