package org.opentrafficsim.road.gtu.lane.tactical;
   
   import java.io.Serializable;
   import java.util.ArrayList;
   import java.util.HashSet;
   import java.util.Iterator;
   import java.util.List;
   import java.util.Map;
   import java.util.Set;
  
  import org.djunits.value.vdouble.scalar.Length;
  import org.opentrafficsim.base.OTSClassUtil;
  import org.opentrafficsim.base.parameters.ParameterTypeClass;
  import org.opentrafficsim.base.parameters.ParameterTypeDuration;
  import org.opentrafficsim.base.parameters.ParameterTypeLength;
  import org.opentrafficsim.base.parameters.ParameterTypes;
  import org.opentrafficsim.base.parameters.constraint.ClassConstraint;
  import org.opentrafficsim.core.geometry.OTSGeometryException;
  import org.opentrafficsim.core.geometry.OTSLine3D;
  import org.opentrafficsim.core.gtu.GTUDirectionality;
  import org.opentrafficsim.core.gtu.GTUException;
  import org.opentrafficsim.core.network.LateralDirectionality;
  import org.opentrafficsim.core.network.Link;
  import org.opentrafficsim.core.network.LinkDirection;
  import org.opentrafficsim.core.network.NetworkException;
  import org.opentrafficsim.core.network.Node;
  import org.opentrafficsim.road.gtu.lane.LaneBasedGTU;
  import org.opentrafficsim.road.gtu.lane.perception.LanePerception;
  import org.opentrafficsim.road.gtu.lane.tactical.following.CarFollowingModel;
  import org.opentrafficsim.road.gtu.lane.tactical.lmrs.LMRS;
  import org.opentrafficsim.road.network.lane.CrossSectionElement;
  import org.opentrafficsim.road.network.lane.CrossSectionLink;
  import org.opentrafficsim.road.network.lane.DirectedLanePosition;
  import org.opentrafficsim.road.network.lane.Lane;
  import org.opentrafficsim.road.network.lane.LaneDirection;
  
  /**
   * A lane-based tactical planner generates an operational plan for the lane-based GTU. It can ask the strategic planner for
   * assistance on the route to take when the network splits. This abstract class contains a number of helper methods that make it
   * easy to implement a tactical planner.
   * <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/docs/license.html">OpenTrafficSim License</a>.
   * </p>
   * $LastChangedDate: 2015-07-24 02:58:59 +0200 (Fri, 24 Jul 2015) $, @version $Revision: 1147 $, by $Author: averbraeck $,
   * initial version Nov 25, 2015 <br>
   * @author <a href="http://www.tbm.tudelft.nl/averbraeck">Alexander Verbraeck</a>
   * @author <a href="http://www.tudelft.nl/pknoppers">Peter Knoppers</a>
   */
  public abstract class AbstractLaneBasedTacticalPlanner implements LaneBasedTacticalPlanner, Serializable
  {
  
      /** Tactical planner parameter. */
      public static final ParameterTypeClass<LaneBasedTacticalPlanner> TACTICAL_PLANNER;
  
      static
      {
          Class<LaneBasedTacticalPlanner> type = LaneBasedTacticalPlanner.class;
          TACTICAL_PLANNER = new ParameterTypeClass<>("tactical planner", "Tactical planner class.",
                  OTSClassUtil.getTypedClass(type), LMRS.class, ClassConstraint.newInstance(type, LMRS.class));
      }
  
      /** */
      private static final long serialVersionUID = 20151125L;
  
      /** Look ahead parameter type. */
      protected static final ParameterTypeLength LOOKAHEAD = ParameterTypes.LOOKAHEAD;
  
      /** Time step parameter type. */
      protected static final ParameterTypeDuration DT = ParameterTypes.DT;
  
      /** The car-following model. */
      private CarFollowingModel carFollowingModel;
  
      /** The perception. */
      private final LanePerception lanePerception;
  
      /** GTU. */
      private final LaneBasedGTU gtu;
  
