/*
 * Copyright (c) 2005 Boðaç Topaktaþ
 * Copyright (c) 2020 Paul B Mahol
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "libavutil/channel_layout.h"
#include "libavutil/ffmath.h"
#include "libavutil/opt.h"
#include "avfilter.h"
#include "audio.h"

typedef struct BiquadCoeffs {
    double a1, a2;
    double b0, b1, b2;
} BiquadCoeffs;

typedef struct ASuperCutContext {
    const AVClass *class;

    double cutoff;
    double level;
    double qfactor;
    int order;

    int filter_count;
    int bypass;

    BiquadCoeffs coeffs[10];

    AVFrame *w;

    int (*filter_channels)(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs);
} ASuperCutContext;

static const enum AVSampleFormat sample_fmts[] = {
    AV_SAMPLE_FMT_FLTP, AV_SAMPLE_FMT_DBLP, AV_SAMPLE_FMT_NONE
};

static void calc_q_factors(int n, double *q)
{
    for (int i = 0; i < n / 2; i++)
        q[i] = 1. / (-2. * cos(M_PI * (2. * (i + 1) + n - 1.) / (2. * n)));
}

static int get_coeffs(AVFilterContext *ctx)
{
    ASuperCutContext *s = ctx->priv;
    AVFilterLink *inlink = ctx->inputs[0];
    double w0 = s->cutoff / inlink->sample_rate;
    double K = tan(M_PI * w0);
    double q[10];

    s->bypass = w0 >= 0.5;
    if (s->bypass)
        return 0;

    if (!strcmp(ctx->filter->name, "asubcut")) {
        s->filter_count = s->order / 2 + (s->order & 1);

        calc_q_factors(s->order, q);

        if (s->order & 1) {
            BiquadCoeffs *coeffs = &s->coeffs[0];
            double omega = 2. * tan(M_PI * w0);

            coeffs->b0 = 2. / (2. + omega);
            coeffs->b1 = -coeffs->b0;
            coeffs->b2 = 0.;
            coeffs->a1 = -(omega - 2.) / (2. + omega);
            coeffs->a2 = 0.;
        }

        for (int b = (s->order & 1); b < s->filter_count; b++) {
            BiquadCoeffs *coeffs = &s->coeffs[b];
            const int idx = b - (s->order & 1);
            double norm = 1.0 / (1.0 + K / q[idx] + K * K);

            coeffs->b0 = norm;
            coeffs->b1 = -2.0 * coeffs->b0;
            coeffs->b2 = coeffs->b0;
            coeffs->a1 = -2.0 * (K * K - 1.0) * norm;
            coeffs->a2 = -(1.0 - K / q[idx] + K * K) * norm;
        }
    } else if (!strcmp(ctx->filter->name, "asupercut")) {
        s->filter_count = s->order / 2 + (s->order & 1);

        calc_q_factors(s->order, q);

        if (s->order & 1) {
            BiquadCoeffs *coeffs = &s->coeffs[0];
            double omega = 2. * tan(M_PI * w0);

            coeffs->b0 = omega / (2. + omega);
            coeffs->b1 = coeffs->b0;
            coeffs->b2 = 0.;
            coeffs->a1 = -(omega - 2.) / (2. + omega);
            coeffs->a2 = 0.;
        }

        for (int b = (s->order & 1); b < s->filter_count; b++) {
            BiquadCoeffs *coeffs = &s->coeffs[b];
            const int idx = b - (s->order & 1);
            double norm = 1.0 / (1.0 + K / q[idx] + K * K);

            coeffs->b0 = K * K * norm;
            coeffs->b1 = 2.0 * coeffs->b0;
            coeffs->b2 = coeffs->b0;
            coeffs->a1 = -2.0 * (K * K - 1.0) * norm;
            coeffs->a2 = -(1.0 - K / q[idx] + K * K) * norm;
        }
    } else if (!strcmp(ctx->filter->name, "asuperpass")) {
        double alpha, beta, gamma, theta;
        double theta_0 = 2. * M_PI * (s->cutoff / inlink->sample_rate);
        double d_E;

