package org.opentrafficsim.road.gtu.lane.perception.mental;
   
   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 nl.tudelft.simulation.dsol.simulators.SimulatorInterface;
  
  /**
   * Class for exponential demand.
   */
  public class ExponentialTask extends AbstractTask
  {
      /** Initial level of task demand. */
      private final double initialTaskDemand;
  
      /** Additional task demand. */
      private final double additionalTaskDemand;
  
      /** Time scale at which task demand changes from the initial to the final value. */
      private final double tau;
  
      /** Start time of the distraction. */
      private final double start;
  
      /**
       * Constructor.
       * @param id String; id
       * @param initialTaskDemand double; initial level of task demand
       * @param finalTaskDemand double; final level of task demand
       * @param tau double; time scale at which task demand changes from the initial to the final value
       * @param simulator SimulatorInterface.TimeDoubleUnit; simulator
       */
      public ExponentialTask(final String id, final double initialTaskDemand, final double finalTaskDemand, final double tau,
              final SimulatorInterface.TimeDoubleUnit simulator)
      {
          super(id);
          this.initialTaskDemand = initialTaskDemand;
          this.additionalTaskDemand = finalTaskDemand - initialTaskDemand;
          this.tau = tau;
          this.start = simulator.getSimulatorTime().si;
      }
  
      /** {@inheritDoc} */
      @Override
      public double calculateTaskDemand(final LanePerception perception, final LaneBasedGTU gtu, final Parameters parameters)
              throws ParameterException, GTUException
      {
          double t = gtu.getSimulator().getSimulatorTime().si - this.start;
          return this.initialTaskDemand + this.additionalTaskDemand * (1.0 - Math.exp(-t / this.tau));
      }
  
  }