// File: contracts/Strings.sol

library Strings {
    // via https://github.com/oraclize/ethereum-api/blob/master/oraclizeAPI_0.5.sol
    function strConcat(string _a, string _b, string _c, string _d, string _e) internal pure returns (string) {
        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);
        uint k = 0;
        for (uint i = 0; i < _ba.length; i++) babcde[k++] = _ba[i];
        for (i = 0; i < _bb.length; i++) babcde[k++] = _bb[i];
        for (i = 0; i < _bc.length; i++) babcde[k++] = _bc[i];
        for (i = 0; i < _bd.length; i++) babcde[k++] = _bd[i];
        for (i = 0; i < _be.length; i++) babcde[k++] = _be[i];
        return string(babcde);
    }

    function strConcat(string _a, string _b, string _c, string _d) internal pure returns (string) {
        return strConcat(_a, _b, _c, _d, "");
    }

    function strConcat(string _a, string _b, string _c) internal pure returns (string) {
        return strConcat(_a, _b, _c, "", "");
    }

    function strConcat(string _a, string _b) internal pure returns (string) {
        return strConcat(_a, _b, "", "", "");
    }

    function uint2str(uint i) internal pure returns (string) {
        if (i == 0) return "0";
        uint j = i;
        uint len;
        while (j != 0){
            len++;
            j /= 10;
        }
        bytes memory bstr = new bytes(len);
        uint k = len - 1;
        while (i != 0){
            bstr[k--] = byte(48 + i % 10);
            i /= 10;
        }
        return string(bstr);
    }
}

// File: openzeppelin-solidity/contracts/token/ERC721/ERC721Basic.sol

pragma solidity ^0.4.23;


/**
 * @title ERC721 Non-Fungible Token Standard basic interface
 * @dev see https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
 */
contract ERC721Basic {
  event Transfer(
    address indexed _from,
    address indexed _to,
    uint256 _tokenId
  );
  event Approval(
    address indexed _owner,
    address indexed _approved,
    uint256 _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 exists(uint256 _tokenId) public view returns (bool _exists);

  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;
}

// File: openzeppelin-solidity/contracts/token/ERC721/ERC721.sol

pragma solidity ^0.4.23;



/**
 * @title ERC-721 Non-Fungible Token Standard, optional enumeration extension
 * @dev See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
 */
contract ERC721Enumerable is ERC721Basic {
  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 ERC-721 Non-Fungible Token Standard, optional metadata extension
 * @dev See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
 */
contract ERC721Metadata is ERC721Basic {
  function name() public view returns (string _name);
  function symbol() public view returns (string _symbol);
  function tokenURI(uint256 _tokenId) public view returns (string);
}


/**
 * @title ERC-721 Non-Fungible Token Standard, full implementation interface
 * @dev See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
 */
contract ERC721 is ERC721Basic, ERC721Enumerable, ERC721Metadata {
}

// File: openzeppelin-solidity/contracts/token/ERC721/ERC721Receiver.sol

pragma solidity ^0.4.23;


/**
 * @title ERC721 token receiver interface
 * @dev Interface for any contract that wants to support safeTransfers
 *  from ERC721 asset contracts.
 */
contract ERC721Receiver {
  /**
   * @dev Magic value to be returned upon successful reception of an NFT
   *  Equals to `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`,
   *  which can be also obtained as `ERC721Receiver(0).onERC721Received.selector`
   */
  bytes4 constant ERC721_RECEIVED = 0xf0b9e5ba;

  /**
   * @notice Handle the receipt of an NFT
   * @dev The ERC721 smart contract calls this function on the recipient
   *  after a `safetransfer`. This function MAY throw to revert and reject the
   *  transfer. This function MUST use 50,000 gas or less. Return of other
   *  than the magic value MUST result in the transaction being reverted.
   *  Note: the contract address is always the message sender.
   * @param _from The sending address
   * @param _tokenId The NFT identifier which is being transfered
   * @param _data Additional data with no specified format
   * @return `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`
   */
  function onERC721Received(
    address _from,
    uint256 _tokenId,
    bytes _data
  )
    public
    returns(bytes4);
}

// File: openzeppelin-solidity/contracts/math/SafeMath.sol

pragma solidity ^0.4.23;


/**
 * @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;
  }
}

// File: openzeppelin-solidity/contracts/AddressUtils.sol

pragma solidity ^0.4.23;


/**
 * Utility library of inline functions on addresses
 */
library AddressUtils {

  /**
   * 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;
  }

}

// File: openzeppelin-solidity/contracts/token/ERC721/ERC721BasicToken.sol

pragma solidity ^0.4.23;






