// SPDX-FileCopyrightText: Copyright 2022 yuzu Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later

#include <array>
#include <vector>

#include "audio_core/renderer/command/data_source/decode.h"
#include "audio_core/renderer/command/resample/resample.h"
#include "common/fixed_point.h"
#include "common/logging/log.h"
#include "common/scratch_buffer.h"
#include "core/memory.h"

namespace AudioCore::AudioRenderer {

constexpr u32 TempBufferSize = 0x3F00;
constexpr std::array<u8, 3> PitchBySrcQuality = {4, 8, 4};

/**
 * Decode PCM data. Only s16 or f32 is supported.
 *
 * @tparam T         - Type to decode. Only s16 and f32 are supported.
 * @param memory     - Core memory for reading samples.
 * @param out_buffer - Output mix buffer to receive the samples.
 * @param req        - Information for how to decode.
 * @return Number of samples decoded.
 */
template <typename T>
static u32 DecodePcm(Core::Memory::Memory& memory, std::span<s16> out_buffer,
                     const DecodeArg& req) {
    constexpr s32 min{std::numeric_limits<s16>::min()};
    constexpr s32 max{std::numeric_limits<s16>::max()};

    if (req.buffer == 0 || req.buffer_size == 0) {
        return 0;
    }

    if (req.start_offset >= req.end_offset) {
        return 0;
    }

    auto samples_to_decode{
        std::min(req.samples_to_read, req.end_offset - req.start_offset - req.offset)};
    u32 channel_count{static_cast<u32>(req.channel_count)};

    switch (req.channel_count) {
    default: {
        const VAddr source{req.buffer +
                           (((req.start_offset + req.offset) * channel_count) * sizeof(T))};
        const u64 size{channel_count * samples_to_decode};

        Core::Memory::CpuGuestMemory<T, Core::Memory::GuestMemoryFlags::UnsafeRead> samples(
            memory, source, size);
        if constexpr (std::is_floating_point_v<T>) {
            for (u32 i = 0; i < samples_to_decode; i++) {
                auto sample{static_cast<s32>(samples[i * channel_count + req.target_channel] *
                                             std::numeric_limits<s16>::max())};
                out_buffer[i] = static_cast<s16>(std::clamp(sample, min, max));
            }
        } else {
            for (u32 i = 0; i < samples_to_decode; i++) {
                out_buffer[i] = samples[i * channel_count + req.target_channel];
            }
        }
    } break;

    case 1:
        if (req.target_channel != 0) {
            LOG_ERROR(Service_Audio, "Invalid target channel, expected 0, got {}",
                      req.target_channel);
            return 0;
        }

        const VAddr source{req.buffer + ((req.start_offset + req.offset) * sizeof(T))};
        Core::Memory::CpuGuestMemory<T, Core::Memory::GuestMemoryFlags::UnsafeRead> samples(
            memory, source, samples_to_decode);

        if constexpr (std::is_floating_point_v<T>) {
            for (u32 i = 0; i < samples_to_decode; i++) {
                auto sample{static_cast<s32>(samples[i * channel_count + req.target_channel] *
                                             std::numeric_limits<s16>::max())};
                out_buffer[i] = static_cast<s16>(std::clamp(sample, min, max));
            }
        } else {
            std::memcpy(out_buffer.data(), samples.data(), samples_to_decode * sizeof(s16));
        }
        break;
    }

    return samples_to_decode;
}

/**
 * Decode ADPCM data.
 *
 * @param memory     - Core memory for reading samples.
 * @param out_buffer - Output mix buffer to receive the samples.
 * @param req        - Information for how to decode.
 * @return Number of samples decoded.
 */
static u32 DecodeAdpcm(Core::Memory::Memory& memory, std::span<s16> out_buffer,
                       const DecodeArg& req) {
    constexpr u32 SamplesPerFrame{14};
    constexpr u32 NibblesPerFrame{16};

