// SPDX-License-Identifier: MIT License

pragma solidity ^0.5.0;

interface IERC165 {

    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

contract IERC721 is IERC165 {
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    function balanceOf(address owner) public view returns (uint256 balance);
    function ownerOf(uint256 tokenId) public view returns (address owner);

    function approve(address to, uint256 tokenId) public;
    function getApproved(uint256 tokenId) public view returns (address operator);

    function setApprovalForAll(address operator, bool _approved) public;
    function isApprovedForAll(address owner, address operator) public view returns (bool);

    function transferFrom(address from, address to, uint256 tokenId) public;
    function safeTransferFrom(address from, address to, uint256 tokenId) public;

    function safeTransferFrom(address from, address to, uint256 tokenId, bytes memory data) public;
}

contract IERC721Receiver {

    function onERC721Received(address operator, address from, uint256 tokenId, bytes memory data) public returns (bytes4);
}

library SafeMath {

    function mul(uint256 a, uint256 b) internal pure returns (uint256) {

        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b);

        return c;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a);
        uint256 c = a - b;

        return c;
    }

    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a);

        return c;
    }

    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b != 0);
        return a % b;
    }
}

library Address {

    function isContract(address account) internal view returns (bool) {
        uint256 size;
        assembly { size := extcodesize(account) }
        return size > 0;
    }
}

contract ERC165 is IERC165 {
    bytes4 private constant _InterfaceId_ERC165 = 0x01ffc9a7;

    mapping(bytes4 => bool) private _supportedInterfaces;

    constructor () internal {
        _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 ERC721 is ERC165, IERC721 {
    using SafeMath for uint256;
    using Address for address;

    bytes4 private constant _ERC721_RECEIVED = 0x150b7a02;

    // Mapping from token ID to owner
    mapping (uint256 => address) private _tokenOwner;

    // Mapping from token ID to approved address
    mapping (uint256 => address) private _tokenApprovals;

    // Mapping from owner to number of owned token
    mapping (address => uint256) private _ownedTokensCount;

    // Mapping from owner to operator approvals
    mapping (address => mapping (address => bool)) private _operatorApprovals;

    bytes4 private constant _InterfaceId_ERC721 = 0x80ac58cd;

    constructor () public {
        // register the supported interfaces to conform to ERC721 via ERC165
        _registerInterface(_InterfaceId_ERC721);
    }

    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 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) {
        require(_exists(tokenId));
        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(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 memory _data) public {
        transferFrom(from, to, tokenId);
        // solium-disable-next-line arg-overflow
        require(_checkOnERC721Received(from, to, tokenId, _data));
    }

    function _exists(uint256 tokenId) internal view returns (bool) {
        address owner = _tokenOwner[tokenId];
        return owner != address(0);
    }

    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 _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 _checkOnERC721Received(address from, address to, uint256 tokenId, bytes memory _data) internal returns (bool) {
        if (!to.isContract()) {
            return true;
        }

        bytes4 retval = IERC721Receiver(to).onERC721Received(msg.sender, from, tokenId, _data);
        return (retval == _ERC721_RECEIVED);
    }

    function _clearApproval(address owner, uint256 tokenId) private {
        require(ownerOf(tokenId) == owner);
        if (_tokenApprovals[tokenId] != address(0)) {
            _tokenApprovals[tokenId] = address(0);
        }
    }
}

contract IERC721Metadata is IERC721 {
    function name() external view returns (string memory);
    function symbol() external view returns (string memory);
    function tokenURI(uint256 tokenId) external view returns (string memory);
}

contract ERC721Metadata is ERC165, ERC721, IERC721Metadata {
    // Token name
    string private _name;

    // Token symbol
    string private _symbol;

    // Optional mapping for token URIs
    mapping(uint256 => string) private _tokenURIs;

    bytes4 private constant InterfaceId_ERC721Metadata = 0x5b5e139f;

    constructor (string memory name, string memory symbol) public {
        _name = name;
        _symbol = symbol;

        // register the supported interfaces to conform to ERC721 via ERC165
        _registerInterface(InterfaceId_ERC721Metadata);
    }

    function name() external view returns (string memory) {
        return _name;
    }

    function symbol() external view returns (string memory ) {
        return _symbol;
    }

    function tokenURI(uint256 tokenId) external view returns (string memory) {
        require(_exists(tokenId));
        return _tokenURIs[tokenId];
    }

    function _setTokenURI(uint256 tokenId, string memory uri) internal {
        require(_exists(tokenId));
        _tokenURIs[tokenId] = uri;
    }

    function _burn(address owner, uint256 tokenId) internal {
        super._burn(owner, tokenId);

        // Clear metadata (if any)
        if (bytes(_tokenURIs[tokenId]).length != 0) {
            delete _tokenURIs[tokenId];
        }
    }
}

contract IERC721Enumerable is IERC721 {
    function totalSupply() public view returns (uint256);
    function tokenOfOwnerByIndex(address owner, uint256 index) public view returns (uint256 tokenId);
    function tokenByIndex(uint256 index) public view returns (uint256);
}

contract ERC721Enumerable is ERC165, ERC721, IERC721Enumerable {
    // Mapping from owner to list of owned token IDs
    mapping(address => uint256[]) private _ownedTokens;

