contract.sol

///////////////////////////////////////////
// File: /app/contracts/Indelible.sol


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

    import "erc721a/contracts/ERC721A.sol";
    import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
    import "@openzeppelin/contracts/access/Ownable.sol";
    import "@openzeppelin/contracts/utils/Base64.sol";
    import "@openzeppelin/contracts/utils/cryptography/MerkleProof.sol";
    import "@openzeppelin/contracts/utils/Address.sol";
    import "./SSTORE2.sol";
    import "./DynamicBuffer.sol";
    import "./HelperLib.sol";

    contract Indelible is ERC721A, ReentrancyGuard, Ownable {
        using HelperLib for uint;
        using DynamicBuffer for bytes;

        struct LinkedTraitDTO {
            uint[] traitA;
            uint[] traitB;
        }

        struct TraitDTO {
            string name;
            string mimetype;
            bytes data;
            bool useExistingData;
            uint existingDataIndex;
        }
        
        struct Trait {
            string name;
            string mimetype;
        }

        struct ContractData {
            string name;
            string description;
            string image;
            string banner;
            string website;
            uint royalties;
            string royaltiesRecipient;
        }

        struct WithdrawRecipient {
            string name;
            string imageUrl;
            address recipientAddress;
            uint percentage;
        }

        mapping(uint => address[]) internal _traitDataPointers;
        mapping(uint => mapping(uint => Trait)) internal _traitDetails;
        mapping(uint => bool) internal _renderTokenOffChain;
        mapping(uint => mapping(uint => uint[])) internal _linkedTraits;

        uint private constant DEVELOPER_FEE = 250; // of 10,000 = 2.5%
        uint private constant NUM_LAYERS = 9;
        uint private constant MAX_BATCH_MINT = 20;
        uint[][NUM_LAYERS] private TIERS;
        string[] private LAYER_NAMES = [unicode"Jewelry", unicode"Beauty Marks", unicode"Eyes", unicode"Pretty Mouths", unicode"Necks", unicode"Hair Hats and Wigs", unicode"Punkins", unicode"Zodiak", unicode"Spooky Sky"];
            bool private shouldWrapSVG = true;
            string private backgroundColor = "transparent";
            
        WithdrawRecipient[1] public withdrawRecipients;
        bool public isContractSealed;
        uint public constant maxSupply = 6969;
        uint public maxPerAddress = 20;
        uint public publicMintPrice = 0.006969 ether;
        string public baseURI = "";
        bool public isPublicMintActive;
        
        bytes32 private merkleRoot;
        uint public allowListPrice = 0.000 ether;
        uint public maxPerAllowList = 3;
        bool public isAllowListActive;
        
        ContractData public contractData = ContractData(unicode"Punkin Spicies", unicode"6969 Little Punk Cuties Derivative Spicy and On Chain", "https://indeliblelabs-prod.s3.us-east-2.amazonaws.com/profile/196f7277-390d-45ff-a605-9c8de357782e", "https://indeliblelabs-prod.s3.us-east-2.amazonaws.com/banner/196f7277-390d-45ff-a605-9c8de357782e", "", 500, "0xf2c0149F0cff4c19b9819d1084f465DF0E1b3795");

        constructor() ERC721A(unicode"Punkin Spicies", unicode"PunkinSpicies") {
            TIERS[0] = [64,206,1744,1752,3203];
TIERS[1] = [109,321,349,1561,1879,2750];
TIERS[2] = [53,74,87,100,131,136,144,195,199,208,233,327,440,441,500,518,609,711,749,1114];
TIERS[3] = [29,65,216,315,592,786,898,1200,1302,1566];
TIERS[4] = [494,1027,1102,1689,2657];
TIERS[5] = [9,18,19,29,41,42,51,70,87,89,91,92,104,124,135,144,150,151,172,182,182,193,194,197,201,217,218,235,235,255,261,291,312,384,409,553,832];
TIERS[6] = [40,80,81,149,185,198,257,342,383,435,674,679,869,1237,1360];
TIERS[7] = [107,107,160,204,212,545,616,630,803,808,1121,1656];
TIERS[8] = [6969];
            withdrawRecipients[0] = WithdrawRecipient(unicode"null",unicode"null", 0x5FD2E3ba05C862E62a34B9F63c45C0DF622Ac112, 5000);
        }

        modifier whenMintActive() {
            require(isMintActive(), "Minting is not active");
            _;
        }

        modifier whenUnsealed() {
            require(!isContractSealed, "Contract is sealed");
            _;
        }

        receive() external payable {
            require(isPublicMintActive, "Public minting is not active");
            handleMint(msg.value / publicMintPrice);
        }

        function rarityGen(uint _randinput, uint _rarityTier)
            internal
            view
            returns (uint)
        {
            uint currentLowerBound = 0;
            for (uint i = 0; i < TIERS[_rarityTier].length; i++) {
                uint thisPercentage = TIERS[_rarityTier][i];
                if (
                    _randinput >= currentLowerBound &&
                    _randinput < currentLowerBound + thisPercentage
                ) return i;
                currentLowerBound = currentLowerBound + thisPercentage;
            }

            revert();
        }
        
        function entropyForExtraData() internal view returns (uint24) {
            uint randomNumber = uint(
                keccak256(
                    abi.encodePacked(
                        tx.gasprice,
                        block.number,
                        block.timestamp,
                        block.difficulty,
                        blockhash(block.number - 1),
                        msg.sender
                    )
                )
            );
            return uint24(randomNumber);
        }
        
        function stringCompare(string memory a, string memory b) internal pure returns (bool) {
            return keccak256(abi.encodePacked(a)) == keccak256(abi.encodePacked(b));
        }

        function tokensAreDuplicates(uint tokenIdA, uint tokenIdB) public view returns (bool) {
            return stringCompare(
                tokenIdToHash(tokenIdA),
                tokenIdToHash(tokenIdB)
            );
        }
        
        function reRollDuplicate(
            uint tokenIdA,
            uint tokenIdB
        ) public whenUnsealed {
            require(tokensAreDuplicates(tokenIdA, tokenIdB), "All tokens must be duplicates");

            uint largerTokenId = tokenIdA > tokenIdB ? tokenIdA : tokenIdB;

            if (msg.sender != owner()) {
                require(msg.sender == ownerOf(largerTokenId), "Only the token owner or contract owner can re-roll");
            }
            
            _initializeOwnershipAt(largerTokenId);
            if (_exists(largerTokenId + 1)) {
                _initializeOwnershipAt(largerTokenId + 1);
            }

            _setExtraDataAt(largerTokenId, entropyForExtraData());
        }
        
        function _extraData(
            address from,
            address to,
            uint24 previousExtraData
        ) internal view virtual override returns (uint24) {
            return from == address(0) ? entropyForExtraData() : previousExtraData;
        }

        function getTokenSeed(uint _tokenId) internal view returns (uint24) {
            return _ownershipOf(_tokenId).extraData;
        }

        function tokenIdToHash(
            uint _tokenId
        ) public view returns (string memory) {
            require(_exists(_tokenId), "Invalid token");
            // This will generate a NUM_LAYERS * 3 character string.
            bytes memory hashBytes = DynamicBuffer.allocate(NUM_LAYERS * 4);

            uint[] memory hash = new uint[](NUM_LAYERS);
            bool[] memory modifiedLayers = new bool[](NUM_LAYERS);

            for (uint i = 0; i < NUM_LAYERS; i++) {
                uint traitIndex = hash[i];
                if (modifiedLayers[i] == false) {
                    uint _randinput = uint(
                        uint(
                            keccak256(
                                abi.encodePacked(
                                    getTokenSeed(_tokenId),
                                    _tokenId,
                                    _tokenId + i
                                )
                            )
                        ) % maxSupply
                    );
    
                    traitIndex = rarityGen(_randinput, i);
                    hash[i] = traitIndex;
                }

                if (_linkedTraits[i][traitIndex].length > 0) {
                    hash[_linkedTraits[i][traitIndex][0]] = _linkedTraits[i][traitIndex][1];
                    modifiedLayers[_linkedTraits[i][traitIndex][0]] = true;
                }
            }

            for (uint i = 0; i < hash.length; i++) {
                if (hash[i] < 10) {
                    hashBytes.appendSafe("00");
                } else if (hash[i] < 100) {
                    hashBytes.appendSafe("0");
                }
                if (hash[i] > 999) {
                    hashBytes.appendSafe("999");
                } else {
                    hashBytes.appendSafe(bytes(_toString(hash[i])));
                }
            }

            return string(hashBytes);
        }

        function handleMint(uint256 _count) internal whenMintActive returns (uint256) {
            uint256 totalMinted = _totalMinted();
            require(_count > 0, "Invalid token count");
            require(totalMinted + _count <= maxSupply, "All tokens are gone");

