package org.opentrafficsim.core.gtu;
   
   import java.io.Serializable;
   import java.util.ArrayList;
   import java.util.LinkedHashMap;
   import java.util.LinkedHashSet;
   import java.util.List;
   import java.util.Map;
   import java.util.Set;
  
  import org.djunits.unit.DirectionUnit;
  import org.djunits.unit.DurationUnit;
  import org.djunits.unit.PositionUnit;
  import org.djunits.unit.TimeUnit;
  import org.djunits.value.vdouble.scalar.Acceleration;
  import org.djunits.value.vdouble.scalar.Direction;
  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.djunits.value.vdouble.vector.PositionVector;
  import org.djutils.base.Identifiable;
  import org.djutils.draw.bounds.Bounds2d;
  import org.djutils.draw.line.Polygon2d;
  import org.djutils.draw.point.OrientedPoint2d;
  import org.djutils.draw.point.Point2d;
  import org.djutils.event.EventType;
  import org.djutils.event.LocalEventProducer;
  import org.djutils.exceptions.Throw;
  import org.djutils.exceptions.Try;
  import org.djutils.immutablecollections.Immutable;
  import org.djutils.immutablecollections.ImmutableLinkedHashMap;
  import org.djutils.immutablecollections.ImmutableMap;
  import org.djutils.metadata.MetaData;
  import org.djutils.metadata.ObjectDescriptor;
  import org.opentrafficsim.base.HierarchicallyTyped;
  import org.opentrafficsim.base.geometry.DynamicSpatialObject;
  import org.opentrafficsim.base.geometry.OffsetRectangleShape;
  import org.opentrafficsim.base.geometry.OtsLine2d;
  import org.opentrafficsim.base.geometry.OtsLocatable;
  import org.opentrafficsim.base.geometry.OtsShape;
  import org.opentrafficsim.base.parameters.ParameterException;
  import org.opentrafficsim.base.parameters.Parameters;
  import org.opentrafficsim.core.dsol.OtsSimulatorInterface;
  import org.opentrafficsim.core.gtu.RelativePosition.Type;
  import org.opentrafficsim.core.gtu.plan.operational.OperationalPlan;
  import org.opentrafficsim.core.gtu.plan.operational.OperationalPlanException;
  import org.opentrafficsim.core.gtu.plan.strategical.StrategicalPlanner;
  import org.opentrafficsim.core.gtu.plan.tactical.TacticalPlanner;
  import org.opentrafficsim.core.network.NetworkException;
  import org.opentrafficsim.core.perception.Historical;
  import org.opentrafficsim.core.perception.HistoricalValue;
  import org.opentrafficsim.core.perception.HistoryManager;
  import org.opentrafficsim.core.perception.PerceivableContext;
  
  import nl.tudelft.simulation.dsol.SimRuntimeException;
  import nl.tudelft.simulation.dsol.formalisms.eventscheduling.SimEvent;
  
  /**
   * Implements the basic functionalities of any GTU: the ability to move on 3D-space according to a plan.
   * <p>
   * Copyright (c) 2013-2024 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
   * BSD-style license. See <a href="https://opentrafficsim.org/docs/license.html">OpenTrafficSim License</a>.
   * </p>
   * @author <a href="https://github.com/averbraeck">Alexander Verbraeck</a>
   * @author <a href="https://github.com/peter-knoppers">Peter Knoppers</a>
   */
  public class Gtu extends LocalEventProducer
          implements HierarchicallyTyped<GtuType, Gtu>, DynamicSpatialObject, OtsLocatable, Serializable, Identifiable
  {
      /** */
      private static final long serialVersionUID = 20140822L;
  
      /** The id of the GTU. */
      private final String id;
  
      /** unique number of the GTU. */
      private final int uniqueNumber;
  
      /** the unique number counter. */
      private static int staticUNIQUENUMBER = 0;
  
      /** The type of GTU, e.g. TruckType, CarType, BusType. */
      private final GtuType gtuType;
  
      /** The simulator to schedule activities on. */
      private final OtsSimulatorInterface simulator;
  
      /** Model parameters. */
      private Parameters parameters;
  
      /** The maximum acceleration. */
      private Acceleration maximumAcceleration;
  
      /** The maximum deceleration, stored as a negative number. */
      private Acceleration maximumDeceleration;
  
      /**
       * The odometer which measures how much distance have we covered between instantiation and the last completed operational
      * plan. In order to get a complete odometer reading, the progress of the current plan execution has to be added to this
      * value.
      */
     private Historical<Length> odometer;
 
     /** The strategical planner that can instantiate tactical planners to determine mid-term decisions. */
     private final Historical<StrategicalPlanner> strategicalPlanner;
 