    // Mapping from token ID to index of the owner tokens list
    mapping(uint256 => uint256) private _ownedTokensIndex;

    // Array with all token ids, used for enumeration
    uint256[] private _allTokens;

    // Mapping from token id to position in the allTokens array
    mapping(uint256 => uint256) private _allTokensIndex;

    bytes4 private constant _InterfaceId_ERC721Enumerable = 0x780e9d63;

    constructor () public {
        // register the supported interface to conform to ERC721 via ERC165
        _registerInterface(_InterfaceId_ERC721Enumerable);
    }

    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 _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;
        // This also deletes the contents at the last position of the array
        _ownedTokens[from].length--;

        _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);

        // 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;
    }
}

contract ERC721Full is ERC721, ERC721Enumerable, ERC721Metadata {
    constructor (string memory name, string memory symbol) ERC721Metadata(name, symbol) public {}
}

library Strings {
  // via https://github.com/oraclize/ethereum-api/blob/master/oraclizeAPI_0.5.sol
  function strConcat(string memory _a, string memory _b, string memory _c, string memory _d, string memory _e) internal pure returns (string memory) {
      bytes memory _ba = bytes(_a);
      bytes memory _bb = bytes(_b);
      bytes memory _bc = bytes(_c);
      bytes memory _bd = bytes(_d);
      bytes memory _be = bytes(_e);
      string memory abcde = new string(_ba.length + _bb.length + _bc.length + _bd.length + _be.length);
      bytes memory babcde = bytes(abcde);
      uint k = 0;
      for (uint i = 0; i < _ba.length; i++) babcde[k++] = _ba[i];
      for (uint i = 0; i < _bb.length; i++) babcde[k++] = _bb[i];
      for (uint i = 0; i < _bc.length; i++) babcde[k++] = _bc[i];
      for (uint i = 0; i < _bd.length; i++) babcde[k++] = _bd[i];
      for (uint i = 0; i < _be.length; i++) babcde[k++] = _be[i];
      return string(babcde);
    }

    function strConcat(string memory _a, string memory _b, string memory _c, string memory _d) internal pure returns (string memory) {
        return strConcat(_a, _b, _c, _d, "");
    }

    function strConcat(string memory _a, string memory _b, string memory _c) internal pure returns (string memory) {
        return strConcat(_a, _b, _c, "", "");
    }

    function strConcat(string memory _a, string memory _b) internal pure returns (string memory) {
        return strConcat(_a, _b, "", "", "");
    }

    function uint2str(uint _i) internal pure returns (string memory _uintAsString) {
        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(uint8(48 + _i % 10));
            _i /= 10;
        }
        return string(bstr);
    }
}

contract OwnableDelegateProxy { }

contract ProxyRegistry {
    mapping(address => OwnableDelegateProxy) public proxies;
}

contract Ownable {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    constructor () internal {
        _owner = msg.sender;
        emit OwnershipTransferred(address(0), _owner);
    }

    function owner() public view returns (address) {
        return _owner;
    }

    modifier onlyOwner() {
        require(isOwner());
        _;
    }

    function isOwner() public view returns (bool) {
        return msg.sender == _owner;
    }

    function renounceOwnership() public onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    function transferOwnership(address newOwner) public onlyOwner {
        _transferOwnership(newOwner);
    }

    function _transferOwnership(address newOwner) internal {
        require(newOwner != address(0));
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

contract TradeableERC721Token is ERC721Full, Ownable {
  using Strings for string;

  address proxyRegistryAddress;
  uint256 private _currentTokenId = 0;

  constructor(string memory _name, string memory _symbol, address _proxyRegistryAddress) ERC721Full(_name, _symbol) public {
    proxyRegistryAddress = _proxyRegistryAddress;
  }

  function mintTo(address _to, uint256 _numOfTokens) public onlyOwner {
    for (uint256 i = 0; i < _numOfTokens; i++) {
        uint256 newTokenId = _getNextTokenId();
        _mint(_to, newTokenId);
        _incrementTokenId();
    }
  }

  function _getNextTokenId() private view returns (uint256) {
    return _currentTokenId.add(1);
  }

  function _incrementTokenId() private  {
    _currentTokenId++;
  }

  function baseTokenURI() public view returns (string memory) {
    return "https://market.k-base.art/api/";
  }

  function tokenURI(uint256 _tokenId) external view returns (string memory) {
    return Strings.strConcat(
        baseTokenURI(),
        Strings.uint2str(_tokenId)
    );
  }

  function isApprovedForAll(
    address owner,
    address operator
  )
    public
    view
    returns (bool)
  {
    // Whitelist OpenSea proxy contract for easy trading.
    ProxyRegistry proxyRegistry = ProxyRegistry(proxyRegistryAddress);
    if (address(proxyRegistry.proxies(owner)) == operator) {
        return true;
    }

    return super.isApprovedForAll(owner, operator);
  }
}

contract KB is TradeableERC721Token {
  constructor(address _proxyRegistryAddress) TradeableERC721Token("K Base", "KB", _proxyRegistryAddress) public {  }

  function baseTokenURI() public view returns (string memory) {
    return "#";
  }
}