package org.opentrafficsim.road.gtu.lane.perception.categories;
   
   import java.util.HashMap;
   import java.util.LinkedHashMap;
   import java.util.LinkedHashSet;
   import java.util.Map;
   import java.util.Objects;
   import java.util.Set;
   import java.util.SortedSet;
  import java.util.TreeSet;
  import java.util.WeakHashMap;
  
  import org.djunits.value.vdouble.scalar.Length;
  import org.djutils.exceptions.Throw;
  import org.djutils.exceptions.Try;
  import org.opentrafficsim.base.TimeStampedObject;
  import org.opentrafficsim.base.parameters.ParameterException;
  import org.opentrafficsim.core.gtu.GTUException;
  import org.opentrafficsim.core.gtu.RelativePosition;
  import org.opentrafficsim.core.network.LateralDirectionality;
  import org.opentrafficsim.core.network.NetworkException;
  import org.opentrafficsim.core.network.route.Route;
  import org.opentrafficsim.road.gtu.lane.perception.InfrastructureLaneChangeInfo;
  import org.opentrafficsim.road.gtu.lane.perception.LanePerception;
  import org.opentrafficsim.road.gtu.lane.perception.LaneStructureRecord;
  import org.opentrafficsim.road.gtu.lane.perception.RelativeLane;
  import org.opentrafficsim.road.network.lane.Lane;
  import org.opentrafficsim.road.network.lane.object.sensor.SingleSensor;
  import org.opentrafficsim.road.network.lane.object.sensor.SinkSensor;
  import org.opentrafficsim.road.network.speed.SpeedLimitProspect;
  import org.opentrafficsim.road.network.speed.SpeedLimitTypes;
  
  /**
   * Perceives information concerning the infrastructure, including splits, lanes, speed limits and road markings. This category
   * is optimized by cooperating closely with the {@code LaneStructure} and only updating internal information when the GTU is on
   * a new {@code Lane}. On the {@code Lane} information is defined relative to the start, and thus easily calculated at each
   * time.
   * <p>
   * Copyright (c) 2013-2019 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/docs/current/license.html">OpenTrafficSim License</a>.
   * <p>
   * @version $Revision$, $LastChangedDate$, by $Author$, initial version Jul 14, 2016 <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>
   */
  // TODO: more than the lane speed limit and maximum vehicle speed in the speed limit prospect
  public class DirectInfrastructurePerception extends LaneBasedAbstractPerceptionCategory implements InfrastructurePerception
  {
  
      /** */
      private static final long serialVersionUID = 20160811L;
  
      /** Infrastructure lane change info per relative lane. */
      private final Map<RelativeLane, TimeStampedObject<SortedSet<InfrastructureLaneChangeInfo>>> infrastructureLaneChangeInfo =
              new HashMap<>();
  
      /** Speed limit prospect per relative lane. */
      private Map<RelativeLane, TimeStampedObject<SpeedLimitProspect>> speedLimitProspect = new HashMap<>();
  
      /** Legal Lane change possibilities per relative lane and lateral direction. */
      private final Map<RelativeLane, Map<LateralDirectionality, TimeStampedObject<LaneChangePossibility>>> legalLaneChangePossibility =
              new HashMap<>();
  
      /** Physical Lane change possibilities per relative lane and lateral direction. */
      private final Map<RelativeLane, Map<LateralDirectionality, TimeStampedObject<LaneChangePossibility>>> physicalLaneChangePossibility =
              new HashMap<>();
  
      /** Cross-section. */
      private TimeStampedObject<SortedSet<RelativeLane>> crossSection;
  
      /** Cache for anyNextOk. */
      private final Map<LaneStructureRecord, Boolean> anyNextOkCache = new WeakHashMap<>();
  
      /** Set of records with accessible end as they are cut off. */
      private final Set<LaneStructureRecord> cutOff = new LinkedHashSet<>();
  
      /** Root. */
      private LaneStructureRecord root;
  
