// Vulnerability label: TD1
// pragma solidity 0.6.0;


pragma solidity ^0.4.24;

/*

*Please accept this GSG-Loyalty Plan as a token of my appreciation.
*Through sharing of knowledge we can uplift the world.
*The individuals behind the creation of this contract wish you a successful journey.
*With God behind us, we will create our own futures.
*
*Thank you Shihad for your expertise.
*
*This is a tribute to Jeremy, Marley, and Aria. I pray this project provides for you for generations -  4 September 2020 
*Your Dad, LuckyRico AKA djSpade1 AKA GOLDBACKERS
*/




/**
 * @title IERC165
 * @dev https://github.com/ethereum/EIPs/blob/master/EIPS/eip-165.md
 */
interface IERC165 {

  /**
   * @notice Query if a contract implements an interface
   * @param interfaceId The interface identifier, as specified in ERC-165
   * @dev Interface identification is specified in ERC-165. This function
   * uses less than 30,000 gas.
   */
  function supportsInterface(bytes4 interfaceId)
    external
    view
    returns (bool);
}

/**
 * @title ERC721 Non-Fungible Token Standard basic interface
 * @dev see https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
 */
contract IERC721 is IERC165 {

  event Transfer(
    address indexed from,
    address indexed to,
    uint256 indexed tokenId
  );
  event Approval(
    address indexed owner,
    address indexed approved,
    uint256 indexed tokenId
  );
  event ApprovalForAll(
    address indexed owner,
    address indexed operator,
    bool approved
  );

  function balanceOf(address owner) public view returns (uint256 balance);
  function ownerOf(uint256 tokenId) public view returns (address owner);

  function approve(address to, uint256 tokenId) public;
  function getApproved(uint256 tokenId)
    public view returns (address operator);

  function setApprovalForAll(address operator, bool _approved) public;
  function isApprovedForAll(address owner, address operator)
    public view returns (bool);

  function transferFrom(address from, address to, uint256 tokenId) public;
  function safeTransferFrom(address from, address to, uint256 tokenId)
    public;

  function safeTransferFrom(
    address from,
    address to,
    uint256 tokenId,
    bytes data
  )
    public;
}

/**
 * @title ERC-721 Non-Fungible Token Standard, optional enumeration extension
 * @dev See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
 */
contract IERC721Enumerable is IERC721 {
  function totalSupply() public view returns (uint256);
  function tokenOfOwnerByIndex(
    address owner,
    uint256 index
  )
    public
    view
    returns (uint256 tokenId);

  function tokenByIndex(uint256 index) public view returns (uint256);
}

/**
 * @title ERC721 token receiver interface
 * @dev Interface for any contract that wants to support safeTransfers
 * from ERC721 asset contracts.
 */
contract IERC721Receiver {
  /**
   * @notice Handle the receipt of an NFT
   * @dev The ERC721 smart contract calls this function on the recipient
   * after a `safeTransfer`. This function MUST return the function selector,
   * otherwise the caller will revert the transaction. The selector to be
   * returned can be obtained as `this.onERC721Received.selector`. This
   * function MAY throw to revert and reject the transfer.
   * Note: the ERC721 contract address is always the message sender.
   * @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 `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
   */
  function onERC721Received(
    address operator,
    address from,
    uint256 tokenId,
    bytes data
  )
    public
    returns(bytes4);
}

/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {

  /**
  * @dev Multiplies two numbers, throws on overflow.
  */
  function mul(uint256 a, uint256 b) internal pure returns (uint256 c) {
    // Gas optimization: this is cheaper than asserting 'a' not being zero, but the
    // benefit is lost if 'b' is also tested.
    // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
    if (a == 0) {
      return 0;
    }

    c = a * b;
    assert(c / a == b);
    return c;
  }

  /**
  * @dev Integer division of two numbers, truncating the quotient.
  */
  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    // assert(b > 0); // Solidity automatically throws when dividing by 0
    // uint256 c = a / b;
    // assert(a == b * c + a % b); // There is no case in which this doesn't hold
    return a / b;
  }

