/*
  * APNG muxer
  * Copyright (c) 2015 Donny Yang
  *
  * first version by Donny Yang <work@kota.moe>
  *
  * 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 "avformat.h"
 #include "internal.h"
 #include "libavutil/avassert.h"
 #include "libavutil/crc.h"
 #include "libavutil/intreadwrite.h"
 #include "libavutil/log.h"
 #include "libavutil/opt.h"
 #include "libavcodec/png.h"
 #include "libavcodec/apng.h"
 
 typedef struct APNGMuxContext {
     AVClass *class;
 
     uint32_t plays;
     AVRational last_delay;
 
     uint64_t acTL_offset;
     uint32_t frame_number;
 
     AVPacket *prev_packet;
     AVRational prev_delay;
 
     int framerate_warned;

 
     uint8_t *extra_data;
     int extra_data_size;

 } APNGMuxContext;
 
 static uint8_t *apng_find_chunk(uint32_t tag, uint8_t *buf, size_t length)
 {
     size_t b;
     for (b = 0; b < length; b += AV_RB32(buf + b) + 12)
         if (AV_RB32(&buf[b + 4]) == tag)
             return &buf[b];
     return NULL;
 }
 
 static void apng_write_chunk(AVIOContext *io_context, uint32_t tag,
                              uint8_t *buf, size_t length)
 {
     const AVCRC *crc_table = av_crc_get_table(AV_CRC_32_IEEE_LE);
     uint32_t crc = ~0U;
     uint8_t tagbuf[4];
 
     av_assert0(crc_table);
 
     avio_wb32(io_context, length);
     AV_WB32(tagbuf, tag);
     crc = av_crc(crc_table, crc, tagbuf, 4);
     avio_wb32(io_context, tag);
     if (length > 0) {
         crc = av_crc(crc_table, crc, buf, length);
         avio_write(io_context, buf, length);
     }
     avio_wb32(io_context, ~crc);
 }
 
 static int apng_write_header(AVFormatContext *format_context)
 {
     APNGMuxContext *apng = format_context->priv_data;

     AVCodecParameters *par = format_context->streams[0]->codecpar;

 
     if (format_context->nb_streams != 1 ||

         format_context->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO ||
         format_context->streams[0]->codecpar->codec_id   != AV_CODEC_ID_APNG) {

         av_log(format_context, AV_LOG_ERROR,
                "APNG muxer supports only a single video APNG stream.\n");
         return AVERROR(EINVAL);
     }
 
     if (apng->last_delay.num > USHRT_MAX || apng->last_delay.den > USHRT_MAX) {
         av_reduce(&apng->last_delay.num, &apng->last_delay.den,
                   apng->last_delay.num, apng->last_delay.den, USHRT_MAX);
         av_log(format_context, AV_LOG_WARNING,
                "Last frame delay is too precise. Reducing to %d/%d (%f).\n",
                apng->last_delay.num, apng->last_delay.den, (double)apng->last_delay.num / apng->last_delay.den);
     }
 
     avio_wb64(format_context->pb, PNGSIG);
     // Remaining headers are written when they are copied from the encoder
 

     if (par->extradata_size) {
         apng->extra_data = av_mallocz(par->extradata_size + AV_INPUT_BUFFER_PADDING_SIZE);
         if (!apng->extra_data)
             return AVERROR(ENOMEM);
         apng->extra_data_size = par->extradata_size;
         memcpy(apng->extra_data, par->extradata, par->extradata_size);
     }
 

     return 0;
 }
 

 static int flush_packet(AVFormatContext *format_context, AVPacket *packet)

 {
     APNGMuxContext *apng = format_context->priv_data;
     AVIOContext *io_context = format_context->pb;
     AVStream *codec_stream = format_context->streams[0];

     uint8_t *side_data = NULL;
     int side_data_size = 0;

 
     av_assert0(apng->prev_packet);
 

     side_data = av_packet_get_side_data(apng->prev_packet, AV_PKT_DATA_NEW_EXTRADATA, &side_data_size);
 
     if (side_data_size) {
         av_freep(&apng->extra_data);
         apng->extra_data = av_mallocz(side_data_size + AV_INPUT_BUFFER_PADDING_SIZE);
         if (!apng->extra_data)
             return AVERROR(ENOMEM);
         apng->extra_data_size = side_data_size;
         memcpy(apng->extra_data, side_data, apng->extra_data_size);
     }
 

     if (apng->frame_number == 0 && !packet) {
         uint8_t *existing_acTL_chunk;
         uint8_t *existing_fcTL_chunk;
 

         av_log(format_context, AV_LOG_INFO, "Only a single frame so saving as a normal PNG.\n");

