//-- AudioFiltersNative.cpp

#include "pch.h"
#include "AudioFiltersNative.h"
#include <cstring>
#include <algorithm>

static float sampleRate_;
static float highCutoff_;
static float lowCutoff_;

extern "C" {
    //-- Declare the function to be exported
    __declspec(dllexport) void ApplyBandStopFilter(float* data, int channels, int dataLength, float* bufferLow, float* bufferHigh, float lowCutoff, float highCutoff)
    {
        highCutoff_ = highCutoff;
        lowCutoff_ = lowCutoff;

        float* dataPtr = data;
        float* dataEnd = data + dataLength;

        while (dataPtr < dataEnd)
        {
            for (int channel = 0; channel < channels; channel++)
            {
                float sample = *dataPtr;
                for (int i = 0; i < 3; i++)
                {
                    sample = ApplyBandStopFilterInternal(sample, channel, bufferLow, bufferHigh);
                }
                *dataPtr = sample;
                dataPtr++;
            }
        }
    }

    extern "C"
    {
        __declspec(dllexport) void InitializeFilters(float sampleRate) {
            sampleRate_ = sampleRate;
        }
    }

    //-- Helper functions for low-pass and high-pass filters
    inline float ApplyLowPassFilter(float sample, float cutoff, float* buffer, int channel)
    {
        float alpha = cutoff / (cutoff + sampleRate_ / 2);
        float oneMinusAlpha = 1.0f - alpha;
        float filtered = alpha * sample + oneMinusAlpha * buffer[channel];
        buffer[channel] = filtered;
        return filtered;
    }

    inline float ApplyHighPassFilter(float sample, float cutoff, float* buffer, int channel)
    {
        float alpha = cutoff / (cutoff + sampleRate_ / 2);
        float filtered = alpha * (buffer[channel] + sample - buffer[channel]);
        buffer[channel] = filtered;
        return sample - filtered;
    }

    inline float ApplyBandStopFilterInternal(float sample, int channel, float* bufferLow, float* bufferHigh)
    {
        float lowFiltered = ApplyLowPassFilter(sample, lowCutoff_, bufferLow, channel);
        float highFiltered = ApplyHighPassFilter(sample, highCutoff_, bufferHigh, channel);
        return lowFiltered - highFiltered;
    }
}