     /** The tactical planner that can generate an operational plan. */
     private final Historical<TacticalPlanner<?, ?>> tacticalPlanner;
 
     /** The current operational plan, which provides a short-term movement over time. */
     private final Historical<OperationalPlan> operationalPlan;
 
     /** The next move event as scheduled on the simulator, can be used for interrupting the current move. */
     private SimEvent<Duration> nextMoveEvent;
 
     /** The model in which this GTU is registered. */
     private PerceivableContext perceivableContext;
 
     /** Is this GTU destroyed? */
     private boolean destroyed = false;
 
     /** aligned or not. */
     // TODO: should be indicated with a Parameter
     public static boolean ALIGNED = true;
 
     /** aligned schedule count. */
     // TODO: can be removed after testing period
     public static int ALIGN_COUNT = 0;
 
     /** Cached speed time. */
     private double cachedSpeedTime = Double.NaN;
 
     /** Cached speed. */
     private Speed cachedSpeed = null;
 
     /** Cached acceleration time. */
     private double cachedAccelerationTime = Double.NaN;
 
     /** Cached acceleration. */
     private Acceleration cachedAcceleration = null;
 
     /** Parent GTU. */
     private Gtu parent = null;
 
     /** Children GTU's. */
     private Set<Gtu> children = new LinkedHashSet<>();
 
     /** Error handler. */
     private GtuErrorHandler errorHandler = GtuErrorHandler.THROW;
 
     /** shape of the Gtu contour. */
     private Polygon2d contour;
 
     /** Shape. */
     private final OtsShape shape;
 
     /** Sensing positions. */
     private final Map<RelativePosition.Type, RelativePosition> relativePositions = new LinkedHashMap<>();
 
     /** cached front. */
     private final RelativePosition frontPos;
 
     /** cached rear. */
     private final RelativePosition rearPos;
 
     /** contour points. */
     private final Set<RelativePosition> contourPoints = new LinkedHashSet<>();
 
     /** The maximum length of the GTU (parallel with driving direction). */
     private final Length length;
 
     /** The maximum width of the GTU (perpendicular to driving direction). */
     private final Length width;
 
     /** The maximum speed of the GTU (in the driving direction). */
     private final Speed maximumSpeed;
 
     /** Tags of the GTU, these are used for specific use cases of any sort. */
     private final Map<String, String> tags = new LinkedHashMap<>();
 
     /** Bounds. */
     private Bounds2d bounds;
 
     /**
      * @param id the id of the GTU
      * @param gtuType the type of GTU, e.g. TruckType, CarType, BusType
      * @param simulator the simulator to schedule plan changes on
      * @param perceivableContext the perceivable context in which this GTU will be registered
      * @param length the maximum length of the GTU (parallel with driving direction)
      * @param width the maximum width of the GTU (perpendicular to driving direction)
      * @param maximumSpeed Speed;the maximum speed of the GTU (in the driving direction)
      * @param front front distance relative to the reference position
      * @param centerOfGravity distance from the center of gravity to the reference position
      * @throws GtuException when the preconditions of the constructor are not met
      */
     @SuppressWarnings("checkstyle:parameternumber")
     public Gtu(final String id, final GtuType gtuType, final OtsSimulatorInterface simulator,
             final PerceivableContext perceivableContext, final Length length, final Length width, final Speed maximumSpeed,
             final Length front, final Length centerOfGravity) throws GtuException
     {
         Throw.when(id == null, GtuException.class, "id is null");
         Throw.when(gtuType == null, GtuException.class, "gtuType is null");
         Throw.when(perceivableContext == null, GtuException.class, "perceivableContext is null for GTU with id %s", id);
         Throw.when(perceivableContext.containsGtuId(id), GtuException.class,
                 "GTU with id %s already registered in perceivableContext %s", id, perceivableContext.getId());
         Throw.when(simulator == null, GtuException.class, "simulator is null for GTU with id %s", id);
 
         this.length = length;
         this.width = width;
         if (null == maximumSpeed)
         {
             throw new GtuException("maximumSpeed may not be null");
         }
         this.maximumSpeed = maximumSpeed;
 
         HistoryManager historyManager = simulator.getReplication().getHistoryManager(simulator);
         this.id = id;
         this.uniqueNumber = ++staticUNIQUENUMBER;
         this.gtuType = gtuType;
         this.simulator = simulator;
         this.odometer = new HistoricalValue<>(historyManager, this, Length.ZERO);
         this.perceivableContext = perceivableContext;
         this.perceivableContext.addGTU(this);
         this.strategicalPlanner = new HistoricalValue<>(historyManager, this);
         this.tacticalPlanner = new HistoricalValue<>(historyManager, this, null);
         this.operationalPlan = new HistoricalValue<>(historyManager, this, null);
 
