/*
 *  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.DefaultWriteFuture;
import org.apache.mina.core.future.WriteFuture;
import org.apache.mina.core.session.AbstractIoSession;
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.NothingWrittenException;
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 AttributeKey DECODER_OUT = new AttributeKey(ProtocolCodecFilter.class, "decoderOut");

    private static final AttributeKey ENCODER_OUT = new AttributeKey(ProtocolCodecFilter.class, "encoderOut");

    /** 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(NextFilter nextFilter, IoSession session, 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;
        }

        IoBuffer in = (IoBuffer) message;
        ProtocolDecoder decoder = factory.getDecoder(session);
        ProtocolDecoderOutput decoderOut = getDecoderOut(session, nextFilter);

        // 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 {
                synchronized (session) {
                    // 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(NextFilter nextFilter, IoSession session, WriteRequest writeRequest) throws Exception {
        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
        ProtocolEncoder encoder = factory.getEncoder(session);

        ProtocolEncoderOutput encoderOut = getEncoderOut(session, nextFilter, writeRequest);

        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);

            // Send it directly
            Queue<Object> bufferQueue = ((AbstractProtocolEncoderOutput) encoderOut).getMessageQueue();

            // Write all the encoded messages now
            while (!bufferQueue.isEmpty()) {
                Object encodedMessage = bufferQueue.poll();

                if (encodedMessage == null) {
                    break;
                }

		// Flush only when the buffer has remaining.
		if (!(encodedMessage instanceof IoBuffer) || ((IoBuffer) encodedMessage).hasRemaining()) {
		    if (bufferQueue.isEmpty()) {
			writeRequest.setMessage(encodedMessage);
			nextFilter.filterWrite(session, writeRequest);
		    } else {
			SocketAddress destination = writeRequest.getDestination();
			WriteRequest encodedWriteRequest = new EncodedWriteRequest(encodedMessage, null, destination);
			nextFilter.filterWrite(session, encodedWriteRequest);
		    }
		}
	    }
        } catch (Exception e) {
            ProtocolEncoderException pee;

            // Generate the correct exception
            if (e instanceof ProtocolEncoderException) {
                pee = (ProtocolEncoderException) e;
            } else {
                pee = new ProtocolEncoderException(e);
            }

            throw pee;
        }
    }

    /**
     * {@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 = getDecoderOut(session, nextFilter);

        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
        }

        /**
         * {@inheritDoc}
         */
        @Override
        public void flush(NextFilter nextFilter, IoSession session) {
            Queue<Object> messageQueue = getMessageQueue();

            while (!messageQueue.isEmpty()) {
                nextFilter.messageReceived(session, messageQueue.poll());
            }
        }
    }

    private static class ProtocolEncoderOutputImpl extends AbstractProtocolEncoderOutput {
        private final IoSession session;

        private final NextFilter nextFilter;

        /** The WriteRequest destination */
        private final SocketAddress destination;

        public ProtocolEncoderOutputImpl(IoSession session, NextFilter nextFilter, WriteRequest writeRequest) {
            this.session = session;
            this.nextFilter = nextFilter;

            // Only store the destination, not the full WriteRequest.
            destination = writeRequest.getDestination();
        }

        /**
         * {@inheritDoc}
         */
        @Override
        public WriteFuture flush() {
            Queue<Object> bufferQueue = getMessageQueue();
            WriteFuture future = null;

            while (!bufferQueue.isEmpty()) {
                Object encodedMessage = bufferQueue.poll();

                if (encodedMessage == null) {
                    break;
                }

                // Flush only when the buffer has remaining.
                if (!(encodedMessage instanceof IoBuffer) || ((IoBuffer) encodedMessage).hasRemaining()) {
                    future = new DefaultWriteFuture(session);
                    nextFilter.filterWrite(session, new EncodedWriteRequest(encodedMessage, future, destination));
                }
            }

            if (future == null) {
                // Creates an empty writeRequest containing the destination
                future = DefaultWriteFuture.newNotWrittenFuture(session, new NothingWrittenException(AbstractIoSession.MESSAGE_SENT_REQUEST));
            }

            return future;
        }
    }

    //----------- 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);

        // We also remove the callback
        disposeDecoderOut(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 + ')');
        }
    }

    /**
     * Return a reference to the decoder callback. If it's not already created
     * and stored into the session, we create a new instance.
     */
    private ProtocolDecoderOutput getDecoderOut(IoSession session, NextFilter nextFilter) {
        ProtocolDecoderOutput out = (ProtocolDecoderOutput) session.getAttribute(DECODER_OUT);

        if (out == null) {
            // Create a new instance, and stores it into the session
            out = new ProtocolDecoderOutputImpl();
            session.setAttribute(DECODER_OUT, out);
        }

        return out;
    }

    private ProtocolEncoderOutput getEncoderOut(IoSession session, NextFilter nextFilter, WriteRequest writeRequest) {
        ProtocolEncoderOutput out = (ProtocolEncoderOutput) session.getAttribute(ENCODER_OUT);

        if (out == null) {
            // Create a new instance, and stores it into the session
            out = new ProtocolEncoderOutputImpl(session, nextFilter, writeRequest);
            session.setAttribute(ENCODER_OUT, out);
        }

        return out;
    }

    /**
     * Remove the decoder callback from the session's attributes.
     */
    private void disposeDecoderOut(IoSession session) {
        session.removeAttribute(DECODER_OUT);
    }
}