/*
    * Copyright 2009 Red Hat, Inc.
    *
    * Red Hat 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 java.math.BigInteger;
  import java.util.Formatter;
  import java.util.logging.Level;
  import java.util.logging.Logger;
  
  import org.jboss.netty.channel.ChannelEvent;
  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;
  
  /**
   * Handler for a server-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.
   *
   * @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
   * @author <a href="http://gleamynode.net/">Trustin Lee</a>
   *
   * @version $Rev: 2121 $, $Date: 2010-02-02 09:38:07 +0900 (Tue, 02 Feb 2010) $
   */
  public class FactorialServerHandler extends SimpleChannelUpstreamHandler {
  
      private static final Logger logger = Logger.getLogger(
              FactorialServerHandler.class.getName());
  
      // Stateful properties.
      private int lastMultiplier = 1;
      private BigInteger factorial = new BigInteger(new byte[] { 1 });
  
      @Override
      public void handleUpstream(
              ChannelHandlerContext ctx, ChannelEvent e) throws Exception {
          if (e instanceof ChannelStateEvent) {
              logger.info(e.toString());
          }
          super.handleUpstream(ctx, e);
      }
  
      @Override
      public void messageReceived(
              ChannelHandlerContext ctx, MessageEvent e) {
  
          // Calculate the cumulative factorial and send it to the client.
          BigInteger number;
          if (e.getMessage() instanceof BigInteger) {
              number = (BigInteger) e.getMessage();
          } else {
              number = new BigInteger(e.getMessage().toString());
          }
          lastMultiplier = number.intValue();
          factorial = factorial.multiply(number);
          e.getChannel().write(factorial);
      }
  
      @Override
      public void channelDisconnected(ChannelHandlerContext ctx,
              ChannelStateEvent e) throws Exception {
          logger.info(new Formatter().format(
                  "Factorial of %,d is: %,d", lastMultiplier, factorial).toString());
      }
  
      @Override
      public void exceptionCaught(
              ChannelHandlerContext ctx, ExceptionEvent e) {
          logger.log(
                  Level.WARNING,
                  "Unexpected exception from downstream.",
                  e.getCause());
          e.getChannel().close();
      }
  }