/*----------------------------------------------------------------------*\
 | Utility routines to convert FIPS dates to and from struct tm			|
 |																		|
 | Routines that write date as string to address given by argument:		|
 | tm_to_yd		from struct tm, generate FIPS date in YYDDD form		|
 | tm_to_yyd	from struct tm, generate FIPS date in YYYYDDD form		|
 | tm_to_ymd	from struct tm, generate FIPS date in YYMMDD form		|
 | tm_to_yymd	from struct tm, generate FIPS date in YYYYMMDD form		|
 |																		|
 | Routines that dynamically allocate struct tm and return its address:	|
 | ymd_to_tm	from FIPS date as YYMMDD or YYYYMMDD, make struct tm	|
 | yd_to_tm		from FIPS date as YYDDD or YYYYDDD, make struct tm		|
 | get_tm		from FIPS date and time (HHMM), make struct tm			|
 |																		|
 | Routines that modify the time data passed by reference				|
 | next_day		modify struct tm by adding one day						|
 | increment_yd	modify FIPS date in YYDDD form by adding one day		|
 |																		|
 | Peter N. Schweitzer (U.S. Geological Survey, Reston, VA 22092)		|
\*----------------------------------------------------------------------*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#include "dw.h"

static char msg [128];

/*                        Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec */
static int year_days[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
static int leap_days[] = { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

static char *month_name[] = {
	"January","February","March","April","May","June","July","August",
	"September","October","November","December"
	};

size_t tm_to_yd (char *dst, const struct tm *tm) {
	return (strftime (dst,6,"%y%j",tm));
	}

size_t tm_to_yyd (char *dst,const struct tm *tm) {
	return (strftime (dst,8,"%Y%j",tm));
	}

size_t tm_to_ymd (char *dst, const struct tm *tm) {
	return (strftime (dst,7,"%y%m%d",tm));
	}

size_t tm_to_yymd (char *dst, const struct tm *tm) {
	return (strftime (dst,9,"%Y%m%d",tm));
	}

struct tm *ymd_to_tm (const char *ymd) {
	int y,m,d;
	const char *s;
	struct tm *tm;
	int *day_count;

	for (s=ymd; *s; s++)
		if (!isdigit (*s)) return (NULL);

	s = ymd;
	if (strlen (ymd) == 8) {
		y = *s++ - '0';
		y *= 10;
		y += *s++ - '0';
		if (y < 19) {
			sprintf (msg,"Error: year must be later than 1899 in \"%s\"",ymd);
			dw_error (msg);
			return (NULL);
			}
		y -= 19;
		}
	else
		y = 0;
	y *= 10;
	y += *s++ - '0';
	y *= 10;
	y += *s++ - '0';

	m  = *s++ - '0';
	m *= 10;
	m += *s++ - '0';
	m--;

	if (m > 11) {
		sprintf (msg,"Error: invalid month %d in \"%s\"",m,ymd);
		dw_error (msg);
		return (NULL);
		}

	d  = *s++ - '0';
	d *= 10;
	d += *s++ - '0';

	if (y & 3) day_count = year_days;
	else       day_count = leap_days;
	if (d > day_count [m]) {
		sprintf (msg,"Error: %s of %d has only %d days, not %d",month_name[m],1900+y,day_count[m],d);
		dw_error (msg);
		return (NULL);
		}

	if (tm = (struct tm *) malloc (sizeof(struct tm))) {
		tm->tm_sec = 0;
		tm->tm_min = 0;
		tm->tm_hour = 0;
		tm->tm_mday = d;
		tm->tm_mon = m;
		tm->tm_year = y;
		tm->tm_wday = 0;
		tm->tm_yday = 0;
		tm->tm_isdst = -1;
		if (mktime (tm) == (time_t) -1) {
			free (tm);
			tm = NULL;
			}
		}
	return (tm);
	}

struct tm *yd_to_tm (const char *yd) {
	int y,m,d;
	const char *s;
	struct tm *tm;
	int *day_count;

	for (s=yd; *s; s++)
		if (!isdigit (*s)) {
			dw_error ("Error: date must consist entirely of numbers");
			return (NULL);
			}

