// File: /contracts/NekoCoreReserve.sol



// SPDX-License-Identifier: MIT
// NEKOCORE Reserve Minter
//
//                       @@@@@@@@@                                               (@@@@@*
//                      @@@/,,,,,%@@@@*                                      %@@@@&*/@@@@
//                     &@@*,,,,,,,,,,&@@@@                               (@@@@(,,,,,,,*@@@
//                     @@@,,,,,,,,,,,,,,*@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@,,,,,,,,,,,,%@@*
//                    @@@,,,,,,,,,,,,,,,,,,,*(/****,,,******,,,**/#@@@@(,,,,,,,,,,,,,,,,@@@
//                    @@@,,,,,,,,,,,,,,,,,,,******,,,******,,,******,,,,,,,,,,,,,,,,,,,,&@@,
//                   #@@(,,,,,,,,,,,,,,,,,,,******,,,******,,,,******,,,,,,,,,,,,,,,,,,,,@@@
//                   @@@*,,,,,,,,,,,,,,,,,,,,******,,,******,,,,******,,,,,,,,,,,,,,,,,,,@@@
//                   @@@,,,,,,,,,,,,,,,,,,,,,******,,,,******,,,,******,,,,,,,,,,,,,,,,,,#@@#
//                   @@@,,,,,,,,,,,,,,,,,,,,,*****,,,,,******,,,******,,,,,,,,,,,,,,,,,,,,@@@
//                  @@@@,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,******,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,@@@
//                &@@@,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,@@@@
//               @@@@,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,%@@@
//              @@@#,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,/@@@
//             @@@&,,,,,,,,,,,,,,,,,,,,,%&&&&&#*,,,,,,,,,,,,,,,,,,,*#&&&&&%,,,,,,,,,,,,,,,,,,%@@@
//            ,@@@,,*********,,,,,,,,@&,,/@@@/,,@@&&*,,,,,,,,,*&@@,,*&@@(,,#@*,,,,,,*******,,,@@@,
//            @@@%************,,,,&%,@#,,,,,,,*%@@,&@,,,,,,,,/@,@@&%*,,,,,,/@*/@,,************@@@@
//            @@@/****,,,,,**,,,,@,@*,,,,,,,,,,,,,/@,@,,,,,,@*%%,,,,,,,,,,,,,,@,@,,***,,,,****&@@@
//            @@@/,,,,,,,,,,,,,,@,&*,,,,,,,,,,,,,,,/%,*,(#,,,/%,,,,,,,,,,,,,,,,@,@,,,,,,,,,,,,@@@%
//            %@@@*********,,,,,@,@,,,,,@,,,,,&#,,,,@*@@&#%@*#&,,,,@,,,,,(@,,,,@,@,,,*********@@@
//             @@@/*********,,,,,@,@,,,,,,(&%*,,,@@@,@,(@@@@@,@#@@,,,(&%*,,,,,@,&*,,,********@@@%
//              @@@*,,,,,,,,,,,,,,@,&@,,,,,,,,/@@@#,@((((((((@**@ %@&,,,,,,,%@,@,,,,,,,,,,,,@@@@
//               @@@(,,,,,,,,,,,,,,,@%,/@@@@@@@*,&@(((((%&%((((@@,*@@@@@@@(,(@,,,,,,,,,,,,,@@@%
//                @@@@,,,,,,,,,,,,,,*@@@&@@@@@%%&@((((@,    @((((@&%@@@@@%&@@@*,,,,,,,,,,@@@@
//                  @@@@*,,,,,,,,,#@#(@@*,,&@((@%%%@((@,@(@ @((@%%%@((@&,,*@@(#@(,,,,,,@@@@/
//                    @@@@@,,,,,,(@(&/ %@@@*  %%(&%%@(@,@(@ @(@%%&(%%  /@@@# /&(@(,,&@@@@
//                       @@@@@%,,@@(@ @(((((@, %(&%%@(@,@(@ @(@%%%#% ,@(((((@ @(@@@@@@(
//                          (@@@@@@(@,@(((((@, &(%%%@(@,@(@ @(@%%%#& ,@(((((@,@(@@@
//                              @@@@#(@,,(/,  @#(@@@(/@@   %@((@@@(#@  ,/(,,@(#@/
//                             &@@@,%@@(((##((#@@@,,,,,,,,,,,,,,,@@@#((##(((@@%
//                            @@@&******(@@@@*,,,,,,,,,,,,,,,,,,,,,,,*@@@@@@@(
//                           @@@@,****,,,,**,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,@@@
//                          ,@@@,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,@@@
//                          @@@/***********,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,@@@*
//                         ,@@@,******,,**,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,@@@/
//                         @@@&,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,@@@/
//                      @@@@@*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,@@@
//                    @@@@,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,@@@
//                   @@@%,,,,***,,,,,/((((((((/,,,,,,,,,,,,,,,,,,,,,*(((#@@@@,
//                   @@@,,,****,,,,@@@@@@@@@@@@@@,,,,,,,@@@,,,,,,,@@@@@@@@@#
//                   @@@******,,,*****&@@@@&  @@@&,,,,,@@@@@,,,,,@@@@
//                    @@@@**,,,,****,,,,,@@@(  (@@@@@@@@@&@@@@@@@@@
//                      @@@@@@@#***,,,,,#@@@
//                          ,&@@@@@@@@@@@@#
//
//

