package org.opentrafficsim.road.gtu.lane.plan.operational;
   
   import java.io.Serializable;
   import java.util.ArrayList;
   import java.util.List;
   import java.util.Map;
   import java.util.Set;
   
   import org.djunits.unit.AccelerationUnit;
  import org.djunits.unit.LengthUnit;
  import org.djunits.unit.SpeedUnit;
  import org.djunits.unit.TimeUnit;
  import org.djunits.value.ValueException;
  import org.djunits.value.vdouble.scalar.Acceleration;
  import org.djunits.value.vdouble.scalar.Duration;
  import org.djunits.value.vdouble.scalar.Length;
  import org.djunits.value.vdouble.scalar.Speed;
  import org.djunits.value.vdouble.scalar.Time;
  import org.opentrafficsim.core.geometry.OTSGeometryException;
  import org.opentrafficsim.core.geometry.OTSLine3D;
  import org.opentrafficsim.core.geometry.OTSPoint3D;
  import org.opentrafficsim.core.gtu.GTUException;
  import org.opentrafficsim.core.gtu.plan.operational.OperationalPlan;
  import org.opentrafficsim.core.gtu.plan.operational.OperationalPlan.SpeedSegment;
  import org.opentrafficsim.core.gtu.plan.operational.OperationalPlanException;
  import org.opentrafficsim.core.math.Solver;
  import org.opentrafficsim.core.network.LateralDirectionality;
  import org.opentrafficsim.road.gtu.lane.AbstractLaneBasedGTU;
  import org.opentrafficsim.road.gtu.lane.LaneBasedGTU;
  import org.opentrafficsim.road.gtu.lane.perception.RelativeLane;
  import org.opentrafficsim.road.network.lane.DirectedLanePosition;
  import org.opentrafficsim.road.network.lane.Lane;
  
  import nl.tudelft.simulation.language.Throw;
  import nl.tudelft.simulation.language.d3.DirectedPoint;
  
  /**
   * Builder for several often used operational plans, based on a list of lanes. E.g., decelerate to come to a full stop at the
   * end of a shape; accelerate to reach a certain speed at the end of a curve; drive constant on a curve; decelerate or
   * accelerate to reach a given end speed at the end of a curve, etc.<br>
   * TODO driving with negative speeds (backward driving) is not yet supported.
   * <p>
   * Copyright (c) 2013-2016 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 15, 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 final class LaneOperationalPlanBuilder
  {
      /** Maximum acceleration for unbounded accelerations: 1E12 m/s2. */
      private static final Acceleration MAX_ACCELERATION = new Acceleration(1E12, AccelerationUnit.SI);
  
      /** Maximum deceleration for unbounded accelerations: -1E12 m/s2. */
      private static final Acceleration MAX_DECELERATION = new Acceleration(-1E12, AccelerationUnit.SI);
  
      /** Private constructor. */
      private LaneOperationalPlanBuilder()
      {
          // class should not be instantiated
      }
  
      /**
       * Build a plan with a path and a given start speed to try to reach a provided end speed, exactly at the end of the curve.
       * The acceleration (and deceleration) are capped by maxAcceleration and maxDeceleration. Therefore, there is no guarantee
       * that the end speed is actually reached by this plan.
       * @param gtu the GTU for debugging purposes
       * @param lanes a list of connected Lanes to do the driving on
       * @param firstLanePosition position on the first lane with the reference point of the GTU
       * @param distance distance to drive for reaching the end speed
       * @param startTime the current time or a time in the future when the plan should start
       * @param startSpeed the speed at the start of the path
       * @param endSpeed the required end speed
       * @param maxAcceleration the maximum acceleration that can be applied, provided as a POSITIVE number
       * @param maxDeceleration the maximum deceleration that can be applied, provided as a NEGATIVE number
       * @return the operational plan to accomplish the given end speed
       * @throws OperationalPlanException when the plan cannot be generated, e.g. because of a path that is too short
       * @throws OperationalPlanException when the length of the path and the calculated driven distance implied by the
       *             constructed segment list differ more than a given threshold
       * @throws OTSGeometryException in case the lanes are not connected or firstLanePosition is larger than the length of the
       *             first lane
       */
      public static LaneBasedOperationalPlan buildGradualAccelerationPlan(final LaneBasedGTU gtu, final List<Lane> lanes,
              final Length firstLanePosition, final Length distance, final Time startTime, final Speed startSpeed,
              final Speed endSpeed, final Acceleration maxAcceleration, final Acceleration maxDeceleration)
              throws OperationalPlanException, OTSGeometryException
      {
          OTSLine3D path = makePath(lanes, firstLanePosition, distance);
          OperationalPlan.Segment segment;
          if (startSpeed.eq(endSpeed))
          {
              segment = new SpeedSegment(distance.divideBy(startSpeed));
          }
          else
          {
              try
              {
                 // t = 2x / (vt + v0); a = (vt - v0) / t
                 Duration duration = distance.multiplyBy(2.0).divideBy(endSpeed.plus(startSpeed));
                 Acceleration acceleration = endSpeed.minus(startSpeed).divideBy(duration);
                 if (acceleration.si < 0.0 && acceleration.lt(maxDeceleration))
                 {
                     acceleration = maxDeceleration;
                     duration = new Duration(Solver.firstSolutionAfter(0, acceleration.si / 2, startSpeed.si, -distance.si),
                             TimeUnit.SI);
                 }
                 if (acceleration.si > 0.0 && acceleration.gt(maxAcceleration))
                 {
                     acceleration = maxAcceleration;
                     duration = new Duration(Solver.firstSolutionAfter(0, acceleration.si / 2, startSpeed.si, -distance.si),
                             TimeUnit.SI);
                 }
                 segment = new OperationalPlan.AccelerationSegment(duration, acceleration);
             }
             catch (ValueException ve)
             {
                 throw new OperationalPlanException(ve);
             }
         }
         ArrayList<OperationalPlan.Segment> segmentList = new ArrayList<>();
         segmentList.add(segment);
         return new LaneBasedOperationalPlan(gtu, path, startTime, startSpeed, segmentList, lanes);
     }
 
