/*
 * Brickworks
 *
 * Copyright (C) 2023 Orastron Srl unipersonale
 *
 * Brickworks is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, version 3 of the License.
 *
 * Brickworks is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Brickworks.  If not, see <http://www.gnu.org/licenses/>.
 *
 * File author: Stefano D'Angelo
 */

/*!
 *  module_type {{{ dsp }}}
 *  version {{{ 1.0.0 }}}
 *  requires {{{
 *    bw_buf bw_common bw_delay bw_gain bw_math bw_one_pole
 *  }}}
 *  description {{{
 *    Comb filter / delay effect with feedforward and feedback paths.
 *
 *    Essentially an implementation of the structure described in
 *
 *    J. Dattorro, "Effect Design, Part 2: Delay-Line Modulation and Chorus",
 *    J. Audio Eng. Soc., vol. 45, no. 10, pp. 764-788, October 1997.
 *
 *    Unlike in the original paper, the feedback signal is not subtracted but
 *    rather added to the input. 
 *  }}}
 *  changelog {{{
 *    <ul>
 *      <li>Version <strong>1.0.0</strong>:
 *        <ul>
 *          <li>Added initial value argument in
 *              <code>bw_chorus_reset_state()</code>.</li>
 *          <li>Added overloaded C++ <code>reset()</code> functions taking
 *              arrays as arguments.</li>
 *          <li>Now using <code>size_t</code> instead of
 *              <code>BW_SIZE_T</code>.</li>
 *          <li><code>bw_comb_process()</code> and
 *              <code>bw_comb_process_multi()</code> now use <code>size_t</code>
 *              to count samples and channels.</li>
 *          <li>Added more <code>const</code> and <code>BW_RESTRICT</code>
 *              specifiers to input arguments and implementation.</li>
 *          <li>Moved C++ code to C header.</li>
 *          <li>Added overloaded C++ <code>process()</code> function taking
 *              C-style arrays as arguments.</li>
 *          <li>Removed usage of reserved identifiers.</li>
 *        </ul>
 *      </li>
 *      <li>Version <strong>0.6.0</strong>:
 *        <ul>
 *          <li>Removed dependency on bw_config.</li>
 *        </ul>
 *      </li>
 *      <li>Version <strong>0.5.0</strong>:
 *        <ul>
 *          <li>Added <code>bw_comb_process_multi()</code>.</li>
 *          <li>Updated mem_req/set API.</li>
 *          <li>Added C++ wrapper.</li>
 *        </ul>
 *      </li>
 *    </ul>
 *      <li>Version <strong>0.4.0</strong>:
 *        <ul>
 *          <li>First release.</li>
 *        </ul>
 *      </li>
 *    </ul>
 *  }}}
 */