            
            if (isPublicMintActive) {
                if (msg.sender != owner()) {
                    require(_numberMinted(msg.sender) + _count <= maxPerAddress, "Exceeded max mints allowed");
                }
                require(msg.sender == tx.origin, "EOAs only");
                require(_count * publicMintPrice == msg.value, "Incorrect amount of ether sent");
            }
            
            uint256 batchCount = _count / MAX_BATCH_MINT;
            uint256 remainder = _count % MAX_BATCH_MINT;

            for (uint256 i = 0; i < batchCount; i++) {
                _mint(msg.sender, MAX_BATCH_MINT);
            }

            if (remainder > 0) {
                _mint(msg.sender, remainder);
            }

            return totalMinted;
        }

        function mint(uint256 _count, bytes32[] calldata merkleProof)
            external
            payable
            nonReentrant
            whenMintActive
            returns (uint)
        {
            
                if (!isPublicMintActive) {
                    if (msg.sender != owner()) {
                        require(onAllowList(msg.sender, merkleProof), "Not on allow list");
                        require(_numberMinted(msg.sender) + _count <= maxPerAllowList, "Exceeded max mints allowed");
                    }
                    require(_count * allowListPrice == msg.value, "Incorrect amount of ether sent");
                }
                
                uint256 totalMinted = handleMint(_count);
    
                return totalMinted;
        }

        function isMintActive() public view returns (bool) {
            return _totalMinted() < maxSupply && (isPublicMintActive || isAllowListActive);
        }

        function hashToSVG(string memory _hash)
            public
            view
            returns (string memory)
        {
            uint thisTraitIndex;
            
            bytes memory svgBytes = DynamicBuffer.allocate(1024 * 128);
            svgBytes.appendSafe('<svg width="1200" height="1200" viewBox="0 0 1200 1200" version="1.2" xmlns="http://www.w3.org/2000/svg" style="background-color:');
            svgBytes.appendSafe(
                abi.encodePacked(
                    backgroundColor,
                    ";background-image:url("
                )
            );

            for (uint i = 0; i < NUM_LAYERS - 1; i++) {
                thisTraitIndex = HelperLib.parseInt(
                    HelperLib._substring(_hash, (i * 3), (i * 3) + 3)
                );
                svgBytes.appendSafe(
                    abi.encodePacked(
                        "data:",
                        _traitDetails[i][thisTraitIndex].mimetype,
                        ";base64,",
                        Base64.encode(SSTORE2.read(_traitDataPointers[i][thisTraitIndex])),
                        "),url("
                    )
                );
            }

            thisTraitIndex = HelperLib.parseInt(
                HelperLib._substring(_hash, (NUM_LAYERS * 3) - 3, NUM_LAYERS * 3)
            );

            svgBytes.appendSafe(
                abi.encodePacked(
                    "data:",
                    _traitDetails[NUM_LAYERS - 1][thisTraitIndex].mimetype,
                    ";base64,",
                    Base64.encode(SSTORE2.read(_traitDataPointers[NUM_LAYERS - 1][thisTraitIndex])),
                    ');background-repeat:no-repeat;background-size:contain;background-position:center;image-rendering:-webkit-optimize-contrast;-ms-interpolation-mode:nearest-neighbor;image-rendering:-moz-crisp-edges;image-rendering:pixelated;"></svg>'
                )
            );

            return string(
                abi.encodePacked(
                    "data:image/svg+xml;base64,",
                    Base64.encode(svgBytes)
                )
            );
        }

        function hashToMetadata(string memory _hash)
            public
            view
            returns (string memory)
        {
            bytes memory metadataBytes = DynamicBuffer.allocate(1024 * 128);
            metadataBytes.appendSafe("[");

            for (uint i = 0; i < NUM_LAYERS; i++) {
                uint thisTraitIndex = HelperLib.parseInt(
                    HelperLib._substring(_hash, (i * 3), (i * 3) + 3)
                );
                metadataBytes.appendSafe(
                    abi.encodePacked(
                        '{"trait_type":"',
                        LAYER_NAMES[i],
                        '","value":"',
                        _traitDetails[i][thisTraitIndex].name,
                        '"}'
                    )
                );
                
                if (i == NUM_LAYERS - 1) {
                    metadataBytes.appendSafe("]");
                } else {
                    metadataBytes.appendSafe(",");
                }
            }

            return string(metadataBytes);
        }

        
        function onAllowList(address addr, bytes32[] calldata merkleProof) public view returns (bool) {
            return MerkleProof.verify(merkleProof, merkleRoot, keccak256(abi.encodePacked(addr)));
        }
        

        function tokenURI(uint _tokenId)
            public
            view
            override
            returns (string memory)
        {
            require(_exists(_tokenId), "Invalid token");
            require(_traitDataPointers[0].length > 0,  "Traits have not been added");

            string memory tokenHash = tokenIdToHash(_tokenId);

            bytes memory jsonBytes = DynamicBuffer.allocate(1024 * 128);
            jsonBytes.appendSafe(unicode"{\"name\":\"Punkin Spicies #");

            jsonBytes.appendSafe(
                abi.encodePacked(
                    _toString(_tokenId),
                    "\",\"description\":\"",
                    contractData.description,
                    "\","
                )
            );

            if (bytes(baseURI).length > 0 && _renderTokenOffChain[_tokenId]) {
                jsonBytes.appendSafe(
                    abi.encodePacked(
                        '"image":"',
                        baseURI,
                        _toString(_tokenId),
                        "?dna=",
                        tokenHash,
                        '&network=mainnet",'
                    )
                );
            } else {
                string memory svgCode = "";
                if (shouldWrapSVG) {
                    string memory svgString = hashToSVG(tokenHash);
                    svgCode = string(
                        abi.encodePacked(
                            "data:image/svg+xml;base64,",
                            Base64.encode(
                                abi.encodePacked(
                                    '<svg width="100%" height="100%" viewBox="0 0 1200 1200" version="1.2" xmlns="http://www.w3.org/2000/svg"><image width="1200" height="1200" href="',
                                    svgString,
                                    '"></image></svg>'
                                )
                            )
                        )
                    );
                    jsonBytes.appendSafe(
                        abi.encodePacked(
                            '"svg_image_data":"',
                            svgString,
                            '",'
                        )
                    );
                } else {
                    svgCode = hashToSVG(tokenHash);
                }

                jsonBytes.appendSafe(
                    abi.encodePacked(
                        '"image_data":"',
                        svgCode,
                        '",'
                    )
                );
            }

            jsonBytes.appendSafe(
                abi.encodePacked(
                    '"attributes":',
                    hashToMetadata(tokenHash),
                    "}"
                )
            );

            return string(
                abi.encodePacked(
                    "data:application/json;base64,",
                    Base64.encode(jsonBytes)
                )
            );
        }

        function contractURI()
            public
            view
            returns (string memory)
        {
            return string(
                abi.encodePacked(
                    "data:application/json;base64,",
                    Base64.encode(
                        abi.encodePacked(
                            '{"name":"',
                            contractData.name,
                            '","description":"',
                            contractData.description,
                            '","image":"',
                            contractData.image,
                            '","banner":"',
                            contractData.banner,
                            '","external_link":"',
                            contractData.website,
                            '","seller_fee_basis_points":',
                            _toString(contractData.royalties),
                            ',"fee_recipient":"',
                            contractData.royaltiesRecipient,
                            '"}'
                        )
                    )
                )
            );
        }

        function tokenIdToSVG(uint _tokenId)
            public
            view
            returns (string memory)
        {
            return hashToSVG(tokenIdToHash(_tokenId));
        }

        function traitDetails(uint _layerIndex, uint _traitIndex)
            public
            view
            returns (Trait memory)
        {
            return _traitDetails[_layerIndex][_traitIndex];
        }

        function traitData(uint _layerIndex, uint _traitIndex)
            public
            view
            returns (string memory)
        {
            return string(SSTORE2.read(_traitDataPointers[_layerIndex][_traitIndex]));
        }

        function getLinkedTraits(uint _layerIndex, uint _traitIndex)
            public
            view
            returns (uint[] memory)
        {
            return _linkedTraits[_layerIndex][_traitIndex];
        }

