/*
  * Copyright (c) 2015 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/lfg.h"
 #include "libavutil/opt.h"
 #include "libavutil/random_seed.h"
 #include "avfilter.h"
 #include "formats.h"
 #include "internal.h"
 #include "video.h"
 
 #define MAX_FRAMES 512
 
 typedef struct RandomContext {
     const AVClass *class;
 
     AVLFG lfg;
     int nb_frames;
     int64_t random_seed;
     int nb_frames_filled;
     AVFrame *frames[MAX_FRAMES];
     int64_t pts[MAX_FRAMES];
     int flush_idx;
 } RandomContext;
 
 #define OFFSET(x) offsetof(RandomContext, x)
 #define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
 
 static const AVOption random_options[] = {
     { "frames", "set number of frames in cache", OFFSET(nb_frames),   AV_OPT_TYPE_INT,   {.i64=30},  2, MAX_FRAMES, FLAGS },
     { "seed",   "set the seed",                  OFFSET(random_seed), AV_OPT_TYPE_INT64, {.i64=-1}, -1, UINT32_MAX, FLAGS },
     { NULL }
 };
 
 AVFILTER_DEFINE_CLASS(random);
 
 static av_cold int init(AVFilterContext *ctx)
 {
     RandomContext *s = ctx->priv;
     uint32_t seed;
 
     if (s->random_seed < 0)
         s->random_seed = av_get_random_seed();
     seed = s->random_seed;
     av_lfg_init(&s->lfg, seed);
 
     return 0;
 }
 
 static int filter_frame(AVFilterLink *inlink, AVFrame *in)
 {
     AVFilterContext *ctx = inlink->dst;
     RandomContext *s = ctx->priv;
     AVFilterLink *outlink = ctx->outputs[0];
     AVFrame *out;
     int idx;
 
     if (s->nb_frames_filled < s->nb_frames) {
         s->frames[s->nb_frames_filled] = in;
         s->pts[s->nb_frames_filled++] = in->pts;
         return 0;
     }
 
     idx = av_lfg_get(&s->lfg) % s->nb_frames;
 
     out = s->frames[idx];
     out->pts = s->pts[0];
     memmove(&s->pts[0], &s->pts[1], (s->nb_frames - 1) * sizeof(s->pts[0]));
     s->frames[idx] = in;
     s->pts[s->nb_frames - 1] = in->pts;
 
     return ff_filter_frame(outlink, out);
 }
 
 static int request_frame(AVFilterLink *outlink)
 {
     AVFilterContext *ctx = outlink->src;
     RandomContext *s = ctx->priv;
     int ret;
 
     ret = ff_request_frame(ctx->inputs[0]);
 
     if (ret == AVERROR_EOF && !ctx->is_disabled && s->nb_frames > 0) {
         AVFrame *out = s->frames[s->nb_frames - 1];
         out->pts = s->pts[s->flush_idx++];
         ret = ff_filter_frame(outlink, out);
         s->frames[s->nb_frames - 1] = NULL;
         s->nb_frames--;
     }
 
     return ret;
 }
 
 static const AVFilterPad random_inputs[] = {
     {
         .name         = "default",
         .type         = AVMEDIA_TYPE_VIDEO,
         .filter_frame = filter_frame,
     },
     { NULL }
 };
 
 static const AVFilterPad random_outputs[] = {
     {
         .name          = "default",
         .type          = AVMEDIA_TYPE_VIDEO,
         .request_frame = request_frame,
     },
     { NULL }
 };
 
 AVFilter ff_vf_random = {
     .name        = "random",
     .description = NULL_IF_CONFIG_SMALL("Return random frames."),
     .priv_size   = sizeof(RandomContext),
     .priv_class  = &random_class,
     .init        = init,
     .inputs      = random_inputs,
     .outputs     = random_outputs,
 };