      /** Lanes registered to the GTU used to check if an update is required. */
      private Set<Lane> lanes;
  
      /** Route. */
      private Route route;
  
      /**
       * @param perception LanePerception; perception
       */
      public DirectInfrastructurePerception(final LanePerception perception)
      {
          super(perception);
      }
  
      /** {@inheritDoc} */
      @Override
      public void updateAll() throws GTUException, ParameterException
      {
          updateCrossSection();
         // clean-up
         Set<RelativeLane> cs = getCrossSection();
         this.infrastructureLaneChangeInfo.keySet().retainAll(cs);
         this.legalLaneChangePossibility.keySet().retainAll(cs);
         this.physicalLaneChangePossibility.keySet().retainAll(cs);
         this.speedLimitProspect.keySet().retainAll(cs);
         // only if required
         LaneStructureRecord newRoot = getPerception().getLaneStructure().getRootRecord();
         if (this.root == null || !newRoot.equals(this.root)
                 || !this.lanes.equals(getPerception().getGtu().positions(RelativePosition.REFERENCE_POSITION).keySet())
                 || !Objects.equals(this.route, getPerception().getGtu().getStrategicalPlanner().getRoute())
                 || this.cutOff.stream().filter((record) -> !record.isCutOffEnd()).count() > 0)
         {
             this.cutOff.clear();
             this.root = newRoot;
             this.lanes = getPerception().getGtu().positions(RelativePosition.REFERENCE_POSITION).keySet();
             this.route = getPerception().getGtu().getStrategicalPlanner().getRoute();
             // TODO: this is not suitable if we change lane and consider e.g. dynamic speed signs, they will be forgotten
             this.speedLimitProspect.clear();
             for (RelativeLane lane : getCrossSection())
             {
                 updateInfrastructureLaneChangeInfo(lane);
                 updateLegalLaneChangePossibility(lane, LateralDirectionality.LEFT);
                 updateLegalLaneChangePossibility(lane, LateralDirectionality.RIGHT);
                 updatePhysicalLaneChangePossibility(lane, LateralDirectionality.LEFT);
                 updatePhysicalLaneChangePossibility(lane, LateralDirectionality.RIGHT);
             }
         }
         // speed limit prospect
         for (RelativeLane lane : getCrossSection())
         {
             updateSpeedLimitProspect(lane);
         }
         for (RelativeLane lane : getCrossSection())
         {
             if (!this.infrastructureLaneChangeInfo.containsKey(lane))
             {
                 updateInfrastructureLaneChangeInfo(lane); // new lane in cross section
                 updateLegalLaneChangePossibility(lane, LateralDirectionality.LEFT);
                 updateLegalLaneChangePossibility(lane, LateralDirectionality.RIGHT);
                 updatePhysicalLaneChangePossibility(lane, LateralDirectionality.LEFT);
                 updatePhysicalLaneChangePossibility(lane, LateralDirectionality.RIGHT);
             }
         }
     }
 
     /** {@inheritDoc} */
     @Override
     public final void updateInfrastructureLaneChangeInfo(final RelativeLane lane) throws GTUException, ParameterException
     {
 
         if (this.infrastructureLaneChangeInfo.containsKey(lane)
                 && this.infrastructureLaneChangeInfo.get(lane).getTimestamp().equals(getTimestamp()))
         {
             // already done at this time
             return;
         }
         updateCrossSection();
 
