// File: /D/GIT/smart-contract-things/contracts/AgentDsSecretRoom.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "./ERC721TradableRandomMint.sol";

contract AgentDsSecretRoom is ERC721TradableRandomMint {
    string public contractURI;

    bool public isMetadataLocked = false;

    address public originalOwner;

    /**
     * @dev Throws if called by any account other than the original owner.
     */
    modifier onlyOriginalOwner() {
        require(originalOwner == _msgSender(), "Caller is not the original owner");
        _;
    }

    // They are watching you!

    constructor(address _proxyRegistryAddress)
        ERC721TradableRandomMint("Agent D's Secret Room", "ASR", _proxyRegistryAddress)
        
    {
        originalOwner = owner();
    }

    function lockContractMetadata() public onlyOriginalOwner {
        require(!isMetadataLocked, "The Contract has already been locked!");
        isMetadataLocked = true;
    }

    // One does not simply enter the basement!

    function setBaseUri(string memory uri) public onlyOriginalOwner {
        require(!isMetadataLocked, "The Contract has been locked, toughluck!");
        baseURI = uri;
    }

    // Don't eat those donuts!

    function setContractUri(string memory uri) public onlyOriginalOwner {
        require(!isMetadataLocked, "The Contract has been locked, toughluck!");
        contractURI = uri;
    }
}

// File: /D/GIT/smart-contract-things/contracts/DuckOwnerProxy.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

interface OpenStoreContract {
    function balanceOf(address _owner, uint256 _id) external view returns (uint256);
}

// quack-quack!

