package org.opentrafficsim.road.gtu.generator;
   
   import java.io.Serializable;
   import java.rmi.RemoteException;
   import java.util.Collections;
   import java.util.LinkedHashMap;
   import java.util.LinkedHashSet;
   import java.util.LinkedList;
   import java.util.Map;
  import java.util.Queue;
  import java.util.Set;
  import java.util.SortedSet;
  import java.util.TreeSet;
  
  import javax.media.j3d.Bounds;
  import javax.naming.NamingException;
  
  import org.djunits.unit.DurationUnit;
  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.djutils.event.EventProducer;
  import org.djutils.event.EventType;
  import org.djutils.exceptions.Throw;
  import org.djutils.immutablecollections.ImmutableMap;
  import org.opentrafficsim.base.Identifiable;
  import org.opentrafficsim.base.TimeStampedObject;
  import org.opentrafficsim.base.parameters.ParameterException;
  import org.opentrafficsim.core.distributions.Generator;
  import org.opentrafficsim.core.distributions.ProbabilityException;
  import org.opentrafficsim.core.dsol.OTSSimulatorInterface;
  import org.opentrafficsim.core.geometry.OTSGeometryException;
  import org.opentrafficsim.core.gtu.GTUDirectionality;
  import org.opentrafficsim.core.gtu.GTUErrorHandler;
  import org.opentrafficsim.core.gtu.GTUException;
  import org.opentrafficsim.core.gtu.GTUType;
  import org.opentrafficsim.core.gtu.RelativePosition;
  import org.opentrafficsim.core.idgenerator.IdGenerator;
  import org.opentrafficsim.core.network.NetworkException;
  import org.opentrafficsim.road.gtu.generator.GeneratorPositions.GeneratorLanePosition;
  import org.opentrafficsim.road.gtu.generator.characteristics.LaneBasedGTUCharacteristics;
  import org.opentrafficsim.road.gtu.generator.characteristics.LaneBasedGTUCharacteristicsGenerator;
  import org.opentrafficsim.road.gtu.lane.LaneBasedGTU;
  import org.opentrafficsim.road.gtu.lane.LaneBasedIndividualGTU;
  import org.opentrafficsim.road.gtu.lane.perception.headway.HeadwayGTU;
  import org.opentrafficsim.road.gtu.lane.perception.headway.HeadwayGTUReal;
  import org.opentrafficsim.road.network.OTSRoadNetwork;
  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;
  
  import nl.tudelft.simulation.dsol.SimRuntimeException;
  import nl.tudelft.simulation.language.d3.DirectedPoint;
  
  /**
   * Lane based GTU generator. This generator generates lane based GTUs using a LaneBasedTemplateGTUType. The template is used to
   * generate a set of GTU characteristics at the times implied by the headway generator. These sets are queued until there is
   * sufficient room to construct a GTU at the specified lane locations. The speed of a construction GTU may be reduced to ensure
   * it does not run into its immediate leader GTU.
   * <p>
   * Copyright (c) 2013-2020 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
   * BSD-style license. See <a href="http://opentrafficsim.org/docs/current/license.html">OpenTrafficSim License</a>.
   * <p>
   * @version $Revision$, $LastChangedDate$, by $Author$, initial version Mar 8, 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>
   */
  public class LaneBasedGTUGenerator extends EventProducer implements Serializable, Identifiable, GtuGeneratorQueue
  {
      /** */
      private static final long serialVersionUID = 20160000L;
  
      /**
       * Event of a generated GTU. Payload: LaneBasedIndividualGTU
       */
      public static final EventType GTU_GENERATED_EVENT = new EventType("GENERATOR.GTU_GENERATED");
  
      /** FIFO for templates that have not been generated yet due to insufficient room/headway, per position, and per link. */
      private final Map<CrossSectionLink,
              Map<GeneratorLanePosition, Queue<TimeStampedObject<LaneBasedGTUCharacteristics>>>> unplacedTemplates =
                      new LinkedHashMap<>();
  
