#ifndef ORFANIDIS_EQ_H_
#define ORFANIDIS_EQ_H_

#include <math.h>
#include <vector>

using namespace std;

namespace orfanidis_eq {
	//Eq data types.
	typedef double eq_single_t;
	typedef double eq_double_t;
	//NOTE: the default float type usage
	//can have shortage of precision

	//Eq types
	typedef enum
	{
		none,
		butterworth,
		chebyshev1,
		chebyshev2
	} filter_type;

	static const char *get_eq_text(filter_type type) {
		switch(type) {
			case none:
				return "not initialized";
			case butterworth:
				return "butterworth";
			case chebyshev1:
				return "chebyshev1";
			case chebyshev2:
				return "chebyshev2";
			default:
				return "none";
		}
	}

	//Eq errors
	typedef enum
	{
		no_error,
		invalid_input_data_error,
		processing_error
	} eq_error_t;

	//Constants
	static const eq_double_t pi = 3.1415926535897932384626433832795;
	static const unsigned int fo_section_order = 4;

	//Default gains
	static const int max_base_gain_db = 0;
	static const int min_base_gain_db = -60;
	static const int butterworth_band_gain_db = -3;
	static const int chebyshev1_band_base_gain_db = -6;
	static const int chebyshev2_band_base_gain_db = -40;
	static const int eq_min_max_gain_db = 46;

	//Default freq's
	static const eq_double_t lowest_grid_center_freq_hz = 31.25;
	static const eq_double_t bands_grid_center_freq_hz = 1000;
	static const eq_double_t lowest_audio_freq_hz = 20;
	static const eq_double_t highest_audio_freq_hz = 20000;

	//Eq config constants
	static const unsigned int default_eq_band_filters_order = 4; //>2
	static const eq_double_t default_sample_freq_hz = 48000;

	//Precomputed Eq (eq2) config constants
	static const eq_double_t p_eq_min_max_gain_db = 40;
	static const eq_double_t p_eq_gain_step_db = 1;
	static const eq_double_t common_base_gain_db = 3;
	static const eq_double_t p_eq_default_gain_db = 0;

	//Version
	static const char* eq_version = "0.01";


	//------------ Conversion functions class ------------
	class conversions
	{
		int db_min_max;
		std::vector<eq_double_t> lin_gains;

		int lin_gains_index(eq_double_t x) {
			int int_x = (int)x;
			if((x >= -db_min_max) && (x < db_min_max - 1))
				return db_min_max + int_x;

			return db_min_max;
		}

		conversions() {}

	public:
		conversions(int min_max) {
			db_min_max = min_max;
			//Update table (vector elements) for fast conversions
			int step = -min_max;
			while(step <= min_max)
				lin_gains.push_back(db_2_lin(step++));
		}

		inline eq_double_t fast_db_2_lin(eq_double_t x) {
			int int_part = (int)x;
			eq_double_t frac_part = x - int_part;
			return lin_gains[lin_gains_index(int_part)] * (1 - frac_part) +
				(lin_gains[lin_gains_index(int_part + 1)])*frac_part;
		}

		inline eq_double_t fast_lin_2_db(eq_double_t x) {
			if((x >= lin_gains[0]) && (x < lin_gains[lin_gains.size() - 1])) {
				for(unsigned int i = 0; i < lin_gains.size() - 2; i++)
					if((x >= lin_gains[i]) && (x < lin_gains[i + 1])) {
						int int_part = i - db_min_max;
						eq_double_t frac_part = x - (int)(x);
						return int_part + frac_part;
					}
			}
			return 0;
		}

		inline static eq_double_t db_2_lin(eq_double_t x) {
			return pow(10, x / 20);
		}

		inline static eq_double_t lin_2_db(eq_double_t x) {
			return 20 * log10(x);
		}

		inline static eq_double_t rad_2_hz(eq_double_t x, eq_double_t fs) {
			return 2 * pi / x*fs;
		}

		inline static eq_double_t hz_2_rad(eq_double_t x, eq_double_t fs) {
			return 2 * pi*x / fs;
		}
	};

	//------------ Band freq's structure ------------
	struct band_freqs
	{
	private:
		band_freqs();

	public:
		eq_double_t min_freq;
		eq_double_t center_freq;
		eq_double_t max_freq;

		band_freqs(eq_double_t f1, eq_double_t f0, eq_double_t f2) :
			min_freq(f1), center_freq(f0), max_freq(f2) {}

		~band_freqs() {}
	};

	//------------ Frequency grid class ------------
	class freq_grid
	{
	private:
		std::vector<band_freqs> freqs_;

	public:
		freq_grid() {}
		freq_grid(const freq_grid& fg) { this->freqs_ = fg.freqs_; }
		~freq_grid() {}

		eq_error_t set_band(eq_double_t fmin, eq_double_t f0, eq_double_t fmax) {
			freqs_.clear();
			return add_band(fmin, f0, fmax);
		}

