//* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Rubber Band Library
    An audio time-stretching and pitch-shifting library.
    Copyright 2007-2021 Particular Programs Ltd.

    This program 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; either version 2 of the
    License, or (at your option) any later version.  See the file
    COPYING included with this distribution for more information.

    Alternatively, if you have a valid commercial licence for the
    Rubber Band Library obtained by agreement with the copyright
    holders, you may redistribute and/or modify it under the terms
    described in that licence.

    If you wish to distribute code using the Rubber Band Library
    under terms other than those of the GNU General Public License,
    you must obtain a valid commercial licence before doing so.
*/

#include "BQResampler.h"

#include <cmath>

#include <iostream>

#include "system/Allocators.h"
#include "system/VectorOps.h"

#define BQ_R__ R__

using std::vector;
using std::cerr;
using std::endl;
using std::min;
using std::max;

namespace RubberBand {

BQResampler::BQResampler(Parameters parameters, int channels) :
    m_qparams(parameters.quality),
    m_dynamism(parameters.dynamism),
    m_ratio_change(parameters.ratioChange),
    m_debug_level(parameters.debugLevel),
    m_initial_rate(parameters.referenceSampleRate),
    m_channels(channels),
    m_fade_count(0),
    m_initialised(false)
{
    if (m_debug_level > 0) {
        cerr << "BQResampler::BQResampler: "
             << (m_dynamism == RatioOftenChanging ? "often-changing" : "mostly-fixed")
             << ", "
             << (m_ratio_change == SmoothRatioChange ? "smooth" : "sudden")
             << " ratio changes, ref " << m_initial_rate << " Hz" << endl;
    }
    
    if (m_dynamism == RatioOftenChanging) {
        m_proto_length = m_qparams.proto_p * m_qparams.p_multiple + 1;
        if (m_debug_level > 0) {
            cerr << "BQResampler: creating prototype filter of length "
                 << m_proto_length << endl;
        }
        m_prototype = make_filter(m_proto_length, m_qparams.proto_p);
        m_prototype.push_back(0.0); // interpolate without fear
    }

    int phase_reserve = 2 * int(round(m_initial_rate));
    int buffer_reserve = 1000 * m_channels;
    m_state_a.phase_info.reserve(phase_reserve);
    m_state_a.buffer.reserve(buffer_reserve);

    if (m_dynamism == RatioOftenChanging) {
        m_state_b.phase_info.reserve(phase_reserve);
        m_state_b.buffer.reserve(buffer_reserve);
    }

    m_s = &m_state_a;
    m_fade = &m_state_b;
}

BQResampler::BQResampler(const BQResampler &other) :
    m_qparams(other.m_qparams),
    m_dynamism(other.m_dynamism),
    m_ratio_change(other.m_ratio_change),
    m_debug_level(other.m_debug_level),
    m_initial_rate(other.m_initial_rate),
    m_channels(other.m_channels),
    m_state_a(other.m_state_a),
    m_state_b(other.m_state_b),
    m_fade_count(other.m_fade_count),
    m_prototype(other.m_prototype),
    m_proto_length(other.m_proto_length),
    m_initialised(other.m_initialised)
{
    if (other.m_s == &(other.m_state_a)) {
        m_s = &m_state_a;
        m_fade = &m_state_b;
    } else {
        m_s = &m_state_b;
        m_fade = &m_state_a;
    }
}

void
BQResampler::reset()
{
    m_initialised = false;
    m_fade_count = 0;
}

BQResampler::QualityParams::QualityParams(Quality q)
{
    switch (q) {
    case Fastest:
        p_multiple = 12;
        proto_p = 160;
        k_snr = 70.0;
        k_transition = 0.2;
        cut = 0.9;
        break;
    case FastestTolerable:
        p_multiple = 62;
        proto_p = 160;
        k_snr = 90.0;
        k_transition = 0.05;
        cut = 0.975;
        break;
    case Best:
        p_multiple = 122;
        proto_p = 800;
        k_snr = 100.0;
        k_transition = 0.01;
        cut = 0.995;
        break;
    }
}
    
