/*
 * sntp-lwip2.c - ESP8266-specific functions for SNTP and lwIP-v2
 * Copyright (c) 2015 Espressif (license is tools/sdk/lwip/src/core/sntp.c's)
 * 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. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission. 
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS 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 AUTHOR 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.
 *
 *
 * History:
 * This code is extracted from lwip1.4-espressif's sntp.c
 * which is a patched version of the original lwip1's sntp.
 * (check the mix-up in tools/sdk/lwip/src/core/sntp.c)
 * It is moved here as-is and cleaned for maintainability and
 * because it does not belong to lwip.
 *
 * TODOs:
 * settimeofday(): handle tv->tv_usec
 * sntp_mktm_r(): review, fix DST handling (this one is currently untouched from lwip-1.4)
 * implement adjtime()
 */

#include <lwip/init.h>
#include <sys/time.h>
#include <osapi.h>
#include <os_type.h>
#include "coredecls.h"

static void (*_settimeofday_cb)(void) = NULL;

void settimeofday_cb (void (*cb)(void))
{
    _settimeofday_cb = cb;
}

#if LWIP_VERSION_MAJOR == 1

#include <pgmspace.h>

static const char stod14[] PROGMEM = "settimeofday() can't set time!\n";

int settimeofday(const struct timeval* tv, const struct timezone* tz)
{
    if (tz) /*before*/
    {
        sntp_set_timezone(tz->tz_minuteswest / 60);
        // apparently tz->tz_dsttime is a bitfield and should not be further used (cf man)
        sntp_set_daylight(0);
    }
    if (tv) /* after*/
    {
        // can't call lwip1.4's static sntp_set_system_time()
        os_printf(stod14);

        // reset time subsystem
        timeshift64_is_set = false;
        
        return -1;
    }
    return 0;
}

#endif // lwip 1.4 only

#if LWIP_VERSION_MAJOR == 2

#include <lwip/apps/sntp.h>

static uint32 realtime_stamp = 0;
static uint16 dst = 0;
static sint8 time_zone = 8; // espressif HQ's default timezone
LOCAL os_timer_t sntp_timer;

/*****************************************/
#define SECSPERMIN	60L
#define MINSPERHOUR	60L
#define HOURSPERDAY	24L
#define SECSPERHOUR	(SECSPERMIN * MINSPERHOUR)
#define SECSPERDAY	(SECSPERHOUR * HOURSPERDAY)
#define DAYSPERWEEK	7
#define MONSPERYEAR	12

#define YEAR_BASE	1900
#define EPOCH_YEAR      1970
#define EPOCH_WDAY      4
#define EPOCH_YEARS_SINCE_LEAP 2
#define EPOCH_YEARS_SINCE_CENTURY 70
#define EPOCH_YEARS_SINCE_LEAP_CENTURY 370

#define isleap(y) ((((y) % 4) == 0 && ((y) % 100) != 0) || ((y) % 400) == 0)

int __tznorth;
int __tzyear;
char reult[100];
static const int mon_lengths[2][12] = {
  {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
  {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
} ;

static const int year_lengths[2] = {
  365,
  366
} ;
struct tm
{
  int	tm_sec;
  int	tm_min;
  int	tm_hour;
  int	tm_mday;
  int	tm_mon;
  int	tm_year;
  int	tm_wday;
  int	tm_yday;
  int	tm_isdst;
};

struct tm res_buf;
typedef struct __tzrule_struct
{
  char ch;
  int m;
  int n;
  int d;
  int s;
  time_t change;
  int offset;
} __tzrule_type;

__tzrule_type sntp__tzrule[2];
struct tm *
sntp_mktm_r(const time_t * tim_p ,struct tm *res ,int is_gmtime)
{
  long days, rem;
  time_t lcltime;
  int y;
  int yleap;
  const int *ip;

  /* base decision about std/dst time on current time */
  lcltime = *tim_p;

  days = ((long)lcltime) / SECSPERDAY;
  rem = ((long)lcltime) % SECSPERDAY;
  while (rem < 0)
    {
      rem += SECSPERDAY;
      --days;
    }
  while (rem >= SECSPERDAY)
    {
      rem -= SECSPERDAY;
      ++days;
    }

  /* compute hour, min, and sec */
  res->tm_hour = (int) (rem / SECSPERHOUR);
  rem %= SECSPERHOUR;
  res->tm_min = (int) (rem / SECSPERMIN);
  res->tm_sec = (int) (rem % SECSPERMIN);

