/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 *
 */
package org.apache.mina.filter.codec;

import java.net.SocketAddress;
import java.util.Queue;

import org.apache.mina.core.buffer.IoBuffer;
import org.apache.mina.core.file.FileRegion;
import org.apache.mina.core.filterchain.IoFilter;
import org.apache.mina.core.filterchain.IoFilterAdapter;
import org.apache.mina.core.filterchain.IoFilterChain;
import org.apache.mina.core.future.WriteFuture;
import org.apache.mina.core.session.AttributeKey;
import org.apache.mina.core.session.IoSession;
import org.apache.mina.core.write.DefaultWriteRequest;
import org.apache.mina.core.write.WriteRequest;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * An {@link IoFilter} which translates binary or protocol specific data into
 * message objects and vice versa using {@link ProtocolCodecFactory},
 * {@link ProtocolEncoder}, or {@link ProtocolDecoder}.
 *
 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
 * @org.apache.xbean.XBean
 */
public class ProtocolCodecFilter extends IoFilterAdapter {
	/** A logger for this class */
	private static final Logger LOGGER = LoggerFactory.getLogger(ProtocolCodecFilter.class);

	private static final Class<?>[] EMPTY_PARAMS = new Class[0];

	private static final IoBuffer EMPTY_BUFFER = IoBuffer.wrap(new byte[0]);

	private static final AttributeKey ENCODER = new AttributeKey(ProtocolCodecFilter.class, "encoder");

	private static final AttributeKey DECODER = new AttributeKey(ProtocolCodecFilter.class, "decoder");

	private static final ProtocolDecoderOutputLocal DECODER_OUTPUT = new ProtocolDecoderOutputLocal();

	private static final ProtocolEncoderOutputLocal ENCODER_OUTPUT = new ProtocolEncoderOutputLocal();

	/** The factory responsible for creating the encoder and decoder */
	private final ProtocolCodecFactory factory;

	/**
	 * Creates a new instance of ProtocolCodecFilter, associating a factory for the
	 * creation of the encoder and decoder.
	 *
	 * @param factory The associated factory
	 */
	public ProtocolCodecFilter(ProtocolCodecFactory factory) {
		if (factory == null) {
			throw new IllegalArgumentException("factory");
		}

		this.factory = factory;
	}

	/**
	 * Creates a new instance of ProtocolCodecFilter, without any factory. The
	 * encoder/decoder factory will be created as an inner class, using the two
	 * parameters (encoder and decoder).
	 * 
	 * @param encoder The class responsible for encoding the message
	 * @param decoder The class responsible for decoding the message
	 */
	public ProtocolCodecFilter(final ProtocolEncoder encoder, final ProtocolDecoder decoder) {
		if (encoder == null) {
			throw new IllegalArgumentException("encoder");
		}
		if (decoder == null) {
			throw new IllegalArgumentException("decoder");
		}

		// Create the inner Factory based on the two parameters
		this.factory = new ProtocolCodecFactory() {
			/**
			 * {@inheritDoc}
			 */
			@Override
			public ProtocolEncoder getEncoder(IoSession session) {
				return encoder;
			}

			/**
			 * {@inheritDoc}
			 */
			@Override
			public ProtocolDecoder getDecoder(IoSession session) {
				return decoder;
			}
		};
	}

	/**
	 * Creates a new instance of ProtocolCodecFilter, without any factory. The
	 * encoder/decoder factory will be created as an inner class, using the two
	 * parameters (encoder and decoder), which are class names. Instances for those
	 * classes will be created in this constructor.
	 * 
	 * @param encoderClass The class responsible for encoding the message
	 * @param decoderClass The class responsible for decoding the message
	 */
	public ProtocolCodecFilter(final Class<? extends ProtocolEncoder> encoderClass,
			final Class<? extends ProtocolDecoder> decoderClass) {
		if (encoderClass == null) {
			throw new IllegalArgumentException("encoderClass");
		}
		if (decoderClass == null) {
			throw new IllegalArgumentException("decoderClass");
		}
		if (!ProtocolEncoder.class.isAssignableFrom(encoderClass)) {
			throw new IllegalArgumentException("encoderClass: " + encoderClass.getName());
		}
		if (!ProtocolDecoder.class.isAssignableFrom(decoderClass)) {
			throw new IllegalArgumentException("decoderClass: " + decoderClass.getName());
		}
		try {
			encoderClass.getConstructor(EMPTY_PARAMS);
		} catch (NoSuchMethodException e) {
			throw new IllegalArgumentException("encoderClass doesn't have a public default constructor.");
		}
		try {
			decoderClass.getConstructor(EMPTY_PARAMS);
		} catch (NoSuchMethodException e) {
			throw new IllegalArgumentException("decoderClass doesn't have a public default constructor.");
		}

		final ProtocolEncoder encoder;

		try {
			encoder = encoderClass.newInstance();
		} catch (Exception e) {
			throw new IllegalArgumentException("encoderClass cannot be initialized");
		}

		final ProtocolDecoder decoder;

		try {
			decoder = decoderClass.newInstance();
		} catch (Exception e) {
			throw new IllegalArgumentException("decoderClass cannot be initialized");
		}

