package org.opentrafficsim.road.gtu.generator.headway;
   
   import org.djunits.value.vdouble.scalar.Duration;
   import org.djunits.value.vdouble.scalar.Frequency;
   import org.opentrafficsim.base.parameters.ParameterException;
   import org.opentrafficsim.core.distributions.Generator;
   import org.opentrafficsim.core.distributions.ProbabilityException;
   
   import nl.tudelft.simulation.jstats.streams.StreamInterface;
  
  /**
   * Headway generator using independent arrivals (exponential distribution) at a fixed average rate.
   * <p>
   * Copyright (c) 2013-2024 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 <a href="https://github.com/averbraeck">Alexander Verbraeck</a>
   * @author <a href="https://tudelft.nl/staff/p.knoppers-1">Peter Knoppers</a>
   * @author <a href="https://github.com/wjschakel">Wouter Schakel</a>
   */
  public class HeadwayGenerator implements Generator<Duration>
  {
  
      /** Demand level. */
      private final Frequency demand;
  
      /** the stream information. */
      private final StreamInterface stream;
  
      /**
       * Constructor.
       * @param demand Frequency; demand.
       * @param stream StreamInterface; the stream to use for generation.
       */
      public HeadwayGenerator(final Frequency demand, final StreamInterface stream)
      {
          this.demand = demand;
          this.stream = stream;
      }
  
      /** {@inheritDoc} */
      @Override
      public Duration draw() throws ProbabilityException, ParameterException
      {
          return Duration.instantiateSI(-Math.log(this.stream.nextDouble()) / this.demand.si);
      }
  
  }