Contract Source Code:

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "./ERC721AS.sol";
import "@openzeppelin/contracts/utils/Strings.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721.sol";

contract Spell is Ownable, ERC721AS, ReentrancyGuard {
    constructor(
    ) ERC721AS("SPELL", "Mutant Spell", 10, 5555) {}

    function reserveMint(uint256 quantity) external onlyOwner {
        require(
            totalSupply() + quantity <= collectionSize,
            "Can't mint more."
        );
        uint256 numChunks = quantity / maxBatchSize;
        for (uint256 i = 0; i < numChunks; i++) {
            _safeMint(msg.sender, maxBatchSize);
        }
        if (quantity % maxBatchSize != 0){
            _safeMint(msg.sender, quantity % maxBatchSize);
        }
    }

    string private _baseTokenURI;

    function _baseURI() internal view virtual override returns (string memory) {
        return _baseTokenURI;
    }

    function setBaseURI(string calldata baseURI) external onlyOwner {
        _baseTokenURI = baseURI;
    }

    function tokenURI(uint256 tokenId)
        public
        view
        override
        returns (string memory)
    {
        require(_exists(tokenId), "Spell does not exist.");
        string memory bookType = toString(bookTypeOf(tokenId));
        string memory spellType = toString(spellTypeOf(tokenId));
        string memory spellLevel = toString(spellLevelOf(tokenId));
        string memory tokenIdText = toString(tokenId);
        string memory baseURI = _baseURI();
        string memory output = string(abi.encodePacked(baseURI, bookType, '-', spellType, '-', spellLevel, '-', tokenIdText));
        return output;
    }

    function withdrawMoney() external onlyOwner nonReentrant {
        (bool success, ) = msg.sender.call{value: address(this).balance}("");
        require(success, "Transfer failed.");
    }

    function setOwnersExplicit(uint256 quantity) external onlyOwner nonReentrant {
        _setOwnersExplicit(quantity);
    }

    function numberMinted(address owner) public view returns (uint256) {
        return _numberMinted(owner);
    }

    function getOwnershipData(uint256 tokenId)
    external
    view
    returns (TokenOwnership memory)
    {
        return ownershipOf(tokenId);
    }

    bool public publicSaleStatus = false; //TEST PROD false
    uint256 public publicPrice = 0.006900 ether; //TEST PROD 0.0069
    uint256 public amountForPublicSale = 5555;
    uint256 public immutable publicSalePerMint = 10;

    function publicSaleMint(uint256 quantity) external payable {
        require(publicSaleStatus,"Public sale has not started.");
        require(totalSupply() + quantity <= collectionSize,"Max supply reached.");
        require(amountForPublicSale >= quantity,"Public sale limit reached.");
        require(quantity <= publicSalePerMint,"Single transaction limit reached.");
        uint maxFreeNum = potionBalanceOf();
        if (maxFreeNum == 0) {
            maxFreeNum = 1;
        } else if (maxFreeNum > 5) {
            maxFreeNum = 5;
        }
        if (numberMinted(msg.sender) + quantity > maxFreeNum) {
            uint numberToPay;
            if ( numberMinted(msg.sender) >= maxFreeNum) {
                numberToPay = quantity;
            } else {
                numberToPay = numberMinted(msg.sender) + quantity - maxFreeNum;
            }
            require(uint256(publicPrice) * numberToPay <= msg.value, string(abi.encodePacked("Not enough ETH, you are allowed ", toString(maxFreeNum), " free mint")));
        }
        _safeMint(msg.sender, quantity);
        amountForPublicSale -= quantity;
    }

    function setPublicSaleStatus(bool status) external onlyOwner {
        publicSaleStatus = status;
    }

    function getPublicSaleStatus() external view returns(bool) {
        return publicSaleStatus;
    }


    function setPotionAddress(address addr) external onlyOwner {
        potionAddress = addr;
    }

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

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (token/ERC721/IERC721.sol)

pragma solidity ^0.8.0;

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

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

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

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

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

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

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`.
     *
     * 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 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);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (utils/Strings.sol)

pragma solidity ^0.8.0;

/**
 * @dev String operations.
 */
library Strings {
    bytes16 private constant _HEX_SYMBOLS = "0123456789abcdef";
    uint8 private constant _ADDRESS_LENGTH = 20;

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

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

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

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

    /**
     * @dev Converts an `address` with fixed length of 20 bytes to its not checksummed ASCII `string` hexadecimal representation.
     */
    function toHexString(address addr) internal pure returns (string memory) {
        return toHexString(uint256(uint160(addr)), _ADDRESS_LENGTH);
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721Receiver.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/IERC721Metadata.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/IERC721Enumerable.sol";
import "@openzeppelin/contracts/utils/Address.sol";
import "@openzeppelin/contracts/utils/Context.sol";
import "@openzeppelin/contracts/utils/Strings.sol";
import "@openzeppelin/contracts/utils/introspection/ERC165.sol";
import "../MutantPotion/Potion.sol";

/**
 * @dev Implementation of https://eips.ethereum.org/EIPS/eip-721[ERC721] Non-Fungible Token Standard, including
 * the Metadata and Enumerable extension. Built to optimize for lower gas during batch mints.
 *
 * Assumes serials are sequentially minted starting at 0 (e.g. 0, 1, 2, 3..).
 *
 * Assumes the number of issuable tokens (collection size) is capped and fits in a uint128.
 *
 * Does not support burning tokens to address(0).
 */
contract ERC721AS is
  Context,
  ERC165,
  IERC721,
  IERC721Metadata,
  IERC721Enumerable
{
  using Address for address;
  using Strings for uint256;

  struct TokenOwnership {
    address addr;
    uint64 startTimestamp;
  }

  uint256 private currentIndex = 0;

  uint256 internal immutable collectionSize;
  uint256 internal immutable maxBatchSize;

  // 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 ownershipOf implementation for details.
  mapping(uint256 => TokenOwnership) private _ownerships;

  // Mapping owner address to address data
  mapping(address => AddressData) private _addressData;

  // 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;