  /**
  * @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
  */
  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    assert(b <= a);
    return a - b;
  }

  /**
  * @dev Adds two numbers, throws on overflow.
  */
  function add(uint256 a, uint256 b) internal pure returns (uint256 c) {
    c = a + b;
    assert(c >= a);
    return c;
  }
}

/**
 * Utility library of inline functions on addresses
 */
library Address {

  /**
   * Returns whether the target address is a contract
   * @dev This function will return false if invoked during the constructor of a contract,
   *  as the code is not actually created until after the constructor finishes.
   * @param addr address to check
   * @return whether the target address is a contract
   */
  function isContract(address addr) internal view returns (bool) {
    uint256 size;
    // XXX Currently there is no better way to check if there is a contract in an address
    // than to check the size of the code at that address.
    // See https://ethereum.stackexchange.com/a/14016/36603
    // for more details about how this works.
    // TODO Check this again before the Serenity release, because all addresses will be
    // contracts then.
    // solium-disable-next-line security/no-inline-assembly
    assembly { size := extcodesize(addr) }
    return size > 0;
  }

}

/**
 * @title ERC165
 * @author Matt Condon (@shrugs)
 * @dev Implements ERC165 using a lookup table.
 */
contract ERC165 is IERC165 {

  bytes4 private constant _InterfaceId_ERC165 = 0x01ffc9a7;
  /**
   * 0x01ffc9a7 ===
   *   bytes4(keccak256('supportsInterface(bytes4)'))
   */

  /**
   * @dev a mapping of interface id to whether or not it's supported
   */
  mapping(bytes4 => bool) private _supportedInterfaces;

  /**
   * @dev A contract implementing SupportsInterfaceWithLookup
   * implement ERC165 itself
   */
  constructor()
    internal
  {
    _registerInterface(_InterfaceId_ERC165);
  }

  /**
   * @dev implement supportsInterface(bytes4) using a lookup table
   */
  function supportsInterface(bytes4 interfaceId)
    external
    view
    returns (bool)
  {
    return _supportedInterfaces[interfaceId];
  }

  /**
   * @dev internal method for registering an interface
   */
  function _registerInterface(bytes4 interfaceId)
    internal
  {
    require(interfaceId != 0xffffffff);
    _supportedInterfaces[interfaceId] = true;
  }
}

/**
 * @title ERC721 Non-Fungible Token Standard basic implementation
 * @dev see https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
 */
contract ERC721 is ERC165, IERC721 {

  using SafeMath for uint256;
  using Address for address;

  // Equals to `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
  // which can be also obtained as `IERC721Receiver(0).onERC721Received.selector`
  bytes4 private constant _ERC721_RECEIVED = 0x150b7a02;

  // Mapping from token ID to owner
  mapping (uint256 => address) private _tokenOwner;

  // Mapping from token ID to approved address
  mapping (uint256 => address) private _tokenApprovals;

  // Mapping from owner to number of owned token
  mapping (address => uint256) private _ownedTokensCount;

  // Mapping from owner to operator approvals
  mapping (address => mapping (address => bool)) private _operatorApprovals;

  bytes4 private constant _InterfaceId_ERC721 = 0x80ac58cd;
  /*
   * 0x80ac58cd ===
   *   bytes4(keccak256('balanceOf(address)')) ^
   *   bytes4(keccak256('ownerOf(uint256)')) ^
   *   bytes4(keccak256('approve(address,uint256)')) ^
   *   bytes4(keccak256('getApproved(uint256)')) ^
   *   bytes4(keccak256('setApprovalForAll(address,bool)')) ^
   *   bytes4(keccak256('isApprovedForAll(address,address)')) ^
   *   bytes4(keccak256('transferFrom(address,address,uint256)')) ^
   *   bytes4(keccak256('safeTransferFrom(address,address,uint256)')) ^
   *   bytes4(keccak256('safeTransferFrom(address,address,uint256,bytes)'))
   */

  constructor()
    public
  {
    // register the supported interfaces to conform to ERC721 via ERC165
    _registerInterface(_InterfaceId_ERC721);
  }