     /**
      * Build a plan with a path and a given start speed to try to reach a provided end speed, exactly at the end of the curve.
      * The acceleration (and deceleration) are capped by maxAcceleration and maxDeceleration. Therefore, there is no guarantee
      * that the end speed is actually reached by this plan.
      * @param lanes a list of connected Lanes to do the driving on
      * @param firstLanePosition position on the first lane with the reference point of the GTU
      * @param distance distance to drive for reaching the end speed
      * @return the driving path as a line
      * @throws OperationalPlanException when the length of the lanes is less than the distance when we start at the
      *             firstLanePosition on the first lane, or when the lanes list contains no elements
      * @throws OTSGeometryException in case the lanes are not connected or firstLanePosition is larger than the length of the
      *             first lane
      */
     public static OTSLine3D makePath(final List<Lane> lanes, final Length firstLanePosition, final Length distance)
             throws OperationalPlanException, OTSGeometryException
     {
         if (lanes.size() == 0)
         {
             throw new OperationalPlanException("LaneOperationalPlanBuilder.makePath got a lanes list with size = 0");
         }
         OTSLine3D path = lanes.get(0).getCenterLine().extract(firstLanePosition, lanes.get(0).getLength());
         for (int i = 1; i < lanes.size(); i++)
         {
             // TODO tolerance may depend on network, increased by 4 for A58 demo
             path = OTSLine3D.concatenate(0.15 * 4, path, lanes.get(i).getCenterLine());
         }
         return path.extract(0.0, distance.si);
     }
 
     /**
      * Build a plan with a path and a given start speed to reach a provided end speed, exactly at the end of the curve.
      * Acceleration and deceleration are virtually unbounded (1E12 m/s2) to reach the end speed (e.g., to come to a complete
      * stop).
      * @param gtu the GTU for debugging purposes
      * @param lanes a list of connected Lanes to do the driving on
      * @param firstLanePosition position on the first lane with the reference point of the GTU
      * @param distance distance to drive for reaching the end speed
      * @param startTime the current time or a time in the future when the plan should start
      * @param startSpeed the speed at the start of the path
      * @param endSpeed the required end speed
      * @return the operational plan to accomplish the given end speed
      * @throws OperationalPlanException when the length of the path and the calculated driven distance implied by the
      *             constructed segment list differ more than a given threshold
      * @throws OTSGeometryException in case the lanes are not connected or firstLanePositiion is larger than the length of the
      *             first lane
      */
     public static LaneBasedOperationalPlan buildGradualAccelerationPlan(final LaneBasedGTU gtu, final List<Lane> lanes,
             final Length firstLanePosition, final Length distance, final Time startTime, final Speed startSpeed,
             final Speed endSpeed) throws OperationalPlanException, OTSGeometryException
     {
         return buildGradualAccelerationPlan(gtu, lanes, firstLanePosition, distance, startTime, startSpeed, endSpeed,
                 MAX_ACCELERATION, MAX_DECELERATION);
     }
 