int
BQResampler::resampleInterleaved(float *const out,
                                 int outspace,
                                 const float *const in,
                                 int incount,
                                 double ratio,
                                 bool final) {

    int fade_length = round(m_initial_rate / 1000.0);
    if (fade_length < 6) {
        fade_length = 6;
    }
    int max_fade = min(outspace, int(floor(incount * ratio))) / 2;
    if (fade_length > max_fade) {
        fade_length = max_fade;
    }
        
    if (!m_initialised) {
        state_for_ratio(*m_s, ratio, *m_fade);
        m_initialised = true;
    } else if (ratio != m_s->parameters.ratio) {
        state *tmp = m_fade;
        m_fade = m_s;
        m_s = tmp;
        state_for_ratio(*m_s, ratio, *m_fade);
        if (m_ratio_change == SmoothRatioChange) {
            if (m_debug_level > 0) {
                cerr << "BQResampler: ratio changed, beginning fade of length "
                     << fade_length << endl;
            }
            m_fade_count = fade_length;
        }
    }

    int i = 0, o = 0;
    int bufsize = m_s->buffer.size();

    int incount_samples = incount * m_channels;
    int outspace_samples = outspace * m_channels;
    
    while (o < outspace_samples) {
        while (i < incount_samples && m_s->fill < bufsize) {
            m_s->buffer[m_s->fill++] = in[i++];
        }
        if (m_s->fill == bufsize) {
            out[o++] = reconstruct_one(m_s);
        } else if (final && m_s->fill > m_s->centre) {
            out[o++] = reconstruct_one(m_s);
        } else if (final && m_s->fill == m_s->centre &&
                   m_s->current_phase != m_s->initial_phase) {
            out[o++] = reconstruct_one(m_s);
        } else {
            break;
        }
    }

    int fbufsize = m_fade->buffer.size();
    int fi = 0, fo = 0;
    while (fo < o && m_fade_count > 0) {
        while (fi < incount_samples && m_fade->fill < fbufsize) {
            m_fade->buffer[m_fade->fill++] = in[fi++];
        }
        if (m_fade->fill == fbufsize) {
            double r = reconstruct_one(m_fade);
            double fadeWith = out[fo];
            double extent = double(m_fade_count - 1) / double(fade_length);
            double mixture = 0.5 * (1.0 - cos(M_PI * extent));
            double mixed = r * mixture + fadeWith * (1.0 - mixture);
            out[fo] = mixed;
            ++fo;
            if (m_fade->current_channel == 0) {
                --m_fade_count;
            }
        } else {
            break;
        }
    }
        
    return o / m_channels;
}

double
BQResampler::getEffectiveRatio(double ratio) const {
    if (m_initialised && ratio == m_s->parameters.ratio) {
        return m_s->parameters.effective;
    } else {
        return pick_params(ratio).effective;
    }
}
    
int
BQResampler::gcd(int a, int b) const
{
    int c = a % b;
    if (c == 0) return b;
    else return gcd(b, c);
}

double
BQResampler::bessel0(double x) const
{
    static double facsquared[] = {
        0.0, 1.0, 4.0, 36.0,
        576.0, 14400.0, 518400.0, 25401600.0,
        1625702400.0, 131681894400.0, 1.316818944E13, 1.59335092224E15,
        2.29442532803E17, 3.87757880436E19, 7.60005445655E21,
        1.71001225272E24, 4.37763136697E26, 1.26513546506E29,
        4.09903890678E31, 1.47975304535E34
    };
    static int nterms = sizeof(facsquared) / sizeof(facsquared[0]);
    double b = 1.0;
    for (int n = 1; n < nterms; ++n) {
        double ff = facsquared[n];
        double term = pow(x / 2.0, n * 2.0) / ff;
        b += term;
    }
    return b;
}

