package org.opentrafficsim.road.gtu.lane.control;
   
   import org.djunits.value.vdouble.scalar.Acceleration;
   import org.djunits.value.vdouble.scalar.Length;
   import org.djunits.value.vdouble.scalar.Speed;
   import org.opentrafficsim.base.parameters.ParameterException;
   import org.opentrafficsim.base.parameters.ParameterTypeDouble;
   import org.opentrafficsim.base.parameters.Parameters;
   import org.opentrafficsim.base.parameters.constraint.NumericConstraint;
  import org.opentrafficsim.core.gtu.plan.operational.OperationalPlanException;
  import org.opentrafficsim.road.gtu.lane.LaneBasedGTU;
  import org.opentrafficsim.road.gtu.lane.perception.PerceptionCollectable;
  import org.opentrafficsim.road.gtu.lane.perception.RelativeLane;
  import org.opentrafficsim.road.gtu.lane.perception.categories.InfrastructurePerception;
  import org.opentrafficsim.road.gtu.lane.perception.headway.HeadwayGTU;
  import org.opentrafficsim.road.network.speed.SpeedLimitInfo;
  
  /**
   * Class that splits the desired acceleration of a controller in a fixed linear free term, and a term for following determined
   * by the sub-class.
   * <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 Mar 14, 2019 <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 abstract class AbstractLinearFreeControl extends AbstractActuatedControl
  {
  
      /** Desired speed error gain parameter. */
      public static final ParameterTypeDouble KF =
              new ParameterTypeDouble("kf", "Desired speed error gain", 0.075, NumericConstraint.POSITIVE);
  
      /**
       * Constructor using default sensors with no delay.
       * @param delayedActuation DelayedActuation; delayed actuation
       */
      public AbstractLinearFreeControl(final DelayedActuation delayedActuation)
      {
          super(delayedActuation);
      }
  
      /** {@inheritDoc} */
      @Override
      public final Acceleration getDesiredAcceleration(final LaneBasedGTU gtu,
              final PerceptionCollectable<HeadwayGTU, LaneBasedGTU> leaders) throws ParameterException
      {
          Parameters params = gtu.getParameters();
          SpeedLimitInfo speedInfo;
          try
          {
              speedInfo = gtu.getTacticalPlanner().getPerception().getPerceptionCategory(InfrastructurePerception.class)
                      .getSpeedLimitProspect(RelativeLane.CURRENT).getSpeedLimitInfo(Length.ZERO);
          }
          catch (OperationalPlanException exception)
          {
              throw new RuntimeException("Infrastructure perception is not available.", exception);
          }
          Speed v0 = gtu.getTacticalPlanner().getCarFollowingModel().desiredSpeed(params, speedInfo);
          Acceleration a = Acceleration.createSI(params.getParameter(KF) * (v0.si - gtu.getSpeed().si));
          if (leaders.isEmpty())
          {
              return a;
          }
          return Acceleration.min(a, getFollowingAcceleration(gtu, leaders));
      }
  
      /**
       * Returns the following acceleration of the longitudinal control. This method is only invoked if there is at least 1
       * leader.
       * @param gtu LaneBasedGTU; gtu
       * @param leaders PerceptionCollectable&lt;HeadwayGTU, LaneBasedGTU&gt;; leaders
       * @return Acceleration; following acceleration of the longitudinal control
       * @throws ParameterException if parameter is not present
       */
      public abstract Acceleration getFollowingAcceleration(LaneBasedGTU gtu,
              PerceptionCollectable<HeadwayGTU, LaneBasedGTU> leaders) throws ParameterException;
  
  }