		//fc, fmin, fmax
		eq_error_t add_band(eq_double_t fmin, eq_double_t f0, eq_double_t fmax) {
			if(fmin < f0 && f0 < fmax)
				freqs_.push_back(band_freqs(fmin, f0, fmax));
			else
				return invalid_input_data_error;
			return no_error;
		}

		//f0, deltaf = fmax - fmin
		eq_error_t add_band(eq_double_t f0, eq_double_t df) {
			if(f0 >= df / 2) {
				eq_double_t fmin = f0 - df / 2;
				eq_double_t fmax = f0 + df / 2;
				freqs_.push_back(band_freqs(fmin, f0, fmax));
			} else
				return invalid_input_data_error;
			return no_error;
		}

		eq_error_t set_5_bands(eq_double_t center_freq = bands_grid_center_freq_hz) {
			freqs_.clear();
			if(lowest_audio_freq_hz < center_freq &&
				center_freq < highest_audio_freq_hz) {

				//Find lowest center frequency in band
				eq_double_t lowest_center_freq = center_freq;
				while(lowest_center_freq > lowest_grid_center_freq_hz)
					lowest_center_freq /= 4.0;
				if(lowest_center_freq < lowest_grid_center_freq_hz)
					lowest_center_freq *= 4.0;

				//Calculate freq's
				eq_double_t f0 = lowest_center_freq;
				for(unsigned int i = 0; i < 5; i++) {
					freqs_.push_back(band_freqs(f0 / 2, f0, f0 * 2));
					f0 *= 4;
				}
			} else
				return invalid_input_data_error;
			return no_error;
		}

		eq_error_t set_10_bands(eq_double_t center_freq = bands_grid_center_freq_hz) {
			freqs_.clear();
			if(lowest_audio_freq_hz < center_freq &&
				center_freq < highest_audio_freq_hz) {

				//Find lowest center frequency in band
				eq_double_t lowest_center_freq = center_freq;
				while(lowest_center_freq > lowest_grid_center_freq_hz)
					lowest_center_freq /= 2;
				if(lowest_center_freq < lowest_grid_center_freq_hz)
					lowest_center_freq *= 2;

				//Calculate freq's
				eq_double_t f0 = lowest_center_freq;
				for(unsigned int i = 0; i < 10; i++) {
					freqs_.push_back(band_freqs(f0 / pow(2, 0.5), f0, f0*pow(2, 0.5)));
					f0 *= 2;
				}
			} else
				return invalid_input_data_error;
			return no_error;
		}

		eq_error_t set_20_bands(eq_double_t center_freq = bands_grid_center_freq_hz) {
			freqs_.clear();
			if(lowest_audio_freq_hz < center_freq &&
				center_freq < highest_audio_freq_hz) {

				//Find lowest center frequency in band
				eq_double_t lowest_center_freq = center_freq;
				while(lowest_center_freq > lowest_audio_freq_hz)
					lowest_center_freq /= pow(2, 0.5);
				if(lowest_center_freq < lowest_audio_freq_hz)
					lowest_center_freq *= pow(2, 0.5);

				//Calculate freq's
				eq_double_t f0 = lowest_center_freq;
				for(unsigned int i = 0; i < 20; i++) {
					freqs_.push_back(band_freqs(f0 / pow(2, 0.25),
						f0, f0*pow(2, 0.25)));
					f0 *= pow(2, 0.5);
				}
			} else
				return invalid_input_data_error;
			return no_error;
		}

		eq_error_t set_30_bands(eq_double_t center_freq = bands_grid_center_freq_hz) {
			freqs_.clear();
			if(lowest_audio_freq_hz < center_freq &&
				center_freq < highest_audio_freq_hz) {

				//Find lowest center frequency in band
				eq_double_t lowest_center_freq = center_freq;
				while(lowest_center_freq > lowest_audio_freq_hz)
					lowest_center_freq /= pow(2.0, 1.0 / 3.0);
				if(lowest_center_freq < lowest_audio_freq_hz)
					lowest_center_freq *= pow(2.0, 1.0 / 3.0);

				//Calculate freq's
				eq_double_t f0 = lowest_center_freq;
				for(unsigned int i = 0; i < 30; i++) {
					freqs_.push_back(band_freqs(f0 / pow(2.0, 1.0 / 6.0),
						f0, f0*pow(2.0, 1.0 / 6.0)));
					f0 *= pow(2, 1.0 / 3.0);
				}
			} else
				return invalid_input_data_error;
			return no_error;
		}

		unsigned int get_number_of_bands() { return (unsigned int)freqs_.size(); }

		std::vector<band_freqs> get_freqs() { return freqs_; }

		unsigned int get_freq(unsigned int number) {
			if(number < freqs_.size())
				return (unsigned int)freqs_[number].center_freq;
			else
				return 0;
		}

