#include <u.h>
#include <libc.h>

static char*
skiptext(char *q)
{
	while(*q != '\0' && *q != ' ' && *q != '\t' && *q != '\r' && *q != '\n')
		q++;
	return q;
}

static char*
skipwhite(char *q)
{
	while(*q == ' ' || *q == '\t' || *q == '\r' || *q == '\n')
		q++;
	return q;
}

static char* months[] = {
	"jan", "feb", "mar", "apr",
	"may", "jun", "jul", "aug",
	"sep", "oct", "nov", "dec"
};

int
strtotm(char *p, Tm *t)
{
	char *q, *r;
	int j;
	Tm tm;
	int delta;

	delta = 0;
	memset(&tm, 0, sizeof(tm));
	tm.mon = -1;
	tm.hour = -1;
	tm.min = -1;
	tm.year = -1;
	tm.mday = -1;
	for(p = skipwhite(p); *p; p = skipwhite(q)){
		q = skiptext(p);

		/* look for time in hh:mm[:ss] */
		if(r = memchr(p, ':', q - p)){
			tm.hour = strtol(p, 0, 10);
			tm.min = strtol(r + 1, 0, 10);
			if(r = memchr(r + 1, ':', q - (r + 1)))
				tm.sec = strtol(r + 1, 0, 10);
			else
				tm.sec = 0;
			continue;
		}

		/* look for month */
		for(j = 0; j < 12; j++)
			if(cistrncmp(p, months[j], 3) == 0){
				tm.mon = j;
				break;
			}
		if(j != 12)
			continue;

		/* look for time zone [A-Z][A-Z]T */
		if(q - p == 3)
		if(p[0] >= 'A' && p[0] <= 'Z')
		if(p[1] >= 'A' && p[1] <= 'Z')
		if(p[2] == 'T'){
			strecpy(tm.zone, tm.zone + 4, p);
			continue;
		}

		if(p[0] == '+'||p[0] == '-')
		if(q - p == 5 && strspn(p + 1, "0123456789") == 4){
			delta = (((p[1] - '0')*10 + p[2] - '0')*60 + (p[3] - '0')*10 + p[4] - '0')*60;
			if(p[0] == '-')
				delta = -delta;
			continue;
		}
		if(strspn(p, "0123456789") == q - p){
			j = strtol(p, nil, 10);
			if(j >= 1 && j <= 31)
				tm.mday = j;
			if(j >= 1900)
				tm.year = j - 1900;
			continue;
		}
		//eprint("strtotm: garbage %.*s\n", q - p, p);
	}
	if(tm.mon < 0 || tm.year < 0
	|| tm.hour < 0 || tm.min < 0
	|| tm.mday < 0)
		return -1;

	*t = *localtime(tm2sec(&tm) - delta);
	return 0;
}