//
   //  ========================================================================
   //  Copyright (c) 1995-2012 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.io.Closeable;
  import java.io.IOException;
  import java.net.ConnectException;
  import java.net.Socket;
  import java.net.SocketAddress;
  import java.nio.channels.CancelledKeyException;
  import java.nio.channels.ClosedChannelException;
  import java.nio.channels.SelectionKey;
  import java.nio.channels.Selector;
  import java.nio.channels.ServerSocketChannel;
  import java.nio.channels.SocketChannel;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Queue;
  import java.util.Set;
  import java.util.concurrent.ConcurrentLinkedQueue;
  import java.util.concurrent.CountDownLatch;
  import java.util.concurrent.TimeUnit;
  
  import org.eclipse.jetty.util.ForkInvoker;
  import org.eclipse.jetty.util.TypeUtil;
  import org.eclipse.jetty.util.annotation.Name;
  import org.eclipse.jetty.util.component.AbstractLifeCycle;
  import org.eclipse.jetty.util.component.ContainerLifeCycle;
  import org.eclipse.jetty.util.component.Dumpable;
  import org.eclipse.jetty.util.log.Log;
  import org.eclipse.jetty.util.log.Logger;
  
  /**
   * <p>{@link SelectorManager} manages a number of {@link ManagedSelector}s that
   * simplify the non-blocking primitives provided by the JVM via the {@code java.nio} package.</p>
   * <p>{@link SelectorManager} subclasses implement methods to return protocol-specific
   * {@link EndPoint}s and {@link Connection}s.</p>
   */
  public abstract class SelectorManager extends AbstractLifeCycle implements Dumpable
  {
      protected static final Logger LOG = Log.getLogger(SelectorManager.class);
  
      private final ManagedSelector[] _selectors;
      private volatile long _selectorIndex;
  
      protected SelectorManager()
      {
          this((Runtime.getRuntime().availableProcessors() + 1) / 2);
      }
  
      protected SelectorManager(@Name(value="selectors") int selectors)
      {
          _selectors = new ManagedSelector[selectors];
      }
  
      /**
       * Executes the given task in a different thread.
       *
       * @param task the task to execute
       */
      protected abstract void execute(Runnable task);
  
      /**
       * @return the number of selectors in use
       */
      public int getSelectorCount()
      {
          return _selectors.length;
      }
  
      private ManagedSelector chooseSelector()
      {
          // The ++ increment here is not atomic, but it does not matter,
          // so long as the value changes sometimes, then connections will
          // be distributed over the available selectors.
          long s = _selectorIndex++;
          int index = (int)(s % getSelectorCount());
          return _selectors[index];
      }
  
      /**
       * <p>Registers a channel to perform a non-blocking connect.</p>
       * <p>The channel must be set in non-blocking mode, and {@link SocketChannel#connect(SocketAddress)}
      * must be called prior to calling this method.</p>
      *
      * @param channel    the channel to register
      * @param attachment the attachment object
      */
     public void connect(SocketChannel channel, Object attachment)
     {
         ManagedSelector set = chooseSelector();
         set.submit(set.new Connect(channel, attachment));
     }
 
     /**
      * <p>Registers a channel to perform non-blocking read/write operations.</p>
      * <p>This method is called just after a channel has been accepted by {@link ServerSocketChannel#accept()},
      * or just after having performed a blocking connect via {@link Socket#connect(SocketAddress, int)}.</p>
      *
      * @param channel the channel to register
      */
     public void accept(final SocketChannel channel)
     {
         final ManagedSelector selector = chooseSelector();
         selector.submit(selector.new Accept(channel));
     }
 
     @Override
     protected void doStart() throws Exception
     {
         super.doStart();
         for (int i = 0; i < _selectors.length; i++)
         {
             ManagedSelector selector = newSelector(i);
             _selectors[i] = selector;
             selector.start();
             execute(selector);
         }
     }
 
