pragma solidity ^0.8.0;
// SPDX-License-Identifier: MIT

/**
 * @dev ERC-721 non-fungible token standard.
 * See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md.
 */
interface ERC721 {

  /**
   * @dev Emits when ownership of any NFT changes by any mechanism. This event emits when NFTs are
   * created (`from` == 0) and destroyed (`to` == 0). Exception: during contract creation, any
   * number of NFTs may be created and assigned without emitting Transfer. At the time of any
   * transfer, the approved address for that NFT (if any) is reset to none.
   */
  event Transfer(
    address indexed _from,
    address indexed _to,
    uint256 indexed _tokenId
  );

  /**
   * @dev This emits when the approved address for an NFT is changed or reaffirmed. The zero
   * address indicates there is no approved address. When a Transfer event emits, this also
   * indicates that the approved address for that NFT (if any) is reset to none.
   */
  event Approval(
    address indexed _owner,
    address indexed _approved,
    uint256 indexed _tokenId
  );

  /**
   * @dev This emits when an operator is enabled or disabled for an owner. The operator can manage
   * all NFTs of the owner.
   */
  event ApprovalForAll(
    address indexed _owner,
    address indexed _operator,
    bool _approved
  );

  /**
   * @notice Throws unless `msg.sender` is the current owner, an authorized operator, or the
   * approved address for this NFT. Throws if `_from` is not the current owner. Throws if `_to` is
   * the zero address. Throws if `_tokenId` is not a valid NFT. When transfer is complete, this
   * function checks if `_to` is a smart contract (code size > 0). If so, it calls
   * `onERC721Received` on `_to` and throws if the return value is not
   * `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`.
   * @dev Transfers the ownership of an NFT from one address to another address. This function can
   * be changed to payable.
   * @param _from The current owner of the NFT.
   * @param _to The new owner.
   * @param _tokenId The NFT to transfer.
   * @param _data Additional data with no specified format, sent in call to `_to`.
   */
  function safeTransferFrom(
    address _from,
    address _to,
    uint256 _tokenId,
    bytes calldata _data
  )
    external;

  /**
   * @notice This works identically to the other function with an extra data parameter, except this
   * function just sets data to ""
   * @dev Transfers the ownership of an NFT from one address to another address. This function can
   * be changed to payable.
   * @param _from The current owner of the NFT.
   * @param _to The new owner.
   * @param _tokenId The NFT to transfer.
   */
  function safeTransferFrom(
    address _from,
    address _to,
    uint256 _tokenId
  )
    external;

  /**
   * @notice The caller is responsible to confirm that `_to` is capable of receiving NFTs or else
   * they may be permanently lost.
   * @dev Throws unless `msg.sender` is the current owner, an authorized operator, or the approved
   * address for this NFT. Throws if `_from` is not the current owner. Throws if `_to` is the zero
   * address. Throws if `_tokenId` is not a valid NFT.  This function can be changed to payable.
   * @param _from The current owner of the NFT.
   * @param _to The new owner.
   * @param _tokenId The NFT to transfer.
   */
  function transferFrom(
    address _from,
    address _to,
    uint256 _tokenId
  )
    external;

  /**
   * @notice The zero address indicates there is no approved address. Throws unless `msg.sender` is
   * the current NFT owner, or an authorized operator of the current owner.
   * @param _approved The new approved NFT controller.
   * @dev Set or reaffirm the approved address for an NFT. This function can be changed to payable.
   * @param _tokenId The NFT to approve.
   */
  function approve(
    address _approved,
    uint256 _tokenId
  )
    external;

  /**
   * @notice The contract MUST allow multiple operators per owner.
   * @dev Enables or disables approval for a third party ("operator") to manage all of
   * `msg.sender`'s assets. It also emits the ApprovalForAll event.
   * @param _operator Address to add to the set of authorized operators.
   * @param _approved True if the operators is approved, false to revoke approval.
   */
  function setApprovalForAll(
    address _operator,
    bool _approved
  )
    external;

  /**
   * @dev Returns the number of NFTs owned by `_owner`. NFTs assigned to the zero address are
   * considered invalid, and this function throws for queries about the zero address.
   * @notice Count all NFTs assigned to an owner.
   * @param _owner Address for whom to query the balance.
   * @return Balance of _owner.
   */
  function balanceOf(
    address _owner
  )
    external
    view
    returns (uint256);

  /**
   * @notice Find the owner of an NFT.
   * @dev Returns the address of the owner of the NFT. NFTs assigned to the zero address are
   * considered invalid, and queries about them do throw.
   * @param _tokenId The identifier for an NFT.
   * @return Address of _tokenId owner.
   */
  function ownerOf(
    uint256 _tokenId
  )
    external
    view
    returns (address);

  /**
   * @notice Throws if `_tokenId` is not a valid NFT.
   * @dev Get the approved address for a single NFT.
   * @param _tokenId The NFT to find the approved address for.
   * @return Address that _tokenId is approved for.
   */
  function getApproved(
    uint256 _tokenId
  )
    external
    view
    returns (address);

  /**
   * @notice Query if an address is an authorized operator for another address.
   * @dev Returns true if `_operator` is an approved operator for `_owner`, false otherwise.
   * @param _owner The address that owns the NFTs.
   * @param _operator The address that acts on behalf of the owner.
   * @return True if approved for all, false otherwise.
   */
  function isApprovedForAll(
    address _owner,
    address _operator
  )
    external
    view
    returns (bool);

