package org.opentrafficsim.road.gtu.lane.perception.mental;
   
   import java.util.function.Supplier;
   
   import org.djunits.value.vdouble.scalar.Duration;
   import org.djunits.value.vdouble.scalar.Length;
   import org.djunits.value.vdouble.scalar.Speed;
   import org.opentrafficsim.base.parameters.ParameterException;
   import org.opentrafficsim.base.parameters.ParameterTypes;
  import org.opentrafficsim.base.parameters.Parameters;
  import org.opentrafficsim.core.gtu.Try;
  import org.opentrafficsim.core.gtu.perception.EgoPerception;
  import org.opentrafficsim.road.gtu.lane.LaneBasedGTU;
  import org.opentrafficsim.road.gtu.lane.perception.LanePerception;
  import org.opentrafficsim.road.gtu.lane.perception.PerceptionCollectable.Intermediate;
  import org.opentrafficsim.road.gtu.lane.perception.PerceptionCollectable.PerceptionAccumulator;
  import org.opentrafficsim.road.gtu.lane.perception.PerceptionCollectable.PerceptionCollector;
  import org.opentrafficsim.road.gtu.lane.perception.PerceptionCollectable.PerceptionFinalizer;
  import org.opentrafficsim.road.gtu.lane.perception.mental.Fuller.Task;
  
  /**
   * Task class that translates a (composite) headway in to a task demand.
   * <p>
   * Copyright (c) 2013-2018 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 25 jun. 2018 <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 abstract class TaskHeadwayBased implements Task
  {
  
      /** Current speed. */
      private Speed speed;
  
      /** {@inheritDoc} */
      @Override
      public double demand(final LanePerception perception, final LaneBasedGTU gtu, final Parameters parameters)
              throws ParameterException
      {
          double a = gtu.getAcceleration().si;
          double b = parameters.getParameter(ParameterTypes.B).si;
          double tMin = parameters.getParameter(ParameterTypes.TMIN).si;
          double hMin = a < -b ? (1.0 - (a + b) / (8.0 - b)) * tMin : tMin;
          EgoPerception ego = perception.getPerceptionCategoryOrNull(EgoPerception.class);
          Try.execute(() -> ego.updateSpeed(), "Could not update perception of ego speed.");
          this.speed = ego.getSpeed();
          Duration h = getHeadway(perception, gtu, parameters);
          if (h == null)
          {
              return 0.0; // no task demand
          }
          return h.si <= hMin ? 1.0 : (h.si > 3.0 ? 0.5 : 1.0 - (1.0 - 0.5) * (h.si - hMin) / (3.0 - hMin));
      }
  
      /**
       * Returns the current speed to translate a distance headway to a time headway.
       * @return Speed; speed
       */
      protected Speed getSpeed()
      {
          return this.speed;
      }
  
      /**
       * Returns a collector for the task demand.
       * @param perception LanePerception; perception
       * @param gtu LaneBasedGTU; gtu
       * @param parameters Parameters; parameters
       * @return Duration; headway, {@code null} of none.
       * @throws ParameterException on invalid parameter
       */
      protected abstract Duration getHeadway(LanePerception perception, LaneBasedGTU gtu, Parameters parameters)
              throws ParameterException;
  
      /**
       * Simple collector implementation to obtain time headway.
       * <p>
       * Copyright (c) 2013-2018 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 3 apr. 2018 <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 static class TaskHeadwayCollector implements PerceptionCollector<Duration, LaneBasedGTU, Duration>
      {
  
          /** Own speed. */
          private final Speed speed;
  
          /**
           * Constructor.
           * @param speed Speed; speed
           */
         public TaskHeadwayCollector(final Speed speed)
         {
             this.speed = speed;
         }
 
         /** {@inheritDoc} */
         @Override
         public Supplier<Duration> getIdentity()
         {
             return new Supplier<Duration>()
             {
                 @Override
                 public Duration get()
                 {
                     return null; // if no leader
                 }
             };
         }
 
         /** {@inheritDoc} */
         @Override
         public PerceptionAccumulator<LaneBasedGTU, Duration> getAccumulator()
         {
             return new PerceptionAccumulator<LaneBasedGTU, Duration>()
             {
                 @SuppressWarnings("synthetic-access")
                 @Override
                 public Intermediate<Duration> accumulate(final Intermediate<Duration> intermediate, final LaneBasedGTU object,
                         final Length distance)
                 {
                     intermediate.setObject(distance.divideBy(TaskHeadwayCollector.this.speed));
                     intermediate.stop(); // need only 1 leader
                     return intermediate;
                 }
             };
         }
 
         /** {@inheritDoc} */
         @Override
         public PerceptionFinalizer<Duration, Duration> getFinalizer()
         {
             return new PerceptionFinalizer<Duration, Duration>()
             {
                 @Override
                 public Duration collect(final Duration intermediate)
                 {
                     return intermediate == null ? intermediate : (intermediate.gt0() ? intermediate : Duration.ZERO);
                 }
             };
         }
 
     }
 
 }