  /**
   * @dev Gets the balance of the specified address
   * @param owner address to query the balance of
   * @return uint256 representing the amount owned by the passed address
   */
  function balanceOf(address owner) public view returns (uint256) {
    require(owner != address(0));
    return _ownedTokensCount[owner];
  }

  /**
   * @dev Gets the owner of the specified token ID
   * @param tokenId uint256 ID of the token to query the owner of
   * @return owner address currently marked as the owner of the given token ID
   */
  function ownerOf(uint256 tokenId) public view returns (address) {
    address owner = _tokenOwner[tokenId];
    require(owner != address(0));
    return owner;
  }

  /**
   * @dev Approves another address to transfer the given token ID
   * The zero address indicates there is no approved address.
   * There can only be one approved address per token at a given time.
   * Can only be called by the token owner or an approved operator.
   * @param to address to be approved for the given token ID
   * @param tokenId uint256 ID of the token to be approved
   */
  function approve(address to, uint256 tokenId) public {
    address owner = ownerOf(tokenId);
    require(to != owner);
    require(msg.sender == owner || isApprovedForAll(owner, msg.sender));

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

  /**
   * @dev Gets the approved address for a token ID, or zero if no address set
   * Reverts if the token ID does not exist.
   * @param tokenId uint256 ID of the token to query the approval of
   * @return address currently approved for the given token ID
   */
  function getApproved(uint256 tokenId) public view returns (address) {
    require(_exists(tokenId));
    return _tokenApprovals[tokenId];
  }

  /**
   * @dev Sets or unsets the approval of a given operator
   * An operator is allowed to transfer all tokens of the sender on their behalf
   * @param to operator address to set the approval
   * @param approved representing the status of the approval to be set
   */
  function setApprovalForAll(address to, bool approved) public {
    require(to != msg.sender);
    _operatorApprovals[msg.sender][to] = approved;
    emit ApprovalForAll(msg.sender, to, approved);
  }

  /**
   * @dev Tells whether an operator is approved by a given owner
   * @param owner owner address which you want to query the approval of
   * @param operator operator address which you want to query the approval of
   * @return bool whether the given operator is approved by the given owner
   */
  function isApprovedForAll(
    address owner,
    address operator
  )
    public
    view
    returns (bool)
  {
    return _operatorApprovals[owner][operator];
  }

  /**
   * @dev Transfers the ownership of a given token ID to another address
   * Usage of this method is discouraged, use `safeTransferFrom` whenever possible
   * Requires the msg sender to be the owner, approved, or operator
   * @param from current owner of the token
   * @param to address to receive the ownership of the given token ID
   * @param tokenId uint256 ID of the token to be transferred
  */
  function transferFrom(
    address from,
    address to,
    uint256 tokenId
  )
    public
  {
    require(_isApprovedOrOwner(msg.sender, tokenId));
    require(to != address(0));

    _clearApproval(from, tokenId);
    _removeTokenFrom(from, tokenId);
    _addTokenTo(to, tokenId);

    emit Transfer(from, to, tokenId);
  }

  /**
   * @dev Safely transfers the ownership of a given token ID to another address
   * If the target address is a contract, it must implement `onERC721Received`,
   * which is called upon a safe transfer, and return the magic value
   * `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`; otherwise,
   * the transfer is reverted.
   *
   * Requires the msg sender to be the owner, approved, or operator
   * @param from current owner of the token
   * @param to address to receive the ownership of the given token ID
   * @param tokenId uint256 ID of the token to be transferred
  */
  function safeTransferFrom(
    address from,
    address to,
    uint256 tokenId
  )
    public
  {
    // solium-disable-next-line arg-overflow
    safeTransferFrom(from, to, tokenId, "");
  }

