package org.djutils.stats.summarizers.event;
   
   import org.djutils.event.Event;
   import org.djutils.event.EventListener;
   import org.djutils.event.EventListenerMap;
   import org.djutils.event.EventProducer;
   import org.djutils.event.LocalEventProducer;
   import org.djutils.exceptions.Throw;
   import org.djutils.stats.summarizers.Counter;
  
  /**
   * The Counter class defines a statistics event counter. It embeds an EventProducer so it can keep listeners informed about new
   * observations, and it listens to external events to be able to receive observations, in addition to the register(...) method.
   * <p>
   * Copyright (c) 2002-2025 Delft University of Technology, Jaffalaan 5, 2628 BX Delft, the Netherlands. All rights reserved. See
   * for project information <a href="https://simulation.tudelft.nl/" target="_blank"> https://simulation.tudelft.nl</a>. The DSOL
   * project is distributed under a three-clause BSD-style license, which can be found at
   * <a href="https://simulation.tudelft.nl/dsol/3.0/license.html" target="_blank">
   * https://simulation.tudelft.nl/dsol/3.0/license.html</a>. <br>
   * @author <a href="https://www.tudelft.nl/averbraeck" target="_blank"> Alexander Verbraeck</a>
   * @author <a href="https://www.linkedin.com/in/peterhmjacobs">Peter Jacobs </a>
   */
  public class EventBasedCounter extends Counter implements EventProducer, EventListener
  {
      /** The embedded EventProducer. */
      private EventProducer eventProducer = null;
  
      /**
       * Construct a new EventBasedCounter.
       * @param description the description for this counter
       */
      public EventBasedCounter(final String description)
      {
          this(description, new LocalEventProducer());
      }
  
      /**
       * Construct a new EventBasedCounter with a specific EventProducer, e.g. a remote one.
       * @param description the description for this counter
       * @param eventProducer the EventProducer to embed and use in this statistic
       */
      public EventBasedCounter(final String description, final EventProducer eventProducer)
      {
          super(description);
          Throw.whenNull(eventProducer, "eventProducer cannot be null");
          this.eventProducer = eventProducer;
      }
  
      @Override
      public EventListenerMap getEventListenerMap()
      {
          return this.eventProducer.getEventListenerMap();
      }
  
      @Override
      public void initialize()
      {
          super.initialize();
          if (this.eventProducer != null)
          {
              this.eventProducer.fireEvent(StatisticsEvents.INITIALIZED_EVENT);
          }
      }
  
      @Override
      public void notify(final Event event)
      {
          long value = 1;
          if (event.getContent() instanceof Number)
          {
              value = Math.round(((Number) event.getContent()).doubleValue());
          }
          else
          {
              throw new IllegalArgumentException("event content for counter not a number but of type " + event.getClass());
          }
          register(value);
      }
  
      @Override
      public long register(final long value)
      {
          super.register(value);
          if (hasListeners())
          {
              this.eventProducer.fireEvent(StatisticsEvents.OBSERVATION_ADDED_EVENT, value);
              fireEvents();
          }
          return value;
      }
  
      /**
       * Method that can be overridden to fire own events or additional events when registering an observation.
       */
      protected void fireEvents()
      {
          this.eventProducer.fireEvent(StatisticsEvents.N_EVENT, getN());
          this.eventProducer.fireEvent(StatisticsEvents.COUNT_EVENT, getCount());
      }
 
 }