package org.opentrafficsim.road.gtu.generator.headway;
   
   import java.io.BufferedReader;
   import java.io.File;
   import java.io.FileNotFoundException;
   import java.io.FileReader;
   import java.io.IOException;
   
   import org.djunits.value.vdouble.scalar.Duration;
  import org.opentrafficsim.base.parameters.ParameterException;
  import org.opentrafficsim.core.distributions.Generator;
  import org.opentrafficsim.core.distributions.ProbabilityException;
  
  /**
   * Headway generator that takes it's input from a file.
   * <p>
   * Copyright (c) 2013-2018 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 11 jan. 2018 <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 class ListHeadways implements Generator<Duration>
  {
  
      /** Reader for the event list. */
      private final BufferedReader reader;
  
      /** Time of previous GTU. */
      private double prev = 0.0;
  
      /**
       * Constructor using file.
       * @param fileName String; file with arrival times
       */
      public ListHeadways(final String fileName)
      {
          try
          {
              this.reader = new BufferedReader(new FileReader(new File(fileName)));
          }
          catch (FileNotFoundException exception)
          {
              throw new RuntimeException(exception);
          }
      }
  
      /** {@inheritDoc} */
      @Override
      public Duration draw() throws ProbabilityException, ParameterException
      {
          try
          {
              String line = null;
              do
              {
                  line = this.reader.readLine();
                  if (null == line)
                  {
                      return null; // End of input; do not re-schedule
                  }
              }
              while (line.equals("")); // ignore blank lines
              double when = Double.parseDouble(line);
              if (when < this.prev)
              {
                  throw new RuntimeException(
                          "Arrival times from file are not in chronological order (" + when + "<" + this.prev + ").");
              }
              Duration headway = Duration.createSI(when - this.prev);
              this.prev = when;
              return headway;
          }
          catch (NumberFormatException | IOException exception)
          {
              throw new RuntimeException("Unable to read arrival time from file.", exception);
          }
      }
  
  }