// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later

#include <array>
#include <atomic>
#include <memory>
#include <span>
#include <vector>

#include "audio_core/audio_core.h"
#include "audio_core/common/common.h"
#include "audio_core/sink/sink_stream.h"
#include "common/common_types.h"
#include "common/fixed_point.h"
#include "common/settings.h"
#include "core/core.h"
#include "core/core_timing.h"

namespace AudioCore::Sink {

void SinkStream::AppendBuffer(SinkBuffer& buffer, std::span<s16> samples) {
    if (type == StreamType::In) {
        queue.enqueue(buffer);
        queued_buffers++;
        return;
    }

    constexpr s32 min{std::numeric_limits<s16>::min()};
    constexpr s32 max{std::numeric_limits<s16>::max()};

    auto yuzu_volume{Settings::Volume()};
    if (yuzu_volume > 1.0f) {
        yuzu_volume = 0.6f + 20 * std::log10(yuzu_volume);
    }
    auto volume{system_volume * device_volume * yuzu_volume};

    if (system_channels == 6 && device_channels == 2) {
        // We're given 6 channels, but our device only outputs 2, so downmix.
        static constexpr std::array<f32, 4> down_mix_coeff{1.0f, 0.707f, 0.251f, 0.707f};

        for (u32 read_index = 0, write_index = 0; read_index < samples.size();
             read_index += system_channels, write_index += device_channels) {
            const auto left_sample{
                ((Common::FixedPoint<49, 15>(
                      samples[read_index + static_cast<u32>(Channels::FrontLeft)]) *
                      down_mix_coeff[0] +
                  samples[read_index + static_cast<u32>(Channels::Center)] * down_mix_coeff[1] +
                  samples[read_index + static_cast<u32>(Channels::LFE)] * down_mix_coeff[2] +
                  samples[read_index + static_cast<u32>(Channels::BackLeft)] * down_mix_coeff[3]) *
                 volume)
                    .to_int()};

            const auto right_sample{
                ((Common::FixedPoint<49, 15>(
                      samples[read_index + static_cast<u32>(Channels::FrontRight)]) *
                      down_mix_coeff[0] +
                  samples[read_index + static_cast<u32>(Channels::Center)] * down_mix_coeff[1] +
                  samples[read_index + static_cast<u32>(Channels::LFE)] * down_mix_coeff[2] +
                  samples[read_index + static_cast<u32>(Channels::BackRight)] * down_mix_coeff[3]) *
                 volume)
                    .to_int()};

            samples[write_index + static_cast<u32>(Channels::FrontLeft)] =
                static_cast<s16>(std::clamp(left_sample, min, max));
            samples[write_index + static_cast<u32>(Channels::FrontRight)] =
                static_cast<s16>(std::clamp(right_sample, min, max));
        }

        samples = samples.subspan(0, samples.size() / system_channels * device_channels);

    } else if (system_channels == 2 && device_channels == 6) {
        // We need moar samples! Not all games will provide 6 channel audio.
        // TODO: Implement some upmixing here. Currently just passthrough, with other
        // channels left as silence.
        auto new_size = samples.size() / system_channels * device_channels;
        tmp_samples.resize_destructive(new_size);

        for (u32 read_index = 0, write_index = 0; read_index < new_size;
             read_index += system_channels, write_index += device_channels) {
            const auto left_sample{static_cast<s16>(std::clamp(
                static_cast<s32>(
                    static_cast<f32>(samples[read_index + static_cast<u32>(Channels::FrontLeft)]) *
                    volume),
                min, max))};

            tmp_samples[write_index + static_cast<u32>(Channels::FrontLeft)] = left_sample;

            const auto right_sample{static_cast<s16>(std::clamp(
                static_cast<s32>(
                    static_cast<f32>(samples[read_index + static_cast<u32>(Channels::FrontRight)]) *
                    volume),
                min, max))};

            tmp_samples[write_index + static_cast<u32>(Channels::FrontRight)] = right_sample;
        }
        samples = std::span<s16>(tmp_samples);

    } else if (volume != 1.0f) {
        for (u32 i = 0; i < samples.size(); i++) {
            samples[i] = static_cast<s16>(
                std::clamp(static_cast<s32>(static_cast<f32>(samples[i]) * volume), min, max));
        }
    }

    samples_buffer.Push(samples);
    queue.enqueue(buffer);
    queued_buffers++;
}

std::vector<s16> SinkStream::ReleaseBuffer(u64 num_samples) {
    constexpr s32 min = std::numeric_limits<s16>::min();
    constexpr s32 max = std::numeric_limits<s16>::max();

    auto samples{samples_buffer.Pop(num_samples)};

    // TODO: Up-mix to 6 channels if the game expects it.
    // For audio input this is unlikely to ever be the case though.

