/*
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    *  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.mina.filter.executor;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.EnumSet;
  import java.util.concurrent.Executor;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Executors;
  import java.util.concurrent.ThreadFactory;
  import java.util.concurrent.TimeUnit;
  
  import org.apache.mina.core.filterchain.IoFilterAdapter;
  import org.apache.mina.core.filterchain.IoFilterChain;
  import org.apache.mina.core.filterchain.IoFilterEvent;
  import org.apache.mina.core.session.IdleStatus;
  import org.apache.mina.core.session.IoEventType;
  import org.apache.mina.core.session.IoSession;
  import org.apache.mina.core.write.WriteRequest;
  
  /**
   * A filter that forwards I/O events to {@link Executor} to enforce a certain
   * thread model while allowing the events per session to be processed
   * simultaneously. You can apply various thread model by inserting this filter
   * to a {@link IoFilterChain}.
   * 
   * <h2>Life Cycle Management</h2>
   * 
   * Please note that this filter doesn't manage the life cycle of the {@link Executor}.
   * If you created this filter using {@link #ExecutorFilter(Executor)} or similar
   * constructor that accepts an {@link Executor} that you've instantiated, you have
   * full control and responsibility of managing its life cycle (e.g. calling
   * {@link ExecutorService#shutdown()}.
   * <p> 
   * If you created this filter using convenience constructors like
   * {@link #ExecutorFilter(int)}, then you can shut down the executor by calling
   * {@link #destroy()} explicitly.
   * 
   * <h2>Event Ordering</h2>
   * 
   * All convenience constructors of this filter creates a new
   * {@link OrderedThreadPoolExecutor} instance.  Therefore, the order of event is
   * maintained like the following:
   * <ul>
   * <li>All event handler methods are called exclusively.
   *     (e.g. messageReceived and messageSent can't be invoked at the same time.)</li>
   * <li>The event order is never mixed up.
   *     (e.g. messageReceived is always invoked before sessionClosed or messageSent.)</li>
   * </ul>
   * However, if you specified other {@link Executor} instance in the constructor,
   * the order of events are not maintained at all.  This means more than one event
   * handler methods can be invoked at the same time with mixed order.  For example,
   * let's assume that messageReceived, messageSent, and sessionClosed events are
   * fired.
   * <ul>
   * <li>All event handler methods can be called simultaneously.
   *     (e.g. messageReceived and messageSent can be invoked at the same time.)</li>
   * <li>The event order can be mixed up.
   *     (e.g. sessionClosed or messageSent can be invoked before messageReceived
   *           is invoked.)</li>
   * </ul>
   * If you need to maintain the order of events per session, please specify an
   * {@link OrderedThreadPoolExecutor} instance or use the convenience constructors.
   * 
   * <h2>Selective Filtering</h2>
   * 
   * By default, all event types but <tt>sessionCreated</tt>, <tt>filterWrite</tt>,
   * <tt>filterClose</tt> and <tt>filterSetTrafficMask</tt> are submitted to the
   * underlying executor, which is most common setting.
   * <p>
   * If you want to submit only a certain set of event types, you can specify them
   * in the constructor.  For example, you could configure a thread pool for
   * write operation for the maximum performance:
   * <pre><code>
   * IoService service = ...;
   * DefaultIoFilterChainBuilder chain = service.getFilterChain();
   * 
   * chain.addLast("codec", new ProtocolCodecFilter(...));
   * // Use one thread pool for most events.
   * chain.addLast("executor1", new ExecutorFilter());
  * // and another dedicated thread pool for 'filterWrite' events.
  * chain.addLast("executor2", new ExecutorFilter(IoEventType.WRITE));
  * </code></pre>
  * 
  * <h2>Preventing {@link OutOfMemoryError}</h2>
  * 
  * Please refer to {@link IoEventQueueThrottle}, which is specified as
  * a parameter of the convenience constructors.
  * 
  * @author The Apache MINA Project (dev@mina.apache.org)
  * @version $Rev: 671827 $, $Date: 2008-06-26 10:49:48 +0200 (jeu, 26 jun 2008) $
  * 
  * @see OrderedThreadPoolExecutor
  * @see UnorderedThreadPoolExecutor
  */
 public class ExecutorFilter extends IoFilterAdapter {
 
     private final EnumSet<IoEventType> eventTypes;
     private final Executor executor;
     private final boolean createdExecutor;
 
     /**
      * (Convenience constructor) Creates a new instance with a new
      * {@link OrderedThreadPoolExecutor}.
      */
     public ExecutorFilter() {
         this(16, (IoEventType[]) null);
     }
     
     /**
      * (Convenience constructor) Creates a new instance with a new
      * {@link OrderedThreadPoolExecutor}.
      */
     public ExecutorFilter(int maximumPoolSize) {
         this(0, maximumPoolSize, (IoEventType[]) null);
     }
     
     /**
      * (Convenience constructor) Creates a new instance with a new
      * {@link OrderedThreadPoolExecutor}.
      */
     public ExecutorFilter(int corePoolSize, int maximumPoolSize) {
         this(corePoolSize, maximumPoolSize, 30, TimeUnit.SECONDS, (IoEventType[]) null);
     }
     