#ifndef BW_COMB_H
#define BW_COMB_H

#include <bw_common.h>

#ifdef __cplusplus
extern "C" {
#endif

/*! api {{{
 *    #### bw_comb_coeffs
 *  ```>>> */
typedef struct bw_comb_coeffs bw_comb_coeffs;
/*! <<<```
 *    Coefficients and related.
 *
 *    #### bw_comb_state
 *  ```>>> */
typedef struct bw_comb_state bw_comb_state;
/*! <<<```
 *    Internal state and related.
 *
 *    #### bw_comb_init()
 *  ```>>> */
static inline void bw_comb_init(bw_comb_coeffs *BW_RESTRICT coeffs, float max_delay);
/*! <<<```
 *    Initializes input parameter values in `coeffs` using `max_delay` (s) as
 *    the maximum delay time.
 *
 *    #### bw_comb_set_sample_rate()
 *  ```>>> */
static inline void bw_comb_set_sample_rate(bw_comb_coeffs *BW_RESTRICT coeffs, float sample_rate);
/*! <<<```
 *    Sets the `sample_rate` (Hz) value in `coeffs`.
 *
 *    #### bw_comb_mem_req()
 *  ```>>> */
static inline size_t bw_comb_mem_req(const bw_comb_coeffs *BW_RESTRICT coeffs);
/*! <<<```
 *    Returns the size, in bytes, of contiguous memory to be supplied to
 *    `bw_comb_mem_set()` using `coeffs`.
 *
 *    #### bw_comb_mem_set()
 *  ```>>> */
static inline void bw_comb_mem_set(const bw_comb_coeffs *BW_RESTRICT coeffs, bw_comb_state *BW_RESTRICT state, void *BW_RESTRICT mem);
/*! <<<```
 *    Associates the contiguous memory block `mem` to the given `state`.
 *
 *    #### bw_comb_reset_coeffs()
 *  ```>>> */
static inline void bw_comb_reset_coeffs(bw_comb_coeffs *BW_RESTRICT coeffs);
/*! <<<```
 *    Resets coefficients in `coeffs` to assume their target values.
 *
 *    #### bw_comb_reset_state()
 *  ```>>> */
static inline void bw_comb_reset_state(const bw_comb_coeffs *BW_RESTRICT coeffs, bw_comb_state *BW_RESTRICT state, float x_0);
/*! <<<```
 *    Resets the given `state` to its initial values using the given `coeffs`
 *    and the quiescent/initial input value `x_0`.
 *
 *    #### bw_comb_update_coeffs_ctrl()
 *  ```>>> */
static inline void bw_comb_update_coeffs_ctrl(bw_comb_coeffs *BW_RESTRICT coeffs);
/*! <<<```
 *    Triggers control-rate update of coefficients in `coeffs`.
 *
 *    #### bw_comb_update_coeffs_audio()
 *  ```>>> */
static inline void bw_comb_update_coeffs_audio(bw_comb_coeffs *BW_RESTRICT coeffs);
/*! <<<```
 *    Triggers audio-rate update of coefficients in `coeffs`.
 *
 *    #### bw_comb_process1()
 *  ```>>> */
static inline float bw_comb_process1(const bw_comb_coeffs *BW_RESTRICT coeffs, bw_comb_state *BW_RESTRICT state, float x);
/*! <<<```
 *    Processes one input sample `x` using `coeffs`, while using and updating
 *    `state`. Returns the corresponding output sample.
 *
 *    #### bw_comb_process()
 *  ```>>> */
static inline void bw_comb_process(bw_comb_coeffs *BW_RESTRICT coeffs, bw_comb_state *BW_RESTRICT state, const float *x, float *y, size_t n_samples);
/*! <<<```
 *    Processes the first `n_samples` of the input buffer `x` and fills the
 *    first `n_samples` of the output buffer `y`, while using and updating both
 *    `coeffs` and `state` (control and audio rate).
 *
 *    #### bw_comb_process_multi()
 *  ```>>> */
static inline void bw_comb_process_multi(bw_comb_coeffs *BW_RESTRICT coeffs, bw_comb_state *BW_RESTRICT const *BW_RESTRICT state, const float * const *x, float * const *y, size_t n_channels, size_t n_samples);
/*! <<<```
 *    Processes the first `n_samples` of the `n_channels` input buffers `x` and
 *    fills the first `n_samples` of the `n_channels` output buffers `y`, while
 *    using and updating both the common `coeffs` and each of the `n_channels`
 *    `state`s (control and audio rate).
 *
 *    #### bw_comb_set_delay_ff()
 *  ```>>> */
static inline void bw_comb_set_delay_ff(bw_comb_coeffs *BW_RESTRICT coeffs, float value);
/*! <<<```
 *    Sets the feedforward delay time `value` (s) in `coeffs`.
 *
 *    Default value: `0.f`.
 *
 *    #### bw_comb_set_delay_fb()
 *  ```>>> */
static inline void bw_comb_set_delay_fb(bw_comb_coeffs *BW_RESTRICT coeffs, float value);
/*! <<<```
 *    Sets the feedback delay time `value` (s) in `coeffs`.
 *
 *    Default value: `0.f`.
 *
 *    #### bw_comb_set_coeff_blend()
 *  ```>>> */
static inline void bw_comb_set_coeff_blend(bw_comb_coeffs *BW_RESTRICT coeffs, float value);
/*! <<<```
 *    Sets the blend coefficient `value` in `coeffs`.
 *
 *    Default value: `1.f`.
 *
 *    #### bw_comb_set_coeff_ff()
 *  ```>>> */
static inline void bw_comb_set_coeff_ff(bw_comb_coeffs *BW_RESTRICT coeffs, float value);
/*! <<<```
 *    Sets the feedforward coefficient `value` in `coeffs`.
 *
 *    Default value: `0.f`.
 *
 *    #### bw_comb_set_coeff_fb()
 *  ```>>> */
static inline void bw_comb_set_coeff_fb(bw_comb_coeffs *BW_RESTRICT coeffs, float value);
/*! <<<```
 *    Sets the feedback coefficient `value` in `coeffs`.
 *
 *    Default value: `0.f`.
 *  }}} */

