package org.apache.helix.controller;
   
   /*
    * 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.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.TreeMap;
  import java.util.TreeSet;
  
  import org.apache.helix.ZNRecord;
  import org.apache.helix.model.Message;
  import org.apache.helix.model.CurrentState.CurrentStateProperty;
  import org.apache.log4j.Logger;
  
  
  /*
   * ZKRoutingInfoProvider keeps a copy of the routing table. Given a partition id,
   * it will return
   *
   * 1. The list of partition that can be read
   * 2. the master partition, for write operation
   *
   * The routing table is constructed from the currentState of each storage nodes.
   * The current state is a list of following pairs: partition-id:State(MASTER / SLAVE)
   *
   * TODO: move the code as part of router process
   * TODO: add listeners to node current state changes
   * */
  public class ExternalViewGenerator
  {
    static Logger _logger = Logger.getLogger(ExternalViewGenerator.class);
  
    /*
     * Given a list of external view ZNRecord nodes(one for each cluster),
     * calculate the routing map.
     *
     * The format of the routing map is like this:
     *
     * Map<String, Map<String, Set<String>>> maps from a partitionName to its
     * states Map<String, List<String>> The second Map maps from a state
     * ("MASTER", "SLAVE"...) to a list of nodeNames
     *
     * So that the we can query the map for the list of nodes by providing the
     * partition name and the expected state.
     */
    public Map<String, Map<String, Set<String>>> getRouterMapFromExternalView(
        List<ZNRecord> externalViewList)
    {
      Map<String, Map<String, Set<String>>> result = new TreeMap<String, Map<String, Set<String>>>();
  
      for (ZNRecord nodeView : externalViewList)
      {
        Map<String, Map<String, String>> partitionNodeStateMap = nodeView
            .getMapFields();
        for (String partitionId : partitionNodeStateMap.keySet())
        {
          if (!result.containsKey(partitionId))
          {
            result.put(partitionId, new TreeMap<String, Set<String>>());
          }
          Map<String, String> nodeStateMap = partitionNodeStateMap.get(partitionId);
          for (String nodeName : nodeStateMap.keySet())
          {
            String state = nodeStateMap.get(nodeName);
            if (!result.get(partitionId).containsKey(state))
            {
              result.get(partitionId).put(state, new TreeSet<String>());
            }
            result.get(partitionId).get(state).add(nodeName);
          }
        }
      }
      return result;
    }
  
    /*
     * The parameter is a map that maps the nodeName to a list of ZNRecords.
     */
    public List<ZNRecord> computeExternalView(
       Map<String, List<ZNRecord>> currentStates, List<ZNRecord> idealStates)
   {
     List<ZNRecord> resultList = new ArrayList<ZNRecord>();
     Map<String, ZNRecord> resultRoutingTable = new HashMap<String, ZNRecord>();
     // maps from resourceName to another map : partition -> map <nodename,
     // master/slave>;
     // Fill the routing table with "empty" default state according to ideals
     // states
     // in the cluster
     if (idealStates != null)
     {
       for (ZNRecord idealState : idealStates)
       {
         ZNRecord defaultExternalView = new ZNRecord(idealState.getId());
         resultRoutingTable.put(idealState.getId(), defaultExternalView);
       }
     } else
     {
       assert (!currentStates.isEmpty());
       return resultList;
     }
     for (String nodeName : currentStates.keySet())
     {
       List<ZNRecord> znStates = currentStates.get(nodeName);
       for (ZNRecord nodeStateRecord : znStates)
       {
         Map<String, Map<String, String>> resourceStates = nodeStateRecord
             .getMapFields();
         for (String stateUnitKey : resourceStates.keySet())
         {
           Map<String, String> partitionStates = resourceStates.get(stateUnitKey);
           String resourceName = partitionStates
               .get(Message.Attributes.RESOURCE_NAME.toString());
           ZNRecord partitionStatus = resultRoutingTable.get(resourceName);
           if (partitionStatus == null)
           {
             partitionStatus = new ZNRecord(resourceName);
             resultRoutingTable.put(resourceName, partitionStatus);
           }
           String currentStateKey = CurrentStateProperty.CURRENT_STATE.toString();
 
           if (!partitionStatus.getMapFields().containsKey(stateUnitKey))
           {
             partitionStatus.setMapField(stateUnitKey,
                 new TreeMap<String, String>());
           }
           partitionStatus.getMapField(stateUnitKey).put(nodeName,
                   partitionStates.get(currentStateKey));
 
         }
       }
     }
     for (ZNRecord record : resultRoutingTable.values())
     {
       resultList.add(record);
     }
     return resultList;
   }
 }