#include "project.h"

static int is_leap (unsigned year)
{
  if (year % 4)
    return 0;

  if (year % 100)
    return 1;

  if (year % 400)
    return 0;

  return 1;
}


UTC time_epoch_to_utc (EPOCH epoch)
{
  UTC u;
  uint64_t day;
  unsigned y400, y100, y4;

  day = epoch.s / 86400;
  epoch.s -= day * 86400;

  day += 134774;

  u.wday = day % 7;
  u.wday++;


  y400 = day / 146097;        /*146097 days in 400 years */
  day -= (y400 * 146097);

  y100 = day / 36524;         /*36524 days in 100 years */
  day -= (y100 * 36524);

  y4 = day / 1461;            /*1461 days in 4 years */
  day -= (y4 * 1461);

  /* This may look redundant but 31 Dec in year 4 is special case */
  if (day < 1095) {           /*1095 days in 3 years */
    u.year = day / 365;     /*365 days in a year */
    day -= (365 * u.year);
  } else {
    u.year = 3;
    day -= 1095;
  }


  /* Now put it all back together */
  u.year += 1601;
  u.year += 4 * y4;
  u.year += 100 * y100;
  u.year += 400 * y400;


  u.jday = day + 1;

  u.is_leap = is_leap (u.year);


  if (!u.is_leap) {
    /*Days and months for ordinary years */
    if (u.jday < 32) {
      u.month = 1;
      u.mday = u.jday;
    } else if (u.jday < 60) {
      u.month = 2;
      u.mday = u.jday - 31;
    } else if (u.jday < 91) {
      u.month = 3;
      u.mday = u.jday - 59;
    } else if (u.jday < 121) {
      u.month = 4;
      u.mday = u.jday - 90;
    } else if (u.jday < 152) {
      u.month = 5;
      u.mday = u.jday - 120;
    } else if (u.jday < 182) {
      u.month = 6;
      u.mday = u.jday - 151;
    } else if (u.jday < 213) {
      u.month = 7;
      u.mday = u.jday - 181;
    } else if (u.jday < 244) {
      u.month = 8;
      u.mday = u.jday - 212;
    } else if (u.jday < 274) {
      u.month = 9;
      u.mday = u.jday - 243;
    } else if (u.jday < 305) {
      u.month = 10;
      u.mday = u.jday - 273;
    } else if (u.jday < 335) {
      u.month = 11;
      u.mday = u.jday - 304;
    } else {
      u.month = 12;
      u.mday = u.jday - 334;
    }
  } else {
    /*And leap years */
    if (u.jday < 32) {
      u.month = 1;
      u.mday = u.jday;
    } else if (u.jday < 61) {
      u.month = 2;
      u.mday = u.jday - 31;
    } else if (u.jday < 92) {
      u.month = 3;
      u.mday = u.jday - 60;
    } else if (u.jday < 122) {
      u.month = 4;
      u.mday = u.jday - 91;
    } else if (u.jday < 153) {
      u.month = 5;
      u.mday = u.jday - 121;
    } else if (u.jday < 183) {
      u.month = 6;
      u.mday = u.jday - 152;
    } else if (u.jday < 214) {
      u.month = 7;
      u.mday = u.jday - 182;
    } else if (u.jday < 245) {
      u.month = 8;
      u.mday = u.jday - 213;
    } else if (u.jday < 275) {
      u.month = 9;
      u.mday = u.jday - 244;
    } else if (u.jday < 306) {
      u.month = 10;
      u.mday = u.jday - 274;
    } else if (u.jday < 336) {
      u.month = 11;
      u.mday = u.jday - 305;
    } else {
      u.month = 12;
      u.mday = u.jday - 335;
    }
  }

  u.hour = epoch.s / 3600;
  epoch.s -= u.hour * 3600;
  u.minute = epoch.s / 60;
  epoch.s -= u.minute * 60;
  u.second = epoch.s;

  u.nanosecond = epoch.ns;

  return u;
}




EPOCH  time_utc_to_epoch (UTC u)
{
  unsigned y400;
  unsigned y100;
  unsigned y4;

  EPOCH ret;

  static int const mdays[] =
  { 0, 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 };
  static int const lmdays[] =
  { 0, 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335 };

  u.is_leap = is_leap (u.year);

  if (u.year < 100) u.year += 2000;


  if (!u.jday) {
    if (u.is_leap)
      u.jday = u.mday + lmdays[u.month];
    else
      u.jday = u.mday + mdays[u.month];
  }

  u.year -= 1601;
  y400 = u.year / 400;
  u.year -= y400 * 400;
  y100 = u.year / 100;
  u.year -= y100 * 100;
  y4 = u.year / 4;
  u.year -= y4 * 4;



  ret.s = u.jday - 1;
  ret.s += u.year * 365;
  ret.s += y4 * 1461;
  ret.s += y100 * 36524;
  ret.s += y400 * 146097;

  ret.s -= 134774;

  ret.s *= 86400;

  ret.s += u.second;
  ret.s += u.minute * 60;
  ret.s += u.hour * 3600;

  ret.ns = u.nanosecond;

  return ret;
}

void utc_to_str (char *dst, UTC u)
{
  const char *dname[] = {"Sun", "Mon", "Tue", "Wed", "Thr", "Fri", "Sat", "Sun"};
  const char *mname[] = {"", "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
  sprintf (dst, "%s %04d-%s-%02d %02d:%02d:%02d.%09d", dname[u.wday], u.year, mname[u.month], u.mday, u.hour, u.minute, u.second, u.nanosecond);
}


void time_print_utc (const char *p, UTC u)
{
  const char *dname[] = {"Sun", "Mon", "Tue", "Wed", "Thr", "Fri", "Sat", "Sun"};
  const char *mname[] = {"", "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
  printf ("%s%s %04d-%s-%02d %02d:%02d:%02d.%09d\r\n", p ? p : "", dname[u.wday], u.year, mname[u.month], u.mday, u.hour, u.minute, u.second, u.nanosecond);
}

void time_print_epoch (const char *p, EPOCH e)
{
  UTC u = time_epoch_to_utc (e);
  time_print_utc (p, u);
}