contract DuckOwnerProxy {
    address public openStoreNFTAddress;
    uint256 public baseNumber = 81051682759312351887842295081699468782319279963069916326007376000000000000000;
    uint56[333] public ducks = [
        uint56(214849514110977),
        uint56(215949025738753),
        uint56(218148048994305),
        uint56(483130351288321),
        uint56(220347072249857),
        uint56(482030839660545),
        uint56(222546095505409),
        uint56(223645607133185),
        uint56(224745118760961),
        uint56(225844630388737),
        uint56(226944142016513),
        uint56(228043653644289),
        uint56(229143165272065),
        uint56(230242676899841),
        uint56(231342188527617),
        uint56(232441700155393),
        uint56(233541211783169),
        uint56(234640723410945),
        uint56(235740235038721),
        uint56(237939258294273),
        uint56(236839746666497),
        uint56(239038769922049),
        uint56(240138281549825),
        uint56(241237793177601),
        uint56(242337304805377),
        uint56(243436816433153),
        uint56(244536328060929),
        uint56(245635839688705),
        uint56(246735351316481),
        uint56(247834862944257),
        uint56(248934374572033),
        uint56(250033886199809),
        uint56(251133397827585),
        uint56(252232909455361),
        uint56(253332421083137),
        uint56(254431932710913),
        uint56(255531444338689),
        uint56(256630955966465),
        uint56(257730467594241),
        uint56(258829979222017),
        uint56(259929490849793),
        uint56(261029002477569),
        uint56(262128514105345),
        uint56(263228025733121),
        uint56(264327537360897), // D
        uint56(265427048988673),
        uint56(266526560616449),
        uint56(267626072244225),
        uint56(268725583872001),
        uint56(269825095499777), // U
        uint56(270924607127553),
        uint56(272024118755329),
        uint56(273123630383105),
        uint56(274223142010881),
        uint56(275322653638657), // C
        uint56(276422165266433),
        uint56(277521676894209),
        uint56(278621188521985),
        uint56(279720700149761),
        uint56(280820211777537), // K
        uint56(281919723405313),
        uint56(283019235033089),
        uint56(284118746660865),
        uint56(285218258288641),
        uint56(286317769916417), // S
        uint56(287417281544193),
        uint56(288516793171969),
        uint56(289616304799745),
        uint56(290715816427521),
        uint56(291815328055297),
        uint56(292914839683073),
        uint56(294014351310849),
        uint56(295113862938625),
        uint56(296213374566401),
        uint56(297312886194177),
        uint56(298412397821953),
        uint56(299511909449729),
        uint56(554598607093761),
        uint56(301710932705281),
        uint56(302810444333057),
        uint56(303909955960833),
        uint56(305009467588609),
        uint56(306108979216385),
        uint56(307208490844161),
        uint56(308308002471937),
        uint56(309407514099713),
        uint56(310507025727489),
        uint56(311606537355265),
        uint56(312706048983041),
        uint56(313805560610817),
        uint56(314905072238593),
        uint56(316004583866369),
        uint56(317104095494145),
        uint56(318203607121921),
        uint56(319303118749697),
        uint56(320402630377473),
        uint56(321502142005249),
        uint56(322601653633025),
        uint56(323701165260801),
        uint56(324800676888577),
        uint56(325900188516353),
        uint56(326999700144129),
        uint56(328099211771905),
        uint56(329198723399681),
        uint56(330298235027457),
        uint56(331397746655233),
        uint56(332497258283009),
        uint56(333596769910785),
        uint56(334696281538561),
        uint56(335795793166337),
        uint56(336895304794113),
        uint56(337994816421889),
        uint56(339094328049665),
        uint56(340193839677441),
        uint56(341293351305217),
        uint56(342392862932993),
        uint56(343492374560769),
        uint56(344591886188545),
        uint56(345691397816321),
        uint56(346790909444097),
        uint56(347890421071873),
        uint56(348989932699649),
        uint56(354487490838529),
        uint56(350089444327425),
        uint56(351188955955201),
        uint56(352288467582977),
        uint56(353387979210753),
        uint56(367681630371841),
        uint56(366582118744065),
        uint56(365482607116289),
        uint56(364383095488513),
        uint56(363283583860737),
        uint56(362184072232961),
        uint56(361084560605185),
        uint56(359985048977409),
        uint56(358885537349633),
        uint56(357786025721857),
        uint56(356686514094081),
        uint56(355587002466305),
        uint56(434751839666177),
        uint56(486428886171649),
        uint56(436950862921729),
        uint56(487528397799425),
        uint56(439149886177281),
        uint56(488627909427201),
        uint56(490826932682753),
        uint56(442448421060609),
        uint56(491926444310529),
        uint56(444647444316161),
        uint56(601877607088129),
        uint56(446846467571713),
        uint56(500722537332737),
        uint56(449045490827265),
        uint56(480931328032769),
        uint56(451244514082817),
        uint56(506220095471617),
        uint56(453443537338369),
        uint56(454543048966145),
        uint56(455642560593921),
        uint56(456742072221697),
        uint56(511717653610497),
        uint56(458941095477249),
        uint56(515016188493825),
        uint56(461140118732801),
        uint56(550200560582657),
        uint56(496324490821633),
        uint56(464438653616129),
        uint56(551300072210433),
        uint56(466637676871681),
        uint56(467737188499457),
        uint56(523812281516033),
        uint56(524911793143809),
        uint56(479831816404993),
        uint56(526011304771585),
        uint56(544703002443777),
        uint56(473234746638337),
        uint56(533707886166017),
        uint56(501822048960513),
        uint56(508419118727169),
        uint56(534807397793793),
        uint56(477632793149441),
        uint56(478732304777217),
        uint56(535906909421569),
        uint56(541404467560449),
        uint56(522712769888257),
        uint56(540304955932673),
        uint56(539205444304897),
        uint56(507319607099393),
        uint56(538105932677121),
        uint56(497424002449409),
        uint56(519414235004929),
        uint56(521613258260481),
        uint56(498523514077185),
        uint56(499623025704961),
        uint56(502921560588289),
        uint56(537006421049345),
        uint56(532608374538241),
        uint56(510618141982721),
        uint56(509518630354945),
        uint56(300611421077505),
        uint56(520513746632705),
        uint56(531508862910465),
        uint56(504021072216065),
        uint56(530409351282689),
        uint56(528210328027137),
        uint56(527110816399361),
        uint56(529309839654913),
        uint56(505120583843841),
        uint56(493025955938305),
        uint56(517215211749377),
        uint56(494125467566081),
        uint56(516115700121601),
        uint56(513916676866049),
        uint56(489727421054977),
        uint56(575489328021505),
        uint56(602977118715905),
        uint56(580986886160385),
        uint56(604076630343681),
        uint56(545802514071553),
        uint56(605176141971457),
        uint56(552399583838209),
        uint56(546902025699329),
        uint56(606275653599233),
        uint56(607375165227009),
        uint56(597479560577025),
        uint56(608474676854785),
        uint56(548001537327105),
        uint56(599678583832577),
        uint56(609574188482561),
        uint56(553499095465985),
        uint56(610673700110337),
        uint56(611773211738113),
        uint56(579887374532609),
        uint56(612872723365889),
        uint56(564494211743745),
        uint56(549101048954881),
        uint56(585384932671489),
        uint56(556797630349313),
        uint56(613972234993665),
        uint56(615071746621441),
        uint56(616171258249217),
        uint56(617270769876993),
        uint56(589782979182593),
        uint56(583185909415937),
        uint56(618370281504769),
        uint56(619469793132545),
        uint56(620569304760321),
        uint56(621668816388097),
        uint56(584285421043713),
        uint56(557897141977089),
        uint56(622768328015873),
        uint56(590882490810369),
        uint56(623867839643649),
        uint56(582086397788161),
        uint56(561195676860417),
        uint56(563394700115969),
        uint56(624967351271425),
        uint56(567792746627073),
        uint56(555698118721537),
        uint56(573290304765953),
        uint56(565593723371521),
        uint56(626066862899201),
        uint56(588683467554817),
        uint56(577688351277057),
        uint56(627166374526977),
        uint56(628265886154753),
        uint56(600778095460353),
        uint56(578787862904833),
        uint56(574389816393729),
        uint56(598579072204801),
        uint56(629365397782529),
        uint56(566693234999297),
        uint56(630464909410305),
        uint56(571091281510401),
        uint56(586484444299265),
        uint56(558996653604865),
        uint56(572190793138177),
        uint56(631564421038081),
        uint56(562295188488193),
        uint56(632663932665857),
        uint56(633763444293633),
        uint56(587583955927041),
        uint56(568892258254849),
        uint56(569991769882625),
        uint56(634862955921409),
        uint56(635962467549185),
        uint56(593081514065921),
        uint56(576588839649281),
        uint56(591982002438145),
        uint56(637061979176961),
        uint56(638161490804737),
        uint56(560096165232641),
        uint56(594181025693697),
        uint56(639261002432513),
        uint56(595280537321473),
        uint56(640360514060289),
        uint56(642559537315841),
        uint56(596380048949249),
        uint56(484229862916097),
        uint56(485329374543873),
        uint56(683241467543553),
        uint56(683241467543553),
        uint56(684340979171329),
        uint56(685440490799105),
        uint56(686540002426881),
        uint56(646957583826945),
        uint56(648057095454721),
        uint56(687639514054657),
        uint56(688739025682433),
        uint56(689838537310209),
        uint56(643659048943617),
        uint56(649156607082497),
        uint56(644758560571393),
        uint56(690938048937985),
        uint56(645858072199169),
        uint56(692037560565761),
        uint56(693137072193537),
        uint56(694236583821313),
        uint56(695336095449089),
        uint56(542503979188225),
        uint56(696435607076865),
        uint56(697535118704641),
        uint56(698634630332417),
        uint56(699734141960193),
        uint56(700833653587969),
        uint56(701933165215745),
        uint56(703032676843521),
        uint56(704132188471297),
        uint56(705231700099073),
        uint56(706331211726849),
        uint56(707430723354625),
        uint56(708530234982401),
        uint56(543603490816001)
    ];