  /**
   * @dev Safely transfers the ownership of a given token ID to another address
   * If the target address is a contract, it must implement `onERC721Received`,
   * which is called upon a safe transfer, and return the magic value
   * `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`; otherwise,
   * the transfer is reverted.
   * Requires the msg sender to be the owner, approved, or operator
   * @param from current owner of the token
   * @param to address to receive the ownership of the given token ID
   * @param tokenId uint256 ID of the token to be transferred
   * @param _data bytes data to send along with a safe transfer check
   */
  function safeTransferFrom(
    address from,
    address to,
    uint256 tokenId,
    bytes _data
  )
    public
  {
    transferFrom(from, to, tokenId);
    // solium-disable-next-line arg-overflow
    require(_checkOnERC721Received(from, to, tokenId, _data));
  }

  /**
   * @dev Returns whether the specified token exists
   * @param tokenId uint256 ID of the token to query the existence of
   * @return whether the token exists
   */
  function _exists(uint256 tokenId) internal view returns (bool) {
    address owner = _tokenOwner[tokenId];
    return owner != address(0);
  }

  /**
   * @dev Returns whether the given spender can transfer a given token ID
   * @param spender address of the spender to query
   * @param tokenId uint256 ID of the token to be transferred
   * @return bool whether the msg.sender is approved for the given token ID,
   *  is an operator of the owner, or is the owner of the token
   */
  function _isApprovedOrOwner(
    address spender,
    uint256 tokenId
  )
    internal
    view
    returns (bool)
  {
    address owner = ownerOf(tokenId);
    // Disable solium check because of
    // https://github.com/duaraghav8/Solium/issues/175
    // solium-disable-next-line operator-whitespace
    return (
      spender == owner ||
      getApproved(tokenId) == spender ||
      isApprovedForAll(owner, spender)
    );
  }

  /**
   * @dev Internal function to mint a new token
   * Reverts if the given token ID already exists
   * @param to The address that will own the minted token
   * @param tokenId uint256 ID of the token to be minted by the msg.sender
   */
  function _mint(address to, uint256 tokenId) internal {
    require(to != address(0));
  
    _addTokenTo(to, tokenId);
    emit Transfer(address(0), to, tokenId);
  }

  /**
   * @dev Internal function to burn a specific token
   * Reverts if the token does not exist
   * @param tokenId uint256 ID of the token being burned by the msg.sender
   */
  function _burn(address owner, uint256 tokenId) internal {
    _clearApproval(owner, tokenId);
    _removeTokenFrom(owner, tokenId);
    emit Transfer(owner, address(0), tokenId);
  }

  /**
   * @dev Internal function to add a token ID to the list of a given address
   * Note that this function is left internal to make ERC721Enumerable possible, but is not
   * intended to be called by custom derived contracts: in particular, it emits no Transfer event.
   * @param to address representing the new owner of the given token ID
   * @param tokenId uint256 ID of the token to be added to the tokens list of the given address
   */
  function _addTokenTo(address to, uint256 tokenId) internal {
    require(_tokenOwner[tokenId] == address(0));
    _tokenOwner[tokenId] = to;
    _ownedTokensCount[to] = _ownedTokensCount[to].add(1);
  }

  /**
   * @dev Internal function to remove a token ID from the list of a given address
   * Note that this function is left internal to make ERC721Enumerable possible, but is not
   * intended to be called by custom derived contracts: in particular, it emits no Transfer event,
   * and doesn't clear approvals.
   * @param from address representing the previous owner of the given token ID
   * @param tokenId uint256 ID of the token to be removed from the tokens list of the given address
   */
  function _removeTokenFrom(address from, uint256 tokenId) internal {
    require(ownerOf(tokenId) == from);
    _ownedTokensCount[from] = _ownedTokensCount[from].sub(1);
    _tokenOwner[tokenId] = address(0);
  }

