/***
    * Redistribution and use of this software and associated documentation
    * ("Software"), with or without modification, are permitted provided
    * that the following conditions are met:
    *
    * 1. Redistributions of source code must retain copyright
    *    statements and notices.  Redistributions must also contain a
    *    copy of this document.
    *
   * 2. Redistributions in binary form must reproduce the
   *    above copyright notice, this list of conditions and the
   *    following disclaimer in the documentation and/or other
   *    materials provided with the distribution.
   *
   * 3. The name "Exolab" must not be used to endorse or promote
   *    products derived from this Software without prior written
   *    permission of Exoffice Technologies.  For written permission,
   *    please contact info@exolab.org.
   *
   * 4. Products derived from this Software may not be called "Exolab"
   *    nor may "Exolab" appear in their names without prior written
   *    permission of Exoffice Technologies. Exolab is a registered
   *    trademark of Exoffice Technologies.
   *
   * 5. Due credit should be given to the Exolab Project
   *    (http://www.exolab.org/).
   *
   * THIS SOFTWARE IS PROVIDED BY EXOFFICE TECHNOLOGIES AND CONTRIBUTORS
   * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
   * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
   * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
   * EXOFFICE TECHNOLOGIES OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
   * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
   * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
   * OF THE POSSIBILITY OF SUCH DAMAGE.
   *
   * Copyright 2001-2005 (C) Exoffice Technologies Inc. All Rights Reserved.
   *
   * $Id: QueueDestinationCache.java,v 1.9 2006/06/09 12:58:56 tanderson Exp $
   */
  package org.exolab.jms.messagemgr;
  
  import java.sql.Connection;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.LinkedList;
  import java.util.List;
  import javax.jms.JMSException;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  import org.exolab.jms.client.JmsDestination;
  import org.exolab.jms.client.JmsQueue;
  import org.exolab.jms.client.JmsTemporaryDestination;
  import org.exolab.jms.lease.LeaseManager;
  import org.exolab.jms.message.MessageImpl;
  import org.exolab.jms.persistence.DatabaseService;
  import org.exolab.jms.persistence.PersistenceException;
  import org.exolab.jms.selector.Selector;
  import org.exolab.jms.server.ServerConnectionManager;
  
  
  /***
   * A {@link DestinationCache} for queues.
   *
   * @author <a href="mailto:jima@comware.com.au">Jim Alateras</a>
   * @author <a href="mailto:tma@netspace.net.au">Tim Anderson</a>
   * @version $Revision: 1.9 $ $Date: 2006/06/09 12:58:56 $
   */
  public class QueueDestinationCache extends AbstractDestinationCache {
  
      /***
       * Maintains a list of {@link QueueConsumerMessageHandle} instances.
       */
      private final MessageQueue _handles = new MessageQueue();
  
      /***
       * Maintains a list of queue browsers for this cache.
       */
      private final List _browsers
              = Collections.synchronizedList(new LinkedList());
  
      /***
       * The connection manager.
       */
      private final ServerConnectionManager _connections;
  
      /***
       * Synchronization helper.
       */
      private final Object _lock = new Object();
  
      /***
       * Index of the last {@link QueueConsumerEndpoint} that received a message
      * from this destination. If multiple consumers are attached to this queue
      * then messages will be sent to each in a round robin fashion
      */
     private int _lastConsumerIndex = 0;
 
     /***
      * The logger.
      */
     private static final Log _log = LogFactory.getLog(
             QueueDestinationCache.class);
 
