// Copyright 2015 Citra Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.

#include <chrono>
#include <cstring>
#include <ctime>

#include "core/core_timing.h"
#include "core/hle/shared_page.h"

////////////////////////////////////////////////////////////////////////////////////////////////////

namespace SharedPage {

SharedPageDef shared_page;

static int update_time_event;

/// Gets system time in 3DS format. The epoch is Jan 1900, and the unit is millisecond.
static u64 GetSystemTime() {
    auto now = std::chrono::system_clock::now();

    // 3DS system does't allow user to set a time before Jan 1 2000,
    // so we use it as an auxiliary epoch to calculate the console time.
    std::tm epoch_tm;
    epoch_tm.tm_sec = 0;
    epoch_tm.tm_min = 0;
    epoch_tm.tm_hour = 0;
    epoch_tm.tm_mday = 1;
    epoch_tm.tm_mon = 0;
    epoch_tm.tm_year = 100;
    epoch_tm.tm_isdst = 0;
    auto epoch = std::chrono::system_clock::from_time_t(std::mktime(&epoch_tm));

    // 3DS console time uses Jan 1 1900 as internal epoch,
    // so we use the milliseconds between 1900 and 2000 as base console time
    u64 console_time = 3155673600000ULL;

    // Only when system time is after 2000, we set it as 3DS system time
    if (now > epoch) {
        console_time += std::chrono::duration_cast<std::chrono::milliseconds>(now - epoch).count();
    }

    // If the system time is in daylight saving, we give an additional hour to console time
    std::time_t now_time_t = std::chrono::system_clock::to_time_t(now);
    std::tm* now_tm = std::localtime(&now_time_t);
    if (now_tm && now_tm->tm_isdst > 0)
        console_time += 60 * 60 * 1000;

    return console_time;
}

static void UpdateTimeCallback(u64 userdata, int cycles_late) {
    DateTime& date_time = shared_page.date_time_counter % 2 ?
        shared_page.date_time_0 : shared_page.date_time_1;

    date_time.date_time = GetSystemTime();
    date_time.update_tick = CoreTiming::GetTicks();
    date_time.tick_to_second_coefficient = g_clock_rate_arm11;
    date_time.tick_offset = 0;

    ++shared_page.date_time_counter;

    // system time is updated hourly
    CoreTiming::ScheduleEvent(msToCycles(60 * 60 * 1000) - cycles_late, update_time_event);
}

void Init() {
    std::memset(&shared_page, 0, sizeof(shared_page));

    shared_page.running_hw = 0x1; // product

    // Some games wait until this value becomes 0x1, before asking running_hw
    shared_page.unknown_value = 0x1;

    update_time_event = CoreTiming::RegisterEvent("SharedPage::UpdateTimeCallback", UpdateTimeCallback);
    CoreTiming::ScheduleEvent(0, update_time_event);
}

} // namespace
