//
   //  ========================================================================
   //  Copyright (c) 1995-2016 Mort Bay Consulting Pty. Ltd.
   //  ------------------------------------------------------------------------
   //  All rights reserved. This program and the accompanying materials
   //  are made available under the terms of the Eclipse Public License v1.0
   //  and Apache License v2.0 which accompanies this distribution.
   //
   //      The Eclipse Public License is available at
  //      http://www.eclipse.org/legal/epl-v10.html
  //
  //      The Apache License v2.0 is available at
  //      http://www.opensource.org/licenses/apache2.0.php
  //
  //  You may elect to redistribute this code under either of these licenses.
  //  ========================================================================
  //
  
  package org.eclipse.jetty.io;
  
  import java.nio.channels.CancelledKeyException;
  import java.nio.channels.SelectionKey;
  import java.nio.channels.SocketChannel;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  import org.eclipse.jetty.util.log.Log;
  import org.eclipse.jetty.util.log.Logger;
  import org.eclipse.jetty.util.thread.Locker;
  import org.eclipse.jetty.util.thread.Scheduler;
  
  /**
   * An ChannelEndpoint that can be scheduled by {@link SelectorManager}.
   */
  public class SelectChannelEndPoint extends ChannelEndPoint implements ManagedSelector.SelectableEndPoint
  {
      public static final Logger LOG = Log.getLogger(SelectChannelEndPoint.class);
  
      private final Locker _locker = new Locker();
      private boolean _updatePending;
  
      /**
       * true if {@link ManagedSelector#destroyEndPoint(EndPoint)} has not been called
       */
      private final AtomicBoolean _open = new AtomicBoolean();
      private final ManagedSelector _selector;
      private final SelectionKey _key;
      /**
       * The current value for {@link SelectionKey#interestOps()}.
       */
      private int _currentInterestOps;
      /**
       * The desired value for {@link SelectionKey#interestOps()}.
       */
      private int _desiredInterestOps;
  
      private final Runnable _runUpdateKey = new Runnable()
      {
          @Override
          public void run()
          {
              updateKey();
          }
  
          @Override
          public String toString()
          {
              return SelectChannelEndPoint.this.toString()+":runUpdateKey";
          }
      };
      private final Runnable _runFillable = new Runnable()
      {
          @Override
          public void run()
          {
              getFillInterest().fillable();
          }
  
          @Override
          public String toString()
          {
              return SelectChannelEndPoint.this.toString()+":runFillable";
          }
      };
      private final Runnable _runCompleteWrite = new Runnable()
      {
          @Override
          public void run()
          {
              getWriteFlusher().completeWrite();
          }
  
          @Override
          public String toString()
          {
              return SelectChannelEndPoint.this.toString()+":runCompleteWrite";
          }
      };
      private final Runnable _runFillableCompleteWrite = new Runnable()
      {
         @Override
         public void run()
         {
             getFillInterest().fillable();
             getWriteFlusher().completeWrite();
         }
 
         @Override
         public String toString()
         {
             return SelectChannelEndPoint.this.toString()+":runFillableCompleteWrite";
         }
     };
 
     public SelectChannelEndPoint(SocketChannel channel, ManagedSelector selector, SelectionKey key, Scheduler scheduler, long idleTimeout)
     {
         super(scheduler, channel);
         _selector = selector;
         _key = key;
         setIdleTimeout(idleTimeout);
     }
 
     @Override
     protected void needsFillInterest()
     {
         changeInterests(SelectionKey.OP_READ);
     }
 
     @Override
     protected void onIncompleteFlush()
     {
         changeInterests(SelectionKey.OP_WRITE);
     }
 
     @Override
     public Runnable onSelected()
     {
         /**
          * This method may run concurrently with {@link #changeInterests(int)}.
          */
 
         int readyOps = _key.readyOps();
         int oldInterestOps;
         int newInterestOps;
         try (Locker.Lock lock = _locker.lock())
         {
             _updatePending = true;
             // Remove the readyOps, that here can only be OP_READ or OP_WRITE (or both).
             oldInterestOps = _desiredInterestOps;
             newInterestOps = oldInterestOps & ~readyOps;
             _desiredInterestOps = newInterestOps;
         }
 
 
         boolean readable = (readyOps & SelectionKey.OP_READ) != 0;
         boolean writable = (readyOps & SelectionKey.OP_WRITE) != 0;
 
 
         if (LOG.isDebugEnabled())
             LOG.debug("onSelected {}->{} r={} w={} for {}", oldInterestOps, newInterestOps, readable, writable, this);
         
