/*
    *  Licensed to the Apache Software Foundation (ASF) under one
    *  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.transport.socket.nio;
  
  import java.io.IOException;
  import java.nio.channels.ByteChannel;
  import java.nio.channels.DatagramChannel;
  import java.nio.channels.SelectableChannel;
  import java.nio.channels.SelectionKey;
  import java.nio.channels.Selector;
  import java.nio.channels.SocketChannel;
  import java.util.Iterator;
  import java.util.Set;
  import java.util.concurrent.Executor;
  
  import org.apache.mina.core.RuntimeIoException;
  import org.apache.mina.core.buffer.IoBuffer;
  import org.apache.mina.core.file.FileRegion;
  import org.apache.mina.core.polling.AbstractPollingIoProcessor;
  import org.apache.mina.core.session.SessionState;
  
  /**
   * TODO Add documentation
   *
   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
   */
  public final class NioProcessor extends AbstractPollingIoProcessor<NioSession> {
      /** The selector associated with this processor */
      private Selector selector;
  
      /**
       *
       * Creates a new instance of NioProcessor.
       *
       * @param executor
       */
      public NioProcessor(Executor executor) {
          super(executor);
  
          try {
              // Open a new selector
              selector = Selector.open();
          } catch (IOException e) {
              throw new RuntimeIoException("Failed to open a selector.", e);
          }
      }
  
      @Override
      protected void doDispose() throws Exception {
          selector.close();
      }
  
      @Override
      protected int select(long timeout) throws Exception {
          return selector.select(timeout);
      }
  
      @Override
      protected int select() throws Exception {
          return selector.select();
      }
  
      @Override
      protected boolean isSelectorEmpty() {
          return selector.keys().isEmpty();
      }
  
      @Override
      protected void wakeup() {
          wakeupCalled.getAndSet(true);
          selector.wakeup();
      }
  
      @Override
      protected Iterator<NioSession> allSessions() {
          return new IoSessionIterator(selector.keys());
      }
  
      @SuppressWarnings("synthetic-access")
      @Override
      protected Iterator<NioSession> selectedSessions() {
          return new IoSessionIterator(selector.selectedKeys());
     }
 
     @Override
     protected void init(NioSession session) throws Exception {
         SelectableChannel ch = (SelectableChannel) session.getChannel();
         ch.configureBlocking(false);
         session.setSelectionKey(ch.register(selector, SelectionKey.OP_READ,
                 session));
     }
 
     @Override
     protected void destroy(NioSession session) throws Exception {
         ByteChannel ch = session.getChannel();
         SelectionKey key = session.getSelectionKey();
         if (key != null) {
             key.cancel();
         }
         ch.close();
     }
 
 
     /**
      * In the case we are using the java select() method, this method is used to
      * trash the buggy selector and create a new one, registering all the
      * sockets on it.
      */
     @Override
     protected void registerNewSelector() throws IOException {
         synchronized (selector) {
             Set<SelectionKey> keys = selector.keys();
 
             // Open a new selector
             Selector newSelector = Selector.open();
 
             // Loop on all the registered keys, and register them on the new selector
             for (SelectionKey key : keys) {
                 SelectableChannel ch = key.channel();
 
                 // Don't forget to attache the session, and back !
                 NioSession session = (NioSession)key.attachment();
                 SelectionKey newKey = ch.register(newSelector, key.interestOps(), session);
                 session.setSelectionKey( newKey );
             }
 
             // Now we can close the old selector and switch it
             selector.close();
             selector = newSelector;
         }
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     protected boolean isBrokenConnection() throws IOException {
         // A flag set to true if we find a broken session
         boolean brokenSession = false;
 
         synchronized (selector) {
             // Get the selector keys
             Set<SelectionKey> keys = selector.keys();
 
             // Loop on all the keys to see if one of them
             // has a closed channel
             for (SelectionKey key : keys) {
                 SelectableChannel channel = key.channel();
 
                 if ((((channel instanceof DatagramChannel) && !((DatagramChannel) channel)
                         .isConnected()))
                         || ((channel instanceof SocketChannel) && !((SocketChannel) channel)
                                 .isConnected())) {
                     // The channel is not connected anymore. Cancel
                     // the associated key then.
                     key.cancel();
 