    constructor(address _openStoreNFTAddress) {
        openStoreNFTAddress = _openStoreNFTAddress;
    }

    // VRAgent was here!

    function checkIfDuckOwner(uint16 _duckID) external view returns (bool) {
        require(_duckID >= 1 && _duckID <= 333, "Duck ID should be in range");
        uint56 offset = ducks[_duckID - 1];
        uint256 tokenID = uint256(offset) + baseNumber;
        OpenStoreContract nft = OpenStoreContract(openStoreNFTAddress);
        return nft.balanceOf(tx.origin, tokenID) == 1;
    }
}

// File: /D/GIT/smart-contract-things/contracts/ERC721TradableRandomMint.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Enumerable.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/math/SafeMath.sol";
import "@openzeppelin/contracts/utils/Strings.sol";

import "./common/meta-transactions/ContentMixin.sol";
import "./common/meta-transactions/NativeMetaTransaction.sol";
import "./ProxyRegistry.sol";


/**
 * @title ERC721TradableRandomMint
 * ERC721TradableRandomMint - ERC721 contract that whitelists a trading address, and has minting functionality.
 * and also has random minting functionality (VRAgent/VRPunk addition)
 */
abstract contract ERC721TradableRandomMint is ContextMixin, ERC721Enumerable, NativeMetaTransaction, Ownable {
    using SafeMath for uint256;

    address proxyRegistryAddress;

    string public baseURI;

    /**
     * @dev This is the mapping we randomly pick from. In case it is 0 it means use the index number instead.
     *      when a token is picked we take the last index and move it to the front.
     */
    mapping (uint16 => uint16) tokenPickMapping;
    uint16 tokensAvailable = 10000;

    constructor(
        string memory _name,
        string memory _symbol,
        address _proxyRegistryAddress
    ) ERC721(_name, _symbol) {
        proxyRegistryAddress = _proxyRegistryAddress;
        _initializeEIP712(_name);
    }

    /**
     * @dev generates a random uint16 number based on block info
     */
    function randomUint16() internal view returns (uint16) {
        bytes32 randomHash = keccak256(
            abi.encode(
                block.timestamp,
                block.difficulty,
                block.coinbase,
                tx.origin
            )
        );
        return uint16(uint256(randomHash) % (type(uint16).max));
    }

    /**
     * @dev Mints a random token to an address with a tokenURI.
     * @param _to address of the future owner of the token
     */
    function mintTo(address _to) public onlyOwner {
        require(tokensAvailable > 0, "No more tokens available.");
        uint16 randomPick = randomUint16() % tokensAvailable;
        uint16 pickedRandomToken = tokenPickMapping[randomPick];
        if (pickedRandomToken == 0) {
            pickedRandomToken = randomPick + 1;
        }
        
