// File: contracts/EtherTulip.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import {ERC721} from "@openzeppelin/contracts/token/ERC721/ERC721.sol";

// This is a revised version of the revised version of the original EtherRock contract 0x41f28833Be34e6EDe3c58D1f597bef429861c4E2 with all the rocks removed and rock properties replaced by tulips.
// The original contract at 0x41f28833Be34e6EDe3c58D1f597bef429861c4E2 had a simple mistake in the buyRock() function where it would mint a rock and not a tulip. The line:
// require(rocks[rockNumber].currentlyForSale == true);
// Had to check for the existance of a tulip, as follows:
// require(tulips[tulipNumber].currentlyForSale == true);
// Therefore in the original contract, anyone could buy anyone elses rock whereas they should have been buying a tulip (regardless of whether the owner chose to sell it or not)

contract EtherTulip is ERC721("EtherTulip", unicode"🌷") {
    struct Tulip {
        uint256 listingTime;
        uint256 price;
        uint256 timesSold;
    }

    mapping(uint256 => Tulip) public tulips;

    uint256 public latestNewTulipForSale;

    address public immutable feeRecipient;

    event TulipForSale(uint256 tulipNumber, address owner, uint256 price);
    event TulipNotForSale(uint256 tulipNumber, address owner);
    event TulipSold(uint256 tulipNumber, address buyer, uint256 price);

    constructor(address _feeRecipient) {
        // set fee recipient
        feeRecipient = _feeRecipient;
        // mint founder tulip to yours and only
        ERC721._mint(address(0x777B0884f97Fd361c55e472530272Be61cEb87c8), 0);
        // initialize auction for second tulip
        latestNewTulipForSale = 1;
        tulips[latestNewTulipForSale].listingTime = block.timestamp;
    }

    // Dutch-ish Auction

    function currentPrice(uint256 tulipNumber) public view returns (uint256 price) {
        if (tulipNumber == latestNewTulipForSale) {
            // if currently in auction
            uint256 initialPrice = 1000 ether;
            uint256 decayPeriod = 1 days;
            // price = initial_price - initial_price * (current_time - start_time) / decay_period
            uint256 elapsedTime = block.timestamp - tulips[tulipNumber].listingTime;
            if (elapsedTime >= decayPeriod) return 0;
            return initialPrice - ((initialPrice * elapsedTime) / decayPeriod);
        } else {
            // if not in auction
            return tulips[tulipNumber].price;
        }
    }

    // ERC721

    function _baseURI() internal pure override returns (string memory) {
        return "ipfs://";
    }