 
     /***
      * Construct a new <code>QueueDestinationCache</code>.
      *
      * @param queue       the queue to cache messages for
      * @param database    the database service
      * @param leases      the lease manager
      * @param connections the connection manager
      * @throws JMSException if the cache can't be initialised
      */
     public QueueDestinationCache(JmsQueue queue,
                                  DatabaseService database,
                                  LeaseManager leases,
                                  ServerConnectionManager connections)
             throws JMSException {
         super(queue, database, leases);
         if (connections == null) {
             throw new IllegalArgumentException(
                     "Argument 'connections' is null");
         }
         _connections = connections;
 
         if (queue.getPersistent()) {
             init();
         }
     }
 
     /***
      * A Queue can also hav a queue listener, which simply gets informed of all
      * messages that arrive at this destination.
      *
      * @param listener - queue listener
      */
     public void addQueueListener(QueueBrowserEndpoint listener) {
         // add if not present
         if (!_browsers.contains(listener)) {
             _browsers.add(listener);
         }
     }
 
     /***
      * Remove the queue listener associated with this cache
      *
      * @param listener - queue listener to remove
      */
     public void removeQueueListener(QueueBrowserEndpoint listener) {
         // add if not present
         if (_browsers.contains(listener)) {
             _browsers.remove(listener);
         }
     }
 
     /***
      * Invoked when the {@link MessageMgr} receives a non-persistent message.
      *
      * @param destination the message's destination
      * @param message     the message
      * @throws JMSException if the listener fails to handle the message
      */
     public void messageAdded(JmsDestination destination, MessageImpl message)
             throws JMSException {
         MessageRef reference = new CachedMessageRef(message, false,
                 getMessageCache());
         MessageHandle shared = new SharedMessageHandle(this, reference,
                 message);
         MessageHandle handle = new QueueConsumerMessageHandle(shared);
 
         // all messages are added to this queue. Receivers will
         // then pick messages from it as required.
         addMessage(reference, message, handle);
 
         // if we have any registered consumers then we need to
         // send the message to one of them first.
         ConsumerEndpoint consumer = getConsumerForMessage(message);
         if (consumer != null) {
             consumer.messageAdded(handle, message);
         }
     }
 
     /***
      * Invoked when the {@link MessageMgr} receives a persistent message.
      *
      * @param destination the message's destination
      * @param message     the message
      * @throws JMSException         if the listener fails to handle the message
      * @throws PersistenceException if there is a persistence related problem
      */
     public void persistentMessageAdded(JmsDestination destination,
                                        MessageImpl message)
             throws JMSException, PersistenceException {
         MessageRef reference = new CachedMessageRef(message, true,
                 getMessageCache());
         MessageHandle shared = new SharedMessageHandle(this, reference,
                 message);
         MessageHandle handle = new QueueConsumerMessageHandle(shared);
         handle.add();
 
         addMessage(reference, message, handle);
 
         // if there are any registered consumers, notify one of them that
         // a message has arrived
         ConsumerEndpoint consumer = getConsumerForMessage(message);
         if (consumer != null) {
             consumer.persistentMessageAdded(handle, message);
         }
     }
 
     /***
      * Returns the first available message matching the supplied message
      * selector.
      *
      * @param selector the message selector to use. May be <code>null</code>
      * @param cancel
      * @return handle to the first message, or <code>null</code> if there are no
      *         messages, or none matching <code>selector</code>
      * @throws JMSException for any error
      */
     public synchronized MessageHandle getMessage(Selector selector,
                                                  Condition cancel)
             throws JMSException {
         QueueConsumerMessageHandle handle = null;
         if (selector == null) {
             // if no selector has been specified then remove and return
             // the first message
             handle = (QueueConsumerMessageHandle) _handles.removeFirst();
         } else {
             // for non null selector we must find the first matching
             MessageHandle[] handles = _handles.toArray();
             for (int i = 0; i < handles.length && !cancel.get(); ++i) {
                 MessageHandle hdl = handles[i];
                 MessageImpl message = hdl.getMessage();
                 if (message != null && selector.selects(message)) {
                     handle = (QueueConsumerMessageHandle) hdl;
                     _handles.remove(handle);
                     break;
                 }
             }
         }
         return handle;
     }
 