     /**
      * Build a plan with a path and a given start speed to try to reach a provided end speed. Acceleration or deceleration is as
      * provided, until the end speed is reached. After this, constant end speed is used to reach the end point of the path.
      * There is no guarantee that the end speed is actually reached by this plan. If the end speed is zero, and it is reached
      * before completing the path, a truncated path that ends where the GTU stops is used instead.
      * @param gtu the GTU for debugging purposes
      * @param lanes a list of connected Lanes to do the driving on
      * @param firstLanePosition position on the first lane with the reference point of the GTU
      * @param distance distance to drive for reaching the end speed
      * @param startTime the current time or a time in the future when the plan should start
      * @param startSpeed the speed at the start of the path
      * @param endSpeed the required end speed
      * @param acceleration the acceleration to use if endSpeed &gt; startSpeed, provided as a POSITIVE number
      * @param deceleration the deceleration to use if endSpeed &lt; startSpeed, provided as a NEGATIVE number
      * @return the operational plan to accomplish the given end speed
      * @throws OperationalPlanException when the construction of the operational path fails
      * @throws OTSGeometryException in case the lanes are not connected or firstLanePositiion is larger than the length of the
      *             first lane
      */
     public static LaneBasedOperationalPlan buildMaximumAccelerationPlan(final LaneBasedGTU gtu, final List<Lane> lanes,
             final Length firstLanePosition, final Length distance, final Time startTime, final Speed startSpeed,
             final Speed endSpeed, final Acceleration acceleration, final Acceleration deceleration)
             throws OperationalPlanException, OTSGeometryException
     {
         OTSLine3D path = makePath(lanes, firstLanePosition, distance);
         ArrayList<OperationalPlan.Segment> segmentList = new ArrayList<>();
         if (startSpeed.eq(endSpeed))
         {
             segmentList.add(new OperationalPlan.SpeedSegment(distance.divideBy(startSpeed)));
         }
         else
         {
             try
             {
                 if (endSpeed.gt(startSpeed))
                 {
                     Duration t = endSpeed.minus(startSpeed).divideBy(acceleration);
                     Length x = startSpeed.multiplyBy(t).plus(acceleration.multiplyBy(0.5).multiplyBy(t).multiplyBy(t));
                     if (x.ge(distance))
                     {
                         // we cannot reach the end speed in the given distance with the given acceleration
                         Duration duration = new Duration(
                                 Solver.firstSolutionAfter(0, acceleration.si / 2, startSpeed.si, -distance.si), TimeUnit.SI);
                         segmentList.add(new OperationalPlan.AccelerationSegment(duration, acceleration));
                     }
                     else
                     {
                         // we reach the (higher) end speed before the end of the segment. Make two segments.
                         segmentList.add(new OperationalPlan.AccelerationSegment(t, acceleration));
                         Duration duration = distance.minus(x).divideBy(endSpeed);
                         segmentList.add(new OperationalPlan.SpeedSegment(duration));
                     }
                 }
                 else
                 {
                     Duration t = endSpeed.minus(startSpeed).divideBy(deceleration);
                     Length x = startSpeed.multiplyBy(t).plus(deceleration.multiplyBy(0.5).multiplyBy(t).multiplyBy(t));
                     if (x.ge(distance))
                     {
                         // we cannot reach the end speed in the given distance with the given deceleration
                         Duration duration = new Duration(
                                 Solver.firstSolutionAfter(0, deceleration.si / 2, startSpeed.si, -distance.si), TimeUnit.SI);
                         segmentList.add(new OperationalPlan.AccelerationSegment(duration, deceleration));
                     }
                     else
                     {
                         if (endSpeed.si == 0.0)
                         {
                             // if endSpeed == 0, we cannot reach the end of the path. Therefore, build a partial path.
                             OTSLine3D partialPath = path.truncate(x.si);
                             segmentList.add(new OperationalPlan.AccelerationSegment(t, deceleration));
                             return new LaneBasedOperationalPlan(gtu, partialPath, startTime, startSpeed, segmentList, lanes);
                         }
                         // we reach the (lower) end speed, larger than zero, before the end of the segment. Make two segments.
                         segmentList.add(new OperationalPlan.AccelerationSegment(t, deceleration));
                         Duration duration = distance.minus(x).divideBy(endSpeed);
                         segmentList.add(new OperationalPlan.SpeedSegment(duration));
                     }
                 }
             }
             catch (ValueException ve)
             {
                 throw new OperationalPlanException(ve);
             }
 
         }
         return new LaneBasedOperationalPlan(gtu, path, startTime, startSpeed, segmentList, lanes);
     }
 
