/**
 * 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 2000-2005 (C) Exoffice Technologies Inc. All Rights Reserved.
 */
package org.exolab.jms.messagemgr;

import java.sql.Connection;
import java.util.Date;
import java.util.HashMap;
import javax.jms.InvalidDestinationException;
import javax.jms.JMSException;
import javax.jms.DeliveryMode;
import javax.jms.Destination;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.exolab.jms.client.JmsDestination;
import org.exolab.jms.message.MessageImpl;
import org.exolab.jms.persistence.DatabaseService;
import org.exolab.jms.persistence.PersistenceException;
import org.exolab.jms.persistence.SQLHelper;
import org.exolab.jms.service.BasicService;
import org.exolab.jms.service.ServiceException;


/**
 * This is the active message handling component within the JMS server. Messages
 * are passed in and added to the appropriate dispatchers for delivery to the
 * clients.
 *
 * @author <a href="mailto:mourikis@intalio.com">Jim Mourikis</a>
 * @author <a href="mailto:tma@netspace.net.au">Tim Anderson</a>
 * @version $Revision: 1.2 $ $Date: 2005/03/18 03:58:39 $
 */
public class MessageMgr extends BasicService {

    /**
     * The service name of the message manager
     */
    private final static String MM_SERVICE_NAME = "MessageManager";

    /**
     * Caches the singleton instance of the message manager.
     */
    private static MessageMgr _instance;

    /**
     * used to synchronise the singleton construction
     */
    private static final Object _block = new Object();

    /**
     * Maintain a list of registered MessageManagerEventListener objects, that
     * get notified when certain events occur in the MessageManager
     */
    private transient HashMap _listeners = new HashMap(1023);

    /**
     * The sequence number generator is used to differentiate messages arriving
     * on the same millisecond
     */
    private long _sequenceNumberGenerator = 0;

    /**
     * The logger
     */
    private static final Log _log = LogFactory.getLog(MessageMgr.class);


    /**
     * Create and return an instance of the singleton. If the singleton already
     * exists then simply return it. If there is a problem creating the
     * singleton then throw an exception
     *
     * @return MessageMgr - the singleton instance
     */
    public static MessageMgr createInstance() {
        if (_instance == null) {
            synchronized (_block) {
                if (_instance == null) {
                    _instance = new MessageMgr();
                }
            }
        }
        return _instance;
    }

    /**
     * Return an instance to the MessageMgr singleton. This method assumes that
     * the singleton has already been created with a call to {@link
     * #createInstance}
     *
     * @return MessageMgr
     */
    public static MessageMgr instance() {
        return _instance;
    }

    /**
     * Construct a new <code>MessageMgr</code>
     */
    private MessageMgr() {
        super(MM_SERVICE_NAME);
    }

    // ovverride BasicService.start
    public void start() throws ServiceException {
        try {
            DestinationManager.createInstance();
            ConsumerManager.createInstance();
        } catch (ServiceException exception) {
            throw exception;
        } catch (Exception exception) {
            String msg = "Failed to start MessageMgr";
            _log.error(msg, exception);
            throw new ServiceException(msg + ":" + exception);
        }
    }

    // implement BasicService.run
    public void run() {
        // do nothing
    }

    // override BasicService.stop
    public synchronized void stop() throws ServiceException {
        try {
            // destroy the consumer manager.
            ConsumerManager.instance().destroy();

            // destroy the destination manager.
            DestinationManager.instance().destroy();

            // clear state
            _listeners.clear();
        } catch (Exception error) {
            error.printStackTrace();
            throw new ServiceException("Failed to stop MessageMgr : " +
                                       error.toString());
        }

        // clear the static reference
        synchronized (_block) {
            _instance = null;

        }
    }

    /**
     * Create the specified destination. The destination is a container for
     * messages and consumers. Consumers listen for messages posted on a
     * particular destination.
     * <p/>
     * This can be called multiple times without any side effects. If the
     * destination is null then it throws a JMSException
     *
     * @param destination - create this destination
     * @throws JMSException - if the params is null
     */
    public void addDestination(JmsDestination destination)
            throws JMSException {

        // check the methods preconditions
        if (destination == null) {
            throw new JMSException("Call to addDestination with null object");
        }

        DestinationManager.instance().getDestinationCache(destination);
    }

    /**
     * Add a message
     *
     * @param message the message to add
     * @throws JMSException if the message cannot be added
     */
    public void add(MessageImpl message) throws JMSException {
        prepare(message);

        JmsDestination destination =
                (JmsDestination) message.getJMSDestination();

        // if the message's delivery mode is PERSISTENT, and the destination
        // is also persistent, then then process it accordingly, otherwise use
        // the non-persistent quality of service
        if (message.getJMSDeliveryMode() == DeliveryMode.PERSISTENT
                && DestinationManager.instance().isPersistent(destination)) {
            addPersistentMessage(message);
        } else {
            addNonPersistentMessage(message);
        }
    }

    /**
     * Add a message
     * <p/>
     * Note that this method is called exclusively by the
     * {@link ResourceManager} and should not be used for any other purpose.
     *
     * @param connection this is the database connection that is used
     * @param message    the message to add
     * @throws JMSException thrown if  there is a problem processing msg