// File: contracts/CnickEVolution.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.9;

import "erc721b/contracts/extensions/ERC721BPausable.sol";
import "erc721b/contracts/extensions/ERC721BStaticTokenURI.sol";
import "erc721b/contracts/extensions/ERC721BContractURIStorage.sol";

import "./lib/Treasury.sol";
import "@openzeppelin/contracts/utils/cryptography/MerkleProof.sol";

import "erc721b/contracts/presets/ERC721BPresetStandard.sol";

contract CnickEVolution is
    Ownable,
    ERC721BPresetStandard,
    ERC721BPausable,
    ERC721BContractURIStorage,
    Treasury
{
    using Strings for uint256;
    enum SalePublicity {
        PRIVATE,
        PUBLIC
    }

    // EVENTS  *****************************************************
    event ReceivedEther(address indexed sender, uint256 indexed amount);
    event AllowlistSignerUpdated(address _signer);

    uint256 public constant MAX_SUPPLY = 500;
    uint256 public constant MAX_PER_WALLET = 10;
    uint256 public currentMaxSupply = 50;
    uint256 public mintPrice = 0.1 ether;
    SalePublicity public publicSale = SalePublicity.PRIVATE;

    address[] private mintPayees = [
        0xC1e227135D7115E40B589fF1a491cA8d1dE21E48, // Cnick
        0xBB11b7858BDdf9D6B3d9bdbcd4D579Ba9AC9741d, // Artist
        0xBa4491E278CA6cCDbA68749673dEF8A0112C1F8f // Dev
    ];

    uint256[] private mintShares = [77, 20, 3];

    bytes32 public merkleRoot;

    mapping(address => uint256) private walletMints;

    constructor(
        string memory name,
        string memory symbol,
        string memory contractUri,
        string memory baseUri,
        address[] memory operators
    )
        payable
        ERC721BPresetStandard(name, symbol)
        Treasury(mintPayees, mintShares)
    {
        _setContractURI(contractUri);
        _setBaseURI(baseUri);
        _pause();
        for (uint256 i = 0; i < operators.length; i++) {
            setApprovalForAll(operators[i], true);
        }
    }

    // External functions *****************************************************
    function setBaseTokenURI(string memory uri) external virtual onlyOwner {
        _setBaseURI(uri);
    }

    // Public functions *****************************************************

    function pause() public virtual onlyOwner {
        _pause();
    }

    function unpause() public virtual onlyOwner {
        _unpause();
    }

    function togglePublicSale() public virtual onlyOwner {
        if (publicSale == SalePublicity.PRIVATE)
            publicSale = SalePublicity.PUBLIC;
        else publicSale = SalePublicity.PRIVATE;
    }

    function setMintPrice(uint256 _newMintPrice) public onlyOwner {
        mintPrice = _newMintPrice;
    }

    function setMerkleRoot(bytes32 _merkleRoot) public onlyOwner {
        merkleRoot = _merkleRoot;
    }

    function setCurrentSupply(uint256 _currentMaxSupply) public onlyOwner {
        currentMaxSupply = _currentMaxSupply > MAX_SUPPLY
            ? MAX_SUPPLY
            : _currentMaxSupply;
    }

    function publicMint(uint256 numberOfTokens) public payable {
        require(!paused(), "Minting is paused");
        require(publicSale == SalePublicity.PUBLIC, "It is not public sale");

        require(
            (totalSupply() + numberOfTokens) <= currentMaxSupply,
            "Not enough CNEV remaining"
        );

        require(
            msg.value == mintPrice * numberOfTokens,
            "Incorrect payment amount"
        );

        require(
            (walletMints[msg.sender] + numberOfTokens) <= MAX_PER_WALLET,
            "Mint limit exceeded"
        );

        walletMints[msg.sender] = walletMints[msg.sender] + numberOfTokens;
        _safeMint(msg.sender, numberOfTokens);
    }

    function allowListMint(
        uint256 numberOfTokens,
        bytes32[] calldata _merkleProof
    ) public payable {
        require(!paused(), "Minting is paused");
        require(publicSale == SalePublicity.PRIVATE, "It is not private sale");

        require(
            msg.value == (mintPrice * numberOfTokens),
            "Incorrect payment amount"
        );
        require(
            (walletMints[msg.sender] + numberOfTokens) <= MAX_PER_WALLET,
            "Mint limit exceeded"
        );
        require(
            (totalSupply() + numberOfTokens) <= currentMaxSupply,
            "Not enough CNEV remaining"
        );

        bytes32 leaf = keccak256(abi.encodePacked(msg.sender));
        require(
            MerkleProof.verify(_merkleProof, merkleRoot, leaf),
            "Invalid proof."
        );

        walletMints[msg.sender] = walletMints[msg.sender] + numberOfTokens;