}

/**
 * @dev ERC-721 interface for accepting safe transfers.
 * See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md.
 */
interface ERC721TokenReceiver {

  /**
   * @notice The contract address is always the message sender. A wallet/broker/auction application
   * MUST implement the wallet interface if it will accept safe transfers.
   * @dev Handle the receipt of a NFT. The ERC721 smart contract calls this function on the
   * recipient after a `transfer`. This function MAY throw to revert and reject the transfer. Return
   * of other than the magic value MUST result in the transaction being reverted.
   * Returns `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))` unless throwing.
   * @param _operator The address which called `safeTransferFrom` function.
   * @param _from The address which previously owned the token.
   * @param _tokenId The NFT identifier which is being transferred.
   * @param _data Additional data with no specified format.
   * @return Returns `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`.
   */
  function onERC721Received(
    address _operator,
    address _from,
    uint256 _tokenId,
    bytes calldata _data
  )
    external
    returns(bytes4);

}


/**
 * @dev A standard for detecting smart contract interfaces. 
 * See: https://eips.ethereum.org/EIPS/eip-165.
 */
interface ERC165 {

  /**
   * @dev Checks if the smart contract includes a specific interface.
   * This function uses less than 30,000 gas.
   * @param _interfaceID The interface identifier, as specified in ERC-165.
   * @return True if _interfaceID is supported, false otherwise.
   */
  function supportsInterface(
    bytes4 _interfaceID
  )
    external
    view
    returns (bool);
    
}


/**
 * @dev Implementation of standard for detect smart contract interfaces.
 */
contract SupportsInterface is
  ERC165
{

  /**
   * @dev Mapping of supported intefraces. You must not set element 0xffffffff to true.
   */
  mapping(bytes4 => bool) internal supportedInterfaces;

  /**
   * @dev Contract constructor.
   */
  constructor()
  {
    supportedInterfaces[0x01ffc9a7] = true; // ERC165
  }

  /**
   * @dev Function to check which interfaces are suported by this contract.
   * @param _interfaceID Id of the interface.
   * @return True if _interfaceID is supported, false otherwise.
   */
  function supportsInterface(
    bytes4 _interfaceID
  )
    external
    override
    view
    returns (bool)
  {
    return supportedInterfaces[_interfaceID];
  }

}


/**
 * @notice Based on:
 * https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/Address.sol
 * Requires EIP-1052.
 * @dev Utility library of inline functions on addresses.
 */
library AddressUtils {

  /**
   * @dev Returns whether the target address is a contract.
   * @param _addr Address to check.
   * @return addressCheck True if _addr is a contract, false if not.
   */
  function isContract(
    address _addr
  )
    internal
    view
    returns (bool addressCheck)
  {
    // This method relies in extcodesize, which returns 0 for contracts in
    // construction, since the code is only stored at the end of the
    // constructor execution.

    // According to EIP-1052, 0x0 is the value returned for not-yet created accounts
    // and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned
    // for accounts without code, i.e. `keccak256('')`
    bytes32 codehash;
    bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
    assembly { codehash := extcodehash(_addr) } // solhint-disable-line
    addressCheck = (codehash != 0x0 && codehash != accountHash);
  }

}


/**
 * @dev Implementation of ERC-721 non-fungible token standard.
 */
contract NFToken is
  ERC721,
  SupportsInterface
{
  using AddressUtils for address;

  /**
   * @dev List of revert message codes. Implementing dApp should handle showing the correct message.
   * Based on 0xcert framework error codes.
   */
  string constant ZERO_ADDRESS = "003001";
  string constant NOT_VALID_NFT = "003002";
  string constant NOT_OWNER_OR_OPERATOR = "003003";
  string constant NOT_OWNER_APPROVED_OR_OPERATOR = "003004";
  string constant NOT_ABLE_TO_RECEIVE_NFT = "003005";
  string constant NFT_ALREADY_EXISTS = "003006";
  string constant NOT_OWNER = "003007";
  string constant IS_OWNER = "003008";

  /**
   * @dev Magic value of a smart contract that can receive NFT.
   * Equal to: bytes4(keccak256("onERC721Received(address,address,uint256,bytes)")).
   */
  bytes4 internal constant MAGIC_ON_ERC721_RECEIVED = 0x150b7a02;

  /**
   * @dev A mapping from NFT ID to the address that owns it.
   */
  mapping (uint256 => address) internal idToOwner;

  /**
   * @dev Mapping from NFT ID to approved address.
   */
  mapping (uint256 => address) internal idToApproval;

   /**
   * @dev Mapping from owner address to count of their tokens.
   */
  mapping (address => uint256) private ownerToNFTokenCount;

  /**
   * @dev Mapping from owner address to mapping of operator addresses.
   */
  mapping (address => mapping (address => bool)) internal ownerToOperators;

  /**
   * @dev Guarantees that the msg.sender is an owner or operator of the given NFT.
   * @param _tokenId ID of the NFT to validate.
   */
  modifier canOperate(
    uint256 _tokenId
  )
  {
    address tokenOwner = idToOwner[_tokenId];
    require(
      tokenOwner == msg.sender || ownerToOperators[tokenOwner][msg.sender],
      NOT_OWNER_OR_OPERATOR
    );
    _;
  }

