package org.opentrafficsim.demo.carFollowing;
   
   import org.djunits.unit.LengthUnit;
   import org.djunits.value.vdouble.scalar.Length;
   import org.djunits.value.vdouble.scalar.Speed;
   import org.opentrafficsim.core.network.NetworkException;
   import org.opentrafficsim.road.gtu.generator.LaneBasedGTUGenerator;
   import org.opentrafficsim.road.gtu.lane.LaneBasedGTUCharacteristics;
   import org.opentrafficsim.road.network.lane.DirectedLanePosition;
  import org.opentrafficsim.road.network.lane.Lane;
  
  /**
   * Demo implementation of the canPlace method required by the LaneBasedGTUGenerator.RoomChecker interface.
   * <p>
   * Copyright (c) 2013-2015 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 Mar 15, 2016 <br>
   * @author <a href="http://www.tudelft.nl/pknoppers">Peter Knoppers</a>
   */
  public class CanPlaceDemoCode implements LaneBasedGTUGenerator.RoomChecker
  {
      /** Maximum distance supplied to the minimumHeadway method of the GTUFollowingModel. */
      private static Length.Rel maxDistance = new Length.Rel(Double.MAX_VALUE, LengthUnit.SI);
  
      /** Precision requested of the minimumHeadway method of the GTUFollowingModel. */
      private static Length.Rel precision = new Length.Rel(0.1, LengthUnit.METER);
  
      /** {@inheritDoc} */
      @Override
      public Speed canPlace(Speed leaderSpeed, org.djunits.value.vdouble.scalar.Length.Rel headway,
              LaneBasedGTUCharacteristics laneBasedGTUCharacteristics) throws NetworkException
      {
          // This simple minded implementation returns null if the headway is less than the headway wanted for driving at
          // the current speed of the leader
          Lane lane = null;
          for (DirectedLanePosition dlp : laneBasedGTUCharacteristics.getInitialLongitudinalPositions())
          {
              if (dlp.getLane().getLaneType().isCompatible(laneBasedGTUCharacteristics.getGTUType()))
              {
                  lane = dlp.getLane();
                  break;
              }
          }
          if (null == lane)
          {
              throw new NetworkException("No " + laneBasedGTUCharacteristics.getGTUType()
                      + "-compatible lane in initial longitudinal positions");
          }
          // Use the speed limit of the first compatible lane in the initial longitudinal positions.
          Speed speedLimit = lane.getSpeedLimit(laneBasedGTUCharacteristics.getGTUType());
          Speed maximumVelocity = laneBasedGTUCharacteristics.getMaximumVelocity();
          if (headway.lt(laneBasedGTUCharacteristics.getStrategicalPlanner().getDrivingCharacteristics().getGTUFollowingModel()
                  .minimumHeadway(leaderSpeed, leaderSpeed, precision, maxDistance, speedLimit, maximumVelocity)))
          {
              return null;
          }
          return leaderSpeed;
      }
  
  }