package org.opentrafficsim.road.network.control.rampmetering;
   
   import java.util.List;
   
   import org.djunits.value.vdouble.scalar.Duration;
   import org.djunits.value.vdouble.scalar.Frequency;
   import org.djunits.value.vdouble.scalar.Speed;
   import org.djutils.exceptions.Throw;
   import org.opentrafficsim.road.network.lane.object.detector.LoopDetector;
  
  /**
   * Super class for feed-forward controller. This class contains some helper methods for sub-classes.
   * <p>
   * Copyright (c) 2013-2024 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
   * BSD-style license. See <a href="https://opentrafficsim.org/docs/license.html">OpenTrafficSim License</a>.
   * </p>
   * @author <a href="https://github.com/averbraeck">Alexander Verbraeck</a>
   * @author <a href="https://github.com/peter-knoppers">Peter Knoppers</a>
   * @author <a href="https://github.com/wjschakel">Wouter Schakel</a>
   */
  public abstract class SingleCrossSectionSwitch implements RampMeteringSwitch
  {
  
      /** Control interval. */
      private final Duration interval;
  
      /** Detectors (on downstream section). */
      private final List<LoopDetector> detectors;
  
      /**
       * Constructor.
       * @param interval interval
       * @param detectors detectors
       */
      public SingleCrossSectionSwitch(final Duration interval, final List<LoopDetector> detectors)
      {
          Throw.whenNull(interval, "Interval may not be null.");
          Throw.when(detectors == null || detectors.size() == 0, IllegalArgumentException.class,
                  "At least 1 detector is required.");
          this.interval = interval;
          this.detectors = detectors;
      }
  
      @Override
      public Duration getInterval()
      {
          return this.interval;
      }
  
      /**
       * Returns the mean speed over the detectors.
       * @return mean speed over the detectors
       */
      protected final Speed meanSpeed()
      {
          int n = 0;
          double value = 0.0;
          for (LoopDetector detector : this.detectors)
          {
              if (detector.hasLastValue())
              {
                  value += detector.getLastValue(LoopDetector.MEAN_SPEED).si;
                  n++;
              }
          }
          return Speed.instantiateSI(value / n);
      }
  
      /**
       * Returns the mean flow over the detectors.
       * @return mean flow over the detectors
       */
      protected final Frequency meanFlow()
      {
          return totalFlow().divide(this.detectors.size());
      }
  
      /**
       * Returns the total flow over the detectors.
       * @return total flow over the detectors
       */
      protected final Frequency totalFlow()
      {
          double value = 0.0;
          for (LoopDetector detector : this.detectors)
          {
              if (detector.hasLastValue())
              {
                  value += detector.getLastFlow().si;
              }
          }
          return Frequency.instantiateSI(value);
      }
  
  }