#include <stdio.h>
#include <string.h>
#include "date.h"


char *month_str (int month);


void init_date_1 (DATE_T *date)

/* initialization function */

{
   date -> day = 1;
   date -> month = 1;
   date -> year = 1;
}


void init_date (DATE_T *date, int d, int m, int y)

/* initialization function */

{
   date -> day = d;
   date -> month = m;
   date -> year = y;
}


int date_equal (DATE_T date1, DATE_T date2)

/* compares two dates and returns 1 if they're equal */

{
   if (date1.day == date2.day && date1.month == date2.month && date1.year == date2.year)

      return 1;

   else

      return 0;
}


int date_less_than (DATE_T date1, DATE_T date2)

/* compares two dates and returns 1 if date1 is less than date2 */

{
   if (date1.year < date2.year)

      return 1;

   else if (date1.year == date2.year) {

      if (date1.month < date2.month)

         return 1; 

      else if (date1.month == date2.month)

         if (date1.day < date2.day)

            return 1;
   }

   return 0;
}


void format_date (DATE_T date, char *str)

/* formats a date into a "month day, year" format (e.g. March 2, 2000 */

{
   sprintf (str, "%s %d, %d", month_str (date.month), date.day, date.year);
}


static int leap_year (int year)

/* returns true if year is a leap year */

{
   int result = 0;

   if (year % 400 == 0)

      result = 1;

   else if (year % 100 == 0)

      result = 0;

   else if (year % 4 == 0)

      result = 1;

   else

      result = 0;

   return result;
}


void next_day (DATE_T *date)

/* increments the current date by one day */

{
   int is_leap = 0;


   date -> day += 1;

   is_leap = leap_year (date -> month);

   /* month rollover */
   if (date -> day > month_length (date -> month, is_leap)) {

      date -> day = 1;
      date -> month += 1;
   }

   /* year rollover */
   if (date -> month > 12) {

      date -> month = 1;
      date -> year +=1;
   }
}


static int month_length (int month, int leap)

/* returns the number of days in month */

{
   int result;

   if (month == 9 || month == 4 || month == 6 || month == 11) {

      result = 30;
   }

   else if (month == 2) {

      if (leap)

         result = 29;

      else

         result = 28;
   }

   else

      result = 31;

   return result;
}


static char *month_str (month)

/* returns string name corresponding to month number */

{
   switch (month) {

      case (1)  : return "January";
      case (2)  : return "February";
      case (3)  : return "March";
      case (4)  : return "April";
      case (5)  : return "May";
      case (6)  : return "June";
      case (7)  : return "July";
      case (8)  : return "August";
      case (9)  : return "September";
      case (10) : return "October";
      case (11) : return "November";
      case (12) : return "December";
   }

   return "unknown";
}