         // Run non-blocking code immediately.
         // This producer knows that this non-blocking code is special
         // and that it must be run in this thread and not fed to the
         // ExecutionStrategy, which could not have any thread to run these
         // tasks (or it may starve forever just after having run them).
         if (readable && getFillInterest().isCallbackNonBlocking())
         {
             if (LOG.isDebugEnabled())
                 LOG.debug("Direct readable run {}",this);
             _runFillable.run();
             readable = false;
         }
         if (writable && getWriteFlusher().isCallbackNonBlocking())
         {
             if (LOG.isDebugEnabled())
                 LOG.debug("Direct writable run {}",this);
             _runCompleteWrite.run();
             writable = false;
         }
 
         // return task to complete the job
         Runnable task= readable ? (writable ? _runFillableCompleteWrite : _runFillable)
                 : (writable ? _runCompleteWrite : null);
 
         if (LOG.isDebugEnabled())
             LOG.debug("task {}",task);
         return task;
     }
 
     @Override
     public void updateKey()
     {
         /**
          * This method may run concurrently with {@link #changeInterests(int)}.
          */
 
         try
         {
             int oldInterestOps;
             int newInterestOps;
             try (Locker.Lock lock = _locker.lock())
             {
                 _updatePending = false;
                 oldInterestOps = _currentInterestOps;
                 newInterestOps = _desiredInterestOps;
                 if (oldInterestOps != newInterestOps)
                 {
                     _currentInterestOps = newInterestOps;
                     _key.interestOps(newInterestOps);
                 }
             }
 
             if (LOG.isDebugEnabled())
                 LOG.debug("Key interests updated {} -> {} on {}", oldInterestOps, newInterestOps, this);
         }
         catch (CancelledKeyException x)
         {
             LOG.debug("Ignoring key update for concurrently closed channel {}", this);
             close();
         }
         catch (Throwable x)
         {
             LOG.warn("Ignoring key update for " + this, x);
             close();
         }
     }
 
     private void changeInterests(int operation)
     {
         /**
          * This method may run concurrently with
          * {@link #updateKey()} and {@link #onSelected()}.
          */
 
         int oldInterestOps;
         int newInterestOps;
         boolean pending;
         try (Locker.Lock lock = _locker.lock())
         {
             pending = _updatePending;
             oldInterestOps = _desiredInterestOps;
             newInterestOps = oldInterestOps | operation;
             if (newInterestOps != oldInterestOps)
                 _desiredInterestOps = newInterestOps;
         }
 
         if (LOG.isDebugEnabled())
             LOG.debug("changeInterests p={} {}->{} for {}", pending, oldInterestOps, newInterestOps, this);
 
         if (!pending)
             _selector.submit(_runUpdateKey);
     }
 
 
     @Override
     public void close()
     {
         if (_open.compareAndSet(true, false))
         {
             super.close();
             _selector.destroyEndPoint(this);
         }
     }
 
     @Override
     public boolean isOpen()
     {
         // We cannot rely on super.isOpen(), because there is a race between calls to close() and isOpen():
         // a thread may call close(), which flips the boolean but has not yet called super.close(), and
         // another thread calls isOpen() which would return true - wrong - if based on super.isOpen().
         return _open.get();
     }
 
     @Override
     public void onOpen()
     {
         if (_open.compareAndSet(false, true))
             super.onOpen();
     }
 
     @Override
     public String toString()
     {
         // We do a best effort to print the right toString() and that's it.
         try
         {
             boolean valid = _key != null && _key.isValid();
             int keyInterests = valid ? _key.interestOps() : -1;
             int keyReadiness = valid ? _key.readyOps() : -1;
             return String.format("%s{io=%d/%d,kio=%d,kro=%d}",
                     super.toString(),
                     _currentInterestOps,
                     _desiredInterestOps,
                     keyInterests,
                     keyReadiness);
         }
         catch (Throwable x)
         {
             return String.format("%s{io=%s,kio=-2,kro=-2}", super.toString(), _desiredInterestOps);
         }
     }
 }