/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at https://curl.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 * SPDX-License-Identifier: curl
 *
 ***************************************************************************/
/*
  A brief summary of the date string formats this parser groks:

  RFC 2616 3.3.1

  Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 822, updated by RFC 1123
  Sunday, 06-Nov-94 08:49:37 GMT ; RFC 850, obsoleted by RFC 1036
  Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format

  we support dates without week day name:

  06 Nov 1994 08:49:37 GMT
  06-Nov-94 08:49:37 GMT
  Nov  6 08:49:37 1994

  without the time zone:

  06 Nov 1994 08:49:37
  06-Nov-94 08:49:37

  weird order:

  1994 Nov 6 08:49:37  (GNU date fails)
  GMT 08:49:37 06-Nov-94 Sunday
  94 6 Nov 08:49:37    (GNU date fails)

  time left out:

  1994 Nov 6
  06-Nov-94
  Sun Nov 6 94

  unusual separators:

  1994.Nov.6
  Sun/Nov/6/94/GMT

  commonly used time zone names:

  Sun, 06 Nov 1994 08:49:37 CET
  06 Nov 1994 08:49:37 EST

  time zones specified using RFC822 style:

  Sun, 12 Sep 2004 15:05:58 -0700
  Sat, 11 Sep 2004 21:32:11 +0200

  compact numerical date strings:

  20040912 15:05:58 -0700
  20040911 +0200

*/

#include "curl_setup.h"

#include <limits.h>

#include <curl/curl.h>
#include "curlx/warnless.h"
#include "parsedate.h"
#include "curlx/strparse.h"

/*
 * parsedate()
 *
 * Returns:
 *
 * PARSEDATE_OK     - a fine conversion
 * PARSEDATE_FAIL   - failed to convert
 * PARSEDATE_LATER  - time overflow at the far end of time_t
 * PARSEDATE_SOONER - time underflow at the low end of time_t
 */

static int parsedate(const char *date, time_t *output);

#define PARSEDATE_OK     0
#define PARSEDATE_FAIL   -1
#define PARSEDATE_LATER  1
#if defined(HAVE_TIME_T_UNSIGNED) || (SIZEOF_TIME_T < 5)
#define PARSEDATE_SOONER 2
#endif

#if !defined(CURL_DISABLE_PARSEDATE) || !defined(CURL_DISABLE_FTP) || \
  !defined(CURL_DISABLE_FILE) || defined(USE_GNUTLS)
/* These names are also used by FTP and FILE code */
const char * const Curl_wkday[] = {
  "Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"
};
const char * const Curl_month[] = {
  "Jan", "Feb", "Mar", "Apr", "May", "Jun",
  "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
};
#endif

#ifndef CURL_DISABLE_PARSEDATE
static const char * const weekday[] = {
  "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"
};

struct tzinfo {
  char name[5];
  int offset; /* +/- in minutes */
};

