/* See LICENSE file for copyright and license details. */
#include "common.h"


static char *
get_timezone(struct libgeome_context *ctx, int *env_determined_out)
{
	const char *tzdir;
	const char *tz;
	char *tzbuf = NULL;
	char *ret;
	size_t tzdirlen;

	tz = getenv("TZ");
	*env_determined_out = !!tz;
	if (!tz) {
		tzdir = getenv("TZDIR");
		if (!tzdir)
			tzdir = TZDIR;
		tz = tzbuf = libgeome_util_areadlink(ctx, TZFILE);
		if (!tz)
			return NULL;
		tzdirlen = strlen(tzdir);
		if (!strncmp(tz, tzdir, tzdirlen) && tz[tzdirlen] == '/') {
			tz = &tz[tzdirlen];
			while (*tz == '/')
				tz++;
		}
	}

	ret = strdup(tz);
	if (!ret)
		ctx->print_error(ctx, "strdup: %s\n", strerror(errno));
	free(tzbuf);
	return ret;
}


static int
get_timezone_location3(struct libgeome_context *ctx, const char *tz, const char *tabfile, struct location *location_out)
{
	const char *tzdir, *coords;
	char *path, *line = NULL, *p;
	size_t size = 0, tzlen = strlen(tz);
	int lat_sign, lat_degrees, lat_minutes, lat_seconds = 0;
	int lon_sign, lon_degrees, lon_minutes, lon_seconds = 0;
	ssize_t len;
	FILE *f;

	tzdir = getenv("TZDIR");
	if (!tzdir)
		tzdir = TZDIR;

	path = malloc(strlen(tzdir) + strlen(tabfile) + sizeof("/"));
	if (!path) {
		ctx->print_error(ctx, "malloc: %s\n", strerror(errno));
		return -1;
	}
	stpcpy(stpcpy(stpcpy(path, tzdir), "/"), tabfile);

	f = fopen(path, "r");
	if (!f) {
		if (errno == ENOENT)
			ctx->print_debug(ctx, "fopen %s r: %s\n", path, strerror(errno));
		else
			ctx->print_error(ctx, "fopen %s r: %s\n", path, strerror(errno));
		free(path);
		return -1;
	}

again:
	while (len = getline(&line, &size, f), len >= 0) {
		p = line;
		for (;; p++) {
			if (!*p || *p == '\r' || *p == '\n' || *p == '#')
				goto next_line;
			if (*p == '\t')
				break;
		}

		coords = ++p;
		for (;; p++) {
			if (!*p || *p == '\r' || *p == '\n' || *p == '#')
				goto next_line;
			if (*p == '\t')
				break;
		}
		*p++ = '\0';

		if (strncmp(p, tz, tzlen))
			goto next_line;
		p = &p[tzlen];
		if (*p && *p != '\r' && *p != '\n' && *p != '#' && *p != '\t')
			goto next_line;

		goto found_coords;

	next_line:;
	}
	if (!feof(f)) {
		if (errno == EINTR) {
			clearerr(f);
			goto again;
		}
		ctx->print_error(ctx, "getline %s: %s\n", path, strerror(errno));
	}
	ctx->print_debug(ctx, "entry for timezone %s not found in %s\n", tz, path);

	free(line);
	free(path);
	fclose(f);
	return -1;

bad_coords:
	ctx->print_debug(ctx, "malformatted coordinates for %s in %s\n", tz, path);
	free(line);
	free(path);
	fclose(f);
	return -1;

found_coords:
	if (coords[0] != '+' && coords[0] != '-')
		goto bad_coords;
	if (!isdigit(coords[1]) || !isdigit(coords[2]))
		goto bad_coords;
	if (!isdigit(coords[3]) || !isdigit(coords[4]))
		goto bad_coords;
	lat_sign = coords[0] == '-' ? -1 : +1;
	lat_degrees = (coords[1] & 15) * 10 + (coords[2] & 15);
	lat_minutes = (coords[3] & 15) * 10 + (coords[4] & 15);
	coords = &coords[5];
	if (isdigit(coords[0]) && isdigit(coords[1])) {
		lat_seconds = (coords[0] & 15) * 10 + (coords[1] & 15);
		coords = &coords[2];
	}

	if (coords[0] != '+' && coords[0] != '-')
		goto bad_coords;
	if (!isdigit(coords[1]) || !isdigit(coords[2]) || !isdigit(coords[3]))
		goto bad_coords;
	if (!isdigit(coords[4]) || !isdigit(coords[5]))
		goto bad_coords;
	lon_sign = coords[0] == '-' ? -1 : +1;
	lon_degrees = (coords[1] & 15) * 100 + (coords[2] & 15) * 10 + (coords[3] & 15);
	lon_minutes = (coords[4] & 15) * 10 + (coords[5] & 15);
	coords = &coords[6];
	if (isdigit(coords[0]) && isdigit(coords[1])) {
		lon_seconds = (coords[0] & 15) * 10 + (coords[1] & 15);
		coords = &coords[2];
	}

	if (*coords)
		goto bad_coords;

	if (lat_degrees > 90 || lon_degrees > 180)
		goto bad_coords;
	if (lat_minutes >= 60 || lon_minutes >= 60)
		goto bad_coords;
	if (lat_seconds >= 60 || lon_seconds >= 60)
		goto bad_coords;
	if (lat_degrees == 90 && lat_minutes + lat_seconds)
		goto bad_coords;
	if (lon_degrees == 180 && lon_minutes + lon_seconds)
		goto bad_coords;

	location_out->latitude = (double)lat_degrees;
	location_out->latitude += (double)lat_minutes / 60;
	location_out->latitude += (double)lat_seconds / 3600;
	location_out->latitude *= (double)lat_sign;

	location_out->longitude = (double)lon_degrees;
	location_out->longitude += (double)lon_minutes / 60;
	location_out->longitude += (double)lon_seconds / 3600;
	location_out->longitude *= (double)lon_sign;

	free(line);
	free(path);
	fclose(f);
	return 0;
}


static int
get_timezone_location(struct libgeome_context *ctx, const char *tz, struct location *location_out)
{
	if (!get_timezone_location3(ctx, tz, "zone1970.tab", location_out))
		return 0;
	if (!get_timezone_location3(ctx, tz, "zone.tab", location_out))
		return 0;
	if (!get_timezone_location3(ctx, tz, "zonenow.tab", location_out))
		return 0;
	return -1;
}


int
libgeome_get_from_timezone(struct libgeome_context *ctx, struct libgeome_data *out)
{
	struct location location;
	char *tz;

	tz = get_timezone(ctx, &(int){0});
	if (!tz)
		return -1;
	if (get_timezone_location(ctx, tz, &location)) {
		free(tz);
		return -1;
	}
	free(tz);

	out->requested_data &= LIBGEOME_DATUM_LATITUDE | LIBGEOME_DATUM_LONGITUDE;
	if (out->requested_data) {
		if (out->requested_data & LIBGEOME_DATUM_LATITUDE)
			out->latitude = location.latitude;
		if (out->requested_data & LIBGEOME_DATUM_LONGITUDE)
			out->longitude = location.longitude;
	}

	return 0;

}