/*

  * 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.kew.plugin;

 import org.apache.log4j.Logger;

 import org.kuali.rice.core.api.config.property.Config;

 import org.kuali.rice.core.impl.resourceloader.BaseWrappingResourceLoader;

 import org.kuali.rice.core.impl.resourceloader.BaseWrappingResourceLoader;

 import org.kuali.rice.core.util.ContextClassLoaderBinder;

 import org.kuali.rice.kew.exception.WorkflowRuntimeException;

 import javax.xml.namespace.QName;

 import java.util.ArrayList;

 import java.util.Iterator;

 import java.util.List;

 /**

  * A KEW Plugin.  A Plugin represents a distinct classloading space living below (as a child) of the core

  * KEW classloader.  It allows for loading of plugin resources from core components of the system.

  * Essentially a Plugin is a specialized ResourceLoader with a custom classloader and attached configuration.

  *

  * @author Kuali Rice Team (rice.collab@kuali.org)

  */

 public class Plugin extends BaseWrappingResourceLoader {

         private static final Logger LOG = Logger.getLogger(Plugin.class);

     private Config config;

     private List<PluginListener> pluginListeners = new ArrayList<PluginListener>();

     private boolean supressStartupFailure = true;

     private boolean started = false;

     private boolean startupFailure = false;

     public Plugin(QName name, Config config, ClassLoader classLoader) {

             super(name, classLoader);

             this.config = config;

     }

     /**

      * Starts the plugin.

      */

     public synchronized void start() {

         if (started) {

             LOG.info(getLogPrefix()+" has already been started.");

             return;

         }

         LOG.info(getLogPrefix()+" Starting...");

         try {

             bindThread();

             try {

                 startupFailure = false;

                 started = true;

                 super.start();

                 LOG.info("Starting plugin listeners");

                 startPluginListeners();

             } finally {

                 unbindThread();

             }

             ClassLoader classLoader = getClassLoader();

             LOG.info(getLogPrefix()+" ...started." + (classLoader != null ? classLoader.toString() : ""));

         } catch (Throwable t) {

             LOG.error(getLogPrefix()+" Failure starting plugin.", t);

             startupFailure = true;

             started = true;

             stop();

             if (!supressStartupFailure) {

                     if (t instanceof Error) {

                             throw (Error)t;

                     } else if (t instanceof RuntimeException) {

                             throw (RuntimeException)t;

                     }

                     throw new WorkflowRuntimeException("Failed to startup plugin.", t);

             }

         }

     }

     /**

      * Stops the plugin.

      */

     public synchronized void stop() {

         if (!started) {

             LOG.info(getLogPrefix()+" has already been stopped.");

             return;

         }

         LOG.info(getLogPrefix()+" Stopping...");

         bindThread();

         try {

             started = false;

             stopPluginListeners();

             // stop resource loaders of super class

             super.stop();

         } catch (Throwable t) {

                 LOG.error(getLogPrefix()+" Failed when attempting to stop the plugin.", t);

         } finally {

             unbindThread();

         }

         resetPlugin();

         LOG.info(getLogPrefix()+" ...stopped.");

     }

     public boolean isStarted() {

         return started;

     }

     public void addPluginListener(PluginListener pluginListener) {

             pluginListeners.add(pluginListener);

     }

     public void removePluginListener(PluginListener pluginListener) {

             pluginListeners.remove(pluginListener);

     }

     protected void startPluginListeners() {

         for (Iterator iterator = pluginListeners.iterator(); iterator.hasNext();) {

             PluginListener listener = (PluginListener) iterator.next();

             listener.pluginInitialized(this);

         }

     }

     /**

      * If we fail to stop a plugin listener, try the next one but don't propogate any

      * exceptions out of this method.  Otherwise the plugin ends up dying and can't be

      * reloaded from a hot deploy.

      */

     protected void stopPluginListeners() {

         for (Iterator iterator = pluginListeners.iterator(); iterator.hasNext();) {

             PluginListener listener = (PluginListener) iterator.next();

             try {

                     listener.pluginDestroyed(this);

             } catch (Throwable t) {

                     LOG.error(getLogPrefix()+" Failed when invoking pluginDestroyed on Plugin Listener '"+listener.getClass().getName()+"'.", t);

             }

         }

     }

     public boolean isSupressStartupFailure() {

                 return supressStartupFailure;

         }

         public void setSupressStartupFailure(boolean supressStartupFailure) {

                 this.supressStartupFailure = supressStartupFailure;

         }

         public void bindThread() {

                 ContextClassLoaderBinder.bind(getClassLoader());

     }

     public void unbindThread() {

         ContextClassLoaderBinder.unbind();

     }

         /**

      * Cleanup plugin resources.

      */

     private void resetPlugin() {

         if (!startupFailure) {

                 setClassLoader(null);

         }

         pluginListeners.clear();

     }

     private String getLogPrefix() {

         return toString();

     }

     public Config getConfig() {

             return config;

     }

     public String toString() {

         return "[Plugin: " + this.getName() + "]";

     }

 }