timestretch_engine.h

// SPDX-FileCopyrightText: © 2026 Alexandros Theodotou <alex@zrythm.org>
// SPDX-License-Identifier: LicenseRef-ZrythmLicense
 
#pragma once
 
#include <cstdint>
#include <memory>
#include <span>
#include <stdexcept>
#include <string_view>
 
#include "dsp/time_warp_map.h"
#include "utils/audio.h"
#include "utils/units.h"
 
#include <QObject>
 
namespace zrythm::dsp
{

struct StretchOptions
{
  Q_GADGET
 
public:
  enum class Algorithm : std::uint8_t
  {
    Beats,
    Monophonic,
    Polyphonic,
    Repitch,
  };
  Q_ENUM (Algorithm)
 
  Algorithm algorithm{ Algorithm::Polyphonic };
  bool preserve_formants{ false };
};

class ITimeStretchEngine
{
public:
  virtual ~ITimeStretchEngine () = default;

  [[nodiscard]] virtual std::string_view id () const = 0;

  [[nodiscard]] virtual bool
  supports (StretchOptions::Algorithm algorithm) const = 0;

  [[nodiscard]] utils::audio::AudioBuffer stretch (
    const utils::audio::AudioBuffer &input,
    const TimeWarpMap               &warp,
    const StretchOptions            &options) [[clang::blocking]]
  {
    if (!warp.is_valid ())
      throw std::invalid_argument ("TimeWarpMap is not valid");
    if (warp.source_length != units::samples (input.getNumSamples ()))
      throw std::invalid_argument (
        "TimeWarpMap source_length does not match input frame count");
    if (!supports (options.algorithm))
      throw std::invalid_argument (
        "engine does not support the requested algorithm");
    return stretch_impl (input, warp, options);
  }
 
private:
  [[nodiscard]] virtual utils::audio::AudioBuffer stretch_impl (
    const utils::audio::AudioBuffer &input,
    const TimeWarpMap               &warp,
    const StretchOptions            &options) [[clang::blocking]] = 0;
};

enum class TimeStretchEngineId : std::uint8_t
{
  RubberBand,
  Resampler, 
};

struct TimeStretchEngineInfo
{
  TimeStretchEngineId id;
  std::string_view key;
  std::string_view display_name;
  bool             supports_pitch_preserve;
};

[[nodiscard]] std::span<const TimeStretchEngineInfo>
available_timestretch_engines () noexcept;

[[nodiscard]] std::unique_ptr<ITimeStretchEngine>
create_timestretch_engine (
  TimeStretchEngineId  id,
  units::sample_rate_t sample_rate);

[[nodiscard]] std::unique_ptr<ITimeStretchEngine>
create_default_timestretch_engine (
  const StretchOptions &options,
  units::sample_rate_t  sample_rate);
 
} // namespace zrythm::dsp
 
Q_DECLARE_METATYPE (zrythm::dsp::StretchOptions::Algorithm)