/*
    * Copyright 2005-2007 The Kuali Foundation
    * 
    * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php
    * 
   * 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.
   */
  package org.kuali.rice.kns.util.cache;
  
  import java.util.HashSet;
  import java.util.Set;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  import com.opensymphony.oscache.base.events.CacheEntryEvent;
  import com.opensymphony.oscache.base.events.CacheEntryEventListener;
  import com.opensymphony.oscache.base.events.CacheGroupEvent;
  import com.opensymphony.oscache.base.events.CachePatternEvent;
  import com.opensymphony.oscache.base.events.CachewideEvent;
  
  
  /**
   * Monitor entry-related events for a cache.
   */
  @SuppressWarnings("unchecked")
  abstract public class OSCacheMonitor implements CacheEntryEventListener {
      private static final Log LOG = LogFactory.getLog(OSCacheMonitor.class);
  
      private final String purpose;
      private final Set entries;
  
      /**
       * Constructs a OSCacheMonitor with the given purpose
       * 
       * @param purpose
       */
  	public OSCacheMonitor(String purpose) {
          this.purpose = purpose;
          entries = new HashSet();
  
          if ( LOG.isInfoEnabled() ) {
          	LOG.info("created " + purpose + " CacheMonitor ");
          }
      }
  
  
      public void cacheEntryAdded(CacheEntryEvent event) {
          entries.add(event.getKey());
          if ( LOG.isDebugEnabled() ) {
          	logEntryEvent("added", event);
          }
      }
  
      public void cacheEntryUpdated(CacheEntryEvent event) {
      	if ( LOG.isDebugEnabled() ) {
      		logEntryEvent("updated", event);
      	}
      }
  
      public void cacheEntryFlushed(CacheEntryEvent event) {
          entries.remove(event.getKey());
          if ( LOG.isDebugEnabled() ) {
          	logEntryEvent("flushed", event);
          }
      }
  
      public void cacheEntryRemoved(CacheEntryEvent event) {
          entries.remove(event.getKey());
          if ( LOG.isDebugEnabled() ) {
          	logEntryEvent("removed", event);
          }
      }
  
      public void cacheFlushed(CachewideEvent event) {
          entries.clear();
          if ( LOG.isDebugEnabled() ) {
          	LOG.debug(purpose + " flushed cache (" + entries.size() + " entries)");
          }
      }
  
  
      public void cacheGroupFlushed(CacheGroupEvent event) {
          // if I read the code correctly, each entry gets its own cacheEntryFlused event
      	if ( LOG.isInfoEnabled() ) {
      		LOG.info(purpose + " flushed cache group '" + event.getGroup() + "'");
      	}
      }
  
      public void cachePatternFlushed(CachePatternEvent event) {
          // if I read the code correctly, each entry gets its own cacheEntryFlused event
     	if ( LOG.isInfoEnabled() ) {
     		LOG.info(purpose + " flushed cache pattern '" + event.getPattern() + "'");
     	}
     }
 
     private void logEntryEvent(String verb, CacheEntryEvent event) {
         LOG.debug(purpose + " " + verb + " entry '" + event.getKey() + "' (" + entries.size() + " entries)");
     }
 }