  /**
   * @dev Guarantees that the msg.sender is allowed to transfer NFT.
   * @param _tokenId ID of the NFT to transfer.
   */
  modifier canTransfer(
    uint256 _tokenId
  )
  {
    address tokenOwner = idToOwner[_tokenId];
    require(
      tokenOwner == msg.sender
      || idToApproval[_tokenId] == msg.sender
      || ownerToOperators[tokenOwner][msg.sender],
      NOT_OWNER_APPROVED_OR_OPERATOR
    );
    _;
  }

  /**
   * @dev Guarantees that _tokenId is a valid Token.
   * @param _tokenId ID of the NFT to validate.
   */
  modifier validNFToken(
    uint256 _tokenId
  )
  {
    require(idToOwner[_tokenId] != address(0), NOT_VALID_NFT);
    _;
  }

  /**
   * @dev Contract constructor.
   */
  constructor()
  {
    supportedInterfaces[0x80ac58cd] = true; // ERC721
  }

  /**
   * @notice Throws unless `msg.sender` is the current owner, an authorized operator, or the
   * approved address for this NFT. Throws if `_from` is not the current owner. Throws if `_to` is
   * the zero address. Throws if `_tokenId` is not a valid NFT. When transfer is complete, this
   * function checks if `_to` is a smart contract (code size > 0). If so, it calls
   * `onERC721Received` on `_to` and throws if the return value is not
   * `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`.
   * @dev Transfers the ownership of an NFT from one address to another address. This function can
   * be changed to payable.
   * @param _from The current owner of the NFT.
   * @param _to The new owner.
   * @param _tokenId The NFT to transfer.
   * @param _data Additional data with no specified format, sent in call to `_to`.
   */
  function safeTransferFrom(
    address _from,
    address _to,
    uint256 _tokenId,
    bytes calldata _data
  )
    external
    override
  {
    _safeTransferFrom(_from, _to, _tokenId, _data);
  }

  /**
   * @notice This works identically to the other function with an extra data parameter, except this
   * function just sets data to "".
   * @dev Transfers the ownership of an NFT from one address to another address. This function can
   * be changed to payable.
   * @param _from The current owner of the NFT.
   * @param _to The new owner.
   * @param _tokenId The NFT to transfer.
   */
  function safeTransferFrom(
    address _from,
    address _to,
    uint256 _tokenId
  )
    external
    override
  {
    _safeTransferFrom(_from, _to, _tokenId, "");
  }

  /**
   * @notice The caller is responsible to confirm that `_to` is capable of receiving NFTs or else
   * they may be permanently lost.
   * @dev Throws unless `msg.sender` is the current owner, an authorized operator, or the approved
   * address for this NFT. Throws if `_from` is not the current owner. Throws if `_to` is the zero
   * address. Throws if `_tokenId` is not a valid NFT. This function can be changed to payable.
   * @param _from The current owner of the NFT.
   * @param _to The new owner.
   * @param _tokenId The NFT to transfer.
   */
  function transferFrom(
    address _from,
    address _to,
    uint256 _tokenId
  )
    external
    override
    canTransfer(_tokenId)
    validNFToken(_tokenId)
  {
    address tokenOwner = idToOwner[_tokenId];
    require(tokenOwner == _from, NOT_OWNER);
    require(_to != address(0), ZERO_ADDRESS);

    _transfer(_to, _tokenId);
  }

  /**
   * @notice The zero address indicates there is no approved address. Throws unless `msg.sender` is
   * the current NFT owner, or an authorized operator of the current owner.
   * @dev Set or reaffirm the approved address for an NFT. This function can be changed to payable.
   * @param _approved Address to be approved for the given NFT ID.
   * @param _tokenId ID of the token to be approved.
   */
  function approve(
    address _approved,
    uint256 _tokenId
  )
    external
    override
    canOperate(_tokenId)
    validNFToken(_tokenId)
  {
    address tokenOwner = idToOwner[_tokenId];
    require(_approved != tokenOwner, IS_OWNER);

    idToApproval[_tokenId] = _approved;
    emit Approval(tokenOwner, _approved, _tokenId);
  }

  /**
   * @notice This works even if sender doesn't own any tokens at the time.
   * @dev Enables or disables approval for a third party ("operator") to manage all of
   * `msg.sender`'s assets. It also emits the ApprovalForAll event.
   * @param _operator Address to add to the set of authorized operators.
   * @param _approved True if the operators is approved, false to revoke approval.
   */
  function setApprovalForAll(
    address _operator,
    bool _approved
  )
    external
    override
  {
    ownerToOperators[msg.sender][_operator] = _approved;
    emit ApprovalForAll(msg.sender, _operator, _approved);
  }

  /**
   * @dev Returns the number of NFTs owned by `_owner`. NFTs assigned to the zero address are
   * considered invalid, and this function throws for queries about the zero address.
   * @param _owner Address for whom to query the balance.
   * @return Balance of _owner.
   */
  function balanceOf(
    address _owner
  )
    external
    override
    view
    returns (uint256)
  {
    require(_owner != address(0), ZERO_ADDRESS);
    return _getOwnerNFTCount(_owner);
  }

  /**
   * @dev Returns the address of the owner of the NFT. NFTs assigned to the zero address are
   * considered invalid, and queries about them do throw.
   * @param _tokenId The identifier for an NFT.
   * @return _owner Address of _tokenId owner.
   */
  function ownerOf(
    uint256 _tokenId
  )
    external
    override
    view
    returns (address _owner)
  {
    _owner = idToOwner[_tokenId];
    require(_owner != address(0), NOT_VALID_NFT);
  }

