package com.atlassian.sal.core.lifecycle;
   
   import com.atlassian.plugin.event.PluginEventListener;
   import com.atlassian.plugin.event.PluginEventManager;
   import com.atlassian.plugin.event.events.PluginFrameworkStartedEvent;
   import com.atlassian.plugin.event.impl.DefaultPluginEventManager;
   import com.atlassian.sal.api.lifecycle.LifecycleAware;
   import com.atlassian.sal.api.lifecycle.LifecycleManager;
   import org.apache.commons.lang.Validate;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.List;
  import java.util.Map;
  
  public abstract class DefaultLifecycleManager implements LifecycleManager
  {
      private static final Logger log = LoggerFactory.getLogger(DefaultLifecycleManager.class);
  
      //@GuardedBy("this")
      private boolean started = false;
      private List<LifecycleAware> listeners;
      private final PluginEventManager pluginEventManager;
  
      public DefaultLifecycleManager(PluginEventManager pluginEventManager)
      {
          this.pluginEventManager = pluginEventManager;
          pluginEventManager.register(this);
      }
  
      /**
       * This method will be invoked by PluginEventManager when PluginFrameworkStartedEvent event occurs.
       * PluginEventManager uses methods called "channel" and methods with annotation "@PluginEventListener"
       * to notify a registered listeners about events.
       * See {@link DefaultPluginEventManager} for more details on this black magic.
       * @param event
       */
      @PluginEventListener
      public void onFrameworkStart(final PluginFrameworkStartedEvent event)
      {
          start();
      }
  
      public synchronized void start()
      {
          if (!started && isApplicationSetUp())
          {
              try
              {
                  notifyOnStart();
              } finally
              {
                  started = true;
              }
  
          }
      }
  
      /**
       * Called by spring-osgi when when new LifecycleAware service is installed. Defined in "spring-components.xml" in "META-INF/spring/"
       *
       * @param service the service to notify
       * @param properties ignored
       */
      @SuppressWarnings("unchecked")
      public synchronized void onBind(final LifecycleAware service, final Map properties)
      {
          if (started)
          {
              notifyLifecycleAwareOfStart(service);
          }
      }
  
      /**
       * Unregister from the {@link PluginEventManager}.
       *
       * @since 2.3.0
       */
      public void destroy()
      {
          pluginEventManager.unregister(this);
      }
  
      protected void notifyOnStart()
      {
          Validate.notNull(listeners, "The list of LifecycleAware implementations hasn't been set yet and so the manager cannot start.");
  
          // calling listeners.iterator() will dynamically update list to get currently installed LifecycleAware components.
          for (final LifecycleAware entry : listeners)
          {
              notifyLifecycleAwareOfStart(entry);
          }
      }
  
      private void notifyLifecycleAwareOfStart(final LifecycleAware entry)
      {
          try
          {
              entry.onStart();
         }
         catch (final RuntimeException ex)
         {
             log.error("Unable to start component: " + entry.getClass().getName(), ex);
         }
     }
 
     //@GuardedBy("spring-dm")
     public void setLifecycleAwareListeners(List<LifecycleAware> listeners)
     {
         this.listeners = listeners;
     }
 }