     /***
      * Playback all the messages in the cache to the specified {@link
      * QueueBrowserEndpoint}.
      *
      * @param browser the queue browser
      * @throws JMSException for any error
      */
     public void playbackMessages(QueueBrowserEndpoint browser)
             throws JMSException {
         MessageHandle[] handles = _handles.toArray();
         for (int i = 0; i < handles.length; ++i) {
             MessageHandle handle = handles[i];
             MessageImpl message = handle.getMessage();
             if (message != null) {
                 browser.messageAdded(handle, message);
             }
         }
     }
 
     /***
      * Return a message handle back to the cache, to recover unsent or
      * unacknowledged messages.
      *
      * @param handle the message handle to return
      */
     public void returnMessageHandle(MessageHandle handle) {
         // add the message to the destination cache
         _handles.add(handle);
         try {
             MessageImpl message = handle.getMessage();
             if (message != null) {
                 // if there are any registered consumers, notify one of them
                 // that a message has arrived
                 ConsumerEndpoint consumer = getConsumerForMessage(message);
                 if (consumer != null) {
                     consumer.messageAdded(handle, message);
                 }
             }
         } catch (JMSException exception) {
             _log.debug(exception, exception);
         }
     }
 
     /***
      * Determines if there are any registered consumers.
      *
      * @return <code>true</code> if there are registered consumers
      */
     public boolean hasConsumers() {
         boolean active = super.hasConsumers();
         if (!active && !_browsers.isEmpty()) {
             active = true;
         }
         if (_log.isDebugEnabled()) {
             _log.debug("hasActiveConsumers()[queue=" + getDestination() + "]="
                     + active);
         }
         return active;
     }
 
     /***
      * Returns the number of messages in the cache.
      *
      * @return the number of messages in the cache
      */
     public int getMessageCount() {
         return _handles.size();
     }
 
     /***
      * Determines if this cache can be destroyed. A <code>QueueDestinationCache</code>
      * can be destroyed if there are no active consumers and: <ul> <li>the queue
      * is persistent and there are no messages</li> <li> the queue is temporary
      * and the corresponding connection is closed </li> </ul>
      *
      * @return <code>true</code> if the cache can be destroyed, otherwise
      *         <code>false</code>
      */
     public boolean canDestroy() {
         boolean destroy = false;
         if (!hasConsumers()) {
             JmsDestination queue = getDestination();
             if (queue.getPersistent() && getMessageCount() == 0) {
                 destroy = true;
             } else if (queue.isTemporaryDestination()) {
                 // check if there is a corresponding connection. If
                 // not, it has been closed, and the cache can be removed
                 long connectionId =
                         ((JmsTemporaryDestination) queue).getConnectionId();
                 if (_connections.getConnection(connectionId) == null) {
                     destroy = true;
                 }
             }
         }
         return destroy;
     }
 
     /***
      * Destroy this object.
      */
     public void destroy() {
         super.destroy();
         _browsers.clear();
     }
 
     /***
      * Initialise the cache. This removes all the expired messages, and then
      * retrieves all unacked messages from the database and stores them
      * locally.
      *
      * @throws JMSException if the cache can't be initialised
      */
     protected void init() throws JMSException {
         JmsDestination queue = getDestination();
 
         List handles;
         DatabaseService service = null;
         try {
             service = DatabaseService.getInstance();
             Connection connection = service.getConnection();
             service.getAdapter().removeExpiredMessageHandles(connection,
                     queue.getName());
             handles = service.getAdapter().getMessageHandles(connection, queue,
                     queue.getName());
         } catch (PersistenceException exception) {
             _log.error(exception, exception);
             try {
                 if (service != null) {
                     service.rollback();
                 }
             } catch (PersistenceException error) {
                 _log.error(error, error);
             }
             throw new JMSException(exception.getMessage());
         }
 