        _safeMint(msg.sender, numberOfTokens);
    }

    function withdrawAll() public onlyOwner {
        require(address(this).balance > 0, "No balance to withdraw");

        for (uint256 i = 0; i < mintPayees.length; i++) {
            super.release(payable(super.payee(i)));
        }
    }

    // Public functions that are view *****************************************************

    function tokenURI(uint256 tokenId)
        public
        view
        virtual
        override(IERC721Metadata)
        returns (string memory)
    {
        if (!_exists(tokenId)) revert NonExistentToken();

        string memory _tokenURI = tokenId.toString();
        string memory base = baseTokenURI();

        // If there is no base URI, return the token URI.
        if (bytes(base).length == 0) {
            return _tokenURI;
        }

        // If both are set, concatenate the baseURI and tokenURI (via abi.encodePacked).
        if (bytes(_tokenURI).length > 0) {
            return string(abi.encodePacked(base, _tokenURI));
        }

        return
            bytes(base).length > 0
                ? string(abi.encodePacked(base, tokenId.toString()))
                : "";
    }

    function ownerOf(uint256 tokenId)
        public
        view
        virtual
        override(ERC721B, IERC721)
        returns (address)
    {
        return super.ownerOf(tokenId);
    }

    function supportsInterface(bytes4 interfaceId)
        public
        view
        virtual
        override(ERC721B, ERC721BPresetStandard)
        returns (bool)
    {
        return super.supportsInterface(interfaceId);
    }

    function totalSupply()
        public
        view
        virtual
        override(ERC721B)
        returns (uint256)
    {
        return super.totalSupply();
    }

    // Internal functions *****************************************************

    function _beforeTokenTransfers(
        address from,
        address to,
        uint256 startTokenId,
        uint256 amount
    ) internal virtual override(ERC721B, ERC721BPausable) {
        super._beforeTokenTransfers(from, to, startTokenId, amount);
    }

    function _exists(uint256 tokenId)
        internal
        view
        virtual
        override(ERC721B)
        returns (bool)
    {
        return super._exists(tokenId);
    }
}


// File: erc721b/contracts/extensions/ERC721BPausable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../ERC721B.sol";
import "@openzeppelin/contracts/security/Pausable.sol";

/**
 * @dev ERC721B token with pausable token transfers, minting and burning.
 *
 * Useful for scenarios such as preventing trades until the end of an evaluation
 * period, or having an emergency switch for freezing all token transfers in the
 * event of a large bug.
 */
abstract contract ERC721BPausable is Pausable, ERC721B {
  /**
   * @dev Hook that is called before a set of serially-ordered token ids 
   * are about to be transferred. This includes minting.
   */
  function _beforeTokenTransfers(
    address from,
    address to,
    uint256 startTokenId,
    uint256 amount
  ) internal virtual override {
    if (paused()) revert InvalidCall();
    super._beforeTokenTransfers(from, to, startTokenId, amount);
  }
}

// File: erc721b/contracts/extensions/ERC721BStaticTokenURI.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC721/extensions/IERC721Metadata.sol";
import "../ERC721B.sol";

/**
 * @dev ERC721 token with storage based token URI management.
 */
abstract contract ERC721BStaticTokenURI is ERC721B, IERC721Metadata {
  // Optional mapping for token URIs
  mapping(uint256 => string) private _tokenURIs;

  /**
   * @dev See {IERC721Metadata-tokenURI}.
   */
  function tokenURI(uint256 tokenId) public view virtual returns(string memory) {
    return staticTokenURI(tokenId);
  }

  /**
   * @dev See {IERC721Metadata-tokenURI}.
   */
  function staticTokenURI(uint256 tokenId) public view virtual returns(string memory) {
    if(!_exists(tokenId)) revert NonExistentToken();
    return _tokenURIs[tokenId];
  }

