/*
   testfunc15.cpp
   CIS 150
   6/9/2005
   David Klick
   
   Demonstration of more complex function usage.
*/

#include <iostream>
#include <iomanip>
#include <cctype>
using std::cin;
using std::cout;
using std::setw;
using std::setprecision;
using std::fixed;
using std::showpoint;

double calcDiscount(int qty);
double calcAmount(double priceEach, int qty,
   double discountPct, double taxRate,
   double &gross, double &discountAmt,
   double &subtot, double &taxAmt);

int main(void) {
   double price = 12.00;
   const double taxrate = .075;
   double amt;
   double disc;
   int quantity;
   
   double amtGross, amtNet, amtTax, amtDisc;
   
   do {
      cout << fixed << showpoint << setprecision(2);
      cout << "How many items do you want at $"
           << price << "? ";
      cin >> quantity;
      if (quantity < 0) {
         cout << "Error: Quantity must be at least 0\n";
      }
   } while (quantity < 0);
   
   disc = calcDiscount(quantity);
   amt = calcAmount(price, quantity, disc, taxrate,
         amtGross, amtDisc, amtNet, amtTax);
      
   cout << fixed << showpoint << setprecision(2);
   cout << "     Price: " << setw(10) << price << '\n'
        << "  Quantity: " << setw(7)  << quantity << '\n'
        << "     Gross: " << setw(10) << amtGross << '\n'
        << "Discount %: " << setw(7) << (int)(disc*100) << "%\n"
        << "Discount $: " << setw(10) << amtDisc << '\n'
        << "  Subtotal: " << setw(10) << amtNet << '\n'
        << "       Tax: " << setw(10) << amtTax << '\n'
        << "     Total: " << setw(10) << amt << '\n';
   

   return 0;
}

/*
   Returns the percentage discount given a quantity.
*/
double calcDiscount(int qty) {
   double pct = 0.0;
   if (qty >= 100) pct = 0.2;
   else if (qty >= 12) pct = 0.1;
   return pct;
}

/*
   Calculates the total amount for a bill given a price,
   a quantity, a discount percentage, and a tax rate.
   The total is returned. Four additional reference variables
   contain additional intermediate information: gross amount,
   discount amount, net after subtracting discount from gross,
   and the tax amount.
*/
double calcAmount(double priceEach, int qty,
   double discountPct, double taxRate,
   double &gross, double &discountAmt,
   double &subtot, double &taxAmt) {
   
   gross = priceEach * qty;
   discountAmt = gross * discountPct;
   subtot = gross - discountAmt;
   taxAmt = subtot * taxRate;
   return subtot + taxAmt;
}