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.ArrayList;
  import java.util.Arrays;
  import java.util.List;
  
  import org.apache.helix.HelixDataAccessor;
  import org.apache.helix.HelixManager;
  import org.apache.helix.HelixConstants.ChangeType;
  import org.apache.helix.HelixConstants.StateModelToken;
  import org.apache.helix.PropertyKey.Builder;
  import org.apache.helix.manager.zk.ZKHelixDataAccessor;
  import org.apache.helix.manager.zk.ZNRecordSerializer;
  import org.apache.helix.manager.zk.ZkBaseDataAccessor;
  import org.apache.helix.manager.zk.ZkClient;
  import org.apache.helix.model.IdealState;
  import org.apache.helix.model.IdealState.IdealStateModeProperty;
  import org.apache.log4j.Logger;
  
  
  /**
   * This provides the ability for users to run a custom code in exactly one
   * process using a LeaderStandBy state model. <br/>
   * A typical use case is when one uses CUSTOMIZED ideal state mode where the
   * assignment of partition to nodes needs to change dynamically as the nodes go
   * online/offline.<br/>
   * <code>
   * HelixCustomCodeRunner runner = new HelixCustomCodeRunner(manager,ZK_ADDR);
   * runner
   *  .invoke(_callback)
   *  .on(ChangeType.LIVE_INSTANCE, ChangeType.IdealState)
   *  .usingLeaderStandbyModel("someUniqueId")
   *  .run()
   * </code>
   *
   *
   */
  public class HelixCustomCodeRunner
  {
    private static final String LEADER_STANDBY = "LeaderStandby";
    private static Logger LOG = Logger.getLogger(HelixCustomCodeRunner.class);
    private static String PARTICIPANT_LEADER = "PARTICIPANT_LEADER";
  
    private CustomCodeCallbackHandler _callback;
    private List<ChangeType> _notificationTypes;
    private String _resourceName;
    private final HelixManager _manager;
    private final String _zkAddr;
    private GenericLeaderStandbyStateModelFactory _stateModelFty;
  
    /**
     * Constructs a HelixCustomCodeRunner that will run exactly in one place
     *
     * @param manager
     * @param zkAddr
     */
    public HelixCustomCodeRunner(HelixManager manager, String zkAddr)
    {
      _manager = manager;
      _zkAddr = zkAddr;
    }
  
    /**
     * callback to invoke when there is a change in cluster state specified by on(
     * notificationTypes) This callback must be idempotent which means they should
     * not depend on what changed instead simply read the cluster data and act on
     * it.
     *
     * @param callback
     * @return
     */
    public HelixCustomCodeRunner invoke(CustomCodeCallbackHandler callback)
    {
      _callback = callback;
      return this;
    }
  
    /**
     * ChangeTypes interested in, ParticipantLeaderCallback.callback method will
     * be invoked on the
    *
    * @param notificationTypes
    * @return
    */
   public HelixCustomCodeRunner on(ChangeType... notificationTypes)
   {
     _notificationTypes = Arrays.asList(notificationTypes);
     return this;
   }
 
   public HelixCustomCodeRunner usingLeaderStandbyModel(String id)
   {
     _resourceName = PARTICIPANT_LEADER + "_" + id;
     return this;
   }
 
   /**
    * This method will be invoked when there is a change in any subscribed
    * notificationTypes
    *
    * @throws Exception
    */
   public void start() throws Exception
   {
     if (_callback == null || _notificationTypes == null || _notificationTypes.size() == 0
         || _resourceName == null)
     {
       throw new IllegalArgumentException("Require callback | notificationTypes | resourceName");
     }
 
     LOG.info("Register participantLeader on " + _notificationTypes + " using " + _resourceName);
 
     _stateModelFty = new GenericLeaderStandbyStateModelFactory(_callback, _notificationTypes);
 
     StateMachineEngine stateMach = _manager.getStateMachineEngine();
     stateMach.registerStateModelFactory(LEADER_STANDBY, _stateModelFty, _resourceName);
     ZkClient zkClient = null;
     try
     {
       // manually add ideal state for participant leader using LeaderStandby
       // model
 
       zkClient = new ZkClient(_zkAddr, ZkClient.DEFAULT_CONNECTION_TIMEOUT);
       zkClient.setZkSerializer(new ZNRecordSerializer());
       HelixDataAccessor accessor = new ZKHelixDataAccessor(_manager.getClusterName(), new ZkBaseDataAccessor(zkClient));
       Builder keyBuilder = accessor.keyBuilder();
 
       IdealState idealState = new IdealState(_resourceName);
       idealState.setIdealStateMode(IdealStateModeProperty.AUTO.toString());
       idealState.setReplicas(StateModelToken.ANY_LIVEINSTANCE.toString());
       idealState.setNumPartitions(1);
       idealState.setStateModelDefRef(LEADER_STANDBY);
       idealState.setStateModelFactoryName(_resourceName);
       List<String> prefList = new ArrayList<String>(Arrays.asList(StateModelToken.ANY_LIVEINSTANCE
           .toString()));
       idealState.getRecord().setListField(_resourceName + "_0", prefList);
 
       List<String> idealStates = accessor.getChildNames(keyBuilder.idealStates());
       while (idealStates == null || !idealStates.contains(_resourceName))
       {
         accessor.setProperty(keyBuilder.idealStates(_resourceName), idealState);
         idealStates = accessor.getChildNames(keyBuilder.idealStates());
       }
 
       LOG.info("Set idealState for participantLeader:" + _resourceName + ", idealState:"
           + idealState);
     } finally
     {
       if (zkClient != null && zkClient.getConnection() != null)
 
       {
         zkClient.close();
       }
     }
 
   }
 
   /**
    * Stop customer code runner
    */
   public void stop()
   {
     LOG.info("Removing stateModelFactory for " + _resourceName);
     _manager.getStateMachineEngine().removeStateModelFactory(LEADER_STANDBY, _stateModelFty,
         _resourceName);
   }
 }