    if (req.buffer == 0 || req.buffer_size == 0) {
        return 0;
    }

    if (req.end_offset < req.start_offset) {
        return 0;
    }

    auto end{(req.end_offset % SamplesPerFrame) +
             NibblesPerFrame * (req.end_offset / SamplesPerFrame)};
    if (req.end_offset % SamplesPerFrame) {
        end += 3;
    } else {
        end += 1;
    }

    if (req.buffer_size < end / 2) {
        return 0;
    }

    auto samples_to_process{
        std::min(req.end_offset - req.start_offset - req.offset, req.samples_to_read)};

    auto samples_to_read{samples_to_process};
    auto start_pos{req.start_offset + req.offset};
    auto samples_remaining_in_frame{start_pos % SamplesPerFrame};
    auto position_in_frame{(start_pos / SamplesPerFrame) * NibblesPerFrame +
                           samples_remaining_in_frame};

    if (samples_remaining_in_frame) {
        position_in_frame += 2;
    }

    const auto size{std::max((samples_to_process / 8U) * SamplesPerFrame, 8U)};
    Core::Memory::CpuGuestMemory<u8, Core::Memory::GuestMemoryFlags::UnsafeRead> wavebuffer(
        memory, req.buffer + position_in_frame / 2, size);

    auto context{req.adpcm_context};
    auto header{context->header};
    u8 coeff_index{static_cast<u8>((header >> 4U) & 0xFU)};
    u8 scale{static_cast<u8>(header & 0xFU)};
    s32 coeff0{req.coefficients[coeff_index * 2 + 0]};
    s32 coeff1{req.coefficients[coeff_index * 2 + 1]};

    auto yn0{context->yn0};
    auto yn1{context->yn1};

    static constexpr std::array<s32, 16> Steps{
        0, 1, 2, 3, 4, 5, 6, 7, -8, -7, -6, -5, -4, -3, -2, -1,
    };

    const auto decode_sample = [&](const s32 code) -> s16 {
        const auto xn = code * (1 << scale);
        const auto prediction = coeff0 * yn0 + coeff1 * yn1;
        const auto sample = ((xn << 11) + 0x400 + prediction) >> 11;
        const auto saturated = std::clamp<s32>(sample, -0x8000, 0x7FFF);
        yn1 = yn0;
        yn0 = static_cast<s16>(saturated);
        return yn0;
    };

    u32 read_index{0};
    u32 write_index{0};

    while (samples_to_read > 0) {
        // Are we at a new frame?
        if ((position_in_frame % NibblesPerFrame) == 0) {
            header = wavebuffer[read_index++];
            coeff_index = (header >> 4) & 0xF;
            scale = header & 0xF;
            coeff0 = req.coefficients[coeff_index * 2 + 0];
            coeff1 = req.coefficients[coeff_index * 2 + 1];
            position_in_frame += 2;

            // Can we consume all of this frame's samples?
            if (samples_to_read >= SamplesPerFrame) {
                // Can grab all samples until the next header
                for (u32 i = 0; i < SamplesPerFrame / 2; i++) {
                    auto code0{Steps[(wavebuffer[read_index] >> 4) & 0xF]};
                    auto code1{Steps[wavebuffer[read_index] & 0xF]};
                    read_index++;

                    out_buffer[write_index++] = decode_sample(code0);
                    out_buffer[write_index++] = decode_sample(code1);
                }

                position_in_frame += SamplesPerFrame;
                samples_to_read -= SamplesPerFrame;
                continue;
            }
        }

