/*

  *   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 java.io.IOException;

 import java.net.InetSocketAddress;

 import java.net.SocketException;

 import java.nio.ByteBuffer;

 import java.nio.CharBuffer;

 import java.nio.channels.ClosedChannelException;

 import java.nio.channels.SelectionKey;

 import java.nio.channels.SocketChannel;

 import java.nio.charset.Charset;

 import java.util.Arrays;

 import java.util.Timer;

 import java.util.TimerTask;

 import java.util.logging.Level;

 import org.sonews.daemon.command.Command;

 import org.sonews.storage.Article;

 import org.sonews.storage.Group;

 import org.sonews.storage.StorageBackendException;

 import org.sonews.util.Log;

 import org.sonews.util.Stats;

 /**

  * For every SocketChannel (so TCP/IP connection) there is an instance of

  * this class.

  * @author Christian Lins

  * @since sonews/0.5.0

  */

 public final class NNTPConnection {

 	public static final String NEWLINE = "\r\n";    // RFC defines this as newline

 	public static final String MESSAGE_ID_PATTERN = "<[^>]+>";

 	private static final Timer cancelTimer = new Timer(true); // Thread-safe? True for run as daemon

 	/** SocketChannel is generally thread-safe */

 	private SocketChannel channel = null;

 	private Charset charset = Charset.forName("UTF-8");

 	private Command command = null;

 	private Article currentArticle = null;

 	private Group currentGroup = null;

 	private volatile long lastActivity = System.currentTimeMillis();

 	private ChannelLineBuffers lineBuffers = new ChannelLineBuffers();

 	private int readLock = 0;

 	private final Object readLockGate = new Object();

 	private SelectionKey writeSelKey = null;

 	public NNTPConnection(final SocketChannel channel)

 			throws IOException {

 		if (channel == null) {

 			throw new IllegalArgumentException("channel is null");

 		}

 		this.channel = channel;

 		Stats.getInstance().clientConnect();

 	}

 	/**

 	 * Tries to get the read lock for this NNTPConnection. This method is Thread-

 	 * safe and returns true of the read lock was successfully set. If the lock

 	 * is still hold by another Thread the method returns false.

 	 */

 	boolean tryReadLock() {

 		// As synchronizing simple types may cause deadlocks,

 		// we use a gate object.

 		synchronized (readLockGate) {

 			if (readLock != 0) {

 				return false;

 			} else {

 				readLock = Thread.currentThread().hashCode();

 				return true;

 			}

 		}

 	}

 	/**

 	 * Releases the read lock in a Thread-safe way.

 	 * @throws IllegalMonitorStateException if a Thread not holding the lock

 	 * tries to release it.

 	 */

 	void unlockReadLock() {

 		synchronized (readLockGate) {

 			if (readLock == Thread.currentThread().hashCode()) {

 				readLock = 0;

 			} else {

 				throw new IllegalMonitorStateException();

 			}

 		}

 	}

 	/**

 	 * @return Current input buffer of this NNTPConnection instance.

 	 */

 	public ByteBuffer getInputBuffer() {

 		return this.lineBuffers.getInputBuffer();

 	}

 	/**

 	 * @return Output buffer of this NNTPConnection which has at least one byte

 	 * free storage.

 	 */

 	public ByteBuffer getOutputBuffer() {

 		return this.lineBuffers.getOutputBuffer();

 	}

 	/**

 	 * @return ChannelLineBuffers instance associated with this NNTPConnection.

 	 */

 	public ChannelLineBuffers getBuffers() {

 		return this.lineBuffers;

 	}

 	/**

 	 * @return true if this connection comes from a local remote address.

 	 */

 	public boolean isLocalConnection() {

 		return ((InetSocketAddress) this.channel.socket().getRemoteSocketAddress()).getHostName().equalsIgnoreCase("localhost");

 	}

 	void setWriteSelectionKey(SelectionKey selKey) {

 		this.writeSelKey = selKey;

 	}

 	public void shutdownInput() {

 		try {

 			// Closes the input line of the channel's socket, so no new data

 			// will be received and a timeout can be triggered.

 			this.channel.socket().shutdownInput();

 		} catch (IOException ex) {

 			Log.get().warning("Exception in NNTPConnection.shutdownInput(): " + ex);

 		}

 	}

 	public void shutdownOutput() {

 		cancelTimer.schedule(new TimerTask() {

 			@Override

 			public void run() {

 				try {

 					// Closes the output line of the channel's socket.

 					channel.socket().shutdownOutput();

 					channel.close();

 				} catch (SocketException ex) {

 					// Socket was already disconnected

 					Log.get().info("NNTPConnection.shutdownOutput(): " + ex);

 				} catch (Exception ex) {

 					Log.get().warning("NNTPConnection.shutdownOutput(): " + ex);

 				}

 			}

 		}, 3000);

 	}

 	public SocketChannel getSocketChannel() {

 		return this.channel;

 	}

 	public Article getCurrentArticle() {

 		return this.currentArticle;

 	}

 	public Charset getCurrentCharset() {

 		return this.charset;

 	}

 	/**

 	 * @return The currently selected communication channel (not SocketChannel)

 	 */

 	public Group getCurrentChannel() {

 		return this.currentGroup;

 	}

 	public void setCurrentArticle(final Article article) {

 		this.currentArticle = article;

 	}

 	public void setCurrentGroup(final Group group) {

 		this.currentGroup = group;

 	}

 	public long getLastActivity() {

 		return this.lastActivity;

 	}

 	/**

 	 * Due to the readLockGate there is no need to synchronize this method.

