/*
  * Copyright (c) 2016 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/audio_fifo.h"
 #include "libavutil/avstring.h"
 #include "libavfilter/internal.h"
 #include "libavutil/common.h"
 #include "libavutil/opt.h"
 #include "libavcodec/avfft.h"
 #include "libavutil/eval.h"
 #include "audio.h"
 #include "window_func.h"
 
 typedef struct AFFTFiltContext {
     const AVClass *class;
     char *real_str;
     char *img_str;
     int fft_bits;
 
     FFTContext *fft, *ifft;
     FFTComplex **fft_data;
     int nb_exprs;
     int window_size;
     AVExpr **real;
     AVExpr **imag;
     AVAudioFifo *fifo;
     int64_t pts;
     int hop_size;
     float overlap;
     AVFrame *buffer;
     int start, end;
     int win_func;
     float win_scale;
     float *window_func_lut;
 } AFFTFiltContext;
 
 static const char *const var_names[] = {            "sr",     "b",       "nb",        "ch",        "chs",   "pts",        NULL };
 enum                                   { VAR_SAMPLE_RATE, VAR_BIN, VAR_NBBINS, VAR_CHANNEL, VAR_CHANNELS, VAR_PTS, VAR_VARS_NB };
 
 #define OFFSET(x) offsetof(AFFTFiltContext, x)
 #define A AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
 
 static const AVOption afftfilt_options[] = {
     { "real", "set channels real expressions",       OFFSET(real_str), AV_OPT_TYPE_STRING, {.str = "1" }, 0, 0, A },
     { "imag",  "set channels imaginary expressions", OFFSET(img_str),  AV_OPT_TYPE_STRING, {.str = NULL }, 0, 0, A },
     { "win_size", "set window size", OFFSET(fft_bits), AV_OPT_TYPE_INT, {.i64=12}, 4, 16, A, "fft" },
         { "w16",    0, 0, AV_OPT_TYPE_CONST, {.i64=4},  0, 0, A, "fft" },
         { "w32",    0, 0, AV_OPT_TYPE_CONST, {.i64=5},  0, 0, A, "fft" },
         { "w64",    0, 0, AV_OPT_TYPE_CONST, {.i64=6},  0, 0, A, "fft" },
         { "w128",   0, 0, AV_OPT_TYPE_CONST, {.i64=7},  0, 0, A, "fft" },
         { "w256",   0, 0, AV_OPT_TYPE_CONST, {.i64=8},  0, 0, A, "fft" },
         { "w512",   0, 0, AV_OPT_TYPE_CONST, {.i64=9},  0, 0, A, "fft" },
         { "w1024",  0, 0, AV_OPT_TYPE_CONST, {.i64=10}, 0, 0, A, "fft" },
         { "w2048",  0, 0, AV_OPT_TYPE_CONST, {.i64=11}, 0, 0, A, "fft" },
         { "w4096",  0, 0, AV_OPT_TYPE_CONST, {.i64=12}, 0, 0, A, "fft" },
         { "w8192",  0, 0, AV_OPT_TYPE_CONST, {.i64=13}, 0, 0, A, "fft" },
         { "w16384", 0, 0, AV_OPT_TYPE_CONST, {.i64=14}, 0, 0, A, "fft" },
         { "w32768", 0, 0, AV_OPT_TYPE_CONST, {.i64=15}, 0, 0, A, "fft" },
         { "w65536", 0, 0, AV_OPT_TYPE_CONST, {.i64=16}, 0, 0, A, "fft" },
     { "win_func", "set window function", OFFSET(win_func), AV_OPT_TYPE_INT, {.i64 = WFUNC_HANNING}, 0, NB_WFUNC-1, A, "win_func" },
         { "rect",     "Rectangular",      0, AV_OPT_TYPE_CONST, {.i64=WFUNC_RECT},     0, 0, A, "win_func" },
         { "bartlett", "Bartlett",         0, AV_OPT_TYPE_CONST, {.i64=WFUNC_BARTLETT}, 0, 0, A, "win_func" },
         { "hann",     "Hann",             0, AV_OPT_TYPE_CONST, {.i64=WFUNC_HANNING},  0, 0, A, "win_func" },
         { "hanning",  "Hanning",          0, AV_OPT_TYPE_CONST, {.i64=WFUNC_HANNING},  0, 0, A, "win_func" },
         { "hamming",  "Hamming",          0, AV_OPT_TYPE_CONST, {.i64=WFUNC_HAMMING},  0, 0, A, "win_func" },
         { "sine",     "Sine",             0, AV_OPT_TYPE_CONST, {.i64=WFUNC_SINE},     0, 0, A, "win_func" },
     { "overlap", "set window overlap", OFFSET(overlap), AV_OPT_TYPE_FLOAT, {.dbl=0.75}, 0,  1, A },
     { NULL },
 };
 
