// Vulnerability label: RENT
pragma solidity ^0.4.19;

library SafeMath {
  function mul(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a * b;
    assert(a == 0 || c / a == b);
    return c;
  }

  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a / b;
    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;
  }
}



contract ERC20Basic {
    uint256 public totalSupply;
    function balanceOf(address who) public view returns (uint256);
    function transfer(address to, uint256 value) public returns (bool);
    event Transfer(address indexed from, address indexed to, uint256 value);
}

contract ERC20 is ERC20Basic {
    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 Approval(address indexed owner, address indexed spender, uint256 value);
}

contract RGOinterface {
    
     function RGOFallback(address _from, uint _value, uint _code);
    
}

contract RGO is ERC20 {
    
    using SafeMath for uint256;
    address owner = msg.sender;
  

    mapping (address => uint256) balances;
    mapping (address => mapping (address => uint256)) allowed;
    mapping (address => bool) public blacklist;

    string public constant name = "RGO CHAIN";
    string public constant symbol = "RGO";
    uint public constant decimals = 8;
    uint256 public totalSupply = 100000000e8;

    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
    
   
   
    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }
    
 
    
    function RGO () public {
        owner = msg.sender;
        balances[owner]= 100000000e8;
        Transfer(address(0), owner, 100000000e8);
    }
    
    function transferOwnership(address newOwner) onlyOwner public {
        if (newOwner != address(0)) {
            owner = newOwner;
        }
    }
  
    function () public payable {
    }
    
   
   
    function balanceOf(address _owner)public view  returns (uint256) {
        return balances[_owner];
    }

    // mitigates the ERC20 short address attack
    modifier onlyPayloadSize(uint size) {
        assert(msg.data.length >= size + 4);
        _;
    }
    
 
    
    function transferFrom(address _from, address _to, uint256 _amount) onlyPayloadSize(3 * 32) public returns (bool success) {
        require(_to != address(0));
        require(_amount <= balances[_from]);
        require(_amount <= allowed[_from][msg.sender]);
        
        balances[_from] = balances[_from].sub(_amount);
        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_amount);
        balances[_to] = balances[_to].add(_amount);
        Transfer(_from, _to, _amount);
        return true;
    }
    
    function approve(address _spender, uint256 _value) public returns (bool success) {
        // mitigates the ERC20 spend/approval race condition
        if (_value != 0 && allowed[msg.sender][_spender] != 0) { return false; }
        allowed[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
        return true;
    }
    
    function allowance(address _owner, address _spender) view public returns (uint256) {
        return allowed[_owner][_spender];
    }
    
    
    
    function withdraw() onlyOwner public {
        uint256 etherBalance = this.balance;
        owner.transfer(etherBalance);
    }
    function transfer(address _to, uint _value) public returns (bool) {
        require(_to != address(0));
        require(_value <= balances[msg.sender]);
    
    // SafeMath.sub will throw if there is not enough balance.
        if(!isContract(_to)){
            balances[msg.sender] = balances[msg.sender].sub(_value);
            balances[_to] = balances[_to].add(_value);
            Transfer(msg.sender, _to, _value);
            return true;
            }
        else{
            balances[msg.sender] = balanceOf(msg.sender).sub(_value);
            balances[_to] = balanceOf(_to).add(_value);
            RGOinterface receiver = RGOinterface(_to);
            receiver.RGOFallback(msg.sender, _value, 0);
            Transfer(msg.sender, _to, _value);
            return true;
        }
    }

    function transfer(address _to, uint _value,uint _code) public returns (bool) {
        require(_to != address(0));
        require(_value <= balances[msg.sender]);
    
    // SafeMath.sub will throw if there is not enough balance.
        if(!isContract(_to)){
            balances[msg.sender] = balances[msg.sender].sub(_value);
            balances[_to] = balances[_to].add(_value);
            Transfer(msg.sender, _to, _value);
            return true;
        }
        else{
            balances[msg.sender] = balanceOf(msg.sender).sub(_value);
            balances[_to] = balanceOf(_to).add(_value);
            RGOinterface receiver = RGOinterface(_to);
            receiver.RGOFallback(msg.sender, _value, _code);
            Transfer(msg.sender, _to, _value);
            return true;
        }
    }
    

    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);
  }


}