     /**
      * Build a plan with a path and a given start speed to try to reach a provided end speed. Acceleration or deceleration is as
      * provided, until the end speed is reached. After this, constant end speed is used to reach the end point of the path.
      * There is no guarantee that the end speed is actually reached by this plan. If the end speed is zero, and it is reached
      * before completing the path, a truncated path that ends where the GTU stops is used instead.
      * @param gtu the GTU for debugging purposes
      * @param lanes a list of connected Lanes to do the driving on
      * @param firstLanePosition position on the first lane with the reference point of the GTU
      * @param startTime the current time or a time in the future when the plan should start
      * @param startSpeed the speed at the start of the path
      * @param acceleration the acceleration to use
      * @param timeStep time step for the plan
      * @return the operational plan to accomplish the given end speed
      * @throws OperationalPlanException when the construction of the operational path fails
      * @throws OTSGeometryException in case the lanes are not connected or firstLanePositiion is larger than the length of the
      *             first lane
      */
     public static LaneBasedOperationalPlan buildAccelerationPlan(final LaneBasedGTU gtu, final List<Lane> lanes,
             final Length firstLanePosition, final Time startTime, final Speed startSpeed, final Acceleration acceleration,
             final Duration timeStep) throws OperationalPlanException, OTSGeometryException
     {
 
         if (startSpeed.si <= OperationalPlan.DRIFTING_SPEED_SI && acceleration.le(Acceleration.ZERO))
         {
             // stand-still
             return new LaneBasedOperationalPlan(gtu, gtu.getLocation(), startTime, timeStep, lanes.get(0));
         }
         Length distance;
         ArrayList<OperationalPlan.Segment> segmentList = new ArrayList<>();
         if (startSpeed.plus(acceleration.multiplyBy(timeStep)).lt(Speed.ZERO))
         {
             // will reach stand-still within time step
             Duration brakingTime = startSpeed.divideBy(acceleration.neg());
             segmentList.add(new OperationalPlan.AccelerationSegment(brakingTime, acceleration));
             segmentList.add(new OperationalPlan.SpeedSegment(timeStep.minus(brakingTime)));
             distance = new Length(startSpeed.si * brakingTime.si + .5 * acceleration.si * brakingTime.si * brakingTime.si,
                     LengthUnit.SI);
         }
         else
         {
             segmentList.add(new OperationalPlan.AccelerationSegment(timeStep, acceleration));
             distance =
                     new Length(startSpeed.si * timeStep.si + .5 * acceleration.si * timeStep.si * timeStep.si, LengthUnit.SI);
         }
         OTSLine3D path;
         try
         {
             path = makePath(lanes, firstLanePosition, distance);
         }
         catch (Exception e)
         {
             path = makePath(lanes, firstLanePosition, distance);
             throw new Error("Bad!");
         }
         return new LaneBasedOperationalPlan(gtu, path, startTime, startSpeed, segmentList, lanes);
     }
 
     /**
      * Build a plan with a path and a given start speed to try to reach a provided end speed. Acceleration or deceleration is as
      * provided, until the end speed is reached. After this, constant end speed is used to reach the end point of the path.
      * There is no guarantee that the end speed is actually reached by this plan. If the end speed is zero, and it is reached
      * before completing the path, a truncated path that ends where the GTU stops is used instead.
      * @param gtu the GTU for debugging purposes
      * @param fromLanes lanes where the GTU changes from
      * @param laneChangeDirectionality direction of lane change
      * @param startPosition current position
      * @param startTime the current time or a time in the future when the plan should start
      * @param startSpeed the speed at the start of the path
      * @param acceleration the acceleration to use
      * @param timeStep time step for the plan
      * @param laneChange lane change status
      * @return the operational plan to accomplish the given end speed
      * @throws OperationalPlanException when the construction of the operational path fails
      * @throws OTSGeometryException in case the lanes are not connected or firstLanePositiion is larger than the length of the
      *             first lane
      */
     @SuppressWarnings("checkstyle:parameternumber")
     public static LaneBasedOperationalPlan buildAccelerationLaneChangePlan(final LaneBasedGTU gtu, final List<Lane> fromLanes,
             final LateralDirectionality laneChangeDirectionality, final DirectedPoint startPosition, final Time startTime,
             final Speed startSpeed, final Acceleration acceleration, final Duration timeStep, final LaneChange laneChange)
             throws OperationalPlanException, OTSGeometryException
     {
         // on first call during lane change, use laneChangeDirectionality as laneChange.getDirection() is probably NONE
         LateralDirectionality direction = laneChange.isChangingLane() ? laneChange.getDirection() : laneChangeDirectionality;
         Length fromLaneDistance =
                 new Length(startSpeed.si * timeStep.si + .5 * acceleration.si * timeStep.si * timeStep.si, LengthUnit.SI);
         // TODO also for other driving directions, additional arguments in projectFractional?
         double firstFractionalPosition = fromLanes.get(0).getCenterLine().projectFractional(
                 fromLanes.get(0).getParentLink().getStartNode().getDirection(),
                 fromLanes.get(0).getParentLink().getEndNode().getDirection(), startPosition.x, startPosition.y);
         Length fromLaneFirstPosition = fromLanes.get(0).position(firstFractionalPosition);
         Length cumulDistance = fromLanes.get(0).getLength().minus(fromLaneFirstPosition);
         int lastLaneIndex = 0;
         while (cumulDistance.lt(fromLaneDistance))
         {
             lastLaneIndex++;
             cumulDistance = cumulDistance.plus(fromLanes.get(lastLaneIndex).getLength());
         }
         double lastFractionalPosition = fromLanes.get(lastLaneIndex).getLength().minus(cumulDistance.minus(fromLaneDistance)).si
                 / fromLanes.get(lastLaneIndex).getLength().si;
 