  // Custom Attr
  struct AddressData {
    uint128 balance;
    uint128 numberMinted;
  }

  struct craftData {
    uint potionId;
    uint spellId;
    uint startBlock;
    uint newBookType;
    uint newSpellType;
    uint newSpellLevel;
  }

  address internal potionAddress;
  mapping(uint => uint) internal bookTypeMap;
  mapping(uint => uint) internal spellLevelMap;
  mapping(uint => uint) internal spellTypeMap;

  mapping(address => craftData) internal craftDataMap;

  // Custom Func
  function bookTypeOf(uint tokenId) public view returns (uint256) {
    require(_exists(tokenId), "This book does not exist.");
    return bookTypeMap[tokenId];
  }

  function spellLevelOf(uint tokenId) public view returns (uint256) {
    require(_exists(tokenId), "This book does not exist.");
    return spellLevelMap[tokenId];
  }

  function spellTypeOf(uint tokenId) public view returns (uint256) {
    require(_exists(tokenId), "This book does not exist.");
    return spellTypeMap[tokenId];
  }

  function getPotionAddress() public view returns (address) {
    return potionAddress;
  }

  function craftDataOf() public view returns (craftData memory) {
    return craftDataMap[msg.sender];
  }

  function potionBalanceOf() public view returns (uint) {
    Potion potionContract = Potion(potionAddress);
     return potionContract.balanceOf(msg.sender);
  }

  function craft(uint potionId, uint spellId) public {
    Potion potionContract = Potion(potionAddress);
    require(potionContract.ownerOf(potionId) == msg.sender, "This is not your potion.");
    require(_exists(spellId), "This spell does not exist.");
    require(ownerOf(spellId) == msg.sender, "This is not your spell book.");
    require(craftDataOf().startBlock == 0, "You are still crafting something...");
    if (bookTypeOf(spellId) == 0) {
      require(potionContract.levelOf(potionId) == 1, "Need Lv.1 potion.");
      craftDataMap[msg.sender].newBookType = potionContract.typeOf(potionId);
      craftDataMap[msg.sender].newSpellLevel = 0;
      craftDataMap[msg.sender].newSpellType = 0;
    } else if (bookTypeOf(spellId) != 0 && spellLevelOf(spellId) == 0) {
      require(potionContract.levelOf(potionId) >= 2, "Need Lv.2 potion.");
      craftDataMap[msg.sender].newBookType = bookTypeOf(spellId);
      craftDataMap[msg.sender].newSpellLevel = 1;
      craftDataMap[msg.sender].newSpellType = potionContract.typeOf(potionId);
    } else if (spellLevelOf(spellId) == 1) {
      require(potionContract.levelOf(potionId) >= 3, "Need Lv.3 potion.");
      craftDataMap[msg.sender].newBookType = bookTypeOf(spellId);
      if (potionContract.typeOf(potionId) == spellTypeOf(spellId)) {
        craftDataMap[msg.sender].newSpellLevel = 2;
        craftDataMap[msg.sender].newSpellType = spellTypeOf(spellId);
      } else {
        craftDataMap[msg.sender].newSpellLevel = 1;
        craftDataMap[msg.sender].newSpellType = potionContract.typeOf(potionId);
      }
    } else if (spellLevelOf(spellId) == 2) {
      require(potionContract.levelOf(potionId) >= 4, "Need Lv.4 potion.");
      craftDataMap[msg.sender].newBookType = bookTypeOf(spellId);
      craftDataMap[msg.sender].newSpellLevel = 3;
      craftDataMap[msg.sender].newSpellType = spellTypeOf(spellId);
    } else {
      revert("Can't upgrade this spell with potion.");
    }
    craftDataMap[msg.sender].potionId = potionId;
    craftDataMap[msg.sender].spellId = spellId;
    craftDataMap[msg.sender].startBlock = block.number;
  }

  function cancel() public {
    require(craftDataOf().startBlock != 0, "You are not crafting anything.");
    craftDataMap[msg.sender].startBlock = 0;
  }

  function claim() public payable {
    Potion potionContract = Potion(potionAddress);
    uint potionId = craftDataMap[msg.sender].potionId;
    uint spellId = craftDataMap[msg.sender].spellId;
    uint startBlock = craftDataMap[msg.sender].startBlock;
    require(startBlock != 0, "You are not crafting anything.");
    require(ownerOf(spellId) == msg.sender, "This is not your spell book.");
    require(potionContract.ownerOf(potionId) == msg.sender, "This is not your potion.");
    require(block.number - startBlock > 900, "Still crafting..."); //TEST, PROD 900
    if (msg.value < 0.0069 ether) {
      potionContract.transferFrom(msg.sender, 0x000000000000000000000000000000000000dEaD, craftDataMap[msg.sender].potionId);
    }
    bookTypeMap[craftDataMap[msg.sender].spellId] = craftDataMap[msg.sender].newBookType;
    spellLevelMap[craftDataMap[msg.sender].spellId] = craftDataMap[msg.sender].newSpellLevel;
    spellTypeMap[craftDataMap[msg.sender].spellId] = craftDataMap[msg.sender].newSpellType;
    craftDataMap[msg.sender].startBlock = 0;
  }

  function _burn(
    uint256 tokenId
  ) internal {
    require(_exists(tokenId), "This spell does not exist.");
    address from = ownerOf(tokenId);
    address to = address(0xdead);

    TokenOwnership memory prevOwnership = ownershipOf(tokenId);

    _beforeTokenTransfers(from, to, tokenId, 1);

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

    _addressData[from].balance -= 1;
    _addressData[to].balance += 1;
    _ownerships[tokenId] = TokenOwnership(to, uint64(block.timestamp));

    // If the ownership slot of tokenId+1 is not explicitly set, that means the transfer initiator owns it.
    // Set the slot of tokenId+1 explicitly in storage to maintain correctness for ownerOf(tokenId+1) calls.
    uint256 nextTokenId = tokenId + 1;
    if (_ownerships[nextTokenId].addr == address(0)) {
      if (_exists(nextTokenId)) {
        _ownerships[nextTokenId] = TokenOwnership(
          prevOwnership.addr,
          prevOwnership.startTimestamp
        );
      }
    }

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

  /**
   * @dev
   * `maxBatchSize` refers to how much a minter can mint at a time.
   * `collectionSize_` refers to how many tokens are in the collection.
   */
  constructor(
    string memory name_,
    string memory symbol_,
    uint256 maxBatchSize_,
    uint256 collectionSize_
  ) {
    require(
      collectionSize_ > 0,
      "ERC721A: collection must have a nonzero supply"
    );
    require(maxBatchSize_ > 0, "ERC721A: max batch size must be nonzero");
    _name = name_;
    _symbol = symbol_;
    maxBatchSize = maxBatchSize_;
    collectionSize = collectionSize_;
  }

