CryptoGhost.sol

// File: openzeppelin-solidity/contracts/GSN/Context.sol

pragma solidity ^0.5.0;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
contract Context {
    // Empty internal constructor, to prevent people from mistakenly deploying
    // an instance of this contract, which should be used via inheritance.
    constructor() internal {}

    // solhint-disable-previous-line no-empty-blocks

    function _msgSender() internal view returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// File: openzeppelin-solidity/contracts/introspection/IERC165.sol

pragma solidity ^0.5.0;

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

// File: openzeppelin-solidity/contracts/token/ERC721/IERC721.sol

pragma solidity ^0.5.0;

/**
 * @dev Required interface of an ERC721 compliant contract.
 */
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
    );

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

    /**
     * @dev Returns the owner of the NFT specified by `tokenId`.
     */
    function ownerOf(uint256 tokenId) public view returns (address owner);

    /**
     * @dev Transfers a specific NFT (`tokenId`) from one account (`from`) to
     * another (`to`).
     *
     *
     *
     * Requirements:
     * - `from`, `to` cannot be zero.
     * - `tokenId` must be owned by `from`.
     * - If the caller is not `from`, it must be have been allowed to move this
     * NFT by either {approve} or {setApprovalForAll}.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public;

    /**
     * @dev Transfers a specific NFT (`tokenId`) from one account (`from`) to
     * another (`to`).
     *
     * Requirements:
     * - If the caller is not `from`, it must be approved to move this NFT by
     * either {approve} or {setApprovalForAll}.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public;

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

// File: openzeppelin-solidity/contracts/token/ERC721/IERC721Receiver.sol

pragma solidity ^0.5.0;

/**
 * @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 {IERC721-safeTransferFrom}. 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 `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
     */
    function onERC721Received(
        address operator,
        address from,
        uint256 tokenId,
        bytes memory data
    ) public returns (bytes4);
}

// File: openzeppelin-solidity/contracts/math/SafeMath.sol

pragma solidity ^0.5.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
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;
    }
}

// File: openzeppelin-solidity/contracts/utils/Address.sol

pragma solidity ^0.5.5;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // 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;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            codehash := extcodehash(account)
        }
        return (codehash != accountHash && codehash != 0x0);
    }

    /**
     * @dev Converts an `address` into `address payable`. Note that this is
     * simply a type cast: the actual underlying value is not changed.
     *
     * _Available since v2.4.0._
     */
    function toPayable(address account)
        internal
        pure
        returns (address payable)
    {
        return address(uint160(account));
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     *
     * _Available since v2.4.0._
     */
    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"
        );
    }
}

// File: openzeppelin-solidity/contracts/drafts/Counters.sol

pragma solidity ^0.5.0;

/**
 * @title Counters
 * @author Matt Condon (@shrugs)
 * @dev Provides counters that can only be incremented or decremented by one. This can be used e.g. to track the number
 * of elements in a mapping, issuing ERC721 ids, or counting request ids.
 *
 * Include with `using Counters for Counters.Counter;`
 * Since it is not possible to overflow a 256 bit integer with increments of one, `increment` can skip the {SafeMath}
 * overflow check, thereby saving gas. This does assume however correct usage, in that the underlying `_value` is never
 * directly accessed.
 */
library Counters {
    using SafeMath for uint256;

    struct Counter {
        // This variable should never be directly accessed by users of the library: interactions must be restricted to
        // the library's function. As of Solidity v0.5.2, this cannot be enforced, though there is a proposal to add
        // this feature: see https://github.com/ethereum/solidity/issues/4637
        uint256 _value; // default: 0
    }

    function current(Counter storage counter) internal view returns (uint256) {
        return counter._value;
    }

    function increment(Counter storage counter) internal {
        // The {SafeMath} overflow check can be skipped here, see the comment at the top
        counter._value += 1;
    }

    function decrement(Counter storage counter) internal {
        counter._value = counter._value.sub(1);
    }
}

// File: openzeppelin-solidity/contracts/introspection/ERC165.sol

pragma solidity ^0.5.0;

/**
 * @dev Implementation of the {IERC165} interface.
 *
 * Contracts may inherit from this and call {_registerInterface} to declare
 * their support of an interface.
 */
contract ERC165 is IERC165 {
    /*
     * bytes4(keccak256('supportsInterface(bytes4)')) == 0x01ffc9a7
     */
    bytes4 private constant _INTERFACE_ID_ERC165 = 0x01ffc9a7;