         List<Lane> toLanes = new ArrayList<>();
         for (Lane lane : fromLanes)
         {
             if (!lane.accessibleAdjacentLanes(direction, gtu.getGTUType()).isEmpty())
             {
                 toLanes.add(lane.accessibleAdjacentLanes(direction, gtu.getGTUType()).iterator().next());
             }
             else
             {
                 new Exception().printStackTrace();
                 System.exit(-1);
             }
         }
 
         Length toLaneFirstPosition = toLanes.get(0).position(firstFractionalPosition);
         Length fromLaneLastPosition = fromLanes.get(lastLaneIndex).position(lastFractionalPosition);
         Length toLaneLastPosition = toLanes.get(lastLaneIndex).position(lastFractionalPosition);
 
         DirectedPoint fromFirst = fromLanes.get(0).getCenterLine().getLocation(fromLaneFirstPosition);
         DirectedPoint toFirst = toLanes.get(0).getCenterLine().getLocation(toLaneFirstPosition);
         DirectedPoint fromLast = fromLanes.get(lastLaneIndex).getCenterLine().getLocation(fromLaneLastPosition);
         DirectedPoint toLast = toLanes.get(lastLaneIndex).getCenterLine().getLocation(toLaneLastPosition);
 
         double lastFraction = laneChange.updateAndGetFraction(timeStep, direction, gtu);
         OTSPoint3D lastPoint = new OTSPoint3D(fromLast.x * (1 - lastFraction) + toLast.x * lastFraction,
                 fromLast.y * (1 - lastFraction) + toLast.y * lastFraction,
                 fromLast.z * (1 - lastFraction) + toLast.z * lastFraction);
         OTSPoint3D firstPoint = new OTSPoint3D(startPosition);
         OTSLine3D path = new OTSLine3D(firstPoint, lastPoint);
 
         double t = timeStep.si;
         // why was this used?
         // Acceleration a = new Acceleration((2.0 * (path.getLength().si - startSpeed.si * t)) / (t * t), AccelerationUnit.SI);
         Speed endSpeed = startSpeed.plus(acceleration.multiplyBy(timeStep));
         ArrayList<OperationalPlan.Segment> segmentList = new ArrayList<>();
         if (endSpeed.lt(Speed.ZERO))
         {
             Duration brakingTime = startSpeed.divideBy(acceleration.neg());
             if (brakingTime.si > 0.0)
             {
                 segmentList.add(new OperationalPlan.AccelerationSegment(brakingTime, acceleration));
             }
             segmentList.add(new OperationalPlan.SpeedSegment(timeStep.minus(brakingTime)));
         }
         else
         {
             segmentList.add(new OperationalPlan.AccelerationSegment(timeStep, acceleration));
         }
         return new LaneBasedOperationalPlan(gtu, path, startTime, startSpeed, segmentList, fromLanes, toLanes, lastLaneIndex,
                 lastFractionalPosition);
     }
 
     /**
      * Lane change status across operational plans.
      * <p>
      * Copyright (c) 2013-2016 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 26, 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>
      */
     public static class LaneChange implements Serializable
     {
 
         /** */
         private static final long serialVersionUID = 20160811L;
 
         /** Lane change progress. */
         private Duration laneChangeProgress;
 
         /** Total lane change duration. */
         private Duration laneChangeDuration;
 
         /** Whether the GTU is changing lane. */
         private LateralDirectionality laneChangeDirectionality = null;
 
         /**
          * Return whether the GTU is changing lane.
          * @return whether the GTU is changing lane
          */
         public final boolean isChangingLane()
         {
             return this.laneChangeDirectionality != null;
         }
 
         /**
          * Return whether the GTU is changing left.
          * @return whether the GTU is changing left
          */
         public final boolean isChangingLeft()
         {
             return LateralDirectionality.LEFT.equals(this.laneChangeDirectionality);
         }
 
         /**
          * Return whether the GTU is changing right.
          * @return whether the GTU is changing right
          */
         public final boolean isChangingRight()
         {
             return LateralDirectionality.RIGHT.equals(this.laneChangeDirectionality);
         }
 