#ifdef __cplusplus
}
#endif

/*** Implementation ***/

/* WARNING: This part of the file is not part of the public API. Its content may
 * change at any time in future versions. Please, do not use it directly. */

#include <bw_delay.h>
#include <bw_gain.h>
#include <bw_one_pole.h>
#include <bw_math.h>

#ifdef __cplusplus
extern "C" {
#endif

struct bw_comb_coeffs {
	// Sub-components
	bw_delay_coeffs		delay_coeffs;
	bw_gain_coeffs		blend_coeffs;
	bw_gain_coeffs		ff_coeffs;
	bw_gain_coeffs		fb_coeffs;
	bw_one_pole_coeffs	smooth_coeffs;
	bw_one_pole_state	smooth_delay_ff_state;
	bw_one_pole_state	smooth_delay_fb_state;

	// Coefficients
	float			fs;

	size_t			dffi;
	float			dfff;
	size_t			dfbi;
	float			dfbf;

	// Parameters
	float			delay_ff;
	float			delay_fb;
};

struct bw_comb_state {
	// Sub-components
	bw_delay_state		delay_state;
};

static inline void bw_comb_init(bw_comb_coeffs *BW_RESTRICT coeffs, float max_delay) {
	bw_delay_init(&coeffs->delay_coeffs, max_delay);
	bw_gain_init(&coeffs->blend_coeffs);
	bw_gain_init(&coeffs->ff_coeffs);
	bw_gain_init(&coeffs->fb_coeffs);
	bw_one_pole_init(&coeffs->smooth_coeffs);
	bw_one_pole_set_tau(&coeffs->smooth_coeffs, 0.05f);
	bw_one_pole_set_sticky_thresh(&coeffs->smooth_coeffs, 1e-6f);
	bw_gain_set_gain_lin(&coeffs->ff_coeffs, 0.f);
	bw_gain_set_gain_lin(&coeffs->fb_coeffs, 0.f);
	coeffs->delay_ff = 0.f;
	coeffs->delay_fb = 0.f;
}

static inline void bw_comb_set_sample_rate(bw_comb_coeffs *BW_RESTRICT coeffs, float sample_rate) {
	bw_delay_set_sample_rate(&coeffs->delay_coeffs, sample_rate);
	bw_gain_set_sample_rate(&coeffs->blend_coeffs, sample_rate); 
	bw_gain_set_sample_rate(&coeffs->ff_coeffs, sample_rate); 
	bw_gain_set_sample_rate(&coeffs->fb_coeffs, sample_rate); 
	bw_one_pole_set_sample_rate(&coeffs->smooth_coeffs, sample_rate);
	bw_one_pole_reset_coeffs(&coeffs->smooth_coeffs);
	coeffs->fs = sample_rate;
}