  /**
   * @dev Sets `_tokenURI` as the tokenURI of `tokenId`.
   *
   * Requirements:
   *
   * - `tokenId` must exist.
   */
  function _setTokenURI(uint256 tokenId, string memory _tokenURI) internal virtual {
    if(!_exists(tokenId)) revert NonExistentToken();
    _tokenURIs[tokenId] = _tokenURI;
  }
}

// File: erc721b/contracts/extensions/ERC721BContractURIStorage.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../ERC721B.sol";

/**
 * @dev ERC721B contract with a URI descriptor
 */
abstract contract ERC721BContractURIStorage is ERC721B {
  //immutable contract uri
  string private _contractURI;

  /**
   * @dev The URI for contract data ex. https://creatures-api.opensea.io/contract/opensea-creatures/contract.json
   * Example Format:
   * {
   *   "name": "OpenSea Creatures",
   *   "description": "OpenSea Creatures are adorable aquatic beings primarily for demonstrating what can be done using the OpenSea platform. Adopt one today to try out all the OpenSea buying, selling, and bidding feature set.",
   *   "image": "https://openseacreatures.io/image.png",
   *   "external_link": "https://openseacreatures.io",
   *   "seller_fee_basis_points": 100, # Indicates a 1% seller fee.
   *   "fee_recipient": "0xA97F337c39cccE66adfeCB2BF99C1DdC54C2D721" # Where seller fees will be paid to.
   * }
   */
  function contractURI() external view returns (string memory) {
    return _contractURI;
  }

  /**
   * @dev Sets contract uri
   */
  function _setContractURI(string memory uri) internal virtual {
    _contractURI = uri;
  }
}

// File: contracts/lib/Treasury.sol



// SPDX-License-Identifier: MIT
// @PixsaOJ

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "@openzeppelin/contracts/utils/Address.sol";
import "@openzeppelin/contracts/utils/Context.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

/**
 * @title Treasury
 * @dev This contract allows to split Ether payments among a group of accounts. The sender does not need to be aware
 * that the Ether will be split in this way, since it is handled transparently by the contract.
 *
 * The split can be in equal parts or in any other arbitrary proportion. The way this is specified is by assigning each
 * account to a number of shares. Of all the Ether that this contract receives, each account will then be able to claim
 * an amount proportional to the percentage of total shares they were assigned.
 *
 * `Treasury` follows a _pull payment_ model. This means that payments are not automatically forwarded to the
 * accounts but kept in this contract, and the actual transfer is triggered as a separate step by calling the {release}
 * function.
 *
 */
contract Treasury is Context {
    event PayeeAdded(address account, uint256 shares);
    event PaymentReleased(address to, uint256 amount);
    event PaymentReceived(address from, uint256 amount);

    uint256 private _totalShares;
    uint256 private _totalReleased;

    mapping(address => uint256) private _shares;
    mapping(address => uint256) private _released;
    address[] private _payees;

    /**
     * @dev Creates an instance of `Treasury` where each account in `payees` is assigned the number of shares at
     * the matching position in the `shares` array.
     *
     * All addresses in `payees` must be non-zero. Both arrays must have the same non-zero length, and there must be no
     * duplicates in `payees`.
     */
    constructor(address[] memory payees, uint256[] memory shares_) payable {
        require(
            payees.length == shares_.length,
            "Payees & shares length mismatch"
        );
        require(payees.length > 0, "Treasury: no payees");

        for (uint256 i = 0; i < payees.length; i++) {
            _addPayee(payees[i], shares_[i]);
        }
    }

    /**
     * @dev The Ether received will be logged with {PaymentReceived} events. Note that these events are not fully
     * reliable: it's possible for a contract to receive Ether without triggering this function. This only affects the
     * reliability of the events, and not the actual splitting of Ether.
     *
     * To learn more about this see the Solidity documentation for
     * https://solidity.readthedocs.io/en/latest/contracts.html#fallback-function[fallback
     * functions].
     */
    fallback() external payable virtual {
        emit PaymentReceived(_msgSender(), msg.value);
    }

    receive() external payable virtual {
        emit PaymentReceived(_msgSender(), msg.value);
    }