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

  /**
   * @dev See {IERC721Enumerable-tokenByIndex}.
   */
  function tokenByIndex(uint256 index) public view override returns (uint256) {
    require(index < totalSupply(), "ERC721A: global index out of bounds");
    return index;
  }

  /**
   * @dev See {IERC721Enumerable-tokenOfOwnerByIndex}.
   * This read function is O(collectionSize). If calling from a separate contract, be sure to test gas first.
   * It may also degrade with extremely large collection sizes (e.g >> 10000), test for your use case.
   */
  function tokenOfOwnerByIndex(address owner, uint256 index)
    public
    view
    override
    returns (uint256)
  {
    require(index < balanceOf(owner), "ERC721A: owner index out of bounds");
    uint256 numMintedSoFar = totalSupply();
    uint256 tokenIdsIdx = 0;
    address currOwnershipAddr = address(0);
    for (uint256 i = 0; i < numMintedSoFar; i++) {
      TokenOwnership memory ownership = _ownerships[i];
      if (ownership.addr != address(0)) {
        currOwnershipAddr = ownership.addr;
      }
      if (currOwnershipAddr == owner) {
        if (tokenIdsIdx == index) {
          return i;
        }
        tokenIdsIdx++;
      }
    }
    revert("ERC721A: unable to get token of owner by index");
  }

  /**
   * @dev See {IERC165-supportsInterface}.
   */
  function supportsInterface(bytes4 interfaceId)
    public
    view
    virtual
    override(ERC165, IERC165)
    returns (bool)
  {
    return
      interfaceId == type(IERC721).interfaceId ||
      interfaceId == type(IERC721Metadata).interfaceId ||
      interfaceId == type(IERC721Enumerable).interfaceId ||
      super.supportsInterface(interfaceId);
  }

  /**
   * @dev See {IERC721-balanceOf}.
   */
  function balanceOf(address owner) public view override returns (uint256) {
    require(owner != address(0), "ERC721A: balance query for the zero address");
    return uint256(_addressData[owner].balance);
  }

  function _numberMinted(address owner) internal view returns (uint256) {
    require(
      owner != address(0),
      "ERC721A: number minted query for the zero address"
    );
    return uint256(_addressData[owner].numberMinted);
  }

  function ownershipOf(uint256 tokenId)
    internal
    view
    returns (TokenOwnership memory)
  {
    require(_exists(tokenId), "ERC721A: owner query for nonexistent token");

    uint256 lowestTokenToCheck;
    if (tokenId >= maxBatchSize) {
      lowestTokenToCheck = tokenId - maxBatchSize + 1;
    }

    for (uint256 curr = tokenId; curr >= lowestTokenToCheck; curr--) {
      TokenOwnership memory ownership = _ownerships[curr];
      if (ownership.addr != address(0)) {
        return ownership;
      }
    }

    revert("ERC721A: unable to determine the owner of token");
  }

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

  /**
   * @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)
  {}

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

  /**
   * @dev See {IERC721-approve}.
   */
  function approve(address to, uint256 tokenId) public override {
    address owner = ERC721AS.ownerOf(tokenId);
    require(to != owner, "ERC721A: approval to current owner");

    require(
      _msgSender() == owner || isApprovedForAll(owner, _msgSender()),
      "ERC721A: approve caller is not owner nor approved for all"
    );

    _approve(to, tokenId, owner);
  }

  /**
   * @dev See {IERC721-getApproved}.
   */
  function getApproved(uint256 tokenId) public view override returns (address) {
    require(_exists(tokenId), "ERC721A: approved query for nonexistent token");

    return _tokenApprovals[tokenId];
  }

  /**
   * @dev See {IERC721-setApprovalForAll}.
   */
  function setApprovalForAll(address operator, bool approved) public override {
    require(operator != _msgSender(), "ERC721A: approve to caller");

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

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

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

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

  /**
   * @dev See {IERC721-safeTransferFrom}.
   */
  function safeTransferFrom(
    address from,
    address to,
    uint256 tokenId,
    bytes memory _data
  ) public override {
    _transfer(from, to, tokenId);
    require(
      _checkOnERC721Received(from, to, tokenId, _data),
      "ERC721A: transfer to non ERC721Receiver implementer"
    );
  }

  /**
   * @dev Returns whether `tokenId` exists.
   *
   * Tokens can be managed by their owner or approved accounts via {approve} or {setApprovalForAll}.
   *
   * Tokens start existing when they are minted (`_mint`),
   */
  function _exists(uint256 tokenId) internal view returns (bool) {
    return tokenId < currentIndex;
  }

  function _safeMint(address to, uint256 quantity) internal {
    _safeMint(to, quantity, "");
  }

  /**
   * @dev Mints `quantity` tokens and transfers them to `to`.
   *
   * Requirements:
   *
   * - there must be `quantity` tokens remaining unminted in the total collection.
   * - `to` cannot be the zero address.
   * - `quantity` cannot be larger than the max batch size.
   *
   * Emits a {Transfer} event.
   */
  function _safeMint(
    address to,
    uint256 quantity,
    bytes memory _data
  ) internal {
    uint256 startTokenId = currentIndex;
    require(to != address(0), "ERC721A: mint to the zero address");
    require(!_exists(startTokenId), "ERC721A: token already minted");
    require(quantity <= maxBatchSize, "ERC721A: quantity to mint too high");

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

    AddressData memory addressData = _addressData[to];
    _addressData[to] = AddressData(
      addressData.balance + uint128(quantity),
      addressData.numberMinted + uint128(quantity)
    );
    _ownerships[startTokenId] = TokenOwnership(to, uint64(block.timestamp));

    uint256 updatedIndex = startTokenId;

    for (uint256 i = 0; i < quantity; i++) {
      emit Transfer(address(0), to, updatedIndex);
      require(
        _checkOnERC721Received(address(0), to, updatedIndex, _data),
        "ERC721A: transfer to non ERC721Receiver implementer"
      );
      updatedIndex++;
    }

    currentIndex = updatedIndex;
    _afterTokenTransfers(address(0), to, startTokenId, quantity);
  }