     /**
      * <p>Factory method for {@link ManagedSelector}.</p>
      *
      * @param id an identifier for the {@link ManagedSelector to create}
      * @return a new {@link ManagedSelector}
      */
     protected ManagedSelector newSelector(int id)
     {
         return new ManagedSelector(id);
     }
 
     @Override
     protected void doStop() throws Exception
     {
         for (ManagedSelector selector : _selectors)
             selector.stop();
         super.doStop();
     }
 
     /**
      * <p>Callback method invoked when an endpoint is opened.</p>
      *
      * @param endpoint the endpoint being opened
      */
     protected void endPointOpened(EndPoint endpoint)
     {
         endpoint.onOpen();
     }
 
     /**
      * <p>Callback method invoked when an endpoint is closed.</p>
      *
      * @param endpoint the endpoint being closed
      */
     protected void endPointClosed(EndPoint endpoint)
     {
         endpoint.onClose();
     }
 
     /**
      * <p>Callback method invoked when a connection is opened.</p>
      *
      * @param connection the connection just opened
      */
     public void connectionOpened(Connection connection)
     {
         try
         {
             connection.onOpen();
         }
         catch (Exception x)
         {
             LOG.info("Exception while notifying connection " + connection, x);
         }
     }
 
     /**
      * <p>Callback method invoked when a connection is closed.</p>
      *
      * @param connection the connection just closed
      */
     public void connectionClosed(Connection connection)
     {
         try
         {
             connection.onClose();
         }
         catch (Exception x)
         {
             LOG.info("Exception while notifying connection " + connection, x);
         }
     }
 
     /**
      * <p>Callback method invoked when a non-blocking connect cannot be completed.</p>
      * <p>By default it just logs with level warning.</p>
      *
      * @param channel the channel that attempted the connect
      * @param ex the exception that caused the connect to fail
      * @param attachment the attachment object associated at registration
      */
     protected void connectionFailed(SocketChannel channel, Throwable ex, Object attachment)
     {
         LOG.warn(String.format("%s - %s", channel, attachment), ex);
     }
 
     /**
      * <p>Factory method to create {@link EndPoint}.</p>
      * <p>This method is invoked as a result of the registration of a channel via {@link #connect(SocketChannel, Object)}
      * or {@link #accept(SocketChannel)}.</p>
      *
      * @param channel   the channel associated to the endpoint
      * @param selector the selector the channel is registered to
      * @param selectionKey      the selection key
      * @return a new endpoint
      * @throws IOException if the endPoint cannot be created
      * @see #newConnection(SocketChannel, EndPoint, Object)
      */
     protected abstract EndPoint newEndPoint(SocketChannel channel, SelectorManager.ManagedSelector selector, SelectionKey selectionKey) throws IOException;
 
     /**
      * <p>Factory method to create {@link Connection}.</p>
      *
      * @param channel    the channel associated to the connection
      * @param endpoint   the endpoint
      * @param attachment the attachment
      * @return a new connection
      * @throws IOException
      * @see #newEndPoint(SocketChannel, ManagedSelector, SelectionKey)
      */
     public abstract Connection newConnection(SocketChannel channel, EndPoint endpoint, Object attachment) throws IOException;
 
     @Override
     public String dump()
     {
         return ContainerLifeCycle.dump(this);
     }
 
     @Override
     public void dump(Appendable out, String indent) throws IOException
     {
         ContainerLifeCycle.dumpObject(out, this);
         ContainerLifeCycle.dump(out, indent, TypeUtil.asList(_selectors));
     }
 
     /**
      * <p>{@link ManagedSelector} wraps a {@link Selector} simplifying non-blocking operations on channels.</p>
      * <p>{@link ManagedSelector} runs the select loop, which waits on {@link Selector#select()} until events
      * happen for registered channels. When events happen, it notifies the {@link EndPoint} associated
      * with the channel.</p>
      */
     public class ManagedSelector extends AbstractLifeCycle implements Runnable, Dumpable
     {
         private final ForkInvoker<Runnable> invoker = new ManagedSelectorInvoker();
         private final Queue<Runnable> _changes = new ConcurrentLinkedQueue<>();
         private final int _id;
         private Selector _selector;
         private Thread _thread;
         private boolean _needsWakeup = true;
 
         public ManagedSelector(int id)
         {
             _id = id;
             setStopTimeout(5000);
         }
 
