#include <inttypes.h>
#include "util.h"

uint8_t frombcd(uint8_t x) {
  return _frombcd(x);
}

uint8_t month_length(uint8_t m, uint8_t leap) {
  uint8_t knuckle = m < 8 ? (m & 1) == 1 : (m & 1) == 0;
  return knuckle ? 31 : m != 2 ? 30 : leap ? 29 : 28;
}

uint8_t days_in_month_bcd(uint8_t year, uint8_t month) {
  uint8_t y = frombcd(year);//(year & 7) + ((year & 070)>>3) * 10;
  uint8_t m = frombcd(month);//(month & 7) + ((month & 070)>>3) * 10;
  uint8_t leap = y % 4 == 0; // non y2k1-compliant, but should be correct for the next 91 years or so :)

  uint8_t knuckle = m < 8 ? (m & 1) == 1 : (m & 1) == 0;
  return knuckle ? 0x31 : m != 2 ? 0x30 : leap ? 0x29 : 0x28;
}


uint8_t bcd_increment(uint8_t x) {
  x++;
  if ((x & 0x0f) >= 0x0a)
    x += 0x10 - 0x0a;
  if (x >= 0xa0)
    x = 0;
  return x;
}


uint8_t day_of_week(uint8_t y, uint8_t m, uint8_t d) {
  uint8_t leap = y % 4 == 0;
  uint16_t centurydays = 6 + y * 365 + (y + 3) / 4; // year 2000 started on Saturday
  for (; --m >= 1; ) {
    centurydays += month_length(m, leap);
  }

  centurydays += d - 1;

  return (centurydays % 7);
}

uint16_t tobcd16(uint16_t x) {
  uint16_t y;

  y  = x % 10;        x /= 10;
  y |= (x % 10) << 4;   x /= 10;
  y |= (x % 100) << 8;  x /= 10;
  y |= 0xf000;

  return y;
}