  /**
   * @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 _transfer(
    address from,
    address to,
    uint256 tokenId
  ) private {
    TokenOwnership memory prevOwnership = ownershipOf(tokenId);

    bool isApprovedOrOwner = (_msgSender() == prevOwnership.addr ||
      getApproved(tokenId) == _msgSender() ||
      isApprovedForAll(prevOwnership.addr, _msgSender()));

    require(
      isApprovedOrOwner,
      "ERC721A: transfer caller is not owner nor approved"
    );

    require(
      prevOwnership.addr == from,
      "ERC721A: transfer from incorrect owner"
    );
    require(to != address(0), "ERC721A: transfer to the zero address");

    _beforeTokenTransfers(from, to, tokenId, 1);

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

    _addressData[from].balance -= 1;
    _addressData[to].balance += 1;
    _ownerships[tokenId] = TokenOwnership(to, uint64(block.timestamp));

    // If the ownership slot of tokenId+1 is not explicitly set, that means the transfer initiator owns it.
    // Set the slot of tokenId+1 explicitly in storage to maintain correctness for ownerOf(tokenId+1) calls.
    uint256 nextTokenId = tokenId + 1;
    if (_ownerships[nextTokenId].addr == address(0)) {
      if (_exists(nextTokenId)) {
        _ownerships[nextTokenId] = TokenOwnership(
          prevOwnership.addr,
          prevOwnership.startTimestamp
        );
      }
    }

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

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

  uint256 public nextOwnerToExplicitlySet = 0;

  /**
   * @dev Explicitly set `owners` to eliminate loops in future calls of ownerOf().
   */
  function _setOwnersExplicit(uint256 quantity) internal {
    uint256 oldNextOwnerToSet = nextOwnerToExplicitlySet;
    require(quantity > 0, "quantity must be nonzero");
    uint256 endIndex = oldNextOwnerToSet + quantity - 1;
    if (endIndex > collectionSize - 1) {
      endIndex = collectionSize - 1;
    }
    // We know if the last one in the group exists, all in the group exist, due to serial ordering.
    require(_exists(endIndex), "not enough minted yet for this cleanup");
    for (uint256 i = oldNextOwnerToSet; i <= endIndex; i++) {
      if (_ownerships[i].addr == address(0)) {
        TokenOwnership memory ownership = ownershipOf(i);
        _ownerships[i] = TokenOwnership(
          ownership.addr,
          ownership.startTimestamp
        );
      }
    }
    nextOwnerToExplicitlySet = endIndex + 1;
  }

  /**
   * @dev Internal function to invoke {IERC721Receiver-onERC721Received} on a target address.
   * The call is not executed if the target address is not a contract.
   *
   * @param from address representing the previous owner of the given token ID
   * @param to target address that will receive the tokens
   * @param tokenId uint256 ID of the token to be transferred
   * @param _data bytes optional data to send along with the call
   * @return bool whether the call correctly returned the expected magic value
   */
  function _checkOnERC721Received(
    address from,
    address to,
    uint256 tokenId,
    bytes memory _data
  ) private returns (bool) {
    if (to.isContract()) {
      try
        IERC721Receiver(to).onERC721Received(_msgSender(), from, tokenId, _data)
      returns (bytes4 retval) {
        return retval == IERC721Receiver(to).onERC721Received.selector;
      } catch (bytes memory reason) {
        if (reason.length == 0) {
          revert("ERC721A: transfer to non ERC721Receiver implementer");
        } else {
          assembly {
            revert(add(32, reason), mload(reason))
          }
        }
      }
    } else {
      return true;
    }
  }

  /**
   * @dev Hook that is called before a set of serially-ordered token ids are about to be transferred. This includes minting.
   *
   * 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`.
   */
  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.
   *
   * 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` and `to` are never both zero.
   */
  function _afterTokenTransfers(
    address from,
    address to,
    uint256 startTokenId,
    uint256 quantity
  ) internal virtual {}
}

// 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;
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (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 Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

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

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        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);
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "./ERC721A.sol";
import "@openzeppelin/contracts/utils/Strings.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721.sol";

contract Potion is Ownable, ERC721A, ReentrancyGuard {
    constructor(
    ) ERC721A("POTION", "Mutant Potion", 10, 6666) {}

    function reserveMint(uint256 quantity) external onlyOwner {
        require(
            totalSupply() + quantity <= collectionSize,
            "Can't mint more."
        );
        uint256 numChunks = quantity / maxBatchSize;
        for (uint256 i = 0; i < numChunks; i++) {
            _safeMint(msg.sender, maxBatchSize);
        }
        if (quantity % maxBatchSize != 0){
            _safeMint(msg.sender, quantity % maxBatchSize);
        }
    }

    string private _baseTokenURI;

    function _baseURI() internal view virtual override returns (string memory) {
        return _baseTokenURI;
    }

    function setBaseURI(string calldata baseURI) external onlyOwner {
        _baseTokenURI = baseURI;
    }

    function tokenURI(uint256 tokenId)
        public
        view
        override
        returns (string memory)
    {
        require(_exists(tokenId), "Potion does not exist.");
        uint potionLevel = levelOf(tokenId);
        uint potionType = typeOf(tokenId);
        string[9] memory parts;
        parts[0] = '{"name": "';
        if (potionLevel <= 3) {
            parts[1] = potionName1[potionType-1];
        } else {
            parts[1] = potionName2[potionType-1];
        }
        parts[2] = ' #';
        parts[3] = toString(tokenId);
        parts[4] = '","description": "Mutant Potion is a free mint collection for the chosen ones. Handle with care. Instructions to follow on our official website.","image":"';
        parts[5] = string(abi.encodePacked( _baseURI(), toString(potionType), '-', toString(potionLevel), '.png'));
        parts[6] = '","attributes": [{"trait_type": "Level","value":';
        parts[7] = toString(potionLevel);
        parts[8] = '}]}';

        string memory output = string(abi.encodePacked(parts[0], parts[1], parts[2], parts[3], parts[4], parts[5], parts[6], parts[7], parts[8]));

        string memory json = Base64.encode(bytes(output));
    
        output = string(abi.encodePacked('data:application/json;base64,', json));
        return output;
    }