         @Override
         protected void doStart() throws Exception
         {
             super.doStart();
             _selector = Selector.open();
         }
 
         @Override
         protected void doStop() throws Exception
         {
             LOG.debug("Stopping {}", this);
             Stop stop = new Stop();
             submit(stop);
             stop.await(getStopTimeout());
             LOG.debug("Stopped {}", this);
         }
 
         /**
          * <p>Submits a change to be executed in the selector thread.</p>
          * <p>Changes may be submitted from any thread, and if they are submitted from a thread different
          * from the selector thread, they are queued for execution, and the selector thread woken up
          * (if necessary) to execute the change.</p>
          *
          * @param change the change to submit
          * @return true if the change has been executed, false if it has been queued for later execution
          */
         public boolean submit(Runnable change)
         {
             return !invoker.invoke(change);
         }
 
         private void runChanges()
         {
             Runnable change;
             while ((change = _changes.poll()) != null)
                 runChange(change);
         }
 
         protected void runChange(Runnable change)
         {
             LOG.debug("Running change {}", change);
             change.run();
         }
 
         @Override
         public void run()
         {
             _thread = Thread.currentThread();
             String name = _thread.getName();
             try
             {
                 _thread.setName(name + "-selector-" + _id);
                 LOG.debug("Starting {} on {}", _thread, this);
                 while (isRunning())
                     select();
                 processChanges();
             }
             finally
             {
                 LOG.debug("Stopped {} on {}", _thread, this);
                 _thread.setName(name);
             }
         }
 
         /**
          * <p>Process changes and waits on {@link Selector#select()}.</p>
          *
          * @see #submit(Runnable)
          */
         public void select()
         {
             boolean debug = LOG.isDebugEnabled();
             try
             {
                 processChanges();
 
                 if (debug)
                     LOG.debug("Selector loop waiting on select");
                 int selected = _selector.select();
                 if (debug)
                     LOG.debug("Selector loop woken up from select, {}/{} selected", selected, _selector.keys().size());
 
                 _needsWakeup = false;
 
                 Set<SelectionKey> selectedKeys = _selector.selectedKeys();
                 for (SelectionKey key : selectedKeys)
                 {
                     if (key.isValid())
                     {
                         processKey(key);
                     }
                     else
                     {
                         if (debug)
                             LOG.debug("Selector loop ignoring invalid key for channel {}", key.channel());
                         Object attachment = key.attachment();
                         if (attachment instanceof EndPoint)
                             ((EndPoint)attachment).close();
                     }
                 }
                 selectedKeys.clear();
             }
             catch (Exception x)
             {
                 if (isRunning())
                     LOG.warn(x);
                 else
                     LOG.ignore(x);
             }
         }
 
         private void processChanges()
         {
             runChanges();
 
             // If tasks are submitted between these 2 statements, they will not
             // wakeup the selector, therefore below we run again the tasks
 
             _needsWakeup = true;
 
             // Run again the tasks to avoid the race condition where a task is
             // submitted but will not wake up the selector
             runChanges();
         }
 
         private void processKey(SelectionKey key)
         {
             Object attachment = key.attachment();
             try
             {
                 if (attachment instanceof SelectableEndPoint)
                 {
                     ((SelectableEndPoint)attachment).onSelected();
                 }
                 else if (key.isConnectable())
                 {
                     // Complete a connection of a registered channel
                     SocketChannel channel = (SocketChannel)key.channel();
                     try
                     {
                         boolean connected = channel.finishConnect();
                         if (connected)
                         {
                             key.interestOps(0);
                             EndPoint endpoint = createEndPoint(channel, key);
                             key.attach(endpoint);
                         }
                         else
                         {
                             throw new ConnectException();
                         }
                     }
                     catch (Exception x)
                     {
                         connectionFailed(channel, x, attachment);
                         closeNoExceptions(channel);
                     }
                 }
                 else
                 {
                     throw new IllegalStateException();
                 }
             }
             catch (CancelledKeyException x)
             {
                 LOG.debug("Ignoring cancelled key for channel {}", key.channel());
                 if (attachment instanceof EndPoint)
                     ((EndPoint)attachment).close();
             }
             catch (Exception x)
             {
                 LOG.warn("Could not process key for channel " + key.channel(), x);
                 if (attachment instanceof EndPoint)
                     ((EndPoint)attachment).close();
             }
         }
 