vector<double>
BQResampler::kaiser(double beta, int len) const
{
    double denominator = bessel0(beta);
    int half = (len % 2 == 0 ? len/2 : (len+1)/2);
    vector<double> v(len, 0.0);
    for (int n = 0; n < half; ++n) {
        double k = (2.0 * n) / (len-1) - 1.0;
        v[n] = bessel0 (beta * sqrt(1.0 - k*k)) / denominator;
    }
    for (int n = half; n < len; ++n) {
        v[n] = v[len-1 - n];
    }
    return v;
}

void
BQResampler::kaiser_params(double attenuation,
                           double transition,
                           double &beta,
                           int &len) const
{
    if (attenuation > 21.0) {
        len = 1 + ceil((attenuation - 7.95) / (2.285 * transition));
    } else {
        len = 1 + ceil(5.79 / transition);
    }
    beta = 0.0;
    if (attenuation > 50.0) {
        beta = 0.1102 * (attenuation - 8.7);
    } else if (attenuation > 21.0) {
        beta = 0.5842 * (pow (attenuation - 21.0, 0.4)) +
            0.07886 * (attenuation - 21.0);
    }
}

vector<double>
BQResampler::kaiser_for(double attenuation,
                        double transition,
                        int minlen,
                        int maxlen) const
{
    double beta;
    int m;
    kaiser_params(attenuation, transition, beta, m);
    int mb = m;
    if (maxlen > 0 && mb > maxlen - 1) {
        mb = maxlen - 1;
    } else if (minlen > 0 && mb < minlen) {
        mb = minlen;
    }
    if (mb % 2 == 0) ++mb;
    if (m_debug_level > 0) {
        cerr << "BQResampler: window attenuation " << attenuation
             << ", transition " << transition
             << " -> length " << m << " adjusted to " << mb
             << ", beta " << beta << endl;
    }
    return kaiser(beta, mb);
}
    
void
BQResampler::sinc_multiply(double peak_to_zero, vector<double> &buf) const
{
    int len = int(buf.size());
    if (len < 2) return;

    int left = len / 2;
    int right = (len + 1) / 2;
    double m = M_PI / peak_to_zero;

    for (int i = 1; i <= right; ++i) {
        double x = i * m;
        double sinc = sin(x) / x;
        if (i <= left) {
            buf[left - i] *= sinc;
        }
        if (i < right) {
            buf[i + left] *= sinc;
        }
    }
}

BQResampler::params
BQResampler::fill_params(double ratio, int num, int denom) const
{
    params p;
    int g = gcd (num, denom);
    p.ratio = ratio;
    p.numerator = num / g;
    p.denominator = denom / g;
    p.effective = double(p.numerator) / double(p.denominator);
    p.peak_to_zero = max(p.denominator, p.numerator);
    p.peak_to_zero /= m_qparams.cut;
    p.scale = double(p.numerator) / double(p.peak_to_zero);

    if (m_debug_level > 0) {
        cerr << "BQResampler: ratio " << p.ratio
             << " -> fraction " << p.numerator << "/" << p.denominator
             << " with error " << p.effective - p.ratio
             << endl;
        cerr << "BQResampler: peak-to-zero " << p.peak_to_zero
             << ", scale " << p.scale
             << endl;
    }
    
    return p;
}
    
BQResampler::params
BQResampler::pick_params(double ratio) const
{
    // Farey algorithm, see
    // https://www.johndcook.com/blog/2010/10/20/best-rational-approximation/
    int max_denom = 192000;
    double a = 0.0, b = 1.0, c = 1.0, d = 0.0;
    double pa = a, pb = b, pc = c, pd = d;
    double eps = 1e-9;
    while (b <= max_denom && d <= max_denom) {
        double mediant = (a + c) / (b + d);
        if (fabs(ratio - mediant) < eps) {
            if (b + d <= max_denom) {
                return fill_params(ratio, a + c, b + d);
            } else if (d > b) {
                return fill_params(ratio, c, d);
            } else {
                return fill_params(ratio, a, b);
            }
        }
        if (ratio > mediant) {
            pa = a; pb = b;
            a += c; b += d;
        } else {
            pc = c; pd = d;
            c += a; d += b;
        }
    }
    if (fabs(ratio - (pc / pd)) < fabs(ratio - (pa / pb))) {
        return fill_params(ratio, pc, pd);
    } else {
        return fill_params(ratio, pa, pb);
    }
}