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

    constructor() internal {
        // Derived contracts need only register support for their own interfaces,
        // we register support for ERC165 itself here
        _registerInterface(_INTERFACE_ID_ERC165);
    }

    /**
     * @dev See {IERC165-supportsInterface}.
     *
     * Time complexity O(1), guaranteed to always use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId)
        external
        view
        returns (bool)
    {
        return _supportedInterfaces[interfaceId];
    }

    /**
     * @dev Registers the contract as an implementer of the interface defined by
     * `interfaceId`. Support of the actual ERC165 interface is automatic and
     * registering its interface id is not required.
     *
     * See {IERC165-supportsInterface}.
     *
     * Requirements:
     *
     * - `interfaceId` cannot be the ERC165 invalid interface (`0xffffffff`).
     */
    function _registerInterface(bytes4 interfaceId) internal {
        require(interfaceId != 0xffffffff, "ERC165: invalid interface id");
        _supportedInterfaces[interfaceId] = true;
    }
}

// File: openzeppelin-solidity/contracts/token/ERC721/ERC721.sol

pragma solidity ^0.5.0;

/**
 * @title ERC721 Non-Fungible Token Standard basic implementation
 * @dev see https://eips.ethereum.org/EIPS/eip-721
 */
contract ERC721 is Context, ERC165, IERC721 {
    using SafeMath for uint256;
    using Address for address;
    using Counters for Counters.Counter;

    // 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 => Counters.Counter) private _ownedTokensCount;

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

    /*
     *     bytes4(keccak256('balanceOf(address)')) == 0x70a08231
     *     bytes4(keccak256('ownerOf(uint256)')) == 0x6352211e
     *     bytes4(keccak256('approve(address,uint256)')) == 0x095ea7b3
     *     bytes4(keccak256('getApproved(uint256)')) == 0x081812fc
     *     bytes4(keccak256('setApprovalForAll(address,bool)')) == 0xa22cb465
     *     bytes4(keccak256('isApprovedForAll(address,address)')) == 0xe985e9c5
     *     bytes4(keccak256('transferFrom(address,address,uint256)')) == 0x23b872dd
     *     bytes4(keccak256('safeTransferFrom(address,address,uint256)')) == 0x42842e0e
     *     bytes4(keccak256('safeTransferFrom(address,address,uint256,bytes)')) == 0xb88d4fde
     *
     *     => 0x70a08231 ^ 0x6352211e ^ 0x095ea7b3 ^ 0x081812fc ^
     *        0xa22cb465 ^ 0xe985e9c ^ 0x23b872dd ^ 0x42842e0e ^ 0xb88d4fde == 0x80ac58cd
     */
    bytes4 private constant _INTERFACE_ID_ERC721 = 0x80ac58cd;

    constructor() public {
        // register the supported interfaces to conform to ERC721 via ERC165
        _registerInterface(_INTERFACE_ID_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),
            "ERC721: balance query for the zero address"
        );

        return _ownedTokensCount[owner].current();
    }

    /**
     * @dev Gets the owner of the specified token ID.
     * @param tokenId uint256 ID of the token to query the owner of
     * @return 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),
            "ERC721: owner query for nonexistent token"
        );

        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, "ERC721: approval to current owner");

        require(
            _msgSender() == owner || isApprovedForAll(owner, _msgSender()),
            "ERC721: approve caller is not owner nor approved for all"
        );

        _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),
            "ERC721: approved query for nonexistent token"
        );

        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 != _msgSender(), "ERC721: approve to caller");

        _operatorApprovals[_msgSender()][to] = approved;
        emit ApprovalForAll(_msgSender(), 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 {
        //solhint-disable-next-line max-line-length
        require(
            _isApprovedOrOwner(_msgSender(), tokenId),
            "ERC721: transfer caller is not owner nor approved"
        );

        _transferFrom(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 {IERC721Receiver-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 {
        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 {IERC721Receiver-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 _msgSender() 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 memory _data
    ) public {
        require(
            _isApprovedOrOwner(_msgSender(), tokenId),
            "ERC721: transfer caller is not owner nor approved"
        );
        _safeTransferFrom(from, to, tokenId, _data);
    }

    /**
     * @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 memory _data
    ) internal {
        _transferFrom(from, to, tokenId);
        require(
            _checkOnERC721Received(from, to, tokenId, _data),
            "ERC721: transfer to non ERC721Receiver implementer"
        );
    }