    function tokenURI(uint256 tokenId) public view override returns (string memory) {
        string memory bulbURI = "bafkreiamkokggzkchkosx5jvz6fduzwcn7qugkp7pytmk327sblrtwa4ze";
        string[100] memory tulipURIs = [
            "bafkreiajlq3nd3nc7xu245eqwnoqkh4fz25rdkinw7wkjtqp54xcbxdski",
            "bafkreickj5f3dw6abk4ezj6vvephroacnizpt474jxjffccklci4bm7ulu",
            "bafkreid3ckzlcv3p6zh3o3cwbryno3keqvzyagptnxtoer3awuvyeydz4u",
            "bafkreid43dy6zwtnvwo6skonl4tcechlhnu7rihp2gnvoaydpxn3qw6yva",
            "bafkreicnjnnu6w3crbzxkoa2g625avmnecrh4ptmuvj2q5izygeqhttjny",
            "bafkreiaefcjmmploftqi6ao3dzrpjttnrhay2hqit5pxtzpwkismviwi7e",
            "bafkreid2jrk7rquxayxdfvyg3w447wqssoutoybqeihuunmau4n5ourj4i",
            "bafkreicvpenpqezcdehpcd2snsgj4ysl2la44fzqdolblr6evpps3uujcm",
            "bafkreihuxku32udn2eolrdivdugr2dd5sot2u7cvth3qpsjoqbkllbwkgy",
            "bafkreidumlyzcwbuaajaeeycq6e6y2zcr4jwq2amy35nsh7laphiecbyvi",
            "bafkreigjkkhwb3rtdgvbhjc6aoarrlqmyfe7f4d67fvtxprqns3r5zu6jm",
            "bafkreigmgqiafi4obtmtzzsocylrfcctjtemm3tdvecr3lobo6sqz73o3u",
            "bafkreig5b6rx3mdxwyrtnumyehvuetzrs3dwkxv76wtqhfayammh2hlsve",
            "bafkreicvhumzmjl7bo4uqhngwxfpk6upry4waxm3csk7wgkkyzjejgcwai",
            "bafkreiehn3tovb6wa2nt6nsouavmy6vrijc4z775hk4hjzdn7b5y5lkiya",
            "bafkreid6lxzktumy535tvzedks3acaqzrqirim4migkbxrp5erx5g6mfeu",
            "bafkreihk3mimxxqimwkowm2arpfaewz7m5o76wcvw4acyixhtun673az34",
            "bafkreidrrmeujlvad7oigztu45yeqxwcb6wpo464vwxqst4qo3itwk6ld4",
            "bafkreihl6hl2ufborow5cfiypdtkk2segp3vxfetupapsjnjvzwxlq2che",
            "bafkreidnv2t75e3kx6ugajs23l4736assxkzrggsocz2dvygsjlvhvntza",
            "bafkreih2hhoeruntbfy4ufngko3wbdp4m6gz7otu3hntuvntlflyehkejq",
            "bafkreieiqmc2t62t2pgabenfkeiclb4gsifcwgqvmkcwqc7lkaxm4vqvai",
            "bafkreieqi56ie7iyl4rne2r7ypnvrbcpvxxqp346c74smgd3vypgspdwdi",
            "bafkreidfw4bmdl3rcoehnak43beoeoucbbvtkxlagisvnuchug4foprhpq",
            "bafkreiasg674cri4woi2nmf2be27i24gdegxhc5hgahpygd7vqcrqvz4va",
            "bafkreidn3ocz3m6lzgu7whiooq74mtczbget5fie7dldzwhafdkty5yje4",
            "bafkreieg474qoeg5mykld7dpego4oy4tvjorlgtpjacw3cjrl7oogsfs6a",
            "bafkreiclbj3ujgxgh5i3plai5t24p7g2aavfzahu2gxq4mavena5ojxfsm",
            "bafkreia2vekumcnyswh2w62htqu7vedtksepokixpqn4qwzxhefj2bdniq",
            "bafkreia5456ribmisd555cwt6vzu57oqqkonugozywjuozsoxlo7ffoqxi",
            "bafkreiekctvro262pk4uz67jpqivxtniebqk3gyfqkclw2vqy3m3iocw6e",
            "bafkreigtxjoh4rx62uzlx4t23txqk3owvn3ckhy766mjiwgvy3fny2ozza",
            "bafkreifui4jzaffl74zakibwmt2js2w2qosm7yzgimecwvqpqxpz2psnmu",
            "bafkreif7426cefprxiupxwggnkjbtht3f3uiaeci2qc3irlppuy7kqoenq",
            "bafkreigdimqwjrkoklbfiigbkfpvmrniealdjr2bv52jb72sfbk6aqorqy",
            "bafkreidy2eohxrecrk3si4coolxawlcdmqrvhskhkal4d6bvxjfmds2m24",
            "bafkreie3qfepdl4pkse6uu3iqwfb2fqusfp3qsp2rh7ynvptps3bbnqzdm",
            "bafkreih2hv3vjipj2kibpynrmulnnoxj5737cbeg2bjl42zc3bhcfdzf2u",
            "bafkreiba3227uclzobdglmkvyz4b5da6gp3p3ehtfqznuprlgu3lt7j6nq",
            "bafkreiakbrgj7y2hzb7dhrpub6c6i72i3cp6ygsrof55t5ueb7wtg33bae",
            "bafkreig5x3r3dqllt2ndhxpahni5fjeeo2obq4ffls4hkbi7a2cfqtappi",
            "bafkreihfiplwjo4rdszuhnvjynx7iesij3borjd3rf5onlfgkwlqqjpbou",
            "bafkreicpnd4dysoaov3ra3jxsnoanyfyg3d56ntuzljro77a2bpgbzo6nu",
            "bafkreicdlambpulyaytsiffl2yra55ejhdcchpzlx3trutkoc4tinkiomq",
            "bafkreia57yvsl5esloc7fsn7uiw5q6opkk477f7qgh2sd2mibl66dwgz4m",
            "bafkreigpxggeedsw2y7rd5dqzhhf4qxq3hw3y5qqnmzgmbg5225z32ke6e",
            "bafkreihnezodqrdgshpkx5mkkebiz472y6r3xjnhjtrea75td6jxobf7ha",
            "bafkreiabrwr6bj62rwayp2nvaa7welt24h3rfrsiilj6f6qav4ryjceb4q",
            "bafkreiddvsn24iswrmxt3ceo7pngsvm44qzzknqto2hz4meytsbqw2q2yy",
            "bafkreibu53ggwhoojqkqws3l6nampmzxyczkymw5ozfz6q4t7tpwimha4y",
            "bafkreigwpa25qyx7f23v7t2nbdzywfigwp324dez2kvfrwyibeckl7kmry",