     /**
      * (Convenience constructor) Creates a new instance with a new
      * {@link OrderedThreadPoolExecutor}.
      */
     public ExecutorFilter(
             int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit) {
         this(corePoolSize, maximumPoolSize, keepAliveTime, unit, (IoEventType[]) null);
     }
 
     /**
      * (Convenience constructor) Creates a new instance with a new
      * {@link OrderedThreadPoolExecutor}.
      */
     public ExecutorFilter(
             int corePoolSize, int maximumPoolSize, 
             long keepAliveTime, TimeUnit unit,
             IoEventQueueHandler queueHandler) {
         this(corePoolSize, maximumPoolSize, keepAliveTime, unit, Executors.defaultThreadFactory(), queueHandler, (IoEventType[]) null);
     }
 
     /**
      * (Convenience constructor) Creates a new instance with a new
      * {@link OrderedThreadPoolExecutor}.
      */
     public ExecutorFilter(
             int corePoolSize, int maximumPoolSize, 
             long keepAliveTime, TimeUnit unit,
             ThreadFactory threadFactory) {
         this(corePoolSize, maximumPoolSize, keepAliveTime, unit, threadFactory, null, (IoEventType[]) null);
     }
 
     /**
      * (Convenience constructor) Creates a new instance with a new
      * {@link OrderedThreadPoolExecutor}.
      */
     public ExecutorFilter(
             int corePoolSize, int maximumPoolSize, 
             long keepAliveTime, TimeUnit unit,
             ThreadFactory threadFactory, IoEventQueueHandler queueHandler) {
         this(new OrderedThreadPoolExecutor(corePoolSize, maximumPoolSize, keepAliveTime, unit, threadFactory, queueHandler), true, (IoEventType[]) null);
     }
 
     /**
      * (Convenience constructor) Creates a new instance with a new
      * {@link OrderedThreadPoolExecutor}.
      */
     public ExecutorFilter(IoEventType... eventTypes) {
         this(16, eventTypes);
     }
     
     /**
      * (Convenience constructor) Creates a new instance with a new
      * {@link OrderedThreadPoolExecutor}.
      */
     public ExecutorFilter(int maximumPoolSize, IoEventType... eventTypes) {
         this(0, maximumPoolSize, eventTypes);
     }
     
     /**
      * (Convenience constructor) Creates a new instance with a new
      * {@link OrderedThreadPoolExecutor}.
      */
     public ExecutorFilter(int corePoolSize, int maximumPoolSize, IoEventType... eventTypes) {
         this(corePoolSize, maximumPoolSize, 30, TimeUnit.SECONDS, eventTypes);
     }
     
     /**
      * (Convenience constructor) Creates a new instance with a new
      * {@link OrderedThreadPoolExecutor}.
      */
     public ExecutorFilter(
             int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, IoEventType... eventTypes) {
         this(corePoolSize, maximumPoolSize, keepAliveTime, unit, Executors.defaultThreadFactory(), eventTypes);
     }
     
     /**
      * (Convenience constructor) Creates a new instance with a new
      * {@link OrderedThreadPoolExecutor}.
      */
     public ExecutorFilter(
             int corePoolSize, int maximumPoolSize, 
             long keepAliveTime, TimeUnit unit,
             IoEventQueueHandler queueHandler, IoEventType... eventTypes) {
         this(corePoolSize, maximumPoolSize, keepAliveTime, unit, Executors.defaultThreadFactory(), queueHandler, eventTypes);
     }
 
     /**
      * (Convenience constructor) Creates a new instance with a new
      * {@link OrderedThreadPoolExecutor}.
      */
     public ExecutorFilter(
             int corePoolSize, int maximumPoolSize, 
             long keepAliveTime, TimeUnit unit,
             ThreadFactory threadFactory, IoEventType... eventTypes) {
         this(corePoolSize, maximumPoolSize, keepAliveTime, unit, threadFactory, null, eventTypes);
     }
 
     /**
      * (Convenience constructor) Creates a new instance with a new
      * {@link OrderedThreadPoolExecutor}.
      */
     public ExecutorFilter(
             int corePoolSize, int maximumPoolSize, 
             long keepAliveTime, TimeUnit unit,
             ThreadFactory threadFactory, IoEventQueueHandler queueHandler, IoEventType... eventTypes) {
         this(new OrderedThreadPoolExecutor(corePoolSize, maximumPoolSize, keepAliveTime, unit, threadFactory, queueHandler), true, eventTypes);
     }
     
     /**
      * Creates a new instance with the specified {@link Executor}.
      */
     public ExecutorFilter(Executor executor) {
         this(executor, false, (IoEventType[]) null);
     }
 