         /**
          * Return lateral lane change direction.
          * @return LateralDirectionality; lateral lane change direction
          */
         public final LateralDirectionality getDirection()
         {
             return this.laneChangeDirectionality;
         }
 
         /**
          * @param laneChangeDirectionality set laneChangeDirectionality.
          */
         public final void setLaneChangeDirectionality(final LateralDirectionality laneChangeDirectionality)
         {
             this.laneChangeDirectionality = laneChangeDirectionality;
         }
 
         /**
          * Second lane of lane change relative to the reference lane. Note that the reference lane may either be the source or
          * the target lane. Thus, the second lane during a lane change may either be the left or right lane, regardless of the
          * lane change direction.
          * @param gtu LaneBasedGTU; gtu
          * @return target lane of lane change
          * @throws OperationalPlanException If no lane change is being performed.
          */
         public final RelativeLane getSecondLane(final LaneBasedGTU gtu) throws OperationalPlanException
         {
             Throw.when(!isChangingLane(), OperationalPlanException.class,
                     "Target lane is requested, but no lane change is being performed.");
             Map<Lane, Length> map;
             DirectedLanePosition dlp;
             try
             {
                 map = gtu.positions(gtu.getReference());
                 dlp = gtu.getReferencePosition();
             }
             catch (GTUException exception)
             {
                 throw new OperationalPlanException("Second lane of lane change could not be determined.", exception);
             }
             Set<Lane> accessibleLanes = dlp.getLane().accessibleAdjacentLanes(this.laneChangeDirectionality, gtu.getGTUType());
             if (!accessibleLanes.isEmpty() && map.containsKey(accessibleLanes.iterator().next()))
             {
                 return isChangingLeft() ? RelativeLane.LEFT : RelativeLane.RIGHT;
             }
             return isChangingLeft() ? RelativeLane.RIGHT : RelativeLane.LEFT;
         }
 
         /**
          * Sets the duration for a lane change. May be set during a lane change. Whenever the lane change progress exceeds the
          * lane change duration, the lane change is finalized in the next time step.
          * @param laneChangeDuration total lane change duration
          */
         public final void setLaneChangeDuration(final Duration laneChangeDuration)
         {
             this.laneChangeDuration = laneChangeDuration;
         }
 
         /**
          * Update the lane change and return the lateral fraction for the end of the coming time step. This method is for use by
          * the operational plan builder. It adds the time step duration to the lane change progress. Lane changes are
          * automatically initiated and finalized.
          * @param timeStep coming time step duration
          * @param laneChangeDirection direction of lane change
          * @param gtu GTU
          * @return lateral fraction for the end of the coming time step
          */
         // TODO remove GTU argument (only needed for instantaneous lane change hack)
         final double updateAndGetFraction(final Duration timeStep, final LateralDirectionality laneChangeDirection,
                 final LaneBasedGTU gtu)
         {
             if (!isChangingLane())
             {
                 // initiate lane change
                 this.laneChangeProgress = Duration.ZERO;
                 this.laneChangeDirectionality = laneChangeDirection;
                 try
                 {
                     ((AbstractLaneBasedGTU) gtu).initLaneChange(laneChangeDirection);
                 }
                 catch (GTUException exception)
                 {
                     throw new RuntimeException("Error during lane change initialization.", exception);
                 }
             }
             // add current time step
             this.laneChangeProgress = this.laneChangeProgress.plus(timeStep);
             // get lateral fraction at end of current time step
             double fraction = this.laneChangeProgress.divideBy(this.laneChangeDuration).si;
             if (fraction >= 1.0)
             {
                 // TODO this elsewhere based on path
                 try
                 {
                     ((AbstractLaneBasedGTU) gtu).finalizeLaneChange(laneChangeDirection,
                             gtu.getSimulator().getSimulatorTime().getTime().plus(timeStep));
                 }
                 catch (GTUException exception)
                 {
                     throw new RuntimeException("Error during lane change finalization.", exception);
                 }
                 // limit by 1 and finalize lane change
                 this.laneChangeDirectionality = null;
                 return 1.0;
             }
             return fraction;
         }
 
         /** {@inheritDoc} */
         public final String toString()
         {
             return "LaneChange [" + this.laneChangeProgress + " of " + this.laneChangeDuration + " to "
                     + this.laneChangeDirectionality + "]";
         }
 
