import java.util.PriorityQueue;

public class Simulation
{
   private PriorityQueue<Event> eventQueue;
   private double currentTime;

   /**
      Constructs a discrete event simulation.
   */
   public Simulation()
   {
      eventQueue = new PriorityQueue<Event>();
   }

   public double getCurrentTime()
   {
      return currentTime;
   }

   /**
      Compute exponentially distributed random numbers.
      @param mean the mean of the number sequence
      @return a random number
   */
   public static double expdist(double mean)
   {  
      return -mean * Math.log(1 - Math.random());
   }

   /**
      Adds an event to the event queue.
      @param evt the event to add
   */
   public void addEvent(Event evt)
   {
      eventQueue.add(evt);
   }

   /**
      Displays intermediate results after each event.
   */
   public void display() {}

   /**
      Displays summary results after the end of the simulation.
   */
   public void displaySummary() {}

   public void run(double startTime, double endTime)
   {
      currentTime = startTime;

      while (eventQueue.size() > 0 && currentTime <= endTime)
      { 
         Event event = eventQueue.remove();
         currentTime = event.getTime();
         event.process(this);
         display();
      }
      displaySummary();
   }
}