package umontreal.iro.lecuyer.util;

/**
 * AbstractChrono is a class that acts as an interface to
 * the system clock and calculates the CPU or system time consumed by
 * parts of a program.
 * 
 * 

 * Every object of class AbstractChrono acts as an independent stopwatch.
 * Several AbstractChrono objects can run at any given time.
 * The method {@link #init init} resets the stopwatch to zero,
 * {@link #getSeconds getSeconds}, {@link #getMinutes getMinutes} and {@link #getHours getHours}
 *  return its current reading,
 * and {@link #format format} converts this reading to a {@link String}.
 * The returned value includes the execution time of the method
 * from AbstractChrono.
 * 
 * 

 * Below is an example of how it may be used.
 * A stopwatch named timer is constructed (and initialized).
 * When 2.1 seconds of CPU time have been consumed,
 * the stopwatch is read and reset to zero.
 * Then, after an additional 330 seconds (or 5.5 minutes) of CPU time,
 * the stopwatch is read again and the value is printed to the output
 * in minutes.
 * 
 * 

 * 
 * 
 * 

 * AbstractChrono timer = new Chrono();
 * 

 * 
 * 
 * 

 * 
 * 
 * 

 * 
   suppose 2.1 CPU seconds are used here
 * 

 * 

 * 
 * 
 * 

 * 
 * double t = timer.getSeconds();               // Here, t = 2.1
 * 

 * timer.init();
 * 

 * t = timer.getSeconds();                      // Here, t = 0.0
 * 

 * 
 * 
 * 

 * 
 * 
 * 

 * 
   suppose 330 CPU seconds are used here.
 * 

 * 

 * 
 * 
 * 

 * 
 * t = timer.getMinutes();                      // Here, t = 5.5
 * 

 * System.out.println (timer.format());         // Prints: 0:5:30.00
 * 

 * 
 * 
 */
public abstract class AbstractChrono {

   private long m_second;
   private long m_microsec;
   private long[] now = new long[2];
   // tab[0] = seconds, tab[1] = microseconds

   protected abstract void getTime (long[] tab);


   public AbstractChrono() {
   }


   /**
    * Initializes this AbstractChrono to zero.
    * 
    */
   public void init()  {
      getTime (now);
      m_second = now[0];
      m_microsec = now[1];
   }


   /**
    * Returns the CPU time in seconds used by the program since the last call to
    *   {@link #init init} for this AbstractChrono.
    *  
    * @return the number of seconds
    * 
    */
   public double getSeconds() {
      getTime (now);
      double time = (now[1] - m_microsec)/1000000.0
             + (now[0] - m_second);
      return time;
   }


   /**
    * Returns the CPU time in minutes used by the program since the last call to
    *   {@link #init init} for this AbstractChrono.
    *  
    * @return the number of minutes
    * 
    */
   public double getMinutes() {
      getTime (now);
      double time = (now[1] - m_microsec)/1000000.0
             + (now[0] - m_second);
      return time*1.666666667*0.01;
   }


   /**
    * Returns the CPU time in hours used by the program since the last call to
    *   {@link #init init} for this AbstractChrono.
    *  
    * @return the number of hours
    * 
    */
   public double getHours() {
      getTime (now);
      double time = (now[1] - m_microsec)/1000000.0
             + (now[0] - m_second);
      return time*2.777777778*0.0001;
   }


   /**
    * Converts the CPU time used by the program since its last
    *    call to {@link #init init} for this AbstractChrono to a
    *   {@link String} in  the HH:MM:SS.xx format.
    *   
    * @return the string representation of the CPU time
    * 
    */
   public String format() {
      return format (getSeconds());
   }


   /**
    * Converts the time time, given in seconds, to a
    *   {@link String} in the HH:MM:SS.xx format.
    *   
    * @return the string representation of the time time
    * 
    */
   public static String format (double time) {
      int second, hour, min, centieme;
      hour = (int)(time/3600.0);
      if (hour > 0) time -= ((double)hour*3600.0);
      min = (int)(time/60.0);
      if (min > 0) time -= ((double)min*60.0);
      second = (int)time;
      centieme = (int)(100.0*(time - (double)second) + 0.5);
      return String.valueOf (hour) + ":" +
                      min + ":" +
                      second + "." +
                      centieme;
   }

}