 AVFILTER_DEFINE_CLASS(afftfilt);
 
 static int config_input(AVFilterLink *inlink)
 {
     AVFilterContext *ctx = inlink->dst;
     AFFTFiltContext *s = ctx->priv;
     char *saveptr = NULL;
     int ret = 0, ch, i;
     float overlap;

     char *args;
     const char *last_expr = "1";

 
     s->fft  = av_fft_init(s->fft_bits, 0);
     s->ifft = av_fft_init(s->fft_bits, 1);
     if (!s->fft || !s->ifft)
         return AVERROR(ENOMEM);
 
     s->window_size = 1 << s->fft_bits;
 
     s->fft_data = av_calloc(inlink->channels, sizeof(*s->fft_data));
     if (!s->fft_data)
         return AVERROR(ENOMEM);
 
     for (ch = 0; ch < inlink->channels; ch++) {
         s->fft_data[ch] = av_calloc(s->window_size, sizeof(**s->fft_data));
         if (!s->fft_data[ch])
             return AVERROR(ENOMEM);
     }
 
     s->real = av_calloc(inlink->channels, sizeof(*s->real));
     if (!s->real)
         return AVERROR(ENOMEM);
 
     s->imag = av_calloc(inlink->channels, sizeof(*s->imag));
     if (!s->imag)
         return AVERROR(ENOMEM);
 
     args = av_strdup(s->real_str);
     if (!args)
         return AVERROR(ENOMEM);
 
     for (ch = 0; ch < inlink->channels; ch++) {
         char *arg = av_strtok(ch == 0 ? args : NULL, "|", &saveptr);
 
         ret = av_expr_parse(&s->real[ch], arg ? arg : last_expr, var_names,
                             NULL, NULL, NULL, NULL, 0, ctx);
         if (ret < 0)
             break;
         if (arg)
             last_expr = arg;
         s->nb_exprs++;
     }
 
     av_free(args);
 
     args = av_strdup(s->img_str ? s->img_str : s->real_str);
     if (!args)
         return AVERROR(ENOMEM);
 
     for (ch = 0; ch < inlink->channels; ch++) {
         char *arg = av_strtok(ch == 0 ? args : NULL, "|", &saveptr);
 
         ret = av_expr_parse(&s->imag[ch], arg ? arg : last_expr, var_names,
                             NULL, NULL, NULL, NULL, 0, ctx);
         if (ret < 0)
             break;
         if (arg)
             last_expr = arg;
     }
 
     av_free(args);
 
     s->fifo = av_audio_fifo_alloc(inlink->format, inlink->channels, s->window_size);
     if (!s->fifo)
         return AVERROR(ENOMEM);
 
     s->window_func_lut = av_realloc_f(s->window_func_lut, s->window_size,
                                       sizeof(*s->window_func_lut));
     if (!s->window_func_lut)
         return AVERROR(ENOMEM);
     ff_generate_window_func(s->window_func_lut, s->window_size, s->win_func, &overlap);
     if (s->overlap == 1)
         s->overlap = overlap;
 
     for (s->win_scale = 0, i = 0; i < s->window_size; i++) {
         s->win_scale += s->window_func_lut[i] * s->window_func_lut[i];
     }
 
     s->hop_size = s->window_size * (1 - s->overlap);
     if (s->hop_size <= 0)
         return AVERROR(EINVAL);
 
     s->buffer = ff_get_audio_buffer(inlink, s->window_size * 2);
     if (!s->buffer)
         return AVERROR(ENOMEM);
 
     return ret;
 }
 
 static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
 {
     AVFilterContext *ctx = inlink->dst;
     AVFilterLink *outlink = ctx->outputs[0];
     AFFTFiltContext *s = ctx->priv;
     const int window_size = s->window_size;
     const float f = 1. / s->win_scale;
     double values[VAR_VARS_NB];
     AVFrame *out, *in = NULL;
     int ch, n, ret, i, j, k;
     int start = s->start, end = s->end;
 
     av_audio_fifo_write(s->fifo, (void **)frame->extended_data, frame->nb_samples);
     av_frame_free(&frame);
 
     while (av_audio_fifo_size(s->fifo) >= window_size) {
         if (!in) {
             in = ff_get_audio_buffer(outlink, window_size);
             if (!in)
                 return AVERROR(ENOMEM);
         }
 
         ret = av_audio_fifo_peek(s->fifo, (void **)in->extended_data, window_size);
         if (ret < 0)
             break;
 
         for (ch = 0; ch < inlink->channels; ch++) {
             const float *src = (float *)in->extended_data[ch];
             FFTComplex *fft_data = s->fft_data[ch];
 
             for (n = 0; n < in->nb_samples; n++) {
                 fft_data[n].re = src[n] * s->window_func_lut[n];
                 fft_data[n].im = 0;
             }
 
             for (; n < window_size; n++) {
                 fft_data[n].re = 0;
                 fft_data[n].im = 0;
             }
         }
 
         values[VAR_PTS]         = s->pts;
         values[VAR_SAMPLE_RATE] = inlink->sample_rate;
         values[VAR_NBBINS]      = window_size / 2;
         values[VAR_CHANNELS]    = inlink->channels;
 
