/*
   * (C) Copyright 2001
   * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
   *
   * SPDX-License-Identifier:	GPL-2.0+
   */
  
  /*
   * Date & Time support for Philips PCF8563 RTC
   */
  
  #include <common.h>
  #include <command.h>
  #include <rtc.h>
  
  #if defined(CONFIG_CMD_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_days[12] = {
  	31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
  };
  
  /*
   * This only works for the Gregorian calendar - i.e. after 1752 (in the UK)
   */
  void GregorianDay(struct rtc_time * tm)
  {
  	int leapsToDate;
  	int lastYear;
  	int day;
  	int MonthOffset[] = { 0,31,59,90,120,151,181,212,243,273,304,334 };
  
  	lastYear=tm->tm_year-1;
  
  	/*
  	 * Number of leap corrections to apply up to end of last year
  	 */
  	leapsToDate = lastYear/4 - lastYear/100 + lastYear/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 will be
  	 */
  	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 += lastYear*365 + leapsToDate + MonthOffset[tm->tm_mon-1] + tm->tm_mday;
  
  	tm->tm_wday=day%7;
  }
  
  void to_tm(int tim, struct rtc_time * tm)
  {
  	register int    i;
  	register long   hms, day;
  
  	day = tim / SECDAY;
  	hms = tim % SECDAY;
  
  	/* Hours, minutes, seconds are easy */
  	tm->tm_hour = hms / 3600;
  	tm->tm_min = (hms % 3600) / 60;
  	tm->tm_sec = (hms % 3600) % 60;
  
  	/* Number of years in days */
  	for (i = STARTOFTIME; day >= days_in_year(i); i++) {
  		day -= days_in_year(i);
  	}
  	tm->tm_year = i;
  
  	/* Number of months in days left */
  	if (leapyear(tm->tm_year)) {
  		days_in_month(FEBRUARY) = 29;
  	}
  	for (i = 1; day >= days_in_month(i); i++) {
  		day -= days_in_month(i);
  	}
  	days_in_month(FEBRUARY) = 28;
  	tm->tm_mon = i;
  
  	/* Days are what is left over (+1) from all that. */
  	tm->tm_mday = day + 1;
  
  	/*
  	 * Determine the day of week
  	 */
  	GregorianDay(tm);
  }
  
  /* 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 were 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
  mktime (unsigned int year, unsigned int mon,
  	unsigned int day, unsigned int hour,
  	unsigned int min, unsigned int sec)
  {
  	if (0 >= (int) (mon -= 2)) {	/* 1..12 -> 11,12,1..10 */
  		mon += 12;		/* Puts Feb last since it has leap day */
  		year -= 1;
  	}
  
  	return (((
  		(unsigned long) (year/4 - year/100 + year/400 + 367*mon/12 + day) +
  			year*365 - 719499
  	    )*24 + hour /* now have hours */
  	  )*60 + min /* now have minutes */
  	)*60 + sec; /* finally seconds */
  }
  
  #endif