#ifndef EQ_FILTER_H
#define EQ_FILTER_H

/*************************************************************************/
/*  eq.h                                                                 */
/*************************************************************************/
/*                         This file is part of:                         */
/*                          PANDEMONIUM ENGINE                           */
/*             https://github.com/Relintai/pandemonium_engine            */
/*************************************************************************/
/* Copyright (c) 2022-present Péter Magyar.                              */
/* Copyright (c) 2014-2022 Godot Engine contributors (cf. AUTHORS.md).   */
/* Copyright (c) 2007-2022 Juan Linietsky, Ariel Manzur.                 */
/*                                                                       */
/* Permission is hereby granted, free of charge, to any person obtaining */
/* a copy of this software and associated documentation files (the       */
/* "Software"), to deal in the Software without restriction, including   */
/* without limitation the rights to use, copy, modify, merge, publish,   */
/* distribute, sublicense, and/or sell copies of the Software, and to    */
/* permit persons to whom the Software is furnished to do so, subject to */
/* the following conditions:                                             */
/*                                                                       */
/* The above copyright notice and this permission notice shall be        */
/* included in all copies or substantial portions of the Software.       */
/*                                                                       */
/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
/*************************************************************************/

// Author: reduzio@gmail.com (C) 2006

#include "core/containers/vector.h"
#include "core/typedefs.h"

/**
@author Juan Linietsky
*/

class EQ {
public:
	enum Preset {

		PRESET_6_BANDS,
		PRESET_8_BANDS,
		PRESET_10_BANDS,
		PRESET_21_BANDS,
		PRESET_31_BANDS
	};

	class BandProcess {
		friend class EQ;
		float c1, c2, c3;
		struct History {
			float a1, a2, a3;
			float b1, b2, b3;

		} history;

	public:
		inline void process_one(float &p_data);

		BandProcess();
	};

private:
	struct Band {
		float freq;
		float c1, c2, c3;
	};

	Vector<Band> band;

	float mix_rate;

	void recalculate_band_coefficients();

public:
	void set_mix_rate(float p_mix_rate);

	int get_band_count() const;
	void set_preset_band_mode(Preset p_preset);
	void set_bands(const Vector<float> &p_bands);
	BandProcess get_band_processor(int p_band) const;
	float get_band_frequency(int p_band);

	EQ();
	~EQ();
};

/* Inline Function */

inline void EQ::BandProcess::process_one(float &p_data) {
	history.a1 = p_data;

	history.b1 = c1 * (history.a1 - history.a3) + c3 * history.b2 - c2 * history.b3;

	p_data = history.b1;

	history.a3 = history.a2;
	history.a2 = history.a1;
	history.b3 = history.b2;
	history.b2 = history.b1;
}

#endif