/* ========================================
 *  BiquadPlus - BiquadPlus.h
 *  Copyright (c) 2016 airwindows, Airwindows uses the MIT license
 * ======================================== */

#include "BiquadPlus.h"

#ifdef SHR3D_SFX_CORE_AIRWINDOWS

namespace airwinconsolidated::BiquadPlus {

void BiquadPlus::processBlock(float **inputs, float **outputs, int sampleFrames) 
{
    float* in1  =  inputs[0];
    float* in2  =  inputs[1];
    float* out1 = outputs[0];
    float* out2 = outputs[1];

	int inFramesToProcess = sampleFrames; //vst doesn't give us this as a separate variable so we'll make it
	double overallscale = 1.0;
	overallscale /= 44100.0;
	overallscale *= getSampleRate();
	
	int type = ceil((A*3.999)+0.00001);

	biquad[biq_freq] = ((B*B*B*20000.0)/getSampleRate());
	if (biquad[biq_freq] < 0.0001) biquad[biq_freq] = 0.0001;
	
    biquad[biq_reso] = (C*C*C*29.99)+0.01;
	if (biquad[biq_reso] < 0.0001) biquad[biq_reso] = 0.0001;
	
	
	
	double wet = (D*2.0)-1.0;
	
	//biquad contains these values:
	//[0] is frequency: 0.000001 to 0.499999 is near-zero to near-Nyquist
	//[1] is resonance, 0.7071 is Butterworth. Also can't be zero
	//[2] is a0 but you need distinct ones for additional biquad instances so it's here
	//[3] is a1 but you need distinct ones for additional biquad instances so it's here
	//[4] is a2 but you need distinct ones for additional biquad instances so it's here
	//[5] is b1 but you need distinct ones for additional biquad instances so it's here
	//[6] is b2 but you need distinct ones for additional biquad instances so it's here
	//[7] is LEFT stored delayed sample (freq and res are stored so you can move them sample by sample)
	//[8] is LEFT stored delayed sample (you have to include the coefficient making code if you do that)
	//[9] is RIGHT stored delayed sample (freq and res are stored so you can move them sample by sample)
	//[10] is RIGHT stored delayed sample (you have to include the coefficient making code if you do that)
	
	//to build a dedicated filter, rename 'biquad' to whatever the new filter is, then
	//put this code either within the sample buffer (for smoothly modulating freq or res)
	//or in this 'read the controls' area (for letting you change freq and res with controls)
	//or in 'reset' if the freq and res are absolutely fixed (use GetSampleRate to define freq)
	
	biquad[biq_aA0] = biquad[biq_aB0];
	biquad[biq_aA1] = biquad[biq_aB1];
	biquad[biq_aA2] = biquad[biq_aB2];
	biquad[biq_bA1] = biquad[biq_bB1];
	biquad[biq_bA2] = biquad[biq_bB2];
	//previous run through the buffer is still in the filter, so we move it
	//to the A section and now it's the new starting point.

	if (type == 1) { //lowpass
		double K = tan(M_PI * biquad[biq_freq]);
		double norm = 1.0 / (1.0 + K / biquad[biq_reso] + K * K);
		biquad[biq_aB0] = K * K * norm;
		biquad[biq_aB1] = 2.0 * biquad[biq_aB0];
		biquad[biq_aB2] = biquad[biq_aB0];
		biquad[biq_bB1] = 2.0 * (K * K - 1.0) * norm;
		biquad[biq_bB2] = (1.0 - K / biquad[biq_reso] + K * K) * norm;
	}
	
	if (type == 2) { //highpass
		double K = tan(M_PI * biquad[biq_freq]);
		double norm = 1.0 / (1.0 + K / biquad[biq_reso] + K * K);
		biquad[biq_aB0] = norm;
		biquad[biq_aB1] = -2.0 * biquad[biq_aB0];
		biquad[biq_aB2] = biquad[biq_aB0];
		biquad[biq_bB1] = 2.0 * (K * K - 1.0) * norm;
		biquad[biq_bB2] = (1.0 - K / biquad[biq_reso] + K * K) * norm;
	}
	
	if (type == 3) { //bandpass
		double K = tan(M_PI * biquad[biq_freq]);
		double norm = 1.0 / (1.0 + K / biquad[biq_reso] + K * K);
		biquad[biq_aB0] = K / biquad[biq_reso] * norm;
		biquad[biq_aB1] = 0.0; //bandpass can simplify the biquad kernel: leave out this multiply
		biquad[biq_aB2] = -biquad[biq_aB0];
		biquad[biq_bB1] = 2.0 * (K * K - 1.0) * norm;
		biquad[biq_bB2] = (1.0 - K / biquad[biq_reso] + K * K) * norm;
	}
	
