pragma solidity ^0.4.20;

contract ERC20Interface {
    
    string public name;
    string public symbol;
    uint8 public decimals;
    uint public totalSupply;
    

    function transfer(address _to, uint256 _value) returns (bool success);
    function transferFrom(address _from, address _to, uint256 _value) returns (bool success);
    function approve(address _spender, uint256 _value) returns (bool success);
    function allowance(address _owner, address _spender) returns (uint256 remaining);
    
   
    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
    
}
contract ERC20 is ERC20Interface {
    
    mapping(address => uint256) public balanceOf;
    mapping(address => mapping(address => uint256)) allowed;
    

    constructor(string _name, string _symbol, uint8 _decimals, uint _totalSupply) public {
       name =  _name;
       symbol = _symbol;
       decimals = _decimals;
       totalSupply = _totalSupply;
       balanceOf[msg.sender] = totalSupply;
    }


    function transfer(address _to, uint256 _value) returns (bool success){
        require(_to != address(0));
        require(balanceOf[msg.sender] >= _value);
        require(balanceOf[ _to] + _value >= balanceOf[ _to]); 

        balanceOf[msg.sender] -= _value;
        balanceOf[_to] += _value;

        emit Transfer(msg.sender, _to, _value);

        return true;
    }
    
    function transferFrom(address _from, address _to, uint256 _value) returns (bool success){
        require(_to != address(0));
        require(allowed[msg.sender][_from] >= _value);
        require(balanceOf[_from] >= _value);
        require(balanceOf[ _to] + _value >= balanceOf[ _to]);

        balanceOf[_from] -= _value;
        balanceOf[_to] += _value;

        allowed[msg.sender][_from] -= _value;

        emit Transfer(msg.sender, _to, _value);
        return true;
    }
    
    function approve(address _spender, uint256 _value) returns (bool success){
        allowed[msg.sender][_spender] = _value;

        emit Approval(msg.sender, _spender, _value);
        return true;
    }
    
 
    function allowance(address _owner, address _spender) returns (uint256 remaining){
         return allowed[_owner][_spender];
    }

}
contract owned {
    address public owner;

    constructor () public {
        owner = msg.sender;
    }
   
  
    modifier onlyOwner {
        require(msg.sender == owner);
        _;
    }
   

    function transferOwnerShip(address newOwer) public onlyOwner {
        owner = newOwer;
    }
}

contract GDChainToken is ERC20, owned {

    mapping (address => bool) public frozenAccount;

    event AddSupply(uint amount);
    event FrozenFunds(address target, bool frozen);
    event Burn(address target, uint amount);

 
    constructor (string _name, string _symbol, uint8 _decimals, uint _totalSupply) 
        ERC20(_name, _symbol, _decimals, _totalSupply) public {
        
    }
   
    function mine(address target, uint amount) public onlyOwner {
        totalSupply += amount;
        balanceOf[target] += amount;

        emit AddSupply(amount);
        emit Transfer(0, target, amount);
    }
    
    function freezeAccount(address target, bool freeze) public onlyOwner {
        frozenAccount[target] = freeze;
        emit FrozenFunds(target, freeze);
    }

    function transfer(address _to, uint256 _value) public returns (bool success) {
        success = _transfer(msg.sender, _to, _value);
    }

    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success){
        require(allowed[_from][msg.sender] >= _value);
        success =  _transfer(_from, _to, _value);
        allowed[_from][msg.sender]  -= _value;
    }

    function _transfer(address _from, address _to, uint256 _value) internal returns (bool) {
      require(_to != address(0));
      require(!frozenAccount[_from]);

      require(balanceOf[_from] >= _value);
      require(balanceOf[ _to] + _value >= balanceOf[ _to]);

      balanceOf[_from] -= _value;
      balanceOf[_to] += _value;

   
      emit Transfer(_from, _to, _value);
      return true;
    }

    function burn(uint256 _value) public returns (bool success) {
       require(balanceOf[msg.sender] >= _value);

       totalSupply -= _value; 
       balanceOf[msg.sender] -= _value;

       emit Burn(msg.sender, _value);
       return true;
    }


    function burnFrom(address _from, uint256 _value)  public returns (bool success) {
        require(balanceOf[_from] >= _value);
        require(allowed[_from][msg.sender] >= _value);

        totalSupply -= _value; 
        balanceOf[msg.sender] -= _value;
        allowed[_from][msg.sender] -= _value;

        emit Burn(msg.sender, _value);
        return true;
    }
}