        // Lets mint the randomly picked token:
        uint16 newTokenId = pickedRandomToken - 1;
        _mint(_to, newTokenId);
        
        // after successfully minting we can update the tokenPickMapping
        tokensAvailable--;

        uint16 lastToken = tokenPickMapping[tokensAvailable];
        if (lastToken == 0) {
            lastToken = tokensAvailable + 1;
        }
        tokenPickMapping[randomPick] = lastToken;
    }

    function tokenURI(uint256 _tokenId) override public view returns (string memory) {
        return string(abi.encodePacked(baseURI, Strings.toString(_tokenId)));
    }

    /**
     * Override isApprovedForAll to whitelist user's OpenSea proxy accounts to enable gas-less listings.
     */
    function isApprovedForAll(address owner, address operator)
        override
        public
        view
        returns (bool)
    {
        // Whitelist OpenSea proxy contract for easy trading.
        ProxyRegistry proxyRegistry = ProxyRegistry(proxyRegistryAddress);
        if (address(proxyRegistry.proxies(owner)) == operator) {
            return true;
        }

        return super.isApprovedForAll(owner, operator);
    }

    /**
     * This is used instead of msg.sender as transactions won't be sent by the original token owner, but by OpenSea.
     */
    function _msgSender()
        internal
        override
        view
        returns (address sender)
    {
        return ContextMixin.msgSender();
    }
}
// File: /D/GIT/smart-contract-things/contracts/IFactoryERC721.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * This is a generic factory contract that can be used to mint tokens. The configuration
 * for minting is specified by an _optionId, which can be used to delineate various
 * ways of minting.
 */
interface FactoryERC721 {
    /**
     * Returns the name of this factory.
     */
    function name() external view returns (string memory);

    /**
     * Returns the symbol for this factory.
     */
    function symbol() external view returns (string memory);

    /**
     * Number of options the factory supports.
     */
    function numOptions() external view returns (uint256);

    /**
     * @dev Returns whether the option ID can be minted. Can return false if the developer wishes to
     * restrict a total supply per option ID (or overall).
     */
    function canMint(uint256 _optionId) external view returns (bool);

    /**
     * @dev Returns a URL specifying some metadata about the option. This metadata can be of the
     * same structure as the ERC721 metadata.
     */
    function tokenURI(uint256 _optionId) external view returns (string memory);

    /**
     * Indicates that this is a factory contract. Ideally would use EIP 165 supportsInterface()
     */
    function supportsFactoryInterface() external view returns (bool);

    /**
     * @dev Mints asset(s) in accordance to a specific address with a particular "option". This should be
     * callable only by the contract owner or the owner's Wyvern Proxy (later universal login will solve this).
     * Options should also be delineated 0 - (numOptions() - 1) for convenient indexing.
     * @param _optionId the option id
     * @param _toAddress address of the future owner of the asset(s)
     */
    function mint(uint256 _optionId, address _toAddress) external;
}
// File: /D/GIT/smart-contract-things/contracts/ProxyRegistry.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

contract OwnableDelegateProxy {}

contract ProxyRegistry {
    mapping(address => OwnableDelegateProxy) public proxies;
}

// File: /D/GIT/smart-contract-things/contracts/SecretAgentAcademy.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/Strings.sol";
import "./IFactoryERC721.sol";
import "./AgentDsSecretRoom.sol";
import "./DuckOwnerProxy.sol";

contract SecretAgentAcademy is FactoryERC721, Ownable {
    using SafeMath for uint256;

    using Strings for string;

    event Transfer(
        address indexed from,
        address indexed to,
        uint256 indexed tokenId
    );

    mapping(uint16 => bool) public mintsFromDuckIDs;

    mapping(address => bool) public presaleWhitelist;

    address public proxyRegistryAddress;
    address public nftAddress;
    address public duckOwnerProxyAdress;
    string public baseURI;

    uint256 public presaleTime = 0;
    uint256 public presaleEndTime = 0;

    uint256 MAX_SUPPLY = 10000;

    uint256 NUM_OPTIONS = 3;
    uint256 SINGLE_OPTION = 0;
    uint256 MULTIPLE_OPTION_5 = 1;
    uint256 MULTIPLE_OPTION_10 = 2;

    modifier onlyPresaleWhitelisted() {
        require(
            presaleWhitelist[msg.sender],
            "You're not whitelisted for pre-sale."
        );
        _;
    }