		unsigned int get_rounded_freq(unsigned int number) {
			if(number < freqs_.size()) {
				unsigned int freq = (unsigned int)freqs_[number].center_freq;
				if(freq < 100)
					return freq;
				else if(freq >= 100 && freq < 1000) {
					unsigned int rest = freq % 10;
					if(rest < 5)
						return freq - rest;
					else
						return freq - rest + 10;
				} else if(freq >= 1000 && freq < 10000) {
					unsigned int rest = freq % 100;
					if(rest < 50)
						return freq - rest;
					else
						return freq - rest + 100;
				} else if(freq >= 10000) {
					unsigned int rest = freq % 1000;
					if(rest < 500)
						return freq - rest;
					else
						return freq - rest + 1000;
				}
			}
			return 0;
		}
	};

	//------------ Forth order sections ------------
	class fo_section
	{
	protected:
		eq_single_t b0; eq_single_t b1; eq_single_t b2; eq_single_t b3; eq_single_t b4;
		eq_single_t a0; eq_single_t a1; eq_single_t a2; eq_single_t a3; eq_single_t a4;

		eq_single_t numBuf[fo_section_order];
		eq_single_t denumBuf[fo_section_order];

		inline eq_single_t df1_fo_process(eq_single_t in) {
			eq_single_t out = 0;
			out += b0*in;
			out += (b1*numBuf[0] - denumBuf[0] * a1);
			out += (b2*numBuf[1] - denumBuf[1] * a2);
			out += (b3*numBuf[2] - denumBuf[2] * a3);
			out += (b4*numBuf[3] - denumBuf[3] * a4);

			numBuf[3] = numBuf[2];
			numBuf[2] = numBuf[1];
			numBuf[1] = numBuf[0];
			if(in < 0.000000000001 && in > -0.000000000001) {
				//Prevent denormalized values (causes extreme performance loss)
				in = 0;
			}
			*numBuf = in;

			denumBuf[3] = denumBuf[2];
			denumBuf[2] = denumBuf[1];
			denumBuf[1] = denumBuf[0];
			if(out < 0.000000000001 && out > -0.000000000001) {
				//Prevent denormalized values (causes extreme performance loss)
				out = 0;
			}
			*denumBuf = out;

			return(out);
		}

	public:
		fo_section() {
			b0 = 1; b1 = 0; b2 = 0; b3 = 0; b4 = 0;
			a0 = 1; a1 = 0; a2 = 0; a3 = 0; a4 = 0;

			for(unsigned int i = 0; i < fo_section_order; i++) {
				numBuf[i] = 0;
				denumBuf[i] = 0;
			}
		}

		virtual ~fo_section() {}

		eq_single_t process(eq_single_t in) {
			return df1_fo_process(in);
		}

		virtual fo_section get() {
			return *this;
		}
	};

	class butterworth_fo_section : public fo_section
	{
		butterworth_fo_section() {}
		butterworth_fo_section(butterworth_fo_section&) {}
	public:
		butterworth_fo_section(eq_double_t beta,
			eq_double_t s, eq_double_t g, eq_double_t g0,
			eq_double_t D, eq_double_t c0) {
			b0 = (g*g*beta*beta + 2 * g*g0*s*beta + g0*g0) / D;
			b1 = -4 * c0*(g0*g0 + g*g0*s*beta) / D;
			b2 = 2 * (g0*g0*(1 + 2 * c0*c0) - g*g*beta*beta) / D;
			b3 = -4 * c0*(g0*g0 - g*g0*s*beta) / D;
			b4 = (g*g*beta*beta - 2 * g*g0*s*beta + g0*g0) / D;

			a0 = 1;
			a1 = -4 * c0*(1 + s*beta) / D;
			a2 = 2 * (1 + 2 * c0*c0 - beta*beta) / D;
			a3 = -4 * c0*(1 - s*beta) / D;
			a4 = (beta*beta - 2 * s*beta + 1) / D;
		}

		fo_section get() { return *this; }
	};

	class chebyshev_type1_fo_section : public fo_section
	{
		chebyshev_type1_fo_section() {}
		chebyshev_type1_fo_section(chebyshev_type1_fo_section&) {}
	public:
		chebyshev_type1_fo_section(eq_double_t a,
			eq_double_t c, eq_double_t tetta_b,
			eq_double_t g0, eq_double_t s, eq_double_t b,
			eq_double_t D, eq_double_t c0) {
			b0 = ((b*b + g0*g0*c*c)*tetta_b*tetta_b + 2 * g0*b*s*tetta_b + g0*g0) / D;
			b1 = -4 * c0*(g0*g0 + g0*b*s*tetta_b) / D;
			b2 = 2 * (g0*g0*(1 + 2 * c0*c0) - (b*b + g0*g0*c*c)*tetta_b*tetta_b) / D;
			b3 = -4 * c0*(g0*g0 - g0*b*s*tetta_b) / D;
			b4 = ((b*b + g0*g0*c*c)*tetta_b*tetta_b - 2 * g0*b*s*tetta_b + g0*g0) / D;

