contract ERC1155 is IERC165 {
  using SafeMath for uint256;
  using Address for address;


  /***********************************|
  |        Variables and Events       |
  |__________________________________*/

  // onReceive function signatures
  bytes4 constant internal ERC1155_RECEIVED_VALUE = 0xf23a6e61;
  bytes4 constant internal ERC1155_BATCH_RECEIVED_VALUE = 0xbc197c81;

  // Objects balances
  mapping (address => mapping(uint256 => uint256)) internal balances;

  // Operator Functions
  mapping (address => mapping(address => bool)) internal operators;

  // Events
  event TransferSingle(address indexed _operator, address indexed _from, address indexed _to, uint256 _id, uint256 _amount);
  event TransferBatch(address indexed _operator, address indexed _from, address indexed _to, uint256[] _ids, uint256[] _amounts);
  event ApprovalForAll(address indexed _owner, address indexed _operator, bool _approved);
  event URI(string _uri, uint256 indexed _id);


  /***********************************|
  |     Public Transfer Functions     |
  |__________________________________*/

  /**
   * @notice Transfers amount amount of an _id from the _from address to the _to address specified
   * @param _from    Source address
   * @param _to      Target address
   * @param _id      ID of the token type
   * @param _amount  Transfered amount
   * @param _data    Additional data with no specified format, sent in call to `_to`
   */
  function safeTransferFrom(address _from, address _to, uint256 _id, uint256 _amount, bytes memory _data)
    public
  {
    require((msg.sender == _from) || operators[_from][msg.sender], "ERC1155#safeTransferFrom: INVALID_OPERATOR");
    require(_to != address(0),"ERC1155#safeTransferFrom: INVALID_RECIPIENT");
    // require(_amount >= balances[_from][_id]) is not necessary since checked with safemath operations

    _safeTransferFrom(_from, _to, _id, _amount);
    _callonERC1155Received(_from, _to, _id, _amount, _data);
  }

  /**
   * @notice Send multiple types of Tokens from the _from address to the _to address (with safety call)
   * @param _from     Source addresses
   * @param _to       Target addresses
   * @param _ids      IDs of each token type
   * @param _amounts  Transfer amounts per token type
   * @param _data     Additional data with no specified format, sent in call to `_to`
   */
  function safeBatchTransferFrom(address _from, address _to, uint256[] memory _ids, uint256[] memory _amounts, bytes memory _data)
    public
  {
    // Requirements
    require((msg.sender == _from) || operators[_from][msg.sender], "ERC1155#safeBatchTransferFrom: INVALID_OPERATOR");
    require(_to != address(0), "ERC1155#safeBatchTransferFrom: INVALID_RECIPIENT");

    _safeBatchTransferFrom(_from, _to, _ids, _amounts);
    _callonERC1155BatchReceived(_from, _to, _ids, _amounts, _data);
  }


  /***********************************|
  |    Internal Transfer Functions    |
  |__________________________________*/

  /**
   * @notice Transfers amount amount of an _id from the _from address to the _to address specified
   * @param _from    Source address
   * @param _to      Target address
   * @param _id      ID of the token type
   * @param _amount  Transfered amount
   */
  function _safeTransferFrom(address _from, address _to, uint256 _id, uint256 _amount)
    internal
  {
    // Update balances
    balances[_from][_id] = balances[_from][_id].sub(_amount); // Subtract amount
    balances[_to][_id] = balances[_to][_id].add(_amount);     // Add amount

    // Emit event
    emit TransferSingle(msg.sender, _from, _to, _id, _amount);
  }

  /**
   * @notice Verifies if receiver is contract and if so, calls (_to).onERC1155Received(...)
   */
  function _callonERC1155Received(address _from, address _to, uint256 _id, uint256 _amount, bytes memory _data)
    internal
  {
    // Check if recipient is contract
    if (_to.isContract()) {
      bytes4 retval = IERC1155TokenReceiver(_to).onERC1155Received(msg.sender, _from, _id, _amount, _data);
      require(retval == ERC1155_RECEIVED_VALUE, "ERC1155#_callonERC1155Received: INVALID_ON_RECEIVE_MESSAGE");
    }
  }

  /**
   * @notice Send multiple types of Tokens from the _from address to the _to address (with safety call)
   * @param _from     Source addresses
   * @param _to       Target addresses
   * @param _ids      IDs of each token type
   * @param _amounts  Transfer amounts per token type
   */
  function _safeBatchTransferFrom(address _from, address _to, uint256[] memory _ids, uint256[] memory _amounts)
    internal
  {
    require(_ids.length == _amounts.length, "ERC1155#_safeBatchTransferFrom: INVALID_ARRAYS_LENGTH");

    // Number of transfer to execute
    uint256 nTransfer = _ids.length;

    // Executing all transfers
    for (uint256 i = 0; i < nTransfer; i++) {
      // Update storage balance of previous bin
      balances[_from][_ids[i]] = balances[_from][_ids[i]].sub(_amounts[i]);
      balances[_to][_ids[i]] = balances[_to][_ids[i]].add(_amounts[i]);
    }

    // Emit event
    emit TransferBatch(msg.sender, _from, _to, _ids, _amounts);
  }