    /**
     * @dev Returns whether the specified token exists.
     * @param tokenId uint256 ID of the token to query the existence of
     * @return bool 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)
    {
        require(
            _exists(tokenId),
            "ERC721: operator query for nonexistent token"
        );
        address owner = ownerOf(tokenId);
        return (spender == owner ||
            getApproved(tokenId) == spender ||
            isApprovedForAll(owner, spender));
    }

    /**
     * @dev Internal function to safely mint a new token.
     * Reverts if the given token ID already exists.
     * 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.
     * @param to The address that will own the minted token
     * @param tokenId uint256 ID of the token to be minted
     */
    function _safeMint(address to, uint256 tokenId) internal {
        _safeMint(to, tokenId, "");
    }

    /**
     * @dev Internal function to safely mint a new token.
     * Reverts if the given token ID already exists.
     * 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.
     * @param to The address that will own the minted token
     * @param tokenId uint256 ID of the token to be minted
     * @param _data bytes data to send along with a safe transfer check
     */
    function _safeMint(
        address to,
        uint256 tokenId,
        bytes memory _data
    ) internal {
        _mint(to, tokenId);
        require(
            _checkOnERC721Received(address(0), to, tokenId, _data),
            "ERC721: transfer to non ERC721Receiver implementer"
        );
    }

    /**
     * @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
     */
    function _mint(address to, uint256 tokenId) internal {
        require(to != address(0), "ERC721: mint to the zero address");
        require(!_exists(tokenId), "ERC721: token already minted");

        _tokenOwner[tokenId] = to;
        _ownedTokensCount[to].increment();

        emit Transfer(address(0), to, tokenId);
    }

    /**
     * @dev Internal function to burn a specific token.
     * Reverts if the token does not exist.
     * Deprecated, use {_burn} instead.
     * @param owner owner of the token to burn
     * @param tokenId uint256 ID of the token being burned
     */
    function _burn(address owner, uint256 tokenId) internal {
        require(
            ownerOf(tokenId) == owner,
            "ERC721: burn of token that is not own"
        );

        _clearApproval(tokenId);

        _ownedTokensCount[owner].decrement();
        _tokenOwner[tokenId] = address(0);

        emit Transfer(owner, address(0), 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
     */
    function _burn(uint256 tokenId) internal {
        _burn(ownerOf(tokenId), tokenId);
    }

    /**
     * @dev Internal function to transfer ownership of a given token ID to another address.
     * As opposed to {transferFrom}, this imposes no restrictions on msg.sender.
     * @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
    ) internal {
        require(
            ownerOf(tokenId) == from,
            "ERC721: transfer of token that is not own"
        );
        require(to != address(0), "ERC721: transfer to the zero address");

        _clearApproval(tokenId);

        _ownedTokensCount[from].decrement();
        _ownedTokensCount[to].increment();

        _tokenOwner[tokenId] = to;

        emit Transfer(from, to, tokenId);
    }

    /**
     * @dev Internal function to invoke {IERC721Receiver-onERC721Received} on a target address.
     * The call is not executed if the target address is not a contract.
     *
     * This is an internal detail of the `ERC721` contract and its use is deprecated.
     * @param from address representing the previous owner of the given token ID
     * @param to target address that will receive the tokens
     * @param tokenId uint256 ID of the token to be transferred
     * @param _data bytes optional data to send along with the call
     * @return bool whether the call correctly returned the expected magic value
     */
    function _checkOnERC721Received(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
    ) internal returns (bool) {
        if (!to.isContract()) {
            return true;
        }
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) =
            to.call(
                abi.encodeWithSelector(
                    IERC721Receiver(to).onERC721Received.selector,
                    _msgSender(),
                    from,
                    tokenId,
                    _data
                )
            );
        if (!success) {
            if (returndata.length > 0) {
                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert("ERC721: transfer to non ERC721Receiver implementer");
            }
        } else {
            bytes4 retval = abi.decode(returndata, (bytes4));
            return (retval == _ERC721_RECEIVED);
        }
    }

    /**
     * @dev Private function to clear current approval of a given token ID.
     * @param tokenId uint256 ID of the token to be transferred
     */
    function _clearApproval(uint256 tokenId) private {
        if (_tokenApprovals[tokenId] != address(0)) {
            _tokenApprovals[tokenId] = address(0);
        }
    }
}

// File: openzeppelin-solidity/contracts/token/ERC721/IERC721Enumerable.sol

pragma solidity ^0.5.0;

/**
 * @title ERC-721 Non-Fungible Token Standard, optional enumeration extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
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);
}