			a0 = 1;
			a1 = -4 * c0*(1 + a*s*tetta_b) / D;
			a2 = 2 * (1 + 2 * c0*c0 - (a*a + c*c)*tetta_b*tetta_b) / D;
			a3 = -4 * c0*(1 - a*s*tetta_b) / D;
			a4 = ((a*a + c*c)*tetta_b*tetta_b - 2 * a*s*tetta_b + 1) / D;
		}

		fo_section get() { return *this; }
	};

	class chebyshev_type2_fo_section : public fo_section
	{
		chebyshev_type2_fo_section() {}
		chebyshev_type2_fo_section(chebyshev_type2_fo_section&) {}
	public:
		chebyshev_type2_fo_section(eq_double_t a,
			eq_double_t c, eq_double_t tetta_b,
			eq_double_t g, eq_double_t s, eq_double_t b,
			eq_double_t D, eq_double_t c0) {
			b0 = (g*g*tetta_b*tetta_b + 2 * g*b*s*tetta_b + b*b + g*g*c*c) / D;
			b1 = -4 * c0*(b*b + g*g*c*c + g*b*s*tetta_b) / D;
			b2 = 2 * ((b*b + g*g*c*c)*(1 + 2 * c0*c0) - g*g*tetta_b*tetta_b) / D;
			b3 = -4 * c0*(b*b + g*g*c*c - g*b*s*tetta_b) / D;
			b4 = (g*g*tetta_b*tetta_b - 2 * g*b*s*tetta_b + b*b + g*g*c*c) / D;

			a0 = 1;
			a1 = -4 * c0*(a*a + c*c + a*s*tetta_b) / D;
			a2 = 2 * ((a*a + c*c)*(1 + 2 * c0*c0) - tetta_b*tetta_b) / D;
			a3 = -4 * c0*(a*a + c*c - a*s*tetta_b) / D;
			a4 = (tetta_b*tetta_b - 2 * a*s*tetta_b + a*a + c*c) / D;
		}

		fo_section get() { return *this; }
	};

	//------------ Bandpass filters ------------
	class bp_filter
	{
	public:
		bp_filter() {}
		virtual ~bp_filter() {}

		virtual eq_single_t process(eq_single_t in) = 0;
	};

	class butterworth_bp_filter : public bp_filter
	{
	private:
		std::vector<fo_section> sections_;

		butterworth_bp_filter() {}
	public:
		butterworth_bp_filter(butterworth_bp_filter& f) {
			this->sections_ = f.sections_;
		}

		butterworth_bp_filter(unsigned int N,
			eq_double_t w0, eq_double_t wb,
			eq_double_t G, eq_double_t Gb, eq_double_t G0) {
			//Case if G == 0 : allpass
			if(G == 0 && G0 == 0) {
				sections_.push_back(fo_section());
				return;
			}

			//Get number of analog sections
			unsigned int r = N % 2;
			unsigned int L = (N - r) / 2;

			//Convert gains to linear scale
			G = conversions::db_2_lin(G);
			Gb = conversions::db_2_lin(Gb);
			G0 = conversions::db_2_lin(G0);

			eq_double_t epsilon = pow(((eq_double_t)(G*G - Gb*Gb)) /
				(Gb*Gb - G0*G0), 0.5);
			eq_double_t g = pow(((eq_double_t)G), 1.0 / ((eq_double_t)N));
			eq_double_t g0 = pow(((eq_double_t)G0), 1.0 / ((eq_double_t)N));
			eq_double_t beta = pow(((eq_double_t)epsilon), -1.0 / ((eq_double_t)N))*
				tan(wb / 2.0);

			eq_double_t c0 = cos(w0);
			if(w0 == 0) c0 = 1;
			if(w0 == pi / 2) c0 = 0;
			if(w0 == pi) c0 = -1;

			//Calculate every section
			for(unsigned int i = 1; i <= L; i++) {
				eq_double_t ui = (2.0*i - 1) / N;
				eq_double_t si = sin(pi*ui / 2.0);

				eq_double_t Di = beta*beta + 2 * si*beta + 1;

				sections_.push_back
				(butterworth_fo_section(beta, si, g, g0, Di, c0));
			}
		}

