/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2009, 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.ha.framework.server.lock;

import java.io.Serializable;

import org.jboss.ha.framework.interfaces.ClusterNode;
import org.jboss.ha.framework.interfaces.HAPartition;

/**
 * Support class for cluster locking scenarios where threads cannot acquire
 * a local lock unless the node owns a cluster-wide lock, but where the node
 * owning the cluster-wide lock will yield it to another node if no thread
 * has a local lock. Use case for this is scenarios like session management
 * where a node needs to acquire ownership of a cluster-wide lock for a session, 
 * but then once acquired wishes to handle multiple calls for the session without
 * make cluster-wide locking calls. The node handling the session would acquire
 * the cluster-wide lock if it doesn't have it and thereafter would only use
 * local locks; if another node received a request for the session it would 
 * request the lock and the first node would release it if no local locks are
 * held.
 * 
 * @author Brian Stansberry
 */
public class YieldingGloballyExclusiveClusterLockSupport extends AbstractClusterLockSupport
{
   public YieldingGloballyExclusiveClusterLockSupport(String serviceHAName, 
                                 HAPartition partition, 
                                 LocalLockHandler handler)
   {
      super(serviceHAName, partition, handler);
   }
   
   // ------------------------------------------------------ ClusterLockManager
   
   public void unlock(Serializable lockId)
   {
      ClusterNode myself = getLocalClusterNode();
      if (myself == null)
      {
         throw new IllegalStateException("Must call start() before first call to unlock()");
      }
      
      ClusterLockState category = getClusterLockState(lockId, false);
      
      if (category != null && myself.equals(category.getHolder()))
      {
         category.invalidate();
         getLocalHandler().unlockFromCluster(lockId, myself);
         removeLockState(category);
      }
   }
   
   // --------------------------------------------------------------- Protected
   
   @Override
   protected ClusterLockState getClusterLockState(Serializable categoryName)
   {
      return getClusterLockState(categoryName, false);
   }
   
   @Override
   protected RemoteLockResponse yieldLock(ClusterLockState lockState, ClusterNode caller, long timeout)
   {
      if (getLocalClusterNode().equals(lockState.getHolder()))
      {
         return getLock(lockState.lockId, lockState, caller, timeout);
      }
      else
      {
         return new RemoteLockResponse(getLocalClusterNode(), RemoteLockResponse.Flag.REJECT, lockState.getHolder());
      }
   }

   @Override
   protected RemoteLockResponse handleLockSuccess(ClusterLockState lockState, ClusterNode caller)
   {
      if (getLocalClusterNode().equals(caller))
      {
         recordLockHolder(lockState, caller);             
      }
      else
      {
         // Caller succeeded, but since this node doesn't hold the
         // lock we don't want to hold the category in our map any longer
         lockState.invalidate();
         removeLockState(lockState);
      }
      return new RemoteLockResponse(getLocalClusterNode(), RemoteLockResponse.Flag.OK);
   }
   
   
   // ----------------------------------------------------------------- Private
}