#include <stdint.h>
#include <stdbool.h>
#include <stddef.h>
#include "common_utils/datetime.h"

const char *DT_WKDAY_NAMES[] = {
    [MONDAY] = "Mon",
    [TUESDAY] = "Tue",
    [WEDNESDAY] = "Wed",
    [THURSDAY] = "Thu",
    [FRIDAY] = "Fri",
    [SATURDAY] = "Sat",
    [SUNDAY] = "Sun"
};

const char *DT_WKDAY_NAMES_FULL[] = {
    [MONDAY] = "Monday",
    [TUESDAY] = "Tuesday",
    [WEDNESDAY] = "Wednesday",
    [THURSDAY] = "Thursday",
    [FRIDAY] = "Friday",
    [SATURDAY] = "Saturday",
    [SUNDAY] = "Sunday"
};

const char *DT_MONTH_NAMES[] = {
    [JANUARY] = "Jan",
    [FEBRUARY] = "Feb",
    [MARCH] = "Mar",
    [APRIL] = "Apr",
    [MAY] = "May",
    [JUNE] = "Jun",
    [JULY] = "Jul",
    [AUGUST] = "Aug",
    [SEPTEMBER] = "Sep",
    [OCTOBER] = "Oct",
    [NOVEMBER] = "Nov",
    [DECEMBER] = "Dec"
};

const char *DT_MONTH_NAMES_FULL[] = {
    [JANUARY] = "January",
    [FEBRUARY] = "February",
    [MARCH] = "March",
    [APRIL] = "April",
    [MAY] = "May",
    [JUNE] = "June",
    [JULY] = "July",
    [AUGUST] = "August",
    [SEPTEMBER] = "September",
    [OCTOBER] = "October",
    [NOVEMBER] = "November",
    [DECEMBER] = "December"
};

static const uint16_t MONTH_LENGTHS[] = { /* 1-based, normal year */
    [JANUARY]=31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
};
_Static_assert(sizeof(MONTH_LENGTHS) / sizeof(uint16_t) == 13, "Months array length");

static const uint16_t MONTH_YEARDAYS[] = { /* 1-based */
    [JANUARY]=0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 // // days until 1st of month
};
_Static_assert(sizeof(MONTH_YEARDAYS) / sizeof(uint16_t) == 13, "Months array length");

_Static_assert(MONDAY < SUNDAY, "Weekday ordering");

bool datetime_is_valid(const datetime_t *dt)
{
    if (dt == NULL) return false;

    // check month first to avoid out-of-bounds read from the MONTH_LENGTHS table
    if (!(dt->month >= JANUARY && dt->month <= DECEMBER)) return false;

    int monthlen = MONTH_LENGTHS[dt->month];
    if (dt->month == FEBRUARY && is_leap_year(dt->year)) {
        monthlen = 29;
    }

    return dt->sec < 60 &&
           dt->min < 60 &&
           dt->hour < 24 &&
           dt->wkday >= MONDAY &&
           dt->wkday <= SUNDAY &&
           dt->year >= DT_START_YEAR &&
           dt->year <= DT_END_YEAR &&
           dt->day >= 1 &&
           dt->day <= monthlen;
}

bool datetime_set_weekday(datetime_t *dt)
{
    dt->wkday = MONDAY; // prevent the validator func erroring out on invalid weekday
    if (!datetime_is_valid(dt)) return false;
    dt->wkday = date_weekday(dt->year, dt->month, dt->day);
    return true;
}

enum weekday date_weekday(uint16_t year, enum month month, uint8_t day)
{
    uint16_t days = (DT_START_WKDAY - MONDAY) + (year - DT_START_YEAR) * 365 + MONTH_YEARDAYS[month] + (day - 1);

    for (uint16_t i = DT_START_YEAR; i <= year; i++) {
        if (is_leap_year(i) && (i < year || month > FEBRUARY)) days++;
    }

    return MONDAY + days % 7;
}