pragma solidity ^0.4.24;

// File: zeppelin-solidity/contracts/introspection/ERC165.sol

/**
 * @title ERC165
 * @dev https://github.com/ethereum/EIPs/blob/master/EIPS/eip-165.md
 */
interface ERC165 {

  /**
   * @notice Query if a contract implements an interface
   * @param _interfaceId The interface identifier, as specified in ERC-165
   * @dev Interface identification is specified in ERC-165. This function
   * uses less than 30,000 gas.
   */
  function supportsInterface(bytes4 _interfaceId)
    external
    view
    returns (bool);
}

// File: zeppelin-solidity/contracts/token/ERC721/ERC721Basic.sol

/**
 * @title ERC721 Non-Fungible Token Standard basic interface
 * @dev see https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
 */
contract ERC721Basic is ERC165 {

  bytes4 internal constant InterfaceId_ERC721 = 0x80ac58cd;
  /*
   * 0x80ac58cd ===
   *   bytes4(keccak256('balanceOf(address)')) ^
   *   bytes4(keccak256('ownerOf(uint256)')) ^
   *   bytes4(keccak256('approve(address,uint256)')) ^
   *   bytes4(keccak256('getApproved(uint256)')) ^
   *   bytes4(keccak256('setApprovalForAll(address,bool)')) ^
   *   bytes4(keccak256('isApprovedForAll(address,address)')) ^
   *   bytes4(keccak256('transferFrom(address,address,uint256)')) ^
   *   bytes4(keccak256('safeTransferFrom(address,address,uint256)')) ^
   *   bytes4(keccak256('safeTransferFrom(address,address,uint256,bytes)'))
   */

  bytes4 internal constant InterfaceId_ERC721Exists = 0x4f558e79;
  /*
   * 0x4f558e79 ===
   *   bytes4(keccak256('exists(uint256)'))
   */

  bytes4 internal constant InterfaceId_ERC721Enumerable = 0x780e9d63;
  /**
   * 0x780e9d63 ===
   *   bytes4(keccak256('totalSupply()')) ^
   *   bytes4(keccak256('tokenOfOwnerByIndex(address,uint256)')) ^
   *   bytes4(keccak256('tokenByIndex(uint256)'))
   */

  bytes4 internal constant InterfaceId_ERC721Metadata = 0x5b5e139f;
  /**
   * 0x5b5e139f ===
   *   bytes4(keccak256('name()')) ^
   *   bytes4(keccak256('symbol()')) ^
   *   bytes4(keccak256('tokenURI(uint256)'))
   */

  event Transfer(
    address indexed _from,
    address indexed _to,
    uint256 indexed _tokenId
  );
  event Approval(
    address indexed _owner,
    address indexed _approved,
    uint256 indexed _tokenId
  );
  event ApprovalForAll(
    address indexed _owner,
    address indexed _operator,
    bool _approved
  );

  function balanceOf(address _owner) public view returns (uint256 _balance);
  function ownerOf(uint256 _tokenId) public view returns (address _owner);
  function 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: zeppelin-solidity/contracts/token/ERC721/ERC721.sol

/**
 * @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() external view returns (string _name);
  function symbol() external 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: zeppelin-solidity/contracts/token/ERC721/ERC721Receiver.sol

/**
 * @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,address,uint256,bytes)"))`,
   *  which can be also obtained as `ERC721Receiver(0).onERC721Received.selector`
   */
  bytes4 internal constant ERC721_RECEIVED = 0x150b7a02;

  /**
   * @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. Return of other than the magic value MUST result in the
   * transaction being reverted.
   * Note: the contract address is always the message sender.
   * @param _operator The address which called `safeTransferFrom` function
   * @param _from The address which previously owned the token
   * @param _tokenId The NFT identifier which is being transferred
   * @param _data Additional data with no specified format
   * @return `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
   */
  function onERC721Received(
    address _operator,
    address _from,
    uint256 _tokenId,
    bytes _data
  )
    public
    returns(bytes4);
}

// File: zeppelin-solidity/contracts/math/SafeMath.sol

/**
 * @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: zeppelin-solidity/contracts/AddressUtils.sol

/**
 * 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: zeppelin-solidity/contracts/introspection/SupportsInterfaceWithLookup.sol

