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.WeightedTally;
  
  /**
   * The EventBasedWeightedTally class defines a time-weighted tally that can be notified with weights and values using the
   * EventListener. It also produces events when values are tallied and when the tally is initialized. It embeds an EventProducer
   * so it can keep listeners informed about new observations.
   * <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.tudelft.nl/staff/p.knoppers/">Peter Knoppers</a>
   */
  public class EventBasedWeightedTally extends WeightedTally implements EventProducer, EventListener
  {
      /** The embedded EventProducer. */
      private EventProducer eventProducer = null;
  
      /**
       * Construct a new WeightedTally with a description.
       * @param description the description of this WeightedTally
       */
      public EventBasedWeightedTally(final String description)
      {
          this(description, new LocalEventProducer());
      }
  
      /**
       * Construct a new WeightedTally with a description.
       * @param description the description of this WeightedTally
       * @param eventProducer the EventProducer to embed and use in this statistic
       */
      public EventBasedWeightedTally(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)
      {
          // metadata descriptor checks content
          Object[] content = (Object[]) event.getContent();
          double weight = ((Number) content[0]).doubleValue();
          double value = ((Number) content[1]).doubleValue();
          register(weight, value);
      }
  
      /**
       * Process one observed weighted value.
       * @param weight the weight of the value to process
       * @param value the value to process
       * @return the value
       */
      @Override
      public double register(final double weight, final double value)
      {
          super.register(weight, value);
          if (hasListeners())
          {
              this.eventProducer.fireEvent(StatisticsEvents.WEIGHTED_OBSERVATION_ADDED_EVENT, new Object[] {weight, 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.MIN_EVENT, getMin());
         this.eventProducer.fireEvent(StatisticsEvents.MAX_EVENT, getMax());
         this.eventProducer.fireEvent(StatisticsEvents.WEIGHTED_POPULATION_MEAN_EVENT, getWeightedPopulationMean());
         this.eventProducer.fireEvent(StatisticsEvents.WEIGHTED_POPULATION_VARIANCE_EVENT, getWeightedPopulationVariance());
         this.eventProducer.fireEvent(StatisticsEvents.WEIGHTED_POPULATION_STDEV_EVENT, getWeightedPopulationStDev());
         this.eventProducer.fireEvent(StatisticsEvents.WEIGHTED_SUM_EVENT, getWeightedSum());
         this.eventProducer.fireEvent(StatisticsEvents.WEIGHTED_SAMPLE_MEAN_EVENT, getWeightedSampleMean());
         this.eventProducer.fireEvent(StatisticsEvents.WEIGHTED_SAMPLE_VARIANCE_EVENT, getWeightedSampleVariance());
         this.eventProducer.fireEvent(StatisticsEvents.WEIGHTED_SAMPLE_STDEV_EVENT, getWeightedSampleStDev());
     }
 
     @Override
     public String toString()
     {
         return super.toString();
     }
 
 }