        s->filter_count = s->order / 2;
        d_E = (2. * tan(theta_0 / (2. * s->qfactor))) / sin(theta_0);

        for (int b = 0; b < s->filter_count; b += 2) {
            double D = 2. * sin(((b + 1) * M_PI) / (2. * s->filter_count));
            double A = (1. + pow((d_E / 2.), 2)) / (D * d_E / 2.);
            double d = sqrt((d_E * D) / (A + sqrt(A * A - 1.)));
            double B = D * (d_E / 2.) / d;
            double W = B + sqrt(B * B - 1.);

            for (int j = 0; j < 2; j++) {
                BiquadCoeffs *coeffs = &s->coeffs[b + j];

                if (j == 1)
                    theta = 2. * atan(tan(theta_0 / 2.) / W);
                else
                    theta = 2. * atan(W * tan(theta_0 / 2.));

                beta = 0.5 * ((1. - (d / 2.) * sin(theta)) / (1. + (d / 2.) * sin(theta)));
                gamma = (0.5 + beta) * cos(theta);
                alpha = 0.5 * (0.5 - beta) * sqrt(1. + pow((W - (1. / W)) / d, 2.));

                coeffs->a1 =  2. * gamma;
                coeffs->a2 = -2. * beta;
                coeffs->b0 =  2. * alpha;
                coeffs->b1 =  0.;
                coeffs->b2 = -2. * alpha;
            }
        }
    } else if (!strcmp(ctx->filter->name, "asuperstop")) {
        double alpha, beta, gamma, theta;
        double theta_0 = 2. * M_PI * (s->cutoff / inlink->sample_rate);
        double d_E;

        s->filter_count = s->order / 2;
        d_E = (2. * tan(theta_0 / (2. * s->qfactor))) / sin(theta_0);

        for (int b = 0; b < s->filter_count; b += 2) {
            double D = 2. * sin(((b + 1) * M_PI) / (2. * s->filter_count));
            double A = (1. + pow((d_E / 2.), 2)) / (D * d_E / 2.);
            double d = sqrt((d_E * D) / (A + sqrt(A * A - 1.)));
            double B = D * (d_E / 2.) / d;
            double W = B + sqrt(B * B - 1.);

            for (int j = 0; j < 2; j++) {
                BiquadCoeffs *coeffs = &s->coeffs[b + j];

                if (j == 1)
                    theta = 2. * atan(tan(theta_0 / 2.) / W);
                else
                    theta = 2. * atan(W * tan(theta_0 / 2.));

                beta = 0.5 * ((1. - (d / 2.) * sin(theta)) / (1. + (d / 2.) * sin(theta)));
                gamma = (0.5 + beta) * cos(theta);
                alpha = 0.5 * (0.5 + beta) * ((1. - cos(theta)) / (1. - cos(theta_0)));

                coeffs->a1 =  2. * gamma;
                coeffs->a2 = -2. * beta;
                coeffs->b0 =  2. * alpha;
                coeffs->b1 = -4. * alpha * cos(theta_0);
                coeffs->b2 =  2. * alpha;
            }
        }
    }

    return 0;
}

typedef struct ThreadData {
    AVFrame *in, *out;
} ThreadData;