      /** Name of the GTU generator. */
      private final String id;
  
      /** Time distribution that determines the interval times between GTUs. */
      private final Generator<Duration> interarrivelTimeGenerator;
  
      /** Generates most properties of the GTUs. */
      private final LaneBasedGTUCharacteristicsGenerator laneBasedGTUCharacteristicsGenerator;
  
      /** Total number of GTUs generated so far. */
      private long generatedGTUs = 0;
  
      /** Retry interval for checking if a GTU can be placed. */
      private Duration reTryInterval = new Duration(0.1, DurationUnit.SI);
  
     /** Location and initial direction provider for all generated GTUs. */
     private final GeneratorPositions generatorPositions;
 
     /** Network. */
     private final OTSRoadNetwork network;
 
     /** Simulator. */
     private final OTSSimulatorInterface simulator;
 
     /** The way that this generator checks if it is safe to construct and place the next lane based GTU. */
     private final RoomChecker roomChecker;
 
     /** ID generator. */
     private final IdGenerator idGenerator;
 
     /** Initial distance over which lane changes shouldn't be performed. */
     private Length noLaneChangeDistance = null;
 
     /** Whether GTUs change lane instantaneously. */
     private boolean instantaneousLaneChange = false;
 
     /** GTU error handler. */
     private GTUErrorHandler errorHandler = GTUErrorHandler.THROW;
 
     /** Vehicle generation is ignored on these lanes. */
     private Set<LaneDirection> disabled = new LinkedHashSet<>();
 
     /**
      * Construct a new lane base GTU generator.
      * @param id String; name of the new GTU generator
      * @param interarrivelTimeGenerator Generator&lt;Duration&gt;; generator for the interval times between GTUs
      * @param laneBasedGTUCharacteristicsGenerator LaneBasedGTUCharacteristicsGenerator; generator of the characteristics of
      *            each GTU
      * @param generatorPositions GeneratorPositions; location and initial direction provider for all generated GTUs
      * @param network OTSRoadNetwork; the OTS network that owns the generated GTUs
      * @param simulator OTSSimulatorInterface; simulator
      * @param roomChecker RoomChecker; the way that this generator checks that there is sufficient room to place a new GTU
      * @param idGenerator IdGenerator; id generator
      * @throws SimRuntimeException when <cite>startTime</cite> lies before the current simulation time
      * @throws ProbabilityException pe
      * @throws ParameterException if drawing from the interarrival generator fails
      */
     @SuppressWarnings("parameternumber")
     public LaneBasedGTUGenerator(final String id, final Generator<Duration> interarrivelTimeGenerator,
             final LaneBasedGTUCharacteristicsGenerator laneBasedGTUCharacteristicsGenerator,
             final GeneratorPositions generatorPositions, final OTSRoadNetwork network, final OTSSimulatorInterface simulator,
             final RoomChecker roomChecker, final IdGenerator idGenerator)
             throws SimRuntimeException, ProbabilityException, ParameterException
     {
         this.id = id;
         this.interarrivelTimeGenerator = interarrivelTimeGenerator;
         this.laneBasedGTUCharacteristicsGenerator = laneBasedGTUCharacteristicsGenerator;
         this.generatorPositions = generatorPositions;
         this.network = network;
         this.simulator = simulator;
         this.roomChecker = roomChecker;
         this.idGenerator = idGenerator;
         Duration headway = this.interarrivelTimeGenerator.draw();
         if (headway != null) // otherwise no demand at all
         {
             simulator.scheduleEventRel(headway, this, this, "generateCharacteristics", new Object[] {});
         }
     }
 
     /**
      * Sets the initial distance over which lane changes shouldn't be performed.
      * @param noLaneChangeDistance Length; initial distance over which lane changes shouldn't be performed
      */
     public void setNoLaneChangeDistance(final Length noLaneChangeDistance)
     {
         this.noLaneChangeDistance = noLaneChangeDistance;
     }
 