  /**
   * @dev Internal function to invoke `onERC721Received` on a target address
   * The call is not executed if the target address is not a contract
   * @param from address representing the previous owner of the given token ID
   * @param to target address that will receive the tokens
   * @param tokenId uint256 ID of the token to be transferred
   * @param _data bytes optional data to send along with the call
   * @return whether the call correctly returned the expected magic value
   */
  function _checkOnERC721Received(
    address from,
    address to,
    uint256 tokenId,
    bytes _data
  )
    internal
    returns (bool)
  {
    if (!to.isContract()) {
      return true;
    }
    bytes4 retval = IERC721Receiver(to).onERC721Received(
      msg.sender, from, tokenId, _data);
    return (retval == _ERC721_RECEIVED);
  }

  /**
   * @dev Private function to clear current approval of a given token ID
   * Reverts if the given address is not indeed the owner of the token
   * @param owner owner of the token
   * @param tokenId uint256 ID of the token to be transferred
   */
  function _clearApproval(address owner, uint256 tokenId) private {
    require(ownerOf(tokenId) == owner);
    if (_tokenApprovals[tokenId] != address(0)) {
      _tokenApprovals[tokenId] = address(0);
    }
  }
}

contract ERC721Enumerable is ERC165, ERC721, IERC721Enumerable {
  // Mapping from owner to list of owned token IDs
  mapping(address => uint256[]) private _ownedTokens;

  // Mapping from token ID to index of the owner tokens list
  mapping(uint256 => uint256) private _ownedTokensIndex;

  // Array with all token ids, used for enumeration
  uint256[] private _allTokens;

  // Mapping from token id to position in the allTokens array
  mapping(uint256 => uint256) private _allTokensIndex;

  bytes4 private constant _InterfaceId_ERC721Enumerable = 0x780e9d63;
  /**
   * 0x780e9d63 ===
   *   bytes4(keccak256('totalSupply()')) ^
   *   bytes4(keccak256('tokenOfOwnerByIndex(address,uint256)')) ^
   *   bytes4(keccak256('tokenByIndex(uint256)'))
   */

  /**
   * @dev Constructor function
   */
  constructor() public {
    // register the supported interface to conform to ERC721 via ERC165
    _registerInterface(_InterfaceId_ERC721Enumerable);
  }

  /**
   * @dev Gets the token ID at a given index of the tokens list of the requested owner
   * @param owner address owning the tokens list to be accessed
   * @param index uint256 representing the index to be accessed of the requested tokens list
   * @return uint256 token ID at the given index of the tokens list owned by the requested address
   */
  function tokenOfOwnerByIndex(
    address owner,
    uint256 index
  )
    public
    view
    returns (uint256)
  {
    require(index < balanceOf(owner));
    return _ownedTokens[owner][index];
  }

  /**
   * @dev Gets the total amount of tokens stored by the contract
   * @return uint256 representing the total amount of tokens
   */
  function totalSupply() public view returns (uint256) {
    return _allTokens.length;
  }

  /**
   * @dev Gets the token ID at a given index of all the tokens in this contract
   * Reverts if the index is greater or equal to the total number of tokens
   * @param index uint256 representing the index to be accessed of the tokens list
   * @return uint256 token ID at the given index of the tokens list
   */
  function tokenByIndex(uint256 index) public view returns (uint256) {
    require(index < totalSupply());
    return _allTokens[index];
  }

  /**
   * @dev Internal function to add a token ID to the list of a given address
   * This function is internal due to language limitations, see the note in ERC721.sol.
   * It is not intended to be called by custom derived contracts: in particular, it emits no Transfer event.
   * @param to address representing the new owner of the given token ID
   * @param tokenId uint256 ID of the token to be added to the tokens list of the given address
   */
  function _addTokenTo(address to, uint256 tokenId) internal {
    super._addTokenTo(to, tokenId);
    uint256 length = _ownedTokens[to].length;
    _ownedTokens[to].push(tokenId);
    _ownedTokensIndex[tokenId] = length;
  }

  /**
   * @dev Internal function to remove a token ID from the list of a given address
   * This function is internal due to language limitations, see the note in ERC721.sol.
   * It is not intended to be called by custom derived contracts: in particular, it emits no Transfer event,
   * and doesn't clear approvals.
   * @param from address representing the previous owner of the given token ID
   * @param tokenId uint256 ID of the token to be removed from the tokens list of the given address
   */
  function _removeTokenFrom(address from, uint256 tokenId) internal {
    super._removeTokenFrom(from, tokenId);