  /**
   * @notice Throws if `_tokenId` is not a valid NFT.
   * @dev Get the approved address for a single NFT.
   * @param _tokenId ID of the NFT to query the approval of.
   * @return Address that _tokenId is approved for.
   */
  function getApproved(
    uint256 _tokenId
  )
    external
    override
    view
    validNFToken(_tokenId)
    returns (address)
  {
    return idToApproval[_tokenId];
  }

  /**
   * @dev Checks if `_operator` is an approved operator for `_owner`.
   * @param _owner The address that owns the NFTs.
   * @param _operator The address that acts on behalf of the owner.
   * @return True if approved for all, false otherwise.
   */
  function isApprovedForAll(
    address _owner,
    address _operator
  )
    external
    override
    view
    virtual
    returns (bool)
  {
    return ownerToOperators[_owner][_operator];
  }

  /**
   * @notice Does NO checks.
   * @dev Actually performs the transfer.
   * @param _to Address of a new owner.
   * @param _tokenId The NFT that is being transferred.
   */
  function _transfer(
    address _to,
    uint256 _tokenId
  )
    internal
    virtual
  {
    address from = idToOwner[_tokenId];
    _clearApproval(_tokenId);

    _removeNFToken(from, _tokenId);
    _addNFToken(_to, _tokenId);

    emit Transfer(from, _to, _tokenId);
  }

  /**
   * @notice This is an internal function which should be called from user-implemented external
   * mint function. Its purpose is to show and properly initialize data structures when using this
   * implementation.
   * @dev Mints a new NFT.
   * @param _to The address that will own the minted NFT.
   * @param _tokenId of the NFT to be minted by the msg.sender.
   */
  function _mint(
    address _to,
    uint256 _tokenId
  )
    internal
    virtual
  {
    require(_to != address(0), ZERO_ADDRESS);
    require(idToOwner[_tokenId] == address(0), NFT_ALREADY_EXISTS);

    _addNFToken(_to, _tokenId);

    emit Transfer(address(0), _to, _tokenId);
  }

  /**
   * @notice This is an internal function which should be called from user-implemented external burn
   * function. Its purpose is to show and properly initialize data structures when using this
   * implementation. Also, note that this burn implementation allows the minter to re-mint a burned
   * NFT.
   * @dev Burns a NFT.
   * @param _tokenId ID of the NFT to be burned.
   */
  function _burn(
    uint256 _tokenId
  )
    internal
    virtual
    validNFToken(_tokenId)
  {
    address tokenOwner = idToOwner[_tokenId];
    _clearApproval(_tokenId);
    _removeNFToken(tokenOwner, _tokenId);
    emit Transfer(tokenOwner, address(0), _tokenId);
  }

  /**
   * @notice Use and override this function with caution. Wrong usage can have serious consequences.
   * @dev Removes a NFT from owner.
   * @param _from Address from which we want to remove the NFT.
   * @param _tokenId Which NFT we want to remove.
   */
  function _removeNFToken(
    address _from,
    uint256 _tokenId
  )
    internal
    virtual
  {
    require(idToOwner[_tokenId] == _from, NOT_OWNER);
    ownerToNFTokenCount[_from] -= 1;
    delete idToOwner[_tokenId];
  }

  /**
   * @notice Use and override this function with caution. Wrong usage can have serious consequences.
   * @dev Assigns a new NFT to owner.
   * @param _to Address to which we want to add the NFT.
   * @param _tokenId Which NFT we want to add.
   */
  function _addNFToken(
    address _to,
    uint256 _tokenId
  )
    internal
    virtual
  {
    require(idToOwner[_tokenId] == address(0), NFT_ALREADY_EXISTS);

    idToOwner[_tokenId] = _to;
    ownerToNFTokenCount[_to] += 1;
  }

  /**
   * @dev Helper function that gets NFT count of owner. This is needed for overriding in enumerable
   * extension to remove double storage (gas optimization) of owner NFT count.
   * @param _owner Address for whom to query the count.
   * @return Number of _owner NFTs.
   */
  function _getOwnerNFTCount(
    address _owner
  )
    internal
    virtual
    view
    returns (uint256)
  {
    return ownerToNFTokenCount[_owner];
  }

  /**
   * @dev Actually perform the safeTransferFrom.
   * @param _from The current owner of the NFT.
   * @param _to The new owner.
   * @param _tokenId The NFT to transfer.
   * @param _data Additional data with no specified format, sent in call to `_to`.
   */
  function _safeTransferFrom(
    address _from,
    address _to,
    uint256 _tokenId,
    bytes memory _data
  )
    private
    canTransfer(_tokenId)
    validNFToken(_tokenId)
  {
    address tokenOwner = idToOwner[_tokenId];
    require(tokenOwner == _from, NOT_OWNER);
    require(_to != address(0), ZERO_ADDRESS);

    _transfer(_to, _tokenId);

    if (_to.isContract())
    {
      bytes4 retval = ERC721TokenReceiver(_to).onERC721Received(msg.sender, _from, _tokenId, _data);
      require(retval == MAGIC_ON_ERC721_RECEIVED, NOT_ABLE_TO_RECEIVE_NFT);
    }
  }

  /**
   * @dev Clears the current approval of a given NFT ID.
   * @param _tokenId ID of the NFT to be transferred.
   */
  function _clearApproval(
    uint256 _tokenId
  )
    private
  {
    delete idToApproval[_tokenId];
  }

