/**
 * Copyright 2012 Apache Wave
 *
 * 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.waveprotocol.box.server.waveserver;

import com.google.common.util.concurrent.ListenableFuture;

import org.waveprotocol.wave.model.id.WaveletName;
import org.waveprotocol.wave.model.wave.ParticipantId;

/**
 * Provides a subscription service for changes to wavelets that can cause
 * modification of the per user wave view. It is an adapter interface for {@link WaveBus}.
 *
 * @author yurize@apache.org (Yuri Zelikov)
 */
public interface PerUserWaveViewBus {

  /**
   * Receives per user wave view bus messages.
   */
  interface Listener {

    /**
     * Notifies the subscriber of an user added to wavelet.
     *
     * @param waveletName the wavelet name.
     * @param participant the participant that was added.
     * @return the future that allows to be notified of the update completion.
     */
    ListenableFuture<Void> onParticipantAdded(WaveletName waveletName, ParticipantId participant);

    /**
     * Notifies the subscriber of an user removed from wavelet.
     *
     * @param waveletName the wavelet name.
     * @param participant the participant that was added.
     * @return the future that allows to be notified of the update completion.
     */
    ListenableFuture<Void> onParticipantRemoved(WaveletName waveletName, ParticipantId participant);

    /**
     * Notifies the subscriber of a new wavelet that should be indexed.
     *
     * @param waveletName the wavelet name.
     * @return the future that allows to be notified of the update completion.
     */
    ListenableFuture<Void> onWaveInit(WaveletName waveletName);
  }

  /**
   * Subscribes to the bus, if the subscriber is not already subscribed.
   */
  void addListener(Listener listener);

  /**
   * Unsubscribes from the bus, if the subscriber is currently subscribed.
   */
  void removeListener(Listener listener);
}