static inline size_t bw_comb_mem_req(const bw_comb_coeffs *BW_RESTRICT coeffs) {
	return bw_delay_mem_req(&coeffs->delay_coeffs);
}

static inline void bw_comb_mem_set(const bw_comb_coeffs *BW_RESTRICT coeffs, bw_comb_state *BW_RESTRICT state, void *BW_RESTRICT mem) {
	bw_delay_mem_set(&coeffs->delay_coeffs, &state->delay_state, mem);
}

static inline void bw_comb_do_update_coeffs(bw_comb_coeffs *BW_RESTRICT coeffs, char force) {
	float delay_ff_cur = bw_one_pole_get_y_z1(&coeffs->smooth_delay_ff_state);
	float delay_fb_cur = bw_one_pole_get_y_z1(&coeffs->smooth_delay_fb_state);
	if (force || delay_ff_cur != coeffs->delay_ff) {
		delay_ff_cur = bw_one_pole_process1_sticky_abs(&coeffs->smooth_coeffs, &coeffs->smooth_delay_ff_state, coeffs->delay_ff);
		const size_t len = bw_delay_get_length(&coeffs->delay_coeffs);
		const float dff = bw_maxf(coeffs->fs * delay_ff_cur, 0.f);
		float dffif;
		bw_intfracf(dff, &dffif, &coeffs->dfff);
		coeffs->dffi = (size_t)dffif;
		if (coeffs->dffi >= len) {
			coeffs->dffi = len;
			coeffs->dfff = 0.f;
		}
	}
	if (force || delay_fb_cur != coeffs->delay_fb) {
		delay_fb_cur = bw_one_pole_process1_sticky_abs(&coeffs->smooth_coeffs, &coeffs->smooth_delay_fb_state, coeffs->delay_fb);
		const size_t len = bw_delay_get_length(&coeffs->delay_coeffs);
		const float dfb = bw_maxf(coeffs->fs * delay_fb_cur, 1.f) - 1.f;
		float dfbif;
		bw_intfracf(dfb, &dfbif, &coeffs->dfbf);
		coeffs->dfbi = (size_t)dfbif;
		if (coeffs->dfbi >= len) {
			coeffs->dfbi = len;
			coeffs->dfbf = 0.f;
		}
	}
}

static inline void bw_comb_reset_coeffs(bw_comb_coeffs *BW_RESTRICT coeffs) {
	bw_delay_reset_coeffs(&coeffs->delay_coeffs);
	bw_gain_reset_coeffs(&coeffs->blend_coeffs);
	bw_gain_reset_coeffs(&coeffs->ff_coeffs);
	bw_gain_reset_coeffs(&coeffs->fb_coeffs);
	bw_one_pole_reset_state(&coeffs->smooth_coeffs, &coeffs->smooth_delay_ff_state, coeffs->delay_ff);
	bw_one_pole_reset_state(&coeffs->smooth_coeffs, &coeffs->smooth_delay_fb_state, coeffs->delay_fb);
	bw_comb_do_update_coeffs(coeffs, 1);
}

static inline void bw_comb_reset_state(const bw_comb_coeffs *BW_RESTRICT coeffs, bw_comb_state *BW_RESTRICT state, float x_0) {
	bw_delay_reset_state(&coeffs->delay_coeffs, &state->delay_state, x_0);
}

static inline void bw_comb_update_coeffs_ctrl(bw_comb_coeffs *BW_RESTRICT coeffs) {
	bw_gain_update_coeffs_ctrl(&coeffs->blend_coeffs);
	bw_gain_update_coeffs_ctrl(&coeffs->ff_coeffs);
	bw_gain_update_coeffs_ctrl(&coeffs->fb_coeffs);
}