/**
 * @title ERC721 Non-Fungible Token Standard basic implementation
 * @dev see https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
 */
contract ERC721BasicToken is ERC721Basic {
  using SafeMath for uint256;
  using AddressUtils for address;

  // Equals to `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`
  // which can be also obtained as `ERC721Receiver(0).onERC721Received.selector`
  bytes4 constant ERC721_RECEIVED = 0xf0b9e5ba;

  // Mapping from token ID to owner
  mapping (uint256 => address) internal tokenOwner;

  // Mapping from token ID to approved address
  mapping (uint256 => address) internal tokenApprovals;

  // Mapping from owner to number of owned token
  mapping (address => uint256) internal ownedTokensCount;

  // Mapping from owner to operator approvals
  mapping (address => mapping (address => bool)) internal operatorApprovals;

  /**
   * @dev Guarantees msg.sender is owner of the given token
   * @param _tokenId uint256 ID of the token to validate its ownership belongs to msg.sender
   */
  modifier onlyOwnerOf(uint256 _tokenId) {
    require(ownerOf(_tokenId) == msg.sender);
    _;
  }

  /**
   * @dev Checks msg.sender can transfer a token, by being owner, approved, or operator
   * @param _tokenId uint256 ID of the token to validate
   */
  modifier canTransfer(uint256 _tokenId) {
    require(isApprovedOrOwner(msg.sender, _tokenId));
    _;
  }

  /**
   * @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 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) public view returns (bool) {
    address owner = tokenOwner[_tokenId];
    return owner != address(0);
  }

  /**
   * @dev Approves another address to transfer the given token ID
   * @dev The zero address indicates there is no approved address.
   * @dev There can only be one approved address per token at a given time.
   * @dev 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));

    if (getApproved(_tokenId) != address(0) || _to != address(0)) {
      tokenApprovals[_tokenId] = _to;
      emit Approval(owner, _to, _tokenId);
    }
  }

  /**
   * @dev Gets the approved address for a token ID, or zero if no address set
   * @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) {
    return tokenApprovals[_tokenId];
  }

  /**
   * @dev Sets or unsets the approval of a given operator
   * @dev 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
   * @dev Usage of this method is discouraged, use `safeTransferFrom` whenever possible
   * @dev 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
    canTransfer(_tokenId)
  {
    require(_from != address(0));
    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
   * @dev 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,uint256,bytes)"))`; otherwise,
   *  the transfer is reverted.
   * @dev 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
    canTransfer(_tokenId)
  {
    // solium-disable-next-line arg-overflow
    safeTransferFrom(_from, _to, _tokenId, "");
  }

  /**
   * @dev Safely transfers the ownership of a given token ID to another address
   * @dev 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,uint256,bytes)"))`; otherwise,
   *  the transfer is reverted.
   * @dev 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
    canTransfer(_tokenId)
  {
    transferFrom(_from, _to, _tokenId);
    // solium-disable-next-line arg-overflow
    require(checkAndCallSafeTransfer(_from, _to, _tokenId, _data));
  }

  /**
   * @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
   * @dev 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
   * @dev 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 clear current approval of a given token ID
   * @dev 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) internal {
    require(ownerOf(_tokenId) == _owner);
    if (tokenApprovals[_tokenId] != address(0)) {
      tokenApprovals[_tokenId] = address(0);
      emit Approval(_owner, address(0), _tokenId);
    }
  }

  /**
   * @dev Internal function to add a token ID to the list of a given address
   * @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
   * @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
   * @dev 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 checkAndCallSafeTransfer(
    address _from,
    address _to,
    uint256 _tokenId,
    bytes _data
  )
    internal
    returns (bool)
  {
    if (!_to.isContract()) {
      return true;
    }
    bytes4 retval = ERC721Receiver(_to).onERC721Received(
      _from, _tokenId, _data);
    return (retval == ERC721_RECEIVED);
  }
}

// File: openzeppelin-solidity/contracts/token/ERC721/ERC721Token.sol

pragma solidity ^0.4.23;




/**
 * @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 ERC721Token is ERC721, ERC721BasicToken {
  // Token name
  string internal name_;

  // Token symbol
  string internal symbol_;

  // Mapping from owner to list of owned token IDs
  mapping(address => uint256[]) internal ownedTokens;

  // Mapping from token ID to index of the owner tokens list
  mapping(uint256 => uint256) internal ownedTokensIndex;

  // Array with all token ids, used for enumeration
  uint256[] internal allTokens;

  // Mapping from token id to position in the allTokens array
  mapping(uint256 => uint256) internal allTokensIndex;