    // left goto1 

    constructor(address _proxyRegistryAddress, address _nftAddress, address _duckOwnerProxyAdress) {
        proxyRegistryAddress = _proxyRegistryAddress;
        nftAddress = _nftAddress;
        duckOwnerProxyAdress = _duckOwnerProxyAdress;

        fireTransferEvents(address(0), owner());
    }

    function name() override external pure returns (string memory) {
        return "Secret Agent Academy";
    }

    function symbol() override external pure returns (string memory) {
        return "SAA";
    }

    function supportsFactoryInterface() override public pure returns (bool) {
        return true;
    }

    function numOptions() override public view returns (uint256) {
        return NUM_OPTIONS;
    }

    function transferOwnership(address newOwner) override public onlyOwner {
        address _prevOwner = owner();
        super.transferOwnership(newOwner);
        fireTransferEvents(_prevOwner, newOwner);
    }

    function fireTransferEvents(address _from, address _to) private {
        for (uint256 i = 0; i < NUM_OPTIONS; i++) {
            emit Transfer(_from, _to, i);
        }
    }

    function setPresaleTimes(
        uint256 _presaleTime,
        uint256 _presaleEndTime
    ) external onlyOwner {
        presaleTime = _presaleTime;
        presaleEndTime = _presaleEndTime;
    }

    function presale(uint256 _amount) external payable onlyPresaleWhitelisted {
        require(
            block.timestamp >= presaleTime && block.timestamp < presaleEndTime,
            "No presale going on at the moment."
        );
        AgentDsSecretRoom nft = AgentDsSecretRoom(nftAddress);
        address toAddress = _msgSender();
        require(
            (_amount + nft.balanceOf(toAddress)) <= 5,
            "Up to 5 NFTs can be purchased in the presale."
        );
        require(
            msg.value == uint256(_amount) * 0.045 ether,
            "You need to pay the exact price."
        );
        uint256 totalSupply = nft.totalSupply();
        require(totalSupply <= (MAX_SUPPLY - _amount), "Not enough NFTs in stock");
        for (
            uint256 i = 0;
            i < _amount;
            i++
        ) {
            nft.mintTo(toAddress);
        }
    }

    function mintFromDuck(uint16 _duckID) external {
        require(!mintsFromDuckIDs[_duckID], "Already minted from this duck");
        DuckOwnerProxy duckOwnerProxy = DuckOwnerProxy(duckOwnerProxyAdress);
        require(duckOwnerProxy.checkIfDuckOwner(_duckID), "You should own this duck in order to use it.");
        AgentDsSecretRoom nft = AgentDsSecretRoom(nftAddress);
        address toAddress = _msgSender();
        uint256 totalSupply = nft.totalSupply();
        require(totalSupply <= (MAX_SUPPLY - 1), "Not enough NFTs in stock");
        nft.mintTo(toAddress);
        mintsFromDuckIDs[_duckID] = true;
    }

    function mint(uint256 _optionId, address _toAddress) override public {
        // Must be sent from the owner proxy or owner.
        ProxyRegistry proxyRegistry = ProxyRegistry(proxyRegistryAddress);
        assert(
            address(proxyRegistry.proxies(owner())) == _msgSender() ||
                owner() == _msgSender()
        );
        require(canMint(_optionId));

        AgentDsSecretRoom nft = AgentDsSecretRoom(nftAddress);
        uint256 numberToMint = 0;
        if (_optionId == SINGLE_OPTION) {
            numberToMint = 1;
        } else if (_optionId == MULTIPLE_OPTION_5) {
            numberToMint = 5;
        } else if (_optionId == MULTIPLE_OPTION_10) {
            numberToMint = 10;
        }

        require(_toAddress == owner() || (nft.balanceOf(_toAddress) + numberToMint) <= 15, "Only up to 15 NFT per owner" );

        for (
            uint256 i = 0;
            i < numberToMint;
            i++
        ) {
            nft.mintTo(_toAddress);
        }
   } 

    function canMint(uint256 _optionId) override public view returns (bool) {
        if (_optionId >= NUM_OPTIONS) {
            return false;
        }

        AgentDsSecretRoom nft = AgentDsSecretRoom(nftAddress);
        uint256 totalSupply = nft.totalSupply();

        uint256 numItemsAllocated = 0;
        if (_optionId == SINGLE_OPTION) {
            numItemsAllocated = 1;
        } else if (_optionId == MULTIPLE_OPTION_5) {
            numItemsAllocated = 5;
        } else if (_optionId == MULTIPLE_OPTION_10) {
            numItemsAllocated = 10;
        }
        return totalSupply <= (MAX_SUPPLY - numItemsAllocated);
    }

    function tokenURI(uint256 _optionId) override external view returns (string memory) {
        return string(abi.encodePacked(baseURI, Strings.toString(_optionId)));
    }

    /**
     * Hack to get things to work automatically on OpenSea.
     * Use transferFrom so the frontend doesn't have to worry about different method names.
     */
    function transferFrom(
        address /* _from */,
        address _to,
        uint256 _tokenId
    ) public {
        mint(_tokenId, _to);
    }