static inline void bw_comb_update_coeffs_audio(bw_comb_coeffs *BW_RESTRICT coeffs) {
	bw_gain_update_coeffs_audio(&coeffs->blend_coeffs);
	bw_gain_update_coeffs_audio(&coeffs->ff_coeffs);
	bw_gain_update_coeffs_audio(&coeffs->fb_coeffs);
	bw_comb_do_update_coeffs(coeffs, 0);
}

static inline float bw_comb_process1(const bw_comb_coeffs *BW_RESTRICT coeffs, bw_comb_state *BW_RESTRICT state, float x) {
	const float fb = bw_delay_read(&coeffs->delay_coeffs, &state->delay_state, coeffs->dfbi, coeffs->dfbf);
	const float v = x + bw_gain_process1(&coeffs->fb_coeffs, fb);
	bw_delay_write(&coeffs->delay_coeffs, &state->delay_state, v);
	const float ff = bw_delay_read(&coeffs->delay_coeffs, &state->delay_state, coeffs->dffi, coeffs->dfff);
	return bw_gain_process1(&coeffs->blend_coeffs, v) + bw_gain_process1(&coeffs->ff_coeffs, ff);
}

static inline void bw_comb_process(bw_comb_coeffs *BW_RESTRICT coeffs, bw_comb_state *BW_RESTRICT state, const float *x, float *y, size_t n_samples) {
	bw_comb_update_coeffs_ctrl(coeffs);
	for (size_t i = 0; i < n_samples; i++) {
		bw_comb_update_coeffs_audio(coeffs);
		y[i] = bw_comb_process1(coeffs, state, x[i]);
	}
}

static inline void bw_comb_process_multi(bw_comb_coeffs *BW_RESTRICT coeffs, bw_comb_state *BW_RESTRICT const *BW_RESTRICT state, const float * const *x, float * const *y, size_t n_channels, size_t n_samples) {
	bw_comb_update_coeffs_ctrl(coeffs);
	for (size_t i = 0; i < n_samples; i++) {
		bw_comb_update_coeffs_audio(coeffs);
		for (size_t j = 0; j < n_channels; j++)
			y[j][i] = bw_comb_process1(coeffs, state[j], x[j][i]);
	}
}

static inline void bw_comb_set_delay_ff(bw_comb_coeffs *BW_RESTRICT coeffs, float value) {
	coeffs->delay_ff = value;
}

static inline void bw_comb_set_delay_fb(bw_comb_coeffs *BW_RESTRICT coeffs, float value) {
	coeffs->delay_fb = value;
}

static inline void bw_comb_set_coeff_blend(bw_comb_coeffs *BW_RESTRICT coeffs, float value) {
	bw_gain_set_gain_lin(&coeffs->blend_coeffs, value);
}

static inline void bw_comb_set_coeff_ff(bw_comb_coeffs *BW_RESTRICT coeffs, float value) {
	bw_gain_set_gain_lin(&coeffs->ff_coeffs, value);
}

static inline void bw_comb_set_coeff_fb(bw_comb_coeffs *BW_RESTRICT coeffs, float value) {
	bw_gain_set_gain_lin(&coeffs->fb_coeffs, value);
}

#ifdef __cplusplus
}

#include <array>

namespace Brickworks {

/*** Public C++ API ***/

/*! api_cpp {{{
 *    ##### Brickworks::Comb
 *  ```>>> */
template<size_t N_CHANNELS>
class Comb {
public:
	Comb(float maxDelay = 1.f);
	~Comb();

	void setSampleRate(float sampleRate);
	void reset(float x_0 = 0.f);
	void reset(const float *BW_RESTRICT x_0);
	void reset(const std::array<float, N_CHANNELS> x_0);
	void process(
		const float * const *x,
		float * const *y,
		size_t nSamples);
	void process(
		const std::array<const float *, N_CHANNELS> x,
		const std::array<float *, N_CHANNELS> y,
		size_t nSamples);

	void setDelayFF(float value);
	void setDelayFB(float value);
	void setCoeffBlend(float value);
	void setCoeffFF(float value);
	void setCoeffFB(float value);
/*! <<<...
 *  }
 *  ```
 *  }}} */