// File: openzeppelin-solidity/contracts/token/ERC721/ERC721Enumerable.sol

pragma solidity ^0.5.0;

/**
 * @title ERC-721 Non-Fungible Token with optional enumeration extension logic
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
contract ERC721Enumerable is Context, 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(keccak256('totalSupply()')) == 0x18160ddd
     *     bytes4(keccak256('tokenOfOwnerByIndex(address,uint256)')) == 0x2f745c59
     *     bytes4(keccak256('tokenByIndex(uint256)')) == 0x4f6ccce7
     *
     *     => 0x18160ddd ^ 0x2f745c59 ^ 0x4f6ccce7 == 0x780e9d63
     */
    bytes4 private constant _INTERFACE_ID_ERC721_ENUMERABLE = 0x780e9d63;

    /**
     * @dev Constructor function.
     */
    constructor() public {
        // register the supported interface to conform to ERC721Enumerable via ERC165
        _registerInterface(_INTERFACE_ID_ERC721_ENUMERABLE);
    }

    /**
     * @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),
            "ERC721Enumerable: owner index out of bounds"
        );
        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(),
            "ERC721Enumerable: global index out of bounds"
        );
        return _allTokens[index];
    }

    /**
     * @dev Internal function to transfer ownership of a given token ID to another address.
     * As opposed to transferFrom, this imposes no restrictions on msg.sender.
     * @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
    ) internal {
        super._transferFrom(from, to, tokenId);

        _removeTokenFromOwnerEnumeration(from, tokenId);

        _addTokenToOwnerEnumeration(to, tokenId);
    }

    /**
     * @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
     */
    function _mint(address to, uint256 tokenId) internal {
        super._mint(to, tokenId);

        _addTokenToOwnerEnumeration(to, tokenId);

        _addTokenToAllTokensEnumeration(tokenId);
    }

    /**
     * @dev Internal function to burn a specific token.
     * Reverts if the token does not exist.
     * Deprecated, use {ERC721-_burn} instead.
     * @param owner owner of the token to burn
     * @param tokenId uint256 ID of the token being burned
     */
    function _burn(address owner, uint256 tokenId) internal {
        super._burn(owner, tokenId);

        _removeTokenFromOwnerEnumeration(owner, tokenId);
        // Since tokenId will be deleted, we can clear its slot in _ownedTokensIndex to trigger a gas refund
        _ownedTokensIndex[tokenId] = 0;

        _removeTokenFromAllTokensEnumeration(tokenId);
    }

    /**
     * @dev Gets the list of token IDs of the requested owner.
     * @param owner address owning the tokens
     * @return uint256[] List of token IDs owned by the requested address
     */
    function _tokensOfOwner(address owner)
        internal
        view
        returns (uint256[] storage)
    {
        return _ownedTokens[owner];
    }

    /**
     * @dev Private function to add a token to this extension's ownership-tracking data structures.
     * @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 _addTokenToOwnerEnumeration(address to, uint256 tokenId) private {
        _ownedTokensIndex[tokenId] = _ownedTokens[to].length;
        _ownedTokens[to].push(tokenId);
    }

    /**
     * @dev Private function to add a token to this extension's token tracking data structures.
     * @param tokenId uint256 ID of the token to be added to the tokens list
     */
    function _addTokenToAllTokensEnumeration(uint256 tokenId) private {
        _allTokensIndex[tokenId] = _allTokens.length;
        _allTokens.push(tokenId);
    }

    /**
     * @dev Private function to remove a token from this extension's ownership-tracking data structures. Note that
     * while the token is not assigned a new owner, the `_ownedTokensIndex` mapping is _not_ updated: this allows for
     * gas optimizations e.g. when performing a transfer operation (avoiding double writes).
     * This has O(1) time complexity, but alters the order of the _ownedTokens array.
     * @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 _removeTokenFromOwnerEnumeration(address from, uint256 tokenId)
        private
    {
        // To prevent a gap in from's tokens array, we store the last token in the index of the token to delete, and
        // then delete the last slot (swap and pop).

        uint256 lastTokenIndex = _ownedTokens[from].length.sub(1);
        uint256 tokenIndex = _ownedTokensIndex[tokenId];

        // When the token to delete is the last token, the swap operation is unnecessary
        if (tokenIndex != lastTokenIndex) {
            uint256 lastTokenId = _ownedTokens[from][lastTokenIndex];

            _ownedTokens[from][tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
            _ownedTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index
        }

