package org.opentrafficsim.road.gtu.lane.perception.mental;
   
   import org.djunits.value.vdouble.scalar.Duration;
   import org.djutils.exceptions.Try;
   import org.opentrafficsim.base.parameters.ParameterException;
   import org.opentrafficsim.base.parameters.Parameters;
   import org.opentrafficsim.core.gtu.GTUException;
   import org.opentrafficsim.road.gtu.lane.LaneBasedGTU;
   import org.opentrafficsim.road.gtu.lane.perception.LanePerception;
  import org.opentrafficsim.road.gtu.lane.perception.RelativeLane;
  import org.opentrafficsim.road.gtu.lane.perception.categories.neighbors.NeighborsPerception;
  import org.opentrafficsim.road.gtu.lane.tactical.util.lmrs.LmrsParameters;
  
  /**
   * Lane changing task based on car-following (as gap-acceptance proxy), and an underlying consideration to include adjacent
   * lanes.
   * <p>
   * Copyright (c) 2013-2019 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 10 apr. 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 class TaskLaneChanging extends TaskHeadwayBased
  {
  
      /** Lateral consideration. */
      private final LateralConsideration lateralConsideration;
  
      /**
       * Constructor.
       * @param lateralConsideration LateralConsideration; lateral consideration
       */
      public TaskLaneChanging(final LateralConsideration lateralConsideration)
      {
          super("lane-changing");
          this.lateralConsideration = lateralConsideration;
      }
  
      /** {@inheritDoc} */
      @Override
      protected Duration getHeadway(final LanePerception perception, final LaneBasedGTU gtu, final Parameters parameters)
              throws ParameterException
      {
          NeighborsPerception neighbors = Try.assign(() -> perception.getPerceptionCategory(NeighborsPerception.class),
                  "NeighborsPerception not available.");
          double lat = Try.assign(() -> this.lateralConsideration.getConsideration(perception, gtu, parameters),
                  "Exception during lateral consideration.");
          RelativeLane lane;
          if (Math.abs(lat) < 1e-9)
          {
              return null;
          }
          if (lat < 0.0)
          {
              lane = RelativeLane.LEFT;
              lat = -lat;
          }
          else
          {
              lane = RelativeLane.RIGHT;
          }
          if (neighbors.isGtuAlongside(lane.getLateralDirectionality()))
          {
              return Duration.ZERO;
          }
          Duration h1 = neighbors.getLeaders(lane).collect(new TaskHeadwayCollector(getSpeed()));
          Duration h2 = neighbors.getFollowers(lane).collect(new TaskHeadwayCollector(getSpeed()));
          if (h1 == null)
          {
              return h2 == null ? null : h2.divideBy(lat);
          }
          if (h2 == null)
          {
              return h1 == null ? null : h1.divideBy(lat);
          }
          if (h1.eq0() && h2.eq0())
          {
              return Duration.ZERO;
          }
          return Duration.createSI(h1.si * h2.si / (lat * (h1.si + h2.si)));
      }
  
      /**
       * Lateral consideration leading to lane change task demand.
       * <p>
       * Copyright (c) 2013-2019 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 10 apr. 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 interface LateralConsideration
      {
 
         /** Desire based lateral consideration. */
         LateralConsideration DESIRE = new LateralConsideration()
         {
             @Override
             public double getConsideration(final LanePerception perception, final LaneBasedGTU gtu, final Parameters parameters)
                     throws ParameterException, GTUException
             {
                 double dLeft = gtu.getParameters().getParameter(LmrsParameters.DLEFT);
                 double dRight = gtu.getParameters().getParameter(LmrsParameters.DRIGHT);
                 if (dLeft > dRight && dLeft > 0.0)
                 {
                     return dLeft > 1.0 ? -1.0 : -dLeft;
                 }
                 else if (dRight > dLeft && dRight > 0.0)
                 {
                     return dRight > 1.0 ? 1.0 : dRight;
                 }
                 return 0.0;
             }
         };
 
         /**
          * Returns fraction of lateral consideration, &lt;0 for left lane, &gt;0 for right lane. Should be in the range -1 ...
          * 1.
          * @param perception LanePerception; perception
          * @param gtu LaneBasedGTU; gtu
          * @param parameters Parameters; parameters
          * @return double; demand of this task
          * @throws ParameterException if a parameter is missing or out of bounds
          * @throws GTUException exceptions pertaining to the GTU
          */
         double getConsideration(LanePerception perception, LaneBasedGTU gtu, Parameters parameters)
                 throws ParameterException, GTUException;
     }
 
 }