         // sensor positions.
         Length dy2 = width.times(0.5);
         this.frontPos = new RelativePosition(front, Length.ZERO, Length.ZERO, RelativePosition.FRONT);
         this.relativePositions.put(RelativePosition.FRONT, this.frontPos);
         this.rearPos = new RelativePosition(front.minus(length), Length.ZERO, Length.ZERO, RelativePosition.REAR);
         this.relativePositions.put(RelativePosition.REAR, this.rearPos);
         this.relativePositions.put(RelativePosition.REFERENCE, RelativePosition.REFERENCE_POSITION);
         this.relativePositions.put(RelativePosition.CENTER,
                 new RelativePosition(Length.ZERO, Length.ZERO, Length.ZERO, RelativePosition.CENTER));
         this.bounds = new Bounds2d(front.minus(length).si, front.si, -width.si / 2.0, width.si / 2.0);
         this.shape = new OffsetRectangleShape(front.minus(length).si, front.si, -width.si / 2.0, width.si / 2.0);
 
         // Contour positions. For now, a rectangle with the four corners.
         for (int i = -1; i <= 1; i += 2)
         {
             Length x = i < 0 ? front.minus(length) : front;
             for (int j = -1; j <= 1; j += 2)
             {
                 this.contourPoints.add(new RelativePosition(x, dy2.times(j), Length.ZERO, RelativePosition.CONTOUR));
             }
         }
     }
 
     /**
      * Initialize the GTU at a location and speed, and give it a mission to fulfill through the strategical planner.
      * @param strategicalPlanner the strategical planner responsible for the overall 'mission' of the GTU, usually indicating
      *            where it needs to go. It operates by instantiating tactical planners to do the work.
      * @param initialLocation the initial location (and direction) of the GTU
      * @param initialSpeed the initial speed of the GTU
      * @throws SimRuntimeException when scheduling after the first move fails
      * @throws GtuException when the preconditions of the parameters are not met or when the construction of the original
      *             waiting path fails
      */
     @SuppressWarnings({"checkstyle:hiddenfield", "hiding", "checkstyle:designforextension"})
     public void init(final StrategicalPlanner strategicalPlanner, final OrientedPoint2d initialLocation,
             final Speed initialSpeed) throws SimRuntimeException, GtuException
     {
         Throw.when(strategicalPlanner == null, GtuException.class, "strategicalPlanner is null for GTU with id %s", this.id);
         Throw.whenNull(initialLocation, "Initial location of GTU cannot be null");
         Throw.when(Double.isNaN(initialLocation.x) || Double.isNaN(initialLocation.y), GtuException.class,
                 "initialLocation %s invalid for GTU with id %s", initialLocation, this.id);
         Throw.when(initialSpeed == null, GtuException.class, "initialSpeed is null for GTU with id %s", this.id);
         Throw.when(!getId().equals(strategicalPlanner.getGtu().getId()), GtuException.class,
                 "GTU %s is initialized with a strategical planner for GTU %s", getId(), strategicalPlanner.getGtu().getId());
 
         this.strategicalPlanner.set(strategicalPlanner);
         this.tacticalPlanner.set(strategicalPlanner.getTacticalPlanner());
 
         try
         {
             move(initialLocation);
         }
         catch (OperationalPlanException | NetworkException | ParameterException exception)
         {
             throw new GtuException("Failed to create OperationalPlan for GTU " + this.id, exception);
         }
     }
 
     /** @return the front position of the GTU, relative to its reference point. */
     public final RelativePosition getFront()
     {
         return this.frontPos;
     }
 
     /** @return the rear position of the GTU, relative to its reference point. */
     public final RelativePosition getRear()
     {
         return this.rearPos;
     }
 
     /** @return the center position of the GTU, relative to its reference point. */
     public final RelativePosition getCenter()
     {
         return this.relativePositions.get(RelativePosition.CENTER);
     }
 
     /** @return the positions for this GTU, but not the contour points. */
     public final ImmutableMap<Type, RelativePosition> getRelativePositions()
     {
         return new ImmutableLinkedHashMap<>(this.relativePositions, Immutable.WRAP);
     }
 
     /** @return the maximum length of the GTU (parallel with driving direction). */
     public final Length getLength()
     {
         return this.length;
     }
 
     /** @return the maximum width of the GTU (perpendicular to driving direction). */
     public final Length getWidth()
     {
         return this.width;
     }
 
     /** @return the maximum speed of the GTU, in the direction of movement. */
     public final Speed getMaximumSpeed()
     {
         return this.maximumSpeed;
     }
 
     @Override
     public final Bounds2d getBounds()
     {
         return this.bounds;
     }
 