    // Incoming mic volume seems to always be very quiet, so multiply by an additional 8 here.
    // TODO: Play with this and find something that works better.
    auto volume{system_volume * device_volume * 8};
    for (u32 i = 0; i < samples.size(); i++) {
        samples[i] = static_cast<s16>(
            std::clamp(static_cast<s32>(static_cast<f32>(samples[i]) * volume), min, max));
    }

    if (samples.size() < num_samples) {
        samples.resize(num_samples, 0);
    }
    return samples;
}

void SinkStream::ClearQueue() {
    samples_buffer.Pop();
    while (queue.pop()) {
    }
    queued_buffers = 0;
    playing_buffer = {};
    playing_buffer.consumed = true;
}

void SinkStream::ProcessAudioIn(std::span<const s16> input_buffer, std::size_t num_frames) {
    const std::size_t num_channels = GetDeviceChannels();
    const std::size_t frame_size = num_channels;
    const std::size_t frame_size_bytes = frame_size * sizeof(s16);
    size_t frames_written{0};

    // If we're paused or going to shut down, we don't want to consume buffers as coretiming is
    // paused and we'll desync, so just return.
    if (system.IsPaused() || system.IsShuttingDown()) {
        return;
    }

    while (frames_written < num_frames) {
        // If the playing buffer has been consumed or has no frames, we need a new one
        if (playing_buffer.consumed || playing_buffer.frames == 0) {
            if (!queue.try_dequeue(playing_buffer)) {
                // If no buffer was available we've underrun, just push the samples and
                // continue.
                samples_buffer.Push(&input_buffer[frames_written * frame_size],
                                    (num_frames - frames_written) * frame_size);
                frames_written = num_frames;
                continue;
            }
            // Successfully dequeued a new buffer.
            queued_buffers--;
        }

        // Get the minimum frames available between the currently playing buffer, and the
        // amount we have left to fill
        size_t frames_available{std::min<u64>(playing_buffer.frames - playing_buffer.frames_played,
                                              num_frames - frames_written)};

        samples_buffer.Push(&input_buffer[frames_written * frame_size],
                            frames_available * frame_size);

        frames_written += frames_available;
        playing_buffer.frames_played += frames_available;

        // If that's all the frames in the current buffer, add its samples and mark it as
        // consumed
        if (playing_buffer.frames_played >= playing_buffer.frames) {
            playing_buffer.consumed = true;
        }
    }

    std::memcpy(&last_frame[0], &input_buffer[(frames_written - 1) * frame_size], frame_size_bytes);
}

void SinkStream::ProcessAudioOutAndRender(std::span<s16> output_buffer, std::size_t num_frames) {
    const std::size_t num_channels = GetDeviceChannels();
    const std::size_t frame_size = num_channels;
    const std::size_t frame_size_bytes = frame_size * sizeof(s16);
    size_t frames_written{0};
    size_t actual_frames_written{0};

    // If we're paused or going to shut down, we don't want to consume buffers as coretiming is
    // paused and we'll desync, so just play silence.
    if (system.IsPaused() || system.IsShuttingDown()) {
        if (system.IsShuttingDown()) {
            release_cv.notify_one();
        }

        static constexpr std::array<s16, 6> silence{};
        for (size_t i = frames_written; i < num_frames; i++) {
            std::memcpy(&output_buffer[i * frame_size], &silence[0], frame_size_bytes);
        }
        return;
    }

    while (frames_written < num_frames) {
        // If the playing buffer has been consumed or has no frames, we need a new one
        if (playing_buffer.consumed || playing_buffer.frames == 0) {
            if (!queue.try_dequeue(playing_buffer)) {
                // If no buffer was available we've underrun, fill the remaining buffer with
                // the last written frame and continue.
                for (size_t i = frames_written; i < num_frames; i++) {
                    std::memcpy(&output_buffer[i * frame_size], &last_frame[0], frame_size_bytes);
                }
                frames_written = num_frames;
                continue;
            }
            // Successfully dequeued a new buffer.
            queued_buffers--;

            { std::unique_lock lk{release_mutex}; }

            release_cv.notify_one();
        }

        // Get the minimum frames available between the currently playing buffer, and the
        // amount we have left to fill
        size_t frames_available{std::min<u64>(playing_buffer.frames - playing_buffer.frames_played,
                                              num_frames - frames_written)};

        samples_buffer.Pop(&output_buffer[frames_written * frame_size],
                           frames_available * frame_size);

        frames_written += frames_available;
        actual_frames_written += frames_available;
        playing_buffer.frames_played += frames_available;

        // If that's all the frames in the current buffer, add its samples and mark it as
        // consumed
        if (playing_buffer.frames_played >= playing_buffer.frames) {
            playing_buffer.consumed = true;
        }
    }

    std::memcpy(&last_frame[0], &output_buffer[(frames_written - 1) * frame_size],
                frame_size_bytes);

    {
        std::scoped_lock lk{sample_count_lock};
        last_sample_count_update_time = system.CoreTiming().GetGlobalTimeNs();
        min_played_sample_count = max_played_sample_count;
        max_played_sample_count += actual_frames_written;
    }
}

u64 SinkStream::GetExpectedPlayedSampleCount() {
    std::scoped_lock lk{sample_count_lock};
    auto cur_time{system.CoreTiming().GetGlobalTimeNs()};
    auto time_delta{cur_time - last_sample_count_update_time};
    auto exp_played_sample_count{min_played_sample_count +
                                 (TargetSampleRate * time_delta) / std::chrono::seconds{1}};

    // Add 15ms of latency in sample reporting to allow for some leeway in scheduler timings
    return std::min<u64>(exp_played_sample_count, max_played_sample_count) + TargetSampleCount * 3;
}

void SinkStream::WaitFreeSpace(std::stop_token stop_token) {
    std::unique_lock lk{release_mutex};
    release_cv.wait_for(lk, std::chrono::milliseconds(5),
                        [this]() { return queued_buffers < max_queue_size; });
    if (queued_buffers > max_queue_size + 3) {
        Common::CondvarWait(release_cv, lk, stop_token,
                            [this] { return queued_buffers < max_queue_size; });
    }
}

} // namespace AudioCore::Sink