pragma solidity ^0.4.24;



/**
 * @title ERC165
 * @dev https://github.com/ethereum/EIPs/blob/master/EIPS/eip-165.md
 */
interface ERC165 {

  function supportsInterface(bytes4 _interfaceId)
    external
    view
    returns (bool);
}



contract SupportsInterfaceWithLookup is ERC165 {
  bytes4 public constant InterfaceId_ERC165 = 0x01ffc9a7;

  mapping(bytes4 => bool) internal supportedInterfaces;

  constructor()
    public
  {
    _registerInterface(InterfaceId_ERC165);
  }

  function supportsInterface(bytes4 _interfaceId)
    external
    view
    returns (bool)
  {
    return supportedInterfaces[_interfaceId];
  }

  function _registerInterface(bytes4 _interfaceId)
    internal
  {
    require(_interfaceId != 0xffffffff);
    supportedInterfaces[_interfaceId] = true;
  }
}


contract ERC721Basic is ERC165 {

  bytes4 internal constant InterfaceId_ERC721 = 0x80ac58cd;

  bytes4 internal constant InterfaceId_ERC721Exists = 0x4f558e79;

  bytes4 internal constant InterfaceId_ERC721Enumerable = 0x780e9d63;

  bytes4 internal constant InterfaceId_ERC721Metadata = 0x5b5e139f;

  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;
}



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);
}


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);
}


contract ERC721 is ERC721Basic, ERC721Enumerable, ERC721Metadata {
}




contract ERC721Receiver {

  bytes4 internal constant ERC721_RECEIVED = 0x150b7a02;

  function onERC721Received(
    address _operator,
    address _from,
    uint256 _tokenId,
    bytes _data
  )
    public
    returns(bytes4);
}



library SafeMath {

  function mul(uint256 a, uint256 b) internal pure returns (uint256 c) {

    if (a == 0) {
      return 0;
    }

    c = a * b;
    assert(c / a == b);
    return c;
  }

  function div(uint256 a, uint256 b) internal pure returns (uint256) {

    return a / b;
  }

  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    assert(b <= a);
    return a - b;
  }

  function add(uint256 a, uint256 b) internal pure returns (uint256 c) {
    c = a + b;
    assert(c >= a);
    return c;
  }
}


library AddressUtils {


  function isContract(address addr) internal view returns (bool) {
    uint256 size;
    assembly { size := extcodesize(addr) }
    return size > 0;
  }

}


contract ERC721BasicToken is SupportsInterfaceWithLookup, ERC721Basic {

  using SafeMath for uint256;
  using AddressUtils for address;

  bytes4 private constant ERC721_RECEIVED = 0x150b7a02;

  mapping (uint256 => address) internal tokenOwner;
  mapping (uint256 => address) internal tokenApprovals;
  mapping (address => uint256) internal ownedTokensCount;
  mapping (address => mapping (address => bool)) internal operatorApprovals;

  constructor()
    public
  {
    _registerInterface(InterfaceId_ERC721);
    _registerInterface(InterfaceId_ERC721Exists);
  }

  function balanceOf(address _owner) public view returns (uint256) {
    require(_owner != address(0));
    return ownedTokensCount[_owner];
  }

  function ownerOf(uint256 _tokenId) public view returns (address) {
    address owner = tokenOwner[_tokenId];
    require(owner != address(0));
    return owner;
  }

  function exists(uint256 _tokenId) public view returns (bool) {
    address owner = tokenOwner[_tokenId];
    return owner != address(0);
  }

  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);
  }

  function getApproved(uint256 _tokenId) public view returns (address) {
    return tokenApprovals[_tokenId];
  }

  function setApprovalForAll(address _to, bool _approved) public {
    require(_to != msg.sender);
    operatorApprovals[msg.sender][_to] = _approved;
    emit ApprovalForAll(msg.sender, _to, _approved);
  }

  function isApprovedForAll(
    address _owner,
    address _operator
  )
    public
    view
    returns (bool)
  {
    return operatorApprovals[_owner][_operator];
  }

