import asm


RTC_CMOS_ADDR: uint16 = 0x70
RTC_CMOS_DATA: uint16 = 0x71

define RTC_REG_SECONDS = 0x00
define RTC_REG_MINUTES = 0x02
define RTC_REG_HOURS = 0x04
define RTC_REG_DAY = 0x07
define RTC_REG_MONTH = 0x08
define RTC_REG_YEAR = 0x09
define RTC_REG_STATUS_A = 0x0A
define RTC_REG_STATUS_B = 0x0B

define RTC_TZ_OFFSET = 8

static rtc_seconds: volatile uint8 = 0
static rtc_minutes: volatile uint8 = 0
static rtc_hours:   volatile uint8 = 0
static rtc_day:     volatile uint8 = 0
static rtc_month:   volatile uint8 = 0
static rtc_year:    volatile uint16 = 0

def cmos_read(reg: uint8) -> uint8:
    asm.outb(RTC_CMOS_ADDR, reg)
    return asm.inb(RTC_CMOS_DATA)

def bcd_to_bin(bcd: uint8) -> uint8:
    return (bcd >> 4) * 10 + (bcd & 0x0F)

def rtc_read_time():
    while cmos_read(RTC_REG_STATUS_A) & 0x80: pass
    sec:   uint8 = cmos_read(RTC_REG_SECONDS)
    min_:  uint8 = cmos_read(RTC_REG_MINUTES)
    hour:  uint8 = cmos_read(RTC_REG_HOURS)
    day:   uint8 = cmos_read(RTC_REG_DAY)
    mon:   uint8 = cmos_read(RTC_REG_MONTH)
    year:  uint8 = cmos_read(RTC_REG_YEAR)
    reg_b: uint8 = cmos_read(RTC_REG_STATUS_B)
    if not (reg_b & 0x04):
        sec  = bcd_to_bin(sec)
        min_ = bcd_to_bin(min_)
        hour = bcd_to_bin(hour)
        day  = bcd_to_bin(day)
        mon  = bcd_to_bin(mon)
        year = bcd_to_bin(year)
    if not (reg_b & 0x02) and (hour & 0x80):
        hour = ((hour & 0x7F) + 12) % 24
    hour = hour + RTC_TZ_OFFSET
    if hour >= 24:
        hour = hour - 24
        day = day + 1
        max_day: uint8 = 31
        if mon == 4 or mon == 6 or mon == 9 or mon == 11:
            max_day = 30
        elif mon == 2:
            max_day = 28
            y4: uint16 = uint16(year) + 2000
            if (y4 % 4 == 0 and y4 % 100 != 0) or (y4 % 400 == 0):
                max_day = 29
        if day > max_day:
            day = 1
            mon = mon + 1
            if mon > 12:
                mon = 1
                year = year + 1
    global rtc_seconds, rtc_minutes, rtc_hours, rtc_day, rtc_month, rtc_year
    rtc_seconds = sec
    rtc_minutes = min_
    rtc_hours = hour
    rtc_day = day
    rtc_month = mon
    rtc_year = uint16(year) + 2000

def rtc_init():                  rtc_read_time()
def rtc_get_hours()   -> uint8:  return rtc_hours
def rtc_get_minutes() -> uint8:  return rtc_minutes
def rtc_get_seconds() -> uint8:  return rtc_seconds
def rtc_get_day()     -> uint8:  return rtc_day
def rtc_get_month()   -> uint8:  return rtc_month
def rtc_get_year()    -> uint16: return rtc_year