package org.opentrafficsim.road.gtu.tactical.following;
   
   import org.djunits.unit.AccelerationUnit;
   import org.djunits.value.vdouble.scalar.Acceleration;
   import org.djunits.value.vdouble.scalar.Length;
   import org.djunits.value.vdouble.scalar.Speed;
   import org.djutils.exceptions.Throw;
   import org.opentrafficsim.base.parameters.ParameterException;
   import org.opentrafficsim.base.parameters.Parameters;
  import org.opentrafficsim.road.gtu.LaneBasedGtu;
  import org.opentrafficsim.road.gtu.perception.PerceptionIterable;
  import org.opentrafficsim.road.gtu.perception.object.PerceivedObject;
  import org.opentrafficsim.road.network.speed.SpeedLimits;
  
  /**
   * Default implementation where desired speed and headway are pre-calculated for car-following.
   * <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 Wouter Schakel
   */
  public abstract class AbstractCarFollowingModel implements CarFollowingModel
  {
  
      /** Desired headway model. */
      private DesiredHeadwayModel desiredHeadwayModel;
  
      /** Desired speed model. */
      private DesiredSpeedModel desiredSpeedModel;
  
      /**
       * Constructor.
       * @param desiredHeadwayModel desired headway model
       * @param desiredSpeedModel desired speed model
       */
      public AbstractCarFollowingModel(final DesiredHeadwayModel desiredHeadwayModel, final DesiredSpeedModel desiredSpeedModel)
      {
          this.desiredHeadwayModel = desiredHeadwayModel;
          this.desiredSpeedModel = desiredSpeedModel;
      }
  
      @Override
      public final Length desiredHeadway(final Parameters parameters, final Speed speed) throws ParameterException
      {
          Throw.whenNull(parameters, "Parameters may not be null.");
          Throw.whenNull(speed, "Speed may not be null.");
          return this.desiredHeadwayModel.desiredHeadway(parameters, speed);
      }
  
      @Override
      public final Speed desiredSpeed(final Parameters parameters, final SpeedLimits speedLimits, final Speed maxVehicleSpeed)
              throws ParameterException
      {
          return this.desiredSpeedModel.desiredSpeed(parameters, speedLimits, maxVehicleSpeed);
      }
  
      @Override
      public final Acceleration followingAcceleration(final Parameters parameters, final Speed speed,
              final SpeedLimits speedLimits, final Speed maxVehicleSpeed,
              final PerceptionIterable<? extends PerceivedObject> leaders) throws ParameterException
      {
          // Catch negative headway
          if (!leaders.isEmpty() && leaders.first().getDistance().si <= 0)
          {
              return new Acceleration(Double.NEGATIVE_INFINITY, AccelerationUnit.SI);
          }
          // Forward to method with desired speed and headway predetermined by this car-following model.
          Acceleration acc = followingAcceleration(parameters, speed, desiredSpeed(parameters, speedLimits, maxVehicleSpeed),
                  desiredHeadway(parameters, speed), leaders);
          return acc;
      }
  
      /**
       * Sets the desired speed model.
       * @param model new model
       * @return the model that was set before this method was called
       */
      public DesiredSpeedModel setDesiredSpeedModel(final DesiredSpeedModel model)
      {
          DesiredSpeedModel old = this.desiredSpeedModel;
          this.desiredSpeedModel = model;
          return old;
      }
  
      /**
       * Determination of car-following acceleration, possibly based on multiple leaders.
       * @param parameters parameters
       * @param speed current speed
       * @param desiredSpeed desired speed
       * @param desiredHeadway desired headway
       * @param leaders set of leader headways (guaranteed positive) and speeds, ordered by headway (closest first)
       * @return car-following acceleration
       * @throws ParameterException if parameter exception occurs
       */
      protected abstract Acceleration followingAcceleration(Parameters parameters, Speed speed, Speed desiredSpeed,
              Length desiredHeadway, PerceptionIterable<? extends PerceivedObject> leaders) throws ParameterException;
  
      @SuppressWarnings("checkstyle:designforextension")
     @Override
     public String toString()
     {
         return getLongName();
     }
 
     @Override
     public final void init(final LaneBasedGtu gtu)
     {
         if (this.desiredHeadwayModel instanceof Initialisable initialisable)
         {
             initialisable.init(gtu);
         }
         if (this.desiredSpeedModel instanceof Initialisable initialisable)
         {
             initialisable.init(gtu);
         }
     }
 
 }