        function addLayer(uint _layerIndex, TraitDTO[] memory traits)
            public
            onlyOwner
            whenUnsealed
        {
            require(TIERS[_layerIndex].length == traits.length, "Traits size does not match tiers for this index");
            address[] memory dataPointers = new address[](traits.length);
            for (uint i = 0; i < traits.length; i++) {
                if (traits[i].useExistingData) {
                    dataPointers[i] = dataPointers[traits[i].existingDataIndex];
                } else {
                    dataPointers[i] = SSTORE2.write(traits[i].data);
                }
                _traitDetails[_layerIndex][i] = Trait(traits[i].name, traits[i].mimetype);
            }
            _traitDataPointers[_layerIndex] = dataPointers;
            return;
        }

        function addTrait(uint _layerIndex, uint _traitIndex, TraitDTO memory trait)
            public
            onlyOwner
            whenUnsealed
        {
            _traitDetails[_layerIndex][_traitIndex] = Trait(trait.name, trait.mimetype);
            address[] memory dataPointers = _traitDataPointers[_layerIndex];
            if (trait.useExistingData) {
                dataPointers[_traitIndex] = dataPointers[trait.existingDataIndex];
            } else {
                dataPointers[_traitIndex] = SSTORE2.write(trait.data);
            }
            _traitDataPointers[_layerIndex] = dataPointers;
            return;
        }

        function setLinkedTraits(LinkedTraitDTO[] memory linkedTraits)
            public
            onlyOwner
            whenUnsealed
        {
            for (uint i = 0; i < linkedTraits.length; i++) {
                _linkedTraits[linkedTraits[i].traitA[0]][linkedTraits[i].traitA[1]] = [linkedTraits[i].traitB[0],linkedTraits[i].traitB[1]];
            }
        }

        function setContractData(ContractData memory _contractData) external onlyOwner whenUnsealed {
            contractData = _contractData;
        }

        function setMaxPerAddress(uint _maxPerAddress) external onlyOwner {
            maxPerAddress = _maxPerAddress;
        }

        function setBaseURI(string memory _baseURI) external onlyOwner {
            baseURI = _baseURI;
        }

        function setBackgroundColor(string memory _backgroundColor) external onlyOwner whenUnsealed {
            backgroundColor = _backgroundColor;
        }

        function setRenderOfTokenId(uint _tokenId, bool _renderOffChain) external {
            require(msg.sender == ownerOf(_tokenId), "Only the token owner can set the render method");
            _renderTokenOffChain[_tokenId] = _renderOffChain;
        }

        
        function setMerkleRoot(bytes32 newMerkleRoot) external onlyOwner {
            merkleRoot = newMerkleRoot;
        }

        function setMaxPerAllowList(uint _maxPerAllowList) external onlyOwner {
            maxPerAllowList = _maxPerAllowList;
        }

        function setAllowListPrice(uint _allowListPrice) external onlyOwner {
            allowListPrice = _allowListPrice;
        }

        function toggleAllowListMint() external onlyOwner {
            isAllowListActive = !isAllowListActive;
        }
        

        function toggleWrapSVG() external onlyOwner {
            shouldWrapSVG = !shouldWrapSVG;
        }

        function togglePublicMint() external onlyOwner {
            isPublicMintActive = !isPublicMintActive;
        }

        function sealContract() external whenUnsealed onlyOwner {
            isContractSealed = true;
        }

        function withdraw() external onlyOwner nonReentrant {
            uint balance = address(this).balance;
            uint amount = (balance * (10000 - DEVELOPER_FEE)) / 10000;
            uint distAmount = 0;
            uint totalDistributionPercentage = 0;

            address payable receiver = payable(owner());
            address payable dev = payable(0xEA208Da933C43857683C04BC76e3FD331D7bfdf7);
            Address.sendValue(dev, balance - amount);

            if (withdrawRecipients.length > 0) {
                for (uint i = 0; i < withdrawRecipients.length; i++) {
                    totalDistributionPercentage = totalDistributionPercentage + withdrawRecipients[i].percentage;
                    address payable currRecepient = payable(withdrawRecipients[i].recipientAddress);
                    distAmount = (amount * (10000 - withdrawRecipients[i].percentage)) / 10000;

                    Address.sendValue(currRecepient, amount - distAmount);
                }
            }
            balance = address(this).balance;
            Address.sendValue(receiver, balance);
        }
    }


///////////////////////////////////////////
// File: /app/contracts/DynamicBuffer.sol

// SPDX-License-Identifier: MIT
// Copyright (c) 2021 the ethier authors (github.com/divergencetech/ethier)

pragma solidity >=0.8.0;

/// @title DynamicBuffer
/// @author David Huber (@cxkoda) and Simon Fremaux (@dievardump). See also
///         https://raw.githubusercontent.com/dievardump/solidity-dynamic-buffer
/// @notice This library is used to allocate a big amount of container memory
//          which will be subsequently filled without needing to reallocate
///         memory.
/// @dev First, allocate memory.
///      Then use `buffer.appendUnchecked(theBytes)` or `appendSafe()` if
///      bounds checking is required.
library DynamicBuffer {
    /// @notice Allocates container space for the DynamicBuffer
    /// @param capacity The intended max amount of bytes in the buffer
    /// @return buffer The memory location of the buffer
    /// @dev Allocates `capacity + 0x60` bytes of space
    ///      The buffer array starts at the first container data position,
    ///      (i.e. `buffer = container + 0x20`)
    function allocate(uint256 capacity)
        internal
        pure
        returns (bytes memory buffer)
    {
        assembly {
            // Get next-free memory address
            let container := mload(0x40)

            // Allocate memory by setting a new next-free address
            {
                // Add 2 x 32 bytes in size for the two length fields
                // Add 32 bytes safety space for 32B chunked copy
                let size := add(capacity, 0x60)
                let newNextFree := add(container, size)
                mstore(0x40, newNextFree)
            }

            // Set the correct container length
            {
                let length := add(capacity, 0x40)
                mstore(container, length)
            }

            // The buffer starts at idx 1 in the container (0 is length)
            buffer := add(container, 0x20)

            // Init content with length 0
            mstore(buffer, 0)
        }

        return buffer;
    }

    /// @notice Appends data to buffer, and update buffer length
    /// @param buffer the buffer to append the data to
    /// @param data the data to append
    /// @dev Does not perform out-of-bound checks (container capacity)
    ///      for efficiency.
    function appendUnchecked(bytes memory buffer, bytes memory data)
        internal
        pure
    {
        assembly {
            let length := mload(data)
            for {
                data := add(data, 0x20)
                let dataEnd := add(data, length)
                let copyTo := add(buffer, add(mload(buffer), 0x20))
            } lt(data, dataEnd) {
                data := add(data, 0x20)
                copyTo := add(copyTo, 0x20)
            } {
                // Copy 32B chunks from data to buffer.
                // This may read over data array boundaries and copy invalid
                // bytes, which doesn't matter in the end since we will
                // later set the correct buffer length, and have allocated an
                // additional word to avoid buffer overflow.
                mstore(copyTo, mload(data))
            }

            // Update buffer length
            mstore(buffer, add(mload(buffer), length))
        }
    }

    /// @notice Appends data to buffer, and update buffer length
    /// @param buffer the buffer to append the data to
    /// @param data the data to append
    /// @dev Performs out-of-bound checks and calls `appendUnchecked`.
    function appendSafe(bytes memory buffer, bytes memory data) internal pure {
        uint256 capacity;
        uint256 length;
        assembly {
            capacity := sub(mload(sub(buffer, 0x20)), 0x40)
            length := mload(buffer)
        }

        require(
            length + data.length <= capacity,
            "DynamicBuffer: Appending out of bounds."
        );
        appendUnchecked(buffer, data);
    }
}

///////////////////////////////////////////
// File: /app/contracts/HelperLib.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.14;

library HelperLib {
    function parseInt(string memory _a)
        internal
        pure
        returns (uint8 _parsedInt)
    {
        bytes memory bresult = bytes(_a);
        uint8 mint = 0;
        for (uint8 i = 0; i < bresult.length; i++) {
            if (
                (uint8(uint8(bresult[i])) >= 48) &&
                (uint8(uint8(bresult[i])) <= 57)
            ) {
                mint *= 10;
                mint += uint8(bresult[i]) - 48;
            }
        }
        return mint;
    }

    function _substring(
        string memory str,
        uint256 startIndex,
        uint256 endIndex
    ) internal pure returns (string memory) {
        bytes memory strBytes = bytes(str);
        bytes memory result = new bytes(endIndex - startIndex);
        for (uint256 i = startIndex; i < endIndex; i++) {
            result[i - startIndex] = strBytes[i];
        }
        return string(result);
    }
}

