/*

  * 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.giraph.comm;

 import org.apache.hadoop.conf.Configuration;

 import org.apache.hadoop.io.Writable;

 import org.apache.hadoop.io.WritableComparable;

 import org.apache.hadoop.util.ReflectionUtils;

 import org.apache.log4j.Logger;

 import org.jboss.netty.buffer.ChannelBuffer;

 import org.jboss.netty.buffer.ChannelBufferInputStream;

 import org.jboss.netty.channel.Channel;

 import org.jboss.netty.channel.ChannelHandlerContext;

 import org.jboss.netty.handler.codec.oneone.OneToOneDecoder;

 /**

  * Decodes encoded requests from the client.

  *

  * @param <I> Vertex id

  * @param <V> Vertex data

  * @param <E> Edge data

  * @param <M> Message data

  */

 @SuppressWarnings("rawtypes")

 public class RequestDecoder<I extends WritableComparable,

     V extends Writable, E extends Writable,

     M extends Writable>  extends OneToOneDecoder {

   /** Class logger */

   private static final Logger LOG =

       Logger.getLogger(RequestDecoder.class);

   /** Configuration */

   private final Configuration conf;

   /** Registry of requests */

   private final RequestRegistry requestRegistry;

   /** Byte counter to output */

   private final ByteCounter byteCounter;

   /**

    * Constructor.

    *

    * @param conf Configuration

    * @param requestRegistry Request registry

    * @param byteCounter Keeps track of the decoded bytes

    */

   public RequestDecoder(Configuration conf, RequestRegistry requestRegistry,

                         ByteCounter byteCounter) {

     this.conf = conf;

     this.requestRegistry = requestRegistry;

     this.byteCounter = byteCounter;

   }

   @Override

   protected Object decode(ChannelHandlerContext ctx,

       Channel channel, Object msg) throws Exception {

     if (!(msg instanceof ChannelBuffer)) {

       throw new IllegalStateException("decode: Got illegal message " + msg);

     }

     // Output metrics every 1/2 minute

     String metrics = byteCounter.getMetricsWindow(30000);

     if (metrics != null) {

       if (LOG.isInfoEnabled()) {

         LOG.info("decode: Server window metrics " + metrics);

       }

     }

     ChannelBuffer buffer = (ChannelBuffer) msg;

     ChannelBufferInputStream inputStream = new ChannelBufferInputStream(buffer);

     int enumValue = inputStream.readByte();

     RequestRegistry.Type type = RequestRegistry.Type.values()[enumValue];

     if (LOG.isDebugEnabled()) {

       LOG.debug("decode: Got a request of type " + type);

     }

     @SuppressWarnings("unchecked")

     Class<? extends WritableRequest<I, V, E, M>> writableRequestClass =

         (Class<? extends WritableRequest<I, V, E, M>>)

         requestRegistry.getClass(type);

     WritableRequest<I, V, E, M> writableRequest =

         ReflectionUtils.newInstance(writableRequestClass, conf);

     writableRequest.readFields(inputStream);

     return writableRequest;

   }

 }