/* Here's a bunch of frequently used time zone names. These were supported
   by the old getdate parser. */
#define tDAYZONE -60       /* offset for daylight savings time */
static const struct tzinfo tz[] = {
  { "GMT",     0 },          /* Greenwich Mean */
  { "UT",      0 },          /* Universal Time */
  { "UTC",     0 },          /* Universal (Coordinated) */
  { "WET",     0 },          /* Western European */
  { "BST",     0 tDAYZONE }, /* British Summer */
  { "WAT",    60 },          /* West Africa */
  { "AST",   240 },          /* Atlantic Standard */
  { "ADT",   240 tDAYZONE }, /* Atlantic Daylight */
  { "EST",   300 },          /* Eastern Standard */
  { "EDT",   300 tDAYZONE }, /* Eastern Daylight */
  { "CST",   360 },          /* Central Standard */
  { "CDT",   360 tDAYZONE }, /* Central Daylight */
  { "MST",   420 },          /* Mountain Standard */
  { "MDT",   420 tDAYZONE }, /* Mountain Daylight */
  { "PST",   480 },          /* Pacific Standard */
  { "PDT",   480 tDAYZONE }, /* Pacific Daylight */
  { "YST",   540 },          /* Yukon Standard */
  { "YDT",   540 tDAYZONE }, /* Yukon Daylight */
  { "HST",   600 },          /* Hawaii Standard */
  { "HDT",   600 tDAYZONE }, /* Hawaii Daylight */
  { "CAT",   600 },          /* Central Alaska */
  { "AHST",  600 },          /* Alaska-Hawaii Standard */
  { "NT",    660 },          /* Nome */ /* spellchecker:disable-line */
  { "IDLW",  720 },          /* International Date Line West */
  { "CET",   -60 },          /* Central European */
  { "MET",   -60 },          /* Middle European */
  { "MEWT",  -60 },          /* Middle European Winter */
  { "MEST",  -60 tDAYZONE }, /* Middle European Summer */
  { "CEST",  -60 tDAYZONE }, /* Central European Summer */
  { "MESZ",  -60 tDAYZONE }, /* Middle European Summer */
  { "FWT",   -60 },          /* French Winter */
  { "FST",   -60 tDAYZONE }, /* French Summer */
  { "EET",  -120 },          /* Eastern Europe, USSR Zone 1 */
  { "WAST", -420 }, /* spellchecker:disable-line */
                             /* West Australian Standard */
  { "WADT", -420 tDAYZONE }, /* West Australian Daylight */
  { "CCT",  -480 },          /* China Coast, USSR Zone 7 */
  { "JST",  -540 },          /* Japan Standard, USSR Zone 8 */
  { "EAST", -600 },          /* Eastern Australian Standard */
  { "EADT", -600 tDAYZONE }, /* Eastern Australian Daylight */
  { "GST",  -600 },          /* Guam Standard, USSR Zone 9 */
  { "NZT",  -720 },          /* New Zealand */
  { "NZST", -720 },          /* New Zealand Standard */
  { "NZDT", -720 tDAYZONE }, /* New Zealand Daylight */
  { "IDLE", -720 },          /* International Date Line East */
  /* Next up: Military timezone names. RFC822 allowed these, but (as noted in
     RFC 1123) had their signs wrong. Here we use the correct signs to match
     actual military usage.
   */
  { "A",   1 * 60 },         /* Alpha */
  { "B",   2 * 60 },         /* Bravo */
  { "C",   3 * 60 },         /* Charlie */
  { "D",   4 * 60 },         /* Delta */
  { "E",   5 * 60 },         /* Echo */
  { "F",   6 * 60 },         /* Foxtrot */
  { "G",   7 * 60 },         /* Golf */
  { "H",   8 * 60 },         /* Hotel */
  { "I",   9 * 60 },         /* India */
  /* "J", Juliet is not used as a timezone, to indicate the observer's local
     time */
  { "K",  10 * 60 },         /* Kilo */
  { "L",  11 * 60 },         /* Lima */
  { "M",  12 * 60 },         /* Mike */
  { "N",  -1 * 60 },         /* November */
  { "O",  -2 * 60 },         /* Oscar */
  { "P",  -3 * 60 },         /* Papa */
  { "Q",  -4 * 60 },         /* Quebec */
  { "R",  -5 * 60 },         /* Romeo */
  { "S",  -6 * 60 },         /* Sierra */
  { "T",  -7 * 60 },         /* Tango */
  { "U",  -8 * 60 },         /* Uniform */
  { "V",  -9 * 60 },         /* Victor */
  { "W", -10 * 60 },         /* Whiskey */
  { "X", -11 * 60 },         /* X-ray */
  { "Y", -12 * 60 },         /* Yankee */
  { "Z", 0 },                /* Zulu, zero meridian, a.k.a. UTC */
};

/* returns:
   -1 no day
   0 monday - 6 sunday
*/

static int checkday(const char *check, size_t len)
{
  int i;
  const char * const *what;
  if(len > 3)
    what = &weekday[0];
  else if(len == 3)
    what = &Curl_wkday[0];
  else
    return -1; /* too short */
  for(i = 0; i < 7; i++) {
    size_t ilen = strlen(what[0]);
    if((ilen == len) &&
       curl_strnequal(check, what[0], len))
      return i;
    what++;
  }
  return -1;
}

static int checkmonth(const char *check, size_t len)
{
  int i;
  const char * const *what = &Curl_month[0];
  if(len != 3)
    return -1; /* not a month */

  for(i = 0; i < 12; i++) {
    if(curl_strnequal(check, what[0], 3))
      return i;
    what++;
  }
  return -1; /* return the offset or -1, no real offset is -1 */
}

/* return the time zone offset between GMT and the input one, in number
   of seconds or -1 if the timezone was not found/legal */

static int checktz(const char *check, size_t len)
{
  unsigned int i;
  const struct tzinfo *what = tz;
  if(len > 4) /* longer than any valid timezone */
    return -1;

  for(i = 0; i < CURL_ARRAYSIZE(tz); i++) {
    size_t ilen = strlen(what->name);
    if((ilen == len) &&
       curl_strnequal(check, what->name, len))
      return what->offset * 60;
    what++;
  }
  return -1;
}

static void skip(const char **date)
{
  /* skip everything that are not letters or digits */
  while(**date && !ISALNUM(**date))
    (*date)++;
}

enum assume {
  DATE_MDAY,
  DATE_YEAR,
  DATE_TIME
};