///////////////////////////////////////////
// File: /app/contracts/SSTORE2.sol

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

import "./utils/Bytecode.sol";

/**
  @title A key-value storage with auto-generated keys for storing chunks of data with a lower write & read cost.
  @author Agustin Aguilar <aa@horizon.io>

  Readme: https://github.com/0xsequence/sstore2#readme
*/
library SSTORE2 {
  error WriteError();

  /**
    @notice Stores `_data` and returns `pointer` as key for later retrieval
    @dev The pointer is a contract address with `_data` as code
    @param _data to be written
    @return pointer Pointer to the written `_data`
  */
  function write(bytes memory _data) internal returns (address pointer) {
    // Append 00 to _data so contract can't be called
    // Build init code
    bytes memory code = Bytecode.creationCodeFor(
      abi.encodePacked(
        hex'00',
        _data
      )
    );

    // Deploy contract using create
    assembly { pointer := create(0, add(code, 32), mload(code)) }

    // Address MUST be non-zero
    if (pointer == address(0)) revert WriteError();
  }

  /**
    @notice Reads the contents of the `_pointer` code as data, skips the first byte 
    @dev The function is intended for reading pointers generated by `write`
    @param _pointer to be read
    @return data read from `_pointer` contract
  */
  function read(address _pointer) internal view returns (bytes memory) {
    return Bytecode.codeAt(_pointer, 1, type(uint256).max);
  }

  /**
    @notice Reads the contents of the `_pointer` code as data, skips the first byte 
    @dev The function is intended for reading pointers generated by `write`
    @param _pointer to be read
    @param _start number of bytes to skip
    @return data read from `_pointer` contract
  */
  function read(address _pointer, uint256 _start) internal view returns (bytes memory) {
    return Bytecode.codeAt(_pointer, _start + 1, type(uint256).max);
  }

  /**
    @notice Reads the contents of the `_pointer` code as data, skips the first byte 
    @dev The function is intended for reading pointers generated by `write`
    @param _pointer to be read
    @param _start number of bytes to skip
    @param _end index before which to end extraction
    @return data read from `_pointer` contract
  */
  function read(address _pointer, uint256 _start, uint256 _end) internal view returns (bytes memory) {
    return Bytecode.codeAt(_pointer, _start + 1, _end + 1);
  }
}

///////////////////////////////////////////
// File: /app/contracts/utils/Bytecode.sol

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


library Bytecode {
  error InvalidCodeAtRange(uint256 _size, uint256 _start, uint256 _end);

  /**
    @notice Generate a creation code that results on a contract with `_code` as bytecode
    @param _code The returning value of the resulting `creationCode`
    @return creationCode (constructor) for new contract
  */
  function creationCodeFor(bytes memory _code) internal pure returns (bytes memory) {
    /*
      0x00    0x63         0x63XXXXXX  PUSH4 _code.length  size
      0x01    0x80         0x80        DUP1                size size
      0x02    0x60         0x600e      PUSH1 14            14 size size
      0x03    0x60         0x6000      PUSH1 00            0 14 size size
      0x04    0x39         0x39        CODECOPY            size
      0x05    0x60         0x6000      PUSH1 00            0 size
      0x06    0xf3         0xf3        RETURN
      <CODE>
    */

    return abi.encodePacked(
      hex"63",
      uint32(_code.length),
      hex"80_60_0E_60_00_39_60_00_F3",
      _code
    );
  }

  /**
    @notice Returns the size of the code on a given address
    @param _addr Address that may or may not contain code
    @return size of the code on the given `_addr`
  */
  function codeSize(address _addr) internal view returns (uint256 size) {
    assembly { size := extcodesize(_addr) }
  }

  /**
    @notice Returns the code of a given address
    @dev It will fail if `_end < _start`
    @param _addr Address that may or may not contain code
    @param _start number of bytes of code to skip on read
    @param _end index before which to end extraction
    @return oCode read from `_addr` deployed bytecode

    Forked from: https://gist.github.com/KardanovIR/fe98661df9338c842b4a30306d507fbd
  */
  function codeAt(address _addr, uint256 _start, uint256 _end) internal view returns (bytes memory oCode) {
    uint256 csize = codeSize(_addr);
    if (csize == 0) return bytes("");

    if (_start > csize) return bytes("");
    if (_end < _start) revert InvalidCodeAtRange(csize, _start, _end); 

    unchecked {
      uint256 reqSize = _end - _start;
      uint256 maxSize = csize - _start;

      uint256 size = maxSize < reqSize ? maxSize : reqSize;

      assembly {
        // allocate output byte array - this could also be done without assembly
        // by using o_code = new bytes(size)
        oCode := mload(0x40)
        // new "memory end" including padding
        mstore(0x40, add(oCode, and(add(add(size, 0x20), 0x1f), not(0x1f))))
        // store length in memory
        mstore(oCode, size)
        // actually retrieve the code, this needs assembly
        extcodecopy(_addr, add(oCode, 0x20), _start, size)
      }
    }
  }
}

///////////////////////////////////////////
// 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);
    }
}


///////////////////////////////////////////
// File: @openzeppelin/contracts/security/ReentrancyGuard.sol

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (security/ReentrancyGuard.sol)

pragma solidity ^0.8.0;

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

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

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

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

        _;

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


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

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

pragma solidity ^0.8.1;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     *
     * [IMPORTANT]
     * ====
     * You shouldn't rely on `isContract` to protect against flash loan attacks!
     *
     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
     * constructor.
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize/address.code.length, which returns 0
        // for contracts in construction, since the code is only stored at the end
        // of the constructor execution.

        return account.code.length > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        (bool success, ) = recipient.call{value: amount}("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain `call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

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

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

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

    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}


///////////////////////////////////////////
// File: @openzeppelin/contracts/utils/Base64.sol

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (utils/Base64.sol)

pragma solidity ^0.8.0;

/**
 * @dev Provides a set of functions to operate with Base64 strings.
 *
 * _Available since v4.5._
 */
library Base64 {
    /**
     * @dev Base64 Encoding/Decoding Table
     */
    string internal constant _TABLE = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

    /**
     * @dev Converts a `bytes` to its Bytes64 `string` representation.
     */
    function encode(bytes memory data) internal pure returns (string memory) {
        /**
         * Inspired by Brecht Devos (Brechtpd) implementation - MIT licence
         * https://github.com/Brechtpd/base64/blob/e78d9fd951e7b0977ddca77d92dc85183770daf4/base64.sol
         */
        if (data.length == 0) return "";

        // Loads the table into memory
        string memory table = _TABLE;

        // Encoding takes 3 bytes chunks of binary data from `bytes` data parameter
        // and split into 4 numbers of 6 bits.
        // The final Base64 length should be `bytes` data length multiplied by 4/3 rounded up
        // - `data.length + 2`  -> Round up
        // - `/ 3`              -> Number of 3-bytes chunks
        // - `4 *`              -> 4 characters for each chunk
        string memory result = new string(4 * ((data.length + 2) / 3));

        assembly {
            // Prepare the lookup table (skip the first "length" byte)
            let tablePtr := add(table, 1)

            // Prepare result pointer, jump over length
            let resultPtr := add(result, 32)

            // Run over the input, 3 bytes at a time
            for {
                let dataPtr := data
                let endPtr := add(data, mload(data))
            } lt(dataPtr, endPtr) {

            } {
                // Advance 3 bytes
                dataPtr := add(dataPtr, 3)
                let input := mload(dataPtr)

                // To write each character, shift the 3 bytes (18 bits) chunk
                // 4 times in blocks of 6 bits for each character (18, 12, 6, 0)
                // and apply logical AND with 0x3F which is the number of
                // the previous character in the ASCII table prior to the Base64 Table
                // The result is then added to the table to get the character to write,
                // and finally write it in the result pointer but with a left shift
                // of 256 (1 byte) - 8 (1 ASCII char) = 248 bits

                mstore8(resultPtr, mload(add(tablePtr, and(shr(18, input), 0x3F))))
                resultPtr := add(resultPtr, 1) // Advance

                mstore8(resultPtr, mload(add(tablePtr, and(shr(12, input), 0x3F))))
                resultPtr := add(resultPtr, 1) // Advance

                mstore8(resultPtr, mload(add(tablePtr, and(shr(6, input), 0x3F))))
                resultPtr := add(resultPtr, 1) // Advance

                mstore8(resultPtr, mload(add(tablePtr, and(input, 0x3F))))
                resultPtr := add(resultPtr, 1) // Advance
            }