		// Create the inner factory based on the two parameters.
		this.factory = new ProtocolCodecFactory() {
			/**
			 * {@inheritDoc}
			 */
			@Override
			public ProtocolEncoder getEncoder(IoSession session) throws Exception {
				return encoder;
			}

			/**
			 * {@inheritDoc}
			 */
			@Override
			public ProtocolDecoder getDecoder(IoSession session) throws Exception {
				return decoder;
			}
		};
	}

	/**
	 * Get the encoder instance from a given session.
	 *
	 * @param session The associated session we will get the encoder from
	 * @return The encoder instance, if any
	 */
	public ProtocolEncoder getEncoder(IoSession session) {
		return (ProtocolEncoder) session.getAttribute(ENCODER);
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public void onPreAdd(IoFilterChain parent, String name, NextFilter nextFilter) throws Exception {
		if (parent.contains(this)) {
			throw new IllegalArgumentException(
					"You can't add the same filter instance more than once.  Create another instance and add it.");
		}
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public void onPostRemove(IoFilterChain parent, String name, NextFilter nextFilter) throws Exception {
		// Clean everything
		disposeCodec(parent.getSession());
	}

	/**
	 * Process the incoming message, calling the session decoder. As the incoming
	 * buffer might contains more than one messages, we have to loop until the
	 * decoder throws an exception.
	 * 
	 * while ( buffer not empty ) try decode ( buffer ) catch break;
	 * 
	 */
	@Override
	public void messageReceived(final NextFilter nextFilter, final IoSession session, final Object message)
			throws Exception {
		if (LOGGER.isDebugEnabled()) {
			LOGGER.debug("Processing a MESSAGE_RECEIVED for session {}", session.getId());
		}

		if (!(message instanceof IoBuffer)) {
			nextFilter.messageReceived(session, message);
			return;
		}

		final IoBuffer in = (IoBuffer) message;
		final ProtocolDecoder decoder = factory.getDecoder(session);
		final ProtocolDecoderOutputImpl decoderOut = DECODER_OUTPUT.get();

		// Loop until we don't have anymore byte in the buffer,
		// or until the decoder throws an unrecoverable exception or
		// can't decoder a message, because there are not enough
		// data in the buffer
		while (in.hasRemaining()) {
			int oldPos = in.position();
			try {
				// Call the decoder with the read bytes
				decoder.decode(session, in, decoderOut);
				// Finish decoding if no exception was thrown.
				decoderOut.flush(nextFilter, session);
			} catch (Exception e) {
				ProtocolDecoderException pde;
				if (e instanceof ProtocolDecoderException) {
					pde = (ProtocolDecoderException) e;
				} else {
					pde = new ProtocolDecoderException(e);
				}
				if (pde.getHexdump() == null) {
					// Generate a message hex dump
					int curPos = in.position();
					in.position(oldPos);
					pde.setHexdump(in.getHexDump());
					in.position(curPos);
				}
				// Fire the exceptionCaught event.
				decoderOut.flush(nextFilter, session);
				nextFilter.exceptionCaught(session, pde);
				// Retry only if the type of the caught exception is
				// recoverable and the buffer position has changed.
				// We check buffer position additionally to prevent an
				// infinite loop.
				if (!(e instanceof RecoverableProtocolDecoderException) || (in.position() == oldPos)) {
					break;
				}
			}
		}
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public void messageSent(NextFilter nextFilter, IoSession session, WriteRequest writeRequest) throws Exception {
		if (writeRequest instanceof EncodedWriteRequest) {
			return;
		}

		nextFilter.messageSent(session, writeRequest);
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public void filterWrite(final NextFilter nextFilter, final IoSession session, final WriteRequest writeRequest)
			throws Exception {
		final Object message = writeRequest.getMessage();

		// Bypass the encoding if the message is contained in a IoBuffer,
		// as it has already been encoded before
		if ((message instanceof IoBuffer) || (message instanceof FileRegion)) {
			nextFilter.filterWrite(session, writeRequest);
			return;
		}

