// Copyright 2020 yuzu Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.

#include "common/wall_clock.h"

#ifdef ARCHITECTURE_x86_64
#include "common/x64/cpu_detect.h"
#include "common/x64/native_clock.h"
#endif

namespace Common {

using base_timer = std::chrono::steady_clock;
using base_time_point = std::chrono::time_point<base_timer>;

class StandardWallClock final : public WallClock {
public:
    explicit StandardWallClock(u64 emulated_cpu_frequency_, u64 emulated_clock_frequency_)
        : WallClock(emulated_cpu_frequency_, emulated_clock_frequency_, false) {
        start_time = base_timer::now();
    }

    std::chrono::nanoseconds GetTimeNS() override {
        base_time_point current = base_timer::now();
        auto elapsed = current - start_time;
        return std::chrono::duration_cast<std::chrono::nanoseconds>(elapsed);
    }

    std::chrono::microseconds GetTimeUS() override {
        base_time_point current = base_timer::now();
        auto elapsed = current - start_time;
        return std::chrono::duration_cast<std::chrono::microseconds>(elapsed);
    }

    std::chrono::milliseconds GetTimeMS() override {
        base_time_point current = base_timer::now();
        auto elapsed = current - start_time;
        return std::chrono::duration_cast<std::chrono::milliseconds>(elapsed);
    }

    u64 GetClockCycles() override {
        return GetTimeNS().count() * (emulated_clock_frequency / 1000) / 1000000;
    }

    u64 GetCPUCycles() override {
        return GetTimeNS().count() * (emulated_cpu_frequency / 1000) / 1000000;
    }

    void Pause([[maybe_unused]] bool is_paused) override {
        // Do nothing in this clock type.
    }

private:
    base_time_point start_time;
};

#ifdef ARCHITECTURE_x86_64

std::unique_ptr<WallClock> CreateBestMatchingClock(u32 emulated_cpu_frequency,
                                                   u32 emulated_clock_frequency) {
    const auto& caps = GetCPUCaps();
    u64 rtsc_frequency = 0;
    if (caps.invariant_tsc) {
        rtsc_frequency = EstimateRDTSCFrequency();
    }
    if (rtsc_frequency == 0) {
        return std::make_unique<StandardWallClock>(emulated_cpu_frequency,
                                                   emulated_clock_frequency);
    } else {
        return std::make_unique<X64::NativeClock>(emulated_cpu_frequency, emulated_clock_frequency,
                                                  rtsc_frequency);
    }
}

#else

std::unique_ptr<WallClock> CreateBestMatchingClock(u32 emulated_cpu_frequency,
                                                   u32 emulated_clock_frequency) {
    return std::make_unique<StandardWallClock>(emulated_cpu_frequency, emulated_clock_frequency);
}

#endif

} // namespace Common
