package discovery.server;

import constants.Constants;
import java.net.*;
import java.util.Enumeration;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @author Mark, and Christopher Frantz
 */
public class BroadcastResponder extends Thread {

	private static final Logger LOG = Logger.getLogger(BroadcastResponder.class.getName());
	private final String lab;

	public BroadcastResponder(final String lab) {
		super();
		super.setDaemon(true);
		this.lab = lab;
	}

	@Override
	public void run() {
		try {
			final MulticastSocket socket = new MulticastSocket(Constants.PORT);
			socket.joinGroup(InetAddress.getByName(Constants.BROADCAST_ADDRESS));

			final int bufferSize = 255;

			while (true) {
				byte[] buffer = new byte[bufferSize]; // NOPMD: need to reset buffer each time
				final DatagramPacket packet = new DatagramPacket(buffer, buffer.length);  // NOPMD: safer to create new packets than try to reuse
				socket.receive(packet);
				final String requestedLab = new String(packet.getData()).trim();  // NOPMD: String.valueOf does not handle byte[] properly...
				if (requestedLab.equalsIgnoreCase(lab)) {
					final String serverIp = this.getServerIp();
					buffer = serverIp.getBytes();
					packet.setData(buffer);
					socket.send(packet);
				}
			}

		} catch (Exception ex) {
			LOG.log(Level.SEVERE, null, ex);
		}

	}

	/**
	 * This code comes from Christopher Frantz and seems less likely to pick the
	 * loopback IP address than other ways.
	 */
	private String getServerIp() {
		try {

			for (final Enumeration<NetworkInterface> en
					= NetworkInterface.getNetworkInterfaces(); en.hasMoreElements();) {

				final NetworkInterface intf = en.nextElement();

				for (final Enumeration<InetAddress> enumIpAddr = intf.getInetAddresses(); enumIpAddr.hasMoreElements();) {

					final InetAddress inetAddress = enumIpAddr.nextElement();

					try {

                  // FIXME: Quick hack to ensure we are only getting IPv4 
						//        addresses - need to test what happens with IPv6
						//        addresses.
						//        
						//        This variable is never used - the cast is to check
						//        if IPv4 or 6.
						final Inet4Address testIfIpv4 = (Inet4Address) inetAddress;  // NOPMD: see above comment

						if (!inetAddress.isLoopbackAddress()) {
							return inetAddress.getHostAddress().toString();
						}

					} catch (ClassCastException ignored) {
						continue;
					}

				}
			}

		} catch (Exception ex) {
			LOG.log(Level.SEVERE, null, ex);
		}
		return null;
	}
}