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   /*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project 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.jboss.netty.example.factorial;
  
  import org.jboss.netty.channel.Channel;
  import org.jboss.netty.channel.ChannelEvent;
  import org.jboss.netty.channel.ChannelFuture;
  import org.jboss.netty.channel.ChannelFutureListener;
  import org.jboss.netty.channel.ChannelHandlerContext;
  import org.jboss.netty.channel.ChannelStateEvent;
  import org.jboss.netty.channel.ExceptionEvent;
  import org.jboss.netty.channel.MessageEvent;
  import org.jboss.netty.channel.SimpleChannelUpstreamHandler;
  
  import java.math.BigInteger;
  import java.util.concurrent.BlockingQueue;
  import java.util.concurrent.LinkedBlockingQueue;
  
  /**
   * Handler for a client-side channel.  This handler maintains stateful
   * information which is specific to a certain channel using member variables.
   * Therefore, an instance of this handler can cover only one channel.  You have
   * to create a new handler instance whenever you create a new channel and insert
   * this handler to avoid a race condition.
   */
  public class FactorialClientHandler extends SimpleChannelUpstreamHandler {
  
      // Stateful properties
      private int i = 1;
      private int receivedMessages;
      final BlockingQueue<BigInteger> answer = new LinkedBlockingQueue<BigInteger>();
  
      public BigInteger getFactorial() {
          boolean interrupted = false;
          try {
              for (;;) {
                  try {
                      return answer.take();
                  } catch (InterruptedException ignore) {
                      interrupted = true;
                  }
              }
          } finally {
              if (interrupted) {
                  Thread.currentThread().interrupt();
              }
          }
      }
  
      @Override
      public void handleUpstream(ChannelHandlerContext ctx, ChannelEvent e) throws Exception {
          if (e instanceof ChannelStateEvent) {
              System.err.println(e);
          }
          super.handleUpstream(ctx, e);
      }
  
      @Override
      public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e) {
          sendNumbers(e);
      }
  
      @Override
      public void channelInterestChanged(ChannelHandlerContext ctx, ChannelStateEvent e) {
          sendNumbers(e);
      }
  
      @Override
      public void messageReceived(
              ChannelHandlerContext ctx, final MessageEvent e) {
          receivedMessages ++;
          if (receivedMessages == FactorialClient.COUNT) {
              // Offer the answer after closing the connection.
              e.getChannel().close().addListener(new ChannelFutureListener() {
                  public void operationComplete(ChannelFuture future) {
                      boolean offered = answer.offer((BigInteger) e.getMessage());
                      assert offered;
                  }
              });
          }
      }
  
      @Override
      public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) {
          e.getCause().printStackTrace();
          e.getChannel().close();
     }
 
     private void sendNumbers(ChannelStateEvent e) {
         Channel channel = e.getChannel();
         while (channel.isWritable()) {
             if (i <= FactorialClient.COUNT) {
                 channel.write(i);
                 i ++;
             } else {
                 break;
             }
         }
     }
 }