package org.lsst.ccs.utilities.dispatch;
   
   import java.util.concurrent.CopyOnWriteArrayList;
   import java.util.concurrent.ExecutorService;
   import java.util.logging.Level;
   
   /**
    * An <TT>Observable</TT> that notifies <TT>Observers</TT>
    * through an <TT>ExecutorService</TT> (that is through different threads).
   *
   * @author bernard AMADE
   */
  public class ParallelObservable<P> {
      protected CopyOnWriteArrayList<ASyncObserver<P>> list = new CopyOnWriteArrayList<ASyncObserver<P>>() ;
  
       static class DoUpdate<P2> implements Runnable {
          public final  ASyncObserver<P2> executant ;
          public final P2 data ;
  
          DoUpdate(ASyncObserver<P2> executant, P2 data) {
              this.executant = executant;
              this.data = data ;
          }
  
          @Override
          public void run() {
              try{
                  executant.update(data);
              } catch (Exception exc) {
                 PackCst.CURLOG.log(Level.SEVERE, "while executing :", exc);
              }
          }
      }
  
  
      /**
       *   ExecutorService that deals with the Threads handling the commands.
       */
      protected ExecutorService loop ;
  
  
      /**
       * Here the threads handling the updates are <TT>daemons</TT>.
       * You may change that by using a different constructor with another <TT>ExecutorService</TT>
       */
      public ParallelObservable() {
          this.loop = PackCst.EXECUTOR_SERVICE ;
      }
  
      public ParallelObservable(ExecutorService execService) {
          this.loop = execService ;
      }
  
       public void addObserver(ASyncObserver<P> observer){
          this.list.add(observer);
      }
  
      public void removeObserver(ASyncObserver<P> observer){
          this.list.remove (observer);
      }
  
      /**
       * do not need a call to <TT>setChanged</TT>: observers
       * are immediately notified through different threads
       *
       * @param data
       */
      public void notifyObservers(P data) {
          for(ASyncObserver<P> observer : list) {
              loop.submit(new DoUpdate<P>(observer, data)) ;
          }
  
      }
  }