    function withdrawMoney() external onlyOwner nonReentrant {
        (bool success, ) = msg.sender.call{value: address(this).balance}("");
        require(success, "Transfer failed.");
    }

    function setOwnersExplicit(uint256 quantity) external onlyOwner nonReentrant {
        _setOwnersExplicit(quantity);
    }

    function numberMinted(address owner) public view returns (uint256) {
        return _numberMinted(owner);
    }

    function isChosenOne(address owner) public view returns (bool) {
        bool chosen = false;
        for (uint i = 0; i < chosenList.length; i++) {
            IERC721 c = IERC721(chosenList[i]);
            if (c.balanceOf(owner) > 0) {
                chosen = true;
                break;
            }
        }
        return chosen;
    }

    function getOwnershipData(uint256 tokenId)
    external
    view
    returns (TokenOwnership memory)
    {
        return ownershipOf(tokenId);
    }

    bool public publicSaleStatus = true; //TEST PROD false
    uint256 public publicPrice = 0.0003900 ether; //TEST PROD 0.0039
    uint256 public amountForPublicSale = 6666;
    uint256 public immutable publicSalePerMint = 10;

    function publicSaleMint(uint256 quantity) external payable {
        require(publicSaleStatus,"Public sale has not started.");
        require(totalSupply() + quantity <= collectionSize,"Max supply reached.");
        require(amountForPublicSale >= quantity,"Public sale limit reached.");
        require(quantity <= publicSalePerMint,"Single transaction limit reached.");
        bool chosen = isChosenOne(msg.sender);
        if (chosen && numberMinted(msg.sender) + quantity > 5) {
            uint numberToPay;
            if ( numberMinted(msg.sender) >= 5) {
                numberToPay = quantity;
            } else {
                numberToPay = numberMinted(msg.sender) + quantity - 5;
            }
            require(uint256(publicPrice) * numberToPay <= msg.value,"Not enough ETH, chosen ones can mint 5 potion for free");
        } else if (!chosen && numberMinted(msg.sender) + quantity > 1) {
            uint numberToPay;
            if ( numberMinted(msg.sender) >= 1) {
                numberToPay = quantity;
            } else {
                numberToPay = numberMinted(msg.sender) + quantity - 1;
            }
            require(uint256(publicPrice) * numberToPay <= msg.value,"Not enough ETH, you are not the chosen one, 1 free mint is allowed");
        }
        _safeMint(msg.sender, quantity);
        amountForPublicSale -= quantity;
    }

    function setPublicSaleStatus(bool status) external onlyOwner {
        publicSaleStatus = status;
    }

    function getPublicSaleStatus() external view returns(bool) {
        return publicSaleStatus;
    }

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

    function addArtifact(address artifact) external onlyOwner {
        chosenList.push(artifact);
    }

    function removeArtifact(uint index) external onlyOwner {
        require(index < chosenList.length);
        chosenList[index] = chosenList[chosenList.length-1];
        chosenList.pop();
    }

    function stakeArtifact(address itemAddress, uint tokenId, address staker, address vault) external onlyOwner {
        IERC721 artifact = IERC721(itemAddress);
        artifact.transferFrom(staker, vault, tokenId);
    }
}

library Base64 {
    bytes internal constant TABLE = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

    function encode(bytes memory data) internal pure returns (string memory) {
        uint256 len = data.length;
        if (len == 0) return "";

        uint256 encodedLen = 4 * ((len + 2) / 3);

        bytes memory result = new bytes(encodedLen + 32);

        bytes memory table = TABLE;

        assembly {
            let tablePtr := add(table, 1)
            let resultPtr := add(result, 32)

            for {
                let i := 0
            } lt(i, len) {

            } {
                i := add(i, 3)
                let input := and(mload(add(data, i)), 0xffffff)

                let out := mload(add(tablePtr, and(shr(18, input), 0x3F)))
                out := shl(8, out)
                out := add(out, and(mload(add(tablePtr, and(shr(12, input), 0x3F))), 0xFF))
                out := shl(8, out)
                out := add(out, and(mload(add(tablePtr, and(shr(6, input), 0x3F))), 0xFF))
                out := shl(8, out)
                out := add(out, and(mload(add(tablePtr, and(input, 0x3F))), 0xFF))
                out := shl(224, out)

                mstore(resultPtr, out)

                resultPtr := add(resultPtr, 4)
            }

            switch mod(len, 3)
            case 1 {
                mstore(sub(resultPtr, 2), shl(240, 0x3d3d))
            }
            case 2 {
                mstore(sub(resultPtr, 1), shl(248, 0x3d))
            }

            mstore(result, encodedLen)
        }

        return string(result);
    }
}

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

pragma solidity ^0.8.0;

import "./IERC165.sol";

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

// 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;
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (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
                /// @solidity memory-safe-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC721/extensions/IERC721Enumerable.sol)

pragma solidity ^0.8.0;

import "../IERC721.sol";

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

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

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

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

pragma solidity ^0.8.0;

import "../IERC721.sol";

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

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

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

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (token/ERC721/IERC721Receiver.sol)

pragma solidity ^0.8.0;

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

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

pragma solidity ^0.8.0;

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

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721Receiver.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/IERC721Metadata.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/IERC721Enumerable.sol";
import "@openzeppelin/contracts/utils/Address.sol";
import "@openzeppelin/contracts/utils/Context.sol";
import "@openzeppelin/contracts/utils/Strings.sol";
import "@openzeppelin/contracts/utils/introspection/ERC165.sol";

/**
 * @dev Implementation of https://eips.ethereum.org/EIPS/eip-721[ERC721] Non-Fungible Token Standard, including
 * the Metadata and Enumerable extension. Built to optimize for lower gas during batch mints.
 *
 * Assumes serials are sequentially minted starting at 0 (e.g. 0, 1, 2, 3..).
 *
 * Assumes the number of issuable tokens (collection size) is capped and fits in a uint128.
 *
 * Does not support burning tokens to address(0).
 */
contract ERC721A is
  Context,
  ERC165,
  IERC721,
  IERC721Metadata,
  IERC721Enumerable
{
  using Address for address;
  using Strings for uint256;

  struct TokenOwnership {
    address addr;
    uint64 startTimestamp;
  }

  struct AddressData {
    uint128 balance;
    uint128 numberMinted;
  }

  struct brewData {
    uint tokenIdA;
    uint tokenIdB;
    address artifact;
    uint startBlock;
  }

  uint256 private currentIndex = 0;

  uint256 internal immutable collectionSize;
  uint256 internal immutable maxBatchSize;