     /**
      * Creates a new instance with the specified {@link Executor}.
      */
     public ExecutorFilter(Executor executor, IoEventType... eventTypes) {
         this(executor, false, eventTypes);
     }
 
     private ExecutorFilter(Executor executor, boolean createdExecutor, IoEventType... eventTypes) {
         if (executor == null) {
             throw new NullPointerException("executor");
         }
         if (eventTypes == null || eventTypes.length == 0) {
             eventTypes = new IoEventType[] { IoEventType.EXCEPTION_CAUGHT,
                     IoEventType.MESSAGE_RECEIVED, IoEventType.MESSAGE_SENT,
                     IoEventType.SESSION_CLOSED, IoEventType.SESSION_IDLE,
                     IoEventType.SESSION_OPENED, };
         }
 
         for (IoEventType t : eventTypes) {
             if (t == IoEventType.SESSION_CREATED) {
                 throw new IllegalArgumentException(IoEventType.SESSION_CREATED
                         + " is not allowed.");
             }
         }
 
         this.executor = executor;
         this.createdExecutor = createdExecutor;
 
         Collection<IoEventType> eventTypeCollection = new ArrayList<IoEventType>(
                 eventTypes.length);
         Collections.addAll(eventTypeCollection, eventTypes);
         this.eventTypes = EnumSet.copyOf(eventTypeCollection);
     }
     
     /**
      * Shuts down the underlying executor if this filter is creates via
      * a convenience constructor.
      */
     @Override
     public void destroy() {
         if (createdExecutor) {
             ((ExecutorService) executor).shutdown();
         }
     }
 
     /**
      * Returns the underlying {@link Executor} instance this filter uses.
      */
     public final Executor getExecutor() {
         return executor;
     }
 
     /**
      * Fires the specified event through the underlying executor.
      */
     protected void fireEvent(IoFilterEvent event) {
         getExecutor().execute(event);
     }
 
     @Override
     public void onPreAdd(IoFilterChain parent, String name,
             NextFilter nextFilter) throws Exception {
         if (parent.contains(this)) {
             throw new IllegalArgumentException(
                     "You can't add the same filter instance more than once.  Create another instance and add it.");
         }
     }
 
     @Override
     public final void sessionCreated(NextFilter nextFilter, IoSession session) {
         nextFilter.sessionCreated(session);
     }
 
     @Override
     public final void sessionOpened(NextFilter nextFilter, IoSession session) {
         if (eventTypes.contains(IoEventType.SESSION_OPENED)) {
             fireEvent(new IoFilterEvent(nextFilter, IoEventType.SESSION_OPENED,
                     session, null));
         } else {
             nextFilter.sessionOpened(session);
         }
     }
 
     @Override
     public final void sessionClosed(NextFilter nextFilter, IoSession session) {
         if (eventTypes.contains(IoEventType.SESSION_CLOSED)) {
             fireEvent(new IoFilterEvent(nextFilter, IoEventType.SESSION_CLOSED,
                     session, null));
         } else {
             nextFilter.sessionClosed(session);
         }
     }
 
     @Override
     public final void sessionIdle(NextFilter nextFilter, IoSession session,
             IdleStatus status) {
         if (eventTypes.contains(IoEventType.SESSION_IDLE)) {
             fireEvent(new IoFilterEvent(nextFilter, IoEventType.SESSION_IDLE,
                     session, status));
         } else {
             nextFilter.sessionIdle(session, status);
         }
     }
 
     @Override
     public final void exceptionCaught(NextFilter nextFilter, IoSession session,
             Throwable cause) {
         if (eventTypes.contains(IoEventType.EXCEPTION_CAUGHT)) {
             fireEvent(new IoFilterEvent(nextFilter,
                     IoEventType.EXCEPTION_CAUGHT, session, cause));
         } else {
             nextFilter.exceptionCaught(session, cause);
         }
     }
 
     @Override
     public final void messageReceived(NextFilter nextFilter, IoSession session,
             Object message) {
         if (eventTypes.contains(IoEventType.MESSAGE_RECEIVED)) {
             fireEvent(new IoFilterEvent(nextFilter,
                     IoEventType.MESSAGE_RECEIVED, session, message));
         } else {
             nextFilter.messageReceived(session, message);
         }
     }
 
     @Override
     public final void messageSent(NextFilter nextFilter, IoSession session,
             WriteRequest writeRequest) {
         if (eventTypes.contains(IoEventType.MESSAGE_SENT)) {
             fireEvent(new IoFilterEvent(nextFilter, IoEventType.MESSAGE_SENT,
                     session, writeRequest));
         } else {
             nextFilter.messageSent(session, writeRequest);
         }
     }
 
     @Override
     public final void filterWrite(NextFilter nextFilter, IoSession session,
             WriteRequest writeRequest) {
         if (eventTypes.contains(IoEventType.WRITE)) {
             fireEvent(new IoFilterEvent(nextFilter, IoEventType.WRITE, session,
                     writeRequest));
         } else {
             nextFilter.filterWrite(session, writeRequest);
         }
     }
 
     @Override
     public final void filterClose(NextFilter nextFilter, IoSession session)
             throws Exception {
         if (eventTypes.contains(IoEventType.CLOSE)) {
             fireEvent(new IoFilterEvent(nextFilter, IoEventType.CLOSE, session,
                     null));
         } else {
             nextFilter.filterClose(session);
         }
     }
 }