 
         // Write normal PNG headers without acTL chunk

         existing_acTL_chunk = apng_find_chunk(MKBETAG('a', 'c', 'T', 'L'), apng->extra_data, apng->extra_data_size);

         if (existing_acTL_chunk) {
             uint8_t *chunk_after_acTL = existing_acTL_chunk + AV_RB32(existing_acTL_chunk) + 12;

             avio_write(io_context, apng->extra_data, existing_acTL_chunk - apng->extra_data);
             avio_write(io_context, chunk_after_acTL, apng->extra_data + apng->extra_data_size - chunk_after_acTL);

         } else {

             avio_write(io_context, apng->extra_data, apng->extra_data_size);

         }
 
         // Write frame data without fcTL chunk
         existing_fcTL_chunk = apng_find_chunk(MKBETAG('f', 'c', 'T', 'L'), apng->prev_packet->data, apng->prev_packet->size);
         if (existing_fcTL_chunk) {
             uint8_t *chunk_after_fcTL = existing_fcTL_chunk + AV_RB32(existing_fcTL_chunk) + 12;
             avio_write(io_context, apng->prev_packet->data, existing_fcTL_chunk - apng->prev_packet->data);
             avio_write(io_context, chunk_after_fcTL, apng->prev_packet->data + apng->prev_packet->size - chunk_after_fcTL);
         } else {
             avio_write(io_context, apng->prev_packet->data, apng->prev_packet->size);
         }
     } else {
         uint8_t *existing_fcTL_chunk;
 
         if (apng->frame_number == 0) {
             uint8_t *existing_acTL_chunk;
 
             // Write normal PNG headers

             avio_write(io_context, apng->extra_data, apng->extra_data_size);

             existing_acTL_chunk = apng_find_chunk(MKBETAG('a', 'c', 'T', 'L'), apng->extra_data, apng->extra_data_size);

             if (!existing_acTL_chunk) {
                 uint8_t buf[8];
                 // Write animation control header
                 apng->acTL_offset = avio_tell(io_context);
                 AV_WB32(buf, UINT_MAX); // number of frames (filled in later)
                 AV_WB32(buf + 4, apng->plays);
                 apng_write_chunk(io_context, MKBETAG('a', 'c', 'T', 'L'), buf, 8);
             }
         }
 
         existing_fcTL_chunk = apng_find_chunk(MKBETAG('f', 'c', 'T', 'L'), apng->prev_packet->data, apng->prev_packet->size);
         if (existing_fcTL_chunk) {
             AVRational delay;
 
             existing_fcTL_chunk += 8;
             delay.num = AV_RB16(existing_fcTL_chunk + 20);
             delay.den = AV_RB16(existing_fcTL_chunk + 22);
 
             if (delay.num == 0 && delay.den == 0) {
                 if (packet) {
                     int64_t delay_num_raw = (packet->dts - apng->prev_packet->dts) * codec_stream->time_base.num;
                     int64_t delay_den_raw = codec_stream->time_base.den;
                     if (!av_reduce(&delay.num, &delay.den, delay_num_raw, delay_den_raw, USHRT_MAX) &&
                         !apng->framerate_warned) {
                         av_log(format_context, AV_LOG_WARNING,
                                "Frame rate is too high or specified too precisely. Unable to copy losslessly.\n");
                         apng->framerate_warned = 1;
                     }

                 } else if (apng->last_delay.num > 0) {

                     delay = apng->last_delay;
                 } else {
                     delay = apng->prev_delay;
                 }
 
                 // Update frame control header with new delay
                 AV_WB16(existing_fcTL_chunk + 20, delay.num);
                 AV_WB16(existing_fcTL_chunk + 22, delay.den);
                 AV_WB32(existing_fcTL_chunk + 26, ~av_crc(av_crc_get_table(AV_CRC_32_IEEE_LE), ~0U, existing_fcTL_chunk - 4, 26 + 4));
             }
             apng->prev_delay = delay