         // start at requested lane
         SortedSet<InfrastructureLaneChangeInfo> resultSet = new TreeSet<>();
         LaneStructureRecord record = getPerception().getLaneStructure().getFirstRecord(lane);
         try
         {
             record = getPerception().getLaneStructure().getFirstRecord(lane);
             if (!record.allowsRoute(getGtu().getStrategicalPlanner().getRoute(), getGtu().getGTUType()))
             {
                 resultSet.add(InfrastructureLaneChangeInfo.fromInaccessibleLane(record.isDeadEnd()));
                 this.infrastructureLaneChangeInfo.put(lane, new TimeStampedObject<>(resultSet, getTimestamp()));
                 return;
             }
         }
         catch (NetworkException exception)
         {
             throw new GTUException("Route has no destination.", exception);
         }
         Map<LaneStructureRecord, InfrastructureLaneChangeInfo> currentSet = new LinkedHashMap<>();
         Map<LaneStructureRecord, InfrastructureLaneChangeInfo> nextSet = new LinkedHashMap<>();
         RelativePosition front = getPerception().getGtu().getFront();
         currentSet.put(record,
                 new InfrastructureLaneChangeInfo(0, record, front, record.isDeadEnd(), LateralDirectionality.NONE));
         while (!currentSet.isEmpty())
         {
             // move lateral
             nextSet.putAll(currentSet);
             for (LaneStructureRecord laneRecord : currentSet.keySet())
             {
                 while (laneRecord.legalLeft() && !nextSet.containsKey(laneRecord.getLeft()))
                 {
                     InfrastructureLaneChangeInfo info =
                             nextSet.get(laneRecord).left(laneRecord.getLeft(), front, laneRecord.getLeft().isDeadEnd());
                     nextSet.put(laneRecord.getLeft(), info);
                     laneRecord = laneRecord.getLeft();
                 }
             }
             for (LaneStructureRecord laneRecord : currentSet.keySet())
             {
                 while (laneRecord.legalRight() && !nextSet.containsKey(laneRecord.getRight()))
                 {
                     InfrastructureLaneChangeInfo info =
                             nextSet.get(laneRecord).right(laneRecord.getRight(), front, laneRecord.getRight().isDeadEnd());
                     nextSet.put(laneRecord.getRight(), info);
                     laneRecord = laneRecord.getRight();
                 }
             }
             // move longitudinal
             currentSet = nextSet;
             nextSet = new LinkedHashMap<>();
             InfrastructureLaneChangeInfo bestOk = null;
             InfrastructureLaneChangeInfo bestNotOk = null;
             boolean deadEnd = false;
             for (LaneStructureRecord laneRecord : currentSet.keySet())
             {
                 boolean anyOk = Try.assign(() -> anyNextOk(laneRecord), "Route has no destination.");
                 if (anyOk)
                 {
                     // add to nextSet
                     for (LaneStructureRecord next : laneRecord.getNext())
                     {
                         try
                         {
                             if (next.allowsRoute(getGtu().getStrategicalPlanner().getRoute(), getGtu().getGTUType()))
                             {
                                 InfrastructureLaneChangeInfo prev = currentSet.get(laneRecord);
                                 InfrastructureLaneChangeInfo info =
                                         new InfrastructureLaneChangeInfo(prev.getRequiredNumberOfLaneChanges(), next, front,
                                                 next.isDeadEnd(), prev.getLateralDirectionality());
                                 nextSet.put(next, info);
                             }
                         }
                         catch (NetworkException exception)
                         {
                             throw new RuntimeException("Network exception while considering route on next lane.", exception);
                         }
                     }
                     // take best ok
                     if (bestOk == null || currentSet.get(laneRecord).getRequiredNumberOfLaneChanges() < bestOk
                             .getRequiredNumberOfLaneChanges())
                     {
                         bestOk = currentSet.get(laneRecord);
                     }
                 }
                 else
                 {
                     // take best not ok
                     deadEnd = deadEnd || currentSet.get(laneRecord).isDeadEnd();
                     if (bestNotOk == null || currentSet.get(laneRecord).getRequiredNumberOfLaneChanges() < bestNotOk
                             .getRequiredNumberOfLaneChanges())
                     {
                         bestNotOk = currentSet.get(laneRecord);
                     }
                 }
 