        // Decode a single sample
        auto code{wavebuffer[read_index]};
        if (position_in_frame & 1) {
            code &= 0xF;
            read_index++;
        } else {
            code >>= 4;
        }

        out_buffer[write_index++] = decode_sample(Steps[code]);

        position_in_frame++;
        samples_to_read--;
    }

    context->header = header;
    context->yn0 = yn0;
    context->yn1 = yn1;

    return samples_to_process;
}

/**
 * Decode implementation.
 * Decode wavebuffers according to the given args.
 *
 * @param memory - Core memory to read data from.
 * @param args   - The wavebuffer data, and information for how to decode it.
 */
void DecodeFromWaveBuffers(Core::Memory::Memory& memory, const DecodeFromWaveBuffersArgs& args) {
    auto& voice_state{*args.voice_state};
    auto remaining_sample_count{args.sample_count};
    auto fraction{voice_state.fraction};

    const auto sample_rate_ratio{
        (Common::FixedPoint<49, 15>(args.source_sample_rate) / args.target_sample_rate) *
        args.pitch};
    const auto size_required{fraction + remaining_sample_count * sample_rate_ratio};

    if (size_required < 0) {
        return;
    }

    auto pitch{PitchBySrcQuality[static_cast<u32>(args.src_quality)]};
    if (static_cast<u32>(pitch + size_required.to_int_floor()) > TempBufferSize) {
        return;
    }

    auto max_remaining_sample_count{
        ((Common::FixedPoint<17, 15>(TempBufferSize) - fraction) / sample_rate_ratio)
            .to_uint_floor()};
    max_remaining_sample_count = std::min(max_remaining_sample_count, remaining_sample_count);

    auto wavebuffers_consumed{voice_state.wave_buffers_consumed};
    auto wavebuffer_index{voice_state.wave_buffer_index};
    auto played_sample_count{voice_state.played_sample_count};

    bool is_buffer_starved{false};
    u32 offset{voice_state.offset};

    auto output_buffer{args.output};
    std::array<s16, TempBufferSize> temp_buffer{};

    while (remaining_sample_count > 0) {
        const auto samples_to_write{std::min(remaining_sample_count, max_remaining_sample_count)};
        const auto samples_to_read{
            (fraction + samples_to_write * sample_rate_ratio).to_uint_floor()};

        u32 temp_buffer_pos{0};

        if (!args.IsVoicePitchAndSrcSkippedSupported) {
            for (u32 i = 0; i < pitch; i++) {
                temp_buffer[i] = voice_state.sample_history[i];
            }
            temp_buffer_pos = pitch;
        }

        u32 samples_read{0};
        while (samples_read < samples_to_read) {
            if (wavebuffer_index >= MaxWaveBuffers) {
                LOG_ERROR(Service_Audio, "Invalid wavebuffer index! {}", wavebuffer_index);
                wavebuffer_index = 0;
                voice_state.wave_buffer_valid.fill(false);
                wavebuffers_consumed = MaxWaveBuffers;
            }

            if (!voice_state.wave_buffer_valid[wavebuffer_index]) {
                is_buffer_starved = true;
                break;
            }

            auto& wavebuffer{args.wave_buffers[wavebuffer_index]};

            if (offset == 0 && args.sample_format == SampleFormat::Adpcm &&
                wavebuffer.context != 0) {
                memory.ReadBlockUnsafe(wavebuffer.context, &voice_state.adpcm_context,
                                       wavebuffer.context_size);
            }

            auto start_offset{wavebuffer.start_offset};
            auto end_offset{wavebuffer.end_offset};

            if (wavebuffer.loop && voice_state.loop_count > 0 &&
                wavebuffer.loop_start_offset != 0 && wavebuffer.loop_end_offset != 0 &&
                wavebuffer.loop_start_offset <= wavebuffer.loop_end_offset) {
                start_offset = wavebuffer.loop_start_offset;
                end_offset = wavebuffer.loop_end_offset;
            }