            // When data `bytes` is not exactly 3 bytes long
            // it is padded with `=` characters at the end
            switch mod(mload(data), 3)
            case 1 {
                mstore8(sub(resultPtr, 1), 0x3d)
                mstore8(sub(resultPtr, 2), 0x3d)
            }
            case 2 {
                mstore8(sub(resultPtr, 1), 0x3d)
            }
        }

        return result;
    }
}


///////////////////////////////////////////
// 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/cryptography/MerkleProof.sol

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (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.
 *
 * WARNING: You should avoid using leaf values that are 64 bytes long prior to
 * hashing, or use a hash function other than keccak256 for hashing leaves.
 * This is because the concatenation of a sorted pair of internal nodes in
 * the merkle tree could be reinterpreted as a leaf value.
 */
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 Merkle 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 = _efficientHash(computedHash, proofElement);
            } else {
                // Hash(current element of the proof + current computed hash)
                computedHash = _efficientHash(proofElement, computedHash);
            }
        }
        return computedHash;
    }

    function _efficientHash(bytes32 a, bytes32 b) private pure returns (bytes32 value) {
        assembly {
            mstore(0x00, a)
            mstore(0x20, b)
            value := keccak256(0x00, 0x40)
        }
    }
}


///////////////////////////////////////////
// File: erc721a/contracts/ERC721A.sol

// SPDX-License-Identifier: MIT
// ERC721A Contracts v4.1.0
// Creator: Chiru Labs

pragma solidity ^0.8.4;

import './IERC721A.sol';

/**
 * @dev ERC721 token receiver interface.
 */
interface ERC721A__IERC721Receiver {
    function onERC721Received(
        address operator,
        address from,
        uint256 tokenId,
        bytes calldata data
    ) external returns (bytes4);
}

/**
 * @dev Implementation of https://eips.ethereum.org/EIPS/eip-721[ERC721] Non-Fungible Token Standard,
 * including the Metadata extension. Built to optimize for lower gas during batch mints.
 *
 * Assumes serials are sequentially minted starting at `_startTokenId()`
 * (defaults to 0, e.g. 0, 1, 2, 3..).
 *
 * Assumes that an owner cannot have more than 2**64 - 1 (max value of uint64) of supply.
 *
 * Assumes that the maximum token id cannot exceed 2**256 - 1 (max value of uint256).
 */
contract ERC721A is IERC721A {
    // Mask of an entry in packed address data.
    uint256 private constant BITMASK_ADDRESS_DATA_ENTRY = (1 << 64) - 1;

    // The bit position of `numberMinted` in packed address data.
    uint256 private constant BITPOS_NUMBER_MINTED = 64;

    // The bit position of `numberBurned` in packed address data.
    uint256 private constant BITPOS_NUMBER_BURNED = 128;

    // The bit position of `aux` in packed address data.
    uint256 private constant BITPOS_AUX = 192;

    // Mask of all 256 bits in packed address data except the 64 bits for `aux`.
    uint256 private constant BITMASK_AUX_COMPLEMENT = (1 << 192) - 1;

    // The bit position of `startTimestamp` in packed ownership.
    uint256 private constant BITPOS_START_TIMESTAMP = 160;

    // The bit mask of the `burned` bit in packed ownership.
    uint256 private constant BITMASK_BURNED = 1 << 224;

    // The bit position of the `nextInitialized` bit in packed ownership.
    uint256 private constant BITPOS_NEXT_INITIALIZED = 225;

    // The bit mask of the `nextInitialized` bit in packed ownership.
    uint256 private constant BITMASK_NEXT_INITIALIZED = 1 << 225;

    // The bit position of `extraData` in packed ownership.
    uint256 private constant BITPOS_EXTRA_DATA = 232;

    // Mask of all 256 bits in a packed ownership except the 24 bits for `extraData`.
    uint256 private constant BITMASK_EXTRA_DATA_COMPLEMENT = (1 << 232) - 1;

    // The mask of the lower 160 bits for addresses.
    uint256 private constant BITMASK_ADDRESS = (1 << 160) - 1;

    // The maximum `quantity` that can be minted with `_mintERC2309`.
    // This limit is to prevent overflows on the address data entries.
    // For a limit of 5000, a total of 3.689e15 calls to `_mintERC2309`
    // is required to cause an overflow, which is unrealistic.
    uint256 private constant MAX_MINT_ERC2309_QUANTITY_LIMIT = 5000;

    // The tokenId of the next token to be minted.
    uint256 private _currentIndex;

    // The number of tokens burned.
    uint256 private _burnCounter;

    // Token name
    string private _name;

    // Token symbol
    string private _symbol;

    // Mapping from token ID to ownership details
    // An empty struct value does not necessarily mean the token is unowned.
    // See `_packedOwnershipOf` implementation for details.
    //
    // Bits Layout:
    // - [0..159]   `addr`
    // - [160..223] `startTimestamp`
    // - [224]      `burned`
    // - [225]      `nextInitialized`
    // - [232..255] `extraData`
    mapping(uint256 => uint256) private _packedOwnerships;

    // Mapping owner address to address data.
    //
    // Bits Layout:
    // - [0..63]    `balance`
    // - [64..127]  `numberMinted`
    // - [128..191] `numberBurned`
    // - [192..255] `aux`
    mapping(address => uint256) private _packedAddressData;

    // 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;

    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
        _currentIndex = _startTokenId();
    }

    /**
     * @dev Returns the starting token ID.
     * To change the starting token ID, please override this function.
     */
    function _startTokenId() internal view virtual returns (uint256) {
        return 0;
    }

    /**
     * @dev Returns the next token ID to be minted.
     */
    function _nextTokenId() internal view returns (uint256) {
        return _currentIndex;
    }

    /**
     * @dev Returns the total number of tokens in existence.
     * Burned tokens will reduce the count.
     * To get the total number of tokens minted, please see `_totalMinted`.
     */
    function totalSupply() public view override returns (uint256) {
        // Counter underflow is impossible as _burnCounter cannot be incremented
        // more than `_currentIndex - _startTokenId()` times.
        unchecked {
            return _currentIndex - _burnCounter - _startTokenId();
        }
    }

    /**
     * @dev Returns the total amount of tokens minted in the contract.
     */
    function _totalMinted() internal view returns (uint256) {
        // Counter underflow is impossible as _currentIndex does not decrement,
        // and it is initialized to `_startTokenId()`
        unchecked {
            return _currentIndex - _startTokenId();
        }
    }

    /**
     * @dev Returns the total number of tokens burned.
     */
    function _totalBurned() internal view returns (uint256) {
        return _burnCounter;
    }

    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        // The interface IDs are constants representing the first 4 bytes of the XOR of
        // all function selectors in the interface. See: https://eips.ethereum.org/EIPS/eip-165
        // e.g. `bytes4(i.functionA.selector ^ i.functionB.selector ^ ...)`
        return
            interfaceId == 0x01ffc9a7 || // ERC165 interface ID for ERC165.
            interfaceId == 0x80ac58cd || // ERC165 interface ID for ERC721.
            interfaceId == 0x5b5e139f; // ERC165 interface ID for ERC721Metadata.
    }

    /**
     * @dev See {IERC721-balanceOf}.
     */
    function balanceOf(address owner) public view override returns (uint256) {
        if (owner == address(0)) revert BalanceQueryForZeroAddress();
        return _packedAddressData[owner] & BITMASK_ADDRESS_DATA_ENTRY;
    }

    /**
     * Returns the number of tokens minted by `owner`.
     */
    function _numberMinted(address owner) internal view returns (uint256) {
        return (_packedAddressData[owner] >> BITPOS_NUMBER_MINTED) & BITMASK_ADDRESS_DATA_ENTRY;
    }

    /**
     * Returns the number of tokens burned by or on behalf of `owner`.
     */
    function _numberBurned(address owner) internal view returns (uint256) {
        return (_packedAddressData[owner] >> BITPOS_NUMBER_BURNED) & BITMASK_ADDRESS_DATA_ENTRY;
    }

    /**
     * Returns the auxiliary data for `owner`. (e.g. number of whitelist mint slots used).
     */
    function _getAux(address owner) internal view returns (uint64) {
        return uint64(_packedAddressData[owner] >> BITPOS_AUX);
    }

