/********************************************************************/
/* CS167 C Programming                                              */
/* the wood screw inventory                                         */
/* practice with functions as modules and as abstractions           */
/* Roger Hartley, Spring 1998                                       */
/********************************************************************/

#include <stdio.h>

#define SIZE 5              /* the size of the inventory and cost arrays */
#define SENTINEL 9999       /* typed by the user as a screws size */

/* global constant array of costs (in dollars) of each screws size
   the array is ordered by screw size 4, 6, 8, 10, 12 */
const float screwCost[SIZE] = { 0.3, 0.35, 0.45, 0.5, 0.65 };

int calculateIndex(int size, int max) {
  /* there is a simple relationship between screw size and the array index */
  int index = size / 2 - 2;
  /* if we are passed an invalid screw size, the index will also be
     invalid, so return -1 */
  if (index < 0 || index >= max)
    return -1;
  else
    return index;
}

int calculateSize(int i) {
  /* the inverse of calulcateIndex - no checking is necessary, since
     this will never be passed an invalid index */
  return (i + 2) * 2;
}

/* Update does the work of altering the qantity of screws on hand
   by adding the passed value (read from the user) to the quantity 
   stored in the inventory array - this might be postiive(an increase)
   or negative (a decrease) */
void Update(int inv[], int arraySize, int screwSize, int screwQuant) {
  int index = calculateIndex(screwSize, arraySize);
  if (index != -1)
    inv[index] += screwQuant;
  else {
    printf("Sorry, the screw size you typed was invalid\n");
    printf("the line will be ignored\n");
  }
}

/* Input does the work of reading values from the user (screw size and
   quantity) in a loop, and passing the values to Update - the end of
   input is signified by typing 9999 as a screw size - note that a 
   quantity must also be typed with the sentinel, but is ignored */
void Input(int inv[]) {
  int screwSize, screwQuant;
  
  printf("Type any number of lines, each with a screw size (4, 6, 8, 10 or 12)\n");
  printf("and a quantity (+ or -), separated by a space\n");
  scanf("%d%d", &screwSize, &screwQuant);  
  while (screwSize != SENTINEL) {
    Update(inv, SIZE, screwSize, screwQuant);
    scanf("%d%d", &screwSize, &screwQuant);
  }
}

/* Print displays a table of sizes, quantity on hand, and the worth 
   of the inventory of each screw size - it also accumulates the 
   total worth of the whole inventory and displays this moneyamount */
void Print(int inv[], int size) {
  int i;
  int quant;
  float invCost, totalCost = 0.0;

  printf("%5s%6s%10s\n", "Size", "Quant", "Worth ($)");
  for (i = 0; i < size; i++) {
    quant = inv[i];
    invCost = quant * screwCost[i];
    totalCost += invCost;
    printf("%5d%6d%10.2f\n", calculateSize(i), inv[i], invCost);
  }
  printf("\nTotal inventory worth is $%-10.2f\n", totalCost);
}

/* the main program just declares the inventory array, initializes it 
   to all zeros, calls Input and Print */
int main() {
  int inventory[SIZE] = { 0 };

  Input(inventory);
  Print(inventory, SIZE);
}