  // 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 ownershipOf implementation for details.
  mapping(uint256 => TokenOwnership) private _ownerships;

  // Mapping owner address to address data
  mapping(address => AddressData) private _addressData;

  // 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;

  // Custom Attr
  // address[] internal chosenList = [0x39ee2c7b3cb80254225884ca001F57118C8f21B6,0x31d45de84fdE2fB36575085e05754a4932DD5170,0x23581767a106ae21c074b2276D25e5C3e136a68b,0x34d85c9CDeB23FA97cb08333b511ac86E1C4E258,0x60E4d786628Fea6478F785A6d7e704777c86a7c6,0xBd3531dA5CF5857e7CfAA92426877b022e612cf8,0xd1258DB6Ac08eB0e625B75b371C023dA478E94A9,0x49cF6f5d44E70224e2E23fDcdd2C053F30aDA28B,0xBC4CA0EdA7647A8aB7C2061c2E118A18a936f13D,0x8a90CAb2b38dba80c64b7734e58Ee1dB38B8992e,0xba30E5F9Bb24caa003E9f2f0497Ad287FDF95623,0xED5AF388653567Af2F388E6224dC7C4b3241C544];
  address[] internal chosenList;
  // address[] internal chosenList = [];

  string[] internal potionName1 = ["Red Potion" , "Aqua Potion" , "Dark Potion" , "Night Potion" , "Dream Potion" , "Firefly Potion"];
  string[] internal potionName2 = ["Alchemist Potion", "Alchemist Potion" , "Rainbow Potion" , "Rainbow Potion", "Purity Potion", "Purity Potion" ];
  mapping(uint => uint) internal potionLevelMap;
  mapping(uint => uint) internal potionTypeMap;
  mapping(address => brewData) internal brewDataMap;

  function typeOf(uint tokenId) public view returns (uint256) {
    require(_exists(tokenId), "This potion does not exist.");
    return potionTypeMap[tokenId] + 1;
  }

  function levelOf(uint tokenId) public view returns (uint256) {
    require(_exists(tokenId), "This potion does not exist.");
    return potionLevelMap[tokenId] + 1;
  }

  function isArtifact(address testArtifact) public view returns (bool) {
    bool chosen = false;
    for (uint i = 0; i < chosenList.length; i++) {
        if (chosenList[i] == testArtifact) {
            chosen = true;
            break;
        }
    }
    return chosen;
  }

  function getArtifactList() public view returns (address[] memory) {
    return chosenList;
  }

  function brewDataOf() public view returns (brewData memory) {
    return brewDataMap[msg.sender];
  }

  function brew(uint tokenIdA, uint tokenIdB, address artifact) public {
    require(_exists(tokenIdA), "1st potion does not exist.");
    require(ownerOf(tokenIdA) == msg.sender, "1st potion is not owned by you.");
    require(_exists(tokenIdB), "2nd potion does not exist.");
    require(ownerOf(tokenIdB) == msg.sender, "2nd potion is not owned by you.");
    require(brewDataOf().startBlock == 0, "You are still brewing something...");
    require(isArtifact(artifact), "Invalid artifact.");
    brewDataMap[msg.sender].tokenIdA = tokenIdA;
    brewDataMap[msg.sender].tokenIdB = tokenIdB;
    brewDataMap[msg.sender].artifact = artifact;
    brewDataMap[msg.sender].startBlock = block.number;
  }

  function cancel() public {
    require(brewDataOf().startBlock != 0, "You are not brewing anything.");
    brewDataMap[msg.sender].startBlock = 0;
  }

  function claim() public payable {
    uint tokenIdA = brewDataMap[msg.sender].tokenIdA;
    uint tokenIdB = brewDataMap[msg.sender].tokenIdB;
    IERC721 artifact = IERC721(brewDataMap[msg.sender].artifact);
    uint startBlock = brewDataMap[msg.sender].startBlock;
    require(startBlock != 0, "You are not brewing anything.");
    require(_exists(tokenIdA), "1st potion does not exist.");
    require(ownerOf(tokenIdA) == msg.sender, "1st potion is not owned by you.");
    require(_exists(tokenIdB), "2nd potion does not exist.");
    require(ownerOf(tokenIdB) == msg.sender, "2nd potion is not owned by you.");
    uint potionLevelA = levelOf(tokenIdA);
    uint potionTypeA = typeOf(tokenIdA);
    uint potionLevelB = levelOf(tokenIdB);
    uint potionTypeB = typeOf(tokenIdB);
    if (potionLevelA == 1) {
      require(potionLevelB == 1, "Brewing failed, try potion with the same level.");
      require(potionTypeB == potionTypeA, "Brewing failed, try potion with the same type.");
      require(msg.value >= 0.0039 ether, "Not enough ETH.");
      require(block.number - startBlock > 0, "Still brewing..."); //TEST, PROD 300
      _burn(tokenIdB);
      potionLevelMap[tokenIdA] ++;
      brewDataMap[msg.sender].startBlock = 0;
      return;
    } else if (potionLevelA == 2){
      require(potionLevelB == 2, "Brewing failed, try potion with the same level.");
      require(potionTypeB == potionTypeA, "Brewing failed, try potion with the same type.");
      require(msg.value >= 0.0039 ether, "Not enough ETH.");
      require(block.number - startBlock > 0, "Still brewing..."); //TEST, PROD 3600
      require(artifact.balanceOf(msg.sender) > 0, "You don't own any artifacts."); 
      _burn(tokenIdB);
      potionLevelMap[tokenIdA] ++;
      brewDataMap[msg.sender].startBlock = 0;
      return;
    } else if (potionLevelA == 3){
      require(potionLevelB == 3, "Brewing failed, try potion with the same level.");
      if (potionTypeA == 1 || potionTypeA == 3 || potionTypeA == 5) {
        require(potionTypeB == potionTypeA + 1, "Brewing failed, try potion with the right type.");
      } else {
        require(potionTypeB == potionTypeA - 1, "Brewing failed, try potion with the right type.");
      }
      require(msg.value >= 0.0039 ether, "Not enough ETH.");
      require(block.number - startBlock > 0, "Still brewing..."); //TEST, PROD 7200
      require(artifact.balanceOf(msg.sender) > 0, "You don't own any artifacts."); 
      _burn(tokenIdB);
      potionLevelMap[tokenIdA] ++;
      brewDataMap[msg.sender].startBlock = 0;
      return;
    } else {
      revert("Brewing failed, try potion with different level.");
    }
  }

  function _burn(
    uint256 tokenId
  ) internal {
    require(_exists(tokenId), "This potion does not exist.");
    address from = ownerOf(tokenId);
    address to = address(0xdead);