             }
             if (bestOk == null)
             {
                 break;
             }
             // if there are lanes that are not okay and only -further- lanes that are ok, we need to change to one of the ok's
             if (bestNotOk != null && bestOk.getRequiredNumberOfLaneChanges() > bestNotOk.getRequiredNumberOfLaneChanges())
             {
                 bestOk.setDeadEnd(deadEnd);
                 resultSet.add(bestOk);
             }
             currentSet = nextSet;
             nextSet = new LinkedHashMap<>();
         }
 
         // save
         this.infrastructureLaneChangeInfo.put(lane, new TimeStampedObject<>(resultSet, getTimestamp()));
     }
 
     /**
      * Returns whether the given record end is ok to pass. If not, a lane change is required before this end. The method will
      * also return true if the next node is the end node of the route, if the lane is cut off due to limited perception range,
      * or when there is a {@code SinkSensor} on the lane.
      * @param record LaneStructureRecord; checked record
      * @return whether the given record end is ok to pass
      * @throws NetworkException if destination could not be obtained
      * @throws GTUException if the GTU could not be obtained
      */
     private boolean anyNextOk(final LaneStructureRecord record) throws NetworkException, GTUException
     {
         if (record.isCutOffEnd())
         {
             this.cutOff.add(record);
             return true; // always ok if cut-off
         }
         // check cache
         Boolean ok = this.anyNextOkCache.get(record);
         if (ok != null)
         {
             return ok;
         }
         // sink
         for (SingleSensor s : record.getLane().getSensors())
         {
             if (s instanceof SinkSensor)
             {
                 this.anyNextOkCache.put(record, true);
                 return true; // ok towards sink
             }
         }
         // check destination
         Route currentRoute = getGtu().getStrategicalPlanner().getRoute();
         try
         {
             if (currentRoute != null && currentRoute.destinationNode().equals(record.getToNode()))
             {
                 this.anyNextOkCache.put(record, true);
                 return true;
             }
         }
         catch (NetworkException exception)
         {
             throw new RuntimeException("Could not determine destination node.", exception);
         }
         // check dead-end
         if (record.getNext().isEmpty())
         {
             this.anyNextOkCache.put(record, false);
             return false; // never ok if dead-end
         }
         // check if we have a route
         if (currentRoute == null)
         {
             this.anyNextOkCache.put(record, true);
             return true; // if no route assume ok, i.e. simple networks without routes
         }
         // finally check route
         ok = record.allowsRouteAtEnd(currentRoute, getGtu().getGTUType());
         this.anyNextOkCache.put(record, ok);
         return ok;
     }
 
     /** {@inheritDoc} */
     @Override
     public final void updateSpeedLimitProspect(final RelativeLane lane) throws GTUException, ParameterException
     {
         updateCrossSection();
         checkLaneIsInCrossSection(lane);
         TimeStampedObject<SpeedLimitProspect> tsSlp = this.speedLimitProspect.get(lane);
         SpeedLimitProspect slp;
         if (tsSlp != null)
         {
             slp = tsSlp.getObject();
             slp.update(getGtu().getOdometer());
         }
         else
         {
             slp = new SpeedLimitProspect(getGtu().getOdometer());
             slp.addSpeedInfo(Length.ZERO, SpeedLimitTypes.MAX_VEHICLE_SPEED, getGtu().getMaximumSpeed(), getGtu());
         }
         try
         {
             Lane laneObj = getGtu().getReferencePosition().getLane();
             if (!slp.containsAddSource(laneObj))
             {
                 slp.addSpeedInfo(Length.ZERO, SpeedLimitTypes.FIXED_SIGN, laneObj.getSpeedLimit(getGtu().getGTUType()),
                         laneObj);
             }
         }
         catch (NetworkException exception)
         {
             throw new RuntimeException("Could not obtain speed limit from lane for perception.", exception);
         }
         this.speedLimitProspect.put(lane, new TimeStampedObject<>(slp, getTimestamp()));
     }
 
