pragma solidity ^0.4.23;

library 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 ERC20Basic {
    function totalSupply() public view returns (uint256);

    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 BasicToken is ERC20Basic {
    using SafeMath for uint256;
    mapping(address => uint256) balances;
    mapping(address => bool) public frozenAccount;
    uint256 totalSupply_;

    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]);
        require(!frozenAccount[msg.sender]);
        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);
        emit Transfer(msg.sender, _to, _value);
        return true;
    }

    function balanceOf(address _owner) public view returns (uint256) {
        return balances[_owner];
    }
}

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 StandardToken is ERC20, BasicToken {
    mapping(address => mapping(address => uint256)) internal allowed;

    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] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(_value);
        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
        emit Transfer(_from, _to, _value);
        return true;
    }

    function approve(address _spender, uint256 _value) public returns (bool) {
        allowed[msg.sender][_spender] = _value;
        emit 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] = (
        allowed[msg.sender][_spender].add(_addedValue));
        emit 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] = oldValue.sub(_subtractedValue);
        }
        emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
        return true;
    }
}

contract Ownable {
    address public owner;

    event OwnershipRenounced(address indexed previousOwner);
    event OwnershipTransferred(
        address indexed previousOwner,
        address indexed newOwner
    );

    constructor() public {
        owner = msg.sender;
    }

    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }

    function transferOwnership(address newOwner) public onlyOwner {
        require(newOwner != address(0));
        emit OwnershipTransferred(owner, newOwner);
        owner = newOwner;
    }

    function renounceOwnership() public onlyOwner {
        emit OwnershipRenounced(owner);
        owner = address(0);
    }
}

contract NASTToken is StandardToken, Ownable {
    string public constant name = "Node All-Star";
    string public constant symbol = "NAST";
    uint8 public constant decimals = 18;
    uint256 public constant INITIAL_SUPPLY = 100000000000 * (10 ** uint256(decimals));

    event Burn(address indexed burner, uint256 value);
    event FrozenFunds(address target, bool frozen);

    constructor() public {
        totalSupply_ = INITIAL_SUPPLY;
        balances[msg.sender] = INITIAL_SUPPLY;
        emit Transfer(0x0, msg.sender, INITIAL_SUPPLY);
    }

    function burnFrom(address _who, uint256 _value) public onlyOwner {
        require(_value <= allowed[_who][msg.sender]);
        allowed[_who][msg.sender] = allowed[_who][msg.sender].sub(_value);

        require(_value <= balances[_who]);
        balances[_who] = balances[_who].sub(_value);
        totalSupply_ = totalSupply_.sub(_value);
        emit Burn(_who, _value);
        emit Transfer(_who, address(0), _value);
    }

    function freezeAccount(address _who, bool freeze) public onlyOwner {
        frozenAccount[_who] = freeze;
        emit FrozenFunds(_who, freeze);
    }
}