package org.opentrafficsim.road.gtu.lane.perception.categories.neighbors;
   
   import org.djunits.value.vdouble.scalar.Length;
   import org.opentrafficsim.base.parameters.ParameterException;
   import org.opentrafficsim.core.gtu.GTUException;
   import org.opentrafficsim.core.gtu.RelativePosition;
   import org.opentrafficsim.core.network.NetworkException;
   import org.opentrafficsim.road.gtu.lane.LaneBasedGTU;
   import org.opentrafficsim.road.gtu.lane.control.ControlTacticalPlanner;
  import org.opentrafficsim.road.gtu.lane.perception.DownstreamNeighborsIterable;
  import org.opentrafficsim.road.gtu.lane.perception.LanePerception;
  import org.opentrafficsim.road.gtu.lane.perception.LaneRecord;
  import org.opentrafficsim.road.gtu.lane.perception.LaneStructureRecord;
  import org.opentrafficsim.road.gtu.lane.perception.PerceptionCollectable;
  import org.opentrafficsim.road.gtu.lane.perception.RelativeLane;
  import org.opentrafficsim.road.gtu.lane.perception.categories.LaneBasedAbstractPerceptionCategory;
  import org.opentrafficsim.road.gtu.lane.perception.headway.HeadwayGTU;
  
  /**
   * ACC perception.
   * <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 Mar 12, 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 AccPerception extends LaneBasedAbstractPerceptionCategory implements LongitudinalControllerPerception
  {
  
      /** */
      private static final long serialVersionUID = 20190312L;
  
      /** Onboard sensors in the form of a headway GTU type. */
      private final HeadwayGtuType sensors;
  
      /**
       * Constructor using default sensors with zero delay.
       * @param perception LanePerception; perception
       */
      public AccPerception(final LanePerception perception)
      {
          this(perception, new DefaultCaccSensors());
      }
  
      /**
       * Constructor using specified sensors.
       * @param perception LanePerception; perception
       * @param sensors HeadwayGtuType; headway GTU type that defines the onboard sensor information
       */
      public AccPerception(final LanePerception perception, final HeadwayGtuType sensors)
      {
          super(perception);
          this.sensors = sensors;
      }
  
      /** {@inheritDoc} */
      @Override
      public void updateAll() throws GTUException, NetworkException, ParameterException
      {
          // lazy evaluation
      }
  
      /** {@inheritDoc} */
      @Override
      public PerceptionCollectable<HeadwayGTU, LaneBasedGTU> getLeaders()
      {
          return computeIfAbsent("leaders", () -> computeLeaders());
      }
  
      /**
       * Computes leaders.
       * @return perception iterable for leaders
       */
      private PerceptionCollectable<HeadwayGTU, LaneBasedGTU> computeLeaders()
      {
          try
          {
              LaneStructureRecord record = getPerception().getLaneStructure().getRootRecord();
              Length pos = record.getStartDistance().neg();
              pos = record.getDirection().isPlus() ? pos.plus(getGtu().getFront().getDx())
                      : pos.minus(getGtu().getFront().getDx());
              boolean ignoreIfUpstream = true;
              return new DownstreamNeighboursIterableACC(getGtu(), record, Length.max(Length.ZERO, pos),
                      ((ControlTacticalPlanner) getGtu().getTacticalPlanner()).getSettings()
                              .getParameter(LongitudinalControllerPerception.RANGE),
                      getGtu().getFront(), this.sensors, RelativeLane.CURRENT, ignoreIfUpstream);
          }
          catch (ParameterException | GTUException exception)
          {
              throw new RuntimeException("Unexpected exception while computing gtu alongside.", exception);
          }
      }
  
      /**
       * Extends the regular {@code DownstreamNeighborsIterable} class with skipping leaders that are not sensed by the system.
       * <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 Mar 13, 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>
      */
     private static class DownstreamNeighboursIterableACC extends DownstreamNeighborsIterable
     {
 
         /**
          * Constructor.
          * @param perceivingGtu LaneBasedGTU; perceiving GTU
          * @param root LaneRecord&lt;?&gt;; root record
          * @param initialPosition Length; position on the root record
          * @param maxDistance Length; maximum distance to search
          * @param relativePosition RelativePosition; position to which distance are calculated by subclasses
          * @param headwayGtuType HeadwayGtuType; type of HeadwayGTU to return
          * @param lane RelativeLane; relative lane (used for a left/right distinction to prevent dead-locks)
          * @param ignoreIfUpstream boolean; whether to ignore GTU that are partially upstream of a record
          */
         @SuppressWarnings("checkstyle:parameternumber")
         DownstreamNeighboursIterableACC(final LaneBasedGTU perceivingGtu, final LaneRecord<?> root,
                 final Length initialPosition, final Length maxDistance, final RelativePosition relativePosition,
                 final HeadwayGtuType headwayGtuType, final RelativeLane lane, final boolean ignoreIfUpstream)
         {
             super(perceivingGtu, root, initialPosition, maxDistance, relativePosition, headwayGtuType, lane, ignoreIfUpstream);
         }
 
         /** {@inheritDoc} */
         @Override
         protected Entry getNext(final LaneRecord<?> record, final Length position, final Integer counter) throws GTUException
         {
             Entry next;
             do
             {
                 next = super.getNext(record, position, counter);
             }
             // skip leaders that are not the direct leader and that are not CACC
             while (next != null && first() != null);
             return next;
         }
 
     }
 
 }