		// Get the encoder in the session
		final ProtocolEncoder encoder = factory.getEncoder(session);
		final ProtocolEncoderOutputImpl encoderOut = ENCODER_OUTPUT.get();

		if (encoder == null) {
			throw new ProtocolEncoderException("The encoder is null for the session " + session);
		}

		try {
			// Now we can try to encode the response
			encoder.encode(session, message, encoderOut);

			final Queue<Object> queue = encoderOut.messageQueue;

			if (queue.isEmpty()) {
				// Write empty message to ensure that messageSent is fired later
				writeRequest.setMessage(EMPTY_BUFFER);
				nextFilter.filterWrite(session, writeRequest);
			} else {
				// Write all the encoded messages now
				Object encodedMessage = null;

				while ((encodedMessage = queue.poll()) != null) {
					if (queue.isEmpty()) {
						// Write last message using original WriteRequest to ensure that any Future and
						// dependency on messageSent event is emitted correctly
						writeRequest.setMessage(encodedMessage);
						nextFilter.filterWrite(session, writeRequest);
					} else {
						SocketAddress destination = writeRequest.getDestination();
						WriteRequest encodedWriteRequest = new EncodedWriteRequest(encodedMessage, null, destination);
						nextFilter.filterWrite(session, encodedWriteRequest);
					}
				}
			}
		} catch (final ProtocolEncoderException e) {
			throw e;
		} catch (final Exception e) {
			// Generate the correct exception
			throw new ProtocolEncoderException(e);
		}
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public void sessionClosed(NextFilter nextFilter, IoSession session) throws Exception {
		// Call finishDecode() first when a connection is closed.
		ProtocolDecoder decoder = factory.getDecoder(session);
		ProtocolDecoderOutput decoderOut = DECODER_OUTPUT.get();

		try {
			decoder.finishDecode(session, decoderOut);
		} catch (Exception e) {
			ProtocolDecoderException pde;
			if (e instanceof ProtocolDecoderException) {
				pde = (ProtocolDecoderException) e;
			} else {
				pde = new ProtocolDecoderException(e);
			}
			throw pde;
		} finally {
			// Dispose everything
			disposeCodec(session);
			decoderOut.flush(nextFilter, session);
		}

		// Call the next filter
		nextFilter.sessionClosed(session);
	}

	private static class EncodedWriteRequest extends DefaultWriteRequest {
		public EncodedWriteRequest(Object encodedMessage, WriteFuture future, SocketAddress destination) {
			super(encodedMessage, future, destination);
		}

		/**
		 * {@inheritDoc}
		 */
		@Override
		public boolean isEncoded() {
			return true;
		}
	}

	private static class ProtocolDecoderOutputImpl extends AbstractProtocolDecoderOutput {
		public ProtocolDecoderOutputImpl() {
			// Do nothing
		}
	}

	private static class ProtocolEncoderOutputImpl extends AbstractProtocolEncoderOutput {
		public ProtocolEncoderOutputImpl() {
			// Do nothing
		}
	}

	// ----------- Helper methods ---------------------------------------------
	/**
	 * Dispose the encoder, decoder, and the callback for the decoded messages.
	 */
	private void disposeCodec(IoSession session) {
		// We just remove the two instances of encoder/decoder to release resources
		// from the session
		disposeEncoder(session);
		disposeDecoder(session);
	}

	/**
	 * Dispose the encoder, removing its instance from the session's attributes, and
	 * calling the associated dispose method.
	 */
	private void disposeEncoder(IoSession session) {
		ProtocolEncoder encoder = (ProtocolEncoder) session.removeAttribute(ENCODER);
		if (encoder == null) {
			return;
		}

		try {
			encoder.dispose(session);
		} catch (Exception e) {
			LOGGER.warn("Failed to dispose: " + encoder.getClass().getName() + " (" + encoder + ')');
		}
	}

	/**
	 * Dispose the decoder, removing its instance from the session's attributes, and
	 * calling the associated dispose method.
	 */
	private void disposeDecoder(IoSession session) {
		ProtocolDecoder decoder = (ProtocolDecoder) session.removeAttribute(DECODER);
		if (decoder == null) {
			return;
		}

		try {
			decoder.dispose(session);
		} catch (Exception e) {
			LOGGER.warn("Failed to dispose: " + decoder.getClass().getName() + " (" + decoder + ')');
		}
	}

	static private class ProtocolDecoderOutputLocal extends ThreadLocal<ProtocolDecoderOutputImpl> {
		@Override
		protected ProtocolDecoderOutputImpl initialValue() {
			return new ProtocolDecoderOutputImpl();
		}
	}

	static private class ProtocolEncoderOutputLocal extends ThreadLocal<ProtocolEncoderOutputImpl> {
		@Override
		protected ProtocolEncoderOutputImpl initialValue() {
			return new ProtocolEncoderOutputImpl();
		}
	}
}