/*** Implementation ***/

/* WARNING: This part of the file is not part of the public API. Its content may
 * change at any time in future versions. Please, do not use it directly. */

private:
	bw_comb_coeffs	 coeffs;
	bw_comb_state	 states[N_CHANNELS];
	bw_comb_state	*BW_RESTRICT statesP[N_CHANNELS];
	void		*BW_RESTRICT mem;
};

template<size_t N_CHANNELS>
inline Comb<N_CHANNELS>::Comb(float maxDelay) {
	bw_comb_init(&coeffs, maxDelay);
	for (size_t i = 0; i < N_CHANNELS; i++)
		statesP[i] = states + i;
	mem = nullptr;
}

template<size_t N_CHANNELS>
inline Comb<N_CHANNELS>::~Comb() {
	if (mem != nullptr)
		operator delete(mem);
}

template<size_t N_CHANNELS>
inline void Comb<N_CHANNELS>::setSampleRate(float sampleRate) {
	bw_comb_set_sample_rate(&coeffs, sampleRate);
	size_t req = bw_comb_mem_req(&coeffs);
	if (mem != nullptr)
		operator delete(mem);
	mem = operator new(req * N_CHANNELS);
	void *m = mem;
	for (size_t i = 0; i < N_CHANNELS; i++, m = static_cast<char *>(m) + req)
		bw_comb_mem_set(&coeffs, states + i, m);
}

template<size_t N_CHANNELS>
inline void Comb<N_CHANNELS>::reset(float x_0) {
	bw_comb_reset_coeffs(&coeffs);
	for (size_t i = 0; i < N_CHANNELS; i++)
		bw_comb_reset_state(&coeffs, states + i, x_0);
}

template<size_t N_CHANNELS>
inline void Comb<N_CHANNELS>::reset(const float *BW_RESTRICT x_0) {
	bw_comb_reset_coeffs(&coeffs);
	for (size_t i = 0; i < N_CHANNELS; i++)
		bw_comb_reset_state(&coeffs, states + i, x_0[i]);
}

template<size_t N_CHANNELS>
inline void Comb<N_CHANNELS>::reset(const std::array<float, N_CHANNELS> x_0) {
	reset(x_0.data());
}

template<size_t N_CHANNELS>
inline void Comb<N_CHANNELS>::process(
		const float * const *x,
		float * const *y,
		size_t nSamples) {
	bw_comb_process_multi(&coeffs, statesP, x, y, N_CHANNELS, nSamples);
}

template<size_t N_CHANNELS>
inline void Comb<N_CHANNELS>::process(
		const std::array<const float *, N_CHANNELS> x,
		const std::array<float *, N_CHANNELS> y,
		size_t nSamples) {
	process(x.data(), y.data(), nSamples);
}

template<size_t N_CHANNELS>
inline void Comb<N_CHANNELS>::setDelayFF(float value) {
	bw_comb_set_delay_ff(&coeffs, value);
}

template<size_t N_CHANNELS>
inline void Comb<N_CHANNELS>::setDelayFB(float value) {
	bw_comb_set_delay_fb(&coeffs, value);
}

template<size_t N_CHANNELS>
inline void Comb<N_CHANNELS>::setCoeffBlend(float value) {
	bw_comb_set_coeff_blend(&coeffs, value);
}

template<size_t N_CHANNELS>
inline void Comb<N_CHANNELS>::setCoeffFF(float value) {
	bw_comb_set_coeff_ff(&coeffs, value);
}

template<size_t N_CHANNELS>
inline void Comb<N_CHANNELS>::setCoeffFB(float value) {
	bw_comb_set_coeff_fb(&coeffs, value);
}

}
#endif

#endif