            "bafkreidjlqycv7hkvn6zmsnwbjy7l563pya2fwtnj5mmiqzosjzyuvv7ay",
            "bafkreibphjjkaarzd6kknwwmjtooccup7p3wyuvahmaemcyfjnbdbjci24",
            "bafkreie3unp25d6yx7yvi7bohox2mftpq5rirhl444ylep5ivijovybs5u",
            "bafkreifwh5ih76ed44cy545vyjovzre2esgk7a6m2njeb2qo5ofzus6q34",
            "bafkreie3h3ltvvnokylzyzcpultd7a5ba5ldp4ui4ejlhr7lbucklj4zfu",
            "bafkreiho2ufocna6dgavys6w3hzjudcppni7fnmo5pdes3cn3m7ndiu3b4",
            "bafkreigdwveaxxfl4sfdnyedx4nnnfv7fzspjmmr3j4eozjfv7tjsovwma",
            "bafkreidfixu2x5svom4aivbzbwyszrt7etpy7vm4deiepxgfyzshzn2ypi",
            "bafkreialq7tz66rwqift3hwfhs7mkpjraqp24lk4kk2amlnh535zzkizzy",
            "bafkreieay36cd2bsrn2tipb4zijvkylnfj7dinsaz342gnope7wsrrypjq",
            "bafkreieo6nbwxyahaafswfbe4sahqby3h7ru2hfitzru6iqyxqgch7nrzq",
            "bafkreicsv6fe4ykonns6hxctcjht7bqx5646cbpgbsug4xr6zg5rbthdj4",
            "bafkreihsgdzvuirts3jt3g26lto73qqu4bg7n4qu72dgmkujjkenee7e7a",
            "bafkreigkjwzzhv4cndw3ehsmsbmixzrxxvrpqj2e2yemxnnlwkew5f6gs4",
            "bafkreic5k7u2m4g3yufqpin7ofnb7hgl5vdtmto36l33bw6sjw5hktmo5a",
            "bafkreihxcdefq5k4vomblxkuj75d3b3ixasxvhuobag4whkrwyahfyfidq",
            "bafkreicjwz7p6dpvcqs7ordhzwslabcwuj3y3hehk4pl63jktebjmncjfy",
            "bafkreiakfuy3pabipys3ese6uerduczphy5rdkccguhyhsgyprmn7qz3ke",
            "bafkreialjw6gr3smsmhmrvcdvlsxxvgroyubz7fk2wrvpcrmomx7pdnjoe",
            "bafkreieqchumy7zibxq4mqppdqcdvfawq6ot7dxpbz3v5fue2bwyp5ivsm",
            "bafkreicev7nx7s75yqv2jpttw4rrukztwtr4kubxrs3wv3v4qlkz4nq4uy",
            "bafkreid2itljfobnxpvjfxnsas2fqbly5dyn7tkogvcojjxmb7muqiejta",
            "bafkreibmiuznmb5lk7gsg6376b4z6orbn2b535u6wnimiq5hwe5scref6u",
            "bafkreigxvddcurbaxgubrenqeahen47dktm4om535kaedeqenx7p6zodty",
            "bafkreibtwpwhksgskwqshwuqehwfm772pu7rfxjcxpijpu5ikh2cwvczvq",
            "bafkreic6j5qpgw326wdt6wyaf6efmbzzcw4rl5zfjiken3uxhu4s65hc2e",
            "bafkreibzl22el47bco2hi6wj6zovosteowcdkzifegbg3xncdhd3d3pjnu",
            "bafkreiew3gjv2dgldfzw5kfsginkvqz5rzktd5d4n6a2fnmuqjjk7hhcim",
            "bafkreigbjzymbt3fmlmfta5oror25swedugp2drdvsjb3juahn6e33r6l4",
            "bafkreicpzyumn7fo7negxdwb3anljwf2lqyseqeh7yogcoiyi75kfbtqky",
            "bafkreihsznkosxzsgfkutuuzhh442k7esjduylhda5ausfbautruuazzmm",
            "bafkreidbg24dnbt5to5vl6m5ektfwstwhp2djhsllf5mtciizlgg4lse6y",
            "bafkreidefsxxb5i4nvdblya2mh7h4uo47dwuthb5jqmartgg4svwrvx2xe",
            "bafkreic3qsb5mn22xy46gkg3whiqhvb2lqjmucbquiq27fyf76b7gpf3kq",
            "bafkreiaej6mkm6jjixeqtheomqtbpc4xp3yrtp66vnmcywxler5qlgidw4",
            "bafkreidhgkhkuwp5qqxzdmga7uh52qzeveu53zt4a2ahoauur6gaorf3sq",
            "bafkreibbw4oyakigmurscj3aknyq4tq4b43jjk2wsoszo4672shsog4ssu",
            "bafkreibbhcuhxye2ga3yblf4vmxsq4n3aofxckbyl66axugczb3e6dansu",
            "bafkreibxvv6oipwxyaejwvf4vnftsd6n3bf6ixnvubyus4q5nqud4plcve",
            "bafkreiahwdvpwtzcn2t45rswol5gka42yd2zkn37tn4mscq7mesuwngqyq",
            "bafkreig3mw4xebzxvrj7w5yvkg6o5a55tf2nlenbpruf7oyo3gauqjhtim",
            "bafkreihkaovv3fj2usy3kkzp4hspkisaqymki56pljvqm7yrv2ijta3pbq",
            "bafkreicytcw572hqzksn3zrdut22xo7wjxkf4ovjijokhpkx6vnc3nax7i",
            "bafkreidsfwztyha6q7i5temqm44mlhslcxerjhasj2kdfqhkssl5yfrgnu",
            "bafkreibsvhu3jxeyohswwic7u3xtzwwzbgssqrmmwzyj2fwhnykwpuu7eu",
            "bafkreibexexusac5lrtzmk26f4gc7pg2hzdf4upmd7ks37rteazol76ccy",
            "bafkreiguleybtirhrwdfp3bmmkm7xwq63so3waxgbwyh277uh62dbh55n4",
            "bafkreig7bdme4w26it2vhpdu2ahxbtl2svul5i3h5xhlpbdrxnmrnomqze",
            "bafkreicjehn5krr3lcnyl65eyh3njrfw5atepdzfmjaga44fmangdv5t6q"
        ];
        require(tokenId < 100, "Enter a tokenId from 0 to 99. Only 100 tulips.");
        if (tokenId >= latestNewTulipForSale) {
            return string(abi.encodePacked(_baseURI(), bulbURI));
        } else {
            return string(abi.encodePacked(_baseURI(), tulipURIs[tokenId]));
        }
    }

