// stats.h: the Statistics class, for objects that collect statistics.
// (There is only one such object in this program.)

class Statistics {
private:
   // The explicit initializations are not needed, but improve clarity.
   int totalArrivals;
   int customersServed;
   int balkingCustomers;
   double totalLitresSold;
   double totalLitresMissed;
   double totalWaitingTime;
   double totalServiceTime;
   static void printHeaders ();

public:

   // Constructor.
   // The list of "name (value)" pairs after the colon and before the
   // constructor body provides initial values for those data members.
   Statistics () : totalArrivals (0), customersServed (0), balkingCustomers (0)
,
      totalLitresSold (0.0), totalLitresMissed (0.0), totalWaitingTime (0.0),
      totalServiceTime (0.0)
      { printHeaders(); }

   // accumBalk: record and count a lost sale.
   void accumBalk (double litres);

   // accumSale: record and count a sale.
   void accumSale (double litres);

   // accumServiceTime: record a customer's service time.
   void accumServiceTime (double interval);

   // accumWaitingTime: record a customer's waiting time.
   void accumWaitingTime (double interval);

   // countArrival: record an arrival.
   void countArrival ();

   // snapshot: print a summary of the statistics so far.
   void snapshot ();
};