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

        // Note that _ownedTokensIndex[tokenId] hasn't been cleared: it still points to the old slot (now occupied by
        // lastTokenId, or just over the end of the array if the token was the last one).
    }

    /**
     * @dev Private function to remove a token from this extension's token tracking data structures.
     * This has O(1) time complexity, but alters the order of the _allTokens array.
     * @param tokenId uint256 ID of the token to be removed from the tokens list
     */
    function _removeTokenFromAllTokensEnumeration(uint256 tokenId) private {
        // To prevent a gap in the tokens array, we store the last token in the index of the token to delete, and
        // then delete the last slot (swap and pop).

        uint256 lastTokenIndex = _allTokens.length.sub(1);
        uint256 tokenIndex = _allTokensIndex[tokenId];

        // When the token to delete is the last token, the swap operation is unnecessary. However, since this occurs so
        // rarely (when the last minted token is burnt) that we still do the swap here to avoid the gas cost of adding
        // an 'if' statement (like in _removeTokenFromOwnerEnumeration)
        uint256 lastTokenId = _allTokens[lastTokenIndex];

        _allTokens[tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
        _allTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index

        // This also deletes the contents at the last position of the array
        _allTokens.length--;
        _allTokensIndex[tokenId] = 0;
    }
}

// File: openzeppelin-solidity/contracts/token/ERC721/IERC721Metadata.sol

pragma solidity ^0.5.0;

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

    function symbol() external view returns (string memory);

    function tokenURI(uint256 tokenId) external view returns (string memory);
}

// File: openzeppelin-solidity/contracts/token/ERC721/ERC721Metadata.sol

pragma solidity ^0.5.0;

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

    // Token symbol
    string private _symbol;

    // Base URI
    string private _baseURI;

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

    /*
     *     bytes4(keccak256('name()')) == 0x06fdde03
     *     bytes4(keccak256('symbol()')) == 0x95d89b41
     *     bytes4(keccak256('tokenURI(uint256)')) == 0xc87b56dd
     *
     *     => 0x06fdde03 ^ 0x95d89b41 ^ 0xc87b56dd == 0x5b5e139f
     */
    bytes4 private constant _INTERFACE_ID_ERC721_METADATA = 0x5b5e139f;

    /**
     * @dev Constructor function
     */
    constructor(string memory name, string memory symbol) public {
        _name = name;
        _symbol = symbol;

        // register the supported interfaces to conform to ERC721 via ERC165
        _registerInterface(_INTERFACE_ID_ERC721_METADATA);
    }

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

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

    /**
     * @dev Returns the URI for a given token ID. May return an empty string.
     *
     * If the token's URI is non-empty and a base URI was set (via
     * {_setBaseURI}), it will be added to the token ID's URI as a prefix.
     *
     * Reverts if the token ID does not exist.
     */
    function tokenURI(uint256 tokenId) external view returns (string memory) {
        require(
            _exists(tokenId),
            "ERC721Metadata: URI query for nonexistent token"
        );

        string memory _tokenURI = _tokenURIs[tokenId];

        // Even if there is a base URI, it is only appended to non-empty token-specific URIs
        if (bytes(_tokenURI).length == 0) {
            return "";
        } else {
            // abi.encodePacked is being used to concatenate strings
            return string(abi.encodePacked(_baseURI, _tokenURI));
        }
    }

    /**
     * @dev Internal function to set the token URI for a given token.
     *
     * Reverts if the token ID does not exist.
     *
     * TIP: if all token IDs share a prefix (e.g. if your URIs look like
     * `http://api.myproject.com/token/<id>`), use {_setBaseURI} to store
     * it and save gas.
     */
    function _setTokenURI(uint256 tokenId, string memory _tokenURI) internal {
        require(
            _exists(tokenId),
            "ERC721Metadata: URI set of nonexistent token"
        );
        _tokenURIs[tokenId] = _tokenURI;
    }

    /**
     * @dev Internal function to set the base URI for all token IDs. It is
     * automatically added as a prefix to the value returned in {tokenURI}.
     *
     * _Available since v2.5.0._
     */
    function _setBaseURI(string memory baseURI) internal {
        _baseURI = baseURI;
    }

    /**
     * @dev Returns the base URI set via {_setBaseURI}. This will be
     * automatically added as a preffix in {tokenURI} to each token's URI, when
     * they are non-empty.
     *
     * _Available since v2.5.0._
     */
    function baseURI() external view returns (string memory) {
        return _baseURI;
    }