         for (ch = 0; ch < inlink->channels; ch++) {
             FFTComplex *fft_data = s->fft_data[ch];
             float *buf = (float *)s->buffer->extended_data[ch];
             int x;
 
             values[VAR_CHANNEL] = ch;
 
             av_fft_permute(s->fft, fft_data);
             av_fft_calc(s->fft, fft_data);
 
             for (n = 0; n < window_size / 2; n++) {
                 float fr, fi;
 
                 values[VAR_BIN] = n;
 
                 fr = av_expr_eval(s->real[ch], values, s);
                 fi = av_expr_eval(s->imag[ch], values, s);
 
                 fft_data[n].re *= fr;
                 fft_data[n].im *= fi;
             }
 
             for (n = window_size / 2 + 1, x = window_size / 2 - 1; n < window_size; n++, x--) {
                 fft_data[n].re =  fft_data[x].re;
                 fft_data[n].im = -fft_data[x].im;
             }
 
             av_fft_permute(s->ifft, fft_data);
             av_fft_calc(s->ifft, fft_data);
 
             start = s->start;
             end = s->end;
             k = end;
             for (i = 0, j = start; j < k && i < window_size; i++, j++) {
                 buf[j] += s->fft_data[ch][i].re * f;
             }
 
             for (; i < window_size; i++, j++) {
                 buf[j] = s->fft_data[ch][i].re * f;
             }
 
             start += s->hop_size;
             end = j;
         }
 
         s->start = start;
         s->end = end;
 
         if (start >= window_size) {
             float *dst, *buf;
 
             start -= window_size;
             end   -= window_size;
 
             s->start = start;
             s->end = end;
 
             out = ff_get_audio_buffer(outlink, window_size);
             if (!out) {
                 ret = AVERROR(ENOMEM);
                 break;
             }
 
             out->pts = s->pts;
             s->pts += window_size;
 
             for (ch = 0; ch < inlink->channels; ch++) {
                 dst = (float *)out->extended_data[ch];
                 buf = (float *)s->buffer->extended_data[ch];
 
                 for (n = 0; n < window_size; n++) {
                     dst[n] = buf[n] * (1 - s->overlap);
                 }
                 memmove(buf, buf + window_size, window_size * 4);
             }
 
             ret = ff_filter_frame(outlink, out);
             if (ret < 0)
                 break;
         }
 
         av_audio_fifo_drain(s->fifo, s->hop_size);
     }
 
     av_frame_free(&in);
     return ret;
 }
 
 static int query_formats(AVFilterContext *ctx)
 {
     AVFilterFormats *formats;
     AVFilterChannelLayouts *layouts;
     static const enum AVSampleFormat sample_fmts[] = {
         AV_SAMPLE_FMT_FLTP,
         AV_SAMPLE_FMT_NONE
     };
     int ret;
 
     layouts = ff_all_channel_counts();
     if (!layouts)
         return AVERROR(ENOMEM);
     ret = ff_set_common_channel_layouts(ctx, layouts);
     if (ret < 0)
         return ret;
 
     formats = ff_make_format_list(sample_fmts);
     if (!formats)
         return AVERROR(ENOMEM);
     ret = ff_set_common_formats(ctx, formats);
     if (ret < 0)
         return ret;
 
     formats = ff_all_samplerates();
     if (!formats)
         return AVERROR(ENOMEM);
     return ff_set_common_samplerates(ctx, formats);
 }
 
 static av_cold void uninit(AVFilterContext *ctx)
 {
     AFFTFiltContext *s = ctx->priv;
     int i;
 
     av_fft_end(s->fft);
     av_fft_end(s->ifft);
 
     for (i = 0; i < s->nb_exprs; i++) {
         if (s->fft_data)
             av_freep(&s->fft_data[i]);
     }
     av_freep(&s->fft_data);
 
     for (i = 0; i < s->nb_exprs; i++) {
         av_expr_free(s->real[i]);
         av_expr_free(s->imag[i]);
     }
 
     av_freep(&s->real);
     av_freep(&s->imag);
     av_frame_free(&s->buffer);
 }
 
 static const AVFilterPad inputs[] = {
     {
         .name         = "default",
         .type         = AVMEDIA_TYPE_AUDIO,
         .config_props = config_input,
         .filter_frame = filter_frame,
     },
     { NULL }
 };
 
 static const AVFilterPad outputs[] = {
     {
         .name = "default",
         .type = AVMEDIA_TYPE_AUDIO,
     },
     { NULL }
 };
 
 AVFilter ff_af_afftfilt = {
     .name            = "afftfilt",
     .description     = NULL_IF_CONFIG_SMALL("Apply arbitrary expressions to samples in frequency domain."),
     .priv_size       = sizeof(AFFTFiltContext),
     .priv_class      = &afftfilt_class,
     .inputs          = inputs,
     .outputs         = outputs,
     .query_formats   = query_formats,
     .uninit          = uninit,
 };