		~butterworth_bp_filter() {}

		static eq_single_t compute_bw_gain_db(eq_single_t gain) {
			eq_single_t bw_gain = 0;
			if(gain <= -6)
				bw_gain = gain + common_base_gain_db;
			else if(gain > -6 && gain < 6)
				bw_gain = gain*0.5;
			else if(gain >= 6)
				bw_gain = gain - common_base_gain_db;

			return bw_gain;
		}

		virtual eq_single_t process(eq_single_t in) {
			eq_single_t p0 = in;
			eq_single_t p1 = 0;
			//Process FO sections in serial connection
			for(size_t i = 0, len = sections_.size(); i < len; i++) {
				p1 = sections_[i].process(p0);
				p0 = p1;
			}

			return p1;
		}
	};

	class chebyshev_type1_bp_filter : public bp_filter
	{
	private:
		std::vector<fo_section> sections_;

		chebyshev_type1_bp_filter() {}
	public:
		chebyshev_type1_bp_filter(unsigned int N,
			eq_double_t w0, eq_double_t wb,
			eq_double_t G, eq_double_t Gb, eq_double_t G0) {
			//Case if G == 0 : allpass
			if(G == 0 && G0 == 0) {
				sections_.push_back(fo_section());
				return;
			}

			//Get number of analog sections
			unsigned int r = N % 2;
			unsigned int L = (N - r) / 2;

			//Convert gains to linear scale
			G = conversions::db_2_lin(G);
			Gb = conversions::db_2_lin(Gb);
			G0 = conversions::db_2_lin(G0);

			eq_double_t epsilon = pow((eq_double_t)(G*G - Gb*Gb) /
				(Gb*Gb - G0*G0), 0.5);
			eq_double_t g0 = pow((eq_double_t)(G0), 1.0 / N);
			eq_double_t alfa =
				pow(1.0 / epsilon + pow(1 + pow(epsilon, -2.0), 0.5), 1.0 / N);
			eq_double_t beta =
				pow(G / epsilon + Gb*pow(1 + pow(epsilon, -2.0), 0.5), 1.0 / N);
			eq_double_t a = 0.5*(alfa - 1.0 / alfa);
			eq_double_t b = 0.5*(beta - g0*g0*(1 / beta));
			eq_double_t tetta_b = tan(wb / 2);

			eq_double_t c0 = cos(w0);
			if(w0 == 0) c0 = 1;
			if(w0 == pi / 2) c0 = 0;
			if(w0 == pi) c0 = -1;

			//Calculate every section
			for(unsigned int i = 1; i <= L; i++) {
				eq_double_t ui = (2.0*i - 1.0) / N;
				eq_double_t ci = cos(pi*ui / 2.0);
				eq_double_t si = sin(pi*ui / 2.0);

				eq_double_t Di = (a*a + ci*ci)*tetta_b*tetta_b +
					2.0*a*si*tetta_b + 1;
				sections_.push_back(
					chebyshev_type1_fo_section(a, ci, tetta_b, g0, si, b, Di, c0));
			}
		}


		~chebyshev_type1_bp_filter() {}

		static eq_single_t compute_bw_gain_db(eq_single_t gain) {
			eq_single_t bw_gain = 0;
			if(gain <= -6)
				bw_gain = gain + 1;
			else if(gain > -6 && gain < 6)
				bw_gain = gain*0.9;
			else if(gain >= 6)
				bw_gain = gain - 1;

			return bw_gain;
		}

		eq_single_t process(eq_single_t in) {
			eq_single_t p0 = in;
			eq_single_t p1 = 0;
			//Process FO sections in serial connection
			for(size_t i = 0, len = sections_.size(); i < len; i++) {
				p1 = sections_[i].process(p0);
				p0 = p1;
			}

			return p1;
		}
	};

	class chebyshev_type2_bp_filter : public bp_filter
	{
	private:
		std::vector<fo_section> sections_;

		chebyshev_type2_bp_filter() {}
	public:
		chebyshev_type2_bp_filter(unsigned int N,
			eq_double_t w0, eq_double_t wb,
			eq_double_t G, eq_double_t Gb, eq_double_t G0) {
			//Case if G == 0 : allpass
			if(G == 0 && G0 == 0) {
				sections_.push_back(fo_section());
				return;
			}

			//Get number of analog sections
			unsigned int r = N % 2;
			unsigned int L = (N - r) / 2;

			//Convert gains to linear scale
			G = conversions::db_2_lin(G);
			Gb = conversions::db_2_lin(Gb);
			G0 = conversions::db_2_lin(G0);

			eq_double_t epsilon = pow((eq_double_t)((G*G - Gb*Gb) /
				(Gb*Gb - G0*G0)), 0.5);
			eq_double_t g = pow((eq_double_t)(G), 1.0 / N);
			eq_double_t eu = pow(epsilon + sqrt(1 + epsilon*epsilon), 1.0 / N);
			eq_double_t ew = pow(G0*epsilon + Gb*sqrt(1 + epsilon*epsilon), 1.0 / N);
			eq_double_t a = (eu - 1.0 / eu) / 2.0;
			eq_double_t b = (ew - g*g / ew) / 2.0;
			eq_double_t tetta_b = tan(wb / 2);

			eq_double_t c0 = cos(w0);
			if(w0 == 0) c0 = 1;
			if(w0 == pi / 2) c0 = 0;
			if(w0 == pi) c0 = -1;