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721Receiver.sol";
import "./NekoCore.sol";

contract NekoCoreReserve is IERC721Receiver, Ownable {
    enum ClaimStrategy {
        MATCH_BOGO,
        ONLY_ONCE,
        SET_EXPLICITLY
    }
    NekoCore public ORIGINAL_CONTRACT =
        NekoCore(0xc1328cf1CF8dB8a5fC407CD56759007C7d20e398);
    uint256 public ORIGINAL_PRICE = 0.09 ether;
    uint256 public PRICE = 0.045 ether;
    mapping(uint256 => uint256) public TIMES_CLAIMED;

    uint256 public BUY_ONE_GET_X = 1; // used for buy-one-get-X
    ClaimStrategy public CLAIM_STRATEGY_FOR_PAID_MINTS =
        ClaimStrategy.MATCH_BOGO;
    ClaimStrategy public CLAIM_STRATEGY_FOR_FREE_MINTS =
        ClaimStrategy.MATCH_BOGO;
    uint256 public EXPLICITLY_SET_CLAIMS_FOR_PAID_MINTS = 1;
    uint256 public EXPLICITLY_SET_CLAIMS_FOR_FREE_MINTS = 1;
    // ^^^ these are a little strange and we don't plan on using them, but it allows
    // for better flexibility with the giveaway limits of new mints
    uint256 public constant BATCH_CLAIM_SIZE = 1 << 6;
    bool public MINTABLE = false;

    // modifiers
    // ---------------------------------------------------------
    modifier refuelIfNeeded(uint256 count) {
        if (address(this).balance < (ORIGINAL_PRICE * count)) {
            _refuel();
        }
        _;
    }

    modifier onlyIfMintable() {
        require(MINTABLE, "NekoCore Reserve is not currently mintable");
        _;
    }

    // required overrides
    // ---------------------------------------------------------
    function onERC721Received(
        address,
        address,
        uint256,
        bytes memory
    ) public virtual override returns (bytes4) {
        return this.onERC721Received.selector;
    }

    // public functions
    // ---------------------------------------------------------
    function mint(uint256 count)
        external
        payable
        onlyIfMintable
        refuelIfNeeded(count)
    {
        require(msg.value >= PRICE * count, "Minting fee not met");

        // mint some new tokens
        uint256 token_id_start = ORIGINAL_CONTRACT.MINTED();
        ORIGINAL_CONTRACT.mint{value: ORIGINAL_PRICE * count}(count);

        // transfer all the tokens that were just minted
        for (uint256 i = 1; i <= count; i++) {
            uint256 token_id = token_id_start + i;
            // any token minted through this contract has its claim count
            // set by the current claim strategy
            if (CLAIM_STRATEGY_FOR_PAID_MINTS == ClaimStrategy.MATCH_BOGO) {
                TIMES_CLAIMED[token_id] = BUY_ONE_GET_X;
            } else if (
                CLAIM_STRATEGY_FOR_PAID_MINTS == ClaimStrategy.ONLY_ONCE
            ) {
                TIMES_CLAIMED[token_id] = type(uint256).max;
            } else {
                TIMES_CLAIMED[token_id] = EXPLICITLY_SET_CLAIMS_FOR_PAID_MINTS;
            }
            ORIGINAL_CONTRACT.safeTransferFrom(
                address(this),
                msg.sender,
                token_id
            );
        }
    }

    function claim(uint256 token_id) public onlyIfMintable refuelIfNeeded(1) {
        require(claimable(token_id), "Token is not eligible for claims");
        require(
            _msgSender() == ORIGINAL_CONTRACT.ownerOf(token_id),
            "Caller is not the token owner"
        );

