/* Written by Richard Levitte (richard@levitte.org) for the OpenSSL
 * project 2001.
 * Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
 * project 2008.
 */
/* ====================================================================
 * Copyright (c) 2001 The OpenSSL Project.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. All advertising materials mentioning features or use of this
 *    software must display the following acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    licensing@OpenSSL.org.
 *
 * 5. Products derived from this software may not be called "OpenSSL"
 *    nor may "OpenSSL" appear in their names without prior written
 *    permission of the OpenSSL Project.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 * ====================================================================
 *
 * This product includes cryptographic software written by Eric Young
 * (eay@cryptsoft.com).  This product includes software written by Tim
 * Hudson (tjh@cryptsoft.com). */

#if !defined(_BSD_SOURCE)
#define _BSD_SOURCE /* for gmtime_r */
#endif

#include <openssl/time_support.h>

#define SECS_PER_DAY (24 * 60 * 60)

struct tm *OPENSSL_gmtime(const time_t *time, struct tm *result) {
#if defined(OPENSSL_WINDOWS)
  if (gmtime_s(result, time)) {
    return NULL;
  }
  return result;
#else
  return gmtime_r(time, result);
#endif
}

/* Convert date to and from julian day Uses Fliegel & Van Flandern algorithm */
static long date_to_julian(int y, int m, int d) {
  return (1461 * (y + 4800 + (m - 14) / 12)) / 4 +
         (367 * (m - 2 - 12 * ((m - 14) / 12))) / 12 -
         (3 * ((y + 4900 + (m - 14) / 12) / 100)) / 4 + d - 32075;
}

static void julian_to_date(long jd, int *y, int *m, int *d) {
  long L = jd + 68569;
  long n = (4 * L) / 146097;
  long i, j;

  L = L - (146097 * n + 3) / 4;
  i = (4000 * (L + 1)) / 1461001;
  L = L - (1461 * i) / 4 + 31;
  j = (80 * L) / 2447;
  *d = L - (2447 * j) / 80;
  L = j / 11;
  *m = j + 2 - (12 * L);
  *y = 100 * (n - 49) + i + L;
}

/* Convert tm structure and offset into julian day and seconds */
static int julian_adj(const struct tm *tm, int off_day, long offset_sec,
                      long *pday, int *psec) {
  int offset_hms, offset_day;
  long time_jd;
  int time_year, time_month, time_day;
  /* split offset into days and day seconds */
  offset_day = offset_sec / SECS_PER_DAY;
  /* Avoid sign issues with % operator */
  offset_hms = offset_sec - (offset_day * SECS_PER_DAY);
  offset_day += off_day;
  /* Add current time seconds to offset */
  offset_hms += tm->tm_hour * 3600 + tm->tm_min * 60 + tm->tm_sec;
  /* Adjust day seconds if overflow */
  if (offset_hms >= SECS_PER_DAY) {
    offset_day++;
    offset_hms -= SECS_PER_DAY;
  } else if (offset_hms < 0) {
    offset_day--;
    offset_hms += SECS_PER_DAY;
  }

  /* Convert date of time structure into a Julian day number. */

  time_year = tm->tm_year + 1900;
  time_month = tm->tm_mon + 1;
  time_day = tm->tm_mday;

  time_jd = date_to_julian(time_year, time_month, time_day);

  /* Work out Julian day of new date */
  time_jd += offset_day;

  if (time_jd < 0)
    return 0;

  *pday = time_jd;
  *psec = offset_hms;
  return 1;
}

int OPENSSL_gmtime_adj(struct tm *tm, int off_day, long offset_sec) {
  int time_sec, time_year, time_month, time_day;
  long time_jd;

  /* Convert time and offset into julian day and seconds */
  if (!julian_adj(tm, off_day, offset_sec, &time_jd, &time_sec))
    return 0;

  /* Convert Julian day back to date */

  julian_to_date(time_jd, &time_year, &time_month, &time_day);

  if (time_year < 1900 || time_year > 9999)
    return 0;

  /* Update tm structure */

  tm->tm_year = time_year - 1900;
  tm->tm_mon = time_month - 1;
  tm->tm_mday = time_day;

  tm->tm_hour = time_sec / 3600;
  tm->tm_min = (time_sec / 60) % 60;
  tm->tm_sec = time_sec % 60;

  return 1;
}

int OPENSSL_gmtime_diff(int *pday, int *psec, const struct tm *from,
                        const struct tm *to) {
  int from_sec, to_sec, diff_sec;
  long from_jd, to_jd, diff_day;

  if (!julian_adj(from, 0, 0, &from_jd, &from_sec)) {
    return 0;
  }
  if (!julian_adj(to, 0, 0, &to_jd, &to_sec)) {
    return 0;
  }

  diff_day = to_jd - from_jd;
  diff_sec = to_sec - from_sec;
  /* Adjust differences so both positive or both negative */
  if (diff_day > 0 && diff_sec < 0) {
    diff_day--;
    diff_sec += SECS_PER_DAY;
  }
  if (diff_day < 0 && diff_sec > 0) {
    diff_day++;
    diff_sec -= SECS_PER_DAY;
  }

  if (pday) {
    *pday = (int)diff_day;
  }
  if (psec) {
    *psec = diff_sec;
  }

  return 1;
}