/**
 * @title SupportsInterfaceWithLookup
 * @author Matt Condon (@shrugs)
 * @dev Implements ERC165 using a lookup table.
 */
contract SupportsInterfaceWithLookup is ERC165 {

  bytes4 public constant InterfaceId_ERC165 = 0x01ffc9a7;
  /**
   * 0x01ffc9a7 ===
   *   bytes4(keccak256('supportsInterface(bytes4)'))
   */

  /**
   * @dev a mapping of interface id to whether or not it's supported
   */
  mapping(bytes4 => bool) internal supportedInterfaces;

  /**
   * @dev A contract implementing SupportsInterfaceWithLookup
   * implement ERC165 itself
   */
  constructor()
    public
  {
    _registerInterface(InterfaceId_ERC165);
  }

  /**
   * @dev implement supportsInterface(bytes4) using a lookup table
   */
  function supportsInterface(bytes4 _interfaceId)
    external
    view
    returns (bool)
  {
    return supportedInterfaces[_interfaceId];
  }

  /**
   * @dev private method for registering an interface
   */
  function _registerInterface(bytes4 _interfaceId)
    internal
  {
    require(_interfaceId != 0xffffffff);
    supportedInterfaces[_interfaceId] = true;
  }
}

// File: zeppelin-solidity/contracts/token/ERC721/ERC721BasicToken.sol

/**
 * @title ERC721 Non-Fungible Token Standard basic implementation
 * @dev see https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
 */
contract ERC721BasicToken is SupportsInterfaceWithLookup, ERC721Basic {

  using SafeMath for uint256;
  using AddressUtils for address;

  // Equals to `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
  // which can be also obtained as `ERC721Receiver(0).onERC721Received.selector`
  bytes4 private constant ERC721_RECEIVED = 0x150b7a02;

  // 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;

  constructor()
    public
  {
    // register the supported interfaces to conform to ERC721 via ERC165
    _registerInterface(InterfaceId_ERC721);
    _registerInterface(InterfaceId_ERC721Exists);
  }

  /**
   * @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
   * The zero address indicates there is no approved address.
   * There can only be one approved address per token at a given time.
   * Can only be called by the token owner or an approved operator.
   * @param _to address to be approved for the given token ID
   * @param _tokenId uint256 ID of the token to be approved
   */
  function approve(address _to, uint256 _tokenId) public {
    address owner = ownerOf(_tokenId);
    require(_to != owner);
    require(msg.sender == owner || isApprovedForAll(owner, msg.sender));

    tokenApprovals[_tokenId] = _to;
    emit Approval(owner, _to, _tokenId);
  }

  /**
   * @dev Gets the approved address for a token ID, or zero if no address set
   * @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
   * An operator is allowed to transfer all tokens of the sender on their behalf
   * @param _to operator address to set the approval
   * @param _approved representing the status of the approval to be set
   */
  function setApprovalForAll(address _to, bool _approved) public {
    require(_to != msg.sender);
    operatorApprovals[msg.sender][_to] = _approved;
    emit ApprovalForAll(msg.sender, _to, _approved);
  }

  /**
   * @dev Tells whether an operator is approved by a given owner
   * @param _owner owner address which you want to query the approval of
   * @param _operator operator address which you want to query the approval of
   * @return bool whether the given operator is approved by the given owner
   */
  function isApprovedForAll(
    address _owner,
    address _operator
  )
    public
    view
    returns (bool)
  {
    return operatorApprovals[_owner][_operator];
  }

  /**
   * @dev Transfers the ownership of a given token ID to another address
   * Usage of this method is discouraged, use `safeTransferFrom` whenever possible
   * Requires the msg sender to be the owner, approved, or operator
   * @param _from current owner of the token
   * @param _to address to receive the ownership of the given token ID
   * @param _tokenId uint256 ID of the token to be transferred
  */
  function transferFrom(
    address _from,
    address _to,
    uint256 _tokenId
  )
    public
  {
    require(isApprovedOrOwner(msg.sender, _tokenId));
    require(_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
   * If the target address is a contract, it must implement `onERC721Received`,
   * which is called upon a safe transfer, and return the magic value
   * `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`; otherwise,
   * the transfer is reverted.
   *
   * Requires the msg sender to be the owner, approved, or operator
   * @param _from current owner of the token
   * @param _to address to receive the ownership of the given token ID
   * @param _tokenId uint256 ID of the token to be transferred
  */
  function safeTransferFrom(
    address _from,
    address _to,
    uint256 _tokenId
  )
    public
  {
    // solium-disable-next-line arg-overflow
    safeTransferFrom(_from, _to, _tokenId, "");
  }

