pragma solidity ^0.4.18;

library SafeMath {
  function mul(uint a, uint b) internal pure returns (uint) {
    uint c = a * b;
    assert(a == 0 || c / a == b);
    return c;
  }

  function div(uint a, uint b) internal pure returns (uint) {
    // assert(b > 0); // Solidity automatically throws when dividing by 0
    uint c = a / b;
    // assert(a == b * c + a % b); // There is no case in which this doesn't hold
    return c;
  }

  function sub(uint a, uint b) internal pure returns (uint) {
    assert(b <= a);
    return a - b;
  }

  function add(uint a, uint b) internal pure returns (uint) {
    uint c = a + b;
    assert(c >= a);
    return c;
  }

  function max64(uint64 a, uint64 b) internal pure returns (uint64) {
    return a >= b ? a : b;
  }

  function min64(uint64 a, uint64 b) internal pure returns (uint64) {
    return a < b ? a : b;
  }

  function max256(uint256 a, uint256 b) internal pure returns (uint256) {
    return a >= b ? a : b;
  }

  function min256(uint256 a, uint256 b) internal pure returns (uint256) {
    return a < b ? a : b;
  }
}


contract ERC223 {
  uint public totalSupply;
  function balanceOf(address who) public view returns (uint);
  
  function name() public view returns (string _name);
  function symbol() public view returns (string _symbol);
  function decimals() public view returns (uint8 _decimals);
  function totalSupply() public view returns (uint256 _supply);

  function transfer(address to, uint value) public returns (bool ok);
  function transfer(address to, uint value, bytes data) public returns (bool ok);
  function transfer(address to, uint value, bytes data, string custom_fallback) public returns (bool ok);
  
  event Transfer(address indexed from, address indexed to, uint value, bytes data);
}

contract ContractReceiver {
     
    struct TKN {
        address sender;
        uint value;
        bytes data;
        bytes4 sig;
    }
    
    
    function tokenFallback(address _from, uint _value, bytes _data) public pure {
      TKN memory tkn;
      tkn.sender = _from;
      tkn.value = _value;
      tkn.data = _data;
      uint32 u = uint32(_data[3]) + (uint32(_data[2]) << 8) + (uint32(_data[1]) << 16) + (uint32(_data[0]) << 24);
      tkn.sig = bytes4(u);
      
      /* tkn variable is analogue of msg variable of Ether transaction
      *  tkn.sender is person who initiated this token transaction   (analogue of msg.sender)
      *  tkn.value the number of tokens that were sent   (analogue of msg.value)
      *  tkn.data is data of token transaction   (analogue of msg.data)
      *  tkn.sig is 4 bytes signature of function
      *  if data of token transaction is a function execution
      */
    }
}

contract StandardToken is ERC223 {
    using SafeMath for uint;

    //user token balances
    mapping (address => uint) balances;
    //token transer permissions
    mapping (address => mapping (address => uint)) allowed;

    // Function that is called when a user or another contract wants to transfer funds .
    function transfer(address _to, uint _value, bytes _data, string _custom_fallback) public returns (bool success) {
        if(isContract(_to)) {
            if (balanceOf(msg.sender) < _value) revert();
            balances[msg.sender] = balanceOf(msg.sender).sub(_value);
            balances[_to] = balanceOf(_to).add(_value);
            assert(_to.call.value(0)(bytes4(keccak256(_custom_fallback)), msg.sender, _value, _data));
            Transfer(msg.sender, _to, _value, _data);
            return true;
        }
        else {
            return transferToAddress(_to, _value, _data);
        }
    }
    

    // Function that is called when a user or another contract wants to transfer funds .
    function transfer(address _to, uint _value, bytes _data) public returns (bool success) {
          
        if(isContract(_to)) {
            return transferToContract(_to, _value, _data);
        }
        else {
            return transferToAddress(_to, _value, _data);
        }
    }
      
    // Standard function transfer similar to ERC20 transfer with no _data .
    // Added due to backwards compatibility reasons .
    function transfer(address _to, uint _value) public returns (bool success) {
          
