package org.lsst.ccs.plugin.jas3.rest;
   
   import com.sun.jersey.api.client.Client;
   import com.sun.jersey.api.client.WebResource;
   import com.sun.jersey.api.client.config.ClientConfig;
   import com.sun.jersey.api.client.config.DefaultClientConfig;
   import java.beans.PropertyChangeEvent;
   import java.beans.PropertyChangeListener;
   import java.util.logging.Level;
  import java.util.logging.Logger;
  import javax.ws.rs.core.MediaType;
  import org.freehep.application.studio.Studio;
  import org.freehep.util.FreeHEPLookup;
  import org.lsst.ccs.localdb.statusdb.server.DataChannel;
  
  /**
   * This class is used to connect to a restful service. It can be run on a
   * background thread and does not directly interface to the GUI.
   *
   * @author tonyj
   */
  class RestConnector implements Runnable, PropertyChangeListener {
  
      private static final Logger logger = Logger.getLogger(RestConnector.class.getName());
      private final RestPreferences prefs;
      private final Client client;
      private DataChannel.DataChannelList channelList;
      private final Studio studio;
      private WebResource service;
  
      RestConnector(Studio studio, RestPreferences restPrefs) {
          this.studio = studio;
          this.prefs = restPrefs;
          ClientConfig config = new DefaultClientConfig();
          client = Client.create(config);
          initialize();
      }
  
      private void initialize() {
          prefs.addPropertyChangeListener(this);
      }
  
      @Override
      public void propertyChange(PropertyChangeEvent evt) {
          // Fired if the RestPreferences URL has been changed.
          Thread t = new Thread(this);
          t.start();
      }
      
      /**
       * The run method is called to establish a new connection to the rest
       * server, and register the channels obtained so they can be displayed to
       * the user. It can also be invoked if the rest URL is changed, in which
       * case it discards the old channel list if any, and obtains a new one.
       * 
       * Once obtained both the WebResource (service) and the channel list are 
       * registered with the lookup service, so that any plugin which wants to 
       * react to the change can do so.
       */
      @Override
      public synchronized void run() {
          final FreeHEPLookup lookup = studio.getLookup();
          
          if (service != null) {
              logger.log(Level.INFO, "Discarding old channel list");
              lookup.remove(channelList);
              lookup.remove(service,"dataserver");
              service = null;
          }
          
          String restFullUrl = prefs.getRestURL();
          logger.log(Level.INFO, "Connecting to rest server {0}", restFullUrl);
          WebResource service = client.resource(restFullUrl).path("dataserver");
          try {
              channelList = service.path("listchannels").accept(MediaType.TEXT_XML).get(DataChannel.DataChannelList.class);
              lookup.add(channelList);
              lookup.add(service, "dataserver");
              this.service = service;
              logger.log(Level.INFO, "Connection successful, {0} channels read", channelList.list.size());
          } catch (Exception e) {
              logger.log(Level.WARNING, "Connection unsuccessful", e);
          }
      }
  }