}


/**
 * @dev Optional metadata extension for ERC-721 non-fungible token standard.
 * See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md.
 */
interface ERC721Metadata {

  /**
   * @dev Returns a descriptive name for a collection of NFTs in this contract.
   * @return _name Representing name.
   */
  function name()
    external
    view
    returns (string memory _name);

  /**
   * @dev Returns a abbreviated name for a collection of NFTs in this contract.
   * @return _symbol Representing symbol.
   */
  function symbol()
    external
    view
    returns (string memory _symbol);

  /**
   * @dev Returns a distinct Uniform Resource Identifier (URI) for a given asset. It Throws if
   * `_tokenId` is not a valid NFT. URIs are defined in RFC3986. The URI may point to a JSON file
   * that conforms to the "ERC721 Metadata JSON Schema".
   * @return URI of _tokenId.
   */
  function tokenURI(uint256 _tokenId)
    external
    view
    returns (string memory);

}


/**
 * @dev Optional metadata implementation for ERC-721 non-fungible token standard.
 */
contract NFTokenMetadata is
  NFToken,
  ERC721Metadata
{

  /**
   * @dev A descriptive name for a collection of NFTs.
   */
  string internal nftName;

  /**
   * @dev An abbreviated name for NFTokens.
   */
  string internal nftSymbol;

  /**
   * @dev Mapping from NFT ID to metadata uri.
   */
  mapping (uint256 => string) internal idToUri;

  /**
   * @notice When implementing this contract don't forget to set nftName and nftSymbol.
   * @dev Contract constructor.
   */
  constructor()
  {
    supportedInterfaces[0x5b5e139f] = true; // ERC721Metadata
  }

  /**
   * @dev Returns a descriptive name for a collection of NFTokens.
   * @return _name Representing name.
   */
  function name()
    external
    override
    view
    returns (string memory _name)
  {
    _name = nftName;
  }

  /**
   * @dev Returns an abbreviated name for NFTokens.
   * @return _symbol Representing symbol.
   */
  function symbol()
    external
    override
    view
    returns (string memory _symbol)
  {
    _symbol = nftSymbol;
  }

  /**
   * @dev A distinct URI (RFC 3986) for a given NFT.
   * @param _tokenId Id for which we want uri.
   * @return URI of _tokenId.
   */
  function tokenURI(
    uint256 _tokenId
  )
    external
    override
    view
    validNFToken(_tokenId)
    returns (string memory)
  {
    return _tokenURI(_tokenId);
  }

  /**
   * @notice This is an internal function that can be overriden if you want to implement a different
   * way to generate token URI.
   * @param _tokenId Id for which we want uri.
   * @return URI of _tokenId.
   */
  function _tokenURI(
    uint256 _tokenId
  )
    internal
    virtual
    view
    returns (string memory)
  {
    return idToUri[_tokenId];
  }

  /**
   * @notice This is an internal function which should be called from user-implemented external
   * burn function. Its purpose is to show and properly initialize data structures when using this
   * implementation. Also, note that this burn implementation allows the minter to re-mint a burned
   * NFT.
   * @dev Burns a NFT.
   * @param _tokenId ID of the NFT to be burned.
   */
  function _burn(
    uint256 _tokenId
  )
    internal
    override
    virtual
  {
    super._burn(_tokenId);

    delete idToUri[_tokenId];
  }

  /**
   * @notice This is an internal function which should be called from user-implemented external
   * function. Its purpose is to show and properly initialize data structures when using this
   * implementation.
   * @dev Set a distinct URI (RFC 3986) for a given NFT ID.
   * @param _tokenId Id for which we want URI.
   * @param _uri String representing RFC 3986 URI.
   */
  function _setTokenUri(
    uint256 _tokenId,
    string memory _uri
  )
    internal
    validNFToken(_tokenId)
  {
    idToUri[_tokenId] = _uri;
  }

}


/**
 * @dev Optional enumeration extension for ERC-721 non-fungible token standard.
 * See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md.
 */
interface ERC721Enumerable {

  /**
   * @dev Returns a count of valid NFTs tracked by this contract, where each one of them has an
   * assigned and queryable owner not equal to the zero address.
   * @return Total supply of NFTs.
   */
  function totalSupply()
    external
    view
    returns (uint256);

  /**
   * @dev Returns the token identifier for the `_index`th NFT. Sort order is not specified.
   * @param _index A counter less than `totalSupply()`.
   * @return Token id.
   */
  function tokenByIndex(
    uint256 _index
  )
    external
    view
    returns (uint256);

  /**
   * @dev Returns the token identifier for the `_index`th NFT assigned to `_owner`. Sort order is
   * not specified. It throws if `_index` >= `balanceOf(_owner)` or if `_owner` is the zero address,
   * representing invalid NFTs.
   * @param _owner An address where we are interested in NFTs owned by them.
   * @param _index A counter less than `balanceOf(_owner)`.
   * @return Token id.
   */
  function tokenOfOwnerByIndex(
    address _owner,
    uint256 _index
  )
    external
    view
    returns (uint256);

}


/**
 * @dev Optional enumeration implementation for ERC-721 non-fungible token standard.
 */
contract NFTokenEnumerable is
  NFToken,
  ERC721Enumerable
{

  /**
   * @dev List of revert message codes. Implementing dApp should handle showing the correct message.
   * Based on 0xcert framework error codes.
   */
  string constant INVALID_INDEX = "005007";

  /**
   * @dev Array of all NFT IDs.
   */
  uint256[] internal tokens;