     /**
      * Sets whether GTUs will change lane instantaneously.
      * @param instantaneous boolean; whether GTUs will change lane instantaneously
      */
     public void setInstantaneousLaneChange(final boolean instantaneous)
     {
         this.instantaneousLaneChange = instantaneous;
     }
 
     /**
      * Sets the GTU error handler.
      * @param gtuErrorHandler GTUErrorHandler; GTU error handler
      */
     public void setErrorHandler(final GTUErrorHandler gtuErrorHandler)
     {
         this.errorHandler = gtuErrorHandler;
     }
 
     /**
      * Generate the characteristics of the next GTU.
      * @throws ProbabilityException when something is wrongly defined in the LaneBasedTemplateGTUType
      * @throws SimRuntimeException when this method fails to re-schedule itself or the call to the method that tries to place a
      *             GTU on the road
      * @throws ParameterException in case of a parameter problem
      * @throws GTUException if strategical planner cannot generate a plan
      */
     @SuppressWarnings("unused")
     private void generateCharacteristics() throws ProbabilityException, SimRuntimeException, ParameterException, GTUException
     {
         synchronized (this.unplacedTemplates)
         {
             // this.generatedGTUs++;
             // XXX try a few times until a valid route has been found
             // XXX see ODApplier.draw() : LaneBasedGTUCharacteristics
             LaneBasedGTUCharacteristics characteristics = this.laneBasedGTUCharacteristicsGenerator.draw();
             /*-
             LaneBasedGTUCharacteristics characteristics = null;
             for (int tryRoute = 0; tryRoute < 10; tryRoute++)
             {
                 characteristics = this.laneBasedGTUCharacteristicsGenerator.draw();
                 if (characteristics.getRoute() != null)
                 {
                     break;
                 }
             }
             */
             // XXX this should actually have been tested in the draw() method as a valid route also links to the GTUType...
             GTUType gtuType = characteristics.getGTUType();
             // gather information on number of unplaced templates per lane, and per link, for the drawing of a new position
             Map<CrossSectionLink, Map<Integer, Integer>> unplaced = new LinkedHashMap<>();
             for (CrossSectionLink link : this.unplacedTemplates.keySet())
             {
                 Map<Integer, Integer> linkMap = new LinkedHashMap<>();
                 Map<GeneratorLanePosition, Queue<TimeStampedObject<LaneBasedGTUCharacteristics>>> linkTemplates =
                         this.unplacedTemplates.get(link);
                 for (GeneratorLanePosition lanePosition : linkTemplates.keySet())
                 {
                     linkMap.put(lanePosition.getLaneNumber(), linkTemplates.get(lanePosition).size());
                 }
                 unplaced.put(link, linkMap);
             }
             // position draw
             Speed desiredSpeed = characteristics.getStrategicalPlannerFactory().peekDesiredSpeed(gtuType,
                     this.generatorPositions.speedLimit(gtuType), characteristics.getMaximumSpeed());
             GeneratorLanePosition lanePosition =
                     this.generatorPositions.draw(gtuType, unplaced, desiredSpeed, characteristics.getRoute());
 
             // skip if disabled at this lane-direction
             Set<LaneDirection> lanes = new LinkedHashSet<>();
             for (DirectedLanePosition pos : lanePosition.getPosition())
             {
                 lanes.add(pos.getLaneDirection());
             }
             if (Collections.disjoint(this.disabled, lanes))
             {
                 queueGtu(lanePosition, characteristics);
             }
 
         }
         Duration headway = this.interarrivelTimeGenerator.draw();
         if (headway != null)
         {
             this.simulator.scheduleEventRel(headway, this, this, "generateCharacteristics", new Object[] {});
         }
     }
 
