#include <stdio.h>

#include "dates.h"

static int tosod(
	int hour, 
	int minute, 
	int second
);

static int todoy(
	int year,
	int month,
	int day
);

static void to_mmdd (
	int year, 
	int doy, 
	int *month, 
	int *day
);

#define NINT(t)         ((int) ((t<0) ? t-.5 : t+.5))

/******************************************************/
double DateValue(year, month, day, hour, minute, second)
int year, month, day, hour, minute, second;
{
	long sod, soy;
	int  doy;
	double d;

/* First get the day of the year */

	doy = todoy (year, month, day);
	if (doy == -1) return (-1.0);

/* Get the second of the day */

	sod = tosod(hour, minute, second);
	if (sod == -1) return (-1.0);

/* Get second of the year */

	soy = (doy-1) * SECONDS_DAY + sod;

/* Get Fraction of year */

	if (year %4 == 0) 
		d = (double) year + (double) soy / SECONDS_YEAR_LEAP;
	else
		d = (double) year + (double) soy / SECONDS_YEAR;

	return (d);
}

/*********************************************************/
/* Convert hour, minute, second to second of the day.
 * Expects hour to be form 0 to 23.
 */

static int tosod(hour, minute, second)
int hour, minute, second;
{
	int n, bad=0;

	if (hour < 0 || hour > 23) {
		fprintf (stderr, "XkDateValue: Got bad hour value: %d\n", hour);
		bad = 1;
	}

	if (minute < 0 || minute > 59) {
		fprintf (stderr, "XkDateValue: Got bad minute value: %d\n", minute);
		bad = 1;
	}
	if (second < 0 || second > 59) {
		fprintf (stderr, "XkDateValue: Got bad second value: %d\n", second);
		bad = 1;
	}

	if (bad) return (-1);

	n = hour*3600 + minute*60 + second;
	return (n);
}

/*********************************************************************/
static int todoy(year,month,day)
int year,month,day;

/*  convert year, month, day to year, day of year
    returns the day of year if succesful, -1 otherwise */

{
   static int mona[11] = {31,59,90,120,151,181,212,243,273,304,334};
   int doy;
 
   if (month < 1 || month > 12) {
	fprintf (stderr, "XkDateValue: Got bad month value: %d\n", month);
   }
   if (day <1 || day > 31 ) {
	fprintf (stderr, "XkDateValue: Got bad day value: %d\n", day);
   }

   if (month < 1 || month > 12 || day <1 || day > 31 ) return -1;
 
   if (month == 1) 
      doy = day;
   else {
      doy = mona[month-2]+day;
      if ((year % 4 ==0) && month >2) doy=doy+1; 
   }
   return doy;
}

/*********************************************************************/
void GetCalendarDate(d, year, month, day, hour, minute, second)
double d;
int *year, *month, *day, *hour, *minute, *second;
{
	int y, nsec, ndays, doy, mon, dy, h, m, s, nsecs;
	double f;


	y = (int) d;

	f = d - y;
	if (y % 4 == 0) 
		nsec = NINT( f * SECONDS_YEAR_LEAP );
	else
		nsec = NINT( f * SECONDS_YEAR );

	ndays = nsec / SECONDS_DAY;
	doy = ndays + 1;

	to_mmdd (y, doy, &mon, &dy);

	nsecs = nsec - (ndays*SECONDS_DAY);
	h = nsecs / 3600;
	m = (nsecs - (h * 3600)) / 60;
	s = nsecs - (h * 3600) - (m * 60);

	*year = y;
	*month = mon;
	*day = dy;
	*hour = h;
	*minute = m;
	*second = s;
}
/**************************************************************************/
static void to_mmdd (year, doy, month, day)
int year, doy, *month, *day;
{
	static int mona[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
	int idoy, imon;

	idoy=doy;
	imon=0;
	if (year%4 == 0) 
		mona[1]=29;
	else
		mona[1]=28;

	while (idoy-mona[imon]>0) {
		idoy-=mona[imon];
		imon++;
	}

	*day=idoy;
	*month=imon+1;
}