import java.util.Random;

/* An instance of this class is for the purpose of generating instances
** of the Customer class.
** Note: This class is essentially the same as that found in
** "Object-Oriented Data Structers using Java", by Dale, Joyce, and Weems,
** (4th edition, Pearson) 
*/
public class CustomerGenerator {

   // instance variables
   // ------------------

   protected int minIAT;  // minimum interarrival time
   protected int maxIAT;  // maximum interarrival time
   protected int minST;   // minimum service time
   protected int maxST;   // maximum service time

   private Random rand;
   protected int mostRecentTime;
   protected int mostRecentID;

   public CustomerGenerator(int randSeed, 
                            int minIAT, int maxIAT,
                            int minST, int maxST) {
      rand = new Random(randSeed);
      this.minIAT = minIAT;
      this.maxIAT = maxIAT;
      this.minST = minST;
      this.maxST = maxST;
      reset();
   }

   // mutator
   // -------
   public void reset() { 
      mostRecentTime = 0; mostRecentID = -1;
   }


   // method of interest
   // ------------------

   public Customer nextCustomer() {
      int interArrivalTime = minIAT + rand.nextInt(maxIAT - minIAT + 1);
      int serviceTime = minST + rand.nextInt(maxST - minST + 1);
      mostRecentTime = mostRecentTime + interArrivalTime;
      mostRecentID++;
      return new Customer(mostRecentID, mostRecentTime, serviceTime);
   }
}