    /**
     * @dev Getter for the total amount of Ether already released.
     */
    function totalReleased() private view returns (uint256) {
        return _totalReleased;
    }

    /**
     * @dev Getter for the amount of Ether already released to a payee.
     */
    function released(address account) private view returns (uint256) {
        return _released[account];
    }

    /**
     * @dev Getter for the address of the payee number `index`.
     */
    function payee(uint256 index) internal view returns (address) {
        return _payees[index];
    }

    /**
     * @dev Triggers a transfer to `account` of the amount of Ether they are owed, according to their percentage of the
     * total shares and their previous withdrawals.
     */
    function release(address payable account) internal {
        require(_shares[account] > 0, "Treasury: account has no shares");

        uint256 totalReceived = address(this).balance + totalReleased();
        uint256 payment = _pendingPayment(
            account,
            totalReceived,
            released(account)
        );

        require(payment != 0, "Account is not due payment");

        _released[account] += payment;
        _totalReleased += payment;

        Address.sendValue(account, payment);
        emit PaymentReleased(account, payment);
    }

    /**
     * @dev internal logic for computing the pending payment of an `account` given the token historical balances and
     * already released amounts.
     */
    function _pendingPayment(
        address account,
        uint256 totalReceived,
        uint256 alreadyReleased
    ) private view returns (uint256) {
        return
            (totalReceived * _shares[account]) / _totalShares - alreadyReleased;
    }

    /**
     * @dev Add a new payee to the contract.
     * @param account The address of the payee to add.
     * @param shares_ The number of shares owned by the payee.
     */
    function _addPayee(address account, uint256 shares_) private {
        require(account != address(0), "Account is the zero address");
        require(shares_ > 0, "Treasury: shares are 0");
        require(_shares[account] == 0, "Account already has shares");

        _payees.push(account);
        _shares[account] = shares_;
        _totalShares = _totalShares + shares_;
        emit PayeeAdded(account, shares_);
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (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.
 */
library MerkleProof {
    /**
     * @dev Returns true if a `leaf` can be proved to be a part of a Merkle tree
     * defined by `root`. For this, a `proof` must be provided, containing
     * sibling hashes on the branch from the leaf to the root of the tree. Each
     * pair of leaves and each pair of pre-images are assumed to be sorted.
     */
    function verify(
        bytes32[] memory proof,
        bytes32 root,
        bytes32 leaf
    ) internal pure returns (bool) {
        return processProof(proof, leaf) == root;
    }

    /**
     * @dev Returns the rebuilt hash obtained by traversing a Merklee tree up
     * from `leaf` using `proof`. A `proof` is valid if and only if the rebuilt
     * hash matches the root of the tree. When processing the proof, the pairs
     * of leafs & pre-images are assumed to be sorted.
     *
     * _Available since v4.4._
     */
    function processProof(bytes32[] memory proof, bytes32 leaf) internal pure returns (bytes32) {
        bytes32 computedHash = leaf;
        for (uint256 i = 0; i < proof.length; i++) {
            bytes32 proofElement = proof[i];
            if (computedHash <= proofElement) {
                // Hash(current computed hash + current element of the proof)
                computedHash = _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: erc721b/contracts/presets/ERC721BPresetStandard.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/access/Ownable.sol";

import "../extensions/ERC721Metadata.sol";
import "../extensions/ERC721BBaseTokenURI.sol";

contract ERC721BPresetStandard is 
  Ownable, 
  ERC721Metadata, 
  ERC721BBaseTokenURI
{ 
  /**
   * @dev Sets the name, symbol
   */
  constructor(string memory name, string memory symbol) 
    ERC721Metadata(name, symbol) {}

  /**
   * @dev Allows owner to mint
   */
  function mint(address to, uint256 quantity) external onlyOwner {
    _safeMint(to, quantity);
  }

  /**
   * @dev See {IERC165-supportsInterface}.
   */
  function supportsInterface(bytes4 interfaceId) 
    public view virtual override(ERC721B, IERC165) returns(bool) 
  {
    return interfaceId == type(IERC721Metadata).interfaceId
      || super.supportsInterface(interfaceId);
  }
}
// File: erc721b/contracts/ERC721B.sol