     /**
      * Destructor. Don't forget to call with super.destroy() from any override to avoid memory leaks in the network.
      */
     @SuppressWarnings("checkstyle:designforextension")
     public void destroy()
     {
         OrientedPoint2d location = getLocation();
         fireTimedEvent(Gtu.DESTROY_EVENT,
                 new Object[] {getId(), new PositionVector(new double[] {location.x, location.y}, PositionUnit.METER),
                         new Direction(location.getDirZ(), DirectionUnit.EAST_RADIAN), getOdometer()},
                 this.simulator.getSimulatorTime());
 
         // cancel the next move
         if (this.nextMoveEvent != null)
         {
             this.simulator.cancelEvent(this.nextMoveEvent);
             this.nextMoveEvent = null;
         }
 
         this.perceivableContext.removeGTU(this);
         this.destroyed = true;
     }
 
     /**
      * Move from the current location according to an operational plan to a location that will bring us nearer to reaching the
      * location provided by the strategical planner. <br>
      * This method can be overridden to carry out specific behavior during the execution of the plan (e.g., scheduling of
      * triggers, entering or leaving lanes, etc.). Please bear in mind that the call to super.move() is essential, and that one
      * has to take care to handle the situation that the plan gets interrupted.
      * @param fromLocation the last known location (initial location, or end location of the previous operational plan)
      * @return whether an exception occurred
      * @throws SimRuntimeException when scheduling of the next move fails
      * @throws GtuException when there is a problem with the state of the GTU when planning a path
      * @throws NetworkException in case of a problem with the network, e.g., a dead end where it is not expected
      * @throws ParameterException in there is a parameter problem
      */
     @SuppressWarnings("checkstyle:designforextension")
     protected boolean move(final OrientedPoint2d fromLocation)
             throws SimRuntimeException, GtuException, NetworkException, ParameterException
     {
         try
         {
             Time now = this.simulator.getSimulatorAbsTime();
 
             // Add the odometer distance from the currently running operational plan.
             // Because a plan can be interrupted, we explicitly calculate the covered distance till 'now'
             Length currentOdometer;
             if (this.operationalPlan.get() != null)
             {
                 currentOdometer = this.odometer.get().plus(this.operationalPlan.get().getTraveledDistance(now));
             }
             else
             {
                 currentOdometer = this.odometer.get();
             }
 
             // Do we have an operational plan?
             // TODO discuss when a new tactical planner may be needed
             TacticalPlanner<?, ?> tactPlanner = this.tacticalPlanner.get();
             if (tactPlanner == null)
             {
                 // Tell the strategical planner to provide a tactical planner
                 tactPlanner = this.strategicalPlanner.get().getTacticalPlanner();
                 this.tacticalPlanner.set(tactPlanner);
             }
             synchronized (this)
             {
                 tactPlanner.getPerception().perceive();
             }
             OperationalPlan newOperationalPlan = tactPlanner.generateOperationalPlan(now, fromLocation);
             synchronized (this)
             {
                 this.operationalPlan.set(newOperationalPlan);
                 this.cachedSpeedTime = Double.NaN;
                 this.cachedAccelerationTime = Double.NaN;
                 this.odometer.set(currentOdometer);
             }
 
             // TODO allow alignment at different intervals, also different between GTU's within a single simulation
             if (ALIGNED && newOperationalPlan.getTotalDuration().si == 0.5)
             {
                 // schedule the next move at exactly 0.5 seconds on the clock
                 // store the event, so it can be cancelled in case the plan has to be interrupted and changed halfway
                 double tNext = Math.floor(2.0 * now.si + 1.0) / 2.0;
                 OrientedPoint2d p = (tNext - now.si < 0.5) ? newOperationalPlan.getEndLocation()
                         : newOperationalPlan.getLocation(new Duration(tNext - now.si, DurationUnit.SI));
                 this.nextMoveEvent =
                         new SimEvent<Duration>(new Duration(tNext - getSimulator().getStartTimeAbs().si, DurationUnit.SI), this,
                                 "move", new Object[] {p});
                 ALIGN_COUNT++;
             }
             else
             {
                 // schedule the next move at the end of the current operational plan
                 // store the event, so it can be cancelled in case the plan has to be interrupted and changed halfway
                 this.nextMoveEvent =
                         new SimEvent<>(now.plus(newOperationalPlan.getTotalDuration()).minus(getSimulator().getStartTimeAbs()),
                                 this, "move", new Object[] {newOperationalPlan.getEndLocation()});
             }
             this.simulator.scheduleEvent(this.nextMoveEvent);
             fireTimedEvent(Gtu.MOVE_EVENT,
                     new Object[] {getId(),
                             new PositionVector(new double[] {fromLocation.x, fromLocation.y}, PositionUnit.METER),
                             new Direction(fromLocation.getDirZ(), DirectionUnit.EAST_RADIAN), getSpeed(), getAcceleration(),
                             getOdometer()},
                     this.simulator.getSimulatorTime());
 
             return false;
         }
         catch (Exception ex)
         {
             try
             {
                 this.errorHandler.handle(this, ex);
             }
             catch (Exception exception)
             {
                 throw new GtuException(exception);
             }
             return true;
         }
     }
 
