Smack/smack-extensions/src/main/java/org/jivesoftware/smackx/pubsub/ItemsExtension.java

/**
 *
 * Copyright 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.jivesoftware.smackx.pubsub;

import java.util.List;

import org.jivesoftware.smack.packet.ExtensionElement;
import org.jivesoftware.smack.packet.NamedElement;
import org.jivesoftware.smack.packet.XmlElement;
import org.jivesoftware.smack.util.XmlStringBuilder;

/**
 * This class is used for multiple purposes.
 * <ul>
 * <li>It can represent an event containing a list of items that have been published
 * <li>It can represent an event containing a list of retracted (deleted) items.
 * <li>It can represent a request to delete a list of items.
 * <li>It can represent a request to get existing items.
 * </ul>
 *
 * <p><b>Please note, this class is used for internal purposes, and is not required for usage of
 * pubsub functionality.</b></p>
 *
 * @author Robin Collier
 */
public class ItemsExtension extends NodeExtension implements EmbeddedPacketExtension {
    protected ItemsElementType type;
    protected Boolean notify;
    protected List<? extends NamedElement> items;

    public enum ItemsElementType {
        /** An items element, which has an optional <b>max_items</b> attribute when requesting items. */
        items(PubSubElementType.ITEMS, "max_items"),

        /** A retract element, which has an optional <b>notify</b> attribute when publishing deletions. */
        retract(PubSubElementType.RETRACT, "notify");

        private final PubSubElementType elem;
        private final String att;

        ItemsElementType(PubSubElementType nodeElement, String attribute) {
            elem = nodeElement;
            att = attribute;
        }

        public PubSubElementType getNodeElement() {
            return elem;
        }

        public String getElementAttribute() {
            return att;
        }
    }

    /**
     * Construct an instance with a list representing items that have been published or deleted.
     *
     * <p>Valid scenarios are:</p>
     * <ul>
     * <li>Request items from node - itemsType = {@link ItemsElementType#items}, items = list of {@link Item} and an
     * optional value for the <b>max_items</b> attribute.
     * <li>Request to delete items - itemsType = {@link ItemsElementType#retract}, items = list of {@link Item} containing
     * only id's and an optional value for the <b>notify</b> attribute.
     * <li>Items published event - itemsType = {@link ItemsElementType#items}, items = list of {@link Item} and
     * attributeValue = <code>null</code>
     * <li>Items deleted event -  itemsType = {@link ItemsElementType#items}, items = list of {@link RetractItem} and
     * attributeValue = <code>null</code>
     * </ul>
     *
     * @param itemsType Type of representation
     * @param nodeId The node to which the items are being sent or deleted
     * @param items The list of {@link Item} or {@link RetractItem}
     */
    public ItemsExtension(ItemsElementType itemsType, String nodeId, List<? extends NamedElement> items) {
        super(itemsType.getNodeElement(), nodeId);
        type = itemsType;
        this.items = items;
    }

    /**
     * Construct an instance with a list representing items that have been published or deleted.
     *
     * <p>Valid scenarios are:</p>
     * <ul>
     * <li>Request items from node - itemsType = {@link ItemsElementType#items}, items = list of {@link Item} and an
     * optional value for the <b>max_items</b> attribute.
     * <li>Request to delete items - itemsType = {@link ItemsElementType#retract}, items = list of {@link Item} containing
     * only id's and an optional value for the <b>notify</b> attribute.
     * <li>Items published event - itemsType = {@link ItemsElementType#items}, items = list of {@link Item} and
     * attributeValue = <code>null</code>
     * <li>Items deleted event -  itemsType = {@link ItemsElementType#items}, items = list of {@link RetractItem} and
     * attributeValue = <code>null</code>
     * </ul>
     *
     * @param nodeId The node to which the items are being sent or deleted
     * @param items The list of {@link Item} or {@link RetractItem}
     * @param notify TODO javadoc me please
     */
    public ItemsExtension(String nodeId, List<? extends ExtensionElement> items, boolean notify) {
        super(ItemsElementType.retract.getNodeElement(), nodeId);
        type = ItemsElementType.retract;
        this.items = items;
        this.notify = notify;
    }

    /**
     * Get the type of element.
     *
     * @return The element type
     */
    public ItemsElementType getItemsElementType() {
        return type;
    }

    @Override
    @SuppressWarnings("unchecked")
    public List<XmlElement> getExtensions() {
        return (List<XmlElement>) getItems();
    }

    /**
     * Gets the items related to the type of request or event.
     *
     * @return List of {@link Item}, {@link RetractItem}, or null
     */
    // TODO: Shouldn't this return List<Item>? Why is RetractItem not a subtype of item?
    public List<? extends NamedElement> getItems() {
        return items;
    }

    /**
     * Gets the value of the optional attribute related to the {@link ItemsElementType}.
     *
     * @return The attribute value
     */
    public boolean getNotify() {
        return notify;
    }

    @Override
    protected void addXml(XmlStringBuilder xml) {
        if ((items == null) || (items.size() == 0)) {
            xml.closeEmptyElement();
            return;
        }

        if (notify != null) {
            xml.attribute(type.getElementAttribute(), notify);
            xml.rightAngleBracket();
        } else {
            xml.rightAngleBracket();
            xml.append(items);
        }

        xml.closeElement(this);
    }

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

}