#include <amd64/io.h>
#include <amd64/rtc.h>
#include <libk/std.h>
#include <limine/requests.h>
#include <sys/debug.h>
#include <sys/spin.h>
#include <sys/stall.h>
#include <time.h>
#include <uacpi/acpi.h>
#include <uacpi/status.h>
#include <uacpi/tables.h>
#include <uacpi/uacpi.h>

#define RTC_CMOS_ADDR 0x70
#define RTC_CMOS_DATA 0x71

static uint8_t rtc_century;
#define RTC_SEC        0x00
#define RTC_SEC_ALARM  0x01
#define RTC_MIN        0x02
#define RTC_MIN_ALARM  0x03
#define RTC_HOUR       0x04
#define RTC_HOUR_ALARM 0x05
#define RTC_WEEK_DAY   0x06
#define RTC_DAY        0x07
#define RTC_MONTH      0x08
#define RTC_YEAR       0x09
#define RTC_REG_A      0x0A
#define RTC_REG_B      0x0B
#define RTC_REG_C      0x0C
#define RTC_REG_D      0x0D

#define RTC_REG_A_UIP (1 << 7)

#define RTC_REG_B_HOURFMT  (1 << 1)
#define RTC_REG_B_DATAMODE (1 << 2)

static uint8_t rtc_read (uint8_t addr) {
  outb (RTC_CMOS_ADDR, RTC_REG_A);
  while (inb (RTC_CMOS_DATA) & RTC_REG_A_UIP)
    ;
  outb (RTC_CMOS_ADDR, addr);
  return inb (RTC_CMOS_DATA);
}

static void rtc_write (uint8_t addr, uint8_t value) {
  outb (RTC_CMOS_ADDR, addr);
  outb (RTC_CMOS_DATA, value);
}

static uint8_t rtc_bcd_to_bin (uint8_t value) { return (value & 0xF) + (value >> 4) * 10; }

static uint8_t rtc_bin_to_bcd (uint8_t value) { return ((value / 10) << 4) + (value % 10); }

void rtc_init (void) {
  struct limine_hhdm_response* hhdm = limine_hhdm_request.response;

  struct uacpi_table fadt_table;
  uacpi_status status = uacpi_table_find_by_signature (ACPI_FADT_SIGNATURE, &fadt_table);
  if (status != UACPI_STATUS_OK) {
    DEBUG ("Could not find FADT table!\n");
    spin ();
  }

  struct acpi_fadt* fadt = (struct acpi_fadt*)fadt_table.virt_addr;

  rtc_century = fadt->century;
}

void rtc_date_time (struct date_time* date_time) {
  if (rtc_read (RTC_REG_A) & RTC_REG_A_UIP)
    stall_ms (1);

  uint8_t sec = rtc_read (RTC_SEC);
  uint8_t min = rtc_read (RTC_MIN);
  uint8_t hour = rtc_read (RTC_HOUR);
  uint8_t weekday = rtc_read (RTC_WEEK_DAY);
  uint8_t day = rtc_read (RTC_DAY);
  uint8_t month = rtc_read (RTC_MONTH);
  uint8_t year = rtc_read (RTC_YEAR);
  uint8_t century = rtc_century != 0 ? rtc_read (rtc_century) : 0;

  uint8_t b = rtc_read (RTC_REG_B);

  /* BCD */
  if ((~b) & RTC_REG_B_DATAMODE) {
    sec = rtc_bcd_to_bin (sec);
    min = rtc_bcd_to_bin (min);
    hour = rtc_bcd_to_bin (hour);
    day = rtc_bcd_to_bin (day);
    month = rtc_bcd_to_bin (month);
    year = rtc_bcd_to_bin (year);
    if (rtc_century != 0)
      century = rtc_bcd_to_bin (century);
  }

  weekday--;

  int full_year;
  if (rtc_century != 0)
    full_year = (century * 100) + year;
  else
    full_year = (year < 80) ? (2000 + year) : (1900 + year);

  date_time->sec = sec;
  date_time->min = min;
  date_time->hour = hour;
  date_time->day = day;
  date_time->weekday = weekday;
  date_time->month = month;
  date_time->year = full_year;
}