#define FILTER(name, type)                                          \
static int filter_channels_## name(AVFilterContext *ctx, void *arg, \
                                   int jobnr, int nb_jobs)          \
{                                                                   \
    ASuperCutContext *s = ctx->priv;                                \
    ThreadData *td = arg;                                           \
    AVFrame *out = td->out;                                         \
    AVFrame *in = td->in;                                           \
    const int start = (in->ch_layout.nb_channels * jobnr) / nb_jobs; \
    const int end = (in->ch_layout.nb_channels * (jobnr+1)) / nb_jobs; \
    const double level = s->level;                                  \
                                                                    \
    for (int ch = start; ch < end; ch++) {                          \
        const type *src = (const type *)in->extended_data[ch];      \
        type *dst = (type *)out->extended_data[ch];                 \
                                                                    \
        for (int b = 0; b < s->filter_count; b++) {                 \
            BiquadCoeffs *coeffs = &s->coeffs[b];                   \
            const type a1 = coeffs->a1;                             \
            const type a2 = coeffs->a2;                             \
            const type b0 = coeffs->b0;                             \
            const type b1 = coeffs->b1;                             \
            const type b2 = coeffs->b2;                             \
            type *w = ((type *)s->w->extended_data[ch]) + b * 2;    \
                                                                    \
            for (int n = 0; n < in->nb_samples; n++) {              \
                type sin = b ? dst[n] : src[n] * level;             \
                type sout = sin * b0 + w[0];                        \
                                                                    \
                w[0] = b1 * sin + w[1] + a1 * sout;                 \
                w[1] = b2 * sin + a2 * sout;                        \
                                                                    \
                dst[n] = sout;                                      \
            }                                                       \
        }                                                           \
    }                                                               \
                                                                    \
    return 0;                                                       \
}

FILTER(fltp, float)
FILTER(dblp, double)

static int config_input(AVFilterLink *inlink)
{
    AVFilterContext *ctx = inlink->dst;
    ASuperCutContext *s = ctx->priv;

    switch (inlink->format) {
    case AV_SAMPLE_FMT_FLTP: s->filter_channels = filter_channels_fltp; break;
    case AV_SAMPLE_FMT_DBLP: s->filter_channels = filter_channels_dblp; break;
    }

    s->w = ff_get_audio_buffer(inlink, 2 * 10);
    if (!s->w)
        return AVERROR(ENOMEM);

    return get_coeffs(ctx);
}

static int filter_frame(AVFilterLink *inlink, AVFrame *in)
{
    AVFilterContext *ctx = inlink->dst;
    ASuperCutContext *s = ctx->priv;
    AVFilterLink *outlink = ctx->outputs[0];
    ThreadData td;
    AVFrame *out;

    if (s->bypass)
        return ff_filter_frame(outlink, in);

    if (av_frame_is_writable(in)) {
        out = in;
    } else {
        out = ff_get_audio_buffer(outlink, in->nb_samples);
        if (!out) {
            av_frame_free(&in);
            return AVERROR(ENOMEM);
        }
        av_frame_copy_props(out, in);
    }

    td.in = in; td.out = out;
    ff_filter_execute(ctx, s->filter_channels, &td, NULL,
                      FFMIN(inlink->ch_layout.nb_channels, ff_filter_get_nb_threads(ctx)));

    if (out != in)
        av_frame_free(&in);
    return ff_filter_frame(outlink, out);
}

static int process_command(AVFilterContext *ctx, const char *cmd, const char *args,
                           char *res, int res_len, int flags)
{
    int ret;

    ret = ff_filter_process_command(ctx, cmd, args, res, res_len, flags);
    if (ret < 0)
        return ret;

    return get_coeffs(ctx);
}

static av_cold void uninit(AVFilterContext *ctx)
{
    ASuperCutContext *s = ctx->priv;

    av_frame_free(&s->w);
}

#define OFFSET(x) offsetof(ASuperCutContext, x)
#define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_RUNTIME_PARAM

static const AVOption asupercut_options[] = {
    { "cutoff", "set cutoff frequency", OFFSET(cutoff), AV_OPT_TYPE_DOUBLE, {.dbl=20000}, 20000, 192000, FLAGS },
    { "order",  "set filter order",     OFFSET(order),  AV_OPT_TYPE_INT,    {.i64=10},        3,     20, FLAGS },
    { "level",  "set input level",      OFFSET(level),  AV_OPT_TYPE_DOUBLE, {.dbl=1.},        0.,    1., FLAGS },
    { NULL }
};