    /**
     * Hack to get things to work automatically on OpenSea.
     * Use isApprovedForAll so the frontend doesn't have to worry about different method names.
     */
    function isApprovedForAll(address _owner, address _operator)
        public
        view
        returns (bool)
    {
        if (owner() == _owner && _owner == _operator) {
            return true;
        }

        ProxyRegistry proxyRegistry = ProxyRegistry(proxyRegistryAddress);
        if (
            owner() == _owner &&
            address(proxyRegistry.proxies(_owner)) == _operator
        ) {
            return true;
        }
        return false;
    }

    function withdraw() external onlyOwner {
        require(address(this).balance > 0, "You just wasted gas on trying to withdraw nada...");
        payable(owner()).transfer(address(this).balance);
    }

    /**
     * Hack to get things to work automatically on OpenSea.
     * Use isApprovedForAll so the frontend doesn't have to worry about different method names.
     */
    function ownerOf(uint256 /*_tokenId*/) public view returns (address _owner) {
        return owner();
    }

    function setBaseUri(string memory uri) public onlyOwner {
        baseURI = uri;
    }

    function addAddressesToPresaleWhitelist(address[] memory addrs) public onlyOwner {
        for (uint256 i = 0; i < addrs.length; i++) {
            presaleWhitelist[addrs[i]] = true;
        }
    }
    // We got taken!
}

// File: /D/GIT/smart-contract-things/contracts/common/meta-transactions/ContentMixin.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

abstract contract ContextMixin {
    function msgSender()
        internal
        view
        returns (address payable sender)
    {
        if (msg.sender == address(this)) {
            bytes memory array = msg.data;
            uint256 index = msg.data.length;
            assembly {
                // Load the 32 bytes word from memory with the address on the lower 20 bytes, and mask those.
                sender := and(
                    mload(add(array, index)),
                    0xffffffffffffffffffffffffffffffffffffffff
                )
            }
        } else {
            sender = payable(msg.sender);
        }
        return sender;
    }
}
// File: /D/GIT/smart-contract-things/contracts/common/meta-transactions/EIP712Base.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import {Initializable} from "./Initializable.sol";

contract EIP712Base is Initializable {
    struct EIP712Domain {
        string name;
        string version;
        address verifyingContract;
        bytes32 salt;
    }

    string constant public ERC712_VERSION = "1";

    bytes32 internal constant EIP712_DOMAIN_TYPEHASH = keccak256(
        bytes(
            "EIP712Domain(string name,string version,address verifyingContract,bytes32 salt)"
        )
    );
    bytes32 internal domainSeperator;

    // supposed to be called once while initializing.
    // one of the contracts that inherits this contract follows proxy pattern
    // so it is not possible to do this in a constructor
    function _initializeEIP712(
        string memory name
    )
        internal
        initializer
    {
        _setDomainSeperator(name);
    }

    function _setDomainSeperator(string memory name) internal {
        domainSeperator = keccak256(
            abi.encode(
                EIP712_DOMAIN_TYPEHASH,
                keccak256(bytes(name)),
                keccak256(bytes(ERC712_VERSION)),
                address(this),
                bytes32(getChainId())
            )
        );
    }

    function getDomainSeperator() public view returns (bytes32) {
        return domainSeperator;
    }

    function getChainId() public view returns (uint256) {
        uint256 id;
        assembly {
            id := chainid()
        }
        return id;
    }

    /**
     * Accept message hash and returns hash message in EIP712 compatible form
     * So that it can be used to recover signer from signature signed using EIP712 formatted data
     * https://eips.ethereum.org/EIPS/eip-712
     * "\\x19" makes the encoding deterministic
     * "\\x01" is the version byte to make it compatible to EIP-191
     */
    function toTypedMessageHash(bytes32 messageHash)
        internal
        view
        returns (bytes32)
    {
        return
            keccak256(
                abi.encodePacked("\x19\x01", getDomainSeperator(), messageHash)
            );
    }
}
// File: /D/GIT/smart-contract-things/contracts/common/meta-transactions/Initializable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

contract Initializable {
    bool inited = false;

    modifier initializer() {
        require(!inited, "already inited");
        _;
        inited = true;
    }
}
// File: /D/GIT/smart-contract-things/contracts/common/meta-transactions/NativeMetaTransaction.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import {SafeMath} from  "@openzeppelin/contracts/utils/math/SafeMath.sol";
import {EIP712Base} from "./EIP712Base.sol";

contract NativeMetaTransaction is EIP712Base {
    using SafeMath for uint256;
    bytes32 private constant META_TRANSACTION_TYPEHASH = keccak256(
        bytes(
            "MetaTransaction(uint256 nonce,address from,bytes functionSignature)"
        )
    );
    event MetaTransactionExecuted(
        address userAddress,
        address payable relayerAddress,
        bytes functionSignature
    );
    mapping(address => uint256) nonces;

