/*
 * 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.channels.DatagramChannel;
import dns.*;


public class UDPNSLookupBase {
	public static void main (String[] args) {
		if (args.length != 1)
			throw new IllegalArgumentException
			("Syntax: "+ UDPNSLookupBase.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 = null;
			/* TODO 
			 * create the datagramChannel
			 */
			DatagramSocket socket = sndChan.socket();
			socket.setSoTimeout (5000);
			try {
				while (!received) {
					try {
						sendQuery (query, sndChan, InetAddress.getByName (nameServer));
						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) throws IOException {
		byte[] data = query.extractQuery ();
		InetSocketAddress rcvAddress;
		rcvAddress = new InetSocketAddress(nameServer, DNS.DEFAULT_PORT);
		/* TODO 
		 * send the data obtained from the query to the datagramChannel
		 * at the server referred by the InetAddress to the default DNS port DNS.DEFAULT_PORT (53)
		 */
	}

	public static void getResponse (DNSQuery query, DatagramChannel chan) throws IOException {
		/* TODO 
		 * receive at max 512 bytes from the server as a response
		 * put data in buffer and data size in size
		 */		
		int size = 0;
		byte[] buffer = null;

		query.decodeResponse (buffer, size);
	}
}