     /**
      * Check if the queue is non-empty and, if it is, try to place the GTUs in the queue on the road.
      * @param position GeneratorLanePosition; position
      * @throws SimRuntimeException should never happen
      * @throws GTUException when something wrong in the definition of the GTU
      * @throws OTSGeometryException when something is wrong in the definition of the GTU
      * @throws NetworkException when something is wrong with the initial location of the GTU
      * @throws NamingException ???
      * @throws ProbabilityException pe
      */
     @SuppressWarnings("unused")
     private void tryToPlaceGTU(final GeneratorLanePosition position) throws SimRuntimeException, GTUException, NamingException,
             NetworkException, OTSGeometryException, ProbabilityException
     {
         TimeStampedObject<LaneBasedGTUCharacteristics> timedCharacteristics;
         Queue<TimeStampedObject<LaneBasedGTUCharacteristics>> queue =
                 this.unplacedTemplates.get(position.getLink()).get(position);
 
         synchronized (queue)
         {
             timedCharacteristics = queue.peek();
         }
         if (null == timedCharacteristics)
         {
             return; // Do not re-schedule this method
         }
 
         LaneBasedGTUCharacteristics characteristics = timedCharacteristics.getObject();
         SortedSet<HeadwayGTU> leaders = new TreeSet<>();
         for (DirectedLanePosition dirPos : position.getPosition())
         {
             getFirstLeaders(dirPos.getLaneDirection(), dirPos.getPosition().neg().minus(characteristics.getFront()),
                     dirPos.getPosition(), leaders);
         }
         Duration since = this.simulator.getSimulatorTime().minus(timedCharacteristics.getTimestamp());
         Placement placement = this.roomChecker.canPlace(leaders, characteristics, since, position.getPosition());
         if (placement.canPlace())
         {
             // There is enough room; remove the template from the queue and construct the new GTU
             synchronized (queue)
             {
                 queue.remove();
             }
             placeGtu(characteristics, placement.getPosition(), placement.getSpeed());
             if (queue.size() > 0)
             {
                 this.simulator.scheduleEventNow(this, this, "tryToPlaceGTU", new Object[] {position});
             }
         }
         else if (queue.size() > 0)
         {
             this.simulator.scheduleEventRel(this.reTryInterval, this, this, "tryToPlaceGTU", new Object[] {position});
         }
     }
 
     /**
      * Adds a GTU to the generation queue. This method ignores whether vehicle generation is enabled at the location. This
      * allows an external party to govern (over some time) what vehicles are generated.
      * @param characteristics LaneBasedGTUCharacteristics; characteristics of GTU to add to the queue
      * @param position Set&lt;LaneDirection&gt;; position to generate the GTU at
      */
     public final void queueGtu(final LaneBasedGTUCharacteristics characteristics, final Set<LaneDirection> position)
     {
         // first find the correct GeneratorLanePosition
         GeneratorLanePosition genPosition = null;
         Set<LaneDirection> genSet = new LinkedHashSet<>();
         for (GeneratorLanePosition lanePosition : this.generatorPositions.getAllPositions())
         {
             for (DirectedLanePosition dirPos : lanePosition.getPosition())
             {
                 genSet.add(dirPos.getLaneDirection());
             }
             if (genSet.equals(position))
             {
                 genPosition = lanePosition;
                 break;
             }
             genSet.clear();
         }
         Throw.when(genPosition == null, IllegalStateException.class, "Position %s is not part of the generation.", position);
         try
         {
             queueGtu(genPosition, characteristics);
         }
         catch (SimRuntimeException exception)
         {
             throw new RuntimeException("Unexpected exception while scheduling tryToPlace event.", exception);
         }
     }
 