  /**
   * @dev Safely transfers the ownership of a given token ID to another address
   * If the target address is a contract, it must implement `onERC721Received`,
   * which is called upon a safe transfer, and return the magic value
   * `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`; otherwise,
   * the transfer is reverted.
   * Requires the msg sender to be the owner, approved, or operator
   * @param _from current owner of the token
   * @param _to address to receive the ownership of the given token ID
   * @param _tokenId uint256 ID of the token to be transferred
   * @param _data bytes data to send along with a safe transfer check
   */
  function safeTransferFrom(
    address _from,
    address _to,
    uint256 _tokenId,
    bytes _data
  )
    public
  {
    transferFrom(_from, _to, _tokenId);
    // solium-disable-next-line arg-overflow
    require(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
   * Reverts if the given token ID already exists
   * @param _to The address that will own the minted token
   * @param _tokenId uint256 ID of the token to be minted by the msg.sender
   */
  function _mint(address _to, uint256 _tokenId) internal {
    require(_to != address(0));
    addTokenTo(_to, _tokenId);
    emit Transfer(address(0), _to, _tokenId);
  }

  /**
   * @dev Internal function to burn a specific token
   * Reverts if the token does not exist
   * @param _tokenId uint256 ID of the token being burned by the msg.sender
   */
  function _burn(address _owner, uint256 _tokenId) internal {
    clearApproval(_owner, _tokenId);
    removeTokenFrom(_owner, _tokenId);
    emit Transfer(_owner, address(0), _tokenId);
  }

  /**
   * @dev Internal function to clear current approval of a given token ID
   * Reverts if the given address is not indeed the owner of the token
   * @param _owner owner of the token
   * @param _tokenId uint256 ID of the token to be transferred
   */
  function clearApproval(address _owner, uint256 _tokenId) internal {
    require(ownerOf(_tokenId) == _owner);
    if (tokenApprovals[_tokenId] != address(0)) {
      tokenApprovals[_tokenId] = address(0);
    }
  }

  /**
   * @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
   * 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(
      msg.sender, _from, _tokenId, _data);
    return (retval == ERC721_RECEIVED);
  }
}

// File: zeppelin-solidity/contracts/token/ERC721/ERC721Token.sol

/**
 * @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 SupportsInterfaceWithLookup, ERC721BasicToken, ERC721 {

  // 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;

    // register the supported interfaces to conform to ERC721 via ERC165
    _registerInterface(InterfaceId_ERC721Enumerable);
    _registerInterface(InterfaceId_ERC721Metadata);
  }

  /**
   * @dev Gets the token name
   * @return string representing the token name
   */
  function name() external view returns (string) {
    return name_;
  }

  /**
   * @dev Gets the token symbol
   * @return string representing the token symbol
   */
  function symbol() external view returns (string) {
    return symbol_;
  }

  /**
   * @dev Returns an URI for a given token ID
   * Throws if the token ID does not exist. May return an empty string.
   * @param _tokenId uint256 ID of the token to query
   */
  function tokenURI(uint256 _tokenId) 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
   * 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
   * 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);

    // To prevent a gap in the array, we store the last token in the index of the token to delete, and
    // then delete the last slot.
    uint256 tokenIndex = ownedTokensIndex[_tokenId];
    uint256 lastTokenIndex = ownedTokens[_from].length.sub(1);
    uint256 lastToken = ownedTokens[_from][lastTokenIndex];

    ownedTokens[_from][tokenIndex] = lastToken;
    // This also deletes the contents at the last position of the array
    ownedTokens[_from].length--;

    // Note that this will handle single-element arrays. In that case, both tokenIndex and lastTokenIndex are going to
    // be zero. Then we can make sure that we will remove _tokenId from the ownedTokens list since we are first swapping
    // the lastToken to the first position, and then dropping the element placed in the last position of the list

    ownedTokensIndex[_tokenId] = 0;
    ownedTokensIndex[lastToken] = tokenIndex;
  }

  /**
   * @dev Internal function to mint a new token
   * Reverts if the given token ID already exists
   * @param _to address the beneficiary that will own the minted token
   * @param _tokenId uint256 ID of the token to be minted by the msg.sender
   */
  function _mint(address _to, uint256 _tokenId) internal {
    super._mint(_to, _tokenId);

    allTokensIndex[_tokenId] = allTokens.length;
    allTokens.push(_tokenId);
  }

  /**
   * @dev Internal function to burn a specific token
   * Reverts if the token does not exist
   * @param _owner owner of the token to burn
   * @param _tokenId uint256 ID of the token being burned by the msg.sender
   */
  function _burn(address _owner, uint256 _tokenId) internal {
    super._burn(_owner, _tokenId);

