squeezelite-esp32/components/spotify/cspot/bell/main/audio-dsp/include/BiquadCombo.h

#pragma once

#include <stdint.h>   // for uint32_t
#include <map>        // for map
#include <memory>     // for unique_ptr, allocator
#include <mutex>      // for scoped_lock
#include <stdexcept>  // for invalid_argument
#include <string>     // for string, operator==, char_traits, basic_...
#include <vector>     // for vector

#include "AudioTransform.h"   // for AudioTransform
#include "Biquad.h"           // for Biquad
#include "StreamInfo.h"       // for StreamInfo
#include "TransformConfig.h"  // for TransformConfig

namespace bell {
class BiquadCombo : public bell::AudioTransform {
 private:
  std::vector<std::unique_ptr<bell::Biquad>> biquads;

  // Calculates Q values for Nth order Butterworth / Linkwitz-Riley filters
  std::vector<float> calculateBWQ(int order);
  std::vector<float> calculateLRQ(int order);

 public:
  BiquadCombo();
  ~BiquadCombo(){};
  int channel;

  std::map<std::string, float> paramCache = {{"order", 0.0f},
                                             {"frequency", 0.0f}};

  enum class FilterType { Highpass, Lowpass };

  void linkwitzRiley(float freq, int order, FilterType type);
  void butterworth(float freq, int order, FilterType type);

  std::unique_ptr<StreamInfo> process(
      std::unique_ptr<StreamInfo> data) override;
  void sampleRateChanged(uint32_t sampleRate) override;

  void reconfigure() override {
    std::scoped_lock lock(this->accessMutex);

    float freq = config->getFloat("frequency");
    int order = config->getInt("order");

    if (paramCache["frequency"] == freq && paramCache["order"] == order) {
      return;
    } else {
      paramCache["frequency"] = freq;
      paramCache["order"] = order;
    }

    this->channel = config->getChannels()[0];
    this->biquads = std::vector<std::unique_ptr<bell::Biquad>>();
    auto type = config->getString("combo_type");
    if (type == "lr_lowpass") {
      this->linkwitzRiley(freq, order, FilterType::Lowpass);
    } else if (type == "lr_highpass") {
      this->linkwitzRiley(freq, order, FilterType::Highpass);
    } else if (type == "bw_highpass") {
      this->butterworth(freq, order, FilterType::Highpass);
    } else if (type == "bw_lowpass") {
      this->butterworth(freq, order, FilterType::Highpass);
    } else {
      throw std::invalid_argument("Invalid combo filter type");
    }
  }
};
};  // namespace bell