    // To prevent a gap in the array, we store the last token in the index of the token to delete, and
    // then delete the last slot.
    uint256 tokenIndex = _ownedTokensIndex[tokenId];
    uint256 lastTokenIndex = _ownedTokens[from].length.sub(1);
    uint256 lastToken = _ownedTokens[from][lastTokenIndex];

    _ownedTokens[from][tokenIndex] = lastToken;
    // This also deletes the contents at the last position of the array
    _ownedTokens[from].length--;

    // Note that this will handle single-element arrays. In that case, both tokenIndex and lastTokenIndex are going to
    // be zero. Then we can make sure that we will remove tokenId from the ownedTokens list since we are first swapping
    // the lastToken to the first position, and then dropping the element placed in the last position of the list

    _ownedTokensIndex[tokenId] = 0;
    _ownedTokensIndex[lastToken] = tokenIndex;
  }

  /**
   * @dev Internal function to mint a new token
   * Reverts if the given token ID already exists
   * @param to address the beneficiary that will own the minted token
   * @param tokenId uint256 ID of the token to be minted by the msg.sender
   */
  function _mint(address to, uint256 tokenId) internal {
    super._mint(to, tokenId);

    _allTokensIndex[tokenId] = _allTokens.length;
    _allTokens.push(tokenId);
  }

  /**
   * @dev Internal function to burn a specific token
   * Reverts if the token does not exist
   * @param owner owner of the token to burn
   * @param tokenId uint256 ID of the token being burned by the msg.sender
   */
  function _burn(address owner, uint256 tokenId) internal {
    super._burn(owner, tokenId);

    // Reorg all tokens array
    uint256 tokenIndex = _allTokensIndex[tokenId];
    uint256 lastTokenIndex = _allTokens.length.sub(1);
    uint256 lastToken = _allTokens[lastTokenIndex];

    _allTokens[tokenIndex] = lastToken;
    _allTokens[lastTokenIndex] = 0;

    _allTokens.length--;
    _allTokensIndex[tokenId] = 0;
    _allTokensIndex[lastToken] = tokenIndex;
  }
}

/**
 * @title ERC-721 Non-Fungible Token Standard, optional metadata extension
 * @dev See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
 */
contract IERC721Metadata is IERC721 {
  function name() external view returns (string);
  function symbol() external view returns (string);
  function tokenURI(uint256 tokenId) external view returns (string);
}

contract ERC721Metadata is ERC165, ERC721, IERC721Metadata {
  // Token name
  string private _name;

  // Token symbol
  string private _symbol;

  // Optional mapping for token URIs
  mapping(uint256 => string) private _tokenURIs;

  bytes4 private constant InterfaceId_ERC721Metadata = 0x5b5e139f;
  /**
   * 0x5b5e139f ===
   *   bytes4(keccak256('name()')) ^
   *   bytes4(keccak256('symbol()')) ^
   *   bytes4(keccak256('tokenURI(uint256)'))
   */

  /**
   * @dev Constructor function
   */
  constructor(string name, string symbol) public {
    _name = name;
    _symbol = symbol;
   
    // register the supported interfaces to conform to ERC721 via ERC165
    _registerInterface(InterfaceId_ERC721Metadata);
  }

  /**
   * @dev Gets the token name
   * @return string representing the token name
   */
  function name() external view returns (string) {
    return _name;
  }

  /**
   * @dev Gets the token symbol
   * @return string representing the token symbol
   */
  function symbol() external view returns (string) {
    return _symbol;
  }

  /**
   * @dev Returns an URI for a given token ID
   * Throws if the token ID does not exist. May return an empty string.
   * @param tokenId uint256 ID of the token to query
   */
  function tokenURI(uint256 tokenId) external view returns (string) {
    require(_exists(tokenId));
    return _tokenURIs[tokenId];
  }

