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;
     }
 }