pragma solidity ^0.4.18;

/**
 * @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 OwnershipTransferred(address indexed previousOwner, address indexed newOwner);


  /**
   * @dev The Ownable constructor sets the original `owner` of the contract to the sender
   * account.
   */
  function Ownable() 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 transfer control of the contract to a newOwner.
   * @param newOwner The address to transfer ownership to.
   */
  function transferOwnership(address newOwner) public onlyOwner {
    require(newOwner != address(0));
    OwnershipTransferred(owner, newOwner);
    owner = newOwner;
  }

}

/**
 * @title Pausable
 * @dev Base contract which allows children to implement an emergency stop mechanism.
 */
contract Pausable is Ownable {
  event Pause();
  event Unpause();

  bool public paused = false;


  /**
   * @dev Modifier to make a function callable only when the contract is not paused.
   */
  modifier whenNotPaused() {
    require(!paused);
    _;
  }

  /**
   * @dev Modifier to make a function callable only when the contract is paused.
   */
  modifier whenPaused() {
    require(paused);
    _;
  }

  /**
   * @dev called by the owner to pause, triggers stopped state
   */
  function pause() onlyOwner whenNotPaused public {
    paused = true;
    Pause();
  }

  /**
   * @dev called by the owner to unpause, returns to normal state
   */
  function unpause() onlyOwner whenPaused public {
    paused = false;
    Unpause();
  }
}

/**
 * @title Claimable
 * @dev Extension for the Ownable contract, where the ownership needs to be claimed.
 * This allows the new owner to accept the transfer.
 */
contract Claimable is Ownable {
  address public pendingOwner;

  /**
   * @dev Modifier throws if called by any account other than the pendingOwner.
   */
  modifier onlyPendingOwner() {
    require(msg.sender == pendingOwner);
    _;
  }

  /**
   * @dev Allows the current owner to set the pendingOwner address.
   * @param newOwner The address to transfer ownership to.
   */
  function transferOwnership(address newOwner) onlyOwner public {
    pendingOwner = newOwner;
  }

  /**
   * @dev Allows the pendingOwner address to finalize the transfer.
   */
  function claimOwnership() onlyPendingOwner public {
    OwnershipTransferred(owner, pendingOwner);
    owner = pendingOwner;
    pendingOwner = address(0);
  }
}

/**
 * @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) {
    if (a == 0) {
      return 0;
    }
    uint256 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 c;
  }

  /**
  * @dev Substracts 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) {
    uint256 c = a + b;
    assert(c >= a);
    return c;
  }
}

/**
 * @title ERC721 interface
 * @dev see https://github.com/ethereum/eips/issues/721
 */
contract ERC721 {
  event Transfer(address indexed _from, address indexed _to, uint256 _tokenId);
  event Approval(address indexed _owner, address indexed _approved, uint256 _tokenId);

  function balanceOf(address _owner) public view returns (uint256 _balance);
  function ownerOf(uint256 _tokenId) public view returns (address _owner);
  function transfer(address _to, uint256 _tokenId) public;
  function approve(address _to, uint256 _tokenId) public;
  function takeOwnership(uint256 _tokenId) public;
}

/**
 * @title ERC721Token
 * Generic implementation for the required functionality of the ERC721 standard
 */
contract ERC721Token is ERC721 {
  using SafeMath for uint256;

  // Total amount of tokens
  uint256 private totalTokens;

  // 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 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;

  /**
  * @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 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 totalTokens;
  }

  /**
  * @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) {
    return ownedTokens[_owner].length;
  }

  /**
  * @dev Gets the list of tokens owned by a given address
  * @param _owner address to query the tokens of
  * @return uint256[] representing the list of tokens owned by the passed address
  */
  function tokensOf(address _owner) public view returns (uint256[]) {
    return ownedTokens[_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 Gets the approved address to take ownership of a given token ID
   * @param _tokenId uint256 ID of the token to query the approval of
   * @return address currently approved to take ownership of the given token ID
   */
  function approvedFor(uint256 _tokenId) public view returns (address) {
    return tokenApprovals[_tokenId];
  }