      /**
       * Instantiates a tactical planner.
       * @param carFollowingModel car-following model
       * @param gtu GTU
       * @param lanePerception perception
       */
      public AbstractLaneBasedTacticalPlanner(final CarFollowingModel carFollowingModel, final LaneBasedGTU gtu,
              final LanePerception lanePerception)
      {
          setCarFollowingModel(carFollowingModel);
          this.gtu = gtu;
          this.lanePerception = lanePerception;
      }
  
      /** {@inheritDoc} */
      @Override
      public final LaneBasedGTU getGtu()
      {
          return this.gtu;
     }
 
     /**
      * Build a list of lanes forward, with a maximum headway relative to the reference point of the GTU.
      * @param gtu LaneBasedGTU; the GTU for which to calculate the lane list
      * @param maxHeadway Length; the maximum length for which lanes should be returned
      * @return LanePathInfo; an instance that provides the following information for an operational plan: the lanes to follow,
      *         and the path to follow when staying on the same lane.
      * @throws GTUException when the vehicle is not on one of the lanes on which it is registered
      * @throws NetworkException when the strategic planner is not able to return a next node in the route
      */
     public static LanePathInfo buildLanePathInfo(final LaneBasedGTU gtu, final Length maxHeadway)
             throws GTUException, NetworkException
     {
         DirectedLanePosition dlp = gtu.getReferencePosition();
         return buildLanePathInfo(gtu, maxHeadway, dlp.getLane(), dlp.getPosition(), dlp.getGtuDirection());
     }
 
     /**
      * Build a list of lanes forward, with a maximum headway relative to the reference point of the GTU.
      * @param gtu LaneBasedGTU; the GTU for which to calculate the lane list
      * @param maxHeadway Length; the maximum length for which lanes should be returned
      * @param startLane Lane; the lane in which the path starts
      * @param position Length; the position on the start lane
      * @param startDirectionality GTUDirectionality; the driving direction on the start lane
      * @return LanePathInfo; an instance that provides the following information for an operational plan: the lanes to follow,
      *         and the path to follow when staying on the same lane.
      * @throws GTUException when the vehicle is not on one of the lanes on which it is registered
      * @throws NetworkException when the strategic planner is not able to return a next node in the route
      * @throws GTUException when the vehicle is not on one of the lanes on which it is registered
      * @throws NetworkException when the strategic planner is not able to return a next node in the route
      */
     public static LanePathInfo buildLanePathInfo(final LaneBasedGTU gtu, final Length maxHeadway, final Lane startLane,
             final Length position, final GTUDirectionality startDirectionality) throws GTUException, NetworkException
     {
         List<LaneDirection> laneListForward = new ArrayList<>();
         Lane lane = startLane;
         GTUDirectionality lastGtuDir = startDirectionality;
         Length startPosition = position;
         Lane lastLane = lane;
         laneListForward.add(new LaneDirection(lastLane, lastGtuDir));
         Length distanceToEndOfLane;
         OTSLine3D path;
         try
         {
             if (lastGtuDir.equals(GTUDirectionality.DIR_PLUS))
             {
                 distanceToEndOfLane = lane.getLength().minus(position);
                 path = lane.getCenterLine().extract(position, lane.getLength());
             }
             else
             {
                 distanceToEndOfLane = position;
                 path = lane.getCenterLine().extract(Length.ZERO, position).reverse();
             }
         }
         catch (@SuppressWarnings("unused") OTSGeometryException exception)
         {
             // System.err.println(gtu + ": " + exception.getMessage());
             // System.err.println(lane + ", len=" + lane.getLength());
             // System.err.println(position);
             // throw new GTUException(exception);
 
