/**
 * $RCSfile: $
 * $Revision: $
 * $Date: $
 *
 * Copyright (C) 2006 Jive Software. All rights reserved.
 *
 * This software is published under the terms of the GNU Public License (GPL),
 * a copy of which is included in this distribution.
 */

package org.jivesoftware.openfire.pubsub;

import org.xmpp.packet.JID;
import org.xmpp.packet.Message;
import org.xmpp.packet.Packet;

import java.util.Collection;

/**
 * A PubSubService is responsible for keeping the hosted nodes by the service, the default
 * configuration to use for newly created nodes and specify the policy to use regarding
 * node management.<p>
 *
 * Implementations of PubSubService are expected to collaborate with a {@link PubSubEngine}
 * that will take care of handling packets sent to the service.<p>
 *
 * The separation between <code>PubSubService</code> and <code>PubSubEngine</code> allows to
 * reuse the handling of packets and at the same time be able to create different pubsub
 * services with different configurations. Examples of different pubsub services are:
 * JEP-60: Publish-Subscribe and JEP-163: Personal Eventing Protocol.
 *
 * @author Matt Tucker
 */
public interface PubSubService {

    /**
     * Returns the XMPP address of the service.
     *
     * @return the XMPP address of the service.
     */
    JID getAddress();

    /**
     * Returns a String that uniquely identifies this pubsub service. This information is
     * being used when storing node information in the database so it's possible to have
     * nodes with the same ID but under different pubsub services.
     *
     * @return a String that uniquely identifies this pubsub service.
     */
    String getServiceID();

    /**
     * Returns true if the pubsub service allows the specified user to create nodes.
     *
     * @param creator the JID of the entity trying to create a new node.
     * @return true if the pubsub service allows the specified user to create nodes.
     */
    boolean canCreateNode(JID creator);

    /**
     * Returns true if the specified user is a sysadmin of the pubsub service or has
     * admin privileges.
     *
     * @param user the user to check if he has admin privileges.
     * @return true if the specified user is a sysadmin of the pubsub service or has
     *         admin privileges.
     */
    boolean isServiceAdmin(JID user);

    /**
     * Returns true if the pubsub service allows users to create nodes without specifying
     * the node ID. The service will create a random node ID and assigne it to the node.
     *
     * @return true if the pubsub service allows users to create nodes without specifying
     *         the node ID.
     */
    boolean isInstantNodeSupported();

    /**
     * Returns true if the pubsub service supports collection nodes. When collection nodes is
     * supported it is possible to create hierarchy of nodes where a {@link CollectionNode}
     * may only hold children nodes of type {@link CollectionNode} or {@link LeafNode}. On the
     * other hand, {@link LeafNode} can only hold {@link PublishedItem}.
     *
     * @return true if the pubsub service supports collection nodes.
     */
    boolean isCollectionNodesSupported();

    /**
     * Returns the {@link CollectionNode} that acts as the root node of the entire
     * node hierarchy. The returned node does not have a node identifier. If collection
     * nodes is not supported then return <tt>null</tt>.
     *
     * @return the CollectionNode that acts as the root node of the entire node hierarchy
     *         or <tt>null</tt> if collection nodes is not supported.
     */
    CollectionNode getRootCollectionNode();

    /**
     * Returns the {@link Node} that matches the specified node ID or <tt>null</tt> if
     * none was found.
     *
     * @param nodeID the ID that uniquely identifies the node in the pubsub service.
     * @return the Node that matches the specified node ID or <tt>null</tt> if none was found.
     */
    Node getNode(String nodeID);

    /**
     * Retuns the collection of nodes hosted by the pubsub service. The collection does
     * not support modifications.
     *
     * @return the collection of nodes hosted by the pubsub service.
     */
    Collection<Node> getNodes();

    /**
     * Adds an already persistent node to the service.
     *
     * @param node the persistent node to add to the service.
     */
    void addNode(Node node);

    /**
     * Removes the specified node from the service. Most probaly the node was deleted from
     * the database as well.<p>
     *
     * A future version may support unloading of inactive nodes even though they may still
     * exist in the database.
     *
     * @param nodeID the ID that uniquely identifies the node in the pubsub service.
     */
    void removeNode(String nodeID);

    /**
     * Broadcasts the specified Message containing an event notification to a list
     * of subscribers to the specified node. Each message being sent has to have a unique
     * ID value so that the service can properly track any notification-related errors
     * that may occur.
     *
     * @param node the node that triggered the event notification.
     * @param message the message containing the event notification.
     * @param jids the list of entities to get the event notification.
     */
    void broadcast(Node node, Message message, Collection<JID> jids);

    /**
     * Sends the specified packet.
     *
     * @param packet the packet to send.
     */
    void send(Packet packet);

    /**
     * Sends the specified Message containing an event notification to a specific
     * subscriber of the specified node. The message being sent has to have a unique
     * ID value so that the service can properly track any notification-related errors
     * that may occur.
     *
     * @param node the node that triggered the event notification.
     * @param message the message containing the event notification.
     * @param jid the entity to get the event notification.
     */
    void sendNotification(Node node, Message message, JID jid);

    /**
     * Returns the default node configuration for the specified node type or <tt>null</tt>
     * if the specified node type is not supported by the service.
     *
     * @param leafType true when requesting default configuration of leaf nodes
     * @return the default node configuration for the specified node type or <tt>null</tt>
     *         if the specified node type is not supported by the service.
     */
    DefaultNodeConfiguration getDefaultNodeConfiguration(boolean leafType);

    /**
     * Returns the show values of the last know presence of all connected resources of the
     * specified subscriber. When the subscriber JID is a bare JID then the answered collection
     * will have many entries one for each connected resource. Moreover, if the user
     * is offline then an empty collectin is returned. Available show status is represented
     * by a <tt>online</tt> value. The rest of the possible show values as defined in RFC 3921.
     *
     * @param subscriber the JID of the subscriber. This is not the JID of the affiliate.
     * @return an empty collection when offline. Otherwise, a collection with the show value
     *         of each connected resource.
     */
    Collection<String> getShowPresences(JID subscriber);

    /**
     * Requests the pubsub service to subscribe to the presence of the user. If the service
     * has already subscribed to the user's presence then do nothing.
     *
     * @param node the node that originated the subscription request.
     * @param user the JID of the affiliate to subscribe to his presence.
     */
    void presenceSubscriptionRequired(Node node, JID user);

    /**
     * Requests the pubsub service to unsubscribe from the presence of the user. If the service
     * was not subscribed to the user's presence or any node still requires to be subscribed to
     * the user presence then do nothing.
     *
     * @param node the node that originated the unsubscription request.
     * @param user the JID of the affiliate to unsubscribe from his presence.
     */
    void presenceSubscriptionNotRequired(Node node, JID user);

    /**
     * Returns true if a user may have more than one subscription with the node. When
     * multiple subscriptions is enabled each subscription request, event notification and
     * unsubscription request should include a <tt>subid</tt> attribute.
     *
     * @return true if a user may have more than one subscription with the node.
     */
    boolean isMultipleSubscriptionsEnabled();

    /**
     * Adds the item to the queue of items to add to the database. The queue is going
     * to be processed by another thread.
     *
     * @param newItem the item to add to the database.
     */
    void queueItemToAdd(PublishedItem newItem);

    /**
     * Adds the item to the queue of items to remove from the database. The queue is going
     * to be processed by another thread.
     *
     * @param removedItem the item to remove from the database.
     */
    void queueItemToRemove(PublishedItem removedItem);
}
