/**
 * $RCSfile$
 * $Revision: 7071 $
 * $Date: 2007-02-11 18:59:05 -0600 (Sun, 11 Feb 2007) $
 *
 * Copyright 2003-2007 Jive Software.
 *
 * 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.smack.packet;

import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

/**
 * Default implementation of the PacketExtension interface. Unless a
 * PacketExtensionProvider is registered with
 * {@link org.jivesoftware.smack.provider.ProviderManager ProviderManager},
 * instances of this class will be returned when getting packet extensions.
 * <p>
 * 
 * This class provides a very simple representation of an XML sub-document. Each
 * element is a key in a Map with its CDATA being the value. For example, given
 * the following XML sub-document:
 * 
 * <pre>
 * <foo xmlns="http://bar.com">
 *     <color>blue</color>
 *     <food>pizza</food>
 * </foo>
 * </pre>
 * 
 * In this case, getValue("color") would return "blue", and getValue("food")
 * would return "pizza". This parsing mechanism mechanism is very simplistic and
 * will not work as desired in all cases (for example, if some of the elements
 * have attributes. In those cases, a custom PacketExtensionProvider should be
 * used.
 * 
 * @author Matt Tucker
 */
public class DefaultPacketExtension implements PacketExtension {

	private final String elementName;
	private final String namespace;
	private Map<String, String> map;

	/**
	 * Creates a new generic packet extension.
	 * 
	 * @param elementName
	 *            the name of the element of the XML sub-document.
	 * @param namespace
	 *            the namespace of the element.
	 */
	public DefaultPacketExtension(String elementName, String namespace) {
		this.elementName = elementName;
		this.namespace = namespace;
	}

	/**
	 * Returns the XML element name of the extension sub-packet root element.
	 * 
	 * @return the XML element name of the packet extension.
	 */
	@Override
	public String getElementName() {
		return elementName;
	}

	/**
	 * Returns an unmodifiable collection of the names that can be used to get
	 * values of the packet extension.
	 * 
	 * @return the names.
	 */
	public synchronized Collection<String> getNames() {
		if (map == null) {
			return Collections.emptySet();
		}
		return Collections.unmodifiableSet(new HashMap<String, String>(map)
				.keySet());
	}

	/**
	 * Returns the XML namespace of the extension sub-packet root element.
	 * 
	 * @return the XML namespace of the packet extension.
	 */
	@Override
	public String getNamespace() {
		return namespace;
	}

	/**
	 * Returns a packet extension value given a name.
	 * 
	 * @param name
	 *            the name.
	 * @return the value.
	 */
	public synchronized String getValue(String name) {
		if (map == null) {
			return null;
		}
		return map.get(name);
	}

	/**
	 * Sets a packet extension value using the given name.
	 * 
	 * @param name
	 *            the name.
	 * @param value
	 *            the value.
	 */
	public synchronized void setValue(String name, String value) {
		if (map == null) {
			map = new HashMap<String, String>();
		}
		map.put(name, value);
	}

	@Override
	public String toXML() {
		final StringBuilder buf = new StringBuilder();
		buf.append("<").append(elementName).append(" xmlns=\"")
				.append(namespace).append("\">");
		for (final String name : getNames()) {
			final String value = getValue(name);
			buf.append("<").append(name).append(">");
			buf.append(value);
			buf.append("</").append(name).append(">");
		}
		buf.append("</").append(elementName).append(">");
		return buf.toString();
	}
}