/*
 * Copyright (C) 1996-8 Michael R. Elkins <me@cs.hmc.edu>
 * 
 *     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 of the License, 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.
 * 
 *     You should have received a copy of the GNU General Public License
 *     along with this program; if not, write to the Free Software
 *     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */ 

/* Slightly modified version from Mutt 0.94.4i */

#include <ctype.h>
#include <string.h>
#include <time.h>
#include <stdio.h>

#define ISSPACE(c) isspace((unsigned char)c)
#define SKIPWS(c) while (*(c) && isspace ((unsigned char) *(c))) c++;

const char *Weekdays[] = { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" };
const char *Months[] = { "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug",
   "Sep", "Oct", "Nov", "Dec", "ERR" };

static const char *next_word (const char *s)
{
  while (*s && !ISSPACE (*s))
    s++;
  SKIPWS (s);
  return s;
}

int check_month (const char *s)
{
  int i;

  for (i = 0; i < 12; i++)
    if (strncasecmp (s, Months[i], 3) == 0)
      return (i);
  return (-1); /* error */
}

static int is_day_name (const char *s)
{
  int i;

  if (!ISSPACE (*(s+3)))
    return 0;
  for (i=0; i<7; i++)
    if (strncasecmp (s, Weekdays[i], 3) == 0)
      return 1;
  return 0;
}

/*
 * A valid message separator looks like:
 *
 * From [ <return-path> ] <weekday> <month> <day> <time> [ <timezone> ] <year>
 */

int is_from (const char *s, char *path, size_t pathlen)
{
  struct tm tm;
  int yr;

  if (path)
    *path = 0;

  if (strncmp ("From ", s, 5) != 0)
    return 0;

  s = next_word (s); /* skip over the From part. */
  if (!*s)
    return 0;

  if (!is_day_name (s))
  {
    const char *p;
    size_t len;

    /* looks like we got the return-path, so extract it  */
    if (*s == '"')
    {
      /* sometimes we see bogus addresses like
       *	From "/foo/bar baz/"@dumbdar.com Sat Nov 22 15:29:32 PST 1997
       */
      p = s;
      p++; /* skip over the quote */
      do
      {
	if (!(p = strpbrk (p, "\\\"")))
	  return 0;
	if (*p == '\\')
	  p += 2;
      }
      while (*p != '"');
      while (*p && !ISSPACE (*p))
	p++;
    }
    else
    {
      if ((p = strchr (s, ' ')) == NULL)
	return 0;
    }
    if (path)
    {
      len = (size_t) (p - s);
      if (len + 1 > pathlen)
	len = pathlen - 1;
      memcpy (path, s, len);
      path[len] = 0;
    }

    s = p + 1;
    SKIPWS (s);
    if (!*s)
      return 0;

    if (!is_day_name (s))
    {
      return 0;
    }
  }

  s = next_word (s);
  if (!*s) return 0;

  /* do a quick check to make sure that this isn't really the day of the week.
   * this could happen when receiving mail from a local user whose login name
   * is the same as a three-letter abbreviation of the day of the week.
   */
  if (is_day_name (s))
  {
    s = next_word (s);
    if (!*s) return 0;
  }

  /* now we should be on the month. */
  if ((tm.tm_mon = check_month (s)) < 0) return 0;

  /* day */
  s = next_word (s);
  if (!*s) return 0;
  if (sscanf (s, "%d", &tm.tm_mday) != 1) return 0;

  /* time */
  s = next_word (s);
  if (!*s) return 0;

  /* Accept either HH:MM or HH:MM:SS */
  if (sscanf (s, "%d:%d:%d", &tm.tm_hour, &tm.tm_min, &tm.tm_sec) == 3);
  else if (sscanf (s, "%d:%d", &tm.tm_hour, &tm.tm_min) == 2)
    tm.tm_sec = 0;
  else
    return 0;

  s = next_word (s);
  if (!*s) return 0;

  /* timezone? */
  if (isalpha ((unsigned char) *s) || *s == '+' || *s == '-')
  {
    s = next_word (s);
    if (!*s) return 0;

    /*
     * some places have two timezone fields after the time, e.g.
     *      From xxxx@yyyyyyy.fr Wed Aug  2 00:39:12 MET DST 1995
     */
    if (isalpha ((unsigned char) *s))
    {
      s = next_word (s);
      if (!*s) return 0;
    }
  }

  /* year */
  if (sscanf (s, "%d", &yr) != 1) return 0;
  tm.tm_year = yr > 1900 ? yr - 1900 : yr;

  tm.tm_isdst = 0;
  tm.tm_yday = 0;
  tm.tm_wday = 0;

/*  return (mutt_mktime (&tm, 0)); */
  return 1;
}