pragma solidity ^0.4.20;

contract ERC20ext
{
  function totalSupply() public constant returns (uint supply);
  function balanceOf( address who ) public constant returns (uint value);
  function allowance( address owner, address spender ) public constant returns (uint _allowance);

  function transfer( address to, uint value) public returns (bool ok);
  function transferFrom( address from, address to, uint value) public returns (bool ok);
  function approve( address spender, uint value ) public returns (bool ok);

  event Transfer( address indexed from, address indexed to, uint value);
  event Approval( address indexed owner, address indexed spender, uint value);

  function postMessage(address dst, uint wad,string data) public returns (bool ok);
  function appointNewCFO(address newCFO) public returns (bool ok);

  function melt(address dst, uint256 wad) public returns (bool ok);
  function mint(address dst, uint256 wad) public returns (bool ok);
  function freeze(address dst, bool flag) public returns (bool ok);

  event MeltEvent(address indexed dst, uint256 wad);
  event MintEvent(address indexed dst, uint256 wad);
  event FreezeEvent(address indexed dst, bool flag);
}

contract SafeMath 
{
  function mul(uint256 a, uint256 b) internal pure returns (uint256 c) 
  {
    if (a == 0) {
      return 0;
    }
    c = a * b;
    assert(c / a == b);
    return c;
  }

  function div(uint256 a, uint256 b) internal pure returns (uint256) 
  {
    return a / b;
  }

  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 c) 
  {
    c = a + b;
    assert(c >= a);
    return c;
  }
}

contract SGCH is ERC20ext,SafeMath
{
  string public name;
  string public symbol;
  uint8  public decimals = 18;

  address _cfo;
  uint256 _supply;

  mapping (address => uint256) _balances;
  mapping (address => mapping (address => uint256)) _allowance;
  mapping (address => bool) public _frozen;

  function SGCH(uint256 initialSupply,string tokenName,string tokenSymbol) public
  {
    _cfo    = msg.sender;
    _supply = initialSupply * 10 ** uint256(decimals);
    _balances[_cfo] = _supply;

    name   = tokenName;
    symbol = tokenSymbol;
  }

  modifier onlyCFO()
  {
    require(msg.sender == _cfo);
    _;
  }

  function totalSupply() public constant returns (uint256)
  {
    return _supply;
  }
  function balanceOf(address src) public constant returns (uint256)
  {
    return _balances[src];
  }
  function allowance(address src, address dst) public constant returns (uint256)
  {
    return _allowance[src][dst];
  }
  function transfer(address dst, uint wad) public returns (bool)
  {
    require(!_frozen[msg.sender]);
    require(!_frozen[dst]);

    require(_balances[msg.sender] >= wad);

    _balances[msg.sender] = sub(_balances[msg.sender],wad);
    _balances[dst]        = add(_balances[dst], wad);

    Transfer(msg.sender, dst, wad);

    return true;
  }
  function transferFrom(address src, address dst, uint wad) public returns (bool)
  {
    require(!_frozen[msg.sender]);
    require(!_frozen[dst]);

    require(_balances[src] >= wad);

    require(_allowance[src][msg.sender] >= wad);

    _allowance[src][msg.sender] = sub(_allowance[src][msg.sender],wad);

    _balances[src] = sub(_balances[src],wad);
    _balances[dst] = add(_balances[dst],wad);

    Transfer(src, dst, wad);

    return true;
  }

  function approve(address dst, uint256 wad) public returns (bool)
  {
    _allowance[msg.sender][dst] = wad;

    Approval(msg.sender, dst, wad);
    return true;
  }

  function postMessage(address dst, uint wad,string data) public returns (bool)
  {
    return transfer(dst,wad);
  }
  function appointNewCFO(address newCFO) onlyCFO public returns (bool)
  {
    if (newCFO != _cfo)
    {
      _cfo = newCFO;
      return true;
    }
    else
    {
      return false;
    }
  }

  function freeze(address dst, bool flag) onlyCFO public returns (bool)
  {
    _frozen[dst] = flag;

    FreezeEvent(dst, flag);
    return true;
  }

  function mint(address dst, uint256 wad) onlyCFO public returns (bool)
  {
    _balances[dst] = add(_balances[dst],wad);
    _supply        = add(_supply,wad);

    MintEvent(dst, wad);
    return true;
  }

  function melt(address dst, uint256 wad) onlyCFO public returns (bool)
  {
    require(_balances[dst] >= wad);

    _balances[dst] = sub(_balances[dst],wad);
    _supply        = sub(_supply,wad);

    MeltEvent(dst, wad);
    return true;
  }
}