#include "unix_timestamp.h"

#define LOG_TAG             "[Unix-time]"
#define LOG_ERROR_ENABLE
#define LOG_DEBUG_ENABLE
/* #define LOG_INFO_ENABLE */
/* #define LOG_DUMP_ENABLE */
#define LOG_CLI_ENABLE
#include "debug.h"

#define SECOND                      1UL
#define MINU_SECONDS                (60 * SECOND)
#define HOUR_SECONDS                (60 * MINU_SECONDS)
#define DAY_SECONDS                 (24 * HOUR_SECONDS)
#define HOUR_MINUTES                60
#define TIME_UNIT                   60
#define UTC_BEIJING_OFFSET_SECONDS  (8 * HOUR_SECONDS)

#define UNIX_EPOCH_YEAR             1970
#define CLOSEST_FAKE_LEAP_YEAR      2102 // 2100 is nonleap year
#define UNIX_EPOCH_YEAR_WEEKDAY     4 // Thursday

#define NONLEAP_YEAR_DAYS           365
#define LEAP_YEAR_DAYS              366
#define EVERY_4YEARS_DAYS           (NONLEAP_YEAR_DAYS * 3 + LEAP_YEAR_DAYS)
#define DAYS_OF_WEEK                7

static bool get_is_leap_year(u16 year)
{
    if (((year % 4) == 0) && ((year % 100) != 0)) {
        return 1;
    } else if ((year % 400) == 0) {
        return 1;
    }

    return 0;
}

struct UTC_TIME unix32_to_UTC(u32 unix_time)
{
    log_info("unix_time=%u", unix_time);

    u8 days_per_month[12] = {
        /*
        1   2   3   4   5   6   7   8   9   10  11  12
        */
        31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
    };
    struct UTC_TIME utc = {0};
    u32 pass_days, pass_days_cnt, pass_days_cnt_next;
    u8 pass_4years_cnt;
    u16 basic_4multiple_year;
    u16 CurrentYear_PassDays, CurrentDay_PassMinutes;
    u32 CurrentDay_PassSeconds;

    pass_days = unix_time / DAY_SECONDS; // passed days since UNIX_EPOCH_YEAR
    pass_4years_cnt = pass_days / EVERY_4YEARS_DAYS; // passed how many 4 years
    basic_4multiple_year = (pass_4years_cnt * 4) + UNIX_EPOCH_YEAR; // next 4 year basic, base on UNIX_EPOCH_YEAR
    pass_days_cnt = pass_4years_cnt * EVERY_4YEARS_DAYS; // passed day of pass_4years_cnt
    if (basic_4multiple_year >= CLOSEST_FAKE_LEAP_YEAR) {
        pass_days_cnt--;
    }
    log_info("basic_4multiple_year=%d", basic_4multiple_year);

    //< get year
    for (u16 i = basic_4multiple_year; ; i++) {
        pass_days_cnt_next = get_is_leap_year(i) ? \
                             (pass_days_cnt + LEAP_YEAR_DAYS) : (pass_days_cnt + NONLEAP_YEAR_DAYS);
        if (pass_days_cnt_next > pass_days) {
            utc.year = i;
            break;
        }
        pass_days_cnt = pass_days_cnt_next;
    }

    //< get month
    CurrentYear_PassDays = pass_days - pass_days_cnt;
    pass_days_cnt = pass_days_cnt_next = 0;
    log_info("CurrentYear_PassDays=%d", CurrentYear_PassDays);
    if (get_is_leap_year(utc.year)) {
        days_per_month[1]++; // leap month of February is 29 days
    }
    for (u8 i = 0; i < ARRAY_SIZE(days_per_month); i++) {
        pass_days_cnt_next += days_per_month[i];
        if (pass_days_cnt_next > CurrentYear_PassDays) {
            utc.month = i + 1;
            break;
        }
        pass_days_cnt = pass_days_cnt_next;
    }

    //< get day
    utc.day = CurrentYear_PassDays - pass_days_cnt + 1;

    //< get hour:minute:second
    CurrentDay_PassSeconds = unix_time - (pass_days * DAY_SECONDS);
    CurrentDay_PassMinutes = CurrentDay_PassSeconds / MINU_SECONDS;
    utc.hour = CurrentDay_PassMinutes / HOUR_MINUTES;
    utc.minute = CurrentDay_PassMinutes % TIME_UNIT;
    utc.second = CurrentDay_PassSeconds % TIME_UNIT;

    //< get weekday
    utc.weekday = (pass_days + UNIX_EPOCH_YEAR_WEEKDAY) % DAYS_OF_WEEK;

    log_info("unix32_to_UTC: %d/%d/%d %02d:%02d:%02d, weekday %d",
             utc.year, utc.month, utc.day,
             utc.hour, utc.minute, utc.second,
             utc.weekday);

    return utc;
}

struct UTC_TIME unix32_to_UTC_beijing(u32 unix_time)
{
    return unix32_to_UTC(unix_time + UTC_BEIJING_OFFSET_SECONDS);
}