/*
    * 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.netty.handler;
  
  import org.apache.giraph.conf.ImmutableClassesGiraphConfiguration;
  import org.apache.giraph.comm.netty.InboundByteCounter;
  import org.apache.giraph.comm.requests.RequestType;
  import org.apache.giraph.comm.requests.WritableRequest;
  import org.apache.giraph.time.SystemTime;
  import org.apache.giraph.time.Time;
  import org.apache.giraph.time.Times;
  import org.apache.giraph.utils.ReflectionUtils;
  import org.apache.giraph.utils.RequestUtils;
  import org.apache.log4j.Logger;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelInboundHandlerAdapter;
  import io.netty.util.ReferenceCountUtil;
  
  /**
   * Decodes encoded requests from the client.
   */
  public class RequestDecoder extends ChannelInboundHandlerAdapter {
    /** Class logger */
    private static final Logger LOG =
        Logger.getLogger(RequestDecoder.class);
    /** Time class to use */
    private static final Time TIME = SystemTime.get();
    /** Configuration */
    private final ImmutableClassesGiraphConfiguration conf;
    /** In bound byte counter to output */
    private final InboundByteCounter byteCounter;
    /** Start nanoseconds for the decoding time */
    private long startDecodingNanoseconds = -1;
    /**
     * Constructor.
     *
     * @param conf Configuration
     * @param byteCounter Keeps track of the decoded bytes
     */
    public RequestDecoder(ImmutableClassesGiraphConfiguration conf,
      InboundByteCounter byteCounter) {
      this.conf = conf;
      this.byteCounter = byteCounter;
    }
  
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg)
      throws Exception {
      if (!(msg instanceof ByteBuf)) {
        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);
        }
      }
  
      if (LOG.isDebugEnabled()) {
        startDecodingNanoseconds = TIME.getNanoseconds();
      }
  
      // Decode the request
      ByteBuf buf = (ByteBuf) msg;
      int enumValue = buf.readByte();
      RequestType type = RequestType.values()[enumValue];
      Class<? extends WritableRequest> requestClass = type.getRequestClass();
      WritableRequest request =
          ReflectionUtils.newInstance(requestClass, conf);
      request = RequestUtils.decodeWritableRequest(buf, request);
  
      if (LOG.isDebugEnabled()) {
        LOG.debug("decode: Client " + request.getClientId() +
            ", requestId " + request.getRequestId() +
            ", " +  request.getType() + ", with size " +
            buf.writerIndex() + " took " +
            Times.getNanosSince(TIME, startDecodingNanoseconds) + " ns");
      }
      ReferenceCountUtil.release(buf);
      // fire writableRequest object to upstream handlers
     ctx.fireChannelRead(request);
   }
 }