        ORIGINAL_CONTRACT.mint{value: ORIGINAL_PRICE}(1);
        uint256 newTokenID = ORIGINAL_CONTRACT.MINTED();

        TIMES_CLAIMED[token_id] += 1; // increment the claim count on the original token
        if (CLAIM_STRATEGY_FOR_FREE_MINTS == ClaimStrategy.MATCH_BOGO) {
            TIMES_CLAIMED[newTokenID] = BUY_ONE_GET_X;
        } else if (CLAIM_STRATEGY_FOR_FREE_MINTS == ClaimStrategy.ONLY_ONCE) {
            TIMES_CLAIMED[newTokenID] = type(uint256).max;
        } else {
            TIMES_CLAIMED[newTokenID] = EXPLICITLY_SET_CLAIMS_FOR_FREE_MINTS;
        }

        ORIGINAL_CONTRACT.safeTransferFrom(
            address(this),
            msg.sender,
            newTokenID
        );
    }

    function claimAll(uint256[] calldata claims)
        public
        onlyIfMintable
        refuelIfNeeded(claims.length)
    {
        for (uint256 i = 0; i < claims.length; i++) {
            claim(claims[i]);
        }
    }

    // public views
    // ---------------------------------------------------------
    function claimable(uint256 token_id) public view returns (bool) {
        // token must exist, not be a trophy, and must not have been claimed already
        return
            token_id <= ORIGINAL_CONTRACT.MINTED() &&
            token_id > ORIGINAL_CONTRACT.TROPHY_COUNT() &&
            TIMES_CLAIMED[token_id] < BUY_ONE_GET_X;
    }

    function claimsAvailable(address test)
        public
        view
        returns (uint256[BATCH_CLAIM_SIZE] memory)
    {
        uint256[BATCH_CLAIM_SIZE] memory result;
        uint256 next;
        for (uint256 i = 1; i <= ORIGINAL_CONTRACT.MINTED(); i++) {
            if (claimable(i) && test == ORIGINAL_CONTRACT.ownerOf(i)) {
                for (
                    uint256 j = 0;
                    j < (BUY_ONE_GET_X - TIMES_CLAIMED[i]);
                    j++
                ) {
                    // it's possible for a token to have multiple claims on it
                    // if so, we add the id multiple times
                    result[next++] = i;
                    if (next == BATCH_CLAIM_SIZE) {
                        return result;
                    }
                }
            }
        }
        return result;
    }

    // onlyOwner
    // ---------------------------------------------------------
    function setMintable(bool mintable) external onlyOwner {
        MINTABLE = mintable;
    }

    function setMintPrice(uint256 amtWei) external onlyOwner {
        // this amount is in wei, super important
        PRICE = amtWei;
    }

    function setRedemptionAmount(uint256 amt) external onlyOwner {
        // set to 0 to turn off freebies
        BUY_ONE_GET_X = amt;
    }

    function setTokenClaimCountManually(uint token_id, uint256 claims) external onlyOwner {
        TIMES_CLAIMED[token_id] = claims;
    }

    function setClaimStrategyAndLimits(
        ClaimStrategy free,
        uint256 freeExplicitlySet,
        ClaimStrategy paid,
        uint256 paidExplicitlySet
    ) external onlyOwner {
        CLAIM_STRATEGY_FOR_FREE_MINTS = free;
        EXPLICITLY_SET_CLAIMS_FOR_FREE_MINTS = freeExplicitlySet;

