#include "bs412.h"

#define BS412_TIME 60
#define CLAMP(x, lo, hi) (((x) < (lo)) ? (lo) : ((x) > (hi) ? (hi) : (x)))

#define SQRT19000 180499999.99999997f // (19000 / sqrt(2)) * 19000 / sqrt(2)

// inline float dbr_to_deviation(float dbr) {
// 	return 19000.0f * sqrtf(pow(10.0, dbr / 10.0));
// }

inline float deviation_to_dbr(float deviation) {
	if (deviation < 1e-6f) return -100.0f;
	return 10*log10f((deviation*deviation)/SQRT19000);
}

void init_bs412(BS412Compressor* comp, uint32_t mpx_deviation, float target_power, float attack, float release, float max_gain, uint32_t sample_rate) {
	comp->mpx_deviation = mpx_deviation;
	comp->avg_power = 0.0f;
    comp->alpha = 1.0f / (BS412_TIME * sample_rate);
	comp->sample_rate = sample_rate;
	comp->attack = expf(-1.0f / (attack * sample_rate));
	comp->release = expf(-1.0f / (release * sample_rate));
	comp->target = target_power; // target is expected to not be our rms format
	comp->gain = 1.0f;
	comp->can_compress = 1;
	comp->second_counter = BS412_TIME+1;
	comp->max_gain = max_gain;
	#ifdef BS412_DEBUG
	debug_printf("Initialized MPX power measurement with sample rate: %d\n", sample_rate);
	#endif
}

float bs412_compress(BS412Compressor* comp, float audio, float sample_mpx) {
	float combined = audio + sample_mpx;
	float output_sample = (audio * comp->gain) + sample_mpx;

	comp->avg_power += comp->alpha * ((output_sample * output_sample * comp->mpx_deviation * comp->mpx_deviation) - comp->avg_power);

	if(comp->sample_counter % 8 == 0) {
		comp->avg_deviation = sqrtf(comp->avg_power);
		comp->modulation_power = deviation_to_dbr(comp->avg_deviation);
	}

	if(comp->sample_counter > comp->sample_rate) {
		comp->sample_counter = 0;
		if(comp->can_compress == 0) comp->second_counter++;
	}

	if(comp->can_compress == 0 && comp->second_counter > BS412_TIME) {
		#ifdef BS412_DEBUG
		debug_printf("Can compress.\n");
		#endif
		comp->can_compress = 1;
		comp->second_counter = 0;
	} else {
		comp->sample_counter++;
		return combined;
	}

	float target_gain = expf((comp->target - comp->modulation_power) * 0.2302585093f); // 1/10 * ln(10)
	if (comp->modulation_power > comp->target) comp->gain = comp->attack * comp->gain + (1.0f - comp->attack) * target_gain;
	else comp->gain = comp->release * comp->gain + (1.0f - comp->release) * target_gain;
	
	comp->gain = CLAMP(comp->gain, 0.0f, comp->max_gain);

	float dev_after_gain = deviation_to_dbr(comp->avg_deviation * comp->gain);
	if(dev_after_gain > comp->target && comp->modulation_power < comp->target) {
		// Gain is too much, reduce
		float reduction_factor = expf((comp->target - dev_after_gain) * 0.2302585093f);
		comp->gain = CLAMP(comp->gain * reduction_factor, 0.01f, comp->max_gain);
	}

	comp->sample_counter++;

	#ifdef BS412_DEBUG
	debug_printf("MPX: %.2f dBr | gain: %.6f | target_gain: %.6f\n",
			comp->modulation_power,
			comp->gain,
			target_gain);
	#endif

	return output_sample;
}