  /**
   * @dev Mapping from token ID to its index in global tokens array.
   */
  mapping(uint256 => uint256) internal idToIndex;

  /**
   * @dev Mapping from owner to list of owned NFT IDs.
   */
  mapping(address => uint256[]) internal ownerToIds;

  /**
   * @dev Mapping from NFT ID to its index in the owner tokens list.
   */
  mapping(uint256 => uint256) internal idToOwnerIndex;

  /**
   * @dev Contract constructor.
   */
  constructor()
  {
    supportedInterfaces[0x780e9d63] = true; // ERC721Enumerable
  }

  /**
   * @dev Returns the count of all existing NFTokens.
   * @return Total supply of NFTs.
   */
  function totalSupply()
    external
    override
    view
    returns (uint256)
  {
    return tokens.length;
  }

  /**
   * @dev Returns NFT ID by its index.
   * @param _index A counter less than `totalSupply()`.
   * @return Token id.
   */
  function tokenByIndex(
    uint256 _index
  )
    external
    override
    view
    returns (uint256)
  {
    require(_index < tokens.length, INVALID_INDEX);
    return tokens[_index];
  }

  /**
   * @dev returns the n-th NFT ID from a list of owner's tokens.
   * @param _owner Token owner's address.
   * @param _index Index number representing n-th token in owner's list of tokens.
   * @return Token id.
   */
  function tokenOfOwnerByIndex(
    address _owner,
    uint256 _index
  )
    external
    override
    view
    returns (uint256)
  {
    require(_index < ownerToIds[_owner].length, INVALID_INDEX);
    return ownerToIds[_owner][_index];
  }

  /**
   * @notice This is an internal function which should be called from user-implemented external
   * mint function. Its purpose is to show and properly initialize data structures when using this
   * implementation.
   * @dev Mints a new NFT.
   * @param _to The address that will own the minted NFT.
   * @param _tokenId of the NFT to be minted by the msg.sender.
   */
  function _mint(
    address _to,
    uint256 _tokenId
  )
    internal
    override
    virtual
  {
    super._mint(_to, _tokenId);
    tokens.push(_tokenId);
    idToIndex[_tokenId] = tokens.length - 1;
  }

  /**
   * @notice This is an internal function which should be called from user-implemented external
   * burn function. Its purpose is to show and properly initialize data structures when using this
   * implementation. Also, note that this burn implementation allows the minter to re-mint a burned
   * NFT.
   * @dev Burns a NFT.
   * @param _tokenId ID of the NFT to be burned.
   */
  function _burn(
    uint256 _tokenId
  )
    internal
    override
    virtual
  {
    super._burn(_tokenId);

    uint256 tokenIndex = idToIndex[_tokenId];
    uint256 lastTokenIndex = tokens.length - 1;
    uint256 lastToken = tokens[lastTokenIndex];

    tokens[tokenIndex] = lastToken;

    tokens.pop();
    // This wastes gas if you are burning the last token but saves a little gas if you are not.
    idToIndex[lastToken] = tokenIndex;
    idToIndex[_tokenId] = 0;
  }

  /**
   * @notice Use and override this function with caution. Wrong usage can have serious consequences.
   * @dev Removes a NFT from an address.
   * @param _from Address from wich we want to remove the NFT.
   * @param _tokenId Which NFT we want to remove.
   */
  function _removeNFToken(
    address _from,
    uint256 _tokenId
  )
    internal
    override
    virtual
  {
    require(idToOwner[_tokenId] == _from, NOT_OWNER);
    delete idToOwner[_tokenId];

    uint256 tokenToRemoveIndex = idToOwnerIndex[_tokenId];
    uint256 lastTokenIndex = ownerToIds[_from].length - 1;

    if (lastTokenIndex != tokenToRemoveIndex)
    {
      uint256 lastToken = ownerToIds[_from][lastTokenIndex];
      ownerToIds[_from][tokenToRemoveIndex] = lastToken;
      idToOwnerIndex[lastToken] = tokenToRemoveIndex;
    }

    ownerToIds[_from].pop();
  }

  /**
   * @notice Use and override this function with caution. Wrong usage can have serious consequences.
   * @dev Assigns a new NFT to an address.
   * @param _to Address to wich we want to add the NFT.
   * @param _tokenId Which NFT we want to add.
   */
  function _addNFToken(
    address _to,
    uint256 _tokenId
  )
    internal
    override
    virtual
  {
    require(idToOwner[_tokenId] == address(0), NFT_ALREADY_EXISTS);
    idToOwner[_tokenId] = _to;

    ownerToIds[_to].push(_tokenId);
    idToOwnerIndex[_tokenId] = ownerToIds[_to].length - 1;
  }

