// compare the date1.cpp and date2.cpp code to the 
// increment_date2.cpp code from lecture 18.
// the main difference is that, in increment_date2.cpp,
// the increment_date function does not change its argument,
// but rather creates a new date object as a result.
//
// In date1.cpp, we show an INCORRECT version of 
// the increment_date function, that tries to modify its argument
// and fails, because its argument is not a pointer.
//
// In date2.cpp, we show the CORRECTED version of 
// the increment_date function, that tries to modify its argument
// and succeeds, because its argument is a pointer.


#include <stdio.h>

// note that the structure date is defined in
// the header file.
#include "date2.h"


// Note that this function works correctly.
// Compare to the incorrect version at date1.cpp
void increment_date(struct date * d1)
{
  d1->day++;
  switch(d1->month)
  {
  case 1:
  case 3:
  case 5:
  case 7:
  case 8:
  case 10:
  case 12:
    if (d1->day == 32)
    {
      d1->day = 1;
      d1->month++;
    }
    break;

  case 2:
    if (d1->day == 29)
    {
      d1->day = 1;
      d1->month++;
    }
    break;

  default:
    if (d1->day == 30)
    {
      d1->day = 1;
      d1->month++;
    }
  }

  if (d1->month == 13)
  {
    d1->month = 1;
    d1->year++;
  }
}


struct date input_date()
{
  struct date result;
  printf("please enter month day year:\n");

  scanf("%d %d %d", &(result.month), &(result.day), &(result.year));
  return result;
}


void print_date(char * name, struct date d1)
{
  printf("%s = %d/%d/%d\n", name, d1.month, d1.day, d1.year);
}


struct date copy_date(struct date input)
{
  struct date result = input;
  return result;
}


int main(void)
{
  struct date d1 = input_date();
  printf("before incrementing:\n");
  print_date("d1:", d1);

  increment_date(&d1);
  printf("\nAfter incrementing:\n");
  print_date("d1:", d1);
  // note that the date d1 has not changed.
}