     /** {@inheritDoc} */
     @Override
     public final void updateLegalLaneChangePossibility(final RelativeLane lane, final LateralDirectionality lat)
             throws GTUException, ParameterException
     {
         updateLaneChangePossibility(lane, lat, true, this.legalLaneChangePossibility);
     }
 
     /** {@inheritDoc} */
     @Override
     public final void updatePhysicalLaneChangePossibility(final RelativeLane lane, final LateralDirectionality lat)
             throws GTUException, ParameterException
     {
         updateLaneChangePossibility(lane, lat, false, this.physicalLaneChangePossibility);
     }
 
     /**
      * Updates the distance over which lane changes remains legally or physically possible.
      * @param lane RelativeLane; lane from which the lane change possibility is requested
      * @param lat LateralDirectionality; LEFT or RIGHT, null not allowed
      * @param legal boolean; legal, or physical otherwise
      * @param possibilityMap
      *            Map&lt;RelativeLane,Map&lt;LateralDirectionality,TimeStampedObject&lt;LaneChangePossibility&gt;&gt;&gt;;
      *            Map&lt;RelativeLane,Map&lt;LateralDirectionality,TimeStampedObject&lt;LaneChangePossibility&gt;&gt;&gt;; legal
      *            or physical possibility map
      * @throws GTUException if the GTU was not initialized or if the lane is not in the cross section
      * @throws ParameterException if a parameter is not defined
      */
     private void updateLaneChangePossibility(final RelativeLane lane, final LateralDirectionality lat, final boolean legal,
             final Map<RelativeLane, Map<LateralDirectionality, TimeStampedObject<LaneChangePossibility>>> possibilityMap)
             throws GTUException, ParameterException
     {
         updateCrossSection();
         checkLaneIsInCrossSection(lane);
 
         if (possibilityMap.get(lane) == null)
         {
             possibilityMap.put(lane, new HashMap<>());
         }
         LaneStructureRecord record = getPerception().getLaneStructure().getFirstRecord(lane);
         // check tail
         Length tail = getPerception().getGtu().getRear().getDx();
         while (record != null && record.getStartDistance().gt(tail) && !record.getPrev().isEmpty()
                 && ((lat.isLeft() && record.possibleLeft(legal)) || (lat.isRight() && record.possibleRight(legal))))
         {
             if (record.getPrev().size() > 1)
             {
                 // assume not possible at a merge
                 possibilityMap.get(lane).put(lat, new TimeStampedObject<>(
                         new LaneChangePossibility(record.getPrev().get(0), tail, true), getTimestamp()));
                 return;
             }
             else if (record.getPrev().isEmpty())
             {
                 // dead-end, no lane upwards prevents a lane change
                 break;
             }
             record = record.getPrev().get(0);
             if ((lat.isLeft() && !record.possibleLeft(legal)) || (lat.isRight() && !record.possibleRight(legal)))
             {
                 // this lane prevents a lane change for the tail
                 possibilityMap.get(lane).put(lat,
                         new TimeStampedObject<>(new LaneChangePossibility(record, tail, true), getTimestamp()));
                 return;
             }
         }
 
         LaneStructureRecord prevRecord = null;
         record = getPerception().getLaneStructure().getFirstRecord(lane);
 
         Length dx;
         if ((lat.isLeft() && record.possibleLeft(legal)) || (lat.isRight() && record.possibleRight(legal)))
         {
             dx = getPerception().getGtu().getFront().getDx();
             while (record != null
                     && ((lat.isLeft() && record.possibleLeft(legal)) || (lat.isRight() && record.possibleRight(legal))))
             {
                 // TODO: splits
                 prevRecord = record;
                 record = record.getNext().isEmpty() ? null : record.getNext().get(0);
             }
         }
         else
         {
             dx = getPerception().getGtu().getRear().getDx();
             while (record != null
                     && ((lat.isLeft() && !record.possibleLeft(legal)) || (lat.isRight() && !record.possibleRight(legal))))
             {
                 // TODO: splits
                 prevRecord = record;
                 record = record.getNext().isEmpty() ? null : record.getNext().get(0);
             }
         }
         possibilityMap.get(lane).put(lat,
                 new TimeStampedObject<>(new LaneChangePossibility(prevRecord, dx, true), getTimestamp()));
     }
 
