/*
 * strftime - convert a structure to a string, controlled by an argument
 */
/* $Id$ */

#include <time.h>
#include "loc_time.h"

/* The width can be -1 in both s_prnt() as in u_prnt(). This
 * indicates that as many characters as needed should be printed.
 */
static char*
s_prnt(char* s, size_t maxsize, const char* str, int width)
{
	while (width > 0 || (width < 0 && *str))
	{
		if (!maxsize)
			break;
		*s++ = *str++;
		maxsize--;
		width--;
	}
	return s;
}

static char*
u_prnt(char* s, size_t maxsize, unsigned val, int width)
{
	int c;

	c = val % 10;
	val = val / 10;
	if (--width > 0 || (width < 0 && val != 0))
		s = u_prnt(s, (maxsize ? maxsize - 1 : 0), val, width);
	if (maxsize)
		*s++ = c + '0';
	return s;
}

size_t
strftime(char* s, size_t maxsize,
    const char* format, const struct tm* timeptr)
{
	size_t n;
	char *firsts, *olds;

	if (!format)
		return 0;

	_tzset(); /* for %Z conversion */
	firsts = s;
	while (maxsize && *format)
	{
		while (maxsize && *format && *format != '%')
		{
			*s++ = *format++;
			maxsize--;
		}
		if (!maxsize || !*format)
			break;
		format++;

		olds = s;
		switch (*format++)
		{
			case 'a':
				s = s_prnt(s, maxsize,
				    _days[timeptr->tm_wday], ABB_LEN);
				maxsize -= s - olds;
				break;
			case 'A':
				s = s_prnt(s, maxsize, _days[timeptr->tm_wday], -1);
				maxsize -= s - olds;
				break;
			case 'b':
				s = s_prnt(s, maxsize,
				    _months[timeptr->tm_mon], ABB_LEN);
				maxsize -= s - olds;
				break;
			case 'B':
				s = s_prnt(s, maxsize, _months[timeptr->tm_mon], -1);
				maxsize -= s - olds;
				break;
			case 'c':
				n = strftime(s, maxsize,
				    "%a %b %d %H:%M:%S %Y", timeptr);
				if (n)
					maxsize -= n;
				else
					maxsize = 0;
				s += n;
				break;
			case 'd':
				s = u_prnt(s, maxsize, timeptr->tm_mday, 2);
				maxsize -= s - olds;
				break;
			case 'H':
				s = u_prnt(s, maxsize, timeptr->tm_hour, 2);
				maxsize -= s - olds;
				break;
			case 'I':
				s = u_prnt(s, maxsize,
				    (timeptr->tm_hour + 11) % 12 + 1, 2);
				maxsize -= s - olds;
				break;
			case 'j':
				s = u_prnt(s, maxsize, timeptr->tm_yday + 1, 3);
				maxsize -= s - olds;
				break;
			case 'm':
				s = u_prnt(s, maxsize, timeptr->tm_mon + 1, 2);
				maxsize -= s - olds;
				break;
			case 'M':
				s = u_prnt(s, maxsize, timeptr->tm_min, 2);
				maxsize -= s - olds;
				break;
			case 'p':
				s = s_prnt(s, maxsize,
				    (timeptr->tm_hour < 12) ? "AM" : "PM", 2);
				maxsize -= s - olds;
				break;
			case 'S':
				s = u_prnt(s, maxsize, timeptr->tm_sec, 2);
				maxsize -= s - olds;
				break;
			case 'U':
				s = u_prnt(s, maxsize, /* ??? */
				    (timeptr->tm_yday + 7 - timeptr->tm_wday) / 7, 2);
				maxsize -= s - olds;
				break;
			case 'w':
				s = u_prnt(s, maxsize, timeptr->tm_wday, 1);
				maxsize -= s - olds;
				break;
			case 'W':
				s = u_prnt(s, maxsize, /* ??? */
				    (timeptr->tm_yday + 7 - (timeptr->tm_wday + 6) % 7) / 7, 2);
				maxsize -= s - olds;
				break;
			case 'x':
				n = strftime(s, maxsize, "%a %b %d %Y", timeptr);
				if (n)
					maxsize -= n;
				else
					maxsize = 0;
				s += n;
				break;
			case 'X':
				n = strftime(s, maxsize, "%H:%M:%S", timeptr);
				if (n)
					maxsize -= n;
				else
					maxsize = 0;
				s += n;
				break;
			case 'y':
				s = u_prnt(s, maxsize, timeptr->tm_year % 100, 2);
				maxsize -= s - olds;
				break;
			case 'Y':
				s = u_prnt(s, maxsize, timeptr->tm_year + YEAR0, -1);
				maxsize -= s - olds;
				break;
			case 'Z':
				s = s_prnt(s, maxsize,
				    _tzname[(timeptr->tm_isdst > 0)], -1);
				maxsize -= s - olds;
				break;
			case '%':
				*s++ = '%';
				maxsize--;
				break;
			default:
				/* A conversion error. Leave the loop. */
				while (*format)
					format++;
				break;
		}
	}
	if (maxsize)
	{
		*s = '\0';
		return s - firsts;
	}
	return 0; /* The buffer is full */
}