  /**
   * @notice Verifies if receiver is contract and if so, calls (_to).onERC1155BatchReceived(...)
   */
  function _callonERC1155BatchReceived(address _from, address _to, uint256[] memory _ids, uint256[] memory _amounts, bytes memory _data)
    internal
  {
    // Pass data if recipient is contract
    if (_to.isContract()) {
      bytes4 retval = IERC1155TokenReceiver(_to).onERC1155BatchReceived(msg.sender, _from, _ids, _amounts, _data);
      require(retval == ERC1155_BATCH_RECEIVED_VALUE, "ERC1155#_callonERC1155BatchReceived: INVALID_ON_RECEIVE_MESSAGE");
    }
  }


  /***********************************|
  |         Operator Functions        |
  |__________________________________*/

  /**
   * @notice Enable or disable approval for a third party ("operator") to manage all of caller's tokens
   * @param _operator  Address to add to the set of authorized operators
   * @param _approved  True if the operator is approved, false to revoke approval
   */
  function setApprovalForAll(address _operator, bool _approved)
    external
  {
    // Update operator status
    operators[msg.sender][_operator] = _approved;
    emit ApprovalForAll(msg.sender, _operator, _approved);
  }

  /**
   * @notice Queries the approval status of an operator for a given owner
   * @param _owner     The owner of the Tokens
   * @param _operator  Address of authorized operator
   * @return True if the operator is approved, false if not
   */
  function isApprovedForAll(address _owner, address _operator)
    public view returns (bool isOperator)
  {
    return operators[_owner][_operator];
  }


  /***********************************|
  |         Balance Functions         |
  |__________________________________*/

  /**
   * @notice Get the balance of an account's Tokens
   * @param _owner  The address of the token holder
   * @param _id     ID of the Token
   * @return The _owner's balance of the Token type requested
   */
  function balanceOf(address _owner, uint256 _id)
    public view returns (uint256)
  {
    return balances[_owner][_id];
  }

  /**
   * @notice Get the balance of multiple account/token pairs
   * @param _owners The addresses of the token holders
   * @param _ids    ID of the Tokens
   * @return        The _owner's balance of the Token types requested (i.e. balance for each (owner, id) pair)
   */
  function balanceOfBatch(address[] memory _owners, uint256[] memory _ids)
    public view returns (uint256[] memory)
  {
    require(_owners.length == _ids.length, "ERC1155#balanceOfBatch: INVALID_ARRAY_LENGTH");

    // Variables
    uint256[] memory batchBalances = new uint256[](_owners.length);

    // Iterate over each owner and token ID
    for (uint256 i = 0; i < _owners.length; i++) {
      batchBalances[i] = balances[_owners[i]][_ids[i]];
    }

    return batchBalances;
  }


  /***********************************|
  |          ERC165 Functions         |
  |__________________________________*/

  /**
   * INTERFACE_SIGNATURE_ERC165 = bytes4(keccak256("supportsInterface(bytes4)"));
   */
  bytes4 constant private INTERFACE_SIGNATURE_ERC165 = 0x01ffc9a7;

  /**
   * INTERFACE_SIGNATURE_ERC1155 =
   * bytes4(keccak256("safeTransferFrom(address,address,uint256,uint256,bytes)")) ^
   * bytes4(keccak256("safeBatchTransferFrom(address,address,uint256[],uint256[],bytes)")) ^
   * bytes4(keccak256("balanceOf(address,uint256)")) ^
   * bytes4(keccak256("balanceOfBatch(address[],uint256[])")) ^
   * bytes4(keccak256("setApprovalForAll(address,bool)")) ^
   * bytes4(keccak256("isApprovedForAll(address,address)"));
   */
  bytes4 constant private INTERFACE_SIGNATURE_ERC1155 = 0xd9b67a26;

  /**
   * @notice Query if a contract implements an interface
   * @param _interfaceID  The interface identifier, as specified in ERC-165
   * @return `true` if the contract implements `_interfaceID` and
   */
  function supportsInterface(bytes4 _interfaceID) external view returns (bool) {
    if (_interfaceID == INTERFACE_SIGNATURE_ERC165 ||
        _interfaceID == INTERFACE_SIGNATURE_ERC1155) {
      return true;
    }
    return false;
  }

}
/**
 * @dev Implementation of Multi-Token Standard contract
 */
function safeBatchTransferFrom(address _from, address _to, uint256[] memory _ids, uint256[] memory _amounts, bytes memory _data)
  public
{
  // Requirements
  require((msg.sender == _from) || operators[_from][msg.sender], "ERC1155#safeBatchTransferFrom: INVALID_OPERATOR");
  require(_to != address(0), "ERC1155#safeBatchTransferFrom: INVALID_RECIPIENT");

  _safeBatchTransferFrom(_from, _to, _ids, _amounts);
  _callonERC1155BatchReceived(_from, _to, _ids, _amounts, _data);
}

/**
 * @notice Send multiple types of Tokens from the _from address to the _to address (with safety call)
 * @param _from     Source addresses
 * @param _to       Target addresses
 * @param _ids      IDs of each token type
 * @param _amounts  Transfer amounts per token type
 * @param _data     Additional data with no specified format, sent in call to `_to`
 */