            DecodeArg decode_arg{.buffer{wavebuffer.buffer},
                                 .buffer_size{wavebuffer.buffer_size},
                                 .start_offset{start_offset},
                                 .end_offset{end_offset},
                                 .channel_count{args.channel_count},
                                 .coefficients{},
                                 .adpcm_context{nullptr},
                                 .target_channel{args.channel},
                                 .offset{offset},
                                 .samples_to_read{samples_to_read - samples_read}};

            s32 samples_decoded{0};

            switch (args.sample_format) {
            case SampleFormat::PcmInt16:
                samples_decoded = DecodePcm<s16>(
                    memory, {&temp_buffer[temp_buffer_pos], TempBufferSize - temp_buffer_pos},
                    decode_arg);
                break;

            case SampleFormat::PcmFloat:
                samples_decoded = DecodePcm<f32>(
                    memory, {&temp_buffer[temp_buffer_pos], TempBufferSize - temp_buffer_pos},
                    decode_arg);
                break;

            case SampleFormat::Adpcm: {
                decode_arg.adpcm_context = &voice_state.adpcm_context;
                memory.ReadBlockUnsafe(args.data_address, &decode_arg.coefficients, args.data_size);
                samples_decoded = DecodeAdpcm(
                    memory, {&temp_buffer[temp_buffer_pos], TempBufferSize - temp_buffer_pos},
                    decode_arg);
            } break;

            default:
                LOG_ERROR(Service_Audio, "Invalid sample format to decode {}",
                          static_cast<u32>(args.sample_format));
                samples_decoded = 0;
                break;
            }

            played_sample_count += samples_decoded;
            samples_read += samples_decoded;
            temp_buffer_pos += samples_decoded;
            offset += samples_decoded;

            if (samples_decoded == 0 || offset >= end_offset - start_offset) {
                offset = 0;
                if (!wavebuffer.loop) {
                    voice_state.wave_buffer_valid[wavebuffer_index] = false;
                    voice_state.loop_count = 0;

                    if (wavebuffer.stream_ended) {
                        played_sample_count = 0;
                    }

                    wavebuffer_index = (wavebuffer_index + 1) % MaxWaveBuffers;
                    wavebuffers_consumed++;
                } else {
                    voice_state.loop_count++;
                    if (wavebuffer.loop_count > 0 &&
                        (voice_state.loop_count > wavebuffer.loop_count || samples_decoded == 0)) {
                        voice_state.wave_buffer_valid[wavebuffer_index] = false;
                        voice_state.loop_count = 0;

                        if (wavebuffer.stream_ended) {
                            played_sample_count = 0;
                        }

                        wavebuffer_index = (wavebuffer_index + 1) % MaxWaveBuffers;
                        wavebuffers_consumed++;
                    }

                    if (samples_decoded == 0) {
                        is_buffer_starved = true;
                        break;
                    }

                    if (args.IsVoicePlayedSampleCountResetAtLoopPointSupported) {
                        played_sample_count = 0;
                    }
                }
            }
        }

        if (args.IsVoicePitchAndSrcSkippedSupported) {
            if (samples_read > output_buffer.size()) {
                LOG_ERROR(Service_Audio, "Attempting to write past the end of output buffer!");
            }
            for (u32 i = 0; i < samples_read; i++) {
                output_buffer[i] = temp_buffer[i];
            }
        } else {
            std::memset(&temp_buffer[temp_buffer_pos], 0,
                        (samples_to_read - samples_read) * sizeof(s16));

            Resample(output_buffer, temp_buffer, sample_rate_ratio, fraction, samples_to_write,
                     args.src_quality);

            std::memcpy(voice_state.sample_history.data(), &temp_buffer[samples_to_read],
                        pitch * sizeof(s16));
        }

        remaining_sample_count -= samples_to_write;
        if (remaining_sample_count != 0 && is_buffer_starved) {
            LOG_ERROR(Service_Audio, "Samples remaining but buffer is starving??");
            break;
        }

        output_buffer = output_buffer.subspan(samples_to_write);
    }

    voice_state.wave_buffers_consumed = wavebuffers_consumed;
    voice_state.played_sample_count = played_sample_count;
    voice_state.wave_buffer_index = wavebuffer_index;
    voice_state.offset = offset;
    voice_state.fraction = fraction;
}

} // namespace AudioCore::AudioRenderer