  // Optional mapping for token URIs
  mapping(uint256 => string) internal tokenURIs;

  /**
   * @dev Constructor function
   */
  constructor(string _name, string _symbol) public {
    name_ = _name;
    symbol_ = _symbol;
  }

  /**
   * @dev Gets the token name
   * @return string representing the token name
   */
  function name() public view returns (string) {
    return name_;
  }

  /**
   * @dev Gets the token symbol
   * @return string representing the token symbol
   */
  function symbol() public view returns (string) {
    return symbol_;
  }

  /**
   * @dev Returns an URI for a given token ID
   * @dev 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) public view returns (string) {
    require(exists(_tokenId));
    return tokenURIs[_tokenId];
  }

  /**
   * @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
   * @dev 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 set the token URI for a given token
   * @dev 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 add a token ID to the list of a given address
   * @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
   * @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);

    uint256 tokenIndex = ownedTokensIndex[_tokenId];
    uint256 lastTokenIndex = ownedTokens[_from].length.sub(1);
    uint256 lastToken = ownedTokens[_from][lastTokenIndex];

    ownedTokens[_from][tokenIndex] = lastToken;
    ownedTokens[_from][lastTokenIndex] = 0;
    // 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

    ownedTokens[_from].length--;
    ownedTokensIndex[_tokenId] = 0;
    ownedTokensIndex[lastToken] = tokenIndex;
  }

  /**
   * @dev Internal function to mint a new token
   * @dev 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
   * @dev 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];
    }

    // 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;
  }

}

// File: openzeppelin-solidity/contracts/ownership/Ownable.sol

pragma solidity ^0.4.23;


/**
 * @title Ownable
 * @dev The Ownable contract has an owner address, and provides basic authorization control
 * functions, this simplifies the implementation of "user permissions".
 */
contract Ownable {
  address public owner;


  event OwnershipRenounced(address indexed previousOwner);
  event OwnershipTransferred(
    address indexed previousOwner,
    address indexed newOwner
  );


  /**
   * @dev The Ownable constructor sets the original `owner` of the contract to the sender
   * account.
   */
  constructor() public {
    owner = msg.sender;
  }

  /**
   * @dev Throws if called by any account other than the owner.
   */
  modifier onlyOwner() {
    require(msg.sender == owner);
    _;
  }

  /**
   * @dev Allows the current owner to relinquish control of the contract.
   */
  function renounceOwnership() public onlyOwner {
    emit OwnershipRenounced(owner);
    owner = address(0);
  }

  /**
   * @dev Allows the current owner to transfer control of the contract to a newOwner.
   * @param _newOwner The address to transfer ownership to.
   */
  function transferOwnership(address _newOwner) public onlyOwner {
    _transferOwnership(_newOwner);
  }

  /**
   * @dev Transfers control of the contract to a newOwner.
   * @param _newOwner The address to transfer ownership to.
   */
  function _transferOwnership(address _newOwner) internal {
    require(_newOwner != address(0));
    emit OwnershipTransferred(owner, _newOwner);
    owner = _newOwner;
  }
}

// File: contracts/TradeableERC721Token.sol

/*
Abstract contract which allows trading to some external (contract) party

Mostly copied from OpenSea https://github.com/ProjectOpenSea/opensea-creatures/blob/master/contracts/TradeableERC721Token.sol

*/
pragma solidity ^0.4.25;







contract OwnableDelegateProxy { }

contract ProxyRegistry {
    mapping(address => OwnableDelegateProxy) public proxies;
}

/**
 * @title TradeableERC721Token
 * TradeableERC721Token - ERC721 contract that whitelists a trading address, and has minting functionality.
 */
contract TradeableERC721Token is ERC721Token, Ownable {
    using SafeMath for uint256;
    using Strings for string;

    uint256 burnedCounter = 0;
    address proxyRegistryAddress;
    string baseURI;

    constructor(string _name, string _symbol, address _proxyRegistryAddress, string _baseTokenURI) ERC721Token(_name, _symbol) public {
        proxyRegistryAddress = _proxyRegistryAddress;
        baseURI = _baseTokenURI;
    }

    /**
      * @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);
    }

    /**
   * @dev Approves another address to transfer the given array of token IDs
   * @param _to address to be approved for the given token ID
   * @param _tokenIds uint256[] IDs of the tokens to be approved
   */
    function approveBulk(address _to, uint256[] _tokenIds) public {
        for (uint256 i = 0; i < _tokenIds.length; i++) {
           approve(_to, _tokenIds[i]);
        }
    }