         private void closeNoExceptions(Closeable closeable)
         {
             try
             {
                 closeable.close();
             }
             catch (IOException x)
             {
                 LOG.ignore(x);
             }
         }
 
         public SelectorManager getSelectorManager()
         {
             return SelectorManager.this;
         }
 
         public void wakeup()
         {
             _selector.wakeup();
         }
 
         private EndPoint createEndPoint(SocketChannel channel, SelectionKey selectionKey) throws IOException
         {
             EndPoint endPoint = newEndPoint(channel, this, selectionKey);
             endPointOpened(endPoint);
             Connection connection = newConnection(channel, endPoint, selectionKey.attachment());
             endPoint.setConnection(connection);
             connectionOpened(connection);
             LOG.debug("Created {}", endPoint);
             return endPoint;
         }
 
         public void destroyEndPoint(EndPoint endPoint)
         {
             // TODO
 
             LOG.debug("Destroyed {}", endPoint);
             Connection connection = endPoint.getConnection();
             if (connection != null)
                 connectionClosed(connection);
             endPointClosed(endPoint);
         }
 
         @Override
         public String dump()
         {
             return ContainerLifeCycle.dump(this);
         }
 
         @Override
         public void dump(Appendable out, String indent) throws IOException
         {
             out.append(String.valueOf(this)).append(" id=").append(String.valueOf(_id)).append("\n");
 
             Thread selecting = _thread;
 
             Object where = "not selecting";
             StackTraceElement[] trace = selecting == null ? null : selecting.getStackTrace();
             if (trace != null)
             {
                 for (StackTraceElement t : trace)
                     if (t.getClassName().startsWith("org.eclipse.jetty."))
                     {
                         where = t;
                         break;
                     }
             }
 
             Selector selector = _selector;
             if (selector != null)
             {
                 final ArrayList<Object> dump = new ArrayList<>(selector.keys().size() * 2);
                 dump.add(where);
 
                 DumpKeys dumpKeys = new DumpKeys(dump);
                 submit(dumpKeys);
                 dumpKeys.await(5, TimeUnit.SECONDS);
 
                 ContainerLifeCycle.dump(out, indent, dump);
             }
         }
 
         public void dumpKeysState(List<Object> dumps)
         {
             Selector selector = _selector;
             Set<SelectionKey> keys = selector.keys();
             dumps.add(selector + " keys=" + keys.size());
             for (SelectionKey key : keys)
             {
                 if (key.isValid())
                     dumps.add(key.attachment() + " iOps=" + key.interestOps() + " rOps=" + key.readyOps());
                 else
                     dumps.add(key.attachment() + " iOps=-1 rOps=-1");
             }
         }
 
         @Override
         public String toString()
         {
             Selector selector = _selector;
             return String.format("%s keys=%d selected=%d",
                     super.toString(),
                     selector != null && selector.isOpen() ? selector.keys().size() : -1,
                     selector != null && selector.isOpen() ? selector.selectedKeys().size() : -1);
         }
 
         private class ManagedSelectorInvoker extends ForkInvoker<Runnable>
         {
             private ManagedSelectorInvoker()
             {
                 super(4);
             }
 
             @Override
             protected boolean condition()
             {
                 return Thread.currentThread() != _thread;
             }
 
             @Override
             public void fork(Runnable change)
             {
                 _changes.offer(change);
                 LOG.debug("Queued change {}", change);
                 boolean wakeup = _needsWakeup;
                 if (wakeup)
                     wakeup();
             }
 