AVFILTER_DEFINE_CLASS(asupercut);

static const AVFilterPad inputs[] = {
    {
        .name         = "default",
        .type         = AVMEDIA_TYPE_AUDIO,
        .filter_frame = filter_frame,
        .config_props = config_input,
    },
};

const AVFilter ff_af_asupercut = {
    .name            = "asupercut",
    .description     = NULL_IF_CONFIG_SMALL("Cut super frequencies."),
    .priv_size       = sizeof(ASuperCutContext),
    .priv_class      = &asupercut_class,
    .uninit          = uninit,
    FILTER_INPUTS(inputs),
    FILTER_OUTPUTS(ff_audio_default_filterpad),
    FILTER_SAMPLEFMTS_ARRAY(sample_fmts),
    .process_command = process_command,
    .flags           = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC |
                       AVFILTER_FLAG_SLICE_THREADS,
};

static const AVOption asubcut_options[] = {
    { "cutoff", "set cutoff frequency", OFFSET(cutoff), AV_OPT_TYPE_DOUBLE, {.dbl=20},  2, 200, FLAGS },
    { "order",  "set filter order",     OFFSET(order),  AV_OPT_TYPE_INT,    {.i64=10},  3,  20, FLAGS },
    { "level",  "set input level",      OFFSET(level),  AV_OPT_TYPE_DOUBLE, {.dbl=1.}, 0.,  1., FLAGS },
    { NULL }
};

AVFILTER_DEFINE_CLASS(asubcut);

const AVFilter ff_af_asubcut = {
    .name            = "asubcut",
    .description     = NULL_IF_CONFIG_SMALL("Cut subwoofer frequencies."),
    .priv_size       = sizeof(ASuperCutContext),
    .priv_class      = &asubcut_class,
    .uninit          = uninit,
    FILTER_INPUTS(inputs),
    FILTER_OUTPUTS(ff_audio_default_filterpad),
    FILTER_SAMPLEFMTS_ARRAY(sample_fmts),
    .process_command = process_command,
    .flags           = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC |
                       AVFILTER_FLAG_SLICE_THREADS,
};

static const AVOption asuperpass_asuperstop_options[] = {
    { "centerf","set center frequency", OFFSET(cutoff), AV_OPT_TYPE_DOUBLE, {.dbl=1000}, 2, 999999, FLAGS },
    { "order",  "set filter order",     OFFSET(order),  AV_OPT_TYPE_INT,    {.i64=4},    4,     20, FLAGS },
    { "qfactor","set Q-factor",         OFFSET(qfactor),AV_OPT_TYPE_DOUBLE, {.dbl=1.},0.01,   100., FLAGS },
    { "level",  "set input level",      OFFSET(level),  AV_OPT_TYPE_DOUBLE, {.dbl=1.},   0.,    2., FLAGS },
    { NULL }
};

AVFILTER_DEFINE_CLASS_EXT(asuperpass_asuperstop, "asuperpass/asuperstop",
                          asuperpass_asuperstop_options);

const AVFilter ff_af_asuperpass = {
    .name            = "asuperpass",
    .description     = NULL_IF_CONFIG_SMALL("Apply high order Butterworth band-pass filter."),
    .priv_class      = &asuperpass_asuperstop_class,
    .priv_size       = sizeof(ASuperCutContext),
    .uninit          = uninit,
    FILTER_INPUTS(inputs),
    FILTER_OUTPUTS(ff_audio_default_filterpad),
    FILTER_SAMPLEFMTS_ARRAY(sample_fmts),
    .process_command = process_command,
    .flags           = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC |
                       AVFILTER_FLAG_SLICE_THREADS,
};

const AVFilter ff_af_asuperstop = {
    .name            = "asuperstop",
    .description     = NULL_IF_CONFIG_SMALL("Apply high order Butterworth band-stop filter."),
    .priv_class      = &asuperpass_asuperstop_class,
    .priv_size       = sizeof(ASuperCutContext),
    .uninit          = uninit,
    FILTER_INPUTS(inputs),
    FILTER_OUTPUTS(ff_audio_default_filterpad),
    FILTER_SAMPLEFMTS_ARRAY(sample_fmts),
    .process_command = process_command,
    .flags           = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC |
                       AVFILTER_FLAG_SLICE_THREADS,
};