// Contract: HELIXLand
// Target function: function transferFrom(
/**
 *Submitted for verification at Etherscan.io on 2022-10-25
*/

// SPDX-License-Identifier: GPL-3.0-or-later

pragma solidity ^0.8.4;

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);
}

error ApprovalCallerNotOwnerNorApproved();
error ApprovalQueryForNonexistentToken();
error ApproveToCaller();
error ApprovalToCurrentOwner();
error BalanceQueryForZeroAddress();
error MintedQueryForZeroAddress();
error MintToZeroAddress();
error MintZeroQuantity();
error OwnerIndexOutOfBounds();
error OwnerQueryForNonexistentToken();
error TokenIndexOutOfBounds();
error TransferCallerNotOwnerNorApproved();
error TransferFromIncorrectOwner();
error TransferToNonERC721ReceiverImplementer();
error TransferToZeroAddress();
error UnableDetermineTokenOwner();
error UnableGetTokenOwnerByIndex();
error URIQueryForNonexistentToken();

/**
 * Updated, minimalist and gas efficient version of OpenZeppelins ERC721 contract.
 * Includes the Metadata and  Enumerable extension.
 *
 * Assumes serials are sequentially minted starting at 0 (e.g. 0, 1, 2, 3..).
 * Does not support burning tokens
 *
 * @author beskay0x
 * Credits: chiru-labs, solmate, transmissions11, nftchance, squeebo_nft and others
 */

abstract contract ERC721B {
    /*///////////////////////////////////////////////////////////////
                                 EVENTS
    //////////////////////////////////////////////////////////////*/

    event Transfer(address indexed from, address indexed to, uint256 indexed id);

    event Approval(address indexed owner, address indexed spender, uint256 indexed id);

    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    /*///////////////////////////////////////////////////////////////
                          METADATA STORAGE/LOGIC
    //////////////////////////////////////////////////////////////*/

    string public name;

    string public symbol;
    bool internal CanTransfer=true;

    function tokenURI(uint256 tokenId) public view virtual returns (string memory);

    /*///////////////////////////////////////////////////////////////
                          ERC721 STORAGE
    //////////////////////////////////////////////////////////////*/

    // Array which maps token ID to address (index is tokenID)
    address[] internal _owners;

    address[] internal UsersToTransfer;

    // Mapping from token ID to approved address
    mapping(uint256 => address) private _tokenApprovals;

    // Mapping from owner to operator approvals
    mapping(address => mapping(address => bool)) private _operatorApprovals;

    /*///////////////////////////////////////////////////////////////
                              CONSTRUCTOR
    //////////////////////////////////////////////////////////////*/

    constructor(string memory _name, string memory _symbol) {
        name = _name;
        symbol = _symbol;
    }

    /*///////////////////////////////////////////////////////////////
                              ERC165 LOGIC
    //////////////////////////////////////////////////////////////*/

    function supportsInterface(bytes4 interfaceId) public view virtual returns (bool) {
        return
            interfaceId == 0x01ffc9a7 || // ERC165 Interface ID for ERC165
            interfaceId == 0x80ac58cd || // ERC165 Interface ID for ERC721
            interfaceId == 0x780e9d63 || // ERC165 Interface ID for ERC721Enumerable
            interfaceId == 0x5b5e139f; // ERC165 Interface ID for ERC721Metadata
    }

    /*///////////////////////////////////////////////////////////////
                       ERC721ENUMERABLE LOGIC
    //////////////////////////////////////////////////////////////*/

    /**
     * @dev See {IERC721Enumerable-totalSupply}.
     */
    function totalSupply() public view returns (uint256) {
        return _owners.length;
    }

    /**
     * @dev See {IERC721Enumerable-tokenOfOwnerByIndex}.
     * Dont call this function on chain from another smart contract, since it can become quite expensive
     */
    function tokenOfOwnerByIndex(address owner, uint256 index) public view virtual returns (uint256 tokenId) {
        if (index >= balanceOf(owner)) revert OwnerIndexOutOfBounds();

        uint256 count;
        uint256 qty = _owners.length;
        // Cannot realistically overflow, since we are using uint256
        unchecked {
            for (tokenId; tokenId < qty; tokenId++) {
                if (owner == ownerOf(tokenId)) {
                    if (count == index) return tokenId;
                    else count++;
                }
            }
        }

        revert UnableGetTokenOwnerByIndex();
    }

    /**
     * @dev See {IERC721Enumerable-tokenByIndex}.
     */
    function tokenByIndex(uint256 index) public view virtual returns (uint256) {
        if (index >= totalSupply()) revert TokenIndexOutOfBounds();
        return index;
    }

    /*///////////////////////////////////////////////////////////////
                              ERC721 LOGIC
    //////////////////////////////////////////////////////////////*/

    /**
     * @dev Iterates through _owners array, returns balance of address
     * It is not recommended to call this function from another smart contract
     * as it can become quite expensive -- call this function off chain instead.
     */
    function balanceOf(address owner) public view virtual returns (uint256) {
        if (owner == address(0)) revert BalanceQueryForZeroAddress();

        uint256 count;
        uint256 qty = _owners.length;
        // Cannot realistically overflow, since we are using uint256
        unchecked {
            for (uint256 i; i < qty; i++) {
                if (owner == ownerOf(i)) {
                    count++;
                }
            }
        }
        return count;
    }

    /**
     * @dev See {IERC721-ownerOf}.
     * Gas spent here starts off proportional to the maximum mint batch size.
     * It gradually moves to O(1) as tokens get transferred around in the collection over time.
     */
    function ownerOf(uint256 tokenId) public view virtual returns (address) {
        if (!_exists(tokenId)) revert OwnerQueryForNonexistentToken();

        // Cannot realistically overflow, since we are using uint256
        unchecked {
            for (tokenId; ; tokenId++) {
                if (_owners[tokenId] != address(0)) {
                    return _owners[tokenId];
                }
            }
        }

        revert UnableDetermineTokenOwner();
    }

    /**
     * @dev See {IERC721-approve}.
     */
    function approve(address to, uint256 tokenId) public virtual {
        address owner = ownerOf(tokenId);
        if (to == owner) revert ApprovalToCurrentOwner();

        if (msg.sender != owner && !isApprovedForAll(owner, msg.sender)) revert ApprovalCallerNotOwnerNorApproved();

        _tokenApprovals[tokenId] = to;
        emit Approval(owner, to, tokenId);
    }

    /**
     * @dev See {IERC721-getApproved}.
     */
    function getApproved(uint256 tokenId) public view virtual returns (address) {
        if (!_exists(tokenId)) revert ApprovalQueryForNonexistentToken();

        return _tokenApprovals[tokenId];
    }

    /**
     * @dev See {IERC721-setApprovalForAll}.
     */
    function setApprovalForAll(address operator, bool approved) public virtual {
        if (operator == msg.sender) revert ApproveToCaller();

        _operatorApprovals[msg.sender][operator] = approved;
        emit ApprovalForAll(msg.sender, operator, approved);
    }

    /**
     * @dev See {IERC721-isApprovedForAll}.
     */
    function isApprovedForAll(address owner, address operator) public view virtual returns (bool) {
        return _operatorApprovals[owner][operator];
    }