			//Calculate every section
			for(unsigned int i = 1; i <= L; i++) {
				eq_double_t ui = (2.0*i - 1.0) / N;
				eq_double_t ci = cos(pi*ui / 2.0);
				eq_double_t si = sin(pi*ui / 2.0);
				eq_double_t Di = tetta_b*tetta_b + 2 * a*si*tetta_b + a*a + ci*ci;

				sections_.push_back(
					chebyshev_type2_fo_section(a, ci, tetta_b, g, si, b, Di, c0));
			}
		}

		~chebyshev_type2_bp_filter() {}

		static eq_single_t compute_bw_gain_db(eq_single_t gain) {
			eq_single_t bw_gain = 0;
			if(gain <= -6)
				bw_gain = -common_base_gain_db;
			else if(gain > -6 && gain < 6)
				bw_gain = gain*0.3;
			else if(gain >= 6)
				bw_gain = common_base_gain_db;

			return bw_gain;
		}

		eq_single_t process(eq_single_t in) {
			eq_single_t p0 = in;
			eq_single_t p1 = 0;

			//Process FO sections in serial connection
			for(size_t i = 0, len = sections_.size(); i < len; i++) {
				p1 = sections_[i].process(p0);
				p0 = p1;
			}

			return p1;
		}
	};

	// ------------ eq1 ------------
	// Equalizer with single precomputed filter for every band
	class eq1
	{
	private:
		conversions conv_;
		eq_double_t sampling_frequency_;
		freq_grid freq_grid_;
		std::vector<eq_single_t> band_gains_;
		std::vector<bp_filter*> filters_;
		filter_type current_eq_type_;

		eq1() :conv_(eq_min_max_gain_db) {}
		eq1(const eq1&) :conv_(eq_min_max_gain_db) {}

		void cleanup_filters_array() {
			for(unsigned int j = 0; j < filters_.size(); j++)
				delete filters_[j];
		}

	public:
		eq1(const freq_grid *fg, filter_type eq_t) : conv_(eq_min_max_gain_db) {
			sampling_frequency_ = default_sample_freq_hz;
			freq_grid_ = *fg;
			current_eq_type_ = eq_t;
			set_eq(freq_grid_, eq_t);
		}
		~eq1() { cleanup_filters_array(); }

		eq_error_t set_eq(freq_grid& fg, filter_type eqt) {
			band_gains_.clear();
			cleanup_filters_array();
			filters_.clear();
			freq_grid_ = fg;

			for(unsigned int i = 0; i < freq_grid_.get_number_of_bands(); i++) {

				eq_double_t wb = conversions::hz_2_rad(
					freq_grid_.get_freqs()[i].max_freq -
					freq_grid_.get_freqs()[i].min_freq,
					sampling_frequency_);

				eq_double_t w0 = conversions::hz_2_rad(
					freq_grid_.get_freqs()[i].center_freq,
					sampling_frequency_);

				switch(eqt) {
					case (butterworth): {
						butterworth_bp_filter* bf =
							new butterworth_bp_filter(
								default_eq_band_filters_order,
								w0,
								wb,
								max_base_gain_db,
								butterworth_band_gain_db,
								min_base_gain_db
							);

						filters_.push_back(bf);
						break;
					}

					case (chebyshev1): {
						chebyshev_type1_bp_filter* cf1 =
							new chebyshev_type1_bp_filter(
								default_eq_band_filters_order,
								w0,
								wb,
								max_base_gain_db,
								chebyshev1_band_base_gain_db,
								min_base_gain_db
							);

						filters_.push_back(cf1);
						break;
					}

					case (chebyshev2): {
						chebyshev_type2_bp_filter* cf2 =
							new chebyshev_type2_bp_filter(
								default_eq_band_filters_order,
								w0,
								wb,
								max_base_gain_db,
								chebyshev2_band_base_gain_db,
								min_base_gain_db
							);

						filters_.push_back(cf2);
						break;
					}

					default:
						current_eq_type_ = none;
						return invalid_input_data_error;

				}
				band_gains_.push_back(max_base_gain_db);
			}

			current_eq_type_ = eqt;
			return no_error;
		}

		eq_error_t set_eq(filter_type eqt)
		{
			return set_eq(freq_grid_, eqt);
		}

		eq_error_t set_sample_rate(eq_double_t sr) {
			eq_error_t err = no_error;
			sampling_frequency_ = sr;
			err = set_eq(freq_grid_, current_eq_type_);

			return err;
		}

		eq_error_t change_gains(std::vector<eq_single_t> band_gains) {
			if(band_gains_.size() == band_gains.size())
				band_gains_ = band_gains;
			else
				return invalid_input_data_error;