     /**
      * Interrupt the move and ask for a new plan. This method can be overridden to carry out the bookkeeping needed when the
      * current plan gets interrupted.
      * @throws SimRuntimeException when scheduling of the next move fails
      * @throws GtuException when there is a problem with the state of the GTU when planning a path
      * @throws NetworkException in case of a problem with the network, e.g., unreachability of a certain point
      * @throws ParameterException when there is a problem with a parameter
      */
     @SuppressWarnings("checkstyle:designforextension")
     protected void interruptMove() throws SimRuntimeException, GtuException, NetworkException, ParameterException
     {
         this.simulator.cancelEvent(this.nextMoveEvent);
         move(this.operationalPlan.get().getLocation(this.simulator.getSimulatorAbsTime()));
     }
 
     /** @return the id of the GTU */
     @Override
     public final String getId()
     {
         return this.id;
     }
 
     /**
      * Sets a tag, these are used for specific use cases of any sort.
      * @param tag name of the tag.
      * @param value value of the tag.
      */
     public void setTag(final String tag, final String value)
     {
         this.tags.put(tag, value);
     }
 
     /**
      * Returns the value for the given tag, these are used for specific use cases of any sort.
      * @param tag name of the tag.
      * @return value of the tag, or {@code null} if it is not given to the GTU.
      */
     public String getTag(final String tag)
     {
         return this.tags.get(tag);
     }
 
     @SuppressWarnings("checkstyle:designforextension")
     @Override
     public GtuType getType()
     {
         return this.gtuType;
     }
 
     /** @return the reference position of the GTU, by definition (0, 0, 0). */
     public final RelativePosition getReference()
     {
         return RelativePosition.REFERENCE_POSITION;
     }
 
     /** @return the simulator of the GTU. */
     public final OtsSimulatorInterface getSimulator()
     {
         return this.simulator;
     }
 
     /** @return Parameters. */
     public final Parameters getParameters()
     {
         return this.parameters;
     }
 
     /** @param parameters parameters */
     public final void setParameters(final Parameters parameters)
     {
         this.parameters = parameters;
     }
 
     /**
      * @return the planner responsible for the overall 'mission' of the GTU, usually indicating where it needs to go. It
      *         operates by instantiating tactical planners to do the work.
      */
     public StrategicalPlanner getStrategicalPlanner()
     {
         return this.strategicalPlanner.get();
     }
 
     /**
      * @param time time to obtain the strategical planner at
      * @return the planner responsible for the overall 'mission' of the GTU, usually indicating where it needs to go. It
      *         operates by instantiating tactical planners to do the work.
      */
     public StrategicalPlanner getStrategicalPlanner(final Time time)
     {
         return this.strategicalPlanner.get(time);
     }
 
     /** @return the current tactical planner that can generate an operational plan */
     public TacticalPlanner<?, ?> getTacticalPlanner()
     {
         return getStrategicalPlanner().getTacticalPlanner();
     }
 
     /**
      * @param time time to obtain the tactical planner at
      * @return the tactical planner that can generate an operational plan at the given time
      */
     public TacticalPlanner<?, ?> getTacticalPlanner(final Time time)
     {
         return getStrategicalPlanner(time).getTacticalPlanner(time);
     }
 
     /** @return the current operational plan for the GTU */
     public final OperationalPlan getOperationalPlan()
     {
         return this.operationalPlan.get();
     }
 
     /**
      * @param time time to obtain the operational plan at
      * @return the operational plan for the GTU at the given time.
      */
     public final OperationalPlan getOperationalPlan(final Time time)
     {
         return this.operationalPlan.get(time);
     }
 
     /**
      * Set the operational plan. This method is for sub classes.
      * @param operationalPlan operational plan.
      */
     protected void setOperationalPlan(final OperationalPlan operationalPlan)
     {
         this.operationalPlan.set(operationalPlan);
     }
 
     /**
      * @return the current odometer value.
      */
     public final Length getOdometer()
     {
         return getOdometer(this.simulator.getSimulatorAbsTime());
     }
 
