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

typedef char *(Stamper)(vlong);
typedef vlong (Parser)(char **);

typedef struct Unit {
	char	*name;
	Stamper	*stamp;
	Parser	*parse;
} Unit;

Stamper isostamp, ascstamp, nsstamp, μsstamp, msstamp, sstamp;
Parser parsens, parseμs, parsems, parses;

Unit utab[] = {
	{"iso",	isostamp},
	{"asc",	ascstamp},
	{"ns",	nsstamp,	parsens},
	{"μs",	μsstamp,	parseμs},
	{"ms",	msstamp,	parsems},
	{"s",	sstamp,	parses},
};

Unit *
ulookup(char *s)
{
	int i;

	for(i=0; i < nelem(utab); i++) {
		if(strcmp(s, utab[i].name) == 0)
			return utab+i;
	}
	return nil;
}

char *
skipspace(char *s)
{
	return s + strspn(s, " 	");
}

char *
isostamp(vlong ns)
{
	char *p;

	p = isotime(localtime(ns / (int)1e9));
	p[26] = '\0';
	return p;
}

char *
ascstamp(vlong ns)
{
	char *p;

	p = asctime(localtime(ns / (int)1e9));
	p[28] = '\0';
	return p;
}

char *
nsstamp(vlong ns)
{
	static char p[32];

	sprint(p, "%lld", ns);
	return p;
}

vlong
parsens(char **s)
{
	vlong ns;

	ns = strtoll(*s, s, 0);
	*s = skipspace(*s);
	return ns;
}

char *
μsstamp(vlong ns)
{
	static char p[32];

	sprint(p, "%lld", ns / (int)1e3);
	return p;
}

vlong
parseμs(char **s)
{
	vlong ns;

	ns = strtoll(*s, s, 0) * (int)1e3;
	*s = skipspace(*s);
	return ns;
}

char *
msstamp(vlong ns)
{
	static char p[32];

	sprint(p, "%lld", ns / (int)1e6);
	return p;
}

vlong
parsems(char **s)
{
	vlong ns;

	ns = strtoll(*s, s, 0) * (int)1e6;
	*s = skipspace(*s);
	return ns;
}

char *
sstamp(vlong ns)
{
	static char p[32];

	sprint(p, "%lld", ns / (int)1e9);
	return p;
}

vlong
parses(char **s)
{
	vlong ns;

	ns = strtoll(*s, s, 0) * (int)1e9;
	*s = skipspace(*s);
	return ns;
}

vlong
parsenull(char **)
{
	return nsec();
}

void
usage(void)
{
	fprint(2, "usage: %s [-c fromunit] unit [file]\n", argv0);
	exits("usage");
}

void
main(int argc, char **argv)
{
	Unit *fromunit, *tounit;
	Stamper *stamp;
	Parser *parse;
	int fd;
	Biobuf bin;
	char *line;

	fromunit = nil;
	ARGBEGIN {
	case 'c': {
			char *s = EARGF(usage());
			if((fromunit = ulookup(s)) == nil)
				sysfatal("invalid unit: %s", s);
		}
		break;
	default:
		usage();
	} ARGEND

	if(argc < 1)
		usage();
	if((tounit = ulookup(*argv)) == nil)
		sysfatal("invalid unit: %s", *argv);
	argc--; argv++;

	if((stamp = tounit->stamp) == nil)
		sysfatal("can't output %s", tounit->name);
	if(fromunit == nil)
		parse = parsenull;
	else if((parse = fromunit->parse) == nil)
		sysfatal("can't parse %s", fromunit->name);

	switch(argc) {
	case 0:
		fd = 0;
		break;
	case 1:
		if((fd = open(argv[0], OREAD)) < 0)
			sysfatal("open %s: %r", argv[0]);
		break;
	default:
		usage();
		SET(fd);
	}
	Binit(&bin, fd, OREAD);

	while((line = Brdline(&bin, '\n')) != nil) {
		line[Blinelen(&bin) - 1] = '\0';
		if(print("%s	%s\n", stamp(parse(&line)), line) < 0)
			sysfatal("print: %r");
	}
	exits(nil);
}