			return no_error;
		}

		eq_error_t change_gains_db(std::vector<eq_single_t> band_gains) {
			if(band_gains_.size() == band_gains.size())
				for(unsigned int j = 0; j < get_number_of_bands(); j++)
					band_gains_[j] = conv_.fast_db_2_lin(band_gains[j]);
			else
				return invalid_input_data_error;

			return no_error;
		}

		eq_error_t change_band_gain(unsigned int band_number,
			eq_single_t band_gain) {
			if(band_number < get_number_of_bands())
				band_gains_[band_number] = band_gain;
			else
				return invalid_input_data_error;

			return no_error;
		}

		eq_error_t change_band_gain_db(unsigned int band_number, eq_single_t band_gain) {
			if(band_number < get_number_of_bands())
				band_gains_[band_number] = conv_.fast_db_2_lin(band_gain);
			else
				return invalid_input_data_error;

			return no_error;
		}

		eq_error_t sbs_process_band(unsigned int band_number,	eq_single_t *in, eq_single_t *out) {
			//if(band_number < get_number_of_bands())
				*out = band_gains_[band_number] *
				filters_[band_number]->process(*in);
			//else
				//return invalid_input_data_error;

			return no_error;
		}

		eq_error_t sbs_process(eq_single_t *in, eq_single_t *out) {
			eq_error_t err = no_error;
			eq_single_t acc_out = 0;
			for(unsigned int j = 0, len = get_number_of_bands(); j < len; j++) {
				eq_single_t band_out = 0;
				err = sbs_process_band(j, in, &band_out);
				acc_out += band_out;
			}
			*out = acc_out;

			return err;
		}

		filter_type get_eq_type() { return current_eq_type_; }
		const char* get_string_eq_type() { return get_eq_text(current_eq_type_); }
		unsigned int get_number_of_bands() {
			return freq_grid_.get_number_of_bands();
		}
		const char* get_version() { return eq_version; }
	};

	//!!! New functionality

	// ------------ eq_channel ------------
	// Precomputed equalizer channel, 
	// consists of vector of filters for every gain value
	class eq_channel
	{
		eq_single_t f0_;
		eq_single_t fb_;
		eq_single_t sampling_frequency_;
		eq_single_t min_max_gain_db_;
		eq_single_t gain_step_db_;

		unsigned int current_filter_index_;
		eq_single_t current_gain_db_;

		std::vector<bp_filter*> filters_;
		filter_type current_channel_type_;

		eq_channel() {}

		unsigned int get_flt_index(eq_single_t gain_db) {
			unsigned int number_of_filters = (unsigned int)filters_.size();
			eq_single_t scale_coef = gain_db / min_max_gain_db_;
			return (unsigned int)((number_of_filters / 2) + (number_of_filters / 2)*scale_coef);
		}

		void cleanup_filters_array() {
			for(unsigned int j = 0; j < filters_.size(); j++)
				delete filters_[j];
		}

	public:
		eq_channel(filter_type ft,
			eq_single_t fs, eq_single_t f0, eq_single_t fb,
			eq_single_t min_max_gain_db = p_eq_min_max_gain_db,
			eq_single_t step_db = p_eq_gain_step_db) {

			//Init data fields
			sampling_frequency_ = fs;
			f0_ = f0;
			fb_ = fb;
			min_max_gain_db_ = min_max_gain_db;
			gain_step_db_ = step_db;

			current_gain_db_ = 0;
			current_filter_index_ = 0;

			current_channel_type_ = ft;

			set_channel(current_channel_type_, sampling_frequency_);
		}

		~eq_channel() { cleanup_filters_array(); }

		eq_error_t set_channel(filter_type ft, eq_single_t fs) {

			eq_double_t wb = conversions::hz_2_rad(fb_, sampling_frequency_);
			eq_double_t w0 = conversions::hz_2_rad(f0_, sampling_frequency_);

			for(eq_single_t gain = -min_max_gain_db_; gain <= min_max_gain_db_;
				gain += gain_step_db_) {

				switch(ft) {
					case (butterworth): {
						eq_single_t bw_gain =
							butterworth_bp_filter::compute_bw_gain_db(gain);

						butterworth_bp_filter* bf =
							new butterworth_bp_filter(
								default_eq_band_filters_order,
								w0,
								wb,
								gain,
								bw_gain,
								p_eq_default_gain_db
							);

						filters_.push_back(bf);
						break;
					}
					case (chebyshev1): {
						eq_single_t bw_gain =
							chebyshev_type1_bp_filter::compute_bw_gain_db(gain);

						chebyshev_type1_bp_filter* cf1 =
							new chebyshev_type1_bp_filter(
								default_eq_band_filters_order,
								w0,
								wb,
								gain,
								bw_gain,
								p_eq_default_gain_db
							);

						filters_.push_back(cf1);
						break;
					}
					case (chebyshev2): {
						eq_single_t bw_gain =
							chebyshev_type2_bp_filter::compute_bw_gain_db(gain);

						chebyshev_type2_bp_filter* cf2 =
							new chebyshev_type2_bp_filter(
								default_eq_band_filters_order,
								w0,
								wb,
								gain,
								bw_gain,
								p_eq_default_gain_db
							);

						filters_.push_back(cf2);
						break;
					}
					default: {
						current_channel_type_ = none;
						return invalid_input_data_error;
					}
				}
			}