    /**
     * Sets the auxiliary data for `owner`. (e.g. number of whitelist mint slots used).
     * If there are multiple variables, please pack them into a uint64.
     */
    function _setAux(address owner, uint64 aux) internal {
        uint256 packed = _packedAddressData[owner];
        uint256 auxCasted;
        // Cast `aux` with assembly to avoid redundant masking.
        assembly {
            auxCasted := aux
        }
        packed = (packed & BITMASK_AUX_COMPLEMENT) | (auxCasted << BITPOS_AUX);
        _packedAddressData[owner] = packed;
    }

    /**
     * Returns the packed ownership data of `tokenId`.
     */
    function _packedOwnershipOf(uint256 tokenId) private view returns (uint256) {
        uint256 curr = tokenId;

        unchecked {
            if (_startTokenId() <= curr)
                if (curr < _currentIndex) {
                    uint256 packed = _packedOwnerships[curr];
                    // If not burned.
                    if (packed & BITMASK_BURNED == 0) {
                        // Invariant:
                        // There will always be an ownership that has an address and is not burned
                        // before an ownership that does not have an address and is not burned.
                        // Hence, curr will not underflow.
                        //
                        // We can directly compare the packed value.
                        // If the address is zero, packed is zero.
                        while (packed == 0) {
                            packed = _packedOwnerships[--curr];
                        }
                        return packed;
                    }
                }
        }
        revert OwnerQueryForNonexistentToken();
    }

    /**
     * Returns the unpacked `TokenOwnership` struct from `packed`.
     */
    function _unpackedOwnership(uint256 packed) private pure returns (TokenOwnership memory ownership) {
        ownership.addr = address(uint160(packed));
        ownership.startTimestamp = uint64(packed >> BITPOS_START_TIMESTAMP);
        ownership.burned = packed & BITMASK_BURNED != 0;
        ownership.extraData = uint24(packed >> BITPOS_EXTRA_DATA);
    }

    /**
     * Returns the unpacked `TokenOwnership` struct at `index`.
     */
    function _ownershipAt(uint256 index) internal view returns (TokenOwnership memory) {
        return _unpackedOwnership(_packedOwnerships[index]);
    }

    /**
     * @dev Initializes the ownership slot minted at `index` for efficiency purposes.
     */
    function _initializeOwnershipAt(uint256 index) internal {
        if (_packedOwnerships[index] == 0) {
            _packedOwnerships[index] = _packedOwnershipOf(index);
        }
    }

    /**
     * Gas spent here starts off proportional to the maximum mint batch size.
     * It gradually moves to O(1) as tokens get transferred around in the collection over time.
     */
    function _ownershipOf(uint256 tokenId) internal view returns (TokenOwnership memory) {
        return _unpackedOwnership(_packedOwnershipOf(tokenId));
    }

    /**
     * @dev Packs ownership data into a single uint256.
     */
    function _packOwnershipData(address owner, uint256 flags) private view returns (uint256 result) {
        assembly {
            // Mask `owner` to the lower 160 bits, in case the upper bits somehow aren't clean.
            owner := and(owner, BITMASK_ADDRESS)
            // `owner | (block.timestamp << BITPOS_START_TIMESTAMP) | flags`.
            result := or(owner, or(shl(BITPOS_START_TIMESTAMP, timestamp()), flags))
        }
    }

    /**
     * @dev See {IERC721-ownerOf}.
     */
    function ownerOf(uint256 tokenId) public view override returns (address) {
        return address(uint160(_packedOwnershipOf(tokenId)));
    }

    /**
     * @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) {
        if (!_exists(tokenId)) revert URIQueryForNonexistentToken();

        string memory baseURI = _baseURI();
        return bytes(baseURI).length != 0 ? string(abi.encodePacked(baseURI, _toString(tokenId))) : '';
    }

    /**
     * @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, it can be overridden in child contracts.
     */
    function _baseURI() internal view virtual returns (string memory) {
        return '';
    }

    /**
     * @dev Returns the `nextInitialized` flag set if `quantity` equals 1.
     */
    function _nextInitializedFlag(uint256 quantity) private pure returns (uint256 result) {
        // For branchless setting of the `nextInitialized` flag.
        assembly {
            // `(quantity == 1) << BITPOS_NEXT_INITIALIZED`.
            result := shl(BITPOS_NEXT_INITIALIZED, eq(quantity, 1))
        }
    }

    /**
     * @dev See {IERC721-approve}.
     */
    function approve(address to, uint256 tokenId) public override {
        address owner = ownerOf(tokenId);

        if (_msgSenderERC721A() != owner)
            if (!isApprovedForAll(owner, _msgSenderERC721A())) {
                revert ApprovalCallerNotOwnerNorApproved();
            }

        _tokenApprovals[tokenId] = to;
        emit Approval(owner, to, tokenId);
    }

    /**
     * @dev See {IERC721-getApproved}.
     */
    function getApproved(uint256 tokenId) public view override returns (address) {
        if (!_exists(tokenId)) revert ApprovalQueryForNonexistentToken();

        return _tokenApprovals[tokenId];
    }

    /**
     * @dev See {IERC721-setApprovalForAll}.
     */
    function setApprovalForAll(address operator, bool approved) public virtual override {
        if (operator == _msgSenderERC721A()) revert ApproveToCaller();

        _operatorApprovals[_msgSenderERC721A()][operator] = approved;
        emit ApprovalForAll(_msgSenderERC721A(), 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-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 {
        transferFrom(from, to, tokenId);
        if (to.code.length != 0)
            if (!_checkContractOnERC721Received(from, to, tokenId, _data)) {
                revert TransferToNonERC721ReceiverImplementer();
            }
    }

    /**
     * @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`),
     */
    function _exists(uint256 tokenId) internal view returns (bool) {
        return
            _startTokenId() <= tokenId &&
            tokenId < _currentIndex && // If within bounds,
            _packedOwnerships[tokenId] & BITMASK_BURNED == 0; // and not burned.
    }

    /**
     * @dev Equivalent to `_safeMint(to, quantity, '')`.
     */
    function _safeMint(address to, uint256 quantity) internal {
        _safeMint(to, quantity, '');
    }

    /**
     * @dev Safely mints `quantity` tokens and transfers them to `to`.
     *
     * Requirements:
     *
     * - If `to` refers to a smart contract, it must implement
     *   {IERC721Receiver-onERC721Received}, which is called for each safe transfer.
     * - `quantity` must be greater than 0.
     *
     * See {_mint}.
     *
     * Emits a {Transfer} event for each mint.
     */
    function _safeMint(
        address to,
        uint256 quantity,
        bytes memory _data
    ) internal {
        _mint(to, quantity);

        unchecked {
            if (to.code.length != 0) {
                uint256 end = _currentIndex;
                uint256 index = end - quantity;
                do {
                    if (!_checkContractOnERC721Received(address(0), to, index++, _data)) {
                        revert TransferToNonERC721ReceiverImplementer();
                    }
                } while (index < end);
                // Reentrancy protection.
                if (_currentIndex != end) revert();
            }
        }
    }

    /**
     * @dev Mints `quantity` tokens and transfers them to `to`.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - `quantity` must be greater than 0.
     *
     * Emits a {Transfer} event for each mint.
     */
    function _mint(address to, uint256 quantity) internal {
        uint256 startTokenId = _currentIndex;
        if (to == address(0)) revert MintToZeroAddress();
        if (quantity == 0) revert MintZeroQuantity();

        _beforeTokenTransfers(address(0), to, startTokenId, quantity);

        // Overflows are incredibly unrealistic.
        // `balance` and `numberMinted` have a maximum limit of 2**64.
        // `tokenId` has a maximum limit of 2**256.
        unchecked {
            // Updates:
            // - `balance += quantity`.
            // - `numberMinted += quantity`.
            //
            // We can directly add to the `balance` and `numberMinted`.
            _packedAddressData[to] += quantity * ((1 << BITPOS_NUMBER_MINTED) | 1);

            // Updates:
            // - `address` to the owner.
            // - `startTimestamp` to the timestamp of minting.
            // - `burned` to `false`.
            // - `nextInitialized` to `quantity == 1`.
            _packedOwnerships[startTokenId] = _packOwnershipData(
                to,
                _nextInitializedFlag(quantity) | _nextExtraData(address(0), to, 0)
            );

            uint256 tokenId = startTokenId;
            uint256 end = startTokenId + quantity;
            do {
                emit Transfer(address(0), to, tokenId++);
            } while (tokenId < end);

            _currentIndex = end;
        }
        _afterTokenTransfers(address(0), to, startTokenId, quantity);
    }