         Iterator iterator = handles.iterator();
         DefaultMessageCache cache = getMessageCache();
         while (iterator.hasNext()) {
             PersistentMessageHandle handle = (PersistentMessageHandle) iterator.next();
             String messageId = handle.getMessageId();
             MessageRef reference = cache.getMessageRef(messageId);
             if (reference == null) {
                 reference = new CachedMessageRef(messageId, true, cache);
             }
             cache.addMessageRef(reference);
             handle.reference(reference);
             handle.setDestinationCache(this);
             _handles.add(new QueueConsumerMessageHandle(handle));
 
             checkMessageExpiry(reference, handle.getExpiryTime());
         }
     }
 
     /***
      * Add a message, and notify any listeners.
      *
      * @param reference a reference to the message
      * @param message   the message
      * @param handle    the handle to add
      * @throws JMSException for any error
      */
     protected void addMessage(MessageRef reference, MessageImpl message,
                               MessageHandle handle) throws JMSException {
         addMessage(reference, message);
         _handles.add(handle);
 
         // notify any queue listeners that a message has arrived
         notifyQueueListeners(handle, message);
 
         // create a lease iff one is required
         checkMessageExpiry(reference, message);
     }
 
 
     /***
      * Notify queue browsers that a message has arrived.
      *
      * @param handle  a handle to the message
      * @param message the message
      * @throws JMSException if a browser fails to handle the message
      */
     protected void notifyQueueListeners(MessageHandle handle,
                                         MessageImpl message)
             throws JMSException {
         QueueBrowserEndpoint[] browsers =
                 (QueueBrowserEndpoint[]) _browsers.toArray(
                         new QueueBrowserEndpoint[0]);
 
         for (int index = 0; index < browsers.length; ++index) {
             QueueBrowserEndpoint browser = browsers[index];
             browser.messageAdded(handle, message);
         }
     }
 
     /***
      * Remove an expired non-peristent message, and notify any listeners.
      *
      * @param reference the reference to the expired message
      * @throws JMSException for any error
      */
     protected void messageExpired(MessageRef reference) throws JMSException {
         _handles.remove(reference.getMessageId());
         // @todo - notify browser
         super.messageExpired(reference);
     }
 
     /***
      * Remove an expired persistent message, and notify any listeners.
      *
      * @param reference the reference to the expired message
      * @throws JMSException         if a listener fails to handle the
      *                              expiration
      * @throws PersistenceException if there is a persistence related problem
      */
     protected void persistentMessageExpired(MessageRef reference)
             throws JMSException, PersistenceException {
         _handles.remove(reference.getMessageId());
         // @todo - notify browsers
         super.messageExpired(reference);
     }
 
     /***
      * Return the next QueueConsumerEndpoint that can consume the specified
      * message or null if there is none.
      *
      * @param message - the message to consume
      * @return the consumer who should receive this message, or null
      */
     private ConsumerEndpoint getConsumerForMessage(MessageImpl message) {
         ConsumerEndpoint result = null;
 
         ConsumerEndpoint[] consumers = getConsumerArray();
         final int size = consumers.length;
         if (size > 0) {
             synchronized (_lock) {
                 // roll over the consumer index if it is greater
                 // than the number of registered consumers
                 if ((_lastConsumerIndex + 1) > size) {
                     _lastConsumerIndex = 0;
                 }
 
                 // look over the list of consumers and return the
                 // first endpoint that can process this message
                 int index = _lastConsumerIndex;
                 do {
                     ConsumerEndpoint consumer = consumers[index];
                     // if the endpoint has a message listener registered
                     // or the endpoint is waiting for a message and the
                     // message satisfies the selector then return it to
                     // the client.
                     if ((consumer.isAsynchronous()
                             || consumer.isWaitingForMessage())
                             && consumer.selects(message)) {
                         _lastConsumerIndex = ++index;
                         result = consumer;
                         break;
                     }
 
                     // advance to the next consumer
                     if (++index >= size) {
                         index = 0;
                     }
                 } while (index != _lastConsumerIndex);
             }
         }
 
         return result;
     }
 
 }