/*
 * Java Network Programming, Second Edition
 * Merlin Hughes, Michael Shoffner, Derek Hamner
 * Manning Publications Company; ISBN 188477749X
 *
 * http://nitric.com/jnp/
 *
 * Copyright (c) 1997-1999 Merlin Hughes, Michael Shoffner, Derek Hamner;
 * all rights reserved; see license.txt for details.
 */

import java.io.IOException;
import java.io.InterruptedIOException;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.DatagramChannel;

import dns.*;


public class UDPNSLookup {
	public static void main (String[] args) {
		if (args.length != 1)
			throw new IllegalArgumentException
			("Syntax: "+ UDPNSLookup.class.getName()+" <hostname>[@<nameserver>]");

		int atIdx = args[0].indexOf ("@");
		String nameServer = (atIdx > -1) ? args[0].substring (atIdx + 1) : "ns";
		String hostName = (atIdx > -1) ? args[0].substring (0, atIdx) : args[0];

		System.out.println ("Nameserver: " + nameServer);
		System.out.println ("Request: " + hostName);
		DNSQuery query = new DNSQuery (hostName, DNS.TYPE_ANY, DNS.CLASS_IN);
		try {
			boolean received = false;
			int count = 0;
			DatagramChannel sndChan = DatagramChannel.open();
			DatagramSocket socket = sndChan.socket();
			socket.setSoTimeout (1000);
			try {
				while (!received) {
					try {
						sendQuery (query, sndChan, InetAddress.getByName (nameServer),2053);
						getResponse (query, sndChan);
						received = true;
					} catch (InterruptedIOException ex) {
						if (count ++ < 3) {
							System.out.println ("resend..");
						} else {
							throw new IOException ("No response received from nameserver");
						}
					}
				}
			} finally {
				sndChan.close ();
			}
			DNSUtil.printRRs (query);
		} catch (IOException ex) {
			ex.printStackTrace();
			System.out.println (ex);
		}
	}

	public static void sendQuery (DNSQuery query, DatagramChannel chan, InetAddress nameServer, int port) throws IOException {
		byte[] data = query.extractQuery ();
		ByteBuffer dataBuf = ByteBuffer.allocate(512);
		dataBuf.clear();
		dataBuf.put(data);
		dataBuf.flip();
		InetSocketAddress rcvAddress;
		rcvAddress = new InetSocketAddress(nameServer,
				port);
		chan.send(dataBuf, rcvAddress);
	}

	public static void getResponse (DNSQuery query, DatagramChannel chan) throws IOException, InterruptedIOException {
		ByteBuffer dataBuf = ByteBuffer.allocate(512);
		dataBuf.clear();

		chan.receive(dataBuf);

		dataBuf.flip();
		int size = dataBuf.limit();
		byte[] buffer = new byte[size];
		dataBuf.get(buffer);
		query.decodeResponse (buffer, size);
	}
}