    /**
     * @dev Internal function to burn a specific token.
     * Reverts if the token does not exist.
     * Deprecated, use _burn(uint256) instead.
     * @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];
        }
    }
}

// File: openzeppelin-solidity/contracts/token/ERC721/ERC721Full.sol

pragma solidity ^0.5.0;

/**
 * @title Full ERC721 Token
 * @dev This implementation includes all the required and some optional functionality of the ERC721 standard
 * Moreover, it includes approve all functionality using operator terminology.
 *
 * See https://eips.ethereum.org/EIPS/eip-721
 */
contract ERC721Full is ERC721, ERC721Enumerable, ERC721Metadata {
    constructor(string memory name, string memory symbol)
        public
        ERC721Metadata(name, symbol)
    {
        // solhint-disable-previous-line no-empty-blocks
    }
}

// File: openzeppelin-solidity/contracts/ownership/Ownable.sol

pragma solidity ^0.5.0;

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(
        address indexed previousOwner,
        address indexed newOwner
    );

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() internal {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

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

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(isOwner(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Returns true if the caller is the current owner.
     */
    function isOwner() public view returns (bool) {
        return _msgSender() == _owner;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public onlyOwner {
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     */
    function _transferOwnership(address newOwner) internal {
        require(
            newOwner != address(0),
            "Ownable: new owner is the zero address"
        );
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

// File: contracts/Strings.sol

pragma solidity ^0.5.0;

library Strings {
    // via https://github.com/oraclize/ethereum-api/blob/master/oraclizeAPI_0.5.sol
    function strConcat(
        string memory _a,
        string memory _b,
        string memory _c,
        string memory _d,
        string memory _e
    ) internal pure returns (string memory) {
        bytes memory _ba = bytes(_a);
        bytes memory _bb = bytes(_b);
        bytes memory _bc = bytes(_c);
        bytes memory _bd = bytes(_d);
        bytes memory _be = bytes(_e);
        string memory abcde =
            new string(
                _ba.length + _bb.length + _bc.length + _bd.length + _be.length
            );
        bytes memory babcde = bytes(abcde);
        uint256 k = 0;
        for (uint256 i = 0; i < _ba.length; i++) babcde[k++] = _ba[i];
        for (uint256 i = 0; i < _bb.length; i++) babcde[k++] = _bb[i];
        for (uint256 i = 0; i < _bc.length; i++) babcde[k++] = _bc[i];
        for (uint256 i = 0; i < _bd.length; i++) babcde[k++] = _bd[i];
        for (uint256 i = 0; i < _be.length; i++) babcde[k++] = _be[i];
        return string(babcde);
    }

    function strConcat(
        string memory _a,
        string memory _b,
        string memory _c,
        string memory _d
    ) internal pure returns (string memory) {
        return strConcat(_a, _b, _c, _d, "");
    }

    function strConcat(
        string memory _a,
        string memory _b,
        string memory _c
    ) internal pure returns (string memory) {
        return strConcat(_a, _b, _c, "", "");
    }

    function strConcat(string memory _a, string memory _b)
        internal
        pure
        returns (string memory)
    {
        return strConcat(_a, _b, "", "", "");
    }

    function uint2str(uint256 _i)
        internal
        pure
        returns (string memory _uintAsString)
    {
        if (_i == 0) {
            return "0";
        }
        uint256 j = _i;
        uint256 len;
        while (j != 0) {
            len++;
            j /= 10;
        }
        bytes memory bstr = new bytes(len);
        uint256 k = len - 1;
        while (_i != 0) {
            bstr[k--] = bytes1(uint8(48 + (_i % 10)));
            _i /= 10;
        }
        return string(bstr);
    }
}

// File: contracts/ERC721Tradable.sol

pragma solidity ^0.5.0;

contract OwnableDelegateProxy {}

contract ProxyRegistry {
    mapping(address => OwnableDelegateProxy) public proxies;
}

/**
 * @title ERC721Tradable
 * ERC721Tradable - ERC721 contract that whitelists a trading address, and has minting functionality.
 */
contract ERC721Tradable is ERC721Full, Ownable {
    using Strings for string;

    address proxyRegistryAddress;
    uint256 private _currentTokenId = 0;

    constructor(
        string memory _name,
        string memory _symbol,
        address _proxyRegistryAddress
    ) public ERC721Full(_name, _symbol) {
        proxyRegistryAddress = _proxyRegistryAddress;
    }

