/* An instance of this class represents a customer who arrives 
** at a place of business (e.g., a bank), waits in a queue for
** service, receives that service, and then departs.
** The relevant facts about such a customer is their arrival time,
** the amount of time that servicing them takes, and the time at
** which service has been completed.
**
** 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 Customer {

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

   protected final int ID;
   protected final int arrivalTime;
   protected final int serviceDuration;
   protected int finishTime;


   // constructor
   // -----------

   public Customer(int ID, int arriveTime, int servDur) {
      this.ID = ID;
      this.arrivalTime = arriveTime;
      this.serviceDuration = servDur;
      this.finishTime = -1;  // dummy value indicating "unknown"
   }

   // observers
   // ---------

   public int ID() { return ID; }
   public int arrivalTime() { return arrivalTime; }
   public int serviceDuration() { return serviceDuration; }
   public int finishTime() { return finishTime; }

   /* Returns how many units of time this customer waited 
   ** before service began to be provided.
   ** pre: recordFinishTime() has been called
   */
   public int waitTime() {
      return finishTime - (serviceDuration + arrivalTime);
   }

   @Override
   public String toString() {
      String result = "ID:" + ID + 
                      "; Arrival:" + arrivalTime +
                      "; Service:" + serviceDuration;
      if (finishTime != -1) {
         result = result + 
                  "; Finish:" + finishTime +
                  "; Waiting:" + waitTime();
      }
      return result + '\n';
   }
   
   // mutator
   // -------

   /* Sets this customer's finish time to the value indicated.
   */
   public void recordFinishTime(int t) { finishTime = t; }

}