  /**
   * @dev Helper function that gets NFT count of owner. This is needed for overriding in enumerable
   * extension to remove double storage(gas optimization) of owner NFT count.
   * @param _owner Address for whom to query the count.
   * @return Number of _owner NFTs.
   */
  function _getOwnerNFTCount(
    address _owner
  )
    internal
    override
    virtual
    view
    returns (uint256)
  {
    return ownerToIds[_owner].length;
  }
}

contract Ownable {

  /**
   * @dev Error constants.
   */
  string public constant NOT_CURRENT_OWNER = "018001";
  string public constant CANNOT_TRANSFER_TO_ZERO_ADDRESS = "018002";
  string public constant NOT_CURRENT_MANAGER = "018003";

  address public owner;
  mapping(address=>bool) public Manager;


  event OwnershipTransferred(
    address indexed previousOwner,
    address indexed newOwner
  );


  constructor()
    public
  {
    owner = msg.sender;
  }
  modifier onlyOwner()
  {
    require(msg.sender == owner, NOT_CURRENT_OWNER);
    _;
  }
  
  modifier onlyManager()    
  {
    require(Manager[msg.sender], NOT_CURRENT_MANAGER);
    _;
  }

  function addManager(address _maddr) public onlyOwner{
      Manager[_maddr] = true;
  }
  
  function delManager(address _maddr) public onlyOwner{
      Manager[_maddr] = false;
  }
  function transferOwnership(
    address _newOwner
  )
    public
    onlyOwner
  {
    require(_newOwner != address(0), CANNOT_TRANSFER_TO_ZERO_ADDRESS);
    emit OwnershipTransferred(owner, _newOwner);
    owner = _newOwner;
  }

}


// nft + enumerable + base_url
/**
 * @dev This is an example contract implementation of NFToken with enumerable and metadata
 * extensions.
 */
library Address {
    function isContract(address account) internal view returns (bool) {
        bytes32 codehash;
        bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
        // solhint-disable-next-line no-inline-assembly
        assembly { codehash := extcodehash(account) }
        return (codehash != 0x0 && codehash != accountHash);
    }
    // function toPayable(address account) internal pure returns (address payable) {
    //     return address(uint160(account));
    // }
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-call-value
        (bool success, ) =  recipient.call{value : amount}("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }
}

library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     *
     * _Available since v2.4.0._
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;
        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }

}


contract OwnableDelegateProxy {}

contract ProxyRegistry {
    mapping(address => OwnableDelegateProxy) public proxies;
}

contract NFTokenCon is
  NFTokenEnumerable,
  NFTokenMetadata,
  Ownable
{

    using SafeMath for uint256;
    string public baseURI; // 
    uint256 public constant maxAmount = 5555; 
    uint256 public soldBoxCount;
    uint256 public perUserLimit = 2; 
    uint256 boxIndex = 10000000;

    mapping(address => bool) public whiteMap;
    mapping(address => uint8) public userBuyCount;
    string boxUrl = "0";

    // 初始价格
    uint256 public price = 8900000000000000;
    // 初始收币地址
    address payable collect = payable(0xe52Ab043711f90596970a409518cAD9a53cEf803);
    uint256 public startOpenBox = 1694534400; 

    address private openSeaRegistryAddress = 0xa5409ec958C83C3f309868babACA7c86DCB077c1;
    uint256 public  openBoxAmount = 5555; 
    mapping(uint256 => uint256) movedCards;



  constructor()
  {
    nftName = "Bedans";
    nftSymbol = "Bedans";
    baseURI = "https://ipfs.io/ipfs/QmfGk943RQAD4yas8B2uQLNEWVXxZYQK7gPvZbNUzbqLvE/";
  }



  function setWhite(address addr,bool flag) public onlyOwner{
    require(whiteMap[addr] != flag,"is set");
    whiteMap[addr] = flag;
  }


  function setWhiteList(address[] memory list,bool flag) public onlyOwner{
    for(uint256 i;i<list.length;i++){
        whiteMap[list[i]] = flag;
    }
  }



  function setPrice(uint256 _price) public onlyOwner{
    price = _price;
  }


  function setPerUserLimit(uint256 _limit) public onlyOwner{
    perUserLimit = _limit;
  }
  


  function setCollectAddr(address payable addr) public onlyOwner{
    collect = addr;
  }

  function setStartOpenBox(uint256 time) public onlyOwner{
    startOpenBox = time;
  }


  function setBaseUrl(string calldata _url) public onlyOwner{
    baseURI = _url;
  }



  receive() external payable {}

  fallback() external payable {}

  function buyBox(uint8 num) public payable{
      require(num>=1 || num<=2 ,"err num");
      soldBoxCount += num;

      require(soldBoxCount<=maxAmount,"no box left");
      require(userBuyCount[msg.sender] + num <=perUserLimit,"over limit");

      uint256 fee = price.mul(num);
      require(msg.value>=fee,"err amount");
      (bool sent,) = collect.call{value: msg.value}("");
      require(sent, "Failed to send Ether");
      
      userBuyCount[msg.sender] = userBuyCount[msg.sender] + num;

      for (uint8 i;i<num;i++){
        boxIndex++;
        super._mint(msg.sender, boxIndex);
        super._setTokenUri(boxIndex, boxUrl);
      }
    
  }


  function whiteBuyBox() public{
    require(whiteMap[msg.sender],"not white");
    soldBoxCount++;
    require(soldBoxCount<=maxAmount,"no box left");
    require(userBuyCount[msg.sender]<perUserLimit,"over limit");
    userBuyCount[msg.sender] = userBuyCount[msg.sender] + 1;

    boxIndex++;
    super._mint(msg.sender, boxIndex);
    super._setTokenUri(boxIndex, boxUrl);
    whiteMap[msg.sender] = false;
  }
 

  function openBox(uint256 _tokenId) public{
    require(block.timestamp>=startOpenBox,"not start");

    require(_tokenId>10000000,"err tokenid");
    require(idToOwner[_tokenId] == msg.sender,"err owner");
    super._burn(_tokenId);

    uint256 index = draw();
    super._mint(msg.sender, index);
    super._setTokenUri(index, _uint2str(index));
  }

  function getRandom(uint256 k) private view returns(uint256) {
    return uint256(keccak256(abi.encodePacked(
                (block.timestamp).add
                (block.difficulty).add
                (block.gaslimit).add
                ((uint256(keccak256(abi.encodePacked(msg.sender)))) / (block.timestamp)).add
                (block.number)
            ))) % (k);
  }


  function cardAt(uint256 i) private view returns (uint256) {
      if (movedCards[i]>0) {
          return movedCards[i];
      } else {
          return i;
      }
  }

  function draw() private returns (uint256) {
      require(openBoxAmount > 0, "All cards drawn");
      // Pick i
      uint256 i = getRandom(openBoxAmount);
      // Pick the ith card in the "deck"
      uint256 outCard = cardAt(i);