     /**
      * @param time time to obtain the odometer at
      * @return the odometer value at given time.
      */
     public final Length getOdometer(final Time time)
     {
         synchronized (this)
         {
             if (getOperationalPlan(time) == null)
             {
                 return this.odometer.get(time);
             }
             try
             {
                 return this.odometer.get(time).plus(getOperationalPlan(time).getTraveledDistance(time));
             }
             catch (OperationalPlanException ope)
             {
                 return this.odometer.get(time);
             }
         }
     }
 
     /** @return the current speed of the GTU, along the direction of movement. */
     public final Speed getSpeed()
     {
         synchronized (this)
         {
             return getSpeed(this.simulator.getSimulatorAbsTime());
         }
     }
 
     /**
      * @param time time at which to obtain the speed
      * @return the current speed of the GTU, along the direction of movement.
      */
     public final Speed getSpeed(final Time time)
     {
         synchronized (this)
         {
             if (this.cachedSpeedTime != time.si)
             {
                 // Invalidate everything
                 this.cachedSpeedTime = Double.NaN;
                 this.cachedSpeed = null;
                 OperationalPlan plan = getOperationalPlan(time);
                 if (plan == null)
                 {
                     this.cachedSpeed = Speed.ZERO;
                 }
                 else if (time.si < plan.getStartTime().si)
                 {
                     this.cachedSpeed = plan.getStartSpeed();
                 }
                 else if (time.si > plan.getEndTime().si)
                 {
                     if (time.si - plan.getEndTime().si < 1e-6)
                     {
                         this.cachedSpeed = Try.assign(() -> plan.getSpeed(plan.getEndTime()),
                                 "getSpeed() could not derive a valid speed for the current operationalPlan");
                     }
                     else
                     {
                         throw new IllegalStateException("Requesting speed value beyond plan.");
                     }
                 }
                 else
                 {
                     this.cachedSpeed = Try.assign(() -> plan.getSpeed(time),
                             "getSpeed() could not derive a valid speed for the current operationalPlan");
                 }
                 this.cachedSpeedTime = time.si; // Do this last
             }
             return this.cachedSpeed;
         }
     }
 
     /** @return the current acceleration of the GTU, along the direction of movement. */
     public final Acceleration getAcceleration()
     {
         synchronized (this)
         {
             return getAcceleration(this.simulator.getSimulatorAbsTime());
         }
     }
 
     /**
      * @param time time at which to obtain the acceleration
      * @return the current acceleration of the GTU, along the direction of movement.
      */
     public final Acceleration getAcceleration(final Time time)
     {
         synchronized (this)
         {
             if (this.cachedAccelerationTime != time.si)
             {
                 // Invalidate everything
                 this.cachedAccelerationTime = Double.NaN;
                 this.cachedAcceleration = null;
                 OperationalPlan plan = getOperationalPlan(time);
                 if (plan == null)
                 {
                     this.cachedAcceleration = Acceleration.ZERO;
                 }
                 else if (time.si < plan.getStartTime().si)
                 {
                     this.cachedAcceleration =
                             Try.assign(() -> plan.getAcceleration(plan.getStartTime()), "Exception obtaining acceleration.");
                 }
                 else if (time.si > plan.getEndTime().si)
                 {
                     if (time.si - plan.getEndTime().si < 1e-6)
                     {
                         this.cachedAcceleration = Try.assign(() -> plan.getAcceleration(plan.getEndTime()),
                                 "getAcceleration() could not derive a valid acceleration for the current operationalPlan");
                     }
                     else
                     {
                         throw new IllegalStateException("Requesting acceleration value beyond plan.");
                     }
                 }
                 else
                 {
                     this.cachedAcceleration = Try.assign(() -> plan.getAcceleration(time),
                             "getAcceleration() could not derive a valid acceleration for the current operationalPlan");
                 }
                 this.cachedAccelerationTime = time.si;
             }
             return this.cachedAcceleration;
         }
     }
 
     /**
      * @return maximumAcceleration
      */
     public final Acceleration getMaximumAcceleration()
     {
         return this.maximumAcceleration;
     }
 
     /**
      * @param maximumAcceleration set maximumAcceleration
      */
     public final void setMaximumAcceleration(final Acceleration maximumAcceleration)
     {
         if (maximumAcceleration.le(Acceleration.ZERO))
         {
             throw new RuntimeException("Maximum acceleration of GTU " + this.id + " set to value <= 0");
         }
         this.maximumAcceleration = maximumAcceleration;
     }
 
     /**
      * @return maximumDeceleration
      */
     public final Acceleration getMaximumDeceleration()
     {
         return this.maximumDeceleration;
     }
 