     /**
      * @param lane RelativeLane; lane to check
      * @throws GTUException if the lane is not in the cross section
      */
     private void checkLaneIsInCrossSection(final RelativeLane lane) throws GTUException
     {
         Throw.when(!getCrossSection().contains(lane), GTUException.class,
                 "The requeasted lane %s is not in the most recent cross section.", lane);
     }
 
     /** {@inheritDoc} */
     @Override
     public final void updateCrossSection() throws GTUException, ParameterException
     {
         if (this.crossSection != null && this.crossSection.getTimestamp().equals(getTimestamp()))
         {
             // already done at this time
             return;
         }
         this.crossSection =
                 new TimeStampedObject<>(getPerception().getLaneStructure().getExtendedCrossSection(), getTimestamp());
     }
 
     /** {@inheritDoc} */
     @Override
     public final SortedSet<InfrastructureLaneChangeInfo> getInfrastructureLaneChangeInfo(final RelativeLane lane)
     {
         return this.infrastructureLaneChangeInfo.get(lane).getObject();
     }
 
     /** {@inheritDoc} */
     @Override
     public final SpeedLimitProspect getSpeedLimitProspect(final RelativeLane lane)
     {
         return this.speedLimitProspect.get(lane).getObject();
     }
 
     /** {@inheritDoc} */
     @Override
     public final Length getLegalLaneChangePossibility(final RelativeLane fromLane, final LateralDirectionality lat)
     {
         return this.legalLaneChangePossibility.get(fromLane).get(lat).getObject().getDistance(lat);
     }
 
     /** {@inheritDoc} */
     @Override
     public final Length getPhysicalLaneChangePossibility(final RelativeLane fromLane, final LateralDirectionality lat)
     {
         return this.physicalLaneChangePossibility.get(fromLane).get(lat).getObject().getDistance(lat);
     }
 
     /** {@inheritDoc} */
     @Override
     public final SortedSet<RelativeLane> getCrossSection()
     {
         return this.crossSection.getObject();
     }
 
     /**
      * Returns time stamped infrastructure lane change info of a lane. A set is returned as multiple points may force lane
      * changes. Which point is considered most critical is a matter of driver interpretation and may change over time. This is
      * shown below. Suppose vehicle A needs to take the off-ramp, and that behavior is that the minimum distance per required
      * lane change determines how critical it is. First, 400m before the lane-drop, the off-ramp is critical. 300m downstream,
      * the lane-drop is critical. Info is sorted by distance, closest first.
      * 
      * <pre>
      * _______
      * _ _A_ _\_________
      * _ _ _ _ _ _ _ _ _
      * _________ _ _ ___
      *          \_______
      *     (-)        Lane-drop: 1 lane change  in 400m (400m per lane change)
      *     (--------) Off-ramp:  3 lane changes in 900m (300m per lane change, critical)
      *     
      *     (-)        Lane-drop: 1 lane change  in 100m (100m per lane change, critical)
      *     (--------) Off-ramp:  3 lane changes in 600m (200m per lane change)
      * </pre>
      * 
      * @param lane RelativeLane; relative lateral lane
      * @return time stamped infrastructure lane change info of a lane
      */
     public final TimeStampedObject<SortedSet<InfrastructureLaneChangeInfo>> getTimeStampedInfrastructureLaneChangeInfo(
             final RelativeLane lane)
     {
         return this.infrastructureLaneChangeInfo.get(lane);
     }
 