  /**
   * @dev Internal function to set the token URI for a given token
   * Reverts if the token ID does not exist
   * @param tokenId uint256 ID of the token to set its URI
   * @param uri string URI to assign
   */
  function _setTokenURI(uint256 tokenId, string uri) internal {
    require(_exists(tokenId));
    _tokenURIs[tokenId] = uri;
  }

  /**
   * @dev Internal function to burn a specific token
   * Reverts if the token does not exist
   * @param owner owner of the token to burn
   * @param tokenId uint256 ID of the token being burned by the msg.sender
   */
  function _burn(address owner, uint256 tokenId) internal {
    super._burn(owner, tokenId);

    // Clear metadata (if any)
    if (bytes(_tokenURIs[tokenId]).length != 0) {
      delete _tokenURIs[tokenId];
    }
  }
}

/**
 * @title Roles
 * @dev Library for managing addresses assigned to a Role.
 */
library Roles {
  struct Role {
    mapping (address => bool) bearer;
  }

  /**
   * @dev give an account access to this role
   */
  function add(Role storage role, address account) internal {
    require(account != address(0));
    require(!has(role, account));

    role.bearer[account] = true;
  }

  /**
   * @dev remove an account's access to this role
   */
  function remove(Role storage role, address account) internal {
    require(account != address(0));
    require(has(role, account));

    role.bearer[account] = false;
  }

  /**
   * @dev check if an account has this role
   * @return bool
   */
  function has(Role storage role, address account)
    internal
    view
    returns (bool)
  {
    require(account != address(0));
    return role.bearer[account];
  }
}

contract MinterRole {
  using Roles for Roles.Role;

  event MinterAdded(address indexed account);
  event MinterRemoved(address indexed account);

  Roles.Role private minters;

  constructor() internal {
    _addMinter(msg.sender);
  }

  modifier onlyMinter() {
    require(isMinter(msg.sender));
    _;
  }

  function isMinter(address account) public view returns (bool) {
    return minters.has(account);
  }

  function addMinter(address account) public onlyMinter {
    _addMinter(account);
  }

  function renounceMinter() public {
    _removeMinter(msg.sender);
  }

  function _addMinter(address account) internal {
    minters.add(account);
    emit MinterAdded(account);
  }

  function _removeMinter(address account) internal {
    minters.remove(account);
    emit MinterRemoved(account);
  }
}

/**
 * @title ERC721MetadataMintable
 * @dev ERC721 minting logic with metadata
 */
contract ERC721MetadataMintable is ERC721, ERC721Metadata, MinterRole {
  /**
   * @dev Function to mint tokens
   * @param to The address that will receive the minted tokens.
   * @param tokenId The token id to mint.
   * @param tokenURI The token URI of the minted token.
   * @return A boolean that indicates if the operation was successful.
   */
  function mintWithTokenURI(
    address to,
    uint256 tokenId,
    string tokenURI
  )
    public
    onlyMinter
    returns (bool)
  {
    
    _mint(to, tokenId);
    _setTokenURI(tokenId, tokenURI);
    return true;
  }
}

/**
 * @title Full ERC721 Token
 * This implementation includes all the required and some optional functionality of the ERC721 standard
 * Moreover, it includes approve all functionality using operator terminology
 * @dev see https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
 */
contract ERC721FullBatchMint is ERC721Enumerable, ERC721MetadataMintable {

  string public constant version = "Mintable v0.5" ;
  uint256 public MAX_MINT;

  constructor(string name, string symbol, string url, uint256 batchMint, address owner)
    ERC721Metadata(name, symbol)
    public
  {
    MAX_MINT = batchMint;
    _mint(owner, 0);
    _setTokenURI(0, url);
  }

  function batchMint (string url, uint256 count)
    public onlyMinter
  returns (bool) {
    if (count > MAX_MINT || count <= 0 || count < 0) {
      count = MAX_MINT;
    }
    uint256 totalSupply = super.totalSupply();
    for (uint256 i = 0; i < count; i++) {
      mintWithTokenURI(msg.sender, totalSupply+i, url);
    }
    return true;
  }
}

