/*
 * 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.Map;
import java.util.WeakHashMap;

import org.apache.catalina.Manager;

/**
 * Tracks sessions invalidated by the current thread so that JBossCacheManager
 * can avoid trying to retrieve them from the distributed cache if the
 * thread asks it to {@link JBossCacheManager#findSession(String) find} them
 * again.
 * <p>
 * Needed for cases where code that executes after {@link ClusteredSessionValve}
 * has returned asks the request for the session again. With an invalidated
 * session this results in a <code>findSession</code> call to JBossCacheManager,
 * which results in a read of the distributed cache. With buddy replication, that
 * will lead to a data gravitation attempt, which is at a minimum expensive and
 * with asynchronous replication may result pulling a stale version of the
 * session back into the cache.
 * </p>
 * 
 * @author Brian Stansberry
 */
public class SessionInvalidationTracker
{
   private static final ThreadLocal<Map<Manager, String>> invalidatedSessions = 
      new ThreadLocal<Map<Manager, String>>();
   private static final ThreadLocal<Boolean> suspended = new ThreadLocal<Boolean>();
   
   public static void suspend()
   {
      suspended.set(Boolean.TRUE);
   }
   
   public static void resume()
   {
      suspended.set(null);
   }
   
   public static void sessionInvalidated(String id, Manager manager)
   {
      if (Boolean.TRUE != suspended.get())
      {
         Map<Manager, String> map = invalidatedSessions.get();
         if (map == null)
         {
            map = new WeakHashMap<Manager, String>(2);
            invalidatedSessions.set(map);
         }
         map.put(manager, id);
      }
   }
   
   public static void clearInvalidatedSession(String id, Manager manager)
   {
      Map<Manager, String> map = invalidatedSessions.get();
      if (map != null)
      {
         map.remove(manager);
      }
   }
   
   public static boolean isSessionInvalidated(String id, Manager manager)
   {
      boolean result = false;
      Map<Manager, String> map = invalidatedSessions.get();
      if (map != null)
      {
         result = id.equals(map.get(manager));
      }
      return result;
   }
}