    /*
     * Meta transaction structure.
     * No point of including value field here as if user is doing value transfer then he has the funds to pay for gas
     * He should call the desired function directly in that case.
     */
    struct MetaTransaction {
        uint256 nonce;
        address from;
        bytes functionSignature;
    }

    function executeMetaTransaction(
        address userAddress,
        bytes memory functionSignature,
        bytes32 sigR,
        bytes32 sigS,
        uint8 sigV
    ) public payable returns (bytes memory) {
        MetaTransaction memory metaTx = MetaTransaction({
            nonce: nonces[userAddress],
            from: userAddress,
            functionSignature: functionSignature
        });

        require(
            verify(userAddress, metaTx, sigR, sigS, sigV),
            "Signer and signature do not match"
        );

        // increase nonce for user (to avoid re-use)
        nonces[userAddress] = nonces[userAddress].add(1);

        emit MetaTransactionExecuted(
            userAddress,
            payable(msg.sender),
            functionSignature
        );

        // Append userAddress and relayer address at the end to extract it from calling context
        (bool success, bytes memory returnData) = address(this).call(
            abi.encodePacked(functionSignature, userAddress)
        );
        require(success, "Function call not successful");

        return returnData;
    }

    function hashMetaTransaction(MetaTransaction memory metaTx)
        internal
        pure
        returns (bytes32)
    {
        return
            keccak256(
                abi.encode(
                    META_TRANSACTION_TYPEHASH,
                    metaTx.nonce,
                    metaTx.from,
                    keccak256(metaTx.functionSignature)
                )
            );
    }

    function getNonce(address user) public view returns (uint256 nonce) {
        nonce = nonces[user];
    }

    function verify(
        address signer,
        MetaTransaction memory metaTx,
        bytes32 sigR,
        bytes32 sigS,
        uint8 sigV
    ) internal view returns (bool) {
        require(signer != address(0), "NativeMetaTransaction: INVALID_SIGNER");
        return
            signer ==
            ecrecover(
                toTypedMessageHash(hashMetaTransaction(metaTx)),
                sigV,
                sigR,
                sigS
            );
    }
}
// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

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

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

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

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _setOwner(_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 {
        _setOwner(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");
        _setOwner(newOwner);
    }

    function _setOwner(address newOwner) private {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

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



// SPDX-License-Identifier: MIT

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 {
        require(operator != _msgSender(), "ERC721: approve to caller");

        _operatorApprovals[_msgSender()][operator] = approved;
        emit ApprovalForAll(_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);
    }

    /**
     * @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);
    }

    /**
     * @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 of token that is not own");
        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);
    }

    /**
     * @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 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(to).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 {}
}

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



// SPDX-License-Identifier: MIT

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

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/ERC721Enumerable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../ERC721.sol";
import "./IERC721Enumerable.sol";

/**
 * @dev This implements an optional extension of {ERC721} defined in the EIP that adds
 * enumerability of all the token ids in the contract as well as all token ids owned by each
 * account.
 */
abstract contract ERC721Enumerable is ERC721, IERC721Enumerable {
    // Mapping from owner to list of owned token IDs
    mapping(address => mapping(uint256 => uint256)) private _ownedTokens;

    // Mapping from token ID to index of the owner tokens list
    mapping(uint256 => uint256) private _ownedTokensIndex;

    // Array with all token ids, used for enumeration
    uint256[] private _allTokens;

    // Mapping from token id to position in the allTokens array
    mapping(uint256 => uint256) private _allTokensIndex;

    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override(IERC165, ERC721) returns (bool) {
        return interfaceId == type(IERC721Enumerable).interfaceId || super.supportsInterface(interfaceId);
    }

    /**
     * @dev See {IERC721Enumerable-tokenOfOwnerByIndex}.
     */
    function tokenOfOwnerByIndex(address owner, uint256 index) public view virtual override returns (uint256) {
        require(index < ERC721.balanceOf(owner), "ERC721Enumerable: owner index out of bounds");
        return _ownedTokens[owner][index];
    }

    /**
     * @dev See {IERC721Enumerable-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _allTokens.length;
    }

    /**
     * @dev See {IERC721Enumerable-tokenByIndex}.
     */
    function tokenByIndex(uint256 index) public view virtual override returns (uint256) {
        require(index < ERC721Enumerable.totalSupply(), "ERC721Enumerable: global index out of bounds");
        return _allTokens[index];
    }

    /**
     * @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` cannot be the zero address.
     * - `to` cannot be the zero address.
     *
     * 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 override {
        super._beforeTokenTransfer(from, to, tokenId);

        if (from == address(0)) {
            _addTokenToAllTokensEnumeration(tokenId);
        } else if (from != to) {
            _removeTokenFromOwnerEnumeration(from, tokenId);
        }
        if (to == address(0)) {
            _removeTokenFromAllTokensEnumeration(tokenId);
        } else if (to != from) {
            _addTokenToOwnerEnumeration(to, tokenId);
        }
    }

