/*

  *   SONEWS News Server

  *   see AUTHORS for the list of contributors

  *

  *   This program is free software: you can redistribute it and/or modify

  *   it under the terms of the GNU General Public License as published by

  *   the Free Software Foundation, either version 3 of the License, or

  *   (at your option) any later version.

  *

  *   This program is distributed in the hope that it will be useful,

  *   but WITHOUT ANY WARRANTY; without even the implied warranty of

  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

  *   GNU General Public License for more details.

  *

  *   You should have received a copy of the GNU General Public License

  *   along with this program.  If not, see <http://www.gnu.org/licenses/>.

  */

 package org.sonews.daemon;

 import org.sonews.config.Config;

 import org.sonews.Main;

 import org.sonews.util.Log;

 import java.io.IOException;

 import java.net.BindException;

 import java.net.InetSocketAddress;

 import java.net.ServerSocket;

 import java.nio.channels.CancelledKeyException;

 import java.nio.channels.ClosedChannelException;

 import java.nio.channels.SelectionKey;

 import java.nio.channels.Selector;

 import java.nio.channels.ServerSocketChannel;

 import java.nio.channels.SocketChannel;

 /**

  * NNTP daemon using SelectableChannels.

  * @author Christian Lins

  * @since sonews/0.5.0

  */

 public final class NNTPDaemon extends AbstractDaemon

 {

 	public static final Object RegisterGate = new Object();

 	private static NNTPDaemon instance = null;

 	public static synchronized NNTPDaemon createInstance(int port)

 	{

 		if (instance == null) {

 			instance = new NNTPDaemon(port);

 			return instance;

 		} else {

 			throw new RuntimeException("NNTPDaemon.createInstance() called twice");

 		}

 	}

 	private int port;

 	private NNTPDaemon(final int port)

 	{

 		Log.get().info("Server listening on port " + port);

 		this.port = port;

 	}

 	@Override

 	public void run()

 	{

 		try {

 			// Create a Selector that handles the SocketChannel multiplexing

 			final Selector readSelector = Selector.open();

 			final Selector writeSelector = Selector.open();

 			// Start working threads

 			final int workerThreads = Runtime.getRuntime().availableProcessors() * 4;

 			ConnectionWorker[] cworkers = new ConnectionWorker[workerThreads];

 			for (int n = 0; n < workerThreads; n++) {

 				cworkers[n] = new ConnectionWorker();

 				cworkers[n].start();

 			}

 			ChannelWriter.getInstance().setSelector(writeSelector);

 			ChannelReader.getInstance().setSelector(readSelector);

 			ChannelWriter.getInstance().start();

 			ChannelReader.getInstance().start();

 			final ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();

 			serverSocketChannel.configureBlocking(true);  // Set to blocking mode

 			// Configure ServerSocket; bind to socket...

 			final ServerSocket serverSocket = serverSocketChannel.socket();

 			serverSocket.bind(new InetSocketAddress(this.port));

 			while (isRunning()) {

 				SocketChannel socketChannel;

 				try {

 					// As we set the server socket channel to blocking mode the accept()

 					// method will block.

 					socketChannel = serverSocketChannel.accept();

 					socketChannel.configureBlocking(false);

 					assert socketChannel.isConnected();

 					assert socketChannel.finishConnect();

 				} catch (IOException ex) {

 					// Under heavy load an IOException "Too many open files may

 					// be thrown. It most cases we should slow down the connection

 					// accepting, to give the worker threads some time to process work.

 					Log.get().severe("IOException while accepting connection: " + ex.getMessage());

 					Log.get().info("Connection accepting sleeping for seconds...");

 					Thread.sleep(5000); // 5 seconds

 					continue;

 				}

 				final NNTPConnection conn;

 				try {

 					conn = new NNTPConnection(socketChannel);

 					Connections.getInstance().add(conn);

 				} catch (IOException ex) {

 					Log.get().warning(ex.toString());

 					socketChannel.close();

 					continue;

 				}

 				try {

 					SelectionKey selKeyWrite =

 						registerSelector(writeSelector, socketChannel, SelectionKey.OP_WRITE);

 					registerSelector(readSelector, socketChannel, SelectionKey.OP_READ);

 					Log.get().info("Connected: " + socketChannel.socket().getRemoteSocketAddress());

 					// Set write selection key and send hello to client

 					conn.setWriteSelectionKey(selKeyWrite);

 					conn.println("200 " + Config.inst().get(Config.HOSTNAME, "localhost")

 						+ " " + Main.VERSION + " news server ready - (posting ok).");

 				} catch (CancelledKeyException cke) {

 					Log.get().warning("CancelledKeyException " + cke.getMessage() + " was thrown: "

 						+ socketChannel.socket());

 				} catch (ClosedChannelException cce) {

 					Log.get().warning("ClosedChannelException " + cce.getMessage() + " was thrown: "

 						+ socketChannel.socket());

 				}

 			}

 		} catch (BindException ex) {

 			// Could not bind to socket; this is a fatal problem; so perform shutdown

 			ex.printStackTrace();

 			System.exit(1);

 		} catch (IOException ex) {

 			ex.printStackTrace();

 		} catch (Exception ex) {

 			ex.printStackTrace();

 		}

 	}

 	public static SelectionKey registerSelector(final Selector selector,

 		final SocketChannel channel, final int op)

 		throws CancelledKeyException, ClosedChannelException

 	{

 		// Register the selector at the channel, so that it will be notified

 		// on the socket's events

 		synchronized (RegisterGate) {

 			// Wakeup the currently blocking reader/writer thread; we have locked

 			// the RegisterGate to prevent the awakened thread to block again

 			selector.wakeup();

 			// Lock the selector to prevent the waiting worker threads going into

 			// selector.select() which would block the selector.

 			synchronized (selector) {

 				return channel.register(selector, op, null);

 			}

 		}

 	}

 }