  /* compute day of week */
  if ((res->tm_wday = ((EPOCH_WDAY + days) % DAYSPERWEEK)) < 0)
    res->tm_wday += DAYSPERWEEK;

  /* compute year & day of year */
  y = EPOCH_YEAR;
  if (days >= 0)
    {
      for (;;)
	{
	  yleap = isleap(y);
	  if (days < year_lengths[yleap])
	    break;
	  y++;
	  days -= year_lengths[yleap];
	}
    }
  else
    {
      do
	{
	  --y;
	  yleap = isleap(y);
	  days += year_lengths[yleap];
	} while (days < 0);
    }

  res->tm_year = y - YEAR_BASE;
  res->tm_yday = days;
  ip = mon_lengths[yleap];
  for (res->tm_mon = 0; days >= ip[res->tm_mon]; ++res->tm_mon)
    days -= ip[res->tm_mon];
  res->tm_mday = days + 1;

  if (!is_gmtime)
    {
      int offset;
      int hours, mins, secs;

//      TZ_LOCK;
//      if (_daylight)
//	{
//	  if (y == __tzyear || __tzcalc_limits (y))
//	    res->tm_isdst = (__tznorth
//			     ? (*tim_p >= __tzrule[0].change && *tim_p < __tzrule[1].change)
//			     : (*tim_p >= __tzrule[0].change || *tim_p < __tzrule[1].change));
//	  else
//	    res->tm_isdst = -1;
//	}
//      else
      res->tm_isdst = -1;

      offset = (res->tm_isdst == 1 ? sntp__tzrule[1].offset : sntp__tzrule[0].offset);

      hours = offset / SECSPERHOUR;
      offset = offset % SECSPERHOUR;

      mins = offset / SECSPERMIN;
      secs = offset % SECSPERMIN;

      res->tm_sec -= secs;
      res->tm_min -= mins;
      res->tm_hour -= hours;

      if (res->tm_sec >= SECSPERMIN)
	{
	  res->tm_min += 1;
	  res->tm_sec -= SECSPERMIN;
	}
      else if (res->tm_sec < 0)
	{
	  res->tm_min -= 1;
	  res->tm_sec += SECSPERMIN;
	}
      if (res->tm_min >= MINSPERHOUR)
	{
	  res->tm_hour += 1;
	  res->tm_min -= MINSPERHOUR;
	}
      else if (res->tm_min < 0)
	{
	  res->tm_hour -= 1;
	  res->tm_min += MINSPERHOUR;
	}
      if (res->tm_hour >= HOURSPERDAY)
	{
	  ++res->tm_yday;
	  ++res->tm_wday;
	  if (res->tm_wday > 6)
	    res->tm_wday = 0;
	  ++res->tm_mday;
	  res->tm_hour -= HOURSPERDAY;
	  if (res->tm_mday > ip[res->tm_mon])
	    {
	      res->tm_mday -= ip[res->tm_mon];
	      res->tm_mon += 1;
	      if (res->tm_mon == 12)
		{
		  res->tm_mon = 0;
		  res->tm_year += 1;
		  res->tm_yday = 0;
		}
	    }
	}
       else if (res->tm_hour < 0)
	{
	  res->tm_yday -= 1;
	  res->tm_wday -= 1;
	  if (res->tm_wday < 0)
	    res->tm_wday = 6;
	  res->tm_mday -= 1;
	  res->tm_hour += 24;
	  if (res->tm_mday == 0)
	    {
	      res->tm_mon -= 1;
	      if (res->tm_mon < 0)
		{
		  res->tm_mon = 11;
		  res->tm_year -= 1;
		  res->tm_yday = 365 + isleap(res->tm_year);
		}
	      res->tm_mday = ip[res->tm_mon];
	    }
	}
//      TZ_UNLOCK;
    }
  else
    res->tm_isdst = 0;
//  os_printf("res %d %d %d %d %d\n",res->tm_year,res->tm_mon,res->tm_mday,res->tm_yday,res->tm_hour);
  return (res);
}
struct tm *
sntp_localtime_r(const time_t * tim_p ,
		struct tm *res)
{
  return sntp_mktm_r (tim_p, res, 0);
}

struct tm *
sntp_localtime(const time_t * tim_p)
{
  return sntp_localtime_r (tim_p, &res_buf);
}

int sntp__tzcalc_limits(int year)
{
  int days, year_days, years;
  int i, j;

  if (year < EPOCH_YEAR)
    return 0;