void
BQResampler::phase_data_for(vector<BQResampler::phase_rec> &target_phase_data,
                            floatbuf &target_phase_sorted_filter,
                            int filter_length,
                            const vector<double> *filter,
                            int initial_phase,
                            int input_spacing,
                            int output_spacing) const
{
    target_phase_data.clear();
    target_phase_data.reserve(input_spacing);
        
    for (int p = 0; p < input_spacing; ++p) {
        int next_phase = p - output_spacing;
        while (next_phase < 0) next_phase += input_spacing;
        next_phase %= input_spacing;
        double dspace = double(input_spacing);
        int zip_length = ceil(double(filter_length - p) / dspace);
        int drop = ceil(double(max(0, output_spacing - p)) / dspace);
        phase_rec phase;
        phase.next_phase = next_phase;
        phase.drop = drop;
        phase.length = zip_length;
        phase.start_index = 0; // we fill this in below if needed
        target_phase_data.push_back(phase);
    }

    if (m_dynamism == RatioMostlyFixed) {
        if (!filter) throw std::logic_error("filter required at phase_data_for in RatioMostlyFixed mode");
        target_phase_sorted_filter.clear();
        target_phase_sorted_filter.reserve(filter_length);
        for (int p = initial_phase; ; ) {
            phase_rec &phase = target_phase_data[p];
            phase.start_index = target_phase_sorted_filter.size();
            for (int i = 0; i < phase.length; ++i) {
                target_phase_sorted_filter.push_back
                    ((*filter)[i * input_spacing + p]);
            }
            p = phase.next_phase;
            if (p == initial_phase) {
                break;
            }
        }
    }
}

vector<double>
BQResampler::make_filter(int filter_length, double peak_to_zero) const
{
    vector<double> filter;
    filter.reserve(filter_length);

    vector<double> kaiser = kaiser_for(m_qparams.k_snr, m_qparams.k_transition,
                                       1, filter_length);
    int k_length = kaiser.size();

    if (k_length == filter_length) {
        sinc_multiply(peak_to_zero, kaiser);
        return kaiser;
    } else {
        kaiser.push_back(0.0);
        double m = double(k_length - 1) / double(filter_length - 1);
        for (int i = 0; i < filter_length; ++i) {
            double ix = i * m;
            int iix = floor(ix);
            double remainder = ix - iix;
            double value = 0.0;
            value += kaiser[iix] * (1.0 - remainder);
            value += kaiser[iix+1] * remainder;
            filter.push_back(value);
        }
        sinc_multiply(peak_to_zero, filter);
        return filter;
    }
}

void
BQResampler::state_for_ratio(BQResampler::state &target_state,
                             double ratio,
                             const BQResampler::state &BQ_R__ prev_state) const
{
    params parameters = pick_params(ratio);
    target_state.parameters = parameters;
    
    target_state.filter_length =
        int(parameters.peak_to_zero * m_qparams.p_multiple + 1);

    if (target_state.filter_length % 2 == 0) {
        ++target_state.filter_length;
    }

    int half_length = target_state.filter_length / 2; // nb length is odd
    int input_spacing = parameters.numerator;
    int initial_phase = half_length % input_spacing;

    target_state.initial_phase = initial_phase;
    target_state.current_phase = initial_phase;

    if (m_dynamism == RatioMostlyFixed) {
        
        if (m_debug_level > 0) {
            cerr << "BQResampler: creating filter of length "
                 << target_state.filter_length << endl;
        }

        vector<double> filter =
            make_filter(target_state.filter_length, parameters.peak_to_zero);

        phase_data_for(target_state.phase_info,
                       target_state.phase_sorted_filter,
                       target_state.filter_length, &filter,
                       target_state.initial_phase,
                       input_spacing,
                       parameters.denominator);
    } else {
        phase_data_for(target_state.phase_info,
                       target_state.phase_sorted_filter,
                       target_state.filter_length, 0,
                       target_state.initial_phase,
                       input_spacing,
                       parameters.denominator);
    }

