/* 
 *  Author: Chris Lord <chris@openedhand.com>
 *
 *  Copyright (c) 2007 OpenedHand Ltd - http://www.openedhand.com/
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2, or (at your option)
 *  any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 */

/**
 * SECTION:jana-ecal-utils
 * @short_description: A set of utility functions for libjana-ecal
 *
 * jana-ecal-utils contains a set of libjana-ecal related utility functions.
 */

#include <string.h>
#include <libical/icaltime.h>
#include <libjana/jana-utils.h>
#include <libecal/e-cal-time-util.h>
#include <libjana-ecal/jana-ecal-time.h>
#include "jana-ecal-utils.h"

/**
 * jana_ecal_utils_time_now:
 * @location: A full timezone name
 *
 * Creates a new #JanaEcalTime with the current time of the given location.
 *
 * Returns: A new #JanaEcalTime, cast as a #JanaTime.
 */
JanaTime *
jana_ecal_utils_time_now (const gchar *location)
{
	icaltimetype ical_time;
	const icaltimezone *zone;
	
	zone = (const icaltimezone *)icaltimezone_get_builtin_timezone (
		location);
	ical_time = icaltime_current_time_with_zone (zone);
	icaltime_set_timezone (&ical_time, zone);

	return jana_ecal_time_new_from_icaltime (&ical_time);
}

/**
 * jana_ecal_utils_time_today:
 * @location: A full timezone name
 *
 * Creates a new #JanaEcalTime with the current date of the given location.
 *
 * Returns: A new #JanaEcalTime, cast as a #JanaTime.
 */
JanaTime *
jana_ecal_utils_time_today (const gchar *location)
{
	JanaTime *time;
	icaltimetype ical_time;
	const icaltimezone *zone;
	
	zone = (const icaltimezone *)icaltimezone_get_builtin_timezone (
		location);
	ical_time = icaltime_current_time_with_zone (zone);
	icaltime_set_timezone (&ical_time, zone);

	time = jana_ecal_time_new_from_icaltime (&ical_time);
	jana_time_set_isdate (time, TRUE);

	return time;
}

/**
 * jana_ecal_utils_guess_location:
 *
 * Tries to guess the location by checking for common system files and 
 * finally falling back on the first location that matches the current 
 * system timezone.
 *
 * Returns: A newly allocated string with the guessed location.
 */
gchar *
jana_ecal_utils_guess_location ()
{
	gint i;
	FILE *file;
	gchar *tzname;
	gchar string[128];
	icaltimetype today;
	icalarray *builtin;
	time_t now_t = time (NULL);
	struct tm *now = localtime (&now_t);
	
	/* Debian systems have /etc/timezone */
	if ((file = fopen ("/etc/timezone", "r"))) {
		if ((fgets (string, 128, file)) && (string[0] != '\0')) {
			gint c;
			fclose (file);
			for (c = 0; (string[c] != '\0') &&
			     (string[c] != '\n'); c++);
			string[c] = '\0';
			return g_strdup (string);
		}
		fclose (file);
	}
	
#if GLIB_CHECK_VERSION(2,14,0)
	/* OpenSuSE (and RH?) systems have /etc/sysconfig/clock */
	if ((file = fopen ("/etc/sysconfig/clock", "r"))) {
		GRegex *regex;
		GError *error = NULL;

		regex = g_regex_new ("TIMEZONE *= *\".*\"",
			G_REGEX_OPTIMIZE, 0, &error);
		if (!regex) {
			g_warning ("Failed to create regex: %s",
				error->message);
			g_error_free (error);
		} else while (fgets (string, 128, file)) {
			GMatchInfo *match_info;
			if (g_regex_match (regex, string, 0, &match_info)) {
				gchar *zone;
				gchar *match = g_match_info_fetch (
					match_info, 0);
				
				g_match_info_free (match_info);
				g_regex_unref (regex);
				fclose (file);
				
				if (match[strlen (match) - 2] == '\n')
					match[strlen (match)-2] = '\0';
				else
					match[strlen (match)-1] = '\0';
				zone = g_strdup (strchr (match, '\"') + 1);
				g_free (match);
				
				return zone;
			}
			g_match_info_free (match_info);
		}
		if (regex) g_regex_unref (regex);
		fclose (file);
	}
#endif
	
	/* Fallback to first location that matches libc timezone and the
	 * offset for the current time.
	 */
	today = icaltime_today ();
	tzname = jana_utils_get_local_tzname ();
	builtin = icaltimezone_get_builtin_timezones ();
	for (i = 0; i < builtin->num_elements; i++) {
		icaltimezone *zone = (icaltimezone *)icalarray_element_at (
			builtin, i);
		gchar *zone_tz;
		int offset;
		
		offset = icaltimezone_get_utc_offset (zone, &today, NULL);
		zone_tz = icaltimezone_get_tznames (zone);

		if (zone_tz && (strcasecmp (tzname, zone_tz) == 0) &&
		    (offset == now->tm_gmtoff)) {
			g_free (tzname);
			return g_strdup (icaltimezone_get_display_name (zone));
		}
	}
	g_free (tzname);
	
	/* No matching timezone found, fall back to UTC */
	return g_strdup ("UTC");
}

/**
 * jana_ecal_utils_get_locations:
 *
 * Retrieves the built-in list of timezone locations from libecal.
 *
 * Returns: A newly allocated string array, to be freed with g_strfreev().
 */
gchar **
jana_ecal_utils_get_locations ()
{
	gint i, z;
	icalarray *builtin;
	gchar **locations;
	
	builtin = icaltimezone_get_builtin_timezones ();
	locations = g_new0 (gchar *, builtin->num_elements + 1);
	for (i = 0, z = 0; i < builtin->num_elements; i++) {
		icaltimezone *zone = (icaltimezone *)icalarray_element_at (
			builtin, i);

		/* Don't return zones that don't have a tzname */
		if (icaltimezone_get_tznames (zone)) {
			locations[z] = g_strdup (
				icaltimezone_get_display_name (zone));
			z++;
		}
	}
	
	return locations;
}