package algs13;
import stdlib.*;

public class XMM1Queue {
  public static void main(String[] args) {
    int SIZE = 60;
    args = new String[] { ".2", ".333" }; SIZE = 60;
    //args = new String[] { ".2", ".25" };  SIZE = 120;
    //args = new String[] { ".2", ".21" };  SIZE = 240;

    double lambda = Double.parseDouble(args[0]);  // arrival rate
    double mu     = Double.parseDouble(args[1]);  // service rate

    Queue<Double> q = new Queue<>();            // arrival times of customers
    double nextArrival   = StdRandom.exp(lambda);     // time of next arrival
    double nextDeparture = Double.POSITIVE_INFINITY;  // time of next departure

    // histogram object
    XHistogram hist = new XHistogram(SIZE);

    // simulate an M/M/1 queue
    while (true) {

      // it's an arrival
      if (nextArrival <= nextDeparture) {
        if (q.isEmpty()) nextDeparture = nextArrival + StdRandom.exp(mu);
        q.enqueue(nextArrival);
        nextArrival += StdRandom.exp(lambda);
      }

      // it's a departure
      else {
        double wait = nextDeparture - q.dequeue();
        StdOut.format("Wait = %6.2f, queue size = %d\n", wait, q.size());
        hist.addDataPoint(Math.min(SIZE-1,  (int) (Math.round(wait))));
        StdDraw.clear ();
        hist.draw ();
        StdDraw.show (1);
        if (q.isEmpty()) nextDeparture = Double.POSITIVE_INFINITY;
        else             nextDeparture += StdRandom.exp(mu);

      }
    }

  }

}