// ========================================================================
   // Copyright (c) Webtide LLC
   // ------------------------------------------------------------------------
   // All rights reserved. This program and the accompanying materials
   // are made available under the terms of the Eclipse Public License v1.0
   // and Apache License v2.0 which accompanies this distribution.
   // The Eclipse Public License is available at 
   // http://www.eclipse.org/legal/epl-v10.html
   // The Apache License v2.0 is available at
  // http://www.opensource.org/licenses/apache2.0.php
  // You may elect to redistribute this code under either of these licenses. 
  // ========================================================================
  
  package org.eclipse.jetty.monitor;
  
  import java.io.IOException;
  import java.util.HashSet;
  import java.util.Set;
  
  import javax.management.MBeanServerConnection;
  
  import org.eclipse.jetty.monitor.jmx.MonitorAction;
  import org.eclipse.jetty.monitor.jmx.MonitorTask;
  import org.eclipse.jetty.monitor.jmx.ServiceConnection;
  import org.eclipse.jetty.xml.XmlConfiguration;
  
  /* ------------------------------------------------------------ */
  /**
   * JMXMonitor
   *
   * Performs monitoring of the values of the attributes of MBeans
   * and executes specified actions as well as sends notifications
   * of the specified events that have occurred.
   */
  public class JMXMonitor
  {
      private static JMXMonitor __monitor = new JMXMonitor();
      
      private String _serverUrl;
      private ServiceConnection _serviceConnection;
  
      private Set<MonitorAction> _actions = new HashSet<MonitorAction>();
  
      /* ------------------------------------------------------------ */
      /**
       * Constructs a JMXMonitor instance. Used for XML Configuration.
       * 
       * !! DO NOT INSTANTIATE EXPLICITLY !!
       */
      public JMXMonitor() {}
  
      /* ------------------------------------------------------------ */
      /**
       * Adds monitor actions to the monitor
       *
       * @param actions monitor actions to add
       * @return true if successful
       */
      public boolean addActions(MonitorAction... actions)
      {
          return getInstance().add(actions);
      }
  
      /* ------------------------------------------------------------ */
      /**
       * Removes monitor actions from the monitor
       * 
       * @param actions monitor actions to remove
       * @return true if successful
       */
      public boolean removeActions(MonitorAction... actions)
      {
          return getInstance().remove(actions);
      }
  
      /* ------------------------------------------------------------ */
      /**
       * Sets the JMX server URL
       *
       * @param url URL of the JMX server
       */
      public void setUrl(String url)
       {
          getInstance().set(url);
      }
      
      public MBeanServerConnection getConnection()
          throws IOException
      {
          return getInstance().get();
      }
  
      public static JMXMonitor getInstance()
      {
          return __monitor;
      }
         
      public static boolean addMonitorActions(MonitorAction... actions)
      {
         return getInstance().add(actions);
     }
 
     public static boolean removeMonitorActions(MonitorAction... actions)
     {
         return getInstance().remove(actions);
     }
     
     public static void setServiceUrl(String url)
     {
         getInstance().set(url);
     }
     
     /* ------------------------------------------------------------ */
     /**
      * Retrieves a connection to JMX service
      *
      * @return server connection
      * @throws IOException
      */
     public static MBeanServerConnection getServiceConnection()
         throws IOException
     {
         return getInstance().getConnection();
     }
 
     public static void main(final String args[]) throws Exception
     {
         XmlConfiguration.main(args);
     }
     
     private synchronized boolean add(MonitorAction... actions)
     {
         boolean result = true;
 
         for (MonitorAction action : actions)
         {
             if (!_actions.add(action))
             {
                 result = false;
             }
             else
             {
                 MonitorTask.schedule(action);
             }
         }
         
         return result;
     }
     
     private synchronized boolean remove(MonitorAction... actions)
     {
         boolean result = true;
 
         for (MonitorAction action : actions)
         {
             if (!_actions.remove(action))
             {
                 result = false;
             }
 
             MonitorTask.cancel(action);
         }
         
         return result;
     }
     
     private synchronized void set(String url)
     {
         _serverUrl = url;
 
         if (_serviceConnection != null)
         {
             _serviceConnection.disconnect();
             _serviceConnection = null;
         }
     }
     
     private synchronized MBeanServerConnection get()
         throws IOException
     {
         if (_serviceConnection == null)
         {
             _serviceConnection = new ServiceConnection(_serverUrl);
             _serviceConnection.connect();
         }
         
         return _serviceConnection.getConnection();
     }
 }