    // 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: @ensdomains/ens/contracts/Deed.sol

/**
 * @title Deed to hold ether in exchange for ownership of a node
 * @dev The deed can be controlled only by the registrar and can only send ether back to the owner.
 */
contract Deed {

    address constant burn = 0xdead;

    address public registrar;
    address public owner;
    address public previousOwner;

    uint public creationDate;
    uint public value;

    bool active;

    event OwnerChanged(address newOwner);
    event DeedClosed();

    modifier onlyRegistrar {
        require(msg.sender == registrar);
        _;
    }

    modifier onlyActive {
        require(active);
        _;
    }

    function Deed(address _owner) public payable {
        owner = _owner;
        registrar = msg.sender;
        creationDate = now;
        active = true;
        value = msg.value;
    }

    function setOwner(address newOwner) public onlyRegistrar {
        require(newOwner != 0);
        previousOwner = owner;  // This allows contracts to check who sent them the ownership
        owner = newOwner;
        OwnerChanged(newOwner);
    }

    function setRegistrar(address newRegistrar) public onlyRegistrar {
        registrar = newRegistrar;
    }

    function setBalance(uint newValue, bool throwOnFailure) public onlyRegistrar onlyActive {
        // Check if it has enough balance to set the value
        require(value >= newValue);
        value = newValue;
        // Send the difference to the owner
        require(owner.send(this.balance - newValue) || !throwOnFailure);
    }

    /**
     * @dev Close a deed and refund a specified fraction of the bid value
     *
     * @param refundRatio The amount*1/1000 to refund
     */
    function closeDeed(uint refundRatio) public onlyRegistrar onlyActive {
        active = false;
        require(burn.send(((1000 - refundRatio) * this.balance)/1000));
        DeedClosed();
        destroyDeed();
    }

    /**
     * @dev Close a deed and refund a specified fraction of the bid value
     */
    function destroyDeed() public {
        require(!active);

        // Instead of selfdestruct(owner), invoke owner fallback function to allow
        // owner to log an event if desired; but owner should also be aware that
        // its fallback function can also be invoked by setBalance
        if (owner.send(this.balance)) {
            selfdestruct(burn);
        }
    }
}

// File: @ensdomains/ens/contracts/ENS.sol

interface ENS {

    // Logged when the owner of a node assigns a new owner to a subnode.
    event NewOwner(bytes32 indexed node, bytes32 indexed label, address owner);

    // Logged when the owner of a node transfers ownership to a new account.
    event Transfer(bytes32 indexed node, address owner);

    // Logged when the resolver for a node changes.
    event NewResolver(bytes32 indexed node, address resolver);

    // Logged when the TTL of a node changes
    event NewTTL(bytes32 indexed node, uint64 ttl);


    function setSubnodeOwner(bytes32 node, bytes32 label, address owner) public;
    function setResolver(bytes32 node, address resolver) public;
    function setOwner(bytes32 node, address owner) public;
    function setTTL(bytes32 node, uint64 ttl) public;
    function owner(bytes32 node) public view returns (address);
    function resolver(bytes32 node) public view returns (address);
    function ttl(bytes32 node) public view returns (uint64);

}

// File: @ensdomains/ens/contracts/HashRegistrarSimplified.sol

/*

Temporary Hash Registrar
========================

This is a simplified version of a hash registrar. It is purporsefully limited:
names cannot be six letters or shorter, new auctions will stop after 4 years.

The plan is to test the basic features and then move to a new contract in at most
2 years, when some sort of renewal mechanism will be enabled.
*/



/**
 * @title Registrar
 * @dev The registrar handles the auction process for each subnode of the node it owns.
 */
contract Registrar {
    ENS public ens;
    bytes32 public rootNode;

    mapping (bytes32 => Entry) _entries;
    mapping (address => mapping (bytes32 => Deed)) public sealedBids;
    
    enum Mode { Open, Auction, Owned, Forbidden, Reveal, NotYetAvailable }

    uint32 constant totalAuctionLength = 5 days;
    uint32 constant revealPeriod = 48 hours;
    uint32 public constant launchLength = 8 weeks;

    uint constant minPrice = 0.01 ether;
    uint public registryStarted;