             // section on current lane too short, floating point operations cause only a single point at the end of the lane
             path = null;
             distanceToEndOfLane = Length.ZERO;
             laneListForward.clear();
             startPosition = Length.ZERO;
         }
 
         while (distanceToEndOfLane.lt(maxHeadway))
         {
             Map<Lane, GTUDirectionality> lanes = lastGtuDir.equals(GTUDirectionality.DIR_PLUS)
                     ? lane.nextLanes(gtu.getGTUType()) : lane.prevLanes(gtu.getGTUType());
             if (lanes.size() == 0)
             {
                 // Dead end. Return with the list as is.
                 return new LanePathInfo(path, laneListForward, startPosition);
             }
             else if (lanes.size() == 1)
             {
                 // Ask the strategical planner what the next link should be (if known), because the strategical planner knows
                 // best!
                 LinkDirection ld = null;
                 ld = gtu.getStrategicalPlanner().nextLinkDirection(lane.getParentLink(), lastGtuDir, gtu.getGTUType());
                 lane = lanes.keySet().iterator().next();
                 if (ld != null && !lane.getParentLink().equals(ld.getLink()))
                 {
                     // Lane not on route anymore. return with the list as is.
                     return new LanePathInfo(path, laneListForward, startPosition);
                 }
             }
             else
             {
                 // Multiple next lanes; ask the strategical planner where to go.
                 // Note: this is not necessarily a split; it could e.g. be a bike path on a road
                 LinkDirection ld;
                 try
                 {
                     ld = gtu.getStrategicalPlanner().nextLinkDirection(lane.getParentLink(), /* gtu.getLanes().get(lane), */
                             lastGtuDir, gtu.getGTUType());
                 }
                 catch (@SuppressWarnings("unused") NetworkException ne)
                 {
                     // no route found.
                     // return the data structure up to this point...
                     return new LanePathInfo(path, laneListForward, startPosition);
                 }
                 Link nextLink = ld.getLink();
                 Lane newLane = null;
                 for (Lane nextLane : lanes.keySet())
                 {
                     if (nextLane.getParentLink().equals(nextLink))
                     {
                         newLane = nextLane;
                         break;
                     }
                 }
                 if (newLane == null)
                 {
                     // we cannot reach the next node on this lane -- we have to make a lane change!
                     // return the data structure up to this point...
                     return new LanePathInfo(path, laneListForward, startPosition);
                 }
                 // otherwise: continue!
                 lane = newLane;
             }
 
             // determine direction for the path
             try
             {
                 if (lastGtuDir.equals(GTUDirectionality.DIR_PLUS))
                 {
                     if (lastLane.getParentLink().getEndNode().equals(lane.getParentLink().getStartNode()))
                     {
                         // -----> O ----->, GTU moves ---->
                         path = concatenateNull(path, lane.getCenterLine());
                         // path = OTSLine3D.concatenate(Lane.MARGIN.si, path, lane.getCenterLine());
                         lastGtuDir = GTUDirectionality.DIR_PLUS;
                     }
                     else
                     {
                         // -----> O <-----, GTU moves ---->
                         path = concatenateNull(path, lane.getCenterLine().reverse());
                         // path = OTSLine3D.concatenate(Lane.MARGIN.si, path, lane.getCenterLine().reverse());
                         lastGtuDir = GTUDirectionality.DIR_MINUS;
                     }
                 }
                 else
                 {
                     if (lastLane.getParentLink().getStartNode().equals(lane.getParentLink().getStartNode()))
                     {
                         // <----- O ----->, GTU moves ---->
                         path = concatenateNull(path, lane.getCenterLine());
                         // path = OTSLine3D.concatenate(Lane.MARGIN.si, path, lane.getCenterLine());
                         lastGtuDir = GTUDirectionality.DIR_PLUS;
                     }
                     else
                     {
                         // <----- O <-----, GTU moves ---->
                         path = concatenateNull(path, lane.getCenterLine().reverse());
                         // path = OTSLine3D.concatenate(Lane.MARGIN.si, path, lane.getCenterLine().reverse());
                         lastGtuDir = GTUDirectionality.DIR_MINUS;
                     }
                 }
                 lastLane = lane;
             }
             catch (OTSGeometryException exception)
             {
                 throw new GTUException(exception);
             }
 
             laneListForward.add(new LaneDirection(lastLane, lastGtuDir));
             distanceToEndOfLane = distanceToEndOfLane.plus(lastLane.getLength());
 