        CLAIM_STRATEGY_FOR_PAID_MINTS = paid;
        EXPLICITLY_SET_CLAIMS_FOR_PAID_MINTS = paidExplicitlySet;
    }

    function setTargetContract(address nkc) external onlyOwner {
        ORIGINAL_CONTRACT = NekoCore(nkc);
        ORIGINAL_PRICE = ORIGINAL_CONTRACT.PRICE_PER_TOKEN();
    }

    function airdrop(uint256 count, address to)
        external
        onlyOwner
        refuelIfNeeded(count)
    {
        uint256 token_id_start = ORIGINAL_CONTRACT.MINTED();
        ORIGINAL_CONTRACT.mint{value: ORIGINAL_PRICE * count}(count);
        for (uint256 i = 1; i <= count; i++) {
            uint256 token_id = token_id_start + i;
            if (CLAIM_STRATEGY_FOR_PAID_MINTS == ClaimStrategy.MATCH_BOGO) {
                TIMES_CLAIMED[token_id] = BUY_ONE_GET_X;
            } else if (
                CLAIM_STRATEGY_FOR_PAID_MINTS == ClaimStrategy.ONLY_ONCE
            ) {
                TIMES_CLAIMED[token_id] = type(uint256).max;
            } else {
                TIMES_CLAIMED[token_id] = EXPLICITLY_SET_CLAIMS_FOR_PAID_MINTS;
            }
            ORIGINAL_CONTRACT.safeTransferFrom(address(this), to, token_id);
        }
    }

    function reclaimOwnership() external onlyOwner {
        // to avoid out-of-fuel errors, we allow this contract to temporarily be
        // the owner of the target contract.
        //
        // This function allows the owner of THIS contract to reclaim
        // ownership of the ORIGINAL contract
        ORIGINAL_CONTRACT.transferOwnership(_msgSender());
    }

    function withdraw(uint256 amtWei) external onlyOwner {
        // special case for '0' withdraw, transfer full balance
        if (amtWei == 0) {
            amtWei = address(this).balance;
        }
        payable(_msgSender()).transfer(amtWei);
    }

    // internal
    // ---------------------------------------------------------
    function _refuel() internal {
        ORIGINAL_CONTRACT.withdraw();
    }

    // fallbacks (ability to fund this contract)
    // ---------------------------------------------------------
    receive() external payable {}
}

// File: /contracts/NekoCore.sol



// SPDX-License-Identifier: MIT
//
//
//                       @@@@@@@@@                                               %@@@@@#                           
//                      @@@/.....%@@@@#                                      &@@@@%**@@@@                          
//                     @@@*..........&@@@@                               %@@@@/.......,@@@                         
//                     @@@..............*@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@............%@@#                        
//                    @@@...................* ////*...//////...///#@@@@ ................@@@                        
//                    @@@...................,/////*...//////...//////,..................&@@#                       
//                   %@@/...................,/////*...//////...//////,...................@@@                       
//                   @@@,...................,/////*...//////...//////....................@@@                       
//                   @@@,.....................*/*.....//////....////*....................#@@&                      
//                   @@@,............................./////,.............................,@@@                      
//                  @@@@..................................................................@@@                      
//           @@@@#@@@@....................................................................@@@@   &@@@@@@           
//           #@@****@@@@@%............................................................../@@@@@ ,,**/@@             
//              @@@******,,, @@@@&*............................................,%@@@@&*,,,,,*****@@#               
//             @@@& @@**********,,,,*%@@@@/............................,%@@@@#,,,,,,,*********@@@                  
//            #@@@//// @@****************,,,,*@@@@%............,@@@@&*,,,,,,***************@@#@@@                  
//            @@@%.......*@&/************************* @@@@@/***************************&@ ...@@@@                 
//            @@@,..........*@%//////********************************************////#@ ......%@@@                 
//            @@@#////////////,*@#/////////////////////////*////////////////////// @#/////////@@@&                 
//            &@@@////////////....*@ ///////////////////&@@ ////////////////////@ .///////////@@@                  
//             @@@,................../@ ///////// &@&........./@@#///////////@&..............@@@&                  
//              @@@////////............. @  @@&.....................,@@&  @@..........//////@@@@                   
//               @@@#////////....................@/*..,..,...../ @..................///////@@@&                    
//                @@@@/////*......................*@**********/@,....................*///@@@@                      
//                  @@@@,............................*@@@%@@@,.........................@@@@%                       
//                    @@@@@.........................................................%@@@@                          
//                       @@@@@%.................................................*@@@@@%                            
//                          %@@@@@@%.......................................*@@@@@@@                                
//                              @@@@ ....................................@@@@@                                     
//                             @@@@*/*,...................................@@@                                      
//                            @@@@//////,.................................@@@%                                     
//                           @@@@//////,...................................@@@                                     
//                          #@@@...........................................@@@                                     
//                          @@@////*.......................................@@@#                                    
//                          @@@/////*......................................@@@%                                    
//                         @@@@///*........................................@@@#                                    
//                      @@@@@*.............................................@@@                                     
//                    @@@@.................................................@@@                                     
//                   @@@#............*        /,....................*    @@@@                                      
//                   @@@...........&@@@@@@@@@@@@@.......@@@.......@@@@@@@@@&                                       
//                   @@@,............,&@@@@@  @@@&.....@@@@@,....@@@@                                              
//                    @@@@...............@@@%  %@@@@@@@@@@@@@@@@@@@                                                
//                      @@@@@@@ ........#@@@                                                                       
//                          #@@@@@@@@@@@@@&                                                                        
//
//

