/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2008, Red Hat Middleware LLC, and individual contributors
 * as indicated by the @author tags. See the copyright.txt file in the
 * distribution for a full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.jboss.web.tomcat.service.session;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import org.jboss.web.tomcat.service.session.distributedcache.spi.DistributableSessionMetadata;
import org.jboss.web.tomcat.service.session.distributedcache.spi.OutgoingAttributeGranularitySessionData;

/**
 * Implementation of a clustered session where the replication granularity
 * level is attribute based; that is, we replicate only the dirty attributes.
 * <p/>
 * Note that the isolation level of the cache dictates the
 * concurrency behavior. Also note that session and its associated attribtues are stored in different nodes.
 * This will be ok since cache will take care of concurrency. When replicating, we will need to replicate both
 * session and its attributes.</p>
 *
 * @author Ben Wang
 * @author Brian Stansberry
 * 
 * @version $Revision: 92504 $
 */
class AttributeBasedClusteredSession
   extends ClusteredSession<OutgoingAttributeGranularitySessionData>
{
   static final long serialVersionUID = -5625209785550936713L;
   /**
    * Descriptive information describing this Session implementation.
    */
   protected static final String info = "AttributeBasedClusteredSession/1.0";

   // Transient map to store attr changes for replication.
   private transient Map<String, Object> attrModifiedMap_ = new HashMap<String, Object>();
   // Transient set to store attr removals for replication
   private transient Set<String> attrRemovedSet_ = new HashSet<String>();

   // ------------------------------------------------------------ Constructors
   

   public AttributeBasedClusteredSession(ClusteredManager<OutgoingAttributeGranularitySessionData> manager)
   {
      super(manager);
   }

   
   // ----------------------------------------------- Overridden Public Methods

   @Override
   public String getInfo()
   {
      return (info);
   }

   /**
    * Override the superclass to additionally reset this class' fields.
    * <p>
    * <strong>NOTE:</strong> It is not anticipated that this method will be
    * called on a ClusteredSession, but we are overriding the method to be
    * thorough.
    * </p>
    */
   @Override
   public void recycle()
   {
      super.recycle();

      clearAttrChangedMaps();
   }

   // -------------------------------------------- Overridden Protected Methods

   @Override
   protected OutgoingAttributeGranularitySessionData getOutgoingSessionData()
   {
      boolean needFull = isFullReplicationNeeded();
      Map<String, Object> modAttrs = null;
      Set<String> removeAttrs = null;
      if (needFull || isSessionAttributeMapDirty())
      {
         if (needFull)
         {
            modAttrs = new HashMap<String, Object>(getAttributesInternal());
            removeExcludedAttributes(modAttrs);
         }
         else if (attrModifiedMap_.size() > 0)
         {
            modAttrs = new HashMap<String, Object>(attrModifiedMap_);
         }
         
         if (attrRemovedSet_.size() > 0)
         {         
            removeAttrs = new HashSet<String>(attrRemovedSet_);
         }
         
         clearAttrChangedMaps();
      }
      DistributableSessionMetadata metadata = (needFull || isSessionMetadataDirty()) ? getSessionMetadata() : null;
      Long timestamp = modAttrs != null || removeAttrs != null || metadata != null || getMustReplicateTimestamp() ? Long.valueOf(getSessionTimestamp()) : null;
      return new OutgoingData(getRealId(), getVersion(), timestamp, metadata, modAttrs, removeAttrs);
   }

   @Override
   protected Object getAttributeInternal(String name)
   {
      Object result = getAttributesInternal().get(name);

      // Do dirty check even if result is null, as w/ SET_AND_GET null
      // still makes us dirty (ensures timely replication w/o using ACCESS)
      if (isGetDirty(result) && !replicationExcludes.contains(name))
      {
         attributeChanged(name, result, false);
      }

      return result;
   }

   @Override
   protected Object removeAttributeInternal(String name, 
                                            boolean localCall, 
                                            boolean localOnly)
   {
      Object result = getAttributesInternal().remove(name);
      if (localCall && !replicationExcludes.contains(name))
         attributeChanged(name, result, true);
      return result;
   }

   @Override
   protected Object setAttributeInternal(String key, Object value)
   {
      Object old = getAttributesInternal().put(key, value);
      if (!replicationExcludes.contains(key))
         attributeChanged(key, value, false);
      return old;
   }

   // ------------------------------------------------------- Private Methods

   private synchronized void attributeChanged(String key, Object value, boolean removal)
   {
      if (removal)
      {
         if (attrModifiedMap_.containsKey(key))
         {
            attrModifiedMap_.remove(key);
         }
         attrRemovedSet_.add(key);
      }
      else
      {
         if (attrRemovedSet_.contains(key))
         {
            attrRemovedSet_.remove(key);
         }
         attrModifiedMap_.put(key, value);
      }
      sessionAttributesDirty();
   }

   private synchronized void clearAttrChangedMaps()
   {
      attrRemovedSet_.clear();
      attrModifiedMap_.clear();
   }

   // ----------------------------------------------------------------- Classes

   private static class OutgoingData
         extends OutgoingDistributableSessionDataImpl
         implements OutgoingAttributeGranularitySessionData
   {
      private final Map<String, Object> modifiedAttributes;
      private final Set<String> removedAttributes;
      
      public OutgoingData(String realId, int version, 
            Long timestamp, DistributableSessionMetadata metadata,
            Map<String, Object> modifiedAttributes, Set<String> removedAttributes)
      {
         super(realId, version, timestamp, metadata);
         this.modifiedAttributes = modifiedAttributes;
         this.removedAttributes = removedAttributes;
      }

      public Map<String, Object> getModifiedSessionAttributes()
      {
         return modifiedAttributes;
      }

      public Set<String> getRemovedSessionAttributes()
      {
         return removedAttributes;
      }
   }
}