  __tzyear = year;

  years = (year - EPOCH_YEAR);

  year_days = years * 365 +
    (years - 1 + EPOCH_YEARS_SINCE_LEAP) / 4 - (years - 1 + EPOCH_YEARS_SINCE_CENTURY) / 100 +
    (years - 1 + EPOCH_YEARS_SINCE_LEAP_CENTURY) / 400;

  for (i = 0; i < 2; ++i)
    {
      if (sntp__tzrule[i].ch == 'J')
	days = year_days + sntp__tzrule[i].d + (isleap(year) && sntp__tzrule[i].d >= 60);
      else if (sntp__tzrule[i].ch == 'D')
	days = year_days + sntp__tzrule[i].d;
      else
	{
	  int yleap = isleap(year);
	  int m_day, m_wday, wday_diff;
	  const int *ip = mon_lengths[yleap];

	  days = year_days;

	  for (j = 1; j < sntp__tzrule[i].m; ++j)
	    days += ip[j-1];

	  m_wday = (EPOCH_WDAY + days) % DAYSPERWEEK;

	  wday_diff = sntp__tzrule[i].d - m_wday;
	  if (wday_diff < 0)
	    wday_diff += DAYSPERWEEK;
	  m_day = (sntp__tzrule[i].n - 1) * DAYSPERWEEK + wday_diff;

	  while (m_day >= ip[j-1])
	    m_day -= DAYSPERWEEK;

	  days += m_day;
	}

      /* store the change-over time in GMT form by adding offset */
      sntp__tzrule[i].change = days * SECSPERDAY + sntp__tzrule[i].s + sntp__tzrule[i].offset;
    }

  __tznorth = (sntp__tzrule[0].change < sntp__tzrule[1].change);

  return 1;
}

char* sntp_asctime_r(struct tm *tim_p ,char *result)
{
  static const char day_name[7][4] = {
	"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
  };
  static const char mon_name[12][4] = {
	"Jan", "Feb", "Mar", "Apr", "May", "Jun",
	"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
  };
  os_sprintf (result, "%s %s %02d %02d:%02d:%02d %02d\n",
	   day_name[tim_p->tm_wday],
	   mon_name[tim_p->tm_mon],
	   tim_p->tm_mday, tim_p->tm_hour, tim_p->tm_min,
	   tim_p->tm_sec, 1900 + tim_p->tm_year);
  return result;
}

char* sntp_asctime(struct tm *tim_p)
{
    return sntp_asctime_r (tim_p, reult);
}

uint32 ICACHE_RAM_ATTR sntp_get_current_timestamp(void)
{
    return realtime_stamp;
}

char* sntp_get_real_time(time_t t)
{
    return sntp_asctime(sntp_localtime (&t));
}

sint8 sntp_get_timezone(void)
{
    return time_zone;
}

bool sntp_set_timezone(sint8 timezone)
{
    if(timezone >= -11 || timezone <= 13) {
        time_zone = timezone;
        return true;
    } else {
        return false;
    }
}

void sntp_set_daylight(int daylight)
{
    dst = daylight;
}

void ICACHE_RAM_ATTR sntp_time_inc (void)
{
    realtime_stamp++;
}

static void sntp_set_system_time (uint32_t t)
{
    realtime_stamp = t + time_zone * 60 * 60 + dst;
    os_timer_disarm(&sntp_timer);
    os_timer_setfn(&sntp_timer, (os_timer_func_t *)sntp_time_inc, NULL);
    os_timer_arm(&sntp_timer, 1000, 1);
}

int settimeofday(const struct timeval* tv, const struct timezone* tz)
{
    if (tz) /*before*/
    {
        sntp_set_timezone(tz->tz_minuteswest / 60);
        // apparently tz->tz_dsttime is a bitfield and should not be further used (cf man)
        sntp_set_daylight(0);
    }
    if (tv) /* after*/
    {
        // reset time subsystem
        tune_timeshift64(tv->tv_sec * 1000000ULL + tv->tv_usec);

        sntp_set_system_time(tv->tv_sec);

        if (_settimeofday_cb)
            _settimeofday_cb();
    }
    return 0;
}

#endif // lwip2 only