/* Parse dates for touch and date.

   Copyright (C) 1989-1991, 1998, 2000-2010 Free Software Foundation, Inc.

   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 3 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, see <http://www.gnu.org/licenses/>.  */

/* Yacc-based version written by Jim Kingdon and David MacKenzie.
   Rewritten by Jim Meyering.  */

#include <config.h>

#include "posixtm.h"

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <string.h>

#if USE_UNLOCKED_IO
# include "unlocked-io.h"
#endif

/* ISDIGIT differs from isdigit, as follows:
   - Its arg may be any int or unsigned int; it need not be an unsigned char
     or EOF.
   - It's typically faster.
   POSIX says that only '0' through '9' are digits.  Prefer ISDIGIT to
   isdigit unless it's important to use the locale's definition
   of `digit' even when the host does not conform to POSIX.  */
#define ISDIGIT(c) ((unsigned int) (c) - '0' <= 9)

/*
  POSIX requires:

  touch -t [[CC]YY]mmddhhmm[.ss] FILE...
    8, 10, or 12 digits, followed by optional .ss
    (PDS_LEADING_YEAR | PDS_CENTURY | PDS_SECONDS)

  touch mmddhhmm[YY] FILE... (obsoleted by POSIX 1003.1-2001)
    8 or 10 digits, YY (if present) must be in the range 69-99
    (PDS_TRAILING_YEAR | PDS_PRE_2000)

  date mmddhhmm[[CC]YY]
    8, 10, or 12 digits
    (PDS_TRAILING_YEAR | PDS_CENTURY)

*/

static int
year (struct tm *tm, const int *digit_pair, size_t n, unsigned int syntax_bits)
{
  switch (n)
    {
    case 1:
      tm->tm_year = *digit_pair;
      /* Deduce the century based on the year.
         POSIX requires that 00-68 be interpreted as 2000-2068,
         and that 69-99 be interpreted as 1969-1999.  */
      if (digit_pair[0] <= 68)
        {
          if (syntax_bits & PDS_PRE_2000)
            return 1;
          tm->tm_year += 100;
        }
      break;

    case 2:
      if (! (syntax_bits & PDS_CENTURY))
        return 1;
      tm->tm_year = digit_pair[0] * 100 + digit_pair[1] - 1900;
      break;

    case 0:
      {
        time_t now;
        struct tm *tmp;

        /* Use current year.  */
        time (&now);
        tmp = localtime (&now);
        if (! tmp)
          return 1;
        tm->tm_year = tmp->tm_year;
      }
      break;

    default:
      abort ();
    }

  return 0;
}

static int
posix_time_parse (struct tm *tm, const char *s, unsigned int syntax_bits)
{
  const char *dot = NULL;
  int pair[6];
  int *p;
  size_t i;

  size_t s_len = strlen (s);
  size_t len = (((syntax_bits & PDS_SECONDS) && (dot = strchr (s, '.')))
                ? (size_t) (dot - s)
                : s_len);

  if (len != 8 && len != 10 && len != 12)
    return 1;

  if (dot)
    {
      if (!(syntax_bits & PDS_SECONDS))
        return 1;

      if (s_len - len != 3)
        return 1;
    }

  for (i = 0; i < len; i++)
    if (!ISDIGIT (s[i]))
      return 1;

  len /= 2;
  for (i = 0; i < len; i++)
    pair[i] = 10 * (s[2*i] - '0') + s[2*i + 1] - '0';

  p = pair;
  if (syntax_bits & PDS_LEADING_YEAR)
    {
      if (year (tm, p, len - 4, syntax_bits))
        return 1;
      p += len - 4;
      len = 4;
    }

  /* Handle 8 digits worth of `MMDDhhmm'.  */
  tm->tm_mon = *p++ - 1;
  tm->tm_mday = *p++;
  tm->tm_hour = *p++;
  tm->tm_min = *p++;
  len -= 4;

  /* Handle any trailing year.  */
  if (syntax_bits & PDS_TRAILING_YEAR)
    {
      if (year (tm, p, len, syntax_bits))
        return 1;
    }

  /* Handle seconds.  */
  if (!dot)
    {
      tm->tm_sec = 0;
    }
  else
    {
      int seconds;

      ++dot;
      if (!ISDIGIT (dot[0]) || !ISDIGIT (dot[1]))
        return 1;
      seconds = 10 * (dot[0] - '0') + dot[1] - '0';

      tm->tm_sec = seconds;
    }

  return 0;
}

/* Parse a POSIX-style date, returning true if successful.  */

bool
posixtime (time_t *p, const char *s, unsigned int syntax_bits)
{
  struct tm tm0;
  struct tm tm1;
  struct tm const *tm;
  time_t t;

  if (posix_time_parse (&tm0, s, syntax_bits))
    return false;

  tm1 = tm0;
  tm1.tm_isdst = -1;
  t = mktime (&tm1);

  if (t != (time_t) -1)
    tm = &tm1;
  else
    {
      /* mktime returns -1 for errors, but -1 is also a valid time_t
         value.  Check whether an error really occurred.  */
      tm = localtime (&t);
      if (! tm)
        return false;
    }

  /* Reject dates like "September 31" and times like "25:61".
     Do not reject times that specify "60" as the number of seconds.  */
  if ((tm0.tm_year ^ tm->tm_year)
      | (tm0.tm_mon ^ tm->tm_mon)
      | (tm0.tm_mday ^ tm->tm_mday)
      | (tm0.tm_hour ^ tm->tm_hour)
      | (tm0.tm_min ^ tm->tm_min)
      | (tm0.tm_sec ^ tm->tm_sec))
    {
      /* Any mismatch without 60 in the tm_sec field is invalid.  */
      if (tm0.tm_sec != 60)
        return false;

      {
        /* Allow times like 01:35:60 or 23:59:60.  */
        time_t dummy;
        char buf[16];
        char *b = stpcpy (buf, s);
        strcpy (b - 2, "59");
        if (!posixtime (&dummy, buf, syntax_bits))
          return false;
      }
    }

  *p = t;
  return true;
}