    event AuctionStarted(bytes32 indexed hash, uint registrationDate);
    event NewBid(bytes32 indexed hash, address indexed bidder, uint deposit);
    event BidRevealed(bytes32 indexed hash, address indexed owner, uint value, uint8 status);
    event HashRegistered(bytes32 indexed hash, address indexed owner, uint value, uint registrationDate);
    event HashReleased(bytes32 indexed hash, uint value);
    event HashInvalidated(bytes32 indexed hash, string indexed name, uint value, uint registrationDate);

    struct Entry {
        Deed deed;
        uint registrationDate;
        uint value;
        uint highestBid;
    }

    modifier inState(bytes32 _hash, Mode _state) {
        require(state(_hash) == _state);
        _;
    }

    modifier onlyOwner(bytes32 _hash) {
        require(state(_hash) == Mode.Owned && msg.sender == _entries[_hash].deed.owner());
        _;
    }

    modifier registryOpen() {
        require(now >= registryStarted && now <= registryStarted + 4 years && ens.owner(rootNode) == address(this));
        _;
    }

    /**
     * @dev Constructs a new Registrar, with the provided address as the owner of the root node.
     *
     * @param _ens The address of the ENS
     * @param _rootNode The hash of the rootnode.
     */
    function Registrar(ENS _ens, bytes32 _rootNode, uint _startDate) public {
        ens = _ens;
        rootNode = _rootNode;
        registryStarted = _startDate > 0 ? _startDate : now;
    }

    /**
     * @dev Start an auction for an available hash
     *
     * @param _hash The hash to start an auction on
     */
    function startAuction(bytes32 _hash) public registryOpen() {
        Mode mode = state(_hash);
        if (mode == Mode.Auction) return;
        require(mode == Mode.Open);

        Entry storage newAuction = _entries[_hash];
        newAuction.registrationDate = now + totalAuctionLength;
        newAuction.value = 0;
        newAuction.highestBid = 0;
        AuctionStarted(_hash, newAuction.registrationDate);
    }

    /**
     * @dev Start multiple auctions for better anonymity
     *
     * Anyone can start an auction by sending an array of hashes that they want to bid for.
     * Arrays are sent so that someone can open up an auction for X dummy hashes when they
     * are only really interested in bidding for one. This will increase the cost for an
     * attacker to simply bid blindly on all new auctions. Dummy auctions that are
     * open but not bid on are closed after a week.
     *
     * @param _hashes An array of hashes, at least one of which you presumably want to bid on
     */
    function startAuctions(bytes32[] _hashes) public {
        for (uint i = 0; i < _hashes.length; i ++) {
            startAuction(_hashes[i]);
        }
    }

    /**
     * @dev Submit a new sealed bid on a desired hash in a blind auction
     *
     * Bids are sent by sending a message to the main contract with a hash and an amount. The hash
     * contains information about the bid, including the bidded hash, the bid amount, and a random
     * salt. Bids are not tied to any one auction until they are revealed. The value of the bid
     * itself can be masqueraded by sending more than the value of your actual bid. This is
     * followed by a 48h reveal period. Bids revealed after this period will be burned and the ether unrecoverable.
     * Since this is an auction, it is expected that most public hashes, like known domains and common dictionary
     * words, will have multiple bidders pushing the price up.
     *
     * @param sealedBid A sealedBid, created by the shaBid function
     */
    function newBid(bytes32 sealedBid) public payable {
        require(address(sealedBids[msg.sender][sealedBid]) == 0x0);
        require(msg.value >= minPrice);

        // Creates a new hash contract with the owner
        Deed newBid = (new Deed).value(msg.value)(msg.sender);
        sealedBids[msg.sender][sealedBid] = newBid;
        NewBid(sealedBid, msg.sender, msg.value);
    }

    /**
     * @dev Start a set of auctions and bid on one of them
     *
     * This method functions identically to calling `startAuctions` followed by `newBid`,
     * but all in one transaction.
     *
     * @param hashes A list of hashes to start auctions on.
     * @param sealedBid A sealed bid for one of the auctions.
     */
    function startAuctionsAndBid(bytes32[] hashes, bytes32 sealedBid) public payable {
        startAuctions(hashes);
        newBid(sealedBid);
    }

