/*

 * Copyright (c) 2018-2022, the SerenityOS developers.

 *

 * SPDX-License-Identifier: BSD-2-Clause

 */

#pragma once

#include <AK/Error.h>

#include <AK/FixedArray.h>

#include <AK/NonnullOwnPtr.h>

#include <AK/NonnullRefPtr.h>

#include <AK/RefCounted.h>

#include <AK/RefPtr.h>

#include <AK/Span.h>

#include <AK/Stream.h>

#include <AK/StringView.h>

#include <AK/Try.h>

#include <LibAudio/GenericTypes.h>

#include <LibAudio/LoaderError.h>

#include <LibAudio/Metadata.h>

#include <LibAudio/Sample.h>

#include <LibAudio/SampleFormats.h>

namespace Audio {

// Experimentally determined to be a decent buffer size on i686:

// 4K (the default) is slightly worse, and 64K is much worse.

// At sufficiently large buffer sizes, the advantage of infrequent read() calls is outweighed by the memmove() overhead.

// There was no intensive fine-tuning done to determine this value, so improvements may definitely be possible.

constexpr size_t const loader_buffer_size = 8 * KiB;

// Two seek points should ideally not be farther apart than this.

// This variable is a heuristic for seek table-constructing loaders.

constexpr u64 const maximum_seekpoint_distance_ms = 1000;

// Seeking should be at least as precise as this.

// That means: The actual achieved seek position must not be more than this amount of time before the requested seek position.

constexpr u64 const seek_tolerance_ms = 5000;

using LoaderSamples = ErrorOr<FixedArray<Sample>, LoaderError>;

using MaybeLoaderError = ErrorOr<void, LoaderError>;

class LoaderPlugin {

public:

    explicit LoaderPlugin(NonnullOwnPtr<SeekableStream> stream);

    virtual ~LoaderPlugin() = default;

    // Load as many audio chunks as necessary to get up to the required samples.

    // A chunk can be anything that is convenient for the plugin to load in one go without requiring to move samples around different buffers.

    // For example: A FLAC, MP3 or QOA frame.

    // The chunks are returned in a vector, so the loader can simply add chunks until the requested sample amount is reached.

    // The sample count MAY be surpassed, but only as little as possible. It CAN be undershot when the end of the stream is reached.

    // If the loader has no chunking limitations (e.g. WAV), it may return a single exact-sized chunk.

    virtual ErrorOr<Vector<FixedArray<Sample>>, LoaderError> load_chunks(size_t samples_to_read_from_input) = 0;

    virtual MaybeLoaderError reset() = 0;

    virtual MaybeLoaderError seek(int const sample_index) = 0;

    // total_samples() and loaded_samples() should be independent

    // of the number of channels.

    //

    // For example, with a three-second-long, stereo, 44.1KHz audio file:

    //    num_channels() should return 2

    //    sample_rate() should return 44100 (each channel is sampled at this rate)

    //    total_samples() should return 132300 (sample_rate * three seconds)

    virtual int loaded_samples() = 0;

    virtual int total_samples() = 0;

    virtual u32 sample_rate() = 0;

    virtual u16 num_channels() = 0;

    // Human-readable name of the file format, of the form <full abbreviation> (.<ending>)

    virtual ByteString format_name() = 0;

    virtual PcmSampleFormat pcm_format() = 0;

    Metadata const& metadata() const { return m_metadata; }

    Vector<PictureData> const& pictures() const { return m_pictures; }

protected:

    NonnullOwnPtr<SeekableStream> m_stream;

    Vector<PictureData> m_pictures;

    Metadata m_metadata;

};

class Loader : public RefCounted<Loader> {

public:

    static ErrorOr<NonnullRefPtr<Loader>, LoaderError> create(StringView path);

    static ErrorOr<NonnullRefPtr<Loader>, LoaderError> create(ReadonlyBytes buffer);

    // Will only read less samples if we're at the end of the stream.

    LoaderSamples get_more_samples(size_t samples_to_read_from_input = 128 * KiB);

    MaybeLoaderError reset() const

    {

        m_plugin_at_end_of_stream = false;

        return m_plugin->reset();

    }

    MaybeLoaderError seek(int const position) const

    {

        m_buffer.clear_with_capacity();

        m_plugin_at_end_of_stream = false;

        return m_plugin->seek(position);

    }

    int loaded_samples() const { return m_plugin->loaded_samples() - (int)m_buffer.size(); }

    int total_samples() const { return m_plugin->total_samples(); }

    u32 sample_rate() const { return m_plugin->sample_rate(); }

    u16 num_channels() const { return m_plugin->num_channels(); }

    ByteString format_name() const { return m_plugin->format_name(); }

    u16 bits_per_sample() const { return pcm_bits_per_sample(m_plugin->pcm_format()); }

    PcmSampleFormat pcm_format() const { return m_plugin->pcm_format(); }

    Metadata const& metadata() const { return m_plugin->metadata(); }

    Vector<PictureData> const& pictures() const { return m_plugin->pictures(); }

private:

    static ErrorOr<NonnullOwnPtr<LoaderPlugin>, LoaderError> create_plugin(NonnullOwnPtr<SeekableStream> stream);

    explicit Loader(NonnullOwnPtr<LoaderPlugin>);

    mutable NonnullOwnPtr<LoaderPlugin> m_plugin;

    // The plugin can signal an end of stream by returning no (or only empty) chunks.

    mutable bool m_plugin_at_end_of_stream { false };

    mutable Vector<Sample, loader_buffer_size> m_buffer;

};

}