    // /**
    //  * @dev Mints a token to an address with a tokenURI.
    //  * @param _to address of the future owner of the token
    //  */
    // function mintTo(address _to) public onlyOwner {
    //     uint256 newTokenId = _getNextTokenId();
    //     _mint(_to, newTokenId);
    //     _incrementTokenId();
    // }

    /**
     * @dev calculates the next token ID based on value of _currentTokenId
     * @return uint256 for the next token ID
     */
    function _getNextTokenId() private view returns (uint256) {
        return _currentTokenId.add(1);
    }

    /**
     * @dev increments the value of _currentTokenId
     */
    function _incrementTokenId() private {
        _currentTokenId++;
    }

    function baseTokenURI() public pure returns (string memory) {
        return "";
    }

    function tokenURI(uint256 _tokenId) external view returns (string memory) {
        return Strings.strConcat(baseTokenURI(), Strings.uint2str(_tokenId));
    }

    /**
     * Override isApprovedForAll to whitelist user's OpenSea proxy accounts to enable gas-less listings.
     */
    function isApprovedForAll(address owner, address operator)
        public
        view
        returns (bool)
    {
        // Whitelist OpenSea proxy contract for easy trading.
        ProxyRegistry proxyRegistry = ProxyRegistry(proxyRegistryAddress);
        if (address(proxyRegistry.proxies(owner)) == operator) {
            return true;
        }

        return super.isApprovedForAll(owner, operator);
    }
}

library BytesUtils {
    function char(bytes1 b) internal pure returns (bytes1 c) {
        if (uint8(b) < 10) return bytes1(uint8(b) + 0x30);
        else return bytes1(uint8(b) + 0x57);
    }

    function bytes32string(bytes32 b32)
        internal
        pure
        returns (string memory out)
    {
        bytes memory s = new bytes(64);
        for (uint32 i = 0; i < 32; i++) {
            bytes1 b = bytes1(b32[i]);
            bytes1 hi = bytes1(uint8(b) / 16);
            bytes1 lo = bytes1(uint8(b) - 16 * uint8(hi));
            s[i * 2] = char(hi);
            s[i * 2 + 1] = char(lo);
        }
        out = string(s);
    }

    function hach(string memory value) internal pure returns (string memory) {
        return bytes32string(sha256(abi.encodePacked(value)));
    }

    function MergeBytes(bytes memory a, bytes memory b)
        internal
        pure
        returns (bytes memory c)
    {
        // Store the length of the first array
        uint256 alen = a.length;
        // Store the length of BOTH arrays
        uint256 totallen = alen + b.length;
        // Count the loops required for array a (sets of 32 bytes)
        uint256 loopsa = (a.length + 31) / 32;
        // Count the loops required for array b (sets of 32 bytes)
        uint256 loopsb = (b.length + 31) / 32;
        assembly {
            let m := mload(0x40)
            // Load the length of both arrays to the head of the new bytes array
            mstore(m, totallen)
            // Add the contents of a to the array
            for {
                let i := 0
            } lt(i, loopsa) {
                i := add(1, i)
            } {
                mstore(
                    add(m, mul(32, add(1, i))),
                    mload(add(a, mul(32, add(1, i))))
                )
            }
            // Add the contents of b to the array
            for {
                let i := 0
            } lt(i, loopsb) {
                i := add(1, i)
            } {
                mstore(
                    add(m, add(mul(32, add(1, i)), alen)),
                    mload(add(b, mul(32, add(1, i))))
                )
            }
            mstore(0x40, add(m, add(32, totallen)))
            c := m
        }
    }
}

// File: contracts/Creature.sol

pragma solidity ^0.5.0;

/**
 * @title CryptoGhost
 */
contract CryptoGhost is ERC721Tradable {
    uint256 currentMintId = 0;
    
    mapping(uint256 => string) private idToGhostKey;
    mapping(string => uint256) private ghostKeyToTokenId;
    mapping(string => bool) private ghostKeyToIsGhostKeyReserved;
    mapping(uint256 => string) private idToGhostName;

    constructor(address _proxyRegistryAddress)
        public
        ERC721Tradable("CryptoGhost", "GHOST", _proxyRegistryAddress)
    {}

    function getGhostKey(uint256 tokenId) public view returns (string memory) {
        require(tokenId < totalSupply(), "Token does not exist");
        string memory ghostKey = idToGhostKey[tokenId];
        return ghostKey;
    }

    function getGhostName(uint256 tokenId) public view returns (string memory) {
        return idToGhostName[tokenId];
    }