  /**
  * @dev Transfers the ownership of a given token ID to another address
  * @param _to address to receive the ownership of the given token ID
  * @param _tokenId uint256 ID of the token to be transferred
  */
  function transfer(address _to, uint256 _tokenId) public onlyOwnerOf(_tokenId) {
    clearApprovalAndTransfer(msg.sender, _to, _tokenId);
  }

  /**
  * @dev Approves another address to claim for the ownership of the given token ID
  * @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 onlyOwnerOf(_tokenId) {
    address owner = ownerOf(_tokenId);
    require(_to != owner);
    if (approvedFor(_tokenId) != 0 || _to != 0) {
      tokenApprovals[_tokenId] = _to;
      Approval(owner, _to, _tokenId);
    }
  }

  /**
  * @dev Claims the ownership of a given token ID
  * @param _tokenId uint256 ID of the token being claimed by the msg.sender
  */
  function takeOwnership(uint256 _tokenId) public {
    require(isApprovedFor(msg.sender, _tokenId));
    clearApprovalAndTransfer(ownerOf(_tokenId), msg.sender, _tokenId);
  }

  /**
  * @dev Mint token function
  * @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));
    addToken(_to, _tokenId);
    Transfer(0x0, _to, _tokenId);
  }

  /**
  * @dev Burns a specific token
  * @param _tokenId uint256 ID of the token being burned by the msg.sender
  */
  function _burn(uint256 _tokenId) onlyOwnerOf(_tokenId) internal {
    if (approvedFor(_tokenId) != 0) {
      clearApproval(msg.sender, _tokenId);
    }
    removeToken(msg.sender, _tokenId);
    Transfer(msg.sender, 0x0, _tokenId);
  }

  /**
   * @dev Tells whether the msg.sender is approved for the given token ID or not
   * This function is not private so it can be extended in further implementations like the operatable ERC721
   * @param _owner address of the owner to query the approval of
   * @param _tokenId uint256 ID of the token to query the approval of
   * @return bool whether the msg.sender is approved for the given token ID or not
   */
  function isApprovedFor(address _owner, uint256 _tokenId) internal view returns (bool) {
    return approvedFor(_tokenId) == _owner;
  }

  /**
  * @dev Internal function to clear current approval and transfer the ownership of a given token ID
  * @param _from address which you want to send tokens from
  * @param _to address which you want to transfer the token to
  * @param _tokenId uint256 ID of the token to be transferred
  */
  function clearApprovalAndTransfer(address _from, address _to, uint256 _tokenId) internal {
    require(_to != address(0));
    require(_to != ownerOf(_tokenId));
    require(ownerOf(_tokenId) == _from);

    clearApproval(_from, _tokenId);
    removeToken(_from, _tokenId);
    addToken(_to, _tokenId);
    Transfer(_from, _to, _tokenId);
  }

  /**
  * @dev Internal function to clear current approval of a given token ID
  * @param _tokenId uint256 ID of the token to be transferred
  */
  function clearApproval(address _owner, uint256 _tokenId) private {
    require(ownerOf(_tokenId) == _owner);
    tokenApprovals[_tokenId] = 0;
    Approval(_owner, 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 addToken(address _to, uint256 _tokenId) private {
    require(tokenOwner[_tokenId] == address(0));
    tokenOwner[_tokenId] = _to;
    uint256 length = balanceOf(_to);
    ownedTokens[_to].push(_tokenId);
    ownedTokensIndex[_tokenId] = length;
    totalTokens = totalTokens.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 removeToken(address _from, uint256 _tokenId) private {
    require(ownerOf(_tokenId) == _from);

    uint256 tokenIndex = ownedTokensIndex[_tokenId];
    uint256 lastTokenIndex = balanceOf(_from).sub(1);
    uint256 lastToken = ownedTokens[_from][lastTokenIndex];

    tokenOwner[_tokenId] = 0;
    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;
    totalTokens = totalTokens.sub(1);
  }
}