    /**
     * @dev Private function to add a token to this extension's ownership-tracking data structures.
     * @param to address representing the new owner of the given token ID
     * @param tokenId uint256 ID of the token to be added to the tokens list of the given address
     */
    function _addTokenToOwnerEnumeration(address to, uint256 tokenId) private {
        uint256 length = ERC721.balanceOf(to);
        _ownedTokens[to][length] = tokenId;
        _ownedTokensIndex[tokenId] = length;
    }

    /**
     * @dev Private function to add a token to this extension's token tracking data structures.
     * @param tokenId uint256 ID of the token to be added to the tokens list
     */
    function _addTokenToAllTokensEnumeration(uint256 tokenId) private {
        _allTokensIndex[tokenId] = _allTokens.length;
        _allTokens.push(tokenId);
    }

    /**
     * @dev Private function to remove a token from this extension's ownership-tracking data structures. Note that
     * while the token is not assigned a new owner, the `_ownedTokensIndex` mapping is _not_ updated: this allows for
     * gas optimizations e.g. when performing a transfer operation (avoiding double writes).
     * This has O(1) time complexity, but alters the order of the _ownedTokens array.
     * @param from address representing the previous owner of the given token ID
     * @param tokenId uint256 ID of the token to be removed from the tokens list of the given address
     */
    function _removeTokenFromOwnerEnumeration(address from, uint256 tokenId) private {
        // To prevent a gap in from's tokens array, we store the last token in the index of the token to delete, and
        // then delete the last slot (swap and pop).

        uint256 lastTokenIndex = ERC721.balanceOf(from) - 1;
        uint256 tokenIndex = _ownedTokensIndex[tokenId];

        // When the token to delete is the last token, the swap operation is unnecessary
        if (tokenIndex != lastTokenIndex) {
            uint256 lastTokenId = _ownedTokens[from][lastTokenIndex];

            _ownedTokens[from][tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
            _ownedTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index
        }

        // This also deletes the contents at the last position of the array
        delete _ownedTokensIndex[tokenId];
        delete _ownedTokens[from][lastTokenIndex];
    }

    /**
     * @dev Private function to remove a token from this extension's token tracking data structures.
     * This has O(1) time complexity, but alters the order of the _allTokens array.
     * @param tokenId uint256 ID of the token to be removed from the tokens list
     */
    function _removeTokenFromAllTokensEnumeration(uint256 tokenId) private {
        // To prevent a gap in the tokens array, we store the last token in the index of the token to delete, and
        // then delete the last slot (swap and pop).

        uint256 lastTokenIndex = _allTokens.length - 1;
        uint256 tokenIndex = _allTokensIndex[tokenId];

        // When the token to delete is the last token, the swap operation is unnecessary. However, since this occurs so
        // rarely (when the last minted token is burnt) that we still do the swap here to avoid the gas cost of adding
        // an 'if' statement (like in _removeTokenFromOwnerEnumeration)
        uint256 lastTokenId = _allTokens[lastTokenIndex];

        _allTokens[tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
        _allTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index

        // This also deletes the contents at the last position of the array
        delete _allTokensIndex[tokenId];
        _allTokens.pop();
    }
}

// File: @openzeppelin/contracts/token/ERC721/extensions/IERC721Enumerable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../IERC721.sol";

/**
 * @title ERC-721 Non-Fungible Token Standard, optional enumeration extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
interface IERC721Enumerable is IERC721 {
    /**
     * @dev Returns the total amount of tokens stored by the contract.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns a token ID owned by `owner` at a given `index` of its token list.
     * Use along with {balanceOf} to enumerate all of ``owner``'s tokens.
     */
    function tokenOfOwnerByIndex(address owner, uint256 index) external view returns (uint256 tokenId);

    /**
     * @dev Returns a token ID at a given `index` of all the tokens stored by the contract.
     * Use along with {totalSupply} to enumerate all tokens.
     */
    function tokenByIndex(uint256 index) external view returns (uint256);
}

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



// SPDX-License-Identifier: MIT

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

pragma solidity ^0.8.0;

/**
 * @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
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        assembly {
            size := extcodesize(account)
        }
        return size > 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);
    }

    function _verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) private 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

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

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

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

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/utils/math/SafeMath.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

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

/**
 * @dev Wrappers over Solidity's arithmetic operations.
 *
 * NOTE: `SafeMath` is no longer needed starting with Solidity 0.8. The compiler
 * now has built in overflow checking.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            uint256 c = a + b;
            if (c < a) return (false, 0);
            return (true, c);
        }
    }

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

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

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

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

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

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

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

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

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

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

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

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