        //standard function transfer similar to ERC20 transfer with no _data
        //added due to backwards compatibility reasons
        bytes memory empty;
        if(isContract(_to)) {
            return transferToContract(_to, _value, empty);
        }
        else {
            return transferToAddress(_to, _value, empty);
        }
    }

    //assemble the given address bytecode. If bytecode exists then the _addr is a contract.
    function isContract(address _addr) private view returns (bool is_contract) {
        uint length;
        assembly {
            //retrieve the size of the code on target address, this needs assembly
            length := extcodesize(_addr)
        }
        return (length > 0);
    }

    //function that is called when transaction target is an address
    function transferToAddress(address _to, uint _value, bytes _data) private returns (bool success) {
        if (balanceOf(msg.sender) < _value) revert();
        balances[msg.sender] = balanceOf(msg.sender).sub(_value);
        balances[_to] = balanceOf(_to).add(_value);
        Transfer(msg.sender, _to, _value, _data);
        return true;
    }
      
      //function that is called when transaction target is a contract
      function transferToContract(address _to, uint _value, bytes _data) private returns (bool success) {
        if (balanceOf(msg.sender) < _value) revert();
        balances[msg.sender] = balanceOf(msg.sender).sub(_value);
        balances[_to] = balanceOf(_to).add(_value);
        ContractReceiver receiver = ContractReceiver(_to);
        receiver.tokenFallback(msg.sender, _value, _data);
        Transfer(msg.sender, _to, _value, _data);
        return true;
    }

    /**
     * Token transfer from from to _to (permission needed)
     */
    function transferFrom(
        address _from, 
        address _to,
        uint _value
    ) 
        public 
        returns (bool)
    {
        if (balanceOf(_from) < _value && allowance(_from, msg.sender) < _value) revert();

        bytes memory empty;
        balances[_to] = balanceOf(_to).add(_value);
        balances[_from] = balanceOf(_from).sub(_value);
        allowed[_from][msg.sender] = allowance(_from, msg.sender).sub(_value);
        if (isContract(_to)) {
            ContractReceiver receiver = ContractReceiver(_to);
            receiver.tokenFallback(msg.sender, _value, empty);
        }
        Transfer(_from, _to, _value, empty);
        return true;
    }

    /**
     * Increase permission for transfer
     */
    function increaseApproval(
        address spender,
        uint value
    )
        public
        returns (bool) 
    {
        allowed[msg.sender][spender] = allowed[msg.sender][spender].add(value);
        return true;
    }

    /**
     * Decrease permission for transfer
     */
    function decreaseApproval(
        address spender,
        uint value
    )
        public
        returns (bool) 
    {
        allowed[msg.sender][spender] = allowed[msg.sender][spender].add(value);
        return true;
    }

    /**
     * User token balance
     */
    function balanceOf(
        address owner
    ) 
        public 
        constant 
        returns (uint) 
    {
        return balances[owner];
    }

    /**
     * User transfer permission
     */
    function allowance(
        address owner, 
        address spender
    )
        public
        constant
        returns (uint remaining)
    {
        return allowed[owner][spender];
    }
}

contract MyDFSToken is StandardToken {

    string public name = "MyDFS Token";
    uint8 public decimals = 6;
    string public symbol = "MyDFS";
    string public version = 'H1.0';
    uint256 public totalSupply;

    function () external {
        revert();
    } 

    function MyDFSToken() public {
        totalSupply = 125 * 1e12;
        balances[msg.sender] = totalSupply;
    }

    // Function to access name of token .
    function name() public view returns (string _name) {
        return name;
    }
    // Function to access symbol of token .
    function symbol() public view returns (string _symbol) {
        return symbol;
    }
    // Function to access decimals of token .
    function decimals() public view returns (uint8 _decimals) {
        return decimals;
    }
    // Function to access total supply of tokens .
    function totalSupply() public view returns (uint256 _totalSupply) {
        return totalSupply;
    }
}