  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);
  }

  function safeTransferFrom(
    address _from,
    address _to,
    uint256 _tokenId
  )
    public
  {
    // solium-disable-next-line arg-overflow
    safeTransferFrom(_from, _to, _tokenId, "");
  }

  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));
  }

  function isApprovedOrOwner(
    address _spender,
    uint256 _tokenId
  )
    internal
    view
    returns (bool)
  {
    address owner = ownerOf(_tokenId);
    return (
      _spender == owner ||
      getApproved(_tokenId) == _spender ||
      isApprovedForAll(owner, _spender)
    );
  }


  function _mint(address _to, uint256 _tokenId) internal {
    require(_to != address(0));
    addTokenTo(_to, _tokenId);
    emit Transfer(address(0), _to, _tokenId);
  }

  function _burn(address _owner, uint256 _tokenId) internal {
    clearApproval(_owner, _tokenId);
    removeTokenFrom(_owner, _tokenId);
    emit Transfer(_owner, address(0), _tokenId);
  }

  function clearApproval(address _owner, uint256 _tokenId) internal {
    require(ownerOf(_tokenId) == _owner);
    if (tokenApprovals[_tokenId] != address(0)) {
      tokenApprovals[_tokenId] = address(0);
    }
  }

  function addTokenTo(address _to, uint256 _tokenId) internal {
    require(tokenOwner[_tokenId] == address(0));
    tokenOwner[_tokenId] = _to;
    ownedTokensCount[_to] = ownedTokensCount[_to].add(1);
  }

  function removeTokenFrom(address _from, uint256 _tokenId) internal {
    require(ownerOf(_tokenId) == _from);
    ownedTokensCount[_from] = ownedTokensCount[_from].sub(1);
    tokenOwner[_tokenId] = address(0);
  }

  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);
  }
}







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;

  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);
  }

  function name() external view returns (string) {
    return name_;
  }

  function symbol() external view returns (string) {
    return symbol_;
  }

  function tokenURI(uint256 _tokenId) public view returns (string) {
    require(exists(_tokenId));
    return tokenURIs[_tokenId];
  }

  function tokenOfOwnerByIndex(
    address _owner,
    uint256 _index
  )
    public
    view
    returns (uint256)
  {
    require(_index < balanceOf(_owner));
    return ownedTokens[_owner][_index];
  }

  function totalSupply() public view returns (uint256) {
    return allTokens.length;
  }

  function tokenByIndex(uint256 _index) public view returns (uint256) {
    require(_index < totalSupply());
    return allTokens[_index];
  }


  function _setTokenURI(uint256 _tokenId, string _uri) internal {
    require(exists(_tokenId));
    tokenURIs[_tokenId] = _uri;
  }


  function addTokenTo(address _to, uint256 _tokenId) internal {
    super.addTokenTo(_to, _tokenId);
    uint256 length = ownedTokens[_to].length;
    ownedTokens[_to].push(_tokenId);
    ownedTokensIndex[_tokenId] = length;
  }


  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].length--; // This also deletes the contents at the last position of the array

    ownedTokensIndex[_tokenId] = 0;
    ownedTokensIndex[lastToken] = tokenIndex;
  }


  function _mint(address _to, uint256 _tokenId) internal {
    super._mint(_to, _tokenId);

    allTokensIndex[_tokenId] = allTokens.length;
    allTokens.push(_tokenId);
  }


  function _burn(address _owner, uint256 _tokenId) internal {
    super._burn(_owner, _tokenId);

    if (bytes(tokenURIs[_tokenId]).length != 0) {
      delete tokenURIs[_tokenId];
    }

    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;
  }

}


contract lettertoken205 is ERC721Token {

  constructor() public ERC721Token("lettertoken205","lettertoken205") { }

  struct Token{
    uint8 data1;
    uint8 data2;
    uint64 data3;
    uint64 data4;
    uint64 startBlock;
  }