    /**
     * @dev Submit the properties of a bid to reveal them
     *
     * @param _hash The node in the sealedBid
     * @param _value The bid amount in the sealedBid
     * @param _salt The sale in the sealedBid
     */
    function unsealBid(bytes32 _hash, uint _value, bytes32 _salt) public {
        bytes32 seal = shaBid(_hash, msg.sender, _value, _salt);
        Deed bid = sealedBids[msg.sender][seal];
        require(address(bid) != 0);

        sealedBids[msg.sender][seal] = Deed(0);
        Entry storage h = _entries[_hash];
        uint value = min(_value, bid.value());
        bid.setBalance(value, true);

        var auctionState = state(_hash);
        if (auctionState == Mode.Owned) {
            // Too late! Bidder loses their bid. Gets 0.5% back.
            bid.closeDeed(5);
            BidRevealed(_hash, msg.sender, value, 1);
        } else if (auctionState != Mode.Reveal) {
            // Invalid phase
            revert();
        } else if (value < minPrice || bid.creationDate() > h.registrationDate - revealPeriod) {
            // Bid too low or too late, refund 99.5%
            bid.closeDeed(995);
            BidRevealed(_hash, msg.sender, value, 0);
        } else if (value > h.highestBid) {
            // New winner
            // Cancel the other bid, refund 99.5%
            if (address(h.deed) != 0) {
                Deed previousWinner = h.deed;
                previousWinner.closeDeed(995);
            }

            // Set new winner
            // Per the rules of a vickery auction, the value becomes the previous highestBid
            h.value = h.highestBid;  // will be zero if there's only 1 bidder
            h.highestBid = value;
            h.deed = bid;
            BidRevealed(_hash, msg.sender, value, 2);
        } else if (value > h.value) {
            // Not winner, but affects second place
            h.value = value;
            bid.closeDeed(995);
            BidRevealed(_hash, msg.sender, value, 3);
        } else {
            // Bid doesn't affect auction
            bid.closeDeed(995);
            BidRevealed(_hash, msg.sender, value, 4);
        }
    }

    /**
     * @dev Cancel a bid
     *
     * @param seal The value returned by the shaBid function
     */
    function cancelBid(address bidder, bytes32 seal) public {
        Deed bid = sealedBids[bidder][seal];
        
        // If a sole bidder does not `unsealBid` in time, they have a few more days
        // where they can call `startAuction` (again) and then `unsealBid` during
        // the revealPeriod to get back their bid value.
        // For simplicity, they should call `startAuction` within
        // 9 days (2 weeks - totalAuctionLength), otherwise their bid will be
        // cancellable by anyone.
        require(address(bid) != 0 && now >= bid.creationDate() + totalAuctionLength + 2 weeks);

        // Send the canceller 0.5% of the bid, and burn the rest.
        bid.setOwner(msg.sender);
        bid.closeDeed(5);
        sealedBids[bidder][seal] = Deed(0);
        BidRevealed(seal, bidder, 0, 5);
    }

    /**
     * @dev Finalize an auction after the registration date has passed
     *
     * @param _hash The hash of the name the auction is for
     */
    function finalizeAuction(bytes32 _hash) public onlyOwner(_hash) {
        Entry storage h = _entries[_hash];
        
        // Handles the case when there's only a single bidder (h.value is zero)
        h.value =  max(h.value, minPrice);
        h.deed.setBalance(h.value, true);

        trySetSubnodeOwner(_hash, h.deed.owner());
        HashRegistered(_hash, h.deed.owner(), h.value, h.registrationDate);
    }

    /**
     * @dev The owner of a domain may transfer it to someone else at any time.
     *
     * @param _hash The node to transfer
     * @param newOwner The address to transfer ownership to
     */
    function transfer(bytes32 _hash, address newOwner) public onlyOwner(_hash) {
        require(newOwner != 0);

        Entry storage h = _entries[_hash];
        h.deed.setOwner(newOwner);
        trySetSubnodeOwner(_hash, newOwner);
    }

    /**
     * @dev After some time, or if we're no longer the registrar, the owner can release
     *      the name and get their ether back.
     *
     * @param _hash The node to release
     */
    function releaseDeed(bytes32 _hash) public onlyOwner(_hash) {
        Entry storage h = _entries[_hash];
        Deed deedContract = h.deed;

        require(now >= h.registrationDate + 1 years || ens.owner(rootNode) != address(this));

        h.value = 0;
        h.highestBid = 0;
        h.deed = Deed(0);

        _tryEraseSingleNode(_hash);
        deedContract.closeDeed(1000);
        HashReleased(_hash, h.value);        
    }

