package org.apache.helix.participant;
   
   /*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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.
   */
  
  import java.util.List;
  
  import org.apache.helix.HelixManager;
  import org.apache.helix.NotificationContext;
  import org.apache.helix.HelixConstants.ChangeType;
  import org.apache.helix.PropertyKey.Builder;
  import org.apache.helix.model.Message;
  import org.apache.helix.participant.statemachine.StateModel;
  import org.apache.helix.participant.statemachine.StateModelInfo;
  import org.apache.helix.participant.statemachine.Transition;
  import org.apache.log4j.Logger;
  
  
  @StateModelInfo(initialState = "OFFLINE", states = { "LEADER", "STANDBY" })
  public class GenericLeaderStandbyModel extends StateModel
  {
    private static Logger LOG = Logger.getLogger(GenericLeaderStandbyModel.class);
  
    private final CustomCodeInvoker _particHolder;
    private final List<ChangeType> _notificationTypes;
  
    public GenericLeaderStandbyModel(CustomCodeCallbackHandler callback, 
                                       List<ChangeType> notificationTypes,
                                       String partitionKey)
    {
      _particHolder = new CustomCodeInvoker(callback, partitionKey);
      _notificationTypes = notificationTypes;
    }
  
    @Transition(to="STANDBY",from="OFFLINE")
    public void onBecomeStandbyFromOffline(Message message, NotificationContext context)
    {
      LOG.info("Become STANDBY from OFFLINE");
    }
  
    @Transition(to="LEADER",from="STANDBY")
    public void onBecomeLeaderFromStandby(Message message, NotificationContext context)
        throws Exception
    {
      LOG.info("Become LEADER from STANDBY");
      HelixManager manager = context.getManager();
      if (manager == null)
      {
        throw new IllegalArgumentException("Require HelixManager in notification conext");
      }
      for (ChangeType notificationType : _notificationTypes)
      {
        if (notificationType == ChangeType.LIVE_INSTANCE)
        {
          manager.addLiveInstanceChangeListener(_particHolder);
        }
        else if (notificationType == ChangeType.CONFIG)
        {
          manager.addConfigChangeListener(_particHolder);
        }
        else if (notificationType == ChangeType.EXTERNAL_VIEW)
        {
          manager.addExternalViewChangeListener(_particHolder);
        }
        else
        {
          LOG.error("Unsupport notificationType:" + notificationType.toString());
        }
      }
    }
  
    @Transition(to="STANDBY",from="LEADER")
    public void onBecomeStandbyFromLeader(Message message, NotificationContext context)
    {
      LOG.info("Become STANDBY from LEADER");
      HelixManager manager = context.getManager();
      if (manager == null)
      {
        throw new IllegalArgumentException("Require HelixManager in notification conext");
      }
      
      Builder keyBuilder = new Builder(manager.getClusterName());
      for (ChangeType notificationType : _notificationTypes)
     {
       if (notificationType == ChangeType.LIVE_INSTANCE)
       {
         manager.removeListener(keyBuilder.liveInstances(), _particHolder);
       }
       else if (notificationType == ChangeType.CONFIG)
       {
         manager.removeListener(keyBuilder.instanceConfigs(), _particHolder);
       }
       else if (notificationType == ChangeType.EXTERNAL_VIEW)
       {
         manager.removeListener(keyBuilder.externalViews(), _particHolder);
       }
       else
       {
         LOG.error("Unsupport notificationType:" + notificationType.toString());
       }
     }
   }
 
   @Transition(to="OFFLINE",from="STANDBY")
   public void onBecomeOfflineFromStandby(Message message, NotificationContext context)
   {
     LOG.info("Become OFFLINE from STANDBY");
   }
 }