package jutil;
/**
 * The Sim framework consists of the Simulator, Events, and
 * priority queue.
 */
public class Simulator implements java.io.Serializable {
	/**
	 * Scheduled events are placed in this queue in order
	 * of their firing times. Currently, the priority
	 * queue is implemented as a binary heap with capacity
	 * 512. Consider replacing this implementation with
	 * a sorted list or a larger binary heap.
	 */
	protected PriorityQueue events = new BinaryHeap();
	/**
	 * The simulated time.
	 */
	protected int clock = 0;
	/**
	 * Set to true to see the clock and event queue after
	 * each event is fired.
	 */
	protected boolean debug = true;
	/**
	 * Adds events to the events queue.
	 */
	public void schedule(Event e) throws OverflowException {
		events.insert(e);
	}

	public Simulator(PriorityQueue q) {
		events = q;
		clock = 0;
		debug = true;
	}
	/**
	 * Initializes event queue as a binary heap.
	 */
	public Simulator() { this(new BinaryHeap()); }
	/**
	 * Repeatedly removes the next event from the event queue, updates
	 * the clock, and fires the event. If firing the event creates a new
	 * event, then this event is scheduled.
	 */
	public void run() {
		try {
			while(!events.isEmpty()) {
				if (debug) {
					System.out.println("clock = " + clock);
					System.out.println("schedule = " + events);
				}
				Event next = (Event)events.deleteMin();
				clock = next.getFireTime();
				Event e = next.fire();
				if (e != null) schedule(e);
			}
			System.out.println("done");
		} catch(Exception e) {
			handle(e);
		}
	}
	/**
	 * Handles errors by terminating the simulation. Errors
	 * are either queue overflow or empty queue errors.
	 *
	 * @param e  The exception thrown.
	 */
	protected void handle(Exception e) {
		System.err.println(e.getMessage());
		System.exit(1);
	}
}