package org.opentrafficsim.road.network.control.rampmetering;
   
   import java.util.List;
   
   import org.djunits.unit.FrequencyUnit;
   import org.djunits.unit.SpeedUnit;
   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.djutils.logger.CategoryLogger;
  import org.opentrafficsim.road.network.lane.object.sensor.Detector;
  
  /**
   * Switch implementing the RWS algorithm.
   * <p>
   * Copyright (c) 2013-2020 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
   * BSD-style license. See <a href="http://opentrafficsim.org/node/13">OpenTrafficSim License</a>.
   * <p>
   * @version $Revision$, $LastChangedDate$, by $Author$, initial version 12 jun. 2019 <br>
   * @author <a href="http://www.tbm.tudelft.nl/averbraeck">Alexander Verbraeck</a>
   * @author <a href="http://www.tudelft.nl/pknoppers">Peter Knoppers</a>
   * @author <a href="http://www.transport.citg.tudelft.nl">Wouter Schakel</a>
   */
  public class RwsSwitch extends SingleCrossSectionSwitch
  {
  
      /** Maximum cycle time. */
      private static final Duration MAX_CYCLE_TIME = Duration.instantiateSI(15);
  
      /** Capacity. */
      private final Frequency capacity;
  
      /** Flow threshold. */
      private final Frequency flowThreshold;
  
      /** Speed threshold. */
      private final Speed speedThreshold = new Speed(70, SpeedUnit.KM_PER_HOUR);
  
      /** Red time. */
      private Duration cycleTime;
  
      /** Flow in previous time step. */
      private Frequency lastFlow;
  
      /**
       * @param detectors List&lt;Detector&gt;; detectors
       */
      public RwsSwitch(final List<Detector> detectors)
      {
          super(Duration.instantiateSI(60.0), detectors);
          this.capacity = new Frequency(2000, FrequencyUnit.PER_HOUR).times(detectors.size());
          this.flowThreshold = new Frequency(1500, FrequencyUnit.PER_HOUR).times(detectors.size());
      }
  
      /** {@inheritDoc} */
      @Override
      public boolean isEnabled()
      {
          Frequency flow = totalFlow();
          CategoryLogger.always().info("Flow is " + flow.getInUnit(FrequencyUnit.PER_HOUR));
          if (meanSpeed().le(this.speedThreshold)
                  || (this.lastFlow != null && flow.gt(this.lastFlow) && flow.gt(this.flowThreshold)))
          {
              if (flow.lt(this.capacity))
              {
                  this.cycleTime = Duration.instantiateSI(1.0 / this.capacity.minus(flow).si);
                  this.cycleTime = Duration.min(this.cycleTime, MAX_CYCLE_TIME);
              }
              else
              {
                  this.cycleTime = MAX_CYCLE_TIME;
              }
              this.lastFlow = flow;
              return true;
          }
          this.lastFlow = flow;
          return false;
      }
  
      /** {@inheritDoc} */
      @Override
      public Duration getCycleTime()
      {
          Throw.whenNull(this.cycleTime, "The method isEnabled() in a RwsSwitch should set a cycle time.");
          return this.cycleTime;
      }
  
  }