// 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/utils/Context.sol";
import "@openzeppelin/contracts/utils/introspection/ERC165.sol";

error InvalidCall();
error BalanceQueryZeroAddress();
error NonExistentToken();
error ApprovalToCurrentOwner();
error ApprovalOwnerIsOperator();
error NotERC721Receiver();
error ERC721ReceiverNotReceived();

/**
 * @dev Implementation of https://eips.ethereum.org/EIPS/eip-721[ERC721] 
 * Non-Fungible Token Standard, including the Metadata extension and 
 * token Auto-ID generation.
 *
 * You must provide `name()` `symbol()` and `tokenURI(uint256 tokenId)`
 * to conform with IERC721Metadata
 */
abstract contract ERC721B is Context, ERC165, IERC721 {

  // ============ Storage ============

  // The last token id minted
  uint256 private _lastTokenId;
  // Mapping from token ID to owner address
  mapping(uint256 => address) internal _owners;
  // Mapping owner address to token count
  mapping(address => uint256) internal _balances;

  // Mapping from token ID to approved address
  mapping(uint256 => address) private _tokenApprovals;
  // Mapping from owner to operator approvals
  mapping(address => mapping(address => bool)) private _operatorApprovals;

  // ============ Read Methods ============

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

  /**
   * @dev Shows the overall amount of tokens generated in the contract
   */
  function totalSupply() public view virtual returns(uint256) {
    return _lastTokenId;
  }

  /**
   * @dev See {IERC721-ownerOf}.
   */
  function ownerOf(uint256 tokenId) 
    public view virtual override returns(address) 
  {
    unchecked {
      //this is the situation when _owners normalized
      uint256 id = tokenId;
      if (_owners[id] != address(0)) {
        return _owners[id];
      }
      //this is the situation when _owners is not normalized
      if (id > 0 && id <= _lastTokenId) {
        //there will never be a case where token 1 is address(0)
        while(true) {
          id--;
          if (id == 0) {
            break;
          } else if (_owners[id] != address(0)) {
            return _owners[id];
          }
        }
      }
    }

    revert NonExistentToken();
  }

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

  // ============ Approval Methods ============

  /**
   * @dev See {IERC721-approve}.
   */
  function approve(address to, uint256 tokenId) public virtual override {
    address owner = ERC721B.ownerOf(tokenId);
    if (to == owner) revert ApprovalToCurrentOwner();

    address sender = _msgSender();
    if (sender != owner && !isApprovedForAll(owner, sender)) 
      revert ApprovalToCurrentOwner();

    _approve(to, tokenId, owner);
  }

  /**
   * @dev See {IERC721-getApproved}.
   */
  function getApproved(uint256 tokenId) 
    public view virtual override returns(address) 
  {
    if (!_exists(tokenId)) revert NonExistentToken();
    return _tokenApprovals[tokenId];
  }

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

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

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

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

  /**
   * @dev Approve `operator` to operate on all of `owner` tokens
   *
   * Emits a {ApprovalForAll} event.
   */
  function _setApprovalForAll(
    address owner,
    address operator,
    bool approved
  ) internal virtual {
    if (owner == operator) revert ApprovalOwnerIsOperator();
    _operatorApprovals[owner][operator] = approved;
    emit ApprovalForAll(owner, operator, approved);
  }

  // ============ Mint Methods ============

  /**
   * @dev Mints `tokenId` and transfers it to `to`.
   *
   * WARNING: Usage of this method is discouraged, use {_safeMint} 
   * whenever possible
   *
   * Requirements:
   *
   * - `tokenId` must not exist.
   * - `to` cannot be the zero address.
   *
   * Emits a {Transfer} event.
   */
  function _mint(
    address to,
    uint256 amount,
    bytes memory _data,
    bool safeCheck
  ) private {
    if(amount == 0 || to == address(0)) revert InvalidCall();
    uint256 startTokenId = _lastTokenId + 1;
    
    _beforeTokenTransfers(address(0), to, startTokenId, amount);
    
    unchecked {
      _lastTokenId += amount;
      _balances[to] += amount;
      _owners[startTokenId] = to;

