#include <dolphin/os.h>

#define OS_TIME_MONTH_MAX 12
#define OS_TIME_WEEK_DAY_MAX 7
#define OS_TIME_YEAR_DAY_MAX 365

// End of each month in standard year
static s32 YearDays[OS_TIME_MONTH_MAX] = {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334};
// End of each month in leap year
static s32 LeapYearDays[OS_TIME_MONTH_MAX] = {0,   31,  60,  91,  121, 152,
                                              182, 213, 244, 274, 305, 335};

asm OSTime OSGetTime(void) {
  // clang-format off
    nofralloc

    mftbu r3
    mftb r4

    // Check for possible carry from TBL to TBU
    mftbu r5
    cmpw r3, r5
    bne OSGetTime

    blr
  // clang-format on
}

asm OSTick OSGetTick(void){
    // clang-format off
    nofralloc

    mftb r3
    blr
    // clang-format on
}

#define OS_SYSTEMTIME_BASE 0x30D8

OSTime __OSGetSystemTime(void) {
  BOOL enabled;
  OSTime* timeAdjustAddr = (OSTime*)(OS_BASE_CACHED + OS_SYSTEMTIME_BASE);
  OSTime result;

  enabled = OSDisableInterrupts();
  result = *timeAdjustAddr + OSGetTime();
  OSRestoreInterrupts(enabled);

  return result;
}

OSTime __OSTimeToSystemTime(OSTime time) {
  BOOL enabled;
  OSTime* timeAdjustAddr = (OSTime*)(OS_BASE_CACHED + OS_SYSTEMTIME_BASE);
  OSTime result;

  enabled = OSDisableInterrupts();
  result = *timeAdjustAddr + time;
  OSRestoreInterrupts(enabled);

  return result;
}

static BOOL IsLeapYear(s32 year) { return (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0); }

static s32 GetYearDays(s32 year, s32 mon) {
  return (IsLeapYear(year) ? LeapYearDays : YearDays)[mon];
}

static s32 GetLeapDays(s32 year) {
  if (year < 1) {
    return 0;
  }
  return (year + 3) / 4 - (year - 1) / 100 + (year - 1) / 400;
}

static void GetDates(s32 days, OSCalendarTime* cal) {
  s32 year;
  s32 totalDays;
  s32* p_days;
  s32 month;
  cal->wday = (days + 6) % OS_TIME_WEEK_DAY_MAX;

  for (year = days / OS_TIME_YEAR_DAY_MAX;
       days < (totalDays = year * OS_TIME_YEAR_DAY_MAX + GetLeapDays(year));) {
    year--;
  }

  days -= totalDays;
  cal->year = year;
  cal->yday = days;

  p_days = IsLeapYear(year) ? LeapYearDays : YearDays;
  month = OS_TIME_MONTH_MAX;
  while (days < p_days[--month]) {
    ;
  }
  cal->mon = month;
  cal->mday = days - p_days[month] + 1;
}

#define BIAS (2000 * 365 + (2000 + 3) / 4 - (2000 - 1) / 100 + (2000 - 1) / 400)

#pragma push
#pragma dont_inline on
void OSTicksToCalendarTime(OSTime ticks, OSCalendarTime* td) {
  int days;
  int secs;
  OSTime d;

  d = ticks % OSSecondsToTicks(1);
  if (d < 0) {
    d += OSSecondsToTicks(1);
  }
  td->usec = (int)(OSTicksToMicroseconds(d) % 1000);
  td->msec = (int)(OSTicksToMilliseconds(d) % 1000);

  ticks -= d;
  days = (int)(OSTicksToSeconds(ticks) / 86400 + BIAS);
  secs = (int)(OSTicksToSeconds(ticks) % 86400);
  if (secs < 0) {
    days -= 1;
    secs += 24 * 60 * 60;
  }

  GetDates(days, td);

  td->hour = secs / 60 / 60;
  td->min = (secs / 60) % 60;
  td->sec = secs % 60;
}
#pragma dont_inline reset

OSTime OSCalendarTimeToTicks(OSCalendarTime* time) {
  ;
  ;
}