    function getTokenIdFromGhostKey(string memory ghostKey)
        public
        view
        returns (uint256)
    {
        require(ghostKeyToIsGhostKeyReserved[ghostKey]);
        return ghostKeyToTokenId[ghostKey];
    }

    function checkGhostKey(string memory str) public pure returns (bool) {
        bytes memory b = bytes(str);
        if (b.length > 25) return false;
        if (b.length == 0) return false;

        for (uint256 i; i < b.length; i++) {
            bytes1 char = b[i];
            if (
                !(char >= 0x30 && char <= 0x39) && //9-0
                !(char >= 0x41 && char <= 0x5A) && //A-Z
                !(char >= 0x61 && char <= 0x7A) //a-z
            ) return false;
        }
        return true;
    }

    function checkGhostName(string memory str) public pure returns (bool) {
        bytes memory b = bytes(str);
        if (b.length > 30) return false;
        if (b.length == 0) return false;

        for (uint256 i; i < b.length; i++) {
            bytes1 char = b[i];
            if (
                !(char >= 0x30 && char <= 0x39) && //9-0
                !(char >= 0x41 && char <= 0x5A) && //A-Z
                !(char >= 0x61 && char <= 0x7A) && //a-z
                !(char == 0x20) // space
            ) return false;
        }
        return true;
    }

    function claimGhost(string memory ghostKey, string memory ghostName)
        public
        payable
    {
        require(block.timestamp < 1647730800, "Minting is over");
        require(msg.value == 0.2 ether, "Need to send 0.2 ether");
        require(
            checkGhostKey(ghostKey),
            "Ghost Key validation failure"
        );
        require(
            checkGhostName(ghostName),
            "Ghost Name validation failure"
        );
        super._mint(msg.sender, currentMintId);
        idToGhostKey[currentMintId] = ghostKey;
        idToGhostName[currentMintId] = ghostName;
        ghostKeyToTokenId[ghostKey] = currentMintId;
        ghostKeyToIsGhostKeyReserved[ghostKey] = true;
        address payable _owner = address(uint160(owner()));
        _owner.transfer(msg.value);
        currentMintId += 1;
    }

    function baseTokenURI() public pure returns (string memory) {
        return "https://cryptoghost.art/meta/items/";
    }

    function contractURI() public pure returns (string memory) {
        return "https://cryptoghost.art/meta/ghost.json";
    }

    function getBitmapFromghostKey(string memory value)
        public
        view
        returns (bytes memory)
    {
        bytes memory headers =
            hex"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";
        bytes memory pixels = new bytes(16384);

        int256 x = 64;
        int256 y = 64;

        int256 totalIndex = 0;
        int256 colorIndex = 0;
        string memory tmp = value;
        bytes memory cha;

        for (uint256 iFill = 0; iFill < 16384; iFill++) {
            pixels[iFill] = bytes1(uint8(255));
        }

        for (uint256 i = 0; i < 151; i++) {
            tmp = BytesUtils.hach(tmp);
            cha = bytes(tmp);
            for (uint256 iChar = 0; iChar < 64; iChar++) {
                if (uint8(cha[iChar]) == 48 || uint8(cha[iChar]) == 49) {
                    x += 1;
                } else if (uint8(cha[iChar]) == 50 || uint8(cha[iChar]) == 51) {
                    x += -1;
                } else if (uint8(cha[iChar]) == 52 || uint8(cha[iChar]) == 53) {
                    y += 1;
                } else if (uint8(cha[iChar]) == 54 || uint8(cha[iChar]) == 55) {
                    y += -1;
                } else if (uint8(cha[iChar]) == 56 || uint8(cha[iChar]) == 57) {
                    x += 1;
                    y += 1;
                } else if (uint8(cha[iChar]) == 97 || uint8(cha[iChar]) == 98) {
                    x += -1;
                    y += 1;
                } else if (
                    uint8(cha[iChar]) == 99 || uint8(cha[iChar]) == 100
                ) {
                    x += 1;
                    y += -1;
                } else if (
                    uint8(cha[iChar]) == 101 || uint8(cha[iChar]) == 102
                ) {
                    x += -1;
                    y += -1;
                }
                if (y >= 128 || y < 0 || x >= 128 || x < 0) {
                    y = 64;
                    x = 64;
                    totalIndex = 0;
                }

                pixels[uint256(x) + (128 * uint256(127 - y))] = bytes1(
                    uint8(totalIndex / 38)
                );
                totalIndex += 1;
            }
        }
        return BytesUtils.MergeBytes(headers, pixels);
    }
}