/** Simulates a waiting line. 
    @author Frank M. Carrano
    @author Timothy M. Henry
    @version 5.0
*/
public class WaitLine
{
   private QueueInterface<Customer> line;
   private int numberOfArrivals;
   private int numberServed;
   private int totalTimeWaited;

   public WaitLine()
   {
      line = new LinkedQueue<>();
      reset();
   } // end default constructor

   /** Simulates a waiting line with one serving agent.
       @param duration  The number of simulated minutes.
       @param arrivalProbability  A real number between 0 and 1, and the
                                  probability that a customer arrives at
                                  a given time
       @param maxTransactionTime  The longest transaction time for a
                                  customer */ 
   public void simulate(int duration, double arrivalProbability, 
                        int maxTransactionTime)
   {
      int transactionTimeLeft = 0;

      for (int clock = 0; clock < duration; clock++)
      {
         if (Math.random() < arrivalProbability)
         {
            numberOfArrivals++;
            int transactionTime = (int)(Math.random() * maxTransactionTime + 1);
            Customer nextArrival = new Customer(clock, transactionTime, 
                                                numberOfArrivals);
            line.enqueue(nextArrival);
            System.out.println("Customer " + numberOfArrivals +
                               " enters line at time " + clock +
                               ". Transaction time is " + transactionTime);
         } // end if

         if (transactionTimeLeft > 0)
            transactionTimeLeft--;
         else if (!line.isEmpty())
         {
            Customer nextCustomer = line.dequeue();
            transactionTimeLeft = nextCustomer.getTransactionTime() - 1;
            int timeWaited = clock - nextCustomer.getArrivalTime();
            totalTimeWaited = totalTimeWaited + timeWaited;
            numberServed++;
            System.out.println("Customer " + nextCustomer.getCustomerNumber() +
                               " begins service at time " + clock +
                               ". Time waited is " + timeWaited);
         } // end if
      } // end for
   } // end simulate

   /** Displays summary results of the simulation. */ 
   public void displayResults()
   {
      System.out.println();
      System.out.println("Number served = " + numberServed);
      System.out.println("Total time waited = " + totalTimeWaited);
      double averageTimeWaited = ((double)totalTimeWaited) / numberServed;
      System.out.println("Average time waited = " + averageTimeWaited);
      int leftInLine = numberOfArrivals - numberServed;
      System.out.println("Number left in line = " + leftInLine);
   } // end displayResults

   /** Initializes the simulation. */ 
   public final void reset()
   {
      line.clear();
      numberOfArrivals = 0;
      numberServed = 0;
      totalTimeWaited = 0;
   } // end reset
} // end WaitLine