                     // Set the flag to true to avoid a selector switch
                     brokenSession = true;
                 }
             }
         }
 
         return brokenSession;
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     protected SessionState getState(NioSession session) {
         SelectionKey key = session.getSelectionKey();
 
         if (key == null) {
             // The channel is not yet registred to a selector
             return SessionState.OPENING;
         }
 
         if (key.isValid()) {
             // The session is opened
             return SessionState.OPENED;
         } else {
             // The session still as to be closed
             return SessionState.CLOSING;
         }
     }
 
     @Override
     protected boolean isReadable(NioSession session) {
         SelectionKey key = session.getSelectionKey();
         return key.isValid() && key.isReadable();
     }
 
     @Override
     protected boolean isWritable(NioSession session) {
         SelectionKey key = session.getSelectionKey();
         return key.isValid() && key.isWritable();
     }
 
     @Override
     protected boolean isInterestedInRead(NioSession session) {
         SelectionKey key = session.getSelectionKey();
         return key.isValid() && ( (key.interestOps() & SelectionKey.OP_READ) != 0 );
     }
 
     @Override
     protected boolean isInterestedInWrite(NioSession session) {
         SelectionKey key = session.getSelectionKey();
         return key.isValid()
                 && ( (key.interestOps() & SelectionKey.OP_WRITE) != 0 );
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     protected void setInterestedInRead(NioSession session, boolean isInterested)
             throws Exception {
         SelectionKey key = session.getSelectionKey();
         int oldInterestOps = key.interestOps();
         int newInterestOps = oldInterestOps;
 
         if (isInterested) {
             newInterestOps |= SelectionKey.OP_READ;
         } else {
             newInterestOps &= ~SelectionKey.OP_READ;
         }
 
         if (oldInterestOps != newInterestOps) {
             key.interestOps(newInterestOps);
         }
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     protected void setInterestedInWrite(NioSession session, boolean isInterested)
             throws Exception {
         SelectionKey key = session.getSelectionKey();
 
         if (key == null) {
             return;
         }
 
         int newInterestOps = key.interestOps();
 
         if (isInterested) {
             newInterestOps |= SelectionKey.OP_WRITE;
             //newInterestOps &= ~SelectionKey.OP_READ;
         } else {
             newInterestOps &= ~SelectionKey.OP_WRITE;
             //newInterestOps |= SelectionKey.OP_READ;
         }
 
         key.interestOps(newInterestOps);
     }
 
     @Override
     protected int read(NioSession session, IoBuffer buf) throws Exception {
         ByteChannel channel = session.getChannel();
 
         return channel.read(buf.buf());
     }
 
     @Override
     protected int write(NioSession session, IoBuffer buf, int length)
             throws Exception {
         if (buf.remaining() <= length) {
             return session.getChannel().write(buf.buf());
         }
 
         int oldLimit = buf.limit();
         buf.limit(buf.position() + length);
         try {
             return session.getChannel().write(buf.buf());
         } finally {
             buf.limit(oldLimit);
         }
     }
 
     @Override
     protected int transferFile(NioSession session, FileRegion region, int length)
             throws Exception {
         try {
             return (int) region.getFileChannel().transferTo(
                     region.getPosition(), length, session.getChannel());
         } catch (IOException e) {
             // Check to see if the IOException is being thrown due to
             // http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=5103988
             String message = e.getMessage();
             if (( message != null ) && message.contains("temporarily unavailable")) {
                 return 0;
             }
 
             throw e;
         }
     }
 
     /**
      * An encapsulating iterator around the {@link Selector#selectedKeys()} or
      * the {@link Selector#keys()} iterator;
      */
     protected static class IoSessionIterator<NioSession> implements
             Iterator<NioSession> {
         private final Iterator<SelectionKey> iterator;
 
         /**
          * Create this iterator as a wrapper on top of the selectionKey Set.
          *
          * @param keys
          *            The set of selected sessions
          */
         private IoSessionIterator(Set<SelectionKey> keys) {
             iterator = keys.iterator();
         }
 
         /**
          * {@inheritDoc}
          */
         public boolean hasNext() {
             return iterator.hasNext();
         }
 
         /**
          * {@inheritDoc}
          */
         public NioSession next() {
             SelectionKey key = iterator.next();
             NioSession nioSession = (NioSession) key.attachment();
             return nioSession;
         }
 
         /**
          * {@inheritDoc}
          */
         public void remove() {
             iterator.remove();
         }
     }
 }