package org.opentrafficsim.road.gtu.tactical.util.lmrs;
   
   import java.util.SortedSet;
   
   import org.djunits.value.vdouble.scalar.Acceleration;
   import org.djunits.value.vdouble.scalar.Length;
   import org.opentrafficsim.base.NamedConstants;
   import org.opentrafficsim.base.parameters.ParameterException;
   import org.opentrafficsim.base.parameters.ParameterTypes;
  import org.opentrafficsim.base.parameters.Parameters;
  import org.opentrafficsim.core.gtu.plan.operational.OperationalPlanException;
  import org.opentrafficsim.core.network.LateralDirectionality;
  import org.opentrafficsim.road.gtu.perception.RelativeLane;
  import org.opentrafficsim.road.gtu.perception.categories.neighbors.NeighborsPerception;
  import org.opentrafficsim.road.gtu.perception.object.PerceivedGtu;
  import org.opentrafficsim.road.gtu.tactical.TacticalContextEgo;
  import org.opentrafficsim.road.gtu.tactical.util.CarFollowingUtil;
  
  /**
   * Interface for LMRS gap-acceptance models.
   * <p>
   * Copyright (c) 2013-2026 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 Alexander Verbraeck
   * @author Peter Knoppers
   * @author Wouter Schakel
   */
  public interface GapAcceptance extends NamedConstants
  {
  
      /** Being informed of the model and parameters of other drivers (default LMRS). */
      GapAcceptance INFORMED = new GapAcceptance()
      {
          @Override
          public boolean acceptGap(final TacticalContextEgo context, final double desire, final LateralDirectionality lat)
                  throws ParameterException, OperationalPlanException
          {
              NeighborsPerception neighbors = context.getPerception().getPerceptionCategory(NeighborsPerception.class);
              if (neighbors.isGtuAlongside(lat))
              {
                  // gtu alongside
                  return false;
              }
  
              Acceleration threshold = context.getParameters().getParameter(ParameterTypes.B).times(-desire);
              if (!acceptEgoAcceleration(context, desire, lat, threshold))
              {
                  return false;
              }
  
              // TODO
              /*-
               * Followers and are accepted if the acceleration and speed is 0, a leader is accepted if the ego speed is 0. This
               * is in place as vehicles that provide courtesy, will decelerate for us and overshoot the stand-still distance. As
               * a consequence, they will cease cooperation as they are too close. A pattern will arise where followers slow down
               * to (near) stand-still, and accelerate again, before we could ever accept the gap.
               *
               * By accepting the gap in the moment that they reach stand-still, this vehicle can at least accept the gap at some
               * point. All of this is only a problem if the own vehicle is standing still. Otherwise the stand-still distance is
               * not important and movement of our own will create an acceptable situation.
               *
               * What needs to be done, is to find a better way to deal with the cooperation and gap-acceptance, such that this
               * hack is not required.
               */
              for (PerceivedGtu follower : neighbors.getFirstFollowers(lat))
              {
                  if (follower.getSpeed().gt0() || follower.getAcceleration().gt0() || follower.getDistance().si < 1.0)
                  {
                      Acceleration aFollow =
                              LmrsUtil.singleAcceleration(follower, follower.getDistance(), context.getSpeed(), desire);
                      if (threshold.gt(aFollow))
                      {
                          return false;
                      }
                  }
              }
  
              if (!acceptLaneChangers(context, lat, threshold))
              {
                  return false;
              }
  
              return true;
          }
  
          @Override
          public String name()
          {
              return "INFORMED";
          }
      };
  
      /** Being informed of the model and parameters of other drivers, but applying own headway value. */
      GapAcceptance EGO_HEADWAY = new GapAcceptance()
      {
          @Override
          public boolean acceptGap(final TacticalContextEgo context, final double desire, final LateralDirectionality lat)
                  throws ParameterException, OperationalPlanException
         {
             NeighborsPerception neigbors = context.getPerception().getPerceptionCategory(NeighborsPerception.class);
             if (neigbors.isGtuAlongside(lat))
             {
                 // gtu alongside
                 return false;
             }
 
