#include "global.h"
#include "RTC_api.h"
#include "RTC_convert.h"

static s32 sDayOfYear[12] = {
      0, // Jan
     31, // Feb
     59, // Mar
     90, // Apr
    120, // May
    151, // Jun
    181, // Jul
    212, // Aug
    243, // Sep
    273, // Oct
    304, // Nov
    334, // Dec
};

static inline BOOL RTCi_IsLeapYear(u32 year)
{
    return !((year & 0x03));
}

s32 RTC_ConvertDateToDay(const RTCDate * date)
{
    if (date->year >= 100
     || date->month < 1
     || date->month > 12
     || date->day < 1
     || date->day > 31
     || date->week >= RTC_WEEK_MAX
     || date->month < 1   // can't be
     || date->month > 12  // too sure
    )
        return -1;
    s32 dayNum = (s32)(date->day - 1);
    dayNum += sDayOfYear[date->month - 1];
    if (date->month >= 3 && RTCi_IsLeapYear(date->year))
        dayNum++;
    dayNum += date->year * 365;
    dayNum += (date->year + 3) / 4;
    return dayNum;
}

s32 RTCi_ConvertTimeToSecond(const RTCTime * time)
{
    return (s32)((time->hour * 60 + time->minute) * 60 + time->second);
}

s64 RTC_ConvertDateTimeToSecond(const RTCDate * date, const RTCTime * time)
{
    s32 day = RTC_ConvertDateToDay(date);
    if (day == -1)
        return -1;
    s32 second = RTCi_ConvertTimeToSecond(time);
    if (second == -1)
        return -1;
    return ((s64)day) * (60 * 60 * 24) + second;
}

void RTC_ConvertDayToDate(RTCDate * date, s32 day)
{
    u32 year;
    s32 month;

    if (day < 0)
    {
        day = 0;
    }
    if (day > 36524) // max number of days that can be recorded
    {
        day = 36524;
    }
    date->week = (RTCWeek)((day + 6) % 7);
    for (year = 0; year < 99; year++)
    {
        s32 prev = day;
        day -= (RTCi_IsLeapYear(year)) ? 366 : 365;
        if (day < 0)
        {
            day = prev;
            break;
        }
    }
    if (day > 365)
    {
        day = 365;
    }
    date->year = year;
    if (RTCi_IsLeapYear(year))
    {
        if (day < 31 + 29)
        {
            if (day < 31)
            {
                month = 1;
            }
            else
            {
                month = 2;
                day -= 31;
            }
            date->month = (u32)month;
            date->day = (u32)(day + 1);
            return;
        }
        else
        {
            day--;
        }
    }
    for (month = 11; month >= 0; month--)
    {
        if (day >= sDayOfYear[month])
        {
            date->month = (u32)(month + 1);
            date->day = (u32)(day - sDayOfYear[month] + 1);
            return;
        }
    }
    // Internal Error.
}

void RTCi_ConvertSecondToTime(RTCTime * time, s32 sec)
{
    if (sec < 0)
        sec = 0;
    if (sec > 86399)
        sec = 86399;
    time->second = (u32)(sec % 60);
    sec /= 60;
    time->minute = (u32)(sec % 60);
    sec /= 60;
    time->hour = (u32)sec;
}

void RTC_ConvertSecondToDateTime(RTCDate * date, RTCTime * time, s64 sec)
{
    if (sec < 0)
        sec = 0;
    else if (sec > 3155759999)
        sec = 3155759999;
    RTCi_ConvertSecondToTime(time, (s32)(sec % 86400));
    RTC_ConvertDayToDate(date, (s32)(sec / 86400));
}

RTCWeek RTC_GetDayOfWeek(RTCDate * date)
{
    int cent;
    int year = (int)(2000 + date->year);
    int month = (int)date->month;
    int day = (int)date->day;

    month -= 2;
    if (month < 1)
    {
        month += 12;
        --year;
    }
    cent = year / 100;
    year %= 100;
    return (RTCWeek)(((26 * month - 2) / 10 + day + year + year / 4 + cent / 4 + 5 * cent) % 7);
}