         }
         return new LanePathInfo(path, laneListForward, startPosition);
     }
 
     /**
      * Concatenate two paths, where the first may be {@code null}.
      * @param path path, may be {@code null}
      * @param centerLine center line of lane to add
      * @return concatenated line
      * @throws OTSGeometryException when lines are degenerate or too distant
      */
     public static OTSLine3D concatenateNull(final OTSLine3D path, final OTSLine3D centerLine) throws OTSGeometryException
     {
         if (path == null)
         {
             return centerLine;
         }
         return OTSLine3D.concatenate(Lane.MARGIN.si, path, centerLine);
     }
 
     /**
      * Calculate the next location where the network splits, with a maximum headway relative to the reference point of the GTU.
      * Note: a lane drop is also considered a split (!).
      * @param gtu LaneBasedGTU; the GTU for which to calculate the lane list
      * @param maxHeadway Length; the maximum length for which lanes should be returned
      * @return NextSplitInfo; an instance that provides the following information for an operational plan: whether the network
      *         splits, the node where it splits, and the current lanes that lead to the right node after the split node.
      * @throws GTUException when the vehicle is not on one of the lanes on which it is registered
      * @throws NetworkException when the strategic planner is not able to return a next node in the route
      */
     public static NextSplitInfo determineNextSplit(final LaneBasedGTU gtu, final Length maxHeadway)
             throws GTUException, NetworkException
     {
         Node nextSplitNode = null;
         Set<Lane> correctCurrentLanes = new HashSet<>();
         DirectedLanePosition dlp = gtu.getReferencePosition();
         Lane referenceLane = dlp.getLane();
         double refFrac = dlp.getPosition().si / referenceLane.getLength().si;
         Link lastLink = referenceLane.getParentLink();
         GTUDirectionality lastGtuDir = dlp.getGtuDirection();
         GTUDirectionality referenceLaneDirectionality = lastGtuDir;
         Length lengthForward;
         Length position = dlp.getPosition();
         Node lastNode;
         if (lastGtuDir.equals(GTUDirectionality.DIR_PLUS))
         {
             lengthForward = referenceLane.getLength().minus(position);
             lastNode = referenceLane.getParentLink().getEndNode();
         }
         else
         {
             lengthForward = gtu.position(referenceLane, gtu.getReference());
             lastNode = referenceLane.getParentLink().getStartNode();
         }
 
         // see if we have a split within maxHeadway distance
         while (lengthForward.lt(maxHeadway) && nextSplitNode == null)
         {
             // calculate the number of "outgoing" links
             Set<Link> links = lastNode.getLinks().toSet(); // safe copy
             Iterator<Link> linkIterator = links.iterator();
             while (linkIterator.hasNext())
             {
                 Link link = linkIterator.next();
                 GTUDirectionality drivingDirection =
                         lastNode.equals(link.getStartNode()) ? GTUDirectionality.DIR_PLUS : GTUDirectionality.DIR_MINUS;
                 if (!link.getDirectionality(gtu.getGTUType()).getDirectionalities().contains(drivingDirection))
                 {
                     linkIterator.remove();
                 }
                 // if (link.equals(lastLink) || !link.getLinkType().isCompatible(gtu.getGTUType())
                 // || (link.getDirectionality(gtu.getGTUType()).isForward() && link.getEndNode().equals(lastNode))
                 // || (link.getDirectionality(gtu.getGTUType()).isBackward() && link.getStartNode().equals(lastNode)))
                 // {
                 // linkIterator.remove();
                 // }
             }
 
             // calculate the number of incoming and outgoing lanes on the link
             boolean laneChange = false;
             if (links.size() == 1)
             {
                 for (CrossSectionElement cse : ((CrossSectionLink) lastLink).getCrossSectionElementList())
                 {
                     if (cse instanceof Lane && lastGtuDir.isPlus())
                     {
                         Lane lane = (Lane) cse;
                         if (lane.nextLanes(gtu.getGTUType()).size() == 0)
                         {
                             laneChange = true;
                         }
                     }
                     if (cse instanceof Lane && lastGtuDir.isMinus())
                     {
                         Lane lane = (Lane) cse;
                         if (lane.prevLanes(gtu.getGTUType()).size() == 0)
                         {
                             laneChange = true;
                         }
                     }
                 }
             }
 