    /**
     * @dev Mints `quantity` tokens and transfers them to `to`.
     *
     * This function is intended for efficient minting only during contract creation.
     *
     * It emits only one {ConsecutiveTransfer} as defined in
     * [ERC2309](https://eips.ethereum.org/EIPS/eip-2309),
     * instead of a sequence of {Transfer} event(s).
     *
     * Calling this function outside of contract creation WILL make your contract
     * non-compliant with the ERC721 standard.
     * For full ERC721 compliance, substituting ERC721 {Transfer} event(s) with the ERC2309
     * {ConsecutiveTransfer} event is only permissible during contract creation.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - `quantity` must be greater than 0.
     *
     * Emits a {ConsecutiveTransfer} event.
     */
    function _mintERC2309(address to, uint256 quantity) internal {
        uint256 startTokenId = _currentIndex;
        if (to == address(0)) revert MintToZeroAddress();
        if (quantity == 0) revert MintZeroQuantity();
        if (quantity > MAX_MINT_ERC2309_QUANTITY_LIMIT) revert MintERC2309QuantityExceedsLimit();

        _beforeTokenTransfers(address(0), to, startTokenId, quantity);

        // Overflows are unrealistic due to the above check for `quantity` to be below the limit.
        unchecked {
            // Updates:
            // - `balance += quantity`.
            // - `numberMinted += quantity`.
            //
            // We can directly add to the `balance` and `numberMinted`.
            _packedAddressData[to] += quantity * ((1 << BITPOS_NUMBER_MINTED) | 1);

            // Updates:
            // - `address` to the owner.
            // - `startTimestamp` to the timestamp of minting.
            // - `burned` to `false`.
            // - `nextInitialized` to `quantity == 1`.
            _packedOwnerships[startTokenId] = _packOwnershipData(
                to,
                _nextInitializedFlag(quantity) | _nextExtraData(address(0), to, 0)
            );

            emit ConsecutiveTransfer(startTokenId, startTokenId + quantity - 1, address(0), to);

            _currentIndex = startTokenId + quantity;
        }
        _afterTokenTransfers(address(0), to, startTokenId, quantity);
    }

    /**
     * @dev Returns the storage slot and value for the approved address of `tokenId`.
     */
    function _getApprovedAddress(uint256 tokenId)
        private
        view
        returns (uint256 approvedAddressSlot, address approvedAddress)
    {
        mapping(uint256 => address) storage tokenApprovalsPtr = _tokenApprovals;
        // The following is equivalent to `approvedAddress = _tokenApprovals[tokenId]`.
        assembly {
            // Compute the slot.
            mstore(0x00, tokenId)
            mstore(0x20, tokenApprovalsPtr.slot)
            approvedAddressSlot := keccak256(0x00, 0x40)
            // Load the slot's value from storage.
            approvedAddress := sload(approvedAddressSlot)
        }
    }

    /**
     * @dev Returns whether the `approvedAddress` is equals to `from` or `msgSender`.
     */
    function _isOwnerOrApproved(
        address approvedAddress,
        address from,
        address msgSender
    ) private pure returns (bool result) {
        assembly {
            // Mask `from` to the lower 160 bits, in case the upper bits somehow aren't clean.
            from := and(from, BITMASK_ADDRESS)
            // Mask `msgSender` to the lower 160 bits, in case the upper bits somehow aren't clean.
            msgSender := and(msgSender, BITMASK_ADDRESS)
            // `msgSender == from || msgSender == approvedAddress`.
            result := or(eq(msgSender, from), eq(msgSender, approvedAddress))
        }
    }

    /**
     * @dev Transfers `tokenId` from `from` to `to`.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public virtual override {
        uint256 prevOwnershipPacked = _packedOwnershipOf(tokenId);

        if (address(uint160(prevOwnershipPacked)) != from) revert TransferFromIncorrectOwner();

        (uint256 approvedAddressSlot, address approvedAddress) = _getApprovedAddress(tokenId);

        // The nested ifs save around 20+ gas over a compound boolean condition.
        if (!_isOwnerOrApproved(approvedAddress, from, _msgSenderERC721A()))
            if (!isApprovedForAll(from, _msgSenderERC721A())) revert TransferCallerNotOwnerNorApproved();

        if (to == address(0)) revert TransferToZeroAddress();

        _beforeTokenTransfers(from, to, tokenId, 1);

        // Clear approvals from the previous owner.
        assembly {
            if approvedAddress {
                // This is equivalent to `delete _tokenApprovals[tokenId]`.
                sstore(approvedAddressSlot, 0)
            }
        }

        // Underflow of the sender's balance is impossible because we check for
        // ownership above and the recipient's balance can't realistically overflow.
        // Counter overflow is incredibly unrealistic as tokenId would have to be 2**256.
        unchecked {
            // We can directly increment and decrement the balances.
            --_packedAddressData[from]; // Updates: `balance -= 1`.
            ++_packedAddressData[to]; // Updates: `balance += 1`.

            // Updates:
            // - `address` to the next owner.
            // - `startTimestamp` to the timestamp of transfering.
            // - `burned` to `false`.
            // - `nextInitialized` to `true`.
            _packedOwnerships[tokenId] = _packOwnershipData(
                to,
                BITMASK_NEXT_INITIALIZED | _nextExtraData(from, to, prevOwnershipPacked)
            );

            // If the next slot may not have been initialized (i.e. `nextInitialized == false`) .
            if (prevOwnershipPacked & BITMASK_NEXT_INITIALIZED == 0) {
                uint256 nextTokenId = tokenId + 1;
                // If the next slot's address is zero and not burned (i.e. packed value is zero).
                if (_packedOwnerships[nextTokenId] == 0) {
                    // If the next slot is within bounds.
                    if (nextTokenId != _currentIndex) {
                        // Initialize the next slot to maintain correctness for `ownerOf(tokenId + 1)`.
                        _packedOwnerships[nextTokenId] = prevOwnershipPacked;
                    }
                }
            }
        }

        emit Transfer(from, to, tokenId);
        _afterTokenTransfers(from, to, tokenId, 1);
    }

    /**
     * @dev Equivalent to `_burn(tokenId, false)`.
     */
    function _burn(uint256 tokenId) internal virtual {
        _burn(tokenId, false);
    }

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

        address from = address(uint160(prevOwnershipPacked));

        (uint256 approvedAddressSlot, address approvedAddress) = _getApprovedAddress(tokenId);

        if (approvalCheck) {
            // The nested ifs save around 20+ gas over a compound boolean condition.
            if (!_isOwnerOrApproved(approvedAddress, from, _msgSenderERC721A()))
                if (!isApprovedForAll(from, _msgSenderERC721A())) revert TransferCallerNotOwnerNorApproved();
        }

        _beforeTokenTransfers(from, address(0), tokenId, 1);

        // Clear approvals from the previous owner.
        assembly {
            if approvedAddress {
                // This is equivalent to `delete _tokenApprovals[tokenId]`.
                sstore(approvedAddressSlot, 0)
            }
        }

        // Underflow of the sender's balance is impossible because we check for
        // ownership above and the recipient's balance can't realistically overflow.
        // Counter overflow is incredibly unrealistic as `tokenId` would have to be 2**256.
        unchecked {
            // Updates:
            // - `balance -= 1`.
            // - `numberBurned += 1`.
            //
            // We can directly decrement the balance, and increment the number burned.
            // This is equivalent to `packed -= 1; packed += 1 << BITPOS_NUMBER_BURNED;`.
            _packedAddressData[from] += (1 << BITPOS_NUMBER_BURNED) - 1;

            // Updates:
            // - `address` to the last owner.
            // - `startTimestamp` to the timestamp of burning.
            // - `burned` to `true`.
            // - `nextInitialized` to `true`.
            _packedOwnerships[tokenId] = _packOwnershipData(
                from,
                (BITMASK_BURNED | BITMASK_NEXT_INITIALIZED) | _nextExtraData(from, address(0), prevOwnershipPacked)
            );

            // If the next slot may not have been initialized (i.e. `nextInitialized == false`) .
            if (prevOwnershipPacked & BITMASK_NEXT_INITIALIZED == 0) {
                uint256 nextTokenId = tokenId + 1;
                // If the next slot's address is zero and not burned (i.e. packed value is zero).
                if (_packedOwnerships[nextTokenId] == 0) {
                    // If the next slot is within bounds.
                    if (nextTokenId != _currentIndex) {
                        // Initialize the next slot to maintain correctness for `ownerOf(tokenId + 1)`.
                        _packedOwnerships[nextTokenId] = prevOwnershipPacked;
                    }
                }
            }
        }

        emit Transfer(from, address(0), tokenId);
        _afterTokenTransfers(from, address(0), tokenId, 1);

