/*
    *  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.SelectableChannel;
  import java.nio.channels.SelectionKey;
  import java.nio.channels.Selector;
  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;
  
  /**
   * TODO Add documentation
   * 
   * @author The Apache MINA Project (dev@mina.apache.org)
   */
  public final class NioProcessor extends AbstractPollingIoProcessor<NioSession> {
      /** The selector associated with this processor */
      private final 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 dispose0() 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() {
          selector.wakeup();
      }
  
      @Override
      protected Iterator<NioSession> allSessions() {
          return new IoSessionIterator(selector.keys());
      }
  
      @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();
     }
 
     @Override
     protected SessionState state(NioSession session) {
         SelectionKey key = session.getSelectionKey();
         if (key == null) {
             return SessionState.PREPARING;
         }
 
         return key.isValid()? SessionState.OPEN : SessionState.CLOSED;
     }
 
     @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;
     }
 
     @Override
     protected void setInterestedInRead(NioSession session, boolean value) throws Exception {
         SelectionKey key = session.getSelectionKey();
         int oldInterestOps = key.interestOps();
         int newInterestOps;
         if (value) {
             newInterestOps = oldInterestOps | SelectionKey.OP_READ;
         } else {
             newInterestOps = oldInterestOps & ~SelectionKey.OP_READ;
         }
         if (oldInterestOps != newInterestOps) {
             key.interestOps(newInterestOps);
         }
     }
 
     @Override
     protected void setInterestedInWrite(NioSession session, boolean value) throws Exception {
         SelectionKey key = session.getSelectionKey();
         int oldInterestOps = key.interestOps();
         int newInterestOps;
         if (value) {
             newInterestOps = oldInterestOps | SelectionKey.OP_WRITE;
         } else {
             newInterestOps = oldInterestOps & ~SelectionKey.OP_WRITE;
         }
         if (oldInterestOps != newInterestOps) {
             key.interestOps(newInterestOps);
         }
     }
 
     @Override
     protected int read(NioSession session, IoBuffer buf) throws Exception {
         return session.getChannel().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 implements Iterator<NioSession> {
         private final Iterator<SelectionKey> iterator;
         
         /**
          * Create this iterator as a wrapper on top of the selectionKey
          * Set.
          * @param keys
          */
         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();
         }
     }
 }