      _afterTokenTransfers(address(0), to, startTokenId, amount);

      uint256 updatedIndex = startTokenId;
      //if do safe check and,
      //check if contract one time (instead of loop)
      //see: @openzep/utils/Address.sol
      if (safeCheck && to.code.length > 0) {
        //loop emit transfer and received check
        for (uint256 i; i < amount; i++) {
          emit Transfer(address(0), to, updatedIndex);
          if (!_checkOnERC721Received(address(0), to, updatedIndex, _data))
            revert ERC721ReceiverNotReceived();
          updatedIndex++;
        }
        return;
      }

      for (uint256 i; i < amount; i++) {
        emit Transfer(address(0), to, updatedIndex);
        updatedIndex++;
      }
    }
  }

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

  /**
   * @dev Same as {xref-ERC721-_safeMint-address-uint256-}[`_safeMint`], 
   * with an additional `data` parameter which is forwarded in 
   * {IERC721Receiver-onERC721Received} to contract recipients.
   */
  function _safeMint(
    address to,
    uint256 amount,
    bytes memory _data
  ) internal virtual {
    _mint(to, amount, _data, true);
  }

  // ============ Transfer Methods ============

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

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

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

  /**
   * @dev Internal function to invoke {IERC721Receiver-onERC721Received} 
   * on a target address. The call is not executed if the target address 
   * is not a contract.
   */
  function _checkOnERC721Received(
    address from,
    address to,
    uint256 tokenId,
    bytes memory _data
  ) private returns (bool) {
    try IERC721Receiver(to).onERC721Received(
      _msgSender(), from, tokenId, _data
    ) returns (bytes4 retval) {
      return retval == IERC721Receiver.onERC721Received.selector;
    } catch (bytes memory reason) {
      if (reason.length == 0) {
        revert NotERC721Receiver();
      } else {
        assembly {
          revert(add(32, reason), mload(reason))
        }
      }
    }
  }

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

  /**
   * @dev Safely transfers `tokenId` token from `from` to `to`, checking 
   * first that contract recipients are aware of the ERC721 protocol to 
   * prevent tokens from being forever locked.
   *
   * `_data` is additional data, it has no specified format and it is 
   * sent in call to `to`.
   *
   * This internal function is equivalent to {safeTransferFrom}, and can 
   * be used to e.g.
   * implement alternative mechanisms to perform token transfer, such as 
   * signature-based.
   *
   * Requirements:
   *
   * - `from` cannot be the zero address.
   * - `to` cannot be the zero address.
   * - `tokenId` token must exist and be owned by `from`.
   * - If `to` refers to a smart contract, it must implement 
   *   {IERC721Receiver-onERC721Received}, which is called upon a 
   *   safe transfer.
   *
   * Emits a {Transfer} event.
   */
  function _safeTransfer(
    address from,
    address to,
    uint256 tokenId,
    bytes memory _data
  ) internal virtual {
    _transfer(from, to, tokenId);
    //see: @openzep/utils/Address.sol
    if (to.code.length > 0
      && !_checkOnERC721Received(from, to, tokenId, _data)
    ) revert ERC721ReceiverNotReceived();
  }

  /**
   * @dev Transfers `tokenId` from `from` to `to`. As opposed to 
   * {transferFrom}, this imposes no restrictions on msg.sender.
   *
   * Requirements:
   *
   * - `to` cannot be the zero address.
   * - `tokenId` token must be owned by `from`.
   *
   * Emits a {Transfer} event.
   */
  function _transfer(address from, address to, uint256 tokenId) private {
    if (to == address(0)) revert InvalidCall();
    //get owner
    address owner = ERC721B.ownerOf(tokenId);
    //owner should be the `from`
    if (from != owner 
      || !_isApprovedOrOwner(_msgSender(), tokenId, owner)
    ) revert InvalidCall();

    _beforeTokenTransfers(from, to, tokenId, 1);
    
    // Clear approvals from the previous owner
    _approve(address(0), tokenId, from);

    unchecked {
      //this is the situation when _owners are normalized
      _balances[to] += 1;
      _balances[from] -= 1;
      _owners[tokenId] = to;
      //this is the situation when _owners are not normalized
      uint256 nextTokenId = tokenId + 1;
      if (nextTokenId <= _lastTokenId && _owners[nextTokenId] == address(0)) {
        _owners[nextTokenId] = from;
      }
    }

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

  // ============ TODO Methods ============

  /**
   * @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
   * amount - 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 amount
  ) 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
   * amount - 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 amount
  ) internal virtual {}
}