     /**
      * Set the maximum deceleration.
      * @param maximumDeceleration set maximumDeceleration, must be a negative number
      */
     public final void setMaximumDeceleration(final Acceleration maximumDeceleration)
     {
         if (maximumDeceleration.ge(Acceleration.ZERO))
         {
             throw new RuntimeException("Cannot set maximum deceleration of GTU " + this.id + " to " + maximumDeceleration
                     + " (value must be negative)");
         }
         this.maximumDeceleration = maximumDeceleration;
     }
 
     /** Cache location time. */
     private Time cacheLocationTime = new Time(Double.NaN, TimeUnit.DEFAULT);
 
     /** Cached location at that time. */
     private OrientedPoint2d cacheLocation = null;
 
     @Override
     @SuppressWarnings("checkstyle:designforextension")
     public OrientedPoint2d getLocation()
     {
         synchronized (this)
         {
             if (this.operationalPlan.get() == null)
             {
                 this.simulator.getLogger().always()
                         .error("No operational plan for GTU " + this.id + " at t=" + this.getSimulator().getSimulatorTime());
                 return new OrientedPoint2d(0, 0, 0); // Do not cache it
             }
             try
             {
                 // cache
                 Time locationTime = this.simulator.getSimulatorAbsTime();
                 if (null == this.cacheLocationTime || this.cacheLocationTime.si != locationTime.si)
                 {
                     this.cacheLocationTime = null;
                     this.cacheLocation = this.operationalPlan.get().getLocation(locationTime);
                     this.cacheLocationTime = locationTime;
                 }
                 return this.cacheLocation;
             }
             catch (OperationalPlanException exception)
             {
                 return new OrientedPoint2d(0, 0, 0);
             }
         }
     }
 
     /**
      * Return the shape of a dynamic object at time 'time'. Note that the getContour() method without a time returns the
      * Minkowski sum of all shapes of the spatial object for a validity time window, e.g., a contour that describes all
      * locations of a GTU for the next time step, i.e., the contour of the GTU belonging to the next operational plan.
      * @param time the time for which we want the shape
      * @return the shape of the object at time 'time'
      */
     @Override
     public Polygon2d getContour(final Time time)
     {
         try
         {
             if (this.contour == null)
             {
                 // TODO: this should account for the reference position
                 double w = getWidth().si;
                 double l = getLength().si;
                 this.contour = new Polygon2d(new Point2d(-0.5 * l, -0.5 * w), new Point2d(-0.5 * l, 0.5 * w),
                         new Point2d(0.5 * l, 0.5 * w), new Point2d(0.5 * l, -0.5 * w));
             }
             Polygon2d s = OtsLocatable.transformContour(this.contour, this.operationalPlan.get(time).getLocation(time));
             System.out.println("gtu " + getId() + ", shape(t)=" + s);
             return s;
         }
         catch (OperationalPlanException exception)
         {
             throw new RuntimeException(exception);
         }
     }
 
     /**
      * Return the shape of the GTU for the validity time of the operational plan. Note that this method without a time returns
      * the Minkowski sum of all shapes of the spatial object for a validity time window, e.g., a contour that describes all
      * locations of a GTU for the next time step, i.e., the contour of the GTU belonging to the next operational plan.
      * @return the shape of the object over the validity of the operational plan
      */
     @Override
     public Polygon2d getContour()
     {
         try
         {
             // TODO: the actual contour of the GTU has to be moved over the path
             OtsLine2d path = this.operationalPlan.get().getPath();
             // part of the Gtu length has to be added before the start and after the end of the path.
             // we assume the reference point is within the contour of the Gtu.
             double rear = Math.max(0.0, getReference().dx().si - getRear().dx().si);
             double front = path.getLength() + Math.max(0.0, getFront().dx().si - getReference().dx().si);
             Point2d p0 = path.getLocationExtendedSI(-rear);
             Point2d pn = path.getLocationExtendedSI(front);
             List<Point2d> pList = path.getPointList();
             pList.add(0, p0);
             pList.add(pn);
             OtsLine2d extendedPath = new OtsLine2d(pList);
             List<Point2d> swath = new ArrayList<>();
             swath.addAll(extendedPath.offsetLine(getWidth().si / 2.0).getPointList());
             swath.addAll(extendedPath.offsetLine(-getWidth().si / 2.0).reverse().getPointList());
             Polygon2d s = new Polygon2d(swath);
             // System.out.println("gtu " + getId() + ", w=" + getWidth() + ", path="
             // + this.operationalPlan.get().getPath().toString() + ", shape=" + s);
             return s;
         }
         catch (Exception e)
         {
             throw new RuntimeException(e);
         }
     }
 
     @Override
     public OtsShape getShape()
     {
         return this.shape;
     }
 
