/* Copyright (C) 2001 Free Software Foundation, Inc.
   A wrapper for mktime function allowing to specify the timezone.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#if HAVE_CONFIG_H
# include <config.h>
#endif

#include <stdio.h>
#ifdef HAVE_STRINGS_H
#include <strings.h>
#endif
#include <time.h>

#include <mailutils/mutil.h>
/* Convert struct tm into time_t, taking into account timezone offset.
 
 mktime() always treats tm as if it was localtime, so convert it
 to UTC, then adjust by the tm's real timezone, if it is known.
*/
time_t
mu_tm2time (struct tm *timeptr, mu_timezone* tz)
{
  int offset = tz ? tz->utc_offset : 0;
  
  return mktime(timeptr) - mu_utc_offset() + offset;
}

/* Convert time 0 at UTC to our localtime, that tells us the offset
   of our current timezone from UTC. */
time_t mu_utc_offset(void)
{
  time_t t = 0;
  struct tm* tm = gmtime(&t);

  return mktime(tm);
}

static const char *months[] =
{
  "Jan", "Feb", "Mar", "Apr", "May", "Jun",
  "Jul", "Aug", "Sep", "Oct", "Nov", "Dec", NULL
};

static const char *wdays[] =
{
  "Mon", "Teu", "Wed", "Thr", "Fri", "Sat", "Sun", NULL
};

int
mu_parse_imap_date_time (const char **p, struct tm *tm, mu_timezone *tz)
{
  int year, mon, day, hour, min, sec;
  char zone[6] = "+0000";	/* ( "+" / "-" ) hhmm */
  char month[5] = "";
  int hh = 0;
  int mm = 0;
  int sign = 1;
  int scanned = 0, scanned3;
  int i;
  int tzoffset;

  day = mon = year = hour = min = sec = 0;

  memset (tm, 0, sizeof (*tm));

  switch (sscanf (*p,
		  "%2d-%3s-%4d%n %2d:%2d:%2d %5s%n",
		  &day, month, &year, &scanned3, &hour, &min, &sec, zone,
		  &scanned))
    {
    case 3:
      scanned = scanned3;
      break;
    case 7:
      break;
    default:
      return -1;
    }

  tm->tm_sec = sec;
  tm->tm_min = min;
  tm->tm_hour = hour;
  tm->tm_mday = day;

  for (i = 0; i < 12; i++)
    {
      if (strncasecmp (month, months[i], 3) == 0)
	{
	  mon = i;
	  break;
	}
    }
  tm->tm_mon = mon;
  tm->tm_year = (year > 1900) ? year - 1900 : year;
  tm->tm_yday = 0;		/* unknown. */
  tm->tm_wday = 0;		/* unknown. */
#if HAVE_TM_ISDST
  tm->tm_isdst = -1;		/* unknown. */
#endif

  hh = (zone[1] - '0') * 10 + (zone[2] - '0');
  mm = (zone[3] - '0') * 10 + (zone[4] - '0');
  sign = (zone[0] == '-') ? -1 : +1;
  tzoffset = sign * (hh * 60 * 60 + mm * 60);

#if HAVE_TM_GMTOFFSET
  tm->tm_gmtoffset = tzoffset;
#endif

  if (tz)
    {
      tz->utc_offset = tzoffset;
      tz->tz_name = NULL;
    }

  *p += scanned;

  return 0;
}

/* "ctime" format is: Thu Jul 01 15:58:27 1999, with no trailing \n.  */
int
mu_parse_ctime_date_time (const char **p, struct tm *tm, mu_timezone * tz)
{
  int wday = 0;
  int year = 0;
  int mon = 0;
  int day = 0;
  int hour = 0;
  int min = 0;
  int sec = 0;
  int n = 0;
  int i;
  char weekday[5] = "";
  char month[5] = "";

  if (sscanf (*p, "%3s %3s %2d %2d:%2d:%2d %d%n\n",
	weekday, month, &day, &hour, &min, &sec, &year, &n) != 7)
    return -1;

  *p += n;

  for (i = 0; i < 7; i++)
    {
      if (strncasecmp (weekday, wdays[i], 3) == 0)
	{
	  wday = i;
	  break;
	}
    }

  for (i = 0; i < 12; i++)
    {
      if (strncasecmp (month, months[i], 3) == 0)
	{
	  mon = i;
	  break;
	}
    }

  if (tm)
    {
      memset (tm, 0, sizeof (struct tm));

      tm->tm_sec = sec;
      tm->tm_min = min;
      tm->tm_hour = hour;
      tm->tm_mday = day;
      tm->tm_wday = wday;
      tm->tm_mon = mon;
      tm->tm_year = (year > 1900) ? year - 1900 : year;
#ifdef HAVE_TM_ISDST
      tm->tm_isdst = -1;	/* unknown. */
#endif
    }

  /* ctime has no timezone information, set tz to UTC if they ask. */
  if (tz)
    memset (tz, 0, sizeof (struct mu_timezone));

  return 0;
}