    /**
      * @dev calculates the next token ID based on totalSupply and the burned offset
      * @return uint256 for the next token ID
      */
    function _getNextTokenId() private view returns (uint256) {
        return totalSupply().add(1).add(burnedCounter);
    }

    /**
      * @dev extends default burn functionality with the the burned counter
      */
    function _burn(address _owner, uint256 _tokenId) internal {
        super._burn(_owner, _tokenId);
        burnedCounter++;
    }

    function baseTokenURI() public view returns (string) {
        return baseURI;
    }

    function tokenURI(uint256 _tokenId) public view returns (string) {
        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)
    {
        //Check optional proxy
        if (proxyRegistryAddress != address(0)) {
            // Whitelist OpenSea proxy contract for easy trading.
            ProxyRegistry proxyRegistry = ProxyRegistry(proxyRegistryAddress);
            if (proxyRegistry.proxies(owner) == operator) {
                return true;
            }
        }

        return super.isApprovedForAll(owner, operator);
    }

    /// @notice Returns a list of all tokens assigned to an address.
    /// @param _owner The owner whose tokens we are interested in.
    /// @dev This method MUST NEVER be called by smart contract code, due to the price
    function tokensOfOwner(address _owner) external view returns(uint256[] ownerTokens) {
        uint256 tokenCount = balanceOf(_owner);

        if (tokenCount == 0) {
            // Return an empty array
            return new uint256[](0);
        } else {
            uint256[] memory result = new uint256[](tokenCount);
            uint256 resultIndex = 0;

            uint256 _tokenIdx;

            for (_tokenIdx = 0; _tokenIdx < tokenCount; _tokenIdx++) {
                result[resultIndex] = tokenOfOwnerByIndex(_owner, _tokenIdx);
                resultIndex++;
            }

            return result;
        }
    }
}

// File: openzeppelin-solidity/contracts/token/ERC20/ERC20Basic.sol

pragma solidity ^0.4.23;


/**
 * @title ERC20Basic
 * @dev Simpler version of ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/179
 */
contract ERC20Basic {
  function totalSupply() public view returns (uint256);
  function balanceOf(address who) public view returns (uint256);
  function transfer(address to, uint256 value) public returns (bool);
  event Transfer(address indexed from, address indexed to, uint256 value);
}

// File: openzeppelin-solidity/contracts/token/ERC20/ERC20.sol

pragma solidity ^0.4.23;



/**
 * @title ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
contract ERC20 is ERC20Basic {
  function allowance(address owner, address spender)
    public view returns (uint256);

  function transferFrom(address from, address to, uint256 value)
    public returns (bool);

  function approve(address spender, uint256 value) public returns (bool);
  event Approval(
    address indexed owner,
    address indexed spender,
    uint256 value
  );
}

// File: contracts/ERC20Box.sol

pragma solidity ^0.4.25;



/**
 * @title ERC20Box
 *
 * A tradable box (ERC-721), OpenSee.io compliant, which holds a portion of ERC-20 tokens,
 * that get credited to the owner upon 'opening' it
 */
contract ERC20Box is TradeableERC721Token {

    ERC20 public token;

    uint256 tokensPerBox;

    /**
   * @dev Constructor function
   * Important! This token is not functional until depositERC() is called
   */
    constructor(string _name, string _symbol, address _proxyRegistryAddress, address _tokenAddress,
    uint256 _tokensPerBox, string _baseTokenURI)
    TradeableERC721Token(_name, _symbol, _proxyRegistryAddress, _baseTokenURI) public {
        token = ERC20(_tokenAddress);
        tokensPerBox = _tokensPerBox;
    }

    // Important! remember to call ERC20(address).approve(this, amount)
    // or this contract will not be able to do the transfer on your behalf.
    function depositERC(uint256 amount) onlyOwner public {
        require(amount % tokensPerBox == 0, "Wrong amount of tokens!");
        require(token.transferFrom(msg.sender, this, amount), "Insufficient funds");
        for(uint i = 0; i < amount.div(tokensPerBox); i++) {
            mintTo(msg.sender);
        }
    }

    function unpack(uint256 _tokenId) public onlyOwnerOf(_tokenId){
        require(token.balanceOf(this) >= tokensPerBox, "Hmm, been opened already?");
        require(token.transfer(msg.sender, tokensPerBox), "Couldn't transfer token");

        // Burn the box.
        _burn(msg.sender, _tokenId);
    }

    /**
   * @dev OpenSee compatibility, expects user-friendly number
   */
    function itemsPerLootbox() public view returns (uint256) {
        return tokensPerBox.div(10**18);
    }
}