package org.opentrafficsim.road.gtu.lane.tactical.directedlanechange;
   
   import java.util.Collection;
   import java.util.Map;
   
   import org.djunits.unit.AccelerationUnit;
   import org.djunits.value.vdouble.scalar.Acceleration;
   import org.djunits.value.vdouble.scalar.DoubleScalar;
   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.gtu.GTUException;
  import org.opentrafficsim.core.gtu.RelativePosition;
  import org.opentrafficsim.core.network.LateralDirectionality;
  import org.opentrafficsim.road.gtu.lane.LaneBasedGTU;
  import org.opentrafficsim.road.gtu.lane.tactical.following.AbstractGTUFollowingModelMobil;
  import org.opentrafficsim.road.gtu.lane.tactical.following.DualAccelerationStep;
  import org.opentrafficsim.road.gtu.lane.tactical.following.GTUFollowingModelOld;
  import org.opentrafficsim.road.gtu.lane.tactical.following.HeadwayGTU;
  import org.opentrafficsim.road.network.lane.Lane;
  
  /**
   * Common code for a family of lane change models like in M. Treiber and A. Kesting <i>Traffic Flow Dynamics</i>,
   * Springer-Verlag Berlin Heidelberg 2013, pp 239-244.
   * <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/docs/license.html">OpenTrafficSim License</a>.
   * <p>
   * @version $Revision: 1401 $, $LastChangedDate: 2015-09-14 01:33:02 +0200 (Mon, 14 Sep 2015) $, by $Author: averbraeck $,
   *          initial version 4 nov. 2014 <br>
   * @author <a href="http://www.tudelft.nl/pknoppers">Peter Knoppers</a>
   */
  public abstract class AbstractDirectedLaneChangeModel implements DirectedLaneChangeModel
  {
      /** Attempt to overcome rounding errors. */
      private static Acceleration extraThreshold = new Acceleration(0.000001, AccelerationUnit.SI);
  
      /** {@inheritDoc} */
      @Override
      public final DirectedLaneMovementStep computeLaneChangeAndAcceleration(final LaneBasedGTU gtu,
              final LateralDirectionality direction, final Collection<HeadwayGTU> sameLaneGTUs,
              final Collection<HeadwayGTU> otherLaneGTUs, final Length.Rel maxDistance, final Speed speedLimit,
              final Acceleration otherLaneRouteIncentive, final Acceleration laneChangeThreshold, final Time.Rel laneChangeTime)
              throws GTUException
      {
          Map<Lane, Length.Rel> positions = gtu.positions(RelativePosition.REFERENCE_POSITION);
          Lane lane = positions.keySet().iterator().next();
          Length.Rel longitudinalPosition = positions.get(lane);
          Lane otherLane = gtu.getPerception().bestAccessibleAdjacentLane(lane, direction, longitudinalPosition);
          GTUFollowingModelOld gtuFollowingModel = gtu.getBehavioralCharacteristics().getGTUFollowingModel();
          if (null == gtuFollowingModel)
          {
              throw new Error(gtu + " has null GTUFollowingModel");
          }
          DualAccelerationStep thisLaneAccelerationSteps =
                  gtuFollowingModel.computeDualAccelerationStep(gtu, sameLaneGTUs, maxDistance, speedLimit, laneChangeTime);
          if (thisLaneAccelerationSteps.getLeaderAcceleration().getSI() < -9999)
          {
              System.out.println(gtu + " has a problem: straightAccelerationSteps.getLeaderAcceleration().getSI() < -9999");
          }
          Acceleration straightA = applyDriverPersonality(thisLaneAccelerationSteps).plus(laneChangeThreshold);
          DualAccelerationStep otherLaneAccelerationSteps =
                  null == otherLane ? null : gtuFollowingModel.computeDualAccelerationStep(gtu, otherLaneGTUs, maxDistance,
                          speedLimit, laneChangeTime);
          if (null != otherLaneAccelerationSteps
                  && otherLaneAccelerationSteps.getFollowerAcceleration().getSI() < -gtu.getBehavioralCharacteristics()
                          .getGTUFollowingModel().getMaximumSafeDeceleration().getSI())
          {
              otherLaneAccelerationSteps = AbstractGTUFollowingModelMobil.TOODANGEROUS;
          }
          Acceleration otherLaneAcceleration = null == otherLane ? null : applyDriverPersonality(otherLaneAccelerationSteps);
          if (null == otherLaneAcceleration)
          {
              // No lane change possible; this is definitely the easy case
              return new DirectedLaneMovementStep(thisLaneAccelerationSteps.getLeaderAccelerationStep(), null);
          }
          // A merge to the other lane is possible
          if (DoubleScalar.plus(otherLaneAcceleration, otherLaneRouteIncentive).plus(extraThreshold).ge(straightA))
          {
              // Merge to the other lane
              return new DirectedLaneMovementStep(otherLaneAccelerationSteps.getLeaderAccelerationStep(), direction);
          }
          else
          {
              // Stay in current lane
              return new DirectedLaneMovementStep(thisLaneAccelerationSteps.getLeaderAccelerationStep(), null);
          }
      }
  
      /**
       * Return the weighted acceleration as described by the personality. This incorporates the personality of the driver to the
       * lane change decisions.
       * @param accelerationStep DualAccelerationStep; the DualAccelerationStep that contains the AccelerationStep that the
       *            reference GTU will make and the AccelerationStep that the (new) follower GTU will make
       * @return Acceleration; the acceleration that the personality of the driver uses (in a comparison to a similarly computed
       *         acceleration in the non-, or different-lane-changed state) to decide if a lane change should be performed
       */
      public abstract Acceleration applyDriverPersonality(DualAccelerationStep accelerationStep);
  }