      // Move the last card in the deck into position i
      movedCards[i] = cardAt(openBoxAmount - 1);
      movedCards[openBoxAmount - 1] = 0;
      openBoxAmount -= 1;

      return outCard;
  }




  function setOpenSeaRegistryAddress(address a) public onlyOwner {
      openSeaRegistryAddress = a;
  }

  
  function isApprovedForAll(address owner, address operator) public override view returns (bool) {
      ProxyRegistry openSeaRegistry = ProxyRegistry(openSeaRegistryAddress);

      if (address(openSeaRegistry.proxies(owner)) == operator) {
          return true;
      }

      return ownerToOperators[owner][operator];
  }


  function _transfer(
    address _to,
    uint256 _tokenId
  )
    internal
    override{
      super._transfer(_to,_tokenId);

    }



  /**
   * @dev Removes a NFT from owner.
   * @param _tokenId Which NFT we want to remove.
   */
  function burn(
    uint256 _tokenId
  )
    external
    onlyOwner
  {
    super._burn(_tokenId);
  }

  /**
   * @dev Mints a new NFT.
   * @notice This is an internal function which should be called from user-implemented external
   * mint function. Its purpose is to show and properly initialize data structures when using this
   * implementation.
   * @param _to The address that will own the minted NFT.
   * @param _tokenId of the NFT to be minted by the msg.sender.
   */
  function _mint(
    address _to,
    uint256 _tokenId
  )
    internal
    override(NFToken, NFTokenEnumerable)
    virtual
  {
    NFTokenEnumerable._mint(_to, _tokenId);
  }


  /**
   * @dev Burns a NFT.
   * @notice This is an internal function which should be called from user-implemented external
   * burn function. Its purpose is to show and properly initialize data structures when using this
   * implementation. Also, note that this burn implementation allows the minter to re-mint a burned
   * NFT.
   * @param _tokenId ID of the NFT to be burned.
   */
  function _burn(
    uint256 _tokenId
  )
    internal
    override(NFTokenMetadata, NFTokenEnumerable)
    virtual
  {
    NFTokenEnumerable._burn(_tokenId);
    if (bytes(idToUri[_tokenId]).length != 0)
    {
      delete idToUri[_tokenId];
    }
  }

  /**
   * @notice Use and override this function with caution. Wrong usage can have serious consequences.
   * @dev Removes a NFT from an address.
   * @param _from Address from wich we want to remove the NFT.
   * @param _tokenId Which NFT we want to remove.
   */
  function _removeNFToken(
    address _from,
    uint256 _tokenId
  )
    internal
    override(NFToken, NFTokenEnumerable)
  {
    NFTokenEnumerable._removeNFToken(_from, _tokenId);
  }

  /**
   * @notice Use and override this function with caution. Wrong usage can have serious consequences.
   * @dev Assigns a new NFT to an address.
   * @param _to Address to wich we want to add the NFT.
   * @param _tokenId Which NFT we want to add.
   */
  function _addNFToken(
    address _to,
    uint256 _tokenId
  )
    internal
    override(NFToken, NFTokenEnumerable)
  {
    NFTokenEnumerable._addNFToken(_to, _tokenId);
  }

   /**
   * @dev Helper function that gets NFT count of owner. This is needed for overriding in enumerable
   * extension to remove double storage(gas optimization) of owner nft count.
   * @param _owner Address for whom to query the count.
   * @return Number of _owner NFTs.
   */
  function _getOwnerNFTCount(
    address _owner
  )
    internal
    override(NFToken, NFTokenEnumerable)
    view
    returns (uint256)
  {
    return NFTokenEnumerable._getOwnerNFTCount(_owner);
  }

  /**
   * @dev A distinct URI (RFC 3986) for a given NFT.
   * @param _tokenId Id for which we want uri.
   * @return URI of _tokenId.
   */
  function _tokenURI(
    uint256 _tokenId
  )
    internal
    override
    view
    returns (string memory)
  {
    return bytes(baseURI).length > 0 ? string(abi.encodePacked(baseURI, super._tokenURI(_tokenId))) : "";
  }

  /**
   * @dev Helper function that changes uint to string representation.
   * @return str String representation.
   */
  function _uint2str(
    uint256 _i
  )
    internal
    pure
    returns (string memory str)
  {
    if (_i == 0) {
      return "0";
    }
    uint256 j = _i;
    uint256 length;
    while (j != 0) {
      length++;
      j /= 10;
    }
    bytes memory bstr = new bytes(length);
    uint256 k = length;
    j = _i;
    while (j != 0) {
      bstr[--k] = bytes1(uint8(48 + j % 10));
      j /= 10;
    }
    str = string(bstr);
  }

}