             Acceleration threshold = context.getParameters().getParameter(ParameterTypes.B).times(-desire);
             if (!acceptEgoAcceleration(context, desire, lat, threshold))
             {
                 return false;
             }
 
             for (PerceivedGtu follower : neigbors.getFirstFollowers(lat))
             {
                 if (follower.getSpeed().gt0() || follower.getAcceleration().gt0())
                 {
                     // Change headway parameter
                     Parameters folParams = follower.getBehavior().getParameters();
                     folParams.setParameter(ParameterTypes.TMIN, context.getParameters().getParameter(ParameterTypes.TMIN));
                     folParams.setParameter(ParameterTypes.TMAX, context.getParameters().getParameter(ParameterTypes.TMAX));
                     Acceleration aFollow =
                             LmrsUtil.singleAcceleration(follower, follower.getDistance(), context.getSpeed(), desire);
                     folParams.resetParameter(ParameterTypes.TMIN);
                     folParams.resetParameter(ParameterTypes.TMAX);
                     if (threshold.gt(aFollow))
                     {
                         return false;
                     }
                 }
             }
 
             if (!acceptLaneChangers(context, lat, threshold))
             {
                 return false;
             }
 
             return true;
         }
 
         @Override
         public String name()
         {
             return "EGO_HEADWAY";
         }
     };
 
     /**
      * Determine whether a gap is acceptable.
      * @param context tactical information such as parameters and car-following model
      * @param desire level of lane change desire
      * @param lat lateral direction for synchronization
      * @param threshold threshold value
      * @return whether a gap is acceptable
      * @throws ParameterException if a parameter is not defined
      * @throws OperationalPlanException perception exception
      */
     private static boolean acceptEgoAcceleration(final TacticalContextEgo context, final double desire,
             final LateralDirectionality lat, final Acceleration threshold) throws ParameterException, OperationalPlanException
     {
         if (context.getSpeed().gt0())
         {
             for (PerceivedGtu leader : context.getPerception().getPerceptionCategory(NeighborsPerception.class)
                     .getFirstLeaders(lat))
             {
                 Acceleration a = LmrsUtil.singleAcceleration(context, leader.getDistance(), leader.getSpeed(), desire);
                 if (threshold.gt(a))
                 {
                     return false;
                 }
             }
         }
         return true;
     }
 
     /**
      * Determine whether a gap is acceptable regarding lane changers from the second adjacent lane to the first adjacent lane.
      * @param context tactical information such as parameters and car-following model
      * @param lat lateral direction for synchronization
      * @param threshold threshold value
      * @return whether a gap is acceptable
      * @throws ParameterException if a parameter is not defined
      * @throws OperationalPlanException perception exception
      */
     private static boolean acceptLaneChangers(final TacticalContextEgo context, final LateralDirectionality lat,
             final Acceleration threshold) throws ParameterException, OperationalPlanException
     {
         if (context.getSpeed().gt0())
         {
             NeighborsPerception neighbors = context.getPerception().getPerceptionCategory(NeighborsPerception.class);
             // Only potential lane changers in the gap to the leader in the target lane are relevant
             SortedSet<PerceivedGtu> firstLeaders = neighbors.getFirstLeaders(lat);
             Length range = Length.POS_MAXVALUE;
             if (!firstLeaders.isEmpty())
             {
                 range = Length.ZERO;
                 for (PerceivedGtu leader : firstLeaders)
                 {
                     range = Length.max(range, leader.getDistance());
                 }
             }
             for (PerceivedGtu leader : neighbors.getLeaders(new RelativeLane(lat, 2)))
             {
                 if (leader.getDistance().gt(range))
                 {
                     return true;
                 }
                 if (leader.getManeuver().isChangingLane(lat.flip()))
                 {
                     Acceleration a = CarFollowingUtil.followSingleLeader(context, leader.getDistance(), leader.getSpeed());
                     return a.ge(threshold);
                 }
             }
         }
         return true;
     }
 
     /**
      * Determine whether a gap is acceptable.
      * @param context tactical information such as parameters and car-following model
      * @param desire level of lane change desire
      * @param lat lateral direction for synchronization
      * @return whether a gap is acceptable
      * @throws ParameterException if a parameter is not defined
      * @throws OperationalPlanException perception exception
      */
     boolean acceptGap(TacticalContextEgo context, double desire, LateralDirectionality lat)
             throws ParameterException, OperationalPlanException;
 
 }