     /**
      * Returns whether the GTU is destroyed.
      * @return whether the GTU is destroyed
      */
     public final boolean isDestroyed()
     {
         return this.destroyed;
     }
 
     /** @return the context to which the GTU belongs */
     public PerceivableContext getPerceivableContext()
     {
         return this.perceivableContext;
     }
 
     /**
      * Adds the provided GTU to this GTU, meaning it moves with this GTU.
      * @param gtu gtu to enter this GTU
      * @throws GtuException if the gtu already has a parent
      */
     public void addGtu(final Gtu gtu) throws GtuException
     {
         this.children.add(gtu);
         gtu.setParent(this);
     }
 
     /**
      * Removes the provided GTU from this GTU, meaning it no longer moves with this GTU.
      * @param gtu gtu to exit this GTU
      */
     public void removeGtu(final Gtu gtu)
     {
         this.children.remove(gtu);
         try
         {
             gtu.setParent(null);
         }
         catch (GtuException exception)
         {
             // cannot happen, setting null is always ok
         }
     }
 
     /**
      * Set the parent GTU.
      * @param gtu parent GTU, may be {@code null}
      * @throws GtuException if the gtu already has a parent
      */
     public void setParent(final Gtu gtu) throws GtuException
     {
         Throw.when(gtu != null && this.parent != null, GtuException.class, "GTU %s already has a parent.", this);
         this.parent = gtu;
     }
 
     /**
      * Returns the parent GTU, or {@code null} if this GTU has no parent.
      * @return parent GTU, or {@code null} if this GTU has no parent
      */
     public Gtu getParent()
     {
         return this.parent;
     }
 
     /**
      * Returns the children GTU's.
      * @return children GTU's
      */
     public Set<Gtu> getChildren()
     {
         return new LinkedHashSet<>(this.children); // safe copy
     }
 
     /**
      * @return errorHandler.
      */
     protected GtuErrorHandler getErrorHandler()
     {
         return this.errorHandler;
     }
 
     /**
      * Sets the error handler.
      * @param errorHandler error handler
      */
     public void setErrorHandler(final GtuErrorHandler errorHandler)
     {
         this.errorHandler = errorHandler;
     }
 
     /**
      * Note that destroying the next move event of the GTU can be dangerous!
      * @return nextMoveEvent the next move event of the GTU, e.g. to cancel it from outside.
      */
     public final SimEvent<Duration> getNextMoveEvent()
     {
         return this.nextMoveEvent;
     }
 
     @Override
     @SuppressWarnings("designforextension")
     public int hashCode()
     {
         final int prime = 31;
         int result = 1;
         result = prime * result + ((this.id == null) ? 0 : this.id.hashCode());
         result = prime * result + this.uniqueNumber;
         return result;
     }
 
     @Override
     @SuppressWarnings({"designforextension", "needbraces"})
     public boolean equals(final Object obj)
     {
         if (this == obj)
             return true;
         if (obj == null)
             return false;
         if (getClass() != obj.getClass())
             return false;
         Gtu other = (Gtu) obj;
         if (this.id == null)
         {
             if (other.id != null)
                 return false;
         }
         else if (!this.id.equals(other.id))
             return false;
         if (this.uniqueNumber != other.uniqueNumber)
             return false;
         return true;
     }
 
     /**
      * The event type for pub/sub indicating a move. <br>
      * Payload: [String id, DirectedPoint position, Speed speed, Acceleration acceleration, Length odometer]
      */
     public static EventType MOVE_EVENT = new EventType("GTU.MOVE",
             new MetaData("GTU move", "GTU id, position, speed, acceleration, odometer",
                     new ObjectDescriptor[] {new ObjectDescriptor("Id", "GTU Id", String.class),
                             new ObjectDescriptor("position", "position", PositionVector.class),
                             new ObjectDescriptor("direction", "direction", Direction.class),
                             new ObjectDescriptor("speed", "speed", Speed.class),
                             new ObjectDescriptor("acceleration", "acceleration", Acceleration.class),
                             new ObjectDescriptor("Odometer", "Total distance travelled since incarnation", Length.class)}));
 
     /**
      * The event type for pub/sub indicating destruction of the GTU. <br>
      * Payload: [String id, DirectedPoint lastPosition, Length odometer]
      */
     public static EventType DESTROY_EVENT = new EventType("GTU.DESTROY",
             new MetaData("GTU destroy", "GTU id, final position, final odometer",
                     new ObjectDescriptor[] {new ObjectDescriptor("Id", "GTU Id", String.class),
                             new ObjectDescriptor("position", "position", PositionVector.class),
                             new ObjectDescriptor("direction", "direction", Direction.class),
                             new ObjectDescriptor("Odometer", "Total distance travelled since incarnation", Length.class)}));
 
 }