        // Overflow not possible, as _burnCounter cannot be exceed _currentIndex times.
        unchecked {
            _burnCounter++;
        }
    }

    /**
     * @dev Internal function to invoke {IERC721Receiver-onERC721Received} on a target 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 _checkContractOnERC721Received(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
    ) private returns (bool) {
        try ERC721A__IERC721Receiver(to).onERC721Received(_msgSenderERC721A(), from, tokenId, _data) returns (
            bytes4 retval
        ) {
            return retval == ERC721A__IERC721Receiver(to).onERC721Received.selector;
        } catch (bytes memory reason) {
            if (reason.length == 0) {
                revert TransferToNonERC721ReceiverImplementer();
            } else {
                assembly {
                    revert(add(32, reason), mload(reason))
                }
            }
        }
    }

    /**
     * @dev Directly sets the extra data for the ownership data `index`.
     */
    function _setExtraDataAt(uint256 index, uint24 extraData) internal {
        uint256 packed = _packedOwnerships[index];
        if (packed == 0) revert OwnershipNotInitializedForExtraData();
        uint256 extraDataCasted;
        // Cast `extraData` with assembly to avoid redundant masking.
        assembly {
            extraDataCasted := extraData
        }
        packed = (packed & BITMASK_EXTRA_DATA_COMPLEMENT) | (extraDataCasted << BITPOS_EXTRA_DATA);
        _packedOwnerships[index] = packed;
    }

    /**
     * @dev Returns the next extra data for the packed ownership data.
     * The returned result is shifted into position.
     */
    function _nextExtraData(
        address from,
        address to,
        uint256 prevOwnershipPacked
    ) private view returns (uint256) {
        uint24 extraData = uint24(prevOwnershipPacked >> BITPOS_EXTRA_DATA);
        return uint256(_extraData(from, to, extraData)) << BITPOS_EXTRA_DATA;
    }

    /**
     * @dev Called during each token transfer to set the 24bit `extraData` field.
     * Intended to be overridden by the cosumer contract.
     *
     * `previousExtraData` - the value of `extraData` before transfer.
     *
     * 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, `tokenId` will be burned by `from`.
     * - `from` and `to` are never both zero.
     */
    function _extraData(
        address from,
        address to,
        uint24 previousExtraData
    ) internal view virtual returns (uint24) {}

    /**
     * @dev Hook that is called before a set of serially-ordered token ids are about to be transferred.
     * This includes minting.
     * And also called before burning one token.
     *
     * startTokenId - the first token id to be transferred
     * quantity - the amount to be transferred
     *
     * 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, `tokenId` will be burned by `from`.
     * - `from` and `to` are never both zero.
     */
    function _beforeTokenTransfers(
        address from,
        address to,
        uint256 startTokenId,
        uint256 quantity
    ) internal virtual {}

    /**
     * @dev Hook that is called after a set of serially-ordered token ids have been transferred.
     * This includes minting.
     * And also called after one token has been burned.
     *
     * startTokenId - the first token id to be transferred
     * quantity - the amount to be transferred
     *
     * Calling conditions:
     *
     * - When `from` and `to` are both non-zero, `from`'s `tokenId` has been
     * transferred to `to`.
     * - When `from` is zero, `tokenId` has been minted for `to`.
     * - When `to` is zero, `tokenId` has been burned by `from`.
     * - `from` and `to` are never both zero.
     */
    function _afterTokenTransfers(
        address from,
        address to,
        uint256 startTokenId,
        uint256 quantity
    ) internal virtual {}

    /**
     * @dev Returns the message sender (defaults to `msg.sender`).
     *
     * If you are writing GSN compatible contracts, you need to override this function.
     */
    function _msgSenderERC721A() internal view virtual returns (address) {
        return msg.sender;
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` decimal representation.
     */
    function _toString(uint256 value) internal pure returns (string memory ptr) {
        assembly {
            // The maximum value of a uint256 contains 78 digits (1 byte per digit),
            // but we allocate 128 bytes to keep the free memory pointer 32-byte word aliged.
            // We will need 1 32-byte word to store the length,
            // and 3 32-byte words to store a maximum of 78 digits. Total: 32 + 3 * 32 = 128.
            ptr := add(mload(0x40), 128)
            // Update the free memory pointer to allocate.
            mstore(0x40, ptr)

            // Cache the end of the memory to calculate the length later.
            let end := ptr

            // We write the string from the rightmost digit to the leftmost digit.
            // The following is essentially a do-while loop that also handles the zero case.
            // Costs a bit more than early returning for the zero case,
            // but cheaper in terms of deployment and overall runtime costs.
            for {
                // Initialize and perform the first pass without check.
                let temp := value
                // Move the pointer 1 byte leftwards to point to an empty character slot.
                ptr := sub(ptr, 1)
                // Write the character to the pointer. 48 is the ASCII index of '0'.
                mstore8(ptr, add(48, mod(temp, 10)))
                temp := div(temp, 10)
            } temp {
                // Keep dividing `temp` until zero.
                temp := div(temp, 10)
            } {
                // Body of the for loop.
                ptr := sub(ptr, 1)
                mstore8(ptr, add(48, mod(temp, 10)))
            }

            let length := sub(end, ptr)
            // Move the pointer 32 bytes leftwards to make room for the length.
            ptr := sub(ptr, 32)
            // Store the length.
            mstore(ptr, length)
        }
    }
}


///////////////////////////////////////////
// File: erc721a/contracts/IERC721A.sol

// SPDX-License-Identifier: MIT
// ERC721A Contracts v4.1.0
// Creator: Chiru Labs

pragma solidity ^0.8.4;

/**
 * @dev Interface of an ERC721A compliant contract.
 */
interface IERC721A {
    /**
     * The caller must own the token or be an approved operator.
     */
    error ApprovalCallerNotOwnerNorApproved();

    /**
     * The token does not exist.
     */
    error ApprovalQueryForNonexistentToken();

    /**
     * The caller cannot approve to their own address.
     */
    error ApproveToCaller();

    /**
     * Cannot query the balance for the zero address.
     */
    error BalanceQueryForZeroAddress();

    /**
     * Cannot mint to the zero address.
     */
    error MintToZeroAddress();

    /**
     * The quantity of tokens minted must be more than zero.
     */
    error MintZeroQuantity();

    /**
     * The token does not exist.
     */
    error OwnerQueryForNonexistentToken();

    /**
     * The caller must own the token or be an approved operator.
     */
    error TransferCallerNotOwnerNorApproved();

    /**
     * The token must be owned by `from`.
     */
    error TransferFromIncorrectOwner();

    /**
     * Cannot safely transfer to a contract that does not implement the ERC721Receiver interface.
     */
    error TransferToNonERC721ReceiverImplementer();

    /**
     * Cannot transfer to the zero address.
     */
    error TransferToZeroAddress();

    /**
     * The token does not exist.
     */
    error URIQueryForNonexistentToken();

    /**
     * The `quantity` minted with ERC2309 exceeds the safety limit.
     */
    error MintERC2309QuantityExceedsLimit();

    /**
     * The `extraData` cannot be set on an unintialized ownership slot.
     */
    error OwnershipNotInitializedForExtraData();

    struct TokenOwnership {
        // The address of the owner.
        address addr;
        // Keeps track of the start time of ownership with minimal overhead for tokenomics.
        uint64 startTimestamp;
        // Whether the token has been burned.
        bool burned;
        // Arbitrary data similar to `startTimestamp` that can be set through `_extraData`.
        uint24 extraData;
    }

    /**
     * @dev Returns the total amount of tokens stored by the contract.
     *
     * Burned tokens are calculated here, use `_totalMinted()` if you want to count just minted tokens.
     */
    function totalSupply() external view returns (uint256);

    // ==============================
    //            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);

    // ==============================
    //            IERC721
    // ==============================

    /**
     * @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`.
     *
     * 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;

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

    /**
     * @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);

    // ==============================
    //        IERC721Metadata
    // ==============================

    /**
     * @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);

    // ==============================
    //            IERC2309
    // ==============================

    /**
     * @dev Emitted when tokens in `fromTokenId` to `toTokenId` (inclusive) is transferred from `from` to `to`,
     * as defined in the ERC2309 standard. See `_mintERC2309` for more details.
     */
    event ConsecutiveTransfer(uint256 indexed fromTokenId, uint256 toTokenId, address indexed from, address indexed to);
}