pragma solidity ^0.8.0;
import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/cryptography/MerkleProof.sol";

contract NekoCore is ERC721, Ownable {
    uint256 public constant PRICE_PER_TOKEN = 0.09 ether;
    uint256 public constant PRICE_PER_TOKEN_PRESALE = 0.06 ether;
    uint256 public constant SUPPLY_MAX = 9999;
    uint256 public constant LIMIT_PUBLIC_MINT = 20;
    uint256 public constant LIMIT_PRESALE_MINT = 2;
    uint256 public constant TROPHY_COUNT = 72;
    bytes32 public immutable PROVENANCE; // keccak256 of all metadata in order, 1..9999

    bytes32 public WHITELIST_ROOT; // merkle root
    uint256 public MINTED; // default = 0;
    bool public MINTABLE; // default = false;
    bool public MINTABLE_PRESALE; // default = false;

    mapping(address => uint) private _presale_balance;
    string private _baseTokenURI; // default = "";

    constructor(
        address catKing,
        string memory baseTokenURI,
        bytes32 provenance
        ) ERC721("NekoCore", "NEKOCORE") {
        _baseTokenURI = baseTokenURI;
        PROVENANCE = provenance;
        uint256 _tc = TROPHY_COUNT;
        // mint trophies to be held by the Cat King Tetsurō
        // (to be distributed to tournament winners)
        for(uint256 i = 1; i <= _tc; i++) {
            _mint(catKing, i);
        }
        MINTED = _tc;
    }

    // --- overrides --------------------------------------------------
    // ----------------------------------------------------------------

    function _baseURI() internal view override returns (string memory) {
        return _baseTokenURI;
    }

    // --- only owner -------------------------------------------------
    // ----------------------------------------------------------------

    function mintReservedTokens(address[] calldata addresses, uint256[] calldata counts) public onlyOwner {
        uint256 _current = MINTED;
        uint256 _tc = TROPHY_COUNT;

        require(addresses.length == counts.length, "Parallel arrays must be of equal length");
        require(_current == _tc, "Dev tokens may only be minted if no other tokens have been minted");

        uint256 _preminted = 0;
        for(uint256 i = 0; i < addresses.length; i++) {
            for(uint256 j = 1; j <= counts[i]; j++) {
                _mint(addresses[i], _tc + _preminted + j);
            }
            _preminted += counts[i];
        }

        MINTED += _preminted;
    }

    function setTokenURI(string calldata uri) public onlyOwner {
        // ipfs://<CID>/token_id
        _baseTokenURI = uri;
    }

    function setMintable(bool allow) public onlyOwner {
        MINTABLE = allow;
    }

    function setMintablePresale(bool allow) public onlyOwner {
        MINTABLE_PRESALE = allow;
    }

    function setWhitelistRoot(bytes32 root) public onlyOwner {
        WHITELIST_ROOT = root;
    }

    function withdraw() public onlyOwner {
        uint256 balance = address(this).balance;
        payable(_msgSender()).transfer(balance);
    }

    // --- public use -------------------------------------------------
    // ----------------------------------------------------------------

    function totalSupply() external view returns (uint256) {
        return MINTED;
    }

    function premintCount(address test) external view returns (uint256) {
        return _presale_balance[test];
    }

    function mint(uint256 count) external payable {
        uint256 _current = MINTED;

        require(MINTABLE, "Contract is not currently mintable");
        require(count <= LIMIT_PUBLIC_MINT, "Exceeded maximum mint count");
        require((_current + count) <= SUPPLY_MAX, "Attempting to mint more tokens than are available");
        require(msg.value >= PRICE_PER_TOKEN * count, "Minting fee not met");

        for(uint256 i = 1; i <= count; i++) {
            _mint(_msgSender(), _current + i);
        }

