PluginProcessor.h

/*
  ==============================================================================

    This file contains the basic framework code for a JUCE plugin processor.

  ==============================================================================
*/

#pragma once

#include <JuceHeader.h>
#include "DSP/SingleChannelSampleFifo.h"

#include <array>

enum Slope
{
    Slope_12,
    Slope_24,
    Slope_36,
    Slope_48
};

struct ChainSettings
{
    float peak1Freq { 0 }, peak1GainInDecibels{ 0 }, peak1Quality {1.f};
    float peak2Freq { 0 }, peak2GainInDecibels{ 0 }, peak2Quality {1.f};
    float peak3Freq { 0 }, peak3GainInDecibels{ 0 }, peak3Quality {1.f};
    float lowCutFreq { 0 }, highCutFreq { 0 };
    
    Slope lowCutSlope { Slope::Slope_12 }, highCutSlope { Slope::Slope_12 };
    
    bool lowCutBypassed { false }, peak1Bypassed { false }, peak2Bypassed { false }, peak3Bypassed { false }, highCutBypassed { false };
};

ChainSettings getChainSettings(juce::AudioProcessorValueTreeState& apvts);

using Filter = juce::dsp::IIR::Filter<float>;

using CutFilter = juce::dsp::ProcessorChain<Filter, Filter, Filter, Filter>;

using MonoChain = juce::dsp::ProcessorChain<CutFilter, Filter, Filter, Filter, CutFilter>;

enum ChainPositions
{
    LowCut,
    Peak1,
    Peak2,
    Peak3,
    HighCut
};

using Coefficients = Filter::CoefficientsPtr;
void updateCoefficients(Coefficients& old, const Coefficients& replacements);

//Coefficients makePeakFilter(const ChainSettings& chainSettings, double sampleRate);
Coefficients makePeakFilter(float freq, float quality, float decibels, double sampleRate);

template<int Index, typename ChainType, typename CoefficientType>
void update(ChainType& chain, const CoefficientType& coefficients)
{
    updateCoefficients(chain.template get<Index>().coefficients, coefficients[Index]);
    chain.template setBypassed<Index>(false);
}

template<typename ChainType, typename CoefficientType>
void updateCutFilter(ChainType& chain,
                     const CoefficientType& coefficients,
                     const Slope& slope)
{
    chain.template setBypassed<0>(true);
    chain.template setBypassed<1>(true);
    chain.template setBypassed<2>(true);
    chain.template setBypassed<3>(true);
    
    switch( slope )
    {
        case Slope_48:
        {
            update<3>(chain, coefficients);
        }
        case Slope_36:
        {
            update<2>(chain, coefficients);
        }
        case Slope_24:
        {
            update<1>(chain, coefficients);
        }
        case Slope_12:
        {
            update<0>(chain, coefficients);
        }
    }
}

inline auto makeLowCutFilter(const ChainSettings& chainSettings, double sampleRate )
{
    return juce::dsp::FilterDesign<float>::designIIRHighpassHighOrderButterworthMethod(chainSettings.lowCutFreq,
                                                                                       sampleRate,
                                                                                       2 * (chainSettings.lowCutSlope + 1));
}

inline auto makeHighCutFilter(const ChainSettings& chainSettings, double sampleRate )
{
    return juce::dsp::FilterDesign<float>::designIIRLowpassHighOrderButterworthMethod(chainSettings.highCutFreq,
                                                                                      sampleRate,
                                                                                      2 * (chainSettings.highCutSlope + 1));
}
//==============================================================================
/**
*/
class SimpleEQAudioProcessor  : public juce::AudioProcessor
{
public:
    //==============================================================================
    SimpleEQAudioProcessor();
    ~SimpleEQAudioProcessor() override;

    //==============================================================================
    void prepareToPlay (double sampleRate, int samplesPerBlock) override;
    void releaseResources() override;

   #ifndef JucePlugin_PreferredChannelConfigurations
    bool isBusesLayoutSupported (const BusesLayout& layouts) const override;
   #endif

    void processBlock (juce::AudioBuffer<float>&, juce::MidiBuffer&) override;

    //==============================================================================
    juce::AudioProcessorEditor* createEditor() override;
    bool hasEditor() const override;

    //==============================================================================
    const juce::String getName() const override;

    bool acceptsMidi() const override;
    bool producesMidi() const override;
    bool isMidiEffect() const override;
    double getTailLengthSeconds() const override;

    //==============================================================================
    int getNumPrograms() override;
    int getCurrentProgram() override;
    void setCurrentProgram (int index) override;
    const juce::String getProgramName (int index) override;
    void changeProgramName (int index, const juce::String& newName) override;

    //==============================================================================
    void getStateInformation (juce::MemoryBlock& destData) override;
    void setStateInformation (const void* data, int sizeInBytes) override;

    static juce::AudioProcessorValueTreeState::ParameterLayout createParameterLayout();
    juce::AudioProcessorValueTreeState apvts {*this, nullptr, "Parameters", createParameterLayout()};
    
    using BlockType = juce::AudioBuffer<float>;
    SingleChannelSampleFifo<BlockType> leftChannelFifo { Channel::Left };
    SingleChannelSampleFifo<BlockType> rightChannelFifo { Channel::Right };
private:
    MonoChain leftChain, rightChain;
    
    void updatePeakFilter(const ChainSettings& chainSettings);
    void updateLowCutFilters(const ChainSettings& chainSettings);
    void updateHighCutFilters(const ChainSettings& chainSettings);
    
    void updateFilters();
    
    juce::dsp::Oscillator<float> osc;
    //==============================================================================
    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (SimpleEQAudioProcessor)
};