  Token[] private tokens;

  function create(uint8 data1, uint8 data2,uint64 data3, uint64 data4) public returns (uint256 _tokenId) {

    string memory tokenUri = createTokenUri(data1,data2,data3,data4);

    Token memory _newToken = Token({
        data1: data1,
        data2: data2,
        data3: data3,
        data4: data4,
        startBlock: uint64(block.number)
    });
    _tokenId = tokens.push(_newToken) - 1;
    _mint(msg.sender,_tokenId);
    _setTokenURI(_tokenId, tokenUri);
    tokenUri=strConcat(tokenUri,"-");
    string memory tokenIdb=uint2str(_tokenId);
    tokenUri=strConcat(tokenUri, tokenIdb);
    emit Create(_tokenId,msg.sender,data1,data2,data3,data4,_newToken.startBlock,tokenUri);
    return _tokenId;
  }

  event Create(
    uint _id,
    address indexed _owner,
    uint8 _data1,
    uint8 _data2,
    uint64 _data3,
    uint64 _data4,
    uint64 _startBlock,
    string _uri
  );

  function get(uint256 _id) public view returns (address owner,uint8 data1,uint8 data2,uint64 data3,uint64 data4,uint64 startBlock) {
    return (
      tokenOwner[_id],
      tokens[_id].data1,
      tokens[_id].data2,
      tokens[_id].data3,
      tokens[_id].data4,
      tokens[_id].startBlock
    );
  }

  function tokensOfOwner(address _owner) public view returns(uint256[]) {
    return ownedTokens[_owner];
  }

  function createTokenUri(uint8 data1,uint8 data2,uint64 data3,uint64 data4) internal pure returns (string){
    string memory uri = "https://www.millionetherwords.com/exchange/displaytoken/?s=";
    uri = appendUint8ToString(uri,data1);
    uri = strConcat(uri,"-");
    uri = appendUint8ToString(uri,data2);
    uri = strConcat(uri,"-");
    string memory data3b=uint2str(data3);
    uri = strConcat(uri,data3b);
    uri = strConcat(uri,"-");
    string memory data4b=uint2str(data4);
    uri = strConcat(uri,data4b);
   
    uri = strConcat(uri,".png");
    return uri;
  }

function uint2str(uint i) internal pure returns (string){
    if (i == 0) return "0";
    uint j = i;
    uint length;
    while (j != 0){
        length++;
        j /= 10;
    }
    bytes memory bstr = new bytes(length);
    uint k = length - 1;
    while (i != 0){
        bstr[k--] = byte(48 + i % 10);
        i /= 10;
    }
    return string(bstr);
}

  function appendUint8ToString(string inStr, uint8 v) internal pure returns (string str) {
        uint maxlength = 100;
        bytes memory reversed = new bytes(maxlength);
        uint i = 0;
        while (v != 0) {
            uint remainder = v % 10;
            v = v / 10;
            reversed[i++] = byte(48 + remainder);
        }
        bytes memory inStrb = bytes(inStr);
        bytes memory s = new bytes(inStrb.length + i);
        uint j;
        for (j = 0; j < inStrb.length; j++) {
            s[j] = inStrb[j];
        }
        for (j = 0; j < i; j++) {
            s[j + inStrb.length] = reversed[i - 1 - j];
        }
        str = string(s);
    }

    function strConcat(string _a, string _b) internal pure returns (string) {
        bytes memory _ba = bytes(_a);
        bytes memory _bb = bytes(_b);
        string memory ab = new string(_ba.length + _bb.length);
        bytes memory bab = bytes(ab);
        uint k = 0;
        for (uint i = 0; i < _ba.length; i++) bab[k++] = _ba[i];
        for (i = 0; i < _bb.length; i++) bab[k++] = _bb[i];
        return string(bab);
    }

}