/**
 * 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.pubsub;

import org.jivesoftware.smack.packet.Message;
import org.jivesoftware.smackx.pubsub.provider.ItemProvider;

/**
 * This class represents an item that has been, or will be published to a pubsub
 * node. An <tt>Item</tt> has several properties that are dependent on the
 * configuration of the node to which it has been or will be published.
 * 
 * <h1>An Item received from a node (via {@link LeafNode#getItems()} or
 * {@link LeafNode#addItemEventListener(org.jivesoftware.smackx.pubsub.listener.ItemEventListener)}
 * </b>
 * <li>Will always have an id (either user or server generated) unless node
 * configuration has both {@link ConfigureForm#isPersistItems()} and
 * {@link ConfigureForm#isDeliverPayloads()}set to false.
 * <li>Will have a payload if the node configuration has
 * {@link ConfigureForm#isDeliverPayloads()} set to true, otherwise it will be
 * null.
 * 
 * <h1>An Item created to send to a node (via {@link LeafNode#send()} or
 * {@link LeafNode#publish()}</b>
 * <li>The id is optional, since the server will generate one if necessary, but
 * should be used if it is meaningful in the context of the node. This value
 * must be unique within the node that it is sent to, since resending an item
 * with the same id will overwrite the one that already exists if the items are
 * persisted.
 * <li>Will require payload if the node configuration has
 * {@link ConfigureForm#isDeliverPayloads()} set to true.
 * 
 * <p>
 * To customise the payload object being returned from the {@link #getPayload()}
 * method, you can add a custom parser as explained in {@link ItemProvider}.
 * 
 * @author Robin Collier
 */
public class Item extends NodeExtension {
	private String id;

	/**
	 * Create an empty <tt>Item</tt> with no id. This is a valid item for nodes
	 * which are configured so that {@link ConfigureForm#isDeliverPayloads()} is
	 * false. In most cases an id will be generated by the server. For nodes
	 * configured with {@link ConfigureForm#isDeliverPayloads()} and
	 * {@link ConfigureForm#isPersistItems()} set to false, no <tt>Item</tt> is
	 * sent to the node, you have to use {@link LeafNode#send()} or
	 * {@link LeafNode#publish()} methods in this case.
	 */
	public Item() {
		super(PubSubElementType.ITEM);
	}

	/**
	 * Create an <tt>Item</tt> with an id but no payload. This is a valid item
	 * for nodes which are configured so that
	 * {@link ConfigureForm#isDeliverPayloads()} is false.
	 * 
	 * @param itemId
	 *            The id if the item. It must be unique within the node unless
	 *            overwriting and existing item. Passing null is the equivalent
	 *            of calling {@link #Item()}.
	 */
	public Item(String itemId) {
		// The element type is actually irrelevant since we override
		// getNamespace() to return null
		super(PubSubElementType.ITEM);
		id = itemId;
	}

	/**
	 * Create an <tt>Item</tt> with an id and a node id.
	 * <p>
	 * <b>Note:</b> This is not valid for publishing an item to a node, only
	 * receiving from one as part of {@link Message}. If used to create an Item
	 * to publish (via {@link LeafNode#publish(Item)}, the server <i>may</i>
	 * return an error for an invalid packet.
	 * 
	 * @param itemId
	 *            The id of the item.
	 * @param nodeId
	 *            The id of the node which the item was published to.
	 */
	public Item(String itemId, String nodeId) {
		super(PubSubElementType.ITEM_EVENT, nodeId);
		id = itemId;
	}

	/**
	 * Get the item id. Unique to the node it is associated with.
	 * 
	 * @return The id
	 */
	public String getId() {
		return id;
	}

	@Override
	public String getNamespace() {
		return null;
	}

	@Override
	public String toString() {
		return getClass().getName() + " | Content [" + toXML() + "]";
	}

	@Override
	public String toXML() {
		final StringBuilder builder = new StringBuilder("<item");

		if (id != null) {
			builder.append(" id='");
			builder.append(id);
			builder.append("'");
		}

		if (getNode() != null) {
			builder.append(" node='");
			builder.append(getNode());
			builder.append("'");
		}
		builder.append("/>");

		return builder.toString();
	}
}