/*
  * Copyright (c) 2011 Stefano Sabatini
  *
  * 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
  */
 
 /**
  * @file
  * filter for selecting which frame passes in the filterchain
  */
 
 #include "libavutil/eval.h"
 #include "libavutil/fifo.h"
 #include "avfilter.h"
 

 static const char * const var_names[] = {

     "TB",                ///< timebase
 
     "pts",               ///< original pts in the file of the frame
     "start_pts",         ///< first PTS in the stream, expressed in TB units
     "prev_pts",          ///< previous frame PTS
     "prev_selected_pts", ///< previous selected frame PTS
 
     "t",                 ///< first PTS in seconds
     "start_t",           ///< first PTS in the stream, expressed in seconds
     "prev_t",            ///< previous frame time
     "prev_selected_t",   ///< previously selected time
 
     "pict_type",         ///< the type of picture in the movie

     "I",
     "P",
     "B",
     "S",
     "SI",
     "SP",
     "BI",

 
     "interlace_type",    ///< the frame interlace type

     "PROGRESSIVE",
     "TOPFIRST",
     "BOTTOMFIRST",

 
     "n",                 ///< frame number (starting from zero)
     "selected_n",        ///< selected frame number (starting from zero)
     "prev_selected_n",   ///< number of the last selected frame
 
     "key",               ///< tell if the frame is a key frame
     "pos",               ///< original position in the file of the frame
 
     NULL
 };
 
 enum var_name {
     VAR_TB,
 
     VAR_PTS,
     VAR_START_PTS,
     VAR_PREV_PTS,
     VAR_PREV_SELECTED_PTS,
 
     VAR_T,
     VAR_START_T,
     VAR_PREV_T,
     VAR_PREV_SELECTED_T,
 
     VAR_PICT_TYPE,
     VAR_PICT_TYPE_I,
     VAR_PICT_TYPE_P,
     VAR_PICT_TYPE_B,
     VAR_PICT_TYPE_S,
     VAR_PICT_TYPE_SI,
     VAR_PICT_TYPE_SP,
     VAR_PICT_TYPE_BI,
 
     VAR_INTERLACE_TYPE,
     VAR_INTERLACE_TYPE_P,
     VAR_INTERLACE_TYPE_T,
     VAR_INTERLACE_TYPE_B,
 
     VAR_N,
     VAR_SELECTED_N,
     VAR_PREV_SELECTED_N,
 
     VAR_KEY,
     VAR_POS,
 
     VAR_VARS_NB
 };
 
 #define FIFO_SIZE 8
 
 typedef struct {
     AVExpr *expr;
     double var_values[VAR_VARS_NB];
     double select;
     int cache_frames;
     AVFifoBuffer *pending_frames; ///< FIFO buffer of video frames
 } SelectContext;
 
 static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
 {
     SelectContext *select = ctx->priv;
     int ret;
 
     if ((ret = av_expr_parse(&select->expr, args ? args : "1",
                              var_names, NULL, NULL, NULL, NULL, 0, ctx)) < 0) {
         av_log(ctx, AV_LOG_ERROR, "Error while parsing expression '%s'\n", args);
         return ret;
     }
 
     select->pending_frames = av_fifo_alloc(FIFO_SIZE*sizeof(AVFilterBufferRef*));
     if (!select->pending_frames) {
         av_log(ctx, AV_LOG_ERROR, "Failed to allocate pending frames buffer.\n");
         return AVERROR(ENOMEM);
     }
     return 0;
 }
 
 #define INTERLACE_TYPE_P 0
 #define INTERLACE_TYPE_T 1
 #define INTERLACE_TYPE_B 2
 
 static int config_input(AVFilterLink *inlink)
 {
     SelectContext *select = inlink->dst->priv;
 
     select->var_values[VAR_N]          = 0.0;
     select->var_values[VAR_SELECTED_N] = 0.0;
 
     select->var_values[VAR_TB] = av_q2d(inlink->time_base);
 
     select->var_values[VAR_PREV_PTS]          = NAN;
     select->var_values[VAR_PREV_SELECTED_PTS] = NAN;
     select->var_values[VAR_PREV_SELECTED_T]   = NAN;
     select->var_values[VAR_START_PTS]         = NAN;
     select->var_values[VAR_START_T]           = NAN;
 