/**
 * @title AccessMint
 * @dev Adds grant/revoke functions to the contract.
 */
contract AccessMint is Claimable {

  // Access for minting new tokens.
  mapping(address => bool) private mintAccess;

  // Event that is fired when minted.
  event Mint(
    address indexed _to,
    uint256 indexed _tokenId
  );

  // Modifier for accessibility to define new hero types.
  modifier onlyAccessMint {
    require(msg.sender == owner || mintAccess[msg.sender] == true);
    _;
  }

  // @dev Grant acess to mint heroes.
  function grantAccessMint(address _address)
    onlyOwner
    public
  {
    mintAccess[_address] = true;
  }

  // @dev Revoke acess to mint heroes.
  function revokeAccessMint(address _address)
    onlyOwner
    public
  {
    mintAccess[_address] = false;
  }

}

/**
 * @title The swap contract (Card => reward)
 * @dev With this contract, a CryptoSagaCard holder can swap his/her CryptoSagaCard for reward.
 *  This contract is intended to be inherited by CryptoSagaCore later.
 */
contract CryptoSagaCardSwap is Ownable {

  // Card contract.
  address internal cardAddess;

  // Modifier for accessibility to define new hero types.
  modifier onlyCard {
    require(msg.sender == cardAddess);
    _;
  }
  
  // @dev Set the address of the contract that represents ERC721 Card.
  function setCardContract(address _contractAddress)
    public
    onlyOwner
  {
    cardAddess = _contractAddress;
  }

  // @dev Convert card into reward.
  //  This should be implemented by CryptoSagaCore later.
  function swapCardForReward(address _by, uint8 _rank)
    onlyCard
    public 
    returns (uint256)
  {
    return 0;
  }

}

/**
 * @title CryptoSaga Card
 * @dev ERC721 Token that repesents CryptoSaga's cards.
 *  Buy consuming a card, players of CryptoSaga can get a heroe.
 */
contract CryptoSagaCard is ERC721Token, Claimable, AccessMint {

  string public constant name = "CryptoSaga Card";
  string public constant symbol = "CARD";

  // Rank of the token.
  mapping(uint256 => uint8) public tokenIdToRank;

  // The number of tokens ever minted.
  uint256 public numberOfTokenId;

  // The converter contract.
  CryptoSagaCardSwap private swapContract;

  // Event that should be fired when card is converted.
  event CardSwap(address indexed _by, uint256 _tokenId, uint256 _rewardId);

  // @dev Set the address of the contract that represents CryptoSaga Cards.
  function setCryptoSagaCardSwapContract(address _contractAddress)
    public
    onlyOwner
  {
    swapContract = CryptoSagaCardSwap(_contractAddress);
  }

  function rankOf(uint256 _tokenId) 
    public view
    returns (uint8)
  {
    return tokenIdToRank[_tokenId];
  }

  // @dev Mint a new card.
  function mint(address _beneficiary, uint256 _amount, uint8 _rank)
    onlyAccessMint
    public
  {
    for (uint256 i = 0; i < _amount; i++) {
      _mint(_beneficiary, numberOfTokenId);
      tokenIdToRank[numberOfTokenId] = _rank;
      numberOfTokenId ++;
    }
  }

  // @dev Swap this card for reward.
  //  The card will be burnt.
  function swap(uint256 _tokenId)
    onlyOwnerOf(_tokenId)
    public
    returns (uint256)
  {
    require(address(swapContract) != address(0));

    var _rank = tokenIdToRank[_tokenId];
    var _rewardId = swapContract.swapCardForReward(this, _rank);
    CardSwap(ownerOf(_tokenId), _tokenId, _rewardId);
    _burn(_tokenId);
    return _rewardId;
  }

}