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



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

pragma solidity ^0.8.0;

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

/**
 * @dev Contract module which allows children to implement an emergency stop
 * mechanism that can be triggered by an authorized account.
 *
 * This module is used through inheritance. It will make available the
 * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
 * the functions of your contract. Note that they will not be pausable by
 * simply including this module, only once the modifiers are put in place.
 */
abstract contract Pausable is Context {
    /**
     * @dev Emitted when the pause is triggered by `account`.
     */
    event Paused(address account);

    /**
     * @dev Emitted when the pause is lifted by `account`.
     */
    event Unpaused(address account);

    bool private _paused;

    /**
     * @dev Initializes the contract in unpaused state.
     */
    constructor() {
        _paused = false;
    }

    /**
     * @dev Returns true if the contract is paused, and false otherwise.
     */
    function paused() public view virtual returns (bool) {
        return _paused;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    modifier whenNotPaused() {
        require(!paused(), "Pausable: paused");
        _;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    modifier whenPaused() {
        require(paused(), "Pausable: not paused");
        _;
    }

    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    function _pause() internal virtual whenNotPaused {
        _paused = true;
        emit Paused(_msgSender());
    }

    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    function _unpause() internal virtual whenPaused {
        _paused = false;
        emit Unpaused(_msgSender());
    }
}

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



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

pragma solidity ^0.8.0;

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

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

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

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

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

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

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

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

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

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

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

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

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

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



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

pragma solidity ^0.8.0;

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

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



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

pragma solidity ^0.8.0;

import "./IERC165.sol";

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

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



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

pragma solidity ^0.8.0;

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

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



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

pragma solidity ^0.8.0;

import "../IERC721.sol";

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

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

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

// File: @openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";
import "../../../utils/Address.sol";

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using Address for address;

    function safeTransfer(
        IERC20 token,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(
        IERC20 token,
        address from,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        require(
            (value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        uint256 newAllowance = token.allowance(address(this), spender) + value;
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        unchecked {
            uint256 oldAllowance = token.allowance(address(this), spender);
            require(oldAllowance >= value, "SafeERC20: decreased allowance below zero");
            uint256 newAllowance = oldAllowance - value;
            _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
        }
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) {
            // Return data is optional
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// 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/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/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `from` to `to` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: erc721b/contracts/extensions/ERC721Metadata.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC721/extensions/IERC721Metadata.sol";

/**
 * @title ERC721B Burnable Token
 * @dev ERC721B Token that can be irreversibly burned (destroyed).
 */
abstract contract ERC721Metadata is IERC721Metadata {
  string private _name;
  string private _symbol;

  /**
   * @dev Sets the name, symbol
   */
  constructor(string memory name_, string memory symbol_) {
    _name = name_;
    _symbol = symbol_;
  }

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

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

// File: erc721b/contracts/extensions/ERC721BBaseTokenURI.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC721/extensions/IERC721Metadata.sol";
import "@openzeppelin/contracts/utils/Strings.sol";
import "../ERC721B.sol";

/**
 * @dev ERC721B token where token URIs are determined with a base URI
 */
abstract contract ERC721BBaseTokenURI is ERC721B, IERC721Metadata {
  using Strings for uint256;
  string private _baseTokenURI;

  /**
   * @dev See {IERC721Metadata-tokenURI}.
   */
  function tokenURI(uint256 tokenId) public view virtual returns(string memory) {
    if(!_exists(tokenId)) revert NonExistentToken();
    string memory baseURI = _baseTokenURI;
    return bytes(baseURI).length > 0 ? string(
      abi.encodePacked(baseURI, tokenId.toString())
    ) : "";
  }
  
  /**
   * @dev The base URI for token data ex. https://creatures-api.opensea.io/api/creature/
   * Example Usage: 
   *  Strings.strConcat(baseTokenURI(), Strings.uint2str(tokenId))
   */
  function baseTokenURI() public view returns (string memory) {
    return _baseTokenURI;
  }

  /**
   * @dev Setting base token uri would be acceptable if using IPFS CIDs
   */
  function _setBaseURI(string memory uri) internal virtual {
    _baseTokenURI = uri;
  }
}

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



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

pragma solidity ^0.8.0;

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

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

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

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

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