    /**
     * @dev Submit a name 6 characters long or less. If it has been registered,
     *      the submitter will earn 50% of the deed value. 
     * 
     * We are purposefully handicapping the simplified registrar as a way 
     * to force it into being restructured in a few years.
     *
     * @param unhashedName An invalid name to search for in the registry.
     */
    function invalidateName(string unhashedName) public inState(keccak256(unhashedName), Mode.Owned) {
        require(strlen(unhashedName) <= 6);
        bytes32 hash = keccak256(unhashedName);

        Entry storage h = _entries[hash];

        _tryEraseSingleNode(hash);

        if (address(h.deed) != 0) {
            // Reward the discoverer with 50% of the deed
            // The previous owner gets 50%
            h.value = max(h.value, minPrice);
            h.deed.setBalance(h.value/2, false);
            h.deed.setOwner(msg.sender);
            h.deed.closeDeed(1000);
        }

        HashInvalidated(hash, unhashedName, h.value, h.registrationDate);

        h.value = 0;
        h.highestBid = 0;
        h.deed = Deed(0);
    }

    /**
     * @dev Allows anyone to delete the owner and resolver records for a (subdomain of) a
     *      name that is not currently owned in the registrar. If passing, eg, 'foo.bar.eth',
     *      the owner and resolver fields on 'foo.bar.eth' and 'bar.eth' will all be cleared.
     *
     * @param labels A series of label hashes identifying the name to zero out, rooted at the
     *        registrar's root. Must contain at least one element. For instance, to zero 
     *        'foo.bar.eth' on a registrar that owns '.eth', pass an array containing
     *        [keccak256('foo'), keccak256('bar')].
     */
    function eraseNode(bytes32[] labels) public {
        require(labels.length != 0);
        require(state(labels[labels.length - 1]) != Mode.Owned);

        _eraseNodeHierarchy(labels.length - 1, labels, rootNode);
    }

    /**
     * @dev Transfers the deed to the current registrar, if different from this one.
     *
     * Used during the upgrade process to a permanent registrar.
     *
     * @param _hash The name hash to transfer.
     */
    function transferRegistrars(bytes32 _hash) public onlyOwner(_hash) {
        address registrar = ens.owner(rootNode);
        require(registrar != address(this));

        // Migrate the deed
        Entry storage h = _entries[_hash];
        h.deed.setRegistrar(registrar);

        // Call the new registrar to accept the transfer
        Registrar(registrar).acceptRegistrarTransfer(_hash, h.deed, h.registrationDate);

        // Zero out the Entry
        h.deed = Deed(0);
        h.registrationDate = 0;
        h.value = 0;
        h.highestBid = 0;
    }

    /**
     * @dev Accepts a transfer from a previous registrar; stubbed out here since there
     *      is no previous registrar implementing this interface.
     *
     * @param hash The sha3 hash of the label to transfer.
     * @param deed The Deed object for the name being transferred in.
     * @param registrationDate The date at which the name was originally registered.
     */
    function acceptRegistrarTransfer(bytes32 hash, Deed deed, uint registrationDate) public {
        hash; deed; registrationDate; // Don't warn about unused variables
    }

    // State transitions for names:
    //   Open -> Auction (startAuction)
    //   Auction -> Reveal
    //   Reveal -> Owned
    //   Reveal -> Open (if nobody bid)
    //   Owned -> Open (releaseDeed or invalidateName)
    function state(bytes32 _hash) public view returns (Mode) {
        Entry storage entry = _entries[_hash];

        if (!isAllowed(_hash, now)) {
            return Mode.NotYetAvailable;
        } else if (now < entry.registrationDate) {
            if (now < entry.registrationDate - revealPeriod) {
                return Mode.Auction;
            } else {
                return Mode.Reveal;
            }
        } else {
            if (entry.highestBid == 0) {
                return Mode.Open;
            } else {
                return Mode.Owned;
            }
        }
    }

    function entries(bytes32 _hash) public view returns (Mode, address, uint, uint, uint) {
        Entry storage h = _entries[_hash];
        return (state(_hash), h.deed, h.registrationDate, h.value, h.highestBid);
    }

    /**
     * @dev Determines if a name is available for registration yet
     *
     * Each name will be assigned a random date in which its auction
     * can be started, from 0 to 8 weeks
     *
     * @param _hash The hash to start an auction on
     * @param _timestamp The timestamp to query about
     */
    function isAllowed(bytes32 _hash, uint _timestamp) public view returns (bool allowed) {
        return _timestamp > getAllowedTime(_hash);
    }