			//Get current filter index
			current_gain_db_ = 0;
			current_filter_index_ = get_flt_index(current_gain_db_);

			return no_error;
		}

		eq_error_t set_gain_db(eq_single_t db) {
			if(db > -min_max_gain_db_ && db < min_max_gain_db_) {
				current_gain_db_ = db;
				current_filter_index_ = get_flt_index(db);
			} else
				return invalid_input_data_error;

			return no_error;
		}

		eq_error_t sbs_process(eq_single_t *in, eq_single_t *out) {
			*out = filters_[current_filter_index_]->process(*in);
			return no_error;
		}
	};

	// ------------ eq2 ------------
	// Precomputed equalizer 

	class eq2
	{
		conversions conv_;
		eq_double_t sampling_frequency_;
		freq_grid freq_grid_;
		std::vector<eq_channel*> channels_;
		filter_type current_eq_type_;

		void cleanup_channels_array() {
			for(unsigned int j = 0; j < channels_.size(); j++)
				delete channels_[j];
		}

	public:
		eq2(freq_grid &fg, filter_type eq_t) : conv_(eq_min_max_gain_db) {
			sampling_frequency_ = default_sample_freq_hz;
			freq_grid_ = fg;
			current_eq_type_ = eq_t;
			set_eq(freq_grid_, eq_t);
		}
		~eq2() { cleanup_channels_array(); }

		eq_error_t set_eq(const freq_grid& fg, filter_type ft) {
			cleanup_channels_array();
			channels_.clear();
			freq_grid_ = fg;

			for(unsigned int i = 0; i < freq_grid_.get_number_of_bands(); i++) {
				band_freqs b_fres = freq_grid_.get_freqs()[i];

				eq_channel* eq_ch = new eq_channel(ft, sampling_frequency_,
					b_fres.center_freq, b_fres.max_freq - b_fres.min_freq);

				channels_.push_back(eq_ch);
				channels_[i]->set_gain_db(p_eq_default_gain_db);
			}

			current_eq_type_ = ft;
			return no_error;
		}

		eq_error_t set_eq(filter_type ft) {
			eq_error_t err = set_eq(freq_grid_, ft);
			return err;
		}

		eq_error_t set_sample_rate(eq_double_t sr) {
			sampling_frequency_ = sr;
			eq_error_t err = set_eq(current_eq_type_);
			return err;
		}

		eq_error_t change_gains(std::vector<eq_single_t> band_gains) {
			if(channels_.size() == band_gains.size())
				for(unsigned int j = 0; j < channels_.size(); j++)
					channels_[j]->set_gain_db(conv_.fast_lin_2_db(band_gains[j]));
			else
				return invalid_input_data_error;

			return no_error;
		}

		eq_error_t change_gains_db(std::vector<eq_single_t> band_gains) {
			if(channels_.size() == band_gains.size())
				for(unsigned int j = 0; j < channels_.size(); j++)
					channels_[j]->set_gain_db(band_gains[j]);
			else
				return invalid_input_data_error;

			return no_error;
		}

		eq_error_t change_band_gain(unsigned int band_number,
			eq_single_t band_gain) {
			if(band_number < channels_.size())
				channels_[band_number]->set_gain_db(conv_.fast_lin_2_db(band_gain));
			else
				return invalid_input_data_error;

			return no_error;
		}

		eq_error_t change_band_gain_db(unsigned int band_number,
			eq_single_t band_gain) {
			if(band_number < channels_.size())
				channels_[band_number]->set_gain_db(band_gain);
			else
				return invalid_input_data_error;

			return no_error;
		}

		eq_error_t sbs_process_band(unsigned int band_number,
			eq_single_t *in, eq_single_t *out) {
			if(band_number < get_number_of_bands())
				channels_[band_number]->sbs_process(in, out);
			else
				return invalid_input_data_error;

			return no_error;
		}

		eq_error_t sbs_process(eq_single_t *in, eq_single_t *out) {
			eq_error_t err = no_error;
			eq_single_t in_out = *in;
			for(unsigned int i = 0; i < get_number_of_bands(); i++)
				err = sbs_process_band(i, &in_out, &in_out);

			*out = in_out;

			return err;
		}

		filter_type get_eq_type() { return current_eq_type_; }
		const char* get_string_eq_type() { return get_eq_text(current_eq_type_); }
		unsigned int get_number_of_bands() {
			return freq_grid_.get_number_of_bands();
		}
		const char* get_version() { return eq_version; }
	};

} //namespace orfanidis_eq
#endif //ORFANIDIS_EQ_H_