// SPDX-License-Identifier: GPL-2.0+

  /*
   * (C) Copyright 2001
   * Wolfgang Denk, DENX Software Engineering, wd@denx.de.

   */

  #include <common.h>
  #include <command.h>

  #include <errno.h>

  #include <rtc.h>

  #include <linux/time.h>

  #if defined(CONFIG_LIB_DATE) || defined(CONFIG_TIMESTAMP)

  
  #define FEBRUARY		2
  #define	STARTOFTIME		1970
  #define SECDAY			86400L
  #define SECYR			(SECDAY * 365)
  #define	leapyear(year)		((year) % 4 == 0)

  #define	days_in_year(a)		(leapyear(a) ? 366 : 365)
  #define	days_in_month(a)	(month_days[(a) - 1])

  static int month_offset[] = {
  	0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
  };

  /*
   * This only works for the Gregorian calendar - i.e. after 1752 (in the UK)
   */

  int rtc_calc_weekday(struct rtc_time *tm)

  {

  	int leaps_to_date;
  	int last_year;

  	int day;

  	if (tm->tm_year < 1753)

  		return -1;
  	last_year = tm->tm_year - 1;

  	/* Number of leap corrections to apply up to end of last year */
  	leaps_to_date = last_year / 4 - last_year / 100 + last_year / 400;

  
  	/*
  	 * This year is a leap year if it is divisible by 4 except when it is
  	 * divisible by 100 unless it is divisible by 400
  	 *

  	 * e.g. 1904 was a leap year, 1900 was not, 1996 is, and 2000 is.

  	 */

  	if (tm->tm_year % 4 == 0 &&
  	    ((tm->tm_year % 100 != 0) || (tm->tm_year % 400 == 0)) &&
  	    tm->tm_mon > 2) {
  		/* We are past Feb. 29 in a leap year */
  		day = 1;

  	} else {

  		day = 0;

  	}

  	day += last_year * 365 + leaps_to_date + month_offset[tm->tm_mon - 1] +
  			tm->tm_mday;
  	tm->tm_wday = day % 7;

  
  	return 0;

  }

  /*
   * Converts Gregorian date to seconds since 1970-01-01 00:00:00.

   * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
   * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
   *
   * [For the Julian calendar (which was used in Russia before 1917,
   * Britain & colonies before 1752, anywhere else before 1582,
   * and is still in use by some communities) leave out the

   * -year / 100 + year / 400 terms, and add 10.]

   *
   * This algorithm was first published by Gauss (I think).
   *
   * WARNING: this function will overflow on 2106-02-07 06:28:16 on

   * machines where long is 32-bit! (However, as time_t is signed, we

   * will already get problems at other places on 2038-01-19 03:14:08)
   */

  unsigned long rtc_mktime(const struct rtc_time *tm)

  {

  	int mon = tm->tm_mon;
  	int year = tm->tm_year;
  	int days, hours;
  
  	mon -= 2;

  	if (0 >= (int)mon) {	/* 1..12 -> 11, 12, 1..10 */
  		mon += 12;	/* Puts Feb last since it has leap day */

  		year -= 1;
  	}

  	days = (unsigned long)(year / 4 - year / 100 + year / 400 +
  			367 * mon / 12 + tm->tm_mday) +
  			year * 365 - 719499;
  	hours = days * 24 + tm->tm_hour;
  	return (hours * 60 + tm->tm_min) * 60 + tm->tm_sec;

  }

  #endif /* CONFIG_LIB_DATE || CONFIG_TIMESTAMP */

  
  #ifdef CONFIG_LIB_DATE
  /* for compatibility with linux code */
  time64_t mktime64(const unsigned int year, const unsigned int mon,
  		  const unsigned int day, const unsigned int hour,
  		  const unsigned int min, const unsigned int sec)
  {
  	struct rtc_time time;
  
  	time.tm_year = year;
  	time.tm_mon = mon;
  	time.tm_mday = day;
  	time.tm_hour = hour;
  	time.tm_min = min;
  	time.tm_sec = sec;
  
  	return (time64_t)rtc_mktime((const struct rtc_time *)&time);
  }
  #endif