             // see if we have a lane drop
             if (laneChange)
             {
                 nextSplitNode = lastNode;
                 // which lane(s) we are registered on and adjacent lanes link to a lane
                 // that does not drop?
                 for (CrossSectionElement cse : referenceLane.getParentLink().getCrossSectionElementList())
                 {
                     if (cse instanceof Lane)
                     {
                         Lane l = (Lane) cse;
                         // if (noLaneDrop(gtu, maxHeadway, l, position, referenceLaneDirectionality))
                         if (noLaneDrop(gtu, maxHeadway, l, l.getLength().multiplyBy(refFrac), referenceLaneDirectionality))
                         {
                             correctCurrentLanes.add(l);
                         }
                     }
                 }
                 return new NextSplitInfo(nextSplitNode, correctCurrentLanes);
             }
 
             // see if we have a split
             if (links.size() > 1)
             {
                 nextSplitNode = lastNode;
                 LinkDirection ld = gtu.getStrategicalPlanner().nextLinkDirection(nextSplitNode, lastLink, gtu.getGTUType());
                 // which lane(s) we are registered on and adjacent lanes link to a lane
                 // that is on the route at the next split?
                 for (CrossSectionElement cse : referenceLane.getParentLink().getCrossSectionElementList())
                 {
                     if (cse instanceof Lane)
                     {
                         Lane l = (Lane) cse;
                         // if (connectsToPath(gtu, maxHeadway, l, position, referenceLaneDirectionality, ld.getLink()))
                         if (connectsToPath(gtu, maxHeadway, l, l.getLength().multiplyBy(refFrac), referenceLaneDirectionality,
                                 ld.getLink()))
                         {
                             correctCurrentLanes.add(l);
                         }
                     }
                 }
                 if (correctCurrentLanes.size() > 0)
                 {
                     return new NextSplitInfo(nextSplitNode, correctCurrentLanes);
                 }
                 // split, but no lane on current link to right direction
                 Set<Lane> correctLanes = new HashSet<>();
                 Set<Lane> wrongLanes = new HashSet<>();
                 for (CrossSectionElement cse : ((CrossSectionLink) lastLink).getCrossSectionElementList())
                 {
                     if (cse instanceof Lane)
                     {
                         Lane l = (Lane) cse;
                         if (connectsToPath(gtu, maxHeadway.plus(l.getLength()), l, Length.ZERO, lastGtuDir, ld.getLink()))
                         {
                             correctLanes.add(l);
                         }
                         else
                         {
                             wrongLanes.add(l);
                         }
                     }
                 }
                 for (Lane wrongLane : wrongLanes)
                 {
                     for (Lane adjLane : wrongLane.accessibleAdjacentLanesLegal(LateralDirectionality.LEFT, gtu.getGTUType(),
                             referenceLaneDirectionality))
                     {
                         if (correctLanes.contains(adjLane))
                         {
                             return new NextSplitInfo(nextSplitNode, correctCurrentLanes, LateralDirectionality.LEFT);
                         }
                     }
                     for (Lane adjLane : wrongLane.accessibleAdjacentLanesLegal(LateralDirectionality.RIGHT, gtu.getGTUType(),
                             referenceLaneDirectionality))
                     {
                         if (correctLanes.contains(adjLane))
                         {
                             return new NextSplitInfo(nextSplitNode, correctCurrentLanes, LateralDirectionality.RIGHT);
                         }
                     }
                 }
                 return new NextSplitInfo(nextSplitNode, correctCurrentLanes, null);
             }
 
             if (links.size() == 0)
             {
                 return new NextSplitInfo(null, correctCurrentLanes);
             }
 
             // just one link
             Link link = links.iterator().next();
 
