/*
 * Copyright 2002-2009 the original author or authors.
 *
 * Licensed 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.springframework.jms.support.destination;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import javax.jms.Destination;
import javax.jms.JMSException;
import javax.jms.Queue;
import javax.jms.Session;
import javax.jms.Topic;
import javax.naming.NamingException;

import org.springframework.jndi.JndiLocatorSupport;
import org.springframework.util.Assert;

/**
 * {@link DestinationResolver} implementation which interprets destination names
 * as JNDI locations (with a configurable fallback strategy).
 *
 * <p>Allows for customizing the JNDI environment if necessary, for example
 * specifying appropriate JNDI environment properties.
 *
 * <p>Dynamic queues and topics get cached by destination name. As a consequence,
 * you need to use unique destination names across both queues and topics.
 * Caching can be turned off through the {@link #setCache "cache"} flag.
 *
 * <p>Note that the fallback to resolution of dynamic destinations
 * is turned <i>off</i> by default. Switch the
 * {@link #setFallbackToDynamicDestination "fallbackToDynamicDestination"}
 * flag on to enable this functionality.
 *
 * @author Mark Pollack
 * @author Juergen Hoeller
 * @since 1.1
 * @see #setJndiTemplate
 * @see #setJndiEnvironment
 * @see #setCache
 * @see #setFallbackToDynamicDestination
 */
public class JndiDestinationResolver extends JndiLocatorSupport implements CachingDestinationResolver {

	private boolean cache = true;

	private boolean fallbackToDynamicDestination = false;

	private DestinationResolver dynamicDestinationResolver = new DynamicDestinationResolver();

	private final Map<String, Destination> destinationCache = new ConcurrentHashMap<String, Destination>();


	/**
	 * Set whether to cache resolved destinations. Default is "true".
	 * <p>This flag can be turned off to re-lookup a destination for each operation,
	 * which allows for hot restarting of destinations. This is mainly useful
	 * during development.
	 * <p>Note that dynamic queues and topics get cached by destination name.
	 * As a consequence, you need to use unique destination names across both
	 * queues and topics.
	 */
	public void setCache(boolean cache) {
		this.cache = cache;
	}

	/**
	 * Set whether this resolver is supposed to create dynamic destinations
	 * if the destination name is not found in JNDI. Default is "false".
	 * <p>Turn this flag on to enable transparent fallback to dynamic destinations.
	 * @see #setDynamicDestinationResolver
	 */
	public void setFallbackToDynamicDestination(boolean fallbackToDynamicDestination) {
		this.fallbackToDynamicDestination = fallbackToDynamicDestination;
	}

	/**
	 * Set the {@link DestinationResolver} to use when falling back to dynamic
	 * destinations.
	 * <p>The default is Spring's standard {@link DynamicDestinationResolver}.
	 * @see #setFallbackToDynamicDestination
	 * @see DynamicDestinationResolver
	 */
	public void setDynamicDestinationResolver(DestinationResolver dynamicDestinationResolver) {
		this.dynamicDestinationResolver = dynamicDestinationResolver;
	}


	public Destination resolveDestinationName(Session session, String destinationName, boolean pubSubDomain)
			throws JMSException {

		Assert.notNull(destinationName, "Destination name must not be null");
		Destination dest = this.destinationCache.get(destinationName);
		if (dest != null) {
			validateDestination(dest, destinationName, pubSubDomain);
		}
		else {
			try {
				dest = lookup(destinationName, Destination.class);
				validateDestination(dest, destinationName, pubSubDomain);
			}
			catch (NamingException ex) {
				if (logger.isDebugEnabled()) {
					logger.debug("Destination [" + destinationName + "] not found in JNDI", ex);
				}
				if (this.fallbackToDynamicDestination) {
					dest = this.dynamicDestinationResolver.resolveDestinationName(session, destinationName, pubSubDomain);
				}
				else {
					throw new DestinationResolutionException(
							"Destination [" + destinationName + "] not found in JNDI", ex);
				}
			}
			if (this.cache) {
				this.destinationCache.put(destinationName, dest);
			}
		}
		return dest;
	}

	/**
	 * Validate the given Destination object, checking whether it matches
	 * the expected type.
	 * @param destination the Destination object to validate
	 * @param destinationName the name of the destination
	 * @param pubSubDomain <code>true</code> if a Topic is expected,
	 * <code>false</code> in case of a Queue
	 */
	protected void validateDestination(Destination destination, String destinationName, boolean pubSubDomain) {
		Class targetClass = Queue.class;
		if (pubSubDomain) {
			targetClass = Topic.class;
		}
		if (!targetClass.isInstance(destination)) {
			throw new DestinationResolutionException(
					"Destination [" + destinationName + "] is not of expected type [" + targetClass.getName() + "]");
		}
	}


	public void removeFromCache(String destinationName) {
		this.destinationCache.remove(destinationName);
	}

	public void clearCache() {
		this.destinationCache.clear();
	}

}