        // update supply count
        MINTED = _current + count;
    }

    function mintPresale(uint256 count, bytes32[] calldata proof) external payable {
        uint256 _current = MINTED;
        
        require(!MINTABLE, "Contract is live, no longer in presale");
        require(MINTABLE_PRESALE, "Contract is not currently in presale");
        require(MerkleProof.verify(proof, WHITELIST_ROOT, keccak256(abi.encodePacked(_msgSender()))), "Caller did not provide valid whitelist proof");
        require(count <= LIMIT_PRESALE_MINT, "Exceeded maximum mint count for presale");
        require((_presale_balance[_msgSender()] + count) <= LIMIT_PRESALE_MINT, "Caller has already minted the maximum presale amount");
        require((_current + count)                       <= SUPPLY_MAX, "Attempting to mint more tokens than are available");
        require(msg.value >= PRICE_PER_TOKEN_PRESALE * count, "Minting fee not met");

        for(uint256 i = 1; i <= count; i++) {
            _mint(_msgSender(), _current + i);
        }

        // update supply count
        _presale_balance[_msgSender()] += count;
        MINTED = _current + count;
    }
}

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



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

pragma solidity ^0.8.0;

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

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



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

pragma solidity ^0.8.0;

import "./IERC165.sol";

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

// File: @openzeppelin/contracts/utils/cryptography/MerkleProof.sol



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

pragma solidity ^0.8.0;

/**
 * @dev These functions deal with verification of Merkle Trees proofs.
 *
 * The proofs can be generated using the JavaScript library
 * https://github.com/miguelmota/merkletreejs[merkletreejs].
 * Note: the hashing algorithm should be keccak256 and pair sorting should be enabled.
 *
 * See `test/utils/cryptography/MerkleProof.test.js` for some examples.
 */
library MerkleProof {
    /**
     * @dev Returns true if a `leaf` can be proved to be a part of a Merkle tree
     * defined by `root`. For this, a `proof` must be provided, containing
     * sibling hashes on the branch from the leaf to the root of the tree. Each
     * pair of leaves and each pair of pre-images are assumed to be sorted.
     */
    function verify(
        bytes32[] memory proof,
        bytes32 root,
        bytes32 leaf
    ) internal pure returns (bool) {
        return processProof(proof, leaf) == root;
    }

    /**
     * @dev Returns the rebuilt hash obtained by traversing a Merklee tree up
     * from `leaf` using `proof`. A `proof` is valid if and only if the rebuilt
     * hash matches the root of the tree. When processing the proof, the pairs
     * of leafs & pre-images are assumed to be sorted.
     *
     * _Available since v4.4._
     */
    function processProof(bytes32[] memory proof, bytes32 leaf) internal pure returns (bytes32) {
        bytes32 computedHash = leaf;
        for (uint256 i = 0; i < proof.length; i++) {
            bytes32 proofElement = proof[i];
            if (computedHash <= proofElement) {
                // Hash(current computed hash + current element of the proof)
                computedHash = keccak256(abi.encodePacked(computedHash, proofElement));
            } else {
                // Hash(current element of the proof + current computed hash)
                computedHash = keccak256(abi.encodePacked(proofElement, computedHash));
            }
        }
        return computedHash;
    }
}

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



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

pragma solidity ^0.8.0;

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

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

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

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

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

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



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

pragma solidity ^0.8.0;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

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

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



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

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/token/ERC721/extensions/IERC721Metadata.sol



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

pragma solidity ^0.8.0;

import "../IERC721.sol";

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

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

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

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



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

pragma solidity ^0.8.0;

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

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



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

pragma solidity ^0.8.0;

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

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

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

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

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

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

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

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

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

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

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

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

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

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



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

pragma solidity ^0.8.0;

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

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

    // Token name
    string private _name;

    // Token symbol
    string private _symbol;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

        _approve(to, tokenId);
    }

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

        return _tokenApprovals[tokenId];
    }

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

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

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

        _transfer(from, to, tokenId);
    }

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (access/Ownable.sol)

pragma solidity ^0.8.0;

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

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

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

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

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

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

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

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

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