     /**
      * Returns the time stamped prospect for speed limits on a lane (dynamic speed limits may vary between lanes).
      * @param lane RelativeLane; relative lateral lane
      * @return time stamped prospect for speed limits on a lane
      */
     public final TimeStampedObject<SpeedLimitProspect> getTimeStampedSpeedLimitProspect(final RelativeLane lane)
     {
         return this.speedLimitProspect.get(lane);
     }
 
     /**
      * Returns the time stamped distance over which a lane change remains legally possible.
      * @param fromLane RelativeLane; lane from which the lane change possibility is requested
      * @param lat LateralDirectionality; LEFT or RIGHT, null not allowed
      * @return time stamped distance over which a lane change remains possible
      * @throws NullPointerException if {@code lat == null}
      */
     public final TimeStampedObject<Length> getTimeStampedLegalLaneChangePossibility(final RelativeLane fromLane,
             final LateralDirectionality lat)
     {
         TimeStampedObject<LaneChangePossibility> tsLcp = this.legalLaneChangePossibility.get(fromLane).get(lat);
         LaneChangePossibility lcp = tsLcp.getObject();
         return new TimeStampedObject<>(lcp.getDistance(lat), tsLcp.getTimestamp());
     }
 
     /**
      * Returns the time stamped distance over which a lane change remains physically possible.
      * @param fromLane RelativeLane; lane from which the lane change possibility is requested
      * @param lat LateralDirectionality; LEFT or RIGHT, null not allowed
      * @return time stamped distance over which a lane change remains possible
      * @throws NullPointerException if {@code lat == null}
      */
     public final TimeStampedObject<Length> getTimeStampedPhysicalLaneChangePossibility(final RelativeLane fromLane,
             final LateralDirectionality lat)
     {
         TimeStampedObject<LaneChangePossibility> tsLcp = this.physicalLaneChangePossibility.get(fromLane).get(lat);
         LaneChangePossibility lcp = tsLcp.getObject();
         return new TimeStampedObject<>(lcp.getDistance(lat), tsLcp.getTimestamp());
     }
 
     /**
      * Returns a time stamped set of relative lanes representing the cross section. Lanes are sorted left to right.
      * @return time stamped set of relative lanes representing the cross section
      */
     public final TimeStampedObject<SortedSet<RelativeLane>> getTimeStampedCrossSection()
     {
         return this.crossSection;
     }
 
     /** {@inheritDoc} */
     @Override
     public final String toString()
     {
         return "DirectInfrastructurePerception";
     }
 
     /**
      * Helper class to return the distance over which a lane change is or is not possible. The distance is based on a
      * LaneStructureRecord, and does not need an update as such.
      * <p>
      * Copyright (c) 2013-2019 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 14 feb. 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>
      */
     private class LaneChangePossibility
     {
 
         /** Structure the end of which determines the available distance. */
         private final LaneStructureRecord record;
 
         /** Relative distance towards nose or tail. */
         private final double dx;
 
         /** Whether to apply legal accessibility. */
         private final boolean legal;
 
         /**
          * @param record LaneStructureRecord; structure the end of which determines the available distance
          * @param dx Length; relative distance towards nose or tail
          * @param legal boolean; whether to apply legal accessibility
          */
         LaneChangePossibility(final LaneStructureRecord record, final Length dx, final boolean legal)
         {
             this.record = record;
             this.dx = dx.si;
             this.legal = legal;
         }
 
         /**
          * Returns the distance over which a lane change is (&gt;0) or is not (&lt;0) possible.
          * @param lat LateralDirectionality; lateral direction
          * @return Length distance over which a lane change is (&gt;0) or is not (&lt;0) possible
          */
         final Length getDistance(final LateralDirectionality lat)
         {
             double d = this.record.getStartDistance().si + this.record.getLane().getLength().si - this.dx;
             if ((lat.isLeft() && this.record.possibleLeft(this.legal))
                     || (lat.isRight() && this.record.possibleRight(this.legal)))
             {
                 return Length.createSI(d); // possible over d
             }
             return Length.createSI(-d); // not possible over d
         }
 
     }
 
 }