    /**
     * @dev Returns available date for hash
     *
     * The available time from the `registryStarted` for a hash is proportional
     * to its numeric value.
     *
     * @param _hash The hash to start an auction on
     */
    function getAllowedTime(bytes32 _hash) public view returns (uint) {
        return registryStarted + ((launchLength * (uint(_hash) >> 128)) >> 128);
        // Right shift operator: a >> b == a / 2**b
    }

    /**
     * @dev Hash the values required for a secret bid
     *
     * @param hash The node corresponding to the desired namehash
     * @param value The bid amount
     * @param salt A random value to ensure secrecy of the bid
     * @return The hash of the bid values
     */
    function shaBid(bytes32 hash, address owner, uint value, bytes32 salt) public pure returns (bytes32) {
        return keccak256(hash, owner, value, salt);
    }

    function _tryEraseSingleNode(bytes32 label) internal {
        if (ens.owner(rootNode) == address(this)) {
            ens.setSubnodeOwner(rootNode, label, address(this));
            bytes32 node = keccak256(rootNode, label);
            ens.setResolver(node, 0);
            ens.setOwner(node, 0);
        }
    }

    function _eraseNodeHierarchy(uint idx, bytes32[] labels, bytes32 node) internal {
        // Take ownership of the node
        ens.setSubnodeOwner(node, labels[idx], address(this));
        node = keccak256(node, labels[idx]);

        // Recurse if there are more labels
        if (idx > 0) {
            _eraseNodeHierarchy(idx - 1, labels, node);
        }

        // Erase the resolver and owner records
        ens.setResolver(node, 0);
        ens.setOwner(node, 0);
    }

    /**
     * @dev Assign the owner in ENS, if we're still the registrar
     *
     * @param _hash hash to change owner
     * @param _newOwner new owner to transfer to
     */
    function trySetSubnodeOwner(bytes32 _hash, address _newOwner) internal {
        if (ens.owner(rootNode) == address(this))
            ens.setSubnodeOwner(rootNode, _hash, _newOwner);
    }

    /**
     * @dev Returns the maximum of two unsigned integers
     *
     * @param a A number to compare
     * @param b A number to compare
     * @return The maximum of two unsigned integers
     */
    function max(uint a, uint b) internal pure returns (uint) {
        if (a > b)
            return a;
        else
            return b;
    }

    /**
     * @dev Returns the minimum of two unsigned integers
     *
     * @param a A number to compare
     * @param b A number to compare
     * @return The minimum of two unsigned integers
     */
    function min(uint a, uint b) internal pure returns (uint) {
        if (a < b)
            return a;
        else
            return b;
    }

    /**
     * @dev Returns the length of a given string
     *
     * @param s The string to measure the length of
     * @return The length of the input string
     */
    function strlen(string s) internal pure returns (uint) {
        s; // Don't warn about unused variables
        // Starting here means the LSB will be the byte we care about
        uint ptr;
        uint end;
        assembly {
            ptr := add(s, 1)
            end := add(mload(s), ptr)
        }
        for (uint len = 0; ptr < end; len++) {
            uint8 b;
            assembly { b := and(mload(ptr), 0xFF) }
            if (b < 0x80) {
                ptr += 1;
            } else if (b < 0xE0) {
                ptr += 2;
            } else if (b < 0xF0) {
                ptr += 3;
            } else if (b < 0xF8) {
                ptr += 4;
            } else if (b < 0xFC) {
                ptr += 5;
            } else {
                ptr += 6;
            }
        }
        return len;
    }

}

// File: contracts/ENSNFT.sol

contract ENSNFT is ERC721Token {
    event Transfer(address indexed _from, address indexed _to, uint256 indexed _tokenId);
    Registrar registrar;
    constructor (string _name, string _symbol, address _registrar) public
        ERC721Token(_name, _symbol) {
        registrar = Registrar(_registrar);
    }
    function mint(bytes32 _hash) public {
        address deedAddress;
        (, deedAddress, , , ) = registrar.entries(_hash);
        Deed deed = Deed(deedAddress);
        require(deed.owner() == address(this));
        require(deed.previousOwner() == msg.sender);
        uint256 tokenId = uint256(_hash); // dont do math on this
        _mint(deed.previousOwner(), tokenId);
    }
    function burn(uint256 tokenId) {
        require(ownerOf(tokenId) == msg.sender);
        _burn(msg.sender, tokenId);
        registrar.transfer(bytes32(tokenId), msg.sender);
    }
}