             // determine direction for the path
             if (lastGtuDir.equals(GTUDirectionality.DIR_PLUS))
             {
                 if (lastLink.getEndNode().equals(link.getStartNode()))
                 {
                     // -----> O ----->, GTU moves ---->
                     lastGtuDir = GTUDirectionality.DIR_PLUS;
                     lastNode = link.getEndNode();
                 }
                 else
                 {
                     // -----> O <-----, GTU moves ---->
                     lastGtuDir = GTUDirectionality.DIR_MINUS;
                     lastNode = link.getEndNode();
                 }
             }
             else
             {
                 if (lastLink.getStartNode().equals(link.getStartNode()))
                 {
                     // <----- O ----->, GTU moves ---->
                     lastNode = link.getStartNode();
                     lastGtuDir = GTUDirectionality.DIR_PLUS;
                 }
                 else
                 {
                     // <----- O <-----, GTU moves ---->
                     lastNode = link.getStartNode();
                     lastGtuDir = GTUDirectionality.DIR_MINUS;
                 }
             }
             lastLink = links.iterator().next();
             lengthForward = lengthForward.plus(lastLink.getLength());
         }
 
         return new NextSplitInfo(null, correctCurrentLanes);
     }
 
     /**
      * Determine whether the lane is directly connected to our route, in other words: if we would (continue to) drive on the
      * given lane, can we take the right branch at the nextSplitNode without switching lanes?
      * @param gtu LaneBasedGTU; the GTU for which we have to determine the lane suitability
      * @param maxHeadway Length; the maximum length for use in the calculation
      * @param startLane Lane; the first lane in the list
      * @param startLanePosition Length; the position on the start lane
      * @param startDirectionality GTUDirectionality; the driving direction on the start lane
      * @param linkAfterSplit Link; the link after the split to which we should connect
      * @return boolean; true if the lane (XXXXX which lane?) is connected to our path
      * @throws GTUException when the vehicle is not on one of the lanes on which it is registered
      * @throws NetworkException when the strategic planner is not able to return a next node in the route
      */
     protected static boolean connectsToPath(final LaneBasedGTU gtu, final Length maxHeadway, final Lane startLane,
             final Length startLanePosition, final GTUDirectionality startDirectionality, final Link linkAfterSplit)
             throws GTUException, NetworkException
     {
         List<LaneDirection> laneDirections =
                 buildLanePathInfo(gtu, maxHeadway, startLane, startLanePosition, startDirectionality).getLaneDirectionList();
         for (LaneDirection laneDirection : laneDirections)
         {
             if (laneDirection.getLane().getParentLink().equals(linkAfterSplit))
             {
                 return true;
             }
         }
         return false;
     }
 
     /**
      * Determine whether the lane does not drop, in other words: if we would (continue to) drive on the given lane, can we
      * continue to drive at the nextSplitNode without switching lanes?
      * @param gtu LaneBasedGTU; the GTU for which we have to determine the lane suitability
      * @param maxHeadway Length; the maximum length for use in the calculation
      * @param startLane Lane; the first lane in the list
      * @param startLanePosition Length; the position on the start lane
      * @param startDirectionality GTUDirectionality; the driving direction on the start lane
      * @return boolean; true if the lane (XXX which lane?) is connected to our path
      * @throws GTUException when the vehicle is not on one of the lanes on which it is registered
      * @throws NetworkException when the strategic planner is not able to return a next node in the route
      */
     protected static boolean noLaneDrop(final LaneBasedGTU gtu, final Length maxHeadway, final Lane startLane,
             final Length startLanePosition, final GTUDirectionality startDirectionality) throws GTUException, NetworkException
     {
         LanePathInfo lpi = buildLanePathInfo(gtu, maxHeadway, startLane, startLanePosition, startDirectionality);
         if (lpi.getPath().getLength().lt(maxHeadway))
         {
             return false;
         }
         return true;
     }
 