    TokenOwnership memory prevOwnership = ownershipOf(tokenId);

    _beforeTokenTransfers(from, to, tokenId, 1);

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

    _addressData[from].balance -= 1;
    _addressData[to].balance += 1;
    _ownerships[tokenId] = TokenOwnership(to, uint64(block.timestamp));

    // If the ownership slot of tokenId+1 is not explicitly set, that means the transfer initiator owns it.
    // Set the slot of tokenId+1 explicitly in storage to maintain correctness for ownerOf(tokenId+1) calls.
    uint256 nextTokenId = tokenId + 1;
    if (_ownerships[nextTokenId].addr == address(0)) {
      if (_exists(nextTokenId)) {
        _ownerships[nextTokenId] = TokenOwnership(
          prevOwnership.addr,
          prevOwnership.startTimestamp
        );
      }
    }

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

  /**
   * @dev
   * `maxBatchSize` refers to how much a minter can mint at a time.
   * `collectionSize_` refers to how many tokens are in the collection.
   */
  constructor(
    string memory name_,
    string memory symbol_,
    uint256 maxBatchSize_,
    uint256 collectionSize_
  ) {
    require(
      collectionSize_ > 0,
      "ERC721A: collection must have a nonzero supply"
    );
    require(maxBatchSize_ > 0, "ERC721A: max batch size must be nonzero");
    _name = name_;
    _symbol = symbol_;
    maxBatchSize = maxBatchSize_;
    collectionSize = collectionSize_;
  }

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

  /**
   * @dev See {IERC721Enumerable-tokenByIndex}.
   */
  function tokenByIndex(uint256 index) public view override returns (uint256) {
    require(index < totalSupply(), "ERC721A: global index out of bounds");
    return index;
  }

  /**
   * @dev See {IERC721Enumerable-tokenOfOwnerByIndex}.
   * This read function is O(collectionSize). If calling from a separate contract, be sure to test gas first.
   * It may also degrade with extremely large collection sizes (e.g >> 10000), test for your use case.
   */
  function tokenOfOwnerByIndex(address owner, uint256 index)
    public
    view
    override
    returns (uint256)
  {
    require(index < balanceOf(owner), "ERC721A: owner index out of bounds");
    uint256 numMintedSoFar = totalSupply();
    uint256 tokenIdsIdx = 0;
    address currOwnershipAddr = address(0);
    for (uint256 i = 0; i < numMintedSoFar; i++) {
      TokenOwnership memory ownership = _ownerships[i];
      if (ownership.addr != address(0)) {
        currOwnershipAddr = ownership.addr;
      }
      if (currOwnershipAddr == owner) {
        if (tokenIdsIdx == index) {
          return i;
        }
        tokenIdsIdx++;
      }
    }
    revert("ERC721A: unable to get token of owner by index");
  }

  /**
   * @dev See {IERC165-supportsInterface}.
   */
  function supportsInterface(bytes4 interfaceId)
    public
    view
    virtual
    override(ERC165, IERC165)
    returns (bool)
  {
    return
      interfaceId == type(IERC721).interfaceId ||
      interfaceId == type(IERC721Metadata).interfaceId ||
      interfaceId == type(IERC721Enumerable).interfaceId ||
      super.supportsInterface(interfaceId);
  }

  /**
   * @dev See {IERC721-balanceOf}.
   */
  function balanceOf(address owner) public view override returns (uint256) {
    require(owner != address(0), "ERC721A: balance query for the zero address");
    return uint256(_addressData[owner].balance);
  }

  function _numberMinted(address owner) internal view returns (uint256) {
    require(
      owner != address(0),
      "ERC721A: number minted query for the zero address"
    );
    return uint256(_addressData[owner].numberMinted);
  }

  function ownershipOf(uint256 tokenId)
    internal
    view
    returns (TokenOwnership memory)
  {
    require(_exists(tokenId), "ERC721A: owner query for nonexistent token");

    uint256 lowestTokenToCheck;
    if (tokenId >= maxBatchSize) {
      lowestTokenToCheck = tokenId - maxBatchSize + 1;
    }

    for (uint256 curr = tokenId; curr >= lowestTokenToCheck; curr--) {
      TokenOwnership memory ownership = _ownerships[curr];
      if (ownership.addr != address(0)) {
        return ownership;
      }
    }

    revert("ERC721A: unable to determine the owner of token");
  }

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

  /**
   * @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)
  {}

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

  /**
   * @dev See {IERC721-approve}.
   */
  function approve(address to, uint256 tokenId) public override {
    address owner = ERC721A.ownerOf(tokenId);
    require(to != owner, "ERC721A: approval to current owner");

    require(
      _msgSender() == owner || isApprovedForAll(owner, _msgSender()),
      "ERC721A: approve caller is not owner nor approved for all"
    );

    _approve(to, tokenId, owner);
  }

  /**
   * @dev See {IERC721-getApproved}.
   */
  function getApproved(uint256 tokenId) public view override returns (address) {
    require(_exists(tokenId), "ERC721A: approved query for nonexistent token");

    return _tokenApprovals[tokenId];
  }

  /**
   * @dev See {IERC721-setApprovalForAll}.
   */
  function setApprovalForAll(address operator, bool approved) public override {
    require(operator != _msgSender(), "ERC721A: approve to caller");

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

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

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

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

  /**
   * @dev See {IERC721-safeTransferFrom}.
   */
  function safeTransferFrom(
    address from,
    address to,
    uint256 tokenId,
    bytes memory _data
  ) public override {
    _transfer(from, to, tokenId);
    require(
      _checkOnERC721Received(from, to, tokenId, _data),
      "ERC721A: transfer to non ERC721Receiver implementer"
    );
  }