     /**
      * Places the characteristics in the queue pertaining to the position, and schedules a call to {@code tryToPlace} now if the
      * queue length is 1.
      * @param lanePosition GeneratorLanePosition; position to generate the GTU at
      * @param characteristics LaneBasedGTUCharacteristics; characteristics of GTU to add to the queue
      * @throws SimRuntimeException when an event is scheduled in the past
      */
     private void queueGtu(final GeneratorLanePosition lanePosition, final LaneBasedGTUCharacteristics characteristics)
             throws SimRuntimeException
     {
         if (!this.unplacedTemplates.containsKey(lanePosition.getLink()))
         {
             this.unplacedTemplates.put(lanePosition.getLink(), new LinkedHashMap<>());
         }
         Map<GeneratorLanePosition, Queue<TimeStampedObject<LaneBasedGTUCharacteristics>>> linkMap =
                 this.unplacedTemplates.get(lanePosition.getLink());
         if (!linkMap.containsKey(lanePosition))
         {
             linkMap.put(lanePosition, new LinkedList<>());
         }
         Queue<TimeStampedObject<LaneBasedGTUCharacteristics>> queue = linkMap.get(lanePosition);
         queue.add(new TimeStampedObject<>(characteristics, this.simulator.getSimulatorTime()));
         if (queue.size() == 1)
         {
             this.simulator.scheduleEventNow(this, this, "tryToPlaceGTU", new Object[] {lanePosition});
         }
     }
 
     /**
      * Places a GTU, regardless of whether it has room. The user of this method should verify this is the case.
      * @param characteristics LaneBasedGTUCharacteristics; characteristics
      * @param position Set&lt;DirectedLanePosition&gt;; position
      * @param speed Speed; speed
      * @throws NamingException on exception
      * @throws GTUException on exception
      * @throws NetworkException on exception
      * @throws SimRuntimeException on exception
      * @throws OTSGeometryException on exception
      */
     public final void placeGtu(final LaneBasedGTUCharacteristics characteristics, final Set<DirectedLanePosition> position,
             final Speed speed) throws NamingException, GTUException, NetworkException, SimRuntimeException, OTSGeometryException
     {
         String gtuId = this.idGenerator.nextId();
         LaneBasedIndividualGTUasedIndividualGTU.html#LaneBasedIndividualGTU">LaneBasedIndividualGTU gtu = new LaneBasedIndividualGTU(gtuId, characteristics.getGTUType(),
                 characteristics.getLength(), characteristics.getWidth(), characteristics.getMaximumSpeed(),
                 characteristics.getFront(), this.simulator, this.network);
         gtu.setMaximumAcceleration(characteristics.getMaximumAcceleration());
         gtu.setMaximumDeceleration(characteristics.getMaximumDeceleration());
         gtu.setVehicleModel(characteristics.getVehicleModel());
         gtu.setNoLaneChangeDistance(this.noLaneChangeDistance);
         gtu.setInstantaneousLaneChange(this.instantaneousLaneChange);
         gtu.setErrorHandler(this.errorHandler);
         gtu.init(characteristics.getStrategicalPlannerFactory().create(gtu, characteristics.getRoute(),
                 characteristics.getOrigin(), characteristics.getDestination()), position, speed);
         this.generatedGTUs++;
         fireEvent(GTU_GENERATED_EVENT, gtu);
     }
 
