text: /*
   * This file is part of the MicroPython project, http://micropython.org/
   *
   * The MIT License (MIT)
   *
   * SPDX-FileCopyrightText: Copyright (c) 2013, 2014 Damien P. George
   * SPDX-FileCopyrightText: Copyright (c) 2015 Daniel Campora
   *
   * 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.
   */
  
  #include "py/obj.h"
  
  #include "shared/timeutils/timeutils.h"
  
  // LEAPOCH corresponds to 2000-03-01, which is a mod-400 year, immediately
  // after Feb 29. We calculate seconds as a signed integer relative to that.
  //
  // Our timebase is relative to 2000-01-01.
  
  #define LEAPOCH ((31 + 29) * 86400)
  
  #define DAYS_PER_400Y (365 * 400 + 97)
  #define DAYS_PER_100Y (365 * 100 + 24)
  #define DAYS_PER_4Y   (365 * 4 + 1)
  
  STATIC const uint16_t days_since_jan1[] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 };
  
  bool timeutils_is_leap_year(mp_uint_t year) {
      return (year % 4 == 0 && year % 100 != 0) || year % 400 == 0;
  }
  
  // month is one based
  mp_uint_t timeutils_days_in_month(mp_uint_t year, mp_uint_t month) {
      mp_uint_t mdays = days_since_jan1[month] - days_since_jan1[month - 1];
      if (month == 2 && timeutils_is_leap_year(year)) {
          mdays++;
      }
      return mdays;
  }
  
  // compute the day of the year, between 1 and 366
  // month should be between 1 and 12, date should start at 1
  mp_uint_t timeutils_year_day(mp_uint_t year, mp_uint_t month, mp_uint_t date) {
      mp_uint_t yday = days_since_jan1[month - 1] + date;
      if (month >= 3 && timeutils_is_leap_year(year)) {
          yday += 1;
      }
      return yday;
  }
  
  void timeutils_seconds_since_2000_to_struct_time(mp_uint_t t, timeutils_struct_time_t *tm) {
      // The following algorithm was adapted from musl's __secs_to_tm and adapted
      // for differences in MicroPython's timebase.
  
      mp_int_t seconds = t - LEAPOCH;
  
      mp_int_t days = seconds / 86400;
      seconds %= 86400;
      if (seconds < 0) {
          seconds += 86400;
          days -= 1;
      }
      tm->tm_hour = seconds / 3600;
      tm->tm_min = seconds / 60 % 60;
      tm->tm_sec = seconds % 60;
  
      mp_int_t wday = (days + 2) % 7;   // Mar 1, 2000 was a Wednesday (2)
      if (wday < 0) {
          wday += 7;
      }
      tm->tm_wday = wday;
  
      mp_int_t qc_cycles = days / DAYS_PER_400Y;
      days %= DAYS_PER_400Y;
      if (days < 0) {
          days += DAYS_PER_400Y;
          qc_cycles--;
      }
      mp_int_t c_cycles = days / DAYS_PER_100Y;
      if (c_cycles == 4) {
          c_cycles--;
      }
      days -= (c_cycles * DAYS_PER_100Y);
  
      mp_int_t q_cycles = days / DAYS_PER_4Y;
      if (q_cycles == 25) {
          q_cycles--;
      }
      days -= q_cycles * DAYS_PER_4Y;
  
      mp_int_t years = days / 365;
      if (years == 4) {
          years--;
      }
      days -= (years * 365);
  
      /* We will compute tm_yday at the very end
      mp_int_t leap = !years && (q_cycles || !c_cycles);
  
      tm->tm_yday = days + 31 + 28 + leap;
      if (tm->tm_yday >= 365 + leap) {
          tm->tm_yday -= 365 + leap;
      }
  
      tm->tm_yday++;  // Make one based
      */
  
      tm->tm_year = 2000 + years + 4 * q_cycles + 100 * c_cycles + 400 * qc_cycles;
  
      // Note: days_in_month[0] corresponds to March
      STATIC const int8_t days_in_month[] = {31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 31, 29};
  
      mp_int_t month;
      for (month = 0; days_in_month[month] <= days; month++) {
          days -= days_in_month[month];
      }
  
      tm->tm_mon = month + 2;
      if (tm->tm_mon >= 12) {
          tm->tm_mon -= 12;
          tm->tm_year++;
      }
      tm->tm_mday = days + 1; // Make one based
      tm->tm_mon++;   // Make one based
  
      tm->tm_yday = timeutils_year_day(tm->tm_year, tm->tm_mon, tm->tm_mday);
  }
  
  // returns the number of seconds, as an integer, since 2000-01-01
  mp_uint_t timeutils_seconds_since_2000(mp_uint_t year, mp_uint_t month,
      mp_uint_t date, mp_uint_t hour, mp_uint_t minute, mp_uint_t second) {
      return
          second
          + minute * 60
          + hour * 3600
          + (timeutils_year_day(year, month, date) - 1
              + ((year - 2000 + 3) / 4) // add a day each 4 years starting with 2001
              - ((year - 2000 + 99) / 100) // subtract a day each 100 years starting with 2001
              + ((year - 2000 + 399) / 400) // add a day each 400 years starting with 2001
              ) * 86400
          + (year - 2000) * 31536000;
  }
  
  mp_uint_t timeutils_mktime_2000(mp_uint_t year, mp_int_t month, mp_int_t mday,
      mp_int_t hours, mp_int_t minutes, mp_int_t seconds) {
  
      // Normalize the tuple. This allows things like:
      //
      // tm_tomorrow = list(time.localtime())
      // tm_tomorrow[2] += 1 # Adds 1 to mday
      // tomorrow = time.mktime(tm_tomorrow)
      //
      // And not have to worry about all the weird overflows.
      //
      // You can subtract dates/times this way as well.
  
      minutes += seconds / 60;
      if ((seconds = seconds % 60) < 0) {
          seconds += 60;
          minutes--;
      }
  
      hours += minutes / 60;
      if ((minutes = minutes % 60) < 0) {
          minutes += 60;
          hours--;
      }
  
      mday += hours / 24;
      if ((hours = hours % 24) < 0) {
          hours += 24;
          mday--;
      }
  
      month--; // make month zero based
      year += month / 12;
      if ((month = month % 12) < 0) {
          month += 12;
          year--;
      }
      month++; // back to one based
  
      while (mday < 1) {
          if (--month == 0) {
              month = 12;
              year--;
          }
          mday += timeutils_days_in_month(year, month);
      }
      while ((mp_uint_t)mday > timeutils_days_in_month(year, month)) {
          mday -= timeutils_days_in_month(year, month);
          if (++month == 13) {
              month = 1;
              year++;
          }
      }
      return timeutils_seconds_since_2000(year, month, mday, hours, minutes, seconds);
  }
  
  // Calculate the weekday from the date.
  // The result is zero based with 0 = Monday.
  // by Michael Keith and Tom Craver, 1990.
  int timeutils_calc_weekday(int y, int m, int d) {
      return ((d += m < 3 ? y-- : y - 2, 23 * m / 9 + d + 4 + y / 4 - y / 100 + y / 400) + 6) % 7;
  }
  