contract GSG_official{
    ERC721FullBatchMint token;
    
    using SafeMath for uint256;
    uint256 public currentId;
    uint256 public registeredUsers;
    address Owner;
    
    struct userDataSet{
        uint256 claimedAmount;
        uint256 timeFrame;
        uint256 currentAmount;
        uint256 timeForClaim;
        bool isRegister;
    }
    

    mapping(address => userDataSet) public userMap;
    mapping(uint256 => address) public userlist;
    
    event TransferETH(address,uint256);
    event UserRegistered(address);
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    
    // give token address of mainnet *the token you want to use in a contract*
    constructor(address _tokenAddress) public {
        token = ERC721FullBatchMint(address(_tokenAddress));
        Owner = msg.sender;

    }
    
    modifier onlyOwner() {
        require(msg.sender == owner(),"ERROR: Only for owner");
        _;
    }
    
    function() external payable{
    }
    //register user to contract so they can start earning ethers 
    function register() public {
        require(token.balanceOf(msg.sender) > 0,"ERROR: Get GSG-Official token to register");
        require(msg.sender != address(0),"ERROR: zero address");
        require(userMap[msg.sender].isRegister == false,"ERROR: User already registered");
        
        userDataSet memory userdata;
        currentId++;
        registeredUsers++;
        
        userdata = userDataSet({
            claimedAmount: 0,
            timeFrame: now + 4 weeks,
            currentAmount: 0,
            timeForClaim: now + 90 days,
            isRegister: true
        });
        
        userMap[msg.sender] = userdata;
        userlist[currentId] = msg.sender;
        emit UserRegistered(msg.sender);
    }
    
    function hasRegistered() public view returns(bool) {
        return userMap[msg.sender].isRegister;
    }
    
    // user can claim one a month 
    //claim amount is calculated according to how much balance and ethers we have in a contract
    function claim() public returns(bool){
        require(token.balanceOf(msg.sender) > 0,"ERROR: You need a token to clain ETH");
        require(msg.sender != address(0), "ERROR: zero address");
        require(userMap[msg.sender].isRegister,"ERROR: Register first");
        
        if(now >= userMap[msg.sender].timeForClaim) {
            userMap[msg.sender].currentAmount = 0; 
            return true;
        }
        require(now >= userMap[msg.sender].timeFrame,"ERROR: Cannot claim before one month");
        uint256 price = userMap[msg.sender].currentAmount;
        
        address(msg.sender).transfer(price);
        
        userMap[msg.sender].claimedAmount += price;
        userMap[msg.sender].currentAmount -= price;
        userMap[msg.sender].timeFrame = now +  4 weeks;
        userMap[msg.sender].timeForClaim = now + 90 days;
        emit TransferETH(msg.sender,price);
        
    }
    
    function calculatePriceETH() internal view returns(uint256) {
        uint256 contractBal = address(this).balance;
        uint256 balances1 = contractBal.mul(30).div(100);
        uint256 balances = balances1.div(registeredUsers);
        return balances;
    }
    
    function holdersBalance() public view returns(uint256) {
        if(now >= userMap[msg.sender].timeFrame){
            return userMap[msg.sender].currentAmount;
        }else{
            return 0;
        }
    }
    
    function distributeETH() public onlyOwner {
        uint256 id = currentId;
        uint256 price = calculatePriceETH();
        
        for(uint256 i=1; i<=id; i++){
            userMap[userlist[i]].currentAmount += price;
        }
        
    }
    
    function totalETH() public view returns(uint256) {
        return address(this).balance;
    }
    
    function owner() public view returns(address){
        return Owner;
    }
    
    
    function transferOwnerShip(address _address) public onlyOwner {
        emit OwnershipTransferred(owner(),_address);
        Owner = _address;
    }
    
    
   function stopPool() public onlyOwner {
       address(this).transfer(address(this).balance);
   }
   
}