package org.opentrafficsim.road.gtu.lane.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.lane.LaneBasedGTU;
  import org.opentrafficsim.road.gtu.lane.perception.PerceptionIterable;
  import org.opentrafficsim.road.gtu.lane.perception.headway.Headway;
  import org.opentrafficsim.road.network.speed.SpeedLimitInfo;
  
  /**
   * Default implementation where desired speed and headway are pre-calculated for car-following.
   * <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/docs/current/license.html">OpenTrafficSim License</a>.
   * <p>
   * @version $Revision$, $LastChangedDate$, by $Author$, initial version Apr 2016 <br>
   * @author <a href="http://www.transport.citg.tudelft.nl">Wouter Schakel</a>
   */
  public abstract class AbstractCarFollowingModel implements CarFollowingModel
  {
  
      /** Desired headway model. */
      private DesiredHeadwayModel desiredHeadwayModel;
  
      /** Desired speed model. */
      private DesiredSpeedModel desiredSpeedModel;
  
      /**
       * @param desiredHeadwayModel DesiredHeadwayModel; desired headway model
       * @param desiredSpeedModel DesiredSpeedModel; desired speed model
       */
      public AbstractCarFollowingModel(final DesiredHeadwayModel desiredHeadwayModel, final DesiredSpeedModel desiredSpeedModel)
      {
          this.desiredHeadwayModel = desiredHeadwayModel;
          this.desiredSpeedModel = desiredSpeedModel;
      }
  
      /** {@inheritDoc} */
      @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);
      }
  
      /** {@inheritDoc} */
      @Override
      public final Speed desiredSpeed(final Parameters parameters, final SpeedLimitInfo speedInfo) throws ParameterException
      {
          Throw.whenNull(parameters, "Parameters may not be null.");
          Throw.whenNull(speedInfo, "Speed limit info may not be null.");
          return this.desiredSpeedModel.desiredSpeed(parameters, speedInfo);
      }
  
      /** {@inheritDoc} */
      @Override
      public final Acceleration followingAcceleration(final Parameters parameters, final Speed speed,
              final SpeedLimitInfo speedLimitInfo, final PerceptionIterable<? extends Headway> leaders) throws ParameterException
      {
          Throw.whenNull(parameters, "Parameters may not be null.");
          Throw.whenNull(speed, "Speed may not be null.");
          Throw.whenNull(speedLimitInfo, "Speed limit info may not be null.");
          Throw.whenNull(leaders, "Leaders may not be null.");
          // 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, speedLimitInfo),
                  desiredHeadway(parameters, speed), leaders);
          return acc;
      }
  
      /**
       * Determination of car-following acceleration, possibly based on multiple leaders.
       * @param parameters Parameters; parameters
       * @param speed Speed; current speed
       * @param desiredSpeed Speed; desired speed
       * @param desiredHeadway Length; desired headway
       * @param leaders PerceptionIterable&lt;? extends Headway&gt;; 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 Headway> leaders) throws ParameterException;
  
      /** {@inheritDoc} */
      @SuppressWarnings("checkstyle:designforextension")
      @Override
      public String toString()
      {
         return getLongName();
     }
 
     /** {@inheritDoc} */
     @Override
     public final void init(final LaneBasedGTU gtu)
     {
         if (this.desiredHeadwayModel instanceof Initialisable)
         {
             ((Initialisable) this.desiredHeadwayModel).init(gtu);
         }
         if (this.desiredSpeedModel instanceof Initialisable)
         {
             ((Initialisable) this.desiredSpeedModel).init(gtu);
         }
     }
 
 }