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

char *format_t(char *, Tm);
ulong now;

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

char *dayname[]=
{
	"Sunday", "Monday", "Tuesday", "Wednesday",
	"Thursday", "Friday", "Saturday",
};

void
usage(void)
{
	fprint(2, "usage: %s [-t seconds] format\n", argv0);
	exits("usage");
}

void
main(int argc, char *argv[])
{
	Tm *now_tm;

	now = time(0);

	ARGBEGIN{
	case 't':
		now = strtoul(EARGF(usage()), 0, 0);
		break;
	default:
		usage();
	}ARGEND

	if(! argc == 1) {
		usage();
	}

	now_tm = localtime(now);

	print("%s", format_t(argv[0], *now_tm));

	exits(0);
}

char *
format_t(char *format, Tm t)
{
	char *outb;
	int i, n;
	Rune r;

	outb="";

	for(i = 0; i < strlen(format); i++){
		if(format[i] != '%') {
			n=chartorune(&r, &format[i]);
			i=i+(n-1);
			outb=smprint("%s%C", outb, r);
		}
		else switch(format[++i]){
/*
 *	There's a lot of these. I've done most of POSIX except
 *	locales (EO) and the year-by-weeks stuff (gGUVW), plus.
 *	here:	aAbBcCdDe F  hHIjklmMn prRsStTu v w xXyYzZ%+ ,.
 *	C89:		aAbBc d       HIj  mM  p   S   U  wWxXyY Z%
 *	C04:		aAbBcCdDeEFgGhHIj  mM OprR S TuU VwWxXyYzZ%
 *	OS X:	aAbBcCdDeEFgGhHIjklmMnOprRsStTuUvVwWxXyYzZ%+
 *	Intentionally "stuck" in "C locale".
 */
			case 'a':
				outb=smprint("%s%.3s", outb, format_t("%A", t));
				break;
			case 'A':
				outb=smprint("%s%s", outb, dayname[t.wday]);
				break;
			case 'b':
				outb=smprint("%s%.3s", outb, format_t("%B", t));
				break;
			case 'B':
				outb=smprint("%s%s", outb, month[t.mon]);
				break;
			case 'c':
				outb=smprint("%s%s", outb, format_t("%a %b %e %T %Y", t));
				break;
			case 'C':
				outb=smprint("%s%.2d", outb, (t.year+1900)/100);
				break;
			case 'd':
				outb=smprint("%s%.2d", outb, t.mday);
				break;
			case 'D':
				outb=smprint("%s%s", outb, format_t("%m/%d/%y", t));
				break;
			case 'e':
				outb=smprint("%s%2.d", outb, t.mday);
				break;
			case 'F':
				outb=smprint("%s%s", outb, format_t("%Y-%m-%d", t));
				break;
			case 'h':
				outb=smprint("%s%s", outb, format_t("%b", t));
				break;
			case 'H':
				outb=smprint("%s%.2d", outb, t.hour);
				break;
			case 'I':
				outb=smprint("%s%.2d", outb, t.hour%12);
				break;
			case 'j':
				outb=smprint("%s%d", outb, t.yday);
				break;
			case 'k':
				outb=smprint("%s%2.d", outb, t.hour);
				break;
			case 'l':
				outb=smprint("%s%2.d", outb, t.hour%12);
				break;
			case 'm':
				outb=smprint("%s%.2d", outb, t.mon+1);
				break;
			case 'M':
				outb=smprint("%s%.2d", outb, t.min);
				break;
			case 'p':
				if(t.hour < 12)
					outb=smprint("%s%s", outb, "AM");
				else
					outb=smprint("%s%s", outb, "PM");
				break;
			case 'r':
				outb=smprint("%s%s", outb, format_t("%I:%M:%S %p", t));
				break;
			case 'R':
				outb=smprint("%s%s", outb, format_t("%H:%M", t));
				break;
			case 's':
				outb=smprint("%s%ld", outb, now);
				break;
			case 'S':
				outb=smprint("%s%.2d", outb, t.sec);
				break;
			case 'T':
				outb=smprint("%s%s", outb, format_t("%H:%M:%S", t));
				break;
			case 'u':
				if(t.wday==0)
					outb=smprint("%s%d", outb, 7);
				else
					outb=smprint("%s%d", outb, t.wday);
				break;
			case 'v':
				outb=smprint("%s%s", outb, format_t("%e-%b-%Y", t));
				break;
			case 'x':
				outb=smprint("%s%s", outb, format_t("%m/%d/%y", t));
				break;
			case 'X':
				outb=smprint("%s%s", outb, format_t("%T", t));
				break;
			case 'y':
				outb=smprint("%s%.2d", outb, t.year%100);
				break;
			case 'Y':
				outb=smprint("%s%.4d", outb, t.year+1900);
				break;
			case 'w':
				outb=smprint("%s%d", outb, t.wday);
				break;
			case 'z':
				outb=smprint("%s%+.2d:%u.2d", outb, t.tzoff/(60*60),
					(t.tzoff%(60*60))/60);
				break;
			case 'Z':
				outb=smprint("%s%s", outb, t.zone);
				break;
			case '+':
				outb=smprint("%s%s", outb, ctime(now));
				break;

			/* Made-up additions */
			case ',':	/* Truncated Julian Day (TJD) */
				outb=smprint("%s%d", outb,
					(int)(2440587.5 + (now/(60*60*24)) - 2440000.5));
				break;
			case '.':	/* TJD w/ fractional days */
				outb=smprint("%s%f", outb,
					(2440587.5 + (now/(60*60*24.0)) - 2440000.5));
				break;

			/* Literals and others */
			case ' ':
				outb=smprint("%s%s", outb, "% ");
				break;
			case '%':
				outb=smprint("%s%s", outb, "%");
				break;
			case 'n':
				outb=smprint("%s%s", outb, "\n");
				break;
			case 't':
				outb=smprint("%s%s", outb, "	");
				break;
			default:
				break;
			}
	}
	return outb;
}