pragma solidity ^0.4.23;

/**
 * @title DECENTRALIZATION EXCHANGE LTD
 *        62a West Hill, London, United Kingdom, SW18 1RU
 */

/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {
  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;
  }

  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;
  }

  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) {
    uint256 c = a + b;
    assert(c >= a);
    return c;
  }
}

interface ERC20 {
  function balanceOf(address who) public view returns (uint256);
  function transfer(address to, uint256 value) public returns (bool);
  function allowance(address owner, address spender) public view returns (uint256);
  function transferFrom(address from, address to, uint256 value) public returns (bool);
  function approve(address spender, uint256 value) public returns (bool);
  event Transfer(address indexed from, address indexed to, uint256 value);
  event Approval(address indexed owner, address indexed spender, uint256 value);
}

/**
 * @title ERC223
 * @dev ERC223 contract interface with ERC20 functions and events
 *      Fully backward compatible with ERC20
 *      Recommended implementation used at https://github.com/Dexaran/ERC223-token-standard/tree/Recommended
 */

interface ERC223 {
    function transfer(address to, uint value, bytes data) public;
    event Transfer(address indexed from, address indexed to, uint value, bytes indexed data);
}

 /*
 * Contract that is working with ERC223 tokens
 */

contract ContractReceiver {

    struct TKN {
        address sender;
        uint value;
        bytes data;
        bytes4 sig;
    }


    function tokenFallback(address _from, uint _value, bytes _data){
      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
      */
    }

    function rewiewToken  () returns (address, uint, bytes, bytes4) {
        TKN memory tkn;

        return (tkn.sender, tkn.value, tkn.data, tkn.sig);

    }
}

/**
 * DECENTRALIZATION EXCHANGE LTD
 * 62a West Hill, London, United Kingdom, SW18 1RU
 */
 
contract ERC223ReceivingContract { 
    function tokenFallback(address _from, uint _value, bytes _data) public;
}

contract SmartExchange is ERC20, ERC223 {
  using SafeMath for uint;
     
    string internal _name;
    string internal _symbol;
    uint8 internal _decimals;
    uint256 internal _totalSupply;

    mapping (address => uint256) internal balances;
    mapping (address => mapping (address => uint256)) internal allowed;

    function SmartExchange (string name, string symbol, uint8 decimals, uint256 totalSupply) public {
        _symbol = "SDE";
        _name = "Smart Exchange";
        _decimals = 18;
        _totalSupply = 28000000 * 1e18;
        balances[msg.sender] = 28000000 * 1e18;
    }

    function name()
        public
        view
        returns (string) {
        return _name;
    }

    function symbol()
        public
        view
        returns (string) {
        return _symbol;
    }

    function decimals()
        public
        view
        returns (uint8) {
        return _decimals;
    }

    function totalSupply()
        public
        view
        returns (uint256) {
        return _totalSupply;
    }

   function transfer(address _to, uint256 _value) public returns (bool) {
     require(_to != address(0));
     require(_value <= balances[msg.sender]);
     balances[msg.sender] = SafeMath.sub(balances[msg.sender], _value);
     balances[_to] = SafeMath.add(balances[_to], _value);
     Transfer(msg.sender, _to, _value);
     return true;
   }

  function balanceOf(address _owner) public view returns (uint256 balance) {
    return balances[_owner];
   }

  function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
    require(_to != address(0));
     require(_value <= balances[_from]);
     require(_value <= allowed[_from][msg.sender]);

    balances[_from] = SafeMath.sub(balances[_from], _value);
     balances[_to] = SafeMath.add(balances[_to], _value);
     allowed[_from][msg.sender] = SafeMath.sub(allowed[_from][msg.sender], _value);
    Transfer(_from, _to, _value);
     return true;
   }

   function approve(address _spender, uint256 _value) public returns (bool) {
     allowed[msg.sender][_spender] = _value;
     Approval(msg.sender, _spender, _value);
     return true;
   }

  function allowance(address _owner, address _spender) public view returns (uint256) {
     return allowed[_owner][_spender];
   }

   function increaseApproval(address _spender, uint _addedValue) public returns (bool) {
     allowed[msg.sender][_spender] = SafeMath.add(allowed[msg.sender][_spender], _addedValue);
     Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
     return true;
   }

  function decreaseApproval(address _spender, uint _subtractedValue) public returns (bool) {
     uint oldValue = allowed[msg.sender][_spender];
     if (_subtractedValue > oldValue) {
       allowed[msg.sender][_spender] = 0;
     } else {
       allowed[msg.sender][_spender] = SafeMath.sub(oldValue, _subtractedValue);
    }
     Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
     return true;
   }
   
  function transfer(address _to, uint _value, bytes _data) public {
    require(_value > 0 );
    if(isContract(_to)) {
        ERC223ReceivingContract receiver = ERC223ReceivingContract(_to);
        receiver.tokenFallback(msg.sender, _value, _data);
    }
        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);
        Transfer(msg.sender, _to, _value, _data);
    }
    
  function isContract(address _addr) private 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);
    }

}