/*
 * time2epoch: time stamp to seconds since epoch in GMT time zone. Similar to
 * mktime but for GMT only.
 */
static time_t time2epoch(int sec, int min, int hour,
                         int mday, int mon, int year)
{
  static const int month_days_cumulative[12] = {
    0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
  };
  int leap_days = year - (mon <= 1);
  leap_days = ((leap_days / 4) - (leap_days / 100) + (leap_days / 400)
               - (1969 / 4) + (1969 / 100) - (1969 / 400));
  return ((((time_t)(year - 1970) * 365
            + leap_days + month_days_cumulative[mon] + mday - 1) * 24
           + hour) * 60 + min) * 60 + sec;
}

/* Returns the value of a single-digit or two-digit decimal number, return
   then pointer to after the number. The 'date' pointer is known to point to a
   digit. */
static int oneortwodigit(const char *date, const char **endp)
{
  int num = date[0] - '0';
  if(ISDIGIT(date[1])) {
    *endp = &date[2];
    return num * 10 + (date[1] - '0');
  }
  *endp = &date[1];
  return num;
}

/* HH:MM:SS or HH:MM and accept single-digits too */
static bool match_time(const char *date,
                       int *h, int *m, int *s, char **endp)
{
  const char *p;
  int hh, mm, ss = 0;
  hh = oneortwodigit(date, &p);
  if((hh < 24) && (*p == ':') && ISDIGIT(p[1])) {
    mm = oneortwodigit(&p[1], &p);
    if(mm < 60) {
      if((*p == ':') && ISDIGIT(p[1])) {
        ss = oneortwodigit(&p[1], &p);
        if(ss <= 60) {
          /* valid HH:MM:SS */
          goto match;
        }
      }
      else {
        /* valid HH:MM */
        goto match;
      }
    }
  }
  return FALSE; /* not a time string */
match:
  *h = hh;
  *m = mm;
  *s = ss;
  *endp = (char *)CURL_UNCONST(p);
  return TRUE;
}

/*
 * parsedate()
 *
 * Returns:
 *
 * PARSEDATE_OK     - a fine conversion
 * PARSEDATE_FAIL   - failed to convert
 * PARSEDATE_LATER  - time overflow at the far end of time_t
 * PARSEDATE_SOONER - time underflow at the low end of time_t
 */

/* Wednesday is the longest name this parser knows about */
#define NAME_LEN 12

static int parsedate(const char *date, time_t *output)
{
  time_t t = 0;
  int wdaynum = -1;  /* day of the week number, 0-6 (mon-sun) */
  int monnum = -1;   /* month of the year number, 0-11 */
  int mdaynum = -1;  /* day of month, 1 - 31 */
  int hournum = -1;
  int minnum = -1;
  int secnum = -1;
  int yearnum = -1;
  int tzoff = -1;
  enum assume dignext = DATE_MDAY;
  const char *indate = date; /* save the original pointer */
  int part = 0; /* max 6 parts */

  while(*date && (part < 6)) {
    bool found = FALSE;

    skip(&date);

    if(ISALPHA(*date)) {
      /* a name coming up */
      size_t len = 0;
      const char *p = date;
      while(ISALPHA(*p) && (len < NAME_LEN)) {
        p++;
        len++;
      }

      if(len != NAME_LEN) {
        if(wdaynum == -1) {
          wdaynum = checkday(date, len);
          if(wdaynum != -1)
            found = TRUE;
        }
        if(!found && (monnum == -1)) {
          monnum = checkmonth(date, len);
          if(monnum != -1)
            found = TRUE;
        }

        if(!found && (tzoff == -1)) {
          /* this just must be a time zone string */
          tzoff = checktz(date, len);
          if(tzoff != -1)
            found = TRUE;
        }
      }
      if(!found)
        return PARSEDATE_FAIL; /* bad string */

      date += len;
    }
    else if(ISDIGIT(*date)) {
      /* a digit */
      unsigned int val;
      char *end;
      if((secnum == -1) &&
         match_time(date, &hournum, &minnum, &secnum, &end)) {
        /* time stamp */
        date = end;
      }
      else {
        curl_off_t lval;
        int num_digits = 0;
        const char *p = date;
        if(curlx_str_number(&p, &lval, 99999999))
          return PARSEDATE_FAIL;

        /* we know num_digits cannot be larger than 8 */
        num_digits = (int)(p - date);
        val = (unsigned int)lval;

        if((tzoff == -1) &&
           (num_digits == 4) &&
           (val <= 1400) &&
           (indate < date) &&
           ((date[-1] == '+' || date[-1] == '-'))) {
          /* four digits and a value less than or equal to 1400 (to take into
             account all sorts of funny time zone diffs) and it is preceded
             with a plus or minus. This is a time zone indication. 1400 is
             picked since +1300 is frequently used and +1400 is mentioned as
             an edge number in the document "ISO C 200X Proposal: Timezone
             Functions" at http://david.tribble.com/text/c0xtimezone.html If
             anyone has a more authoritative source for the exact maximum time
             zone offsets, please speak up! */
          found = TRUE;
          tzoff = (val / 100 * 60 + val % 100) * 60;