     select->var_values[VAR_PICT_TYPE_I]  = AV_PICTURE_TYPE_I;
     select->var_values[VAR_PICT_TYPE_P]  = AV_PICTURE_TYPE_P;
     select->var_values[VAR_PICT_TYPE_B]  = AV_PICTURE_TYPE_B;
     select->var_values[VAR_PICT_TYPE_SI] = AV_PICTURE_TYPE_SI;
     select->var_values[VAR_PICT_TYPE_SP] = AV_PICTURE_TYPE_SP;
 
     select->var_values[VAR_INTERLACE_TYPE_P] = INTERLACE_TYPE_P;
     select->var_values[VAR_INTERLACE_TYPE_T] = INTERLACE_TYPE_T;

     select->var_values[VAR_INTERLACE_TYPE_B] = INTERLACE_TYPE_B;

 
     return 0;
 }
 
 #define D2TS(d)  (isnan(d) ? AV_NOPTS_VALUE : (int64_t)(d))
 #define TS2D(ts) ((ts) == AV_NOPTS_VALUE ? NAN : (double)(ts))
 
 static int select_frame(AVFilterContext *ctx, AVFilterBufferRef *picref)
 {
     SelectContext *select = ctx->priv;
     AVFilterLink *inlink = ctx->inputs[0];
     double res;
 
     if (isnan(select->var_values[VAR_START_PTS]))
         select->var_values[VAR_START_PTS] = TS2D(picref->pts);

     if (isnan(select->var_values[VAR_START_T]))
         select->var_values[VAR_START_T] = TS2D(picref->pts) * av_q2d(inlink->time_base);

 
     select->var_values[VAR_PTS] = TS2D(picref->pts);

     select->var_values[VAR_T  ] = TS2D(picref->pts) * av_q2d(inlink->time_base);

     select->var_values[VAR_POS] = picref->pos == -1 ? NAN : picref->pos;
     select->var_values[VAR_PREV_PTS] = TS2D(picref ->pts);
 
     select->var_values[VAR_INTERLACE_TYPE] =
         !picref->video->interlaced     ? INTERLACE_TYPE_P :
         picref->video->top_field_first ? INTERLACE_TYPE_T : INTERLACE_TYPE_B;
     select->var_values[VAR_PICT_TYPE] = picref->video->pict_type;
 
     res = av_expr_eval(select->expr, select->var_values, NULL);
     av_log(inlink->dst, AV_LOG_DEBUG,
            "n:%d pts:%d t:%f pos:%d interlace_type:%c key:%d pict_type:%c "
            "-> select:%f\n",
            (int)select->var_values[VAR_N],
            (int)select->var_values[VAR_PTS],
            select->var_values[VAR_T],
            (int)select->var_values[VAR_POS],
            select->var_values[VAR_INTERLACE_TYPE] == INTERLACE_TYPE_P ? 'P' :
            select->var_values[VAR_INTERLACE_TYPE] == INTERLACE_TYPE_T ? 'T' :
            select->var_values[VAR_INTERLACE_TYPE] == INTERLACE_TYPE_B ? 'B' : '?',
            (int)select->var_values[VAR_KEY],
            av_get_picture_type_char(select->var_values[VAR_PICT_TYPE]),
            res);
 
     select->var_values[VAR_N] += 1.0;
 
     if (res) {
         select->var_values[VAR_PREV_SELECTED_N]   = select->var_values[VAR_N];
         select->var_values[VAR_PREV_SELECTED_PTS] = select->var_values[VAR_PTS];
         select->var_values[VAR_PREV_SELECTED_T]   = select->var_values[VAR_T];
         select->var_values[VAR_SELECTED_N] += 1.0;
     }
     return res;
 }
 
 static void start_frame(AVFilterLink *inlink, AVFilterBufferRef *picref)
 {
     SelectContext *select = inlink->dst->priv;
 
