/*
 * 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.*;

import java.net.*;
import java.nio.ByteBuffer;
import java.nio.channels.SocketChannel;

import dns.DNS;
import dns.DNSQuery;
import dns.DNSUtil;

public class NSLookup {
	private static boolean debug = true;
	public static void main (String[] args) {
		if (args.length != 1)
			throw new IllegalArgumentException
			("Syntax: "+ NSLookup.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 {
			SocketChannel rwChan = SocketChannel.open();
			Socket socket = rwChan.socket();
			InetAddress destAddr = InetAddress.getByName(nameServer);
			InetSocketAddress rcvAddress =  new InetSocketAddress(destAddr, DNS.DEFAULT_PORT);
			socket.connect(rcvAddress);
			socket.setSoTimeout (10000);
			sendQuery (query, rwChan);
			getResponse (query, rwChan);
			rwChan.close ();
			DNSUtil.printRRs (query);
		} catch (IOException ex) {
			ex.printStackTrace();
		}
	}
	public static void sendQuery (DNSQuery query, SocketChannel chan) throws IOException {
		byte[] data = query.extractQuery ();
		ByteBuffer dataBuf = ByteBuffer.allocate(data.length+2);
		dataBuf.putShort((short)data.length);
		dataBuf.put(data);
		dataBuf.flip();
		chan.write(dataBuf);
	}

	public static void getResponse (DNSQuery query, SocketChannel chan) throws IOException {
		ByteBuffer dataBuf = ByteBuffer.allocate(2048);
		chan.read(dataBuf);
		dataBuf.flip();
		int datasize = dataBuf.limit() - 2 ;
		int responseSize = dataBuf.getShort();
		if(debug) {
				System.out.println("ResponseSize & datasize : " + responseSize +
						" " + datasize);
		}
		byte[] buffer = new byte[datasize];
		dataBuf.get(buffer);
		query.decodeResponse (buffer, buffer.length);
	}
}