    function _beforeTokenTransfer(
        address,
        address,
        uint256 tokenId
    ) internal override {
        // unlist tulip
        tulips[tokenId].listingTime = 0;
        // emit event
        emit TulipNotForSale(tokenId, msg.sender);
    }

    // ETHERROCK

    function getTulipInfo(uint256 tulipNumber)
        public
        view
        returns (
            address owner,
            uint256 listingTime,
            uint256 price,
            uint256 timesSold
        )
    {
        return (
            ERC721.ownerOf(tulipNumber),
            tulips[tulipNumber].listingTime,
            currentPrice(tulipNumber),
            tulips[tulipNumber].timesSold
        );
    }

    function buyTulip(uint256 tulipNumber) public payable {
        // check sellable
        require(tulips[tulipNumber].listingTime != 0);
        require(tulipNumber < 100, "Enter a tokenId from 0 to 99. Only 100 tulips.");
        // check for sufficient payment
        require(msg.value >= currentPrice(tulipNumber));
        // unlist and update metadata
        tulips[tulipNumber].listingTime = 0;
        tulips[tulipNumber].timesSold++;
        // swap ownership for payment
        if (tulipNumber >= latestNewTulipForSale) {
            // if new, _mint()
            uint256 _latestNewTulipForSale = latestNewTulipForSale;
            // update auction
            if (latestNewTulipForSale < 99) {
                latestNewTulipForSale++;
                tulips[latestNewTulipForSale].listingTime = block.timestamp;
            } else {
                latestNewTulipForSale++;
            }
            // mint and transfer payment
            ERC721._mint(msg.sender, _latestNewTulipForSale);
            payable(feeRecipient).transfer(msg.value);
        } else {
            // if old, _transfer()
            address seller = ERC721.ownerOf(tulipNumber);
            ERC721._transfer(seller, msg.sender, tulipNumber);
            payable(seller).transfer(msg.value);
        }
        // emit event
        emit TulipSold(tulipNumber, msg.sender, msg.value);
    }

    function sellTulip(uint256 tulipNumber, uint256 price) public {
        require(msg.sender == ERC721.ownerOf(tulipNumber));
        require(price > 0);
        tulips[tulipNumber].price = price;
        tulips[tulipNumber].listingTime = block.timestamp;
        // emit event
        emit TulipForSale(tulipNumber, msg.sender, price);
    }

    function dontSellTulip(uint256 tulipNumber) public {
        require(msg.sender == ERC721.ownerOf(tulipNumber));
        tulips[tulipNumber].listingTime = 0;
        // emit event
        emit TulipNotForSale(tulipNumber, msg.sender);
    }

    function giftTulip(uint256 tulipNumber, address receiver) public {
        ERC721.transferFrom(msg.sender, receiver, tulipNumber);
    }
}

// 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.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/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);
    }

    /**
     * @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

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);
}