/**
 * ch6sam2.c
 * written by Derrick Stolee
 */
 
#include <stdio.h>

double buyCoffee(int *numCups, int* coupon); 

int main(void)
{
	int numCoffees;
	int bought = 0;
	int coupon = 0;
	double totalAmount = 0.0;
	double cost;
	
	printf("How many coffees would you like to buy? ");
	scanf("%d", &numCoffees);
	
	int i;
	for ( i = 0; i < numCoffees; i++ )
	{
		cost = buyCoffee(&bought, &coupon);
		
		printf("Bought a coffee for $%1.2lf\n",cost);
		
		totalAmount = totalAmount + cost;
	}
	
	printf("Bought %d coffees for $%1.2lf", bought, totalAmount);
	
	if ( coupon )
	{
		printf(" and I have a coupon!\n");
	}
	else
	{
		printf("\n");
	}
	
	return 0;	
}


/* request to buy some coffee, with a possible coupon */
double buyCoffee(int *numCups, int* coupon)
{
	/* modify the number of cups so far */
	(*numCups) = (*numCups)+1;

	/* did they have a coupon? */
	if ( *coupon == 1 )
	{
		/* use the coupon */
		(*coupon) = 0;
		return 0.0;	
	}
	else if ( *numCups % 5 == 0 )
	{
		/* add a coupon with this purchace? */
		(*coupon) = 1;
	}
	
	/* charge normal price */
	return 1.75;
}