/*
    * Time.cpp
    * Copyright (c) 2025 Daniel Hammer
*/

#include "Time.hpp"
#include "Timer.hpp"
#include <Terminal/Terminal.hpp>
#include <CppLib/Stream.hpp>

using namespace Kt;

static int64_t g_bootEpoch = 0;
static int g_tzOffsetMinutes = 60; /* Default: UTC+1 (CET) until userspace overrides */

static bool IsLeapYear(int year) {
    return (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0);
}

static int DaysInMonth(int month, int year) {
    static const int days[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    if (month == 2 && IsLeapYear(year)) return 29;
    return days[month];
}

static int64_t DateToEpoch(int year, int month, int day, int hour, int minute, int second) {
    int64_t days = 0;
    for (int y = 1970; y < year; y++) {
        days += IsLeapYear(y) ? 366 : 365;
    }
    for (int m = 1; m < month; m++) {
        days += DaysInMonth(m, year);
    }
    days += day - 1;
    return days * 86400 + hour * 3600 + minute * 60 + second;
}

static Timekeeping::DateTime EpochToDate(int64_t epoch) {
    Timekeeping::DateTime dt = {};
    /* Before the first NTP sync on a board with no RTC the clock sits near
       the epoch, and a negative time zone pushes local time before it. */
    int64_t rem = epoch < 0 ? 0 : epoch;
    int year = 1970;
    while (true) {
        int64_t daysInYear = IsLeapYear(year) ? 366 : 365;
        if (rem < daysInYear * 86400) break;
        rem -= daysInYear * 86400;
        year++;
    }
    dt.Year = (uint16_t)year;

    int dayOfYear = (int)(rem / 86400);
    rem -= (int64_t)dayOfYear * 86400;

    int month = 1;
    while (month <= 12) {
        int dim = DaysInMonth(month, year);
        if (dayOfYear < dim) break;
        dayOfYear -= dim;
        month++;
    }
    dt.Month = (uint8_t)month;
    dt.Day = (uint8_t)(dayOfYear + 1);

    dt.Hour = (uint8_t)(rem / 3600);
    rem %= 3600;
    dt.Minute = (uint8_t)(rem / 60);
    dt.Second = (uint8_t)(rem % 60);
    return dt;
}

void Timekeeping::Init(uint16_t Year, uint8_t Month, uint8_t Day, uint8_t Hour, uint8_t Minute, uint8_t Second) {
    g_bootEpoch = DateToEpoch(Year, Month, Day, Hour, Minute, Second);

    int64_t absoluteOffset = g_tzOffsetMinutes;
    char sign = '+';
    if (absoluteOffset < 0) {
        sign = '-';
        absoluteOffset = -absoluteOffset;
    }

    int offH = (int)(absoluteOffset / 60);
    int offM = (int)(absoluteOffset % 60);
    auto log = Kt::KernelLogStream(INFO, "Timekeeping Service");
    log << "Time zone: UTC" << sign << offH;
    if (offM != 0)
        log << ":" << (offM < 10 ? "0" : "") << offM;
}

int64_t Timekeeping::GetUnixTimestamp() {
    return g_bootEpoch + (int64_t)(Timekeeping::GetMilliseconds() / 1000);
}

int64_t Timekeeping::DateToUnixTimestamp(int year, int month, int day,
                                         int hour, int minute, int second) {
    if (year < 1970 || month < 1 || month > 12 || day < 1 || day > 31) return 0;
    if (hour < 0 || hour > 23 || minute < 0 || minute > 59 || second < 0 || second > 60) return 0;
    return DateToEpoch(year, month, day, hour, minute, second);
}

bool Timekeeping::SetUnixTimestamp(int64_t unixSeconds) {
    if (unixSeconds < 0 || unixSeconds > 4102444799LL)
        return false;
    g_bootEpoch = unixSeconds - (int64_t)(Timekeeping::GetMilliseconds() / 1000);
    return true;
}

Timekeeping::DateTime Timekeeping::GetDateTime() {
    return EpochToDate(GetUnixTimestamp() + (int64_t)g_tzOffsetMinutes * 60);
}

void Timekeeping::SetTZOffset(int totalMinutes) {
    g_tzOffsetMinutes = totalMinutes;
}

int Timekeeping::GetTZOffset() {
    return g_tzOffsetMinutes;
}