/*
    * Copyright 2006-2011 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.ksb.messaging.threadpool;
  
  import org.apache.log4j.Logger;
  import org.kuali.rice.core.api.config.CoreConfigHelper;
  import org.kuali.rice.core.api.config.property.Config;
  import org.kuali.rice.core.api.config.property.ConfigContext;
  import org.kuali.rice.core.util.ClassLoaderUtils;
  
  import java.util.concurrent.Executors;
  import java.util.concurrent.PriorityBlockingQueue;
  import java.util.concurrent.ThreadFactory;
  import java.util.concurrent.ThreadPoolExecutor;
  import java.util.concurrent.TimeUnit;
  
  /**
   * A Thread Pool implementation for the KSB which implements a thread pool backed by a configuration store.
   *
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  public class KSBThreadPoolImpl extends ThreadPoolExecutor implements KSBThreadPool {
  
      private static final Logger LOG = Logger.getLogger(KSBThreadPoolImpl.class);
  
      public static final int DEFAULT_POOL_SIZE = 5;
  
      private boolean started;
      private boolean poolSizeSet;
  
      public KSBThreadPoolImpl() {
      	super(DEFAULT_POOL_SIZE, DEFAULT_POOL_SIZE, 60, TimeUnit.SECONDS, new PriorityBlockingQueue(1, new PriorityBlockingQueuePersistedMessageComparator()),  new KSBThreadFactory(ClassLoaderUtils.getDefaultClassLoader()), new ThreadPoolExecutor.AbortPolicy());
      }
  
      public void setCorePoolSize(int corePoolSize) {
  		LOG.info("Setting core pool size to " + corePoolSize + " threads.");
  		super.setCorePoolSize(corePoolSize);
  		this.poolSizeSet = true;
      }
  
      public long getKeepAliveTime() {
  	return super.getKeepAliveTime(TimeUnit.MILLISECONDS);
      }
  
      public boolean isStarted() {
  	return this.started;
      }
  
      public void start() throws Exception {
      	LOG.info("Starting the KSB thread pool...");
      	loadSettings();
      	this.started = true;
      	LOG.info("...KSB thread pool successfully started.");
      }
  
      public void stop() throws Exception {
  		if (isStarted()) {
  			LOG.info("Shutting down KSB thread pool...");
  		    this.shutdownNow();
  		    this.started = false;
  		    LOG.info("...KSB thread pool successfully shut down.");
  		}
      }
  
      /**
           * Loads the thread pool settings from the DAO.
           */
      protected void loadSettings() {
  		String threadPoolSizeStr = ConfigContext.getCurrentContextConfig().getProperty(Config.THREAD_POOL_SIZE);
  		if (!this.poolSizeSet) {
  		    int poolSize = DEFAULT_POOL_SIZE;
  		    try {
  		    	poolSize = new Integer(threadPoolSizeStr);
  		    } catch (NumberFormatException nfe) {
  		    	LOG.error( "loadSettings(): Unable to parse the pool size: '"+threadPoolSizeStr+"'");
  		    }
  		    setCorePoolSize(poolSize);
  		}
      }
  
      public Object getInstance() {
      	return this;
      }
  
      /**
          * A simple ThreadFactory which names the thread as follows:<br>
          * <br>
          *
          * <i>applicationId</i>/KSB-pool-<i>m</i>-thread-<i>n</i><br>
          * <br>
          *
          * Where <i>applicationId</i> is the id of the application running the thread pool, <i>m</i> is the
          * sequence number of the factory and <i>n</i> is the sequence number of the thread within the factory.
          *
  * @author Kuali Rice Team (rice.collab@kuali.org)
          */
     private static class KSBThreadFactory implements ThreadFactory {
 
 	private static int factorySequence = 0;
 
 	private static int threadSequence = 0;
 
 	private ThreadFactory defaultThreadFactory = Executors.defaultThreadFactory();
 
 	private ClassLoader contextClassLoader;
 
 	public KSBThreadFactory(ClassLoader contextClassLoader) {
 	    this.contextClassLoader = contextClassLoader;
 	    factorySequence++;
 	}
 
 	public Thread newThread(Runnable runnable) {
 	    threadSequence++;
 	    Thread thread = this.defaultThreadFactory.newThread(runnable);
 	    // if the thread ends up getting spawned by an action inside of a workflow plugin or something along those lines, it will inherit the plugin's
 	    // classloader as it's ContextClassLoader.  Let's make sure it's set to the same ClassLoader that loaded the KSBConfigurer
 	    thread.setContextClassLoader(contextClassLoader);
 	    thread.setName(CoreConfigHelper.getApplicationId() + "/KSB-pool-" + factorySequence + "-thread-"
 		    + threadSequence);
 	    return thread;
 	}
 
     }
 }