/*

 * libwebsockets - small server side websockets and web server implementation

 *

 * Copyright (C) 2010 - 2020 Andy Green <andy@warmcat.com>

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this software and associated documentation files (the "Software"), to

 * deal in the Software without restriction, including without limitation the

 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or

 * sell copies of the Software, and to permit persons to whom the Software is

 * furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS

 * IN THE SOFTWARE.

 *

 * RFC7231 date string generation and parsing

 */

#include "private-lib-core.h"

/*

 * To avoid needless pointers, we encode these in one string using the fact

 * they're 3 chars each to index it

 */

static const char *const s =

    "JanFebMarAprMayJunJulAugSepOctNovDecMonTueWedThuFriSatSun";

static int

lws_http_date_render(char *buf, size_t len, const struct tm *tm)

{

  const char *w = s + 36 + (3 * tm->tm_wday), *m = s + (3 * tm->tm_mon);

  if (len < 29)

    return -1;

  lws_snprintf(buf, len, "%c%c%c, %02d %c%c%c %d %02d:%02d:%02d GMT",

         w[0], w[1], w[2], tm->tm_mday, m[0], m[1], m[2],

         1900 + tm->tm_year, tm->tm_hour, tm->tm_min, tm->tm_sec);

  return 0;

}

int

lws_http_date_render_from_unix(char *buf, size_t len, const time_t *t)

{

#if defined(LWS_HAVE_GMTIME_R)

  struct tm tmp;

  struct tm *tm = gmtime_r(t, &tmp);

#else

  struct tm *tm = gmtime(t);

#endif

  if (!tm)

    return -1;

  if (lws_http_date_render(buf, len, tm))

    return -1;

  return 0;

}

static int

lws_http_date_parse(const char *b, size_t len, struct tm *tm)

{

  int n;

  if (len < 29)

    return -1;

  /*

   * We reject anything that isn't a properly-formatted RFC7231 date, eg

   *

   *     Tue, 15 Nov 1994 08:12:31 GMT

   */

  if (b[3] != ','  || b[4] != ' '  || b[7] != ' '  || b[11] != ' ' ||

      b[16] != ' ' || b[19] != ':' || b[22] != ':' || b[25] != ' ' ||

      b[26] != 'G' || b[27] != 'M' || b[28] != 'T')

    return -1;

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

  for (n = 36; n < 57; n += 3)

    if (b[0] == s[n] && b[1] == s[n + 1] && b[2] == s[n + 2])

      break;

    else

      tm->tm_wday++;

  if (n == 57)

    return -1;

  for (n = 0; n < 36; n += 3)

    if (b[8] == s[n] && b[9] == s[n + 1] && b[10] == s[n + 2])

      break;

    else

      tm->tm_mon++;

  if (n == 36)

    return -1;

  tm->tm_mday = atoi(b + 5);

  n = atoi(b + 12);

  if (n < 1900)

    return -1;

  tm->tm_year = n - 1900;

  n = atoi(b + 17);

  if (n < 0 || n > 23)

    return -1;

  tm->tm_hour = n;

  n = atoi(b + 20);

  if (n < 0 || n > 60)

    return -1;

  tm->tm_min = n;

  n = atoi(b + 23);

  if (n < 0 || n > 61) /* leap second */

    return -1;

  tm->tm_sec = n;

  return 0;

}

int

lws_http_date_parse_unix(const char *b, size_t len, time_t *t)

{

  struct tm tm;

  if (lws_http_date_parse(b, len, &tm))

    return -1;

#if defined(WIN32)

  *t = _mkgmtime(&tm);

#else

#if defined(LWS_HAVE_TIMEGM)

  *t = timegm(&tm);

#else

  /* this is a poor fallback since it uses localtime zone */

  *t = mktime(&tm);

#endif

#endif

  return (int)*t == -1 ? -1 : 0;

}

#if defined(LWS_WITH_CLIENT)

int

lws_http_check_retry_after(struct lws *wsi, lws_usec_t *us_interval_in_out)

{

  size_t len = (unsigned int)lws_hdr_total_length(wsi, WSI_TOKEN_HTTP_RETRY_AFTER);

  char *p = lws_hdr_simple_ptr(wsi, WSI_TOKEN_HTTP_RETRY_AFTER);

  lws_usec_t u;

  time_t t, td;

  if (!p)

    return 1;

  /*

   * There are two arg styles for RETRY_AFTER specified in RFC7231 7.1.3,

   * either a full absolute second-resolution date/time, or an integer

   * interval

   *

   *      Retry-After: Fri, 31 Dec 1999 23:59:59 GMT

         *      Retry-After: 120

   */

  if (len < 9)

    u = ((lws_usec_t)(time_t)atoi(p)) * LWS_USEC_PER_SEC;

  else {

    if (lws_http_date_parse_unix(p, len, &t))

      return 1;

    /*

     * If possible, look for DATE from the server as well, so we

     * can calculate the interval it thinks it is giving us,

     * eliminating problems from server - client clock skew

     */

    time(&td);

    len = (unsigned int)lws_hdr_total_length(wsi, WSI_TOKEN_HTTP_DATE);

    if (len) {

      p = lws_hdr_simple_ptr(wsi, WSI_TOKEN_HTTP_DATE);

      /* if this fails, it leaves td as client time */

      (void)lws_http_date_parse_unix(p, len, &td);

    }

    if (td >= t)

      /*

       * if he's effectively giving us a 0 or negative

       * interval, just ignore the whole thing and keep the

       * incoming interval

       */

      return 1;

    u = ((lws_usec_t)(t - td)) * LWS_USEC_PER_SEC;

  }

  /*

   * We are only willing to increase the incoming interval, not

   * decrease it

   */

  if (u < *us_interval_in_out)

    /* keep the incoming interval */

    return 1;

  /* use the computed interval */

  *us_interval_in_out = u;

  return 0;

}

#endif