// WSGDATE.C   -  time conversion utility file
 
#include <math.h>
#include <dos.h>
#include "wsgdate.h"


static int ndays[13] = {0,0,31,59,90,120,151,181,212,243,273,304,334};

double etoh(int year,int mnth, int day, int hh,int mm, float ss)
	{
	long doy,dyears;
	long n4,n100,n400,nlpyrs;
	double tdays;
	double dres;

	/* if given month and day, convert to day of year */
	doy = ndays[mnth] + day;
	if(isleap(year) && (mnth > 2)) ++doy;

	dyears = year - 1970;
	n4 = (dyears+1)/4;
	n100 = (dyears+69)/100;
	n400 = (dyears+369)/400;

	nlpyrs = n4 - n100 + n400;
	tdays = (dyears * (double)365) + nlpyrs;

	dres=(double)	24.*60.*60.*(tdays+doy-1)+(double)60.*60.*hh+60.*mm+ss;
	return dres;
	}
int isleap(int year)
	{
	if (year%400 == 0) return(1);
	if (year%4 != 0) return(0);
	if (year%100 == 0) return(0);
	else return(1);
	}
int mdays[13] = {0,31,28,31,30,31,30,31,31,30,31,30,31};

int dom(int dofy,int *mon,int *day,int year)
	{
	if (dofy < 1) {
		*mon = 0;
		*day = 0;
		return(0);
	}

	if (isleap(year)) mdays[2] = 29;
	else mdays[2] = 28;

	for (*mon = 1; *mon <= 12; (*mon)++) {
		*day = dofy;
		if ((dofy -= mdays[*mon]) <= 0) return(1);
	}

	*mon = 0;
	*day = 0;
	return(0);
}

static double di400y=146097.;	/* days in 400 years */
static double di100y=36524.;	/* days in 100 years */
static double di4y=1461.;	/* days in 4 years */

int htoe(double ttt,int *yr,int *mnth, int *day, int *hh,int *mm, float *ss)
	{
	double tot,days,secs,hours,mins,n400yp,n100yp,n4yp,n1yp,i,secs70;
	int month,dim;
	double year,tfract;

	secs70=31536000.*1492.+31622400.*477.;	/* number of seconds from year 1 to Jan 1., 1970 */
	ttt+=secs70;
	tfract=modf(ttt,&tot);

	modf(tot/86400.,&days);
	secs=tot-days*86400.;
	modf(secs/3600.,&hours);
	secs-=hours*3600.;
	modf(secs/60.,&mins);
	secs-=mins*60.;
	*ss=(float)secs+(float)tfract;
	*mm=(int)mins;
	*hh=(int)hours;

	modf(days/di400y,&n400yp);			/* find number of 400 year periods */
	days-=di400y*n400yp;				/* days < 400 years */
	if (days == 146096.) n100yp=3;	/* last year in a 400 year period */
	else modf(days/di100y,&n100yp);
	days-=di100y*n100yp;					/* days < 100 years */
	modf(days/di4y,&n4yp);				/* find number of 4 year periods */
	days-=di4y*n4yp;						/* days < 4 years */
	modf(days/365.,&n1yp);				/* find number of 1 year periods */
	if (n1yp == 4) n1yp=3;
	days-=365.*n1yp;						/* days < 1 year */
	year=400.*n400yp+100.*n100yp+4.*n4yp+n1yp+1.;	/* compute year */
	days+=1.;
	i=dom((int)days,&month,&dim,(int)year);	/* days = day < 1 year ; mon = month 1-12, returned */
/* dim = days in month 1-31, returned ; year = the year, passed only to test for leap year */
	if (i <= 0) {
		return(0);
	}
	*yr=(int)year;							/* year */
	*day=(int)days;						/* day of year */
	*mnth=month;							/* month */
	*day=dim;								/* day of month */
	return(1);
	}
long jdate(int year, int month, int day)
	{
	int doy = ndays[month] + day;
	if(isleap(year) && (month > 2)) ++doy;
   	return 1000L*(long)year+(long)doy;
	}