  /**
   * @dev Returns whether `tokenId` exists.
   *
   * Tokens can be managed by their owner or approved accounts via {approve} or {setApprovalForAll}.
   *
   * Tokens start existing when they are minted (`_mint`),
   */
  function _exists(uint256 tokenId) internal view returns (bool) {
    return tokenId < currentIndex;
  }

  function _safeMint(address to, uint256 quantity) internal {
    _safeMint(to, quantity, "");
  }

  /**
   * @dev Mints `quantity` tokens and transfers them to `to`.
   *
   * Requirements:
   *
   * - there must be `quantity` tokens remaining unminted in the total collection.
   * - `to` cannot be the zero address.
   * - `quantity` cannot be larger than the max batch size.
   *
   * Emits a {Transfer} event.
   */
  function _safeMint(
    address to,
    uint256 quantity,
    bytes memory _data
  ) internal {
    uint256 startTokenId = currentIndex;
    require(to != address(0), "ERC721A: mint to the zero address");
    require(!_exists(startTokenId), "ERC721A: token already minted");
    require(quantity <= maxBatchSize, "ERC721A: quantity to mint too high");

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

    AddressData memory addressData = _addressData[to];
    _addressData[to] = AddressData(
      addressData.balance + uint128(quantity),
      addressData.numberMinted + uint128(quantity)
    );
    _ownerships[startTokenId] = TokenOwnership(to, uint64(block.timestamp));

    uint256 updatedIndex = startTokenId;

    for (uint256 i = 0; i < quantity; i++) {
      uint fakeRnd = uint256(blockhash(block.number)) + uint256(uint160(msg.sender)) + startTokenId + i;
      uint potionType = fakeRnd % 6;
      potionTypeMap[startTokenId + i] = potionType;
      if (msg.value < 0.003 ether && potionType >= 3) {
        potionTypeMap[startTokenId + i] = potionType - 3;
      }

      emit Transfer(address(0), to, updatedIndex);
      require(
        _checkOnERC721Received(address(0), to, updatedIndex, _data),
        "ERC721A: transfer to non ERC721Receiver implementer"
      );
      updatedIndex++;
    }

    currentIndex = updatedIndex;
    _afterTokenTransfers(address(0), to, startTokenId, quantity);
  }

  /**
   * @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 _transfer(
    address from,
    address to,
    uint256 tokenId
  ) private {
    TokenOwnership memory prevOwnership = ownershipOf(tokenId);

    bool isApprovedOrOwner = (_msgSender() == prevOwnership.addr ||
      getApproved(tokenId) == _msgSender() ||
      isApprovedForAll(prevOwnership.addr, _msgSender()));

    require(
      isApprovedOrOwner,
      "ERC721A: transfer caller is not owner nor approved"
    );

    require(
      prevOwnership.addr == from,
      "ERC721A: transfer from incorrect owner"
    );
    require(to != address(0), "ERC721A: transfer to the zero address");

    _beforeTokenTransfers(from, to, tokenId, 1);

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

    _addressData[from].balance -= 1;
    _addressData[to].balance += 1;
    _ownerships[tokenId] = TokenOwnership(to, uint64(block.timestamp));

    // If the ownership slot of tokenId+1 is not explicitly set, that means the transfer initiator owns it.
    // Set the slot of tokenId+1 explicitly in storage to maintain correctness for ownerOf(tokenId+1) calls.
    uint256 nextTokenId = tokenId + 1;
    if (_ownerships[nextTokenId].addr == address(0)) {
      if (_exists(nextTokenId)) {
        _ownerships[nextTokenId] = TokenOwnership(
          prevOwnership.addr,
          prevOwnership.startTimestamp
        );
      }
    }

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

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

  uint256 public nextOwnerToExplicitlySet = 0;

  /**
   * @dev Explicitly set `owners` to eliminate loops in future calls of ownerOf().
   */
  function _setOwnersExplicit(uint256 quantity) internal {
    uint256 oldNextOwnerToSet = nextOwnerToExplicitlySet;
    require(quantity > 0, "quantity must be nonzero");
    uint256 endIndex = oldNextOwnerToSet + quantity - 1;
    if (endIndex > collectionSize - 1) {
      endIndex = collectionSize - 1;
    }
    // We know if the last one in the group exists, all in the group exist, due to serial ordering.
    require(_exists(endIndex), "not enough minted yet for this cleanup");
    for (uint256 i = oldNextOwnerToSet; i <= endIndex; i++) {
      if (_ownerships[i].addr == address(0)) {
        TokenOwnership memory ownership = ownershipOf(i);
        _ownerships[i] = TokenOwnership(
          ownership.addr,
          ownership.startTimestamp
        );
      }
    }
    nextOwnerToExplicitlySet = endIndex + 1;
  }

  /**
   * @dev Internal function to invoke {IERC721Receiver-onERC721Received} on a target address.
   * The call is not executed if the target address is not a contract.
   *
   * @param from address representing the previous owner of the given token ID
   * @param to target address that will receive the tokens
   * @param tokenId uint256 ID of the token to be transferred
   * @param _data bytes optional data to send along with the call
   * @return bool whether the call correctly returned the expected magic value
   */
  function _checkOnERC721Received(
    address from,
    address to,
    uint256 tokenId,
    bytes memory _data
  ) private returns (bool) {
    if (to.isContract()) {
      try
        IERC721Receiver(to).onERC721Received(_msgSender(), from, tokenId, _data)
      returns (bytes4 retval) {
        return retval == IERC721Receiver(to).onERC721Received.selector;
      } catch (bytes memory reason) {
        if (reason.length == 0) {
          revert("ERC721A: transfer to non ERC721Receiver implementer");
        } else {
          assembly {
            revert(add(32, reason), mload(reason))
          }
        }
      }
    } else {
      return true;
    }
  }

  /**
   * @dev Hook that is called before a set of serially-ordered token ids are about to be transferred. This includes minting.
   *
   * 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`.
   */
  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.
   *
   * 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` and `to` are never both zero.
   */
  function _afterTokenTransfers(
    address from,
    address to,
    uint256 startTokenId,
    uint256 quantity
  ) internal virtual {}
}