	s = yd;
	if (strlen (yd) == 7) {
		y = *s++ - '0';
		y *= 10;
		y += *s++ - '0';
		if (y < 19) {
			sprintf (msg,"Error: year must be later than 1899 in \"%s\"",yd);
			dw_error (msg);
			return (NULL);
			}
		y -= 19;
		}
	else
		y = 0;
	y *= 10;
	y += *s++ - '0';
	y *= 10;
	y += *s++ - '0';

	if (y & 3) day_count = year_days;
	else       day_count = leap_days;

	d  = *s++ - '0';
	d *= 10;
	d += *s++ - '0';
	d *= 10;
	d += *s++ - '0';

	m = 0;
	while (d > day_count[m]) d -= day_count[m++];

	if (m > 11) {
		sprintf (msg,"Error: invalid day count in \"%s\"",yd);
		dw_error (msg);
		return (NULL);
		}

	if (tm = (struct tm *) malloc (sizeof(struct tm))) {
		tm->tm_sec = 0;
		tm->tm_min = 0;
		tm->tm_hour = 0;
		tm->tm_mday = d;
		tm->tm_mon = m;
		tm->tm_year = y;
		tm->tm_wday = 0;
		tm->tm_yday = 0;
		tm->tm_isdst = -1;
		if (mktime (tm) == (time_t) -1) {
			free (tm);
			tm = NULL;
			}
		}
	return (tm);
	}

struct tm *get_tm (char *ds, char *ts) {
	int j,h,m;
	char *s;
	struct tm *tm = NULL;

	j = strlen (ds);
	if (j == 7 || j == 5) tm = yd_to_tm (ds);
	else
		if (j == 8 || j == 6) tm = ymd_to_tm (ds);
		else
			dw_error ("Error: expected date like YYMMDD or YYDDD");
	if (tm) {
		s = ts;
		if (!isdigit(s[0]) || !isdigit(s[1]) || !isdigit(s[2]) || !isdigit(s[3]))
			dw_error ("Error: expected time like HHMM");
		h = *s++ - '0';
		h *= 10;
		h += *s++ - '0';
		m = *s++ - '0';
		m *= 10;
		m += *s++ - '0';
		tm->tm_hour = h;
		tm->tm_min = m;
		}
	return (tm);
	}

void next_day (struct tm *tm) {
	int *day_count;

	if (tm->tm_year & 3) day_count = year_days;
	else day_count = leap_days;

	tm->tm_yday++;
	tm->tm_mday++;
	if (tm->tm_mday > day_count[tm->tm_mon]) {
		tm->tm_mday -= day_count[tm->tm_mon];
		tm->tm_mon++;
		if (tm->tm_mon > 11) {
			tm->tm_mon = 0;
			tm->tm_year++;
			tm->tm_yday = 0;
			}
		}
	}

/*----------------------------------------------------------------------*\
 | increment_yd modifies a FIPS date in the form YYDDD by adding one	|
 | day and, if necessary, adjusting the year accordingly.  Note that it	|
 | modifies the string pointed to by the argument.						|
\*----------------------------------------------------------------------*/

void increment_yd (char *yyddd) {
	int y,d;
	char *s = yyddd;

	y = *s++ - '0';
	y *= 10;
	y += *s++ - '0';

	d = *s++ - '0';
	d *= 10;
	d += *s++ - '0';
	d *= 10;
	d += *s++ - '0';

	d++;

	if (d > 365)
		if (y & 3) {	/* not a leap year */
			y++;
			s = yyddd;
			*s++ = '0' + (y / 10);
			*s++ = '0' + (y % 10);
			d -= 365;
			}
		else	/* leap year */
			if (d > 366) {
				y++;
				s = yyddd;
				*s++ = '0' + (y / 10);
				*s++ = '0' + (y % 10);
				d -= 366;
				}

	s = yyddd + 2;
	*s++ = '0' + d/100;
	*s++ = '0' + (d % 100)/10;
	*s = '0' + (d % 10);
	}

/*----------------------------------------------------------------------*\
\*----------------------------------------------------------------------*/