     /**
      * Make a list of links on which to drive next, with a maximum headway relative to the reference point of the GTU.
      * @param gtu LaneBasedGTU; the GTU for which to calculate the link list
      * @param maxHeadway Length; the maximum length for which links should be returned
      * @return List&lt;LinkDirection&gt;; a list of links on which to drive next
      * @throws GTUException when the vehicle is not on one of the lanes on which it is registered
      * @throws NetworkException when the strategic planner is not able to return a next node in the route
      */
     protected static List<LinkDirection> buildLinkListForward(final LaneBasedGTU gtu, final Length maxHeadway)
             throws GTUException, NetworkException
     {
         List<LinkDirection> linkList = new ArrayList<>();
         DirectedLanePosition dlp = gtu.getReferencePosition();
         Lane referenceLane = dlp.getLane();
         Link lastLink = referenceLane.getParentLink();
         GTUDirectionality lastGtuDir = dlp.getGtuDirection();
         linkList.add(new LinkDirection(lastLink, lastGtuDir));
         Length lengthForward;
         Length position = dlp.getPosition();
         Node lastNode;
         if (lastGtuDir.equals(GTUDirectionality.DIR_PLUS))
         {
             lengthForward = referenceLane.getLength().minus(position);
             lastNode = referenceLane.getParentLink().getEndNode();
         }
         else
         {
             lengthForward = gtu.position(referenceLane, gtu.getReference());
             lastNode = referenceLane.getParentLink().getStartNode();
         }
 
         // see if we have a split within maxHeadway distance
         while (lengthForward.lt(maxHeadway))
         {
             // calculate the number of "outgoing" links
             Set<Link> links = lastNode.getLinks().toSet(); // is a safe copy
             Iterator<Link> linkIterator = links.iterator();
             while (linkIterator.hasNext())
             {
                 Link link = linkIterator.next();
                 GTUDirectionality drivingDirection =
                         lastNode.equals(link.getStartNode()) ? GTUDirectionality.DIR_PLUS : GTUDirectionality.DIR_MINUS;
                 if (link.equals(lastLink) || !link.getLinkType().isCompatible(gtu.getGTUType(), drivingDirection))
                 {
                     linkIterator.remove();
                 }
             }
 
             if (links.size() == 0)
             {
                 return linkList; // the path stops here...
             }
 
             Link link;
             if (links.size() > 1)
             {
                 LinkDirection ld = gtu.getStrategicalPlanner().nextLinkDirection(lastLink, lastGtuDir, gtu.getGTUType());
                 link = ld.getLink();
             }
             else
             {
                 link = links.iterator().next();
             }
 
             // determine direction for the path
             if (lastGtuDir.equals(GTUDirectionality.DIR_PLUS))
             {
                 if (lastLink.getEndNode().equals(link.getStartNode()))
                 {
                     // -----> O ----->, GTU moves ---->
                     lastGtuDir = GTUDirectionality.DIR_PLUS;
                     lastNode = lastLink.getEndNode();
                 }
                 else
                 {
                     // -----> O <-----, GTU moves ---->
                     lastGtuDir = GTUDirectionality.DIR_MINUS;
                     lastNode = lastLink.getEndNode();
                 }
             }
             else
             {
                 if (lastLink.getStartNode().equals(link.getStartNode()))
                 {
                     // <----- O ----->, GTU moves ---->
                     lastNode = lastLink.getStartNode();
                     lastGtuDir = GTUDirectionality.DIR_PLUS;
                 }
                 else
                 {
                     // <----- O <-----, GTU moves ---->
                     lastNode = lastLink.getStartNode();
                     lastGtuDir = GTUDirectionality.DIR_MINUS;
                 }
             }
             lastLink = link;
             linkList.add(new LinkDirection(lastLink, lastGtuDir));
             lengthForward = lengthForward.plus(lastLink.getLength());
         }
         return linkList;
     }
 
     /** {@inheritDoc} */
     @Override
     public final CarFollowingModel getCarFollowingModel()
     {
         return this.carFollowingModel;
     }
 
     /**
      * Sets the car-following model.
      * @param carFollowingModel Car-following model to set.
      */
     public final void setCarFollowingModel(final CarFollowingModel carFollowingModel)
     {
         this.carFollowingModel = carFollowingModel;
     }
 
     /** {@inheritDoc} */
     @Override
     public final LanePerception getPerception()
     {
         return this.lanePerception;
     }
 
 }