 	 * @param raw

 	 * @throws IllegalArgumentException if raw is null.

 	 * @throws IllegalStateException if calling thread does not own the readLock.

 	 */

 	void lineReceived(byte[] raw) {

 		if (raw == null) {

 			throw new IllegalArgumentException("raw is null");

 		}

 		if (readLock == 0 || readLock != Thread.currentThread().hashCode()) {

 			throw new IllegalStateException("readLock not properly set");

 		}

 		this.lastActivity = System.currentTimeMillis();

 		String line = new String(raw, this.charset);

 		// There might be a trailing \r, but trim() is a bad idea

 		// as it removes also leading spaces from long header lines.

 		if (line.endsWith("\r")) {

 			line = line.substring(0, line.length() - 1);

 			raw = Arrays.copyOf(raw, raw.length - 1);

 		}

 		Log.get().fine("<< " + line);

 		if (command == null) {

 			command = parseCommandLine(line);

 			assert command != null;

 		}

 		try {

 			// The command object will process the line we just received

 			try {

 				command.processLine(this, line, raw);

 			} catch (StorageBackendException ex) {

 				Log.get().info("Retry command processing after StorageBackendException");

 				// Try it a second time, so that the backend has time to recover

 				command.processLine(this, line, raw);

 			}

 		} catch (ClosedChannelException ex0) {

 			try {

 				StringBuilder strBuf = new StringBuilder();

 				strBuf.append("Connection to ");

 				strBuf.append(channel.socket().getRemoteSocketAddress());

 				strBuf.append(" closed: ");

 				strBuf.append(ex0);

 				Log.get().info(strBuf.toString());

 			} catch (Exception ex0a) {

 				ex0a.printStackTrace();

 			}

 		} catch (Exception ex1) { // This will catch a second StorageBackendException

 			try {

 				command = null;

 				Log.get().log(Level.WARNING, ex1.getLocalizedMessage(), ex1);

 				println("403 Internal server error");

 				// Should we end the connection here?

 				// RFC says we MUST return 400 before closing the connection

 				shutdownInput();

 				shutdownOutput();

 			} catch (Exception ex2) {

 				ex2.printStackTrace();

 			}

 		}

 		if (command == null || command.hasFinished()) {

 			command = null;

 			charset = Charset.forName("UTF-8"); // Reset to default

 		}

 	}

 	/**

 	 * This method determines the fitting command processing class.

 	 * @param line

 	 * @return

 	 */

 	private Command parseCommandLine(String line) {

 		String cmdStr = line.split(" ")[0];

 		return CommandSelector.getInstance().get(cmdStr);

 	}

 	/**

 	 * Puts the given line into the output buffer, adds a newline character

 	 * and returns. The method returns immediately and does not block until

 	 * the line was sent. If line is longer than 510 octets it is split up in

 	 * several lines. Each line is terminated by \r\n (NNTPConnection.NEWLINE).

 	 * @param line

 	 */

 	public void println(final CharSequence line, final Charset charset)

 			throws IOException {

 		writeToChannel(CharBuffer.wrap(line), charset, line);

 		writeToChannel(CharBuffer.wrap(NEWLINE), charset, null);

 	}

 	/**

 	 * Writes the given raw lines to the output buffers and finishes with

 	 * a newline character (\r\n).

 	 * @param rawLines

 	 */

 	public void println(final byte[] rawLines)

 			throws IOException {

 		this.lineBuffers.addOutputBuffer(ByteBuffer.wrap(rawLines));

 		writeToChannel(CharBuffer.wrap(NEWLINE), charset, null);

 	}

 	/**

 	 * Encodes the given CharBuffer using the given Charset to a bunch of

 	 * ByteBuffers (each 512 bytes large) and enqueues them for writing at the

 	 * connected SocketChannel.

 	 * @throws java.io.IOException

 	 */

 	private void writeToChannel(CharBuffer characters, final Charset charset,

 			CharSequence debugLine)

 			throws IOException {

 		if (!charset.canEncode()) {

 			Log.get().severe("FATAL: Charset " + charset + " cannot encode!");

 			return;

 		}

 		// Write characters to output buffers

 		LineEncoder lenc = new LineEncoder(characters, charset);

 		lenc.encode(lineBuffers);

 		enableWriteEvents(debugLine);

 	}

 	private void enableWriteEvents(CharSequence debugLine) {

 		// Enable OP_WRITE events so that the buffers are processed

 		try {

 			this.writeSelKey.interestOps(SelectionKey.OP_WRITE);

 			ChannelWriter.getInstance().getSelector().wakeup();

 		} catch (Exception ex) // CancelledKeyException and ChannelCloseException

 		{

 			Log.get().warning("NNTPConnection.writeToChannel(): " + ex);

 			return;

 		}

 		// Update last activity timestamp

 		this.lastActivity = System.currentTimeMillis();

 		if (debugLine != null) {

 			Log.get().fine(">> " + debugLine);

 		}

 	}

 	public void println(final CharSequence line)

 			throws IOException {

 		println(line, charset);

 	}

 	public void print(final String line)

 			throws IOException {

 		writeToChannel(CharBuffer.wrap(line), charset, line);

 	}

 	public void setCurrentCharset(final Charset charset) {

 		this.charset = charset;

 	}

 	void setLastActivity(long timestamp) {

 		this.lastActivity = timestamp;

 	}

 }