     }
 
     /**
      * Build a plan with a path and a given start speed to try to come to a stop with a given deceleration. If the GTU can stop
      * before completing the given path, a truncated path that ends where the GTU stops is used instead. There is no guarantee
      * that the OperationalPlan will lead to a complete stop.
      * @param gtu the GTU for debugging purposes
      * @param lanes a list of connected Lanes to do the driving on
      * @param firstLanePosition position on the first lane with the reference point of the GTU
      * @param distance distance to drive for reaching the end speed
      * @param startTime the current time or a time in the future when the plan should start
      * @param startSpeed the speed at the start of the path
      * @param deceleration the deceleration to use if endSpeed &lt; startSpeed, provided as a NEGATIVE number
      * @return the operational plan to accomplish the given end speed
      * @throws OperationalPlanException when construction of the operational path fails
      * @throws OTSGeometryException in case the lanes are not connected or firstLanePositiion is larger than the length of the
      *             first lane
      */
     public static LaneBasedOperationalPlan buildStopPlan(final LaneBasedGTU gtu, final List<Lane> lanes,
             final Length firstLanePosition, final Length distance, final Time startTime, final Speed startSpeed,
             final Acceleration deceleration) throws OperationalPlanException, OTSGeometryException
     {
         return buildMaximumAccelerationPlan(gtu, lanes, firstLanePosition, distance, startTime, startSpeed,
                 new Speed(0.0, SpeedUnit.SI), new Acceleration(1.0, AccelerationUnit.SI), deceleration);
     }
 
     /*-
     public static OperationalPlan buildSpatialPlan(final LaneBasedGTU gtu, final Time startTime,
         final Acceleration startAcceleration, final Speed maxSpeed, final Duration duration,
         final List<LaneDirection> fromLanes, List<LaneDirection> toLanes, final CurvatureType curvatureType,
         final double laneChangeProgress, final DirectedPoint endPoint) throws OperationalPlanException
     {
         return buildSpatialPlan(gtu, startTime, gtu.getLocation(), gtu.getSpeed(), startAcceleration, maxSpeed, duration,
             fromLanes, toLanes, curvatureType, laneChangeProgress, endPoint);
     }
     
     public static OperationalPlan buildSpatialPlan(final LaneBasedGTU gtu, final Time startTime,
         final DirectedPoint startPoint, final Speed startSpeed, final Acceleration startAcceleration, final Speed maxSpeed,
         final Duration duration, final List<LaneDirection> fromLanes, List<LaneDirection> toLanes,
         final CurvatureType curvatureType, final double laneChangeProgress, final DirectedPoint endPoint)
         throws OperationalPlanException
     {
     
         // check
         checkLaneDirections(fromLanes, toLanes);
     
         // get start fractional position on link
         final CrossSectionLink startLink = fromLanes.get(0).getLane().getParentLink();
         Direction start;
         Direction end;
         if (fromLanes.get(0).getDirection() == GTUDirectionality.DIR_PLUS)
         {
             start = startLink.getStartNode().getDirection();
             end = startLink.getEndNode().getDirection();
         }
         else
         {
             start = startLink.getEndNode().getDirection();
             end = startLink.getStartNode().getDirection();
         }
         double fStart = startLink.getDesignLine().projectFractional(start, end, startPoint.x, startPoint.y);
     
         // get end fractional position on link, and end link
         double fEnd = 0;
         CrossSectionLink endLink = null;
         for (int i = 0; i < toLanes.size(); i++)
         {
             CrossSectionLink l = toLanes.get(i).getLane().getParentLink();
             if (toLanes.get(i).getDirection() == GTUDirectionality.DIR_PLUS)
             {
                 start = l.getStartNode().getDirection();
                 end = l.getEndNode().getDirection();
             }
             else
             {
                 start = l.getEndNode().getDirection();
                 end = l.getStartNode().getDirection();
             }
             fEnd = l.getDesignLine().projectFractional(start, end, endPoint.x, endPoint.y);
             if (fEnd > 0 && fEnd < 1)
             {
                 endLink = l;
                 break;
             }
         }
         Throw.when(endLink == null, OperationalPlanException.class, "End point cannot be projected to to-lanes.");
     
         // build from-line and to-line
         OTSLine3D from = null;
         OTSLine3D to = null;
         for (int i = 0; i < toLanes.size(); i++)
         {
             CrossSectionLink l = toLanes.get(i).getLane().getParentLink();
             try
             {
                 if (l == startLink)
                 {
                     from = fromLanes.get(i).getLane().getCenterLine().extractFractional(fStart, 1);
                     to = toLanes.get(i).getLane().getCenterLine().extractFractional(fStart, 1);
                 }
                 else if (l == endLink)
                 {
                     from =
                         OTSLine3D.concatenate(from, fromLanes.get(i).getLane().getCenterLine().extractFractional(0, fEnd));
                     to = OTSLine3D.concatenate(to, toLanes.get(i).getLane().getCenterLine().extractFractional(0, fEnd));
                     break;
                 }
                 from = OTSLine3D.concatenate(from, fromLanes.get(i).getLane().getCenterLine());
                 to = OTSLine3D.concatenate(to, toLanes.get(i).getLane().getCenterLine());
             }
             catch (OTSGeometryException exception)
             {
                 throw new RuntimeException("Bug in buildSpatialPlan method.");
             }
         }
     