             @Override
             public void call(Runnable change)
             {
                 LOG.debug("Submitted change {}", change);
                 runChanges();
                 runChange(change);
             }
         }
 
         private class DumpKeys implements Runnable
         {
             private final CountDownLatch latch = new CountDownLatch(1);
             private final List<Object> _dumps;
 
             private DumpKeys(List<Object> dumps)
             {
                 this._dumps = dumps;
             }
 
             @Override
             public void run()
             {
                 dumpKeysState(_dumps);
                 latch.countDown();
             }
 
             public boolean await(long timeout, TimeUnit unit)
             {
                 try
                 {
                     return latch.await(timeout, unit);
                 }
                 catch (InterruptedException x)
                 {
                     return false;
                 }
             }
         }
 
         private class Accept implements Runnable
         {
             private final SocketChannel _channel;
 
             public Accept(SocketChannel channel)
             {
                 this._channel = channel;
             }
 
             @Override
             public void run()
             {
                 try
                 {
                     SelectionKey key = _channel.register(_selector, 0, null);
                     EndPoint endpoint = createEndPoint(_channel, key);
                     key.attach(endpoint);
                 }
                 catch (IOException x)
                 {
                     LOG.debug(x);
                 }
             }
         }
 
         private class Connect implements Runnable
         {
             private final SocketChannel channel;
             private final Object attachment;
 
             public Connect(SocketChannel channel, Object attachment)
             {
                 this.channel = channel;
                 this.attachment = attachment;
             }
 
             @Override
             public void run()
             {
                 try
                 {
                     channel.register(_selector, SelectionKey.OP_CONNECT, attachment);
                 }
                 catch (ClosedChannelException x)
                 {
                     LOG.debug(x);
                 }
             }
         }
 
         private class Stop implements Runnable
         {
             private final CountDownLatch latch = new CountDownLatch(1);
 
             @Override
             public void run()
             {
                 try
                 {
                     for (SelectionKey key : _selector.keys())
                     {
                         Object attachment = key.attachment();
                         if (attachment instanceof EndPoint)
                         {
                             EndPointCloser closer = new EndPointCloser((EndPoint)attachment);
                             execute(closer);
                             // We are closing the SelectorManager, so we want to block the
                             // selector thread here until we have closed all EndPoints.
                             // This is different than calling close() directly, because close()
                             // can wait forever, while here we are limited by the stop timeout.
                             closer.await(getStopTimeout());
                         }
                     }
 
                     closeNoExceptions(_selector);
                 }
                 finally
                 {
                     latch.countDown();
                 }
             }
 
             public boolean await(long timeout)
             {
                 try
                 {
                     return latch.await(timeout, TimeUnit.MILLISECONDS);
                 }
                 catch (InterruptedException x)
                 {
                     return false;
                 }
             }
         }
 
         private class EndPointCloser implements Runnable
         {
             private final CountDownLatch latch = new CountDownLatch(1);
             private final EndPoint endPoint;
 
             private EndPointCloser(EndPoint endPoint)
             {
                 this.endPoint = endPoint;
             }
 
             @Override
             public void run()
             {
                 try
                 {
                     endPoint.getConnection().close();
                 }
                 finally
                 {
                     latch.countDown();
                 }
             }
 
             private boolean await(long timeout)
             {
                 try
                 {
                     return latch.await(timeout, TimeUnit.MILLISECONDS);
                 }
                 catch (InterruptedException x)
                 {
                     return false;
                 }
             }
         }
     }
 
     /**
      * A {@link SelectableEndPoint} is an {@link EndPoint} that wish to be notified of
      * non-blocking events by the {@link ManagedSelector}.
      */
     public interface SelectableEndPoint extends EndPoint
     {
         /**
          * <p>Callback method invoked when a read or write events has been detected by the {@link ManagedSelector}
          * for this endpoint.</p>
          */
         void onSelected();
     }
 }