/*
    * 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.handler.timeout;
  
  import org.jboss.netty.bootstrap.ServerBootstrap;
  import org.jboss.netty.channel.ChannelFuture;
  import org.jboss.netty.channel.ChannelFutureListener;
  import org.jboss.netty.channel.ChannelHandler.Sharable;
  import org.jboss.netty.channel.ChannelHandlerContext;
  import org.jboss.netty.channel.ChannelPipeline;
  import org.jboss.netty.channel.ChannelPipelineFactory;
  import org.jboss.netty.channel.Channels;
  import org.jboss.netty.channel.MessageEvent;
  import org.jboss.netty.channel.SimpleChannelDownstreamHandler;
  import org.jboss.netty.util.ExternalResourceReleasable;
  import org.jboss.netty.util.HashedWheelTimer;
  import org.jboss.netty.util.Timeout;
  import org.jboss.netty.util.Timer;
  import org.jboss.netty.util.TimerTask;
  
  import java.util.concurrent.TimeUnit;
  
  import static org.jboss.netty.channel.Channels.*;
  
  /**
   * Raises a {@link WriteTimeoutException} when no data was written within a
   * certain period of time.
   *
   * <pre>
   * public class MyPipelineFactory implements {@link ChannelPipelineFactory} {
   *
   *     private final {@link Timer} timer;
   *
   *     public MyPipelineFactory({@link Timer} timer) {
   *         this.timer = timer;
   *     }
   *
   *     public {@link ChannelPipeline} getPipeline() {
   *         // An example configuration that implements 30-second write timeout:
   *         return {@link Channels}.pipeline(
   *             <b>new {@link WriteTimeoutHandler}(timer, 30), // timer must be shared.</b>
   *             new MyHandler());
   *     }
   * }
   *
   * {@link ServerBootstrap} bootstrap = ...;
   * {@link Timer} timer = new {@link HashedWheelTimer}();
   * ...
   * bootstrap.setPipelineFactory(new MyPipelineFactory(timer));
   * </pre>
   *
   * The {@link Timer} which was specified when the {@link ReadTimeoutHandler} is
   * created should be stopped manually by calling {@link #releaseExternalResources()}
   * or {@link Timer#stop()} when your application shuts down.
   * @see ReadTimeoutHandler
   * @see IdleStateHandler
   *
   * @apiviz.landmark
   * @apiviz.uses org.jboss.netty.util.HashedWheelTimer
   * @apiviz.has org.jboss.netty.handler.timeout.TimeoutException oneway - - raises
   */
  @Sharable
  public class WriteTimeoutHandler extends SimpleChannelDownstreamHandler
                                   implements ExternalResourceReleasable {
  
      static final WriteTimeoutException EXCEPTION = new WriteTimeoutException();
  
      private final Timer timer;
      private final long timeoutMillis;
  
      /**
       * Creates a new instance.
       *
       * @param timer
       *        the {@link Timer} that is used to trigger the scheduled event.
       *        The recommended {@link Timer} implementation is {@link HashedWheelTimer}.
       * @param timeoutSeconds
       *        write timeout in seconds
       */
      public WriteTimeoutHandler(Timer timer, int timeoutSeconds) {
          this(timer, timeoutSeconds, TimeUnit.SECONDS);
      }
  
      /**
       * Creates a new instance.
       *
      * @param timer
      *        the {@link Timer} that is used to trigger the scheduled event.
      *        The recommended {@link Timer} implementation is {@link HashedWheelTimer}.
      * @param timeout
      *        write timeout
      * @param unit
      *        the {@link TimeUnit} of {@code timeout}
      */
     public WriteTimeoutHandler(Timer timer, long timeout, TimeUnit unit) {
         if (timer == null) {
             throw new NullPointerException("timer");
         }
         if (unit == null) {
             throw new NullPointerException("unit");
         }
 
         this.timer = timer;
         if (timeout <= 0) {
             timeoutMillis = 0;
         } else {
             timeoutMillis = Math.max(unit.toMillis(timeout), 1);
         }
     }
 
     /**
      * Stops the {@link Timer} which was specified in the constructor of this
      * handler.  You should not call this method if the {@link Timer} is in use
      * by other objects.
      */
     public void releaseExternalResources() {
         timer.stop();
     }
 
     /**
      * Returns the write timeout of the specified event.  By default, this method returns the
      * timeout value you specified in the constructor.  Override this method to determine the
      * timeout value depending on the message being written.
      *
      * @param e the message being written
      */
     protected long getTimeoutMillis(MessageEvent e) {
         return timeoutMillis;
     }
 
     @Override
     public void writeRequested(ChannelHandlerContext ctx, MessageEvent e)
             throws Exception {
 
         long timeoutMillis = getTimeoutMillis(e);
         if (timeoutMillis > 0) {
             // Set timeout only when getTimeoutMillis() returns a positive value.
             ChannelFuture future = e.getFuture();
             final Timeout timeout = timer.newTimeout(
                     new WriteTimeoutTask(ctx, future),
                     timeoutMillis, TimeUnit.MILLISECONDS);
 
             future.addListener(new TimeoutCanceller(timeout));
         }
 
         super.writeRequested(ctx, e);
     }
 
     protected void writeTimedOut(ChannelHandlerContext ctx) throws Exception {
        fireExceptionCaught(ctx, EXCEPTION);
     }
 
     private final class WriteTimeoutTask implements TimerTask {
 
         private final ChannelHandlerContext ctx;
         private final ChannelFuture future;
 
         WriteTimeoutTask(ChannelHandlerContext ctx, ChannelFuture future) {
             this.ctx = ctx;
             this.future = future;
         }
 
         public void run(Timeout timeout) throws Exception {
             if (timeout.isCancelled()) {
                 return;
             }
 
             if (!ctx.getChannel().isOpen()) {
                 return;
             }
 
             // Mark the future as failure
             if (future.setFailure(EXCEPTION)) {
                 // If succeeded to mark as failure, notify the pipeline, too.
                 fireWriteTimeOut(ctx);
             }
         }
 
         private void fireWriteTimeOut(final ChannelHandlerContext ctx) {
             ctx.getPipeline().execute(new Runnable() {
 
                 public void run() {
                     try {
                         writeTimedOut(ctx);
                     } catch (Throwable t) {
                         fireExceptionCaught(ctx, t);
                     }
                 }
             });
         }
     }
 
     private static final class TimeoutCanceller implements ChannelFutureListener {
         private final Timeout timeout;
 
         TimeoutCanceller(Timeout timeout) {
             this.timeout = timeout;
         }
 
         public void operationComplete(ChannelFuture future) throws Exception {
             timeout.cancel();
         }
     }
 }