          /* the + and - prefix indicates the local time compared to GMT,
             this we need their reversed math to get what we want */
          tzoff = date[-1] == '+' ? -tzoff : tzoff;
        }

        else if((num_digits == 8) &&
                (yearnum == -1) &&
                (monnum == -1) &&
                (mdaynum == -1)) {
          /* 8 digits, no year, month or day yet. This is YYYYMMDD */
          found = TRUE;
          yearnum = val / 10000;
          monnum = (val % 10000) / 100 - 1; /* month is 0 - 11 */
          mdaynum = val % 100;
        }

        if(!found && (dignext == DATE_MDAY) && (mdaynum == -1)) {
          if((val > 0) && (val < 32)) {
            mdaynum = val;
            found = TRUE;
          }
          dignext = DATE_YEAR;
        }

        if(!found && (dignext == DATE_YEAR) && (yearnum == -1)) {
          yearnum = val;
          found = TRUE;
          if(yearnum < 100) {
            if(yearnum > 70)
              yearnum += 1900;
            else
              yearnum += 2000;
          }
          if(mdaynum == -1)
            dignext = DATE_MDAY;
        }

        if(!found)
          return PARSEDATE_FAIL;

        date = p;
      }
    }

    part++;
  }

  if(-1 == secnum)
    secnum = minnum = hournum = 0; /* no time, make it zero */

  if((-1 == mdaynum) ||
     (-1 == monnum) ||
     (-1 == yearnum))
    /* lacks vital info, fail */
    return PARSEDATE_FAIL;

#ifdef HAVE_TIME_T_UNSIGNED
  if(yearnum < 1970) {
    /* only positive numbers cannot return earlier */
    *output = TIME_T_MIN;
    return PARSEDATE_SOONER;
  }
#endif

#if (SIZEOF_TIME_T < 5)

#ifdef HAVE_TIME_T_UNSIGNED
  /* an unsigned 32-bit time_t can only hold dates to 2106 */
  if(yearnum > 2105) {
    *output = TIME_T_MAX;
    return PARSEDATE_LATER;
  }
#else
  /* a signed 32-bit time_t can only hold dates to the beginning of 2038 */
  if(yearnum > 2037) {
    *output = TIME_T_MAX;
    return PARSEDATE_LATER;
  }
  if(yearnum < 1903) {
    *output = TIME_T_MIN;
    return PARSEDATE_SOONER;
  }
#endif

#else
  /* The Gregorian calendar was introduced 1582 */
  if(yearnum < 1583)
    return PARSEDATE_FAIL;
#endif

  if((mdaynum > 31) || (monnum > 11) ||
     (hournum > 23) || (minnum > 59) || (secnum > 60))
    return PARSEDATE_FAIL; /* clearly an illegal date */

  /* time2epoch() returns a time_t. time_t is often 32 bits, sometimes even on
     architectures that feature a 64 bits 'long' but ultimately time_t is the
     correct data type to use.
  */
  t = time2epoch(secnum, minnum, hournum, mdaynum, monnum, yearnum);

  /* Add the time zone diff between local time zone and GMT. */
  if(tzoff == -1)
    tzoff = 0;

  if((tzoff > 0) && (t > (time_t)(TIME_T_MAX - tzoff))) {
    *output = TIME_T_MAX;
    return PARSEDATE_LATER; /* time_t overflow */
  }

  t += tzoff;

  *output = t;

  return PARSEDATE_OK;
}
#else
/* disabled */
static int parsedate(const char *date, time_t *output)
{
  (void)date;
  *output = 0;
  return PARSEDATE_OK; /* a lie */
}
#endif

time_t curl_getdate(const char *p, const time_t *now)
{
  time_t parsed = -1;
  int rc = parsedate(p, &parsed);
  (void)now; /* legacy argument from the past that we ignore */

  if(rc == PARSEDATE_OK) {
    if(parsed == (time_t)-1)
      /* avoid returning -1 for a working scenario */
      parsed++;
    return parsed;
  }
  /* everything else is fail */
  return -1;
}

/* Curl_getdate_capped() differs from curl_getdate() in that this will return
   TIME_T_MAX in case the parsed time value was too big, instead of an
   error. Returns non-zero on error. */

int Curl_getdate_capped(const char *p, time_t *tp)
{
  int rc = parsedate(p, tp);
  return (rc == PARSEDATE_FAIL);
}
