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/**
 * All rights reserved. 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.jivesoftware.smackx.provider;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.jivesoftware.smack.packet.PacketExtension;
import org.jivesoftware.smack.provider.PacketExtensionProvider;
import org.jivesoftware.smack.util.PacketParserUtils;
import org.jivesoftware.smackx.pubsub.provider.ItemProvider;
import org.jivesoftware.smackx.pubsub.provider.ItemsProvider;
import org.xmlpull.v1.XmlPullParser;

/**
 * 
 * This class simplifies parsing of embedded elements by using the 
 * Template Method Pattern.  
 * After extracting the current element attributes and content of any child elements, the template method 
 * ({@link #createReturnExtension(String, String, Map, List)} is called.  Subclasses
 * then override this method to create the specific return type.
 * 
 * To use this class, you simply register your subclasses as extension providers in the 
 * smack.properties file.  Then they will be automatically picked up and used to parse
 * any child elements.  
 * 
 * 
 * For example, given the following message
 * 
 * <message from='pubsub.shakespeare.lit' to='[email protected]' id='foo>
 *    <event xmlns='http://jabber.org/protocol/pubsub#event>
 *       <items node='princely_musings'>
 *          <item id='asdjkwei3i34234n356'>
 *             <entry xmlns='http://www.w3.org/2005/Atom'>
 *                <title>Soliloquy</title>
 *                <link rel='alternative' type='text/html'/>
 *                <id>tag:denmark.lit,2003:entry-32397</id>
 *             </entry>
 *          </item>
 *       </items>
 *    </event>
 * </message>
 * 
 * I would have a classes
 * {@link ItemsProvider} extends {@link EmbeddedExtensionProvider}
 * {@link ItemProvider} extends {@link EmbeddedExtensionProvider}
 * and
 * AtomProvider extends {@link PacketExtensionProvider}
 * 
 * These classes are then registered in the meta-inf/smack.providers file
 * as follows.
 * 
 *   <extensionProvider>
 *      <elementName>items</elementName>
 *      <namespace>http://jabber.org/protocol/pubsub#event</namespace>
 *      <className>org.jivesoftware.smackx.provider.ItemsEventProvider</className>
 *   </extensionProvider>
 *   <extensionProvider>
 *       <elementName>item</elementName>
 *       <namespace>http://jabber.org/protocol/pubsub#event</namespace>
 *       <className>org.jivesoftware.smackx.provider.ItemProvider</className>
 *   </extensionProvider>
 * 
 * 
 * 
 * @author Robin Collier
 */
abstract public class EmbeddedExtensionProvider implements PacketExtensionProvider
{

	final public PacketExtension parseExtension(XmlPullParser parser) throws Exception
	{
        String namespace = parser.getNamespace();
        String name = parser.getName();
        Map attMap = new HashMap();
        
        for(int i=0; i extensions = new ArrayList();
        
        do
        {
            int tag = parser.next();

            if (tag == XmlPullParser.START_TAG) 
            	extensions.add(PacketParserUtils.parsePacketExtension(parser.getName(), parser.getNamespace(), parser));
        } while (!name.equals(parser.getName()));

		return createReturnExtension(name, namespace, attMap, extensions);
	}

	abstract protected PacketExtension createReturnExtension(String currentElement, String currentNamespace, Map attributeMap, List content);
}