	if (type == 4) { //notch
		double K = tan(M_PI * biquad[biq_freq]);
		double norm = 1.0 / (1.0 + K / biquad[biq_reso] + K * K);
		biquad[biq_aB0] = (1.0 + K * K) * norm;
		biquad[biq_aB1] = 2.0 * (K * K - 1) * norm;
		biquad[biq_aB2] = biquad[biq_aB0];
		biquad[biq_bB1] = biquad[biq_aB1];
		biquad[biq_bB2] = (1.0 - K / biquad[biq_reso] + K * K) * norm;
	}
	
	if (biquad[biq_aA0] == 0.0) { // if we have just started, start directly with raw info
		biquad[biq_aA0] = biquad[biq_aB0];
		biquad[biq_aA1] = biquad[biq_aB1];
		biquad[biq_aA2] = biquad[biq_aB2];
		biquad[biq_bA1] = biquad[biq_bB1];
		biquad[biq_bA2] = biquad[biq_bB2];
	}
	
    while (--sampleFrames >= 0)
    {
		double inputSampleL = *in1;
		double inputSampleR = *in2;
		if (fabs(inputSampleL)<1.18e-23) inputSampleL = fpdL * 1.18e-17;
		if (fabs(inputSampleR)<1.18e-23) inputSampleR = fpdR * 1.18e-17;
		double drySampleL = inputSampleL;
		double drySampleR = inputSampleR;
		
		double buf = (double)sampleFrames/inFramesToProcess;
		biquad[biq_a0] = (biquad[biq_aA0]*buf)+(biquad[biq_aB0]*(1.0-buf));
		biquad[biq_a1] = (biquad[biq_aA1]*buf)+(biquad[biq_aB1]*(1.0-buf));
		biquad[biq_a2] = (biquad[biq_aA2]*buf)+(biquad[biq_aB2]*(1.0-buf));
		biquad[biq_b1] = (biquad[biq_bA1]*buf)+(biquad[biq_bB1]*(1.0-buf));
		biquad[biq_b2] = (biquad[biq_bA2]*buf)+(biquad[biq_bB2]*(1.0-buf));
		double tempSample = (inputSampleL * biquad[biq_a0]) + biquad[biq_sL1];
		biquad[biq_sL1] = (inputSampleL * biquad[biq_a1]) - (tempSample * biquad[biq_b1]) + biquad[biq_sL2];
		biquad[biq_sL2] = (inputSampleL * biquad[biq_a2]) - (tempSample * biquad[biq_b2]);
		inputSampleL = tempSample;
		tempSample = (inputSampleR * biquad[biq_a0]) + biquad[biq_sR1];
		biquad[biq_sR1] = (inputSampleR * biquad[biq_a1]) - (tempSample * biquad[biq_b1]) + biquad[biq_sR2];
		biquad[biq_sR2] = (inputSampleR * biquad[biq_a2]) - (tempSample * biquad[biq_b2]);
		inputSampleR = tempSample;
				
		if (wet < 1.0) {
			inputSampleL = (inputSampleL*wet) + (drySampleL*(1.0-fabs(wet)));
			inputSampleR = (inputSampleR*wet) + (drySampleR*(1.0-fabs(wet)));
			//inv/dry/wet lets us turn LP into HP and band into notch
		}
		
		//begin 32 bit stereo floating point dither
		int expon; frexpf((float)inputSampleL, &expon);
		fpdL ^= fpdL << 13; fpdL ^= fpdL >> 17; fpdL ^= fpdL << 5;
		inputSampleL += double((double(fpdL)-uint32_t(0x7fffffff)) * 5.5e-36l * pow(2.0,expon+62.0));
		frexpf((float)inputSampleR, &expon);
		fpdR ^= fpdR << 13; fpdR ^= fpdR >> 17; fpdR ^= fpdR << 5;
		inputSampleR += double((double(fpdR)-uint32_t(0x7fffffff)) * 5.5e-36l * pow(2.0,expon+62.0));
		//end 32 bit stereo floating point dither
		
		*out1 = float(inputSampleL);
		*out2 = float(inputSampleR);

		in1++;
		in2++;
		out1++;
		out2++;
    }
}

} // end namespace

#endif // SHR3D_SFX_CORE_AIRWINDOWS
