/*
  * webp muxer
  * Copyright (c) 2014 Michael Niedermayer
  *
  * 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/intreadwrite.h"
 #include "libavutil/opt.h"
 #include "avformat.h"
 #include "internal.h"
 
 typedef struct WebpContext{
     AVClass *class;
     int frame_count;
     AVPacket last_pkt;
     int loop;

     int wrote_webp_header;
     int using_webp_anim_encoder;

 } WebpContext;
 
 static int webp_write_header(AVFormatContext *s)
 {
     AVStream *st;
 
     if (s->nb_streams != 1) {
         av_log(s, AV_LOG_ERROR, "Only exactly 1 stream is supported\n");
         return AVERROR(EINVAL);
     }
     st = s->streams[0];

     if (st->codecpar->codec_id != AV_CODEC_ID_WEBP) {

         av_log(s, AV_LOG_ERROR, "Only WebP is supported\n");
         return AVERROR(EINVAL);
     }
     avpriv_set_pts_info(st, 24, 1, 1000);
 

     return 0;
 }
 
 static int is_animated_webp_packet(AVPacket *pkt)
 {
     if (pkt->size) {
         int skip = 0;
         unsigned flags = 0;
 
         if (pkt->size < 4)
             return 0;
         if (AV_RL32(pkt->data) == AV_RL32("RIFF"))
             skip = 12;
 
         if (pkt->size < skip + 4)
             return 0;
         if (AV_RL32(pkt->data + skip) == AV_RL32("VP8X")) {
             flags |= pkt->data[skip + 4 + 4];
         }

         if (flags & 2)  // ANIMATION_FLAG is on
             return 1;
     }

     return 0;
 }
 
 static int flush(AVFormatContext *s, int trailer, int64_t pts)
 {
     WebpContext *w = s->priv_data;
     AVStream *st = s->streams[0];
 
     if (w->last_pkt.size) {
         int skip = 0;

         unsigned flags = 0;
         int vp8x = 0;

         if (w->last_pkt.size < 4)
             return 0;

         if (AV_RL32(w->last_pkt.data) == AV_RL32("RIFF"))
             skip = 12;

 
         if (w->last_pkt.size < skip + 4)
             return 0;  // Safe to do this as a valid WebP bitstream is >=30 bytes.

         if (AV_RL32(w->last_pkt.data + skip) == AV_RL32("VP8X")) {
             flags |= w->last_pkt.data[skip + 4 + 4];
             vp8x = 1;

             skip += AV_RL32(w->last_pkt.data + skip + 4) + 8;

         }

         if (!w->wrote_webp_header) {
             avio_write(s->pb, "RIFF\0\0\0\0WEBP", 12);
             w->wrote_webp_header = 1;
             if (w->frame_count > 1)  // first non-empty packet
                 w->frame_count = 1;  // so we don't count previous empty packets.
         }

         if (w->frame_count == 1) {
             if (!trailer) {
                 vp8x = 1;
                 flags |= 2 + 16;
             }
 
             if (vp8x) {
                 avio_write(s->pb, "VP8X", 4);
                 avio_wl32(s->pb, 10);
                 avio_w8(s->pb, flags);
                 avio_wl24(s->pb, 0);

                 avio_wl24(s->pb, st->codecpar->width - 1);
                 avio_wl24(s->pb, st->codecpar->height - 1);

             }
             if (!trailer) {
                 avio_write(s->pb, "ANIM", 4);
                 avio_wl32(s->pb, 6);
                 avio_wl32(s->pb, 0xFFFFFFFF);
                 avio_wl16(s->pb, w->loop);
             }

         }
 
         if (w->frame_count > trailer) {
             avio_write(s->pb, "ANMF", 4);
             avio_wl32(s->pb, 16 + w->last_pkt.size - skip);
             avio_wl24(s->pb, 0);
             avio_wl24(s->pb, 0);

             avio_wl24(s->pb, st->codecpar->width - 1);
             avio_wl24(s->pb, st->codecpar->height - 1);

             if (w->last_pkt.pts != AV_NOPTS_VALUE && pts != AV_NOPTS_VALUE) {
                 avio_wl24(s->pb, pts - w->last_pkt.pts);
             } else
                 avio_wl24(s->pb, w->last_pkt.duration);
             avio_w8(s->pb, 0);
         }
         avio_write(s->pb, w->last_pkt.data + skip, w->last_pkt.size - skip);

         av_packet_unref(&w->last_pkt);

     }
 
     return 0;
 }
 
 static int webp_write_packet(AVFormatContext *s, AVPacket *pkt)
 {
     WebpContext *w = s->priv_data;

     w->using_webp_anim_encoder |= is_animated_webp_packet(pkt);
 
     if (w->using_webp_anim_encoder) {
         avio_write(s->pb, pkt->data, pkt->size);
         w->wrote_webp_header = 1;  // for good measure
     } else {
         int ret;
         if ((ret = flush(s, 0, pkt->pts)) < 0)
             return ret;

         av_packet_ref(&w->last_pkt, pkt);

     }
     ++w->frame_count;

 
     return 0;
 }
 
 static int webp_write_trailer(AVFormatContext *s)
 {
     unsigned filesize;

     WebpContext *w = s->priv_data;

     if (w->using_webp_anim_encoder) {
         if ((w->frame_count > 1) && w->loop) {  // Write loop count.
             avio_seek(s->pb, 42, SEEK_SET);
             avio_wl16(s->pb, w->loop);
         }
     } else {
         int ret;
         if ((ret = flush(s, 1, AV_NOPTS_VALUE)) < 0)
             return ret;
 
         filesize = avio_tell(s->pb);
         avio_seek(s->pb, 4, SEEK_SET);
         avio_wl32(s->pb, filesize - 8);
         // Note: without the following, avio only writes 8 bytes to the file.
         avio_seek(s->pb, filesize, SEEK_SET);
     }

 
     return 0;
 }
 
 #define OFFSET(x) offsetof(WebpContext, x)
 #define ENC AV_OPT_FLAG_ENCODING_PARAM
 static const AVOption options[] = {
     { "loop", "Number of times to loop the output: 0 - infinite loop", OFFSET(loop),
       AV_OPT_TYPE_INT, { .i64 = 1 }, 0, 65535, ENC },
     { NULL },
 };
 
 static const AVClass webp_muxer_class = {
     .class_name = "WebP muxer",
     .item_name  = av_default_item_name,
     .version    = LIBAVUTIL_VERSION_INT,
     .option     = options,
 };
 AVOutputFormat ff_webp_muxer = {
     .name           = "webp",
     .long_name      = NULL_IF_CONFIG_SMALL("WebP"),
     .extensions     = "webp",
     .priv_data_size = sizeof(WebpContext),
     .video_codec    = AV_CODEC_ID_WEBP,
     .write_header   = webp_write_header,
     .write_packet   = webp_write_packet,
     .write_trailer  = webp_write_trailer,
     .priv_class     = &webp_muxer_class,
     .flags          = AVFMT_VARIABLE_FPS,
 };