     /**
      * Adds the first GTU on the lane to the set, or any number or leaders on downstream lane(s) if there is no GTU on the lane.
      * @param lane LaneDirection; lane to search on
      * @param startDistance Length; distance from generator location (nose) to start of the lane
      * @param beyond Length; location to search downstream of which is the generator position, or the start for downstream lanes
      * @param set Set&lt;HeadwayGTU&gt;; set to add the GTU's to
      * @throws GTUException if a GTU is incorrectly positioned on a lane
      */
     private void getFirstLeaders(final LaneDirection lane, final Length startDistance, final Length beyond,
             final Set<HeadwayGTU> set) throws GTUException
     {
         LaneBasedGTU next = lane.getLane().getGtuAhead(beyond, lane.getDirection(), RelativePosition.FRONT,
                 this.simulator.getSimulatorTime());
         if (next != null)
         {
             Length headway;
             if (lane.getDirection().isPlus())
             {
                 headway = startDistance.plus(next.position(lane.getLane(), next.getRear()));
             }
             else
             {
                 headway = startDistance.plus(lane.getLane().getLength().minus(next.position(lane.getLane(), next.getRear())));
             }
             if (headway.si < 300)
             {
                 set.add(new HeadwayGTUReal(next, headway, true));
             }
             return;
         }
         ImmutableMap<Lane, GTUDirectionality> downstreamLanes =
                 lane.getLane().downstreamLanes(lane.getDirection(), this.network.getGtuType(GTUType.DEFAULTS.VEHICLE));
         for (Lane downstreamLane : downstreamLanes.keySet())
         {
             Length startDistanceDownstream = startDistance.plus(lane.getLane().getLength());
             if (startDistanceDownstream.si > 300)
             {
                 return;
             }
             GTUDirectionality dir = downstreamLanes.get(downstreamLane);
             Length beyondDownstream = dir.isPlus() ? Length.ZERO : downstreamLane.getLength();
             getFirstLeaders(new LaneDirection(downstreamLane, dir), startDistanceDownstream, beyondDownstream, set);
         }
     }
 
     /** {@inheritDoc} */
     @Override
     public final String toString()
     {
         return "LaneBasedGTUGenerator " + this.id + " on " + this.generatorPositions;
     }
 
     /**
      * @return generatedGTUs.
      */
     public final long getGeneratedGTUs()
     {
         return this.generatedGTUs;
     }
 
     /**
      * Retrieve the id of this LaneBasedGTUGenerator.
      * @return String; the id of this LaneBasedGTUGenerator
      */
     @Override
     public final String getId()
     {
         return this.id;
     }
 
     /**
      * Disable the vehicle generator during the specific time. Underlying processes such as drawing characteristics and headways
      * are continued, but simply will not result in the queuing of the GTU.
      * @param start Time; start time
      * @param end Time; end time
      * @param laneDirections Set&lt;LaneDirection&gt;; lanes to disable generation on
      * @throws SimRuntimeException if time is incorrect
      */
     public void disable(final Time start, final Time end, final Set<LaneDirection> laneDirections) throws SimRuntimeException
     {
         Throw.when(end.lt(start), SimRuntimeException.class, "End time %s is before start time %s.", end, start);
         this.simulator.scheduleEventAbs(start, this, this, "disable", new Object[] {laneDirections});
         this.simulator.scheduleEventAbs(end, this, this, "enable", new Object[0]);
     }
 
     /**
      * Disables the generator.
      * @param laneDirections Set&lt;LaneDirection&gt;; lanes to disable generation on
      */
     @SuppressWarnings("unused")
     private void disable(final Set<LaneDirection> laneDirections)
     {
         Throw.when(this.disabled != null && !this.disabled.isEmpty(), IllegalStateException.class,
                 "Disabling a generator that is already disabled is not allowed.");
         this.disabled = laneDirections;
     }
 
     /**
      * Enables the generator.
      */
     @SuppressWarnings("unused")
     private void enable()
     {
         this.disabled = new LinkedHashSet<>();
     }
 
     /**
      * Interface for class that checks that there is sufficient room for a proposed new GTU and returns the maximum safe speed
      * and position for the proposed new GTU.
      */
     public interface RoomChecker
     {
         /**
          * Return the maximum safe speed and position for a new GTU with the specified characteristics. Returns
          * {@code Placement.NO} if there is no safe speed and position. This method might be called with an empty leader set
          * such that the desired speed can be implemented.
          * @param leaders SortedSet&lt;HeadwayGTU&gt;; leaders, usually 1, possibly more after a branch
          * @param characteristics LaneBasedGTUCharacteristics; characteristics of the proposed new GTU
          * @param since Duration; time since the GTU wanted to arrive
          * @param initialPosition Set&lt;DirectedLanePosition&gt;; initial position
          * @return Speed; maximum safe speed, or null if a GTU with the specified characteristics cannot be placed at the
          *         current time
          * @throws NetworkException this method may throw a NetworkException if it encounters an error in the network structure
          * @throws GTUException on parameter exception
          */
         Placement canPlace(SortedSet<HeadwayGTU> leaders, LaneBasedGTUCharacteristics characteristics, Duration since,
                 Set<DirectedLanePosition> initialPosition) throws NetworkException, GTUException;
     }
 