    int buffer_left = half_length / input_spacing;
    int buffer_right = buffer_left + 1;

    int buffer_length = buffer_left + buffer_right;
    buffer_length = max(buffer_length,
                        int(prev_state.buffer.size() / m_channels));

    target_state.centre = buffer_length / 2;
    target_state.left = target_state.centre - buffer_left;
    target_state.fill = target_state.centre;

    buffer_length *= m_channels;
    target_state.centre *= m_channels;
    target_state.left *= m_channels;
    target_state.fill *= m_channels;
    
    int n_phases = int(target_state.phase_info.size());

    if (m_debug_level > 0) {
        cerr << "BQResampler: " << m_channels << " channel(s) interleaved"
             << ", buffer left " << buffer_left
             << ", right " << buffer_right
             << ", total " << buffer_length << endl;
    
        cerr << "BQResampler: input spacing " << input_spacing
             << ", output spacing " << parameters.denominator
             << ", initial phase " << initial_phase
             << " of " << n_phases << endl;
    }

    if (prev_state.buffer.size() > 0) {
        if (int(prev_state.buffer.size()) == buffer_length) {
            target_state.buffer = prev_state.buffer;
            target_state.fill = prev_state.fill;
        } else {
            target_state.buffer = floatbuf(buffer_length, 0.0);
            for (int i = 0; i < prev_state.fill; ++i) {
                int offset = i - prev_state.centre;
                int new_ix = offset + target_state.centre;
                if (new_ix >= 0 && new_ix < buffer_length) {
                    target_state.buffer[new_ix] = prev_state.buffer[i];
                    target_state.fill = new_ix + 1;
                }
            }
        }

        int phases_then = int(prev_state.phase_info.size());
        double distance_through =
            double(prev_state.current_phase) / double(phases_then);
        target_state.current_phase = round(n_phases * distance_through);
        if (target_state.current_phase >= n_phases) {
            target_state.current_phase = n_phases - 1;
        }
    } else {
        target_state.buffer = floatbuf(buffer_length, 0.0);
    }
}

double
BQResampler::reconstruct_one(state *s) const
{
    const phase_rec &pr = s->phase_info[s->current_phase];
    int phase_length = pr.length;
    double result = 0.0;

    int dot_length = min(phase_length, int(s->buffer.size()) - s->left);

    if (m_dynamism == RatioMostlyFixed) {
        int phase_start = pr.start_index;
        if (m_channels == 1) {
            result = v_multiply_and_sum
                (s->phase_sorted_filter.data() + phase_start,
                 s->buffer.data() + s->left,
                 dot_length);
        } else {
            for (int i = 0; i < dot_length; ++i) {
                result +=
                    s->phase_sorted_filter[phase_start + i] *
                    s->buffer[s->left + i * m_channels + s->current_channel];
            }
        }
    } else {
        double m = double(m_proto_length - 1) / double(s->filter_length - 1);
        for (int i = 0; i < dot_length; ++i) {
            double sample =
                s->buffer[s->left + i * m_channels + s->current_channel];
            int filter_index = i * s->parameters.numerator + s->current_phase;
            double proto_index = m * filter_index;
            int iix = floor(proto_index);
            double remainder = proto_index - iix;
            double filter_value = m_prototype[iix] * (1.0 - remainder);
            filter_value += m_prototype[iix+1] * remainder;
            result += filter_value * sample;
        }
    }

    s->current_channel = (s->current_channel + 1) % m_channels;
    
    if (s->current_channel == 0) {

        if (pr.drop > 0) {
            int drop = pr.drop * m_channels;
            v_move(s->buffer.data(), s->buffer.data() + drop,
                   int(s->buffer.size()) - drop);
            for (int i = 1; i <= drop; ++i) {
                s->buffer[s->buffer.size() - i] = 0.0;
            }
            s->fill -= drop;
        }

        s->current_phase = pr.next_phase;
    }
    
    return result * s->parameters.scale;
}

}