     select->select = select_frame(inlink->dst, picref);
     if (select->select) {
         /* frame was requested through poll_frame */
         if (select->cache_frames) {
             if (!av_fifo_space(select->pending_frames))
                 av_log(inlink->dst, AV_LOG_ERROR,
                        "Buffering limit reached, cannot cache more frames\n");
             else
                 av_fifo_generic_write(select->pending_frames, &picref,
                                       sizeof(picref), NULL);
             return;
         }
         avfilter_start_frame(inlink->dst->outputs[0], avfilter_ref_buffer(picref, ~0));
     }
 }
 
 static void draw_slice(AVFilterLink *inlink, int y, int h, int slice_dir)
 {
     SelectContext *select = inlink->dst->priv;
 
     if (select->select && !select->cache_frames)
         avfilter_draw_slice(inlink->dst->outputs[0], y, h, slice_dir);
 }
 
 static void end_frame(AVFilterLink *inlink)
 {
     SelectContext *select = inlink->dst->priv;
     AVFilterBufferRef *picref = inlink->cur_buf;
 
     if (select->select) {
         if (select->cache_frames)
             return;
         avfilter_end_frame(inlink->dst->outputs[0]);
     }
     avfilter_unref_buffer(picref);
 }
 
 static int request_frame(AVFilterLink *outlink)
 {
     AVFilterContext *ctx = outlink->src;
     SelectContext *select = ctx->priv;
     AVFilterLink *inlink = outlink->src->inputs[0];
     select->select = 0;
 
     if (av_fifo_size(select->pending_frames)) {
         AVFilterBufferRef *picref;
         av_fifo_generic_read(select->pending_frames, &picref, sizeof(picref), NULL);
         avfilter_start_frame(outlink, avfilter_ref_buffer(picref, ~0));
         avfilter_draw_slice(outlink, 0, outlink->h, 1);
         avfilter_end_frame(outlink);
         avfilter_unref_buffer(picref);
         return 0;
     }
 
     while (!select->select) {
         int ret = avfilter_request_frame(inlink);
         if (ret < 0)
             return ret;
     }
 
     return 0;
 }
 
 static int poll_frame(AVFilterLink *outlink)
 {
     SelectContext *select = outlink->src->priv;
     AVFilterLink *inlink = outlink->src->inputs[0];
     int count, ret;
 
     if (!av_fifo_size(select->pending_frames)) {
         if ((count = avfilter_poll_frame(inlink)) <= 0)
             return count;
         /* request frame from input, and apply select condition to it */
         select->cache_frames = 1;
         while (count-- && av_fifo_space(select->pending_frames)) {
             ret = avfilter_request_frame(inlink);
             if (ret < 0)
                 break;
         }
         select->cache_frames = 0;
     }
 
     return av_fifo_size(select->pending_frames)/sizeof(AVFilterBufferRef *);
 }
 
 static av_cold void uninit(AVFilterContext *ctx)
 {
     SelectContext *select = ctx->priv;
     AVFilterBufferRef *picref;
 

     av_expr_free(select->expr);

     select->expr = NULL;
 

     while (select->pending_frames &&
            av_fifo_generic_read(select->pending_frames, &picref, sizeof(picref), NULL) == sizeof(picref))
         avfilter_unref_buffer(picref);
     av_fifo_free(select->pending_frames);

     select->pending_frames = NULL;

 }
 
 AVFilter avfilter_vf_select = {
     .name      = "select",
     .description = NULL_IF_CONFIG_SMALL("Select frames to pass in output."),
     .init      = init,
     .uninit    = uninit,
 
     .priv_size = sizeof(SelectContext),
 

     .inputs    = (const AVFilterPad[]) {{ .name       = "default",

                                     .type             = AVMEDIA_TYPE_VIDEO,
                                     .get_video_buffer = avfilter_null_get_video_buffer,
                                     .config_props     = config_input,
                                     .start_frame      = start_frame,
                                     .draw_slice       = draw_slice,
                                     .end_frame        = end_frame },
                                   { .name = NULL }},

     .outputs   = (const AVFilterPad[]) {{ .name       = "default",

                                     .type             = AVMEDIA_TYPE_VIDEO,
                                     .poll_frame       = poll_frame,
                                     .request_frame    = request_frame, },
                                   { .name = NULL}},
 };