     /**
      * Placement contains the information that a {@code RoomChecker} returns.
      * <p>
      * Copyright (c) 2013-2020 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved.
      * <br>
      * BSD-style license. See <a href="http://opentrafficsim.org/node/13">OpenTrafficSim License</a>.
      * <p>
      * @version $Revision$, $LastChangedDate$, by $Author$, initial version 12 jan. 2018 <br>
      * @author <a href="http://www.tbm.tudelft.nl/averbraeck">Alexander Verbraeck</a>
      * @author <a href="http://www.tudelft.nl/pknoppers">Peter Knoppers</a>
      * @author <a href="http://www.transport.citg.tudelft.nl">Wouter Schakel</a>
      */
     public static final class Placement
     {
 
         /** Value if the GTU cannot be placed. */
         public static final Placement NO = new Placement();
 
         /** Speed. */
         private final Speed speed;
 
         /** Position. */
         private final Set<DirectedLanePosition> position;
 
         /**
          * Constructor for NO.
          */
         private Placement()
         {
             this.speed = null;
             this.position = null;
         }
 
         /**
          * Constructor.
          * @param speed Speed; speed
          * @param position Set&lt;DirectedLanePosition&gt;; position
          */
         public Placement(final Speed speed, final Set<DirectedLanePosition> position)
         {
             Throw.whenNull(speed, "Speed may not be null. Use Placement.NO if the GTU cannot be placed.");
             Throw.whenNull(position, "Position may not be null. Use Placement.NO if the GTU cannot be placed.");
             this.speed = speed;
             this.position = position;
         }
 
         /**
          * Returns whether the GTU can be placed.
          * @return whether the GTU can be placed
          */
         public boolean canPlace()
         {
             return this.speed != null && this.position != null;
         }
 
         /**
          * Returns the speed.
          * @return Speed; speed
          */
         public Speed getSpeed()
         {
             return this.speed;
         }
 
         /**
          * Returns the position.
          * @return Set&lt;DirectedLanePosition&gt;; position
          */
         public Set<DirectedLanePosition> getPosition()
         {
             return this.position;
         }
 
         /** {@inheritDoc} */
         @Override
         public String toString()
         {
             return "Placement [speed=" + this.speed + ", position=" + this.position + "]";
         }
 
     }
 
     /** {@inheritDoc} */
     @Override
     public DirectedPoint getLocation() throws RemoteException
     {
         return this.generatorPositions.getLocation();
     }
 
     /** {@inheritDoc} */
     @Override
     public Bounds getBounds() throws RemoteException
     {
         return this.generatorPositions.getBounds();
     }
 
     /** {@inheritDoc} */
     @Override
     public Map<DirectedPoint, Integer> getQueueLengths()
     {
         Map<DirectedPoint, Integer> result = new LinkedHashMap<>();
         for (CrossSectionLink link : this.unplacedTemplates.keySet())
         {
             for (GeneratorLanePosition lanePosition : this.unplacedTemplates.get(link).keySet())
             {
                 result.put(lanePosition.getPosition().iterator().next().getLocation(),
                         this.unplacedTemplates.get(link).get(lanePosition).size());
             }
         }
         for (GeneratorLanePosition lanePosition : this.generatorPositions.getAllPositions())
         {
             DirectedPoint p = lanePosition.getPosition().iterator().next().getLocation();
             if (!result.containsKey(p))
             {
                 result.put(p, 0);
             }
         }
         return result;
     }
 
     /** {@inheritDoc} */
     @Override
     public Serializable getSourceId()
     {
         return this.id;
     }
 
 }