package org.apache.helix.manager.zk;
   
   
   /*
    * 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.io.File;
  import java.util.List;
  
  import org.I0Itec.zkclient.exception.ZkNoNodeException;
  import org.apache.helix.AccessOption;
  import org.apache.helix.BaseDataAccessor;
  import org.apache.helix.store.zk.ZNode;
  import org.apache.helix.util.HelixUtil;
  import org.apache.log4j.Logger;
  import org.apache.zookeeper.data.Stat;
  
  
  public class WriteThroughCache<T> extends Cache<T>
  {
    private static Logger     LOG = Logger.getLogger(WriteThroughCache.class);
  
    final BaseDataAccessor<T> _accessor;
  
    public WriteThroughCache(BaseDataAccessor<T> accessor, List<String> paths)
    {
      super();
      _accessor = accessor;
  
      // init cache
      if (paths != null && !paths.isEmpty())
      {
        for (String path : paths)
        {
          updateRecursive(path);
        }
      }
    }
  
    @Override
    public void update(String path, T data, Stat stat)
    {
      String parentPath = HelixUtil.getZkParentPath(path);
      String childName = HelixUtil.getZkName(path);
      addToParentChildSet(parentPath, childName);
      
      ZNode znode = _cache.get(path);
      if (znode == null)
      {
        _cache.put(path, new ZNode(path, data, stat));
      }
      else
      {
        znode.setData(data);
        znode.setStat(stat);
      }
    }
    
    @Override
    public void updateRecursive(String path)
    {
      if (path == null)
      {
        return;
      }
  
      try
      {
        _lock.writeLock().lock();
  
        // update this node
        Stat stat = new Stat();
        T readData = _accessor.get(path, stat, AccessOption.THROW_EXCEPTION_IFNOTEXIST);
  
        update(path, readData, stat);
        
        // recursively update children nodes if not exists
        ZNode znode = _cache.get(path);
        List<String> childNames = _accessor.getChildNames(path, 0);
        if (childNames != null && childNames.size() > 0)
        {
          for (String childName : childNames)
          {
           String childPath = path + "/" + childName;
           if (!znode.hasChild(childName))
           {
             znode.addChild(childName);
             updateRecursive(childPath);
           }
         }
       }
     }
     catch (ZkNoNodeException e)
     {
       // OK. someone delete znode while we are updating cache
     }
     finally
     {
       _lock.writeLock().unlock();
     }
   }
 }