         // interpolate path
         List<OTSPoint3D> line = new ArrayList<>();
         line.add(new OTSPoint3D(startPoint.x, startPoint.y, startPoint.z));
         if (curvatureType.equals(CurvatureType.LINEAR))
         {
             int n = (int) Math.ceil(32 * (1.0 - laneChangeProgress));
             for (int i = 1; i < n; i++)
             {
                 double fraction = 1.0 * i / n;
                 double f0 = laneChangeProgress + (1.0 - laneChangeProgress) * fraction;
                 double f1 = 1.0 - f0;
                 DirectedPoint p1;
                 DirectedPoint p2;
                 try
                 {
                     p1 = from.getLocationFraction(fraction);
                     p2 = to.getLocationFraction(fraction);
                 }
                 catch (OTSGeometryException exception)
                 {
                     throw new RuntimeException("Bug in buildSpatialPlan method.");
                 }
                 line.add(new OTSPoint3D(p1.x * f1 + p2.x * f0, p1.y * f1 + p2.y * f0, p1.z * f1 + p2.z * f0));
             }
         }
         OTSLine3D path;
         try
         {
             path = new OTSLine3D(line);
         }
         catch (OTSGeometryException exception)
         {
             throw new RuntimeException("Bug in buildSpatialPlan method.");
         }
     
         // acceleration segments
         List<Segment> segmentList = new ArrayList<>();
         Acceleration b = startAcceleration.neg();
         if (startSpeed.lt(b.multiplyBy(duration)))
         {
             // will reach zero speed within duration
             Duration d = startSpeed.divideBy(b);
             segmentList.add(new AccelerationSegment(d, startAcceleration)); // decelerate to zero
             segmentList.add(new SpeedSegment(duration.minus(d))); // stay at zero for the remainder of duration
         }
         else
         {
             segmentList.add(new AccelerationSegment(duration, startAcceleration));
         }
     
         return new OperationalPlan(gtu, path, startTime, startSpeed, segmentList);
     }
     
     public static OperationalPlan buildSpatialPlan(final LaneBasedGTU gtu, final Acceleration startAcceleration,
         final Speed maxSpeed, final List<LaneDirection> fromLanes, List<LaneDirection> toLanes,
         final CurvatureType curvatureType, final Duration duration) throws OperationalPlanException
     {
         return buildSpatialPlan(gtu, gtu.getLocation(), gtu.getSpeed(), startAcceleration, maxSpeed, fromLanes, toLanes,
             curvatureType, duration);
     }
     
     public static OperationalPlan buildSpatialPlan(final LaneBasedGTU gtu, final DirectedPoint startPoint,
         final Speed startSpeed, final Acceleration startAcceleration, final Speed maxSpeed,
         final List<LaneDirection> fromLanes, List<LaneDirection> toLanes, final CurvatureType curvatureType,
         final Duration duration) throws OperationalPlanException
     {
         checkLaneDirections(fromLanes, toLanes);
     
         return null;
     }
     
     private final static void checkLaneDirections(final List<LaneDirection> fromLanes, List<LaneDirection> toLanes)
         throws OperationalPlanException
     {
         Throw.when(fromLanes == null || toLanes == null, OperationalPlanException.class, "Lane lists may not be null.");
         Throw.when(fromLanes.isEmpty(), OperationalPlanException.class, "Lane lists may not be empty.");
         Throw.when(fromLanes.size() != toLanes.size(), OperationalPlanException.class,
             "Set of from lanes has different length than set of to lanes.");
         for (int i = 0; i < fromLanes.size(); i++)
         {
             Throw.when(!fromLanes.get(i).getLane().getParentLink().equals(toLanes.get(i).getLane().getParentLink()),
                 OperationalPlanException.class,
                 "A lane in the from-lanes list is not on the same link as the lane at equal index in the to-lanes list.");
         }
     }
     
     /**
      * Defines curvature.
      * <p>
      * Copyright (c) 2013-2016 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 May 27, 2016 <br>
      * @author <a href="http://www.tbm.tudelft.nl/averbraeck">Alexander Verbraeck</a>
      * @author <a href="http://www.transport.citg.tudelft.nl">Wouter Schakel</a>
      */
     /*-
     public enum CurvatureType
     {
         /** Linear lateral movement. */
     /*-
     LINEAR
     {
         public double[] getFractions(final double strartFraction)
         {
             return new double[1];
         }
     },
     
     /** */
     /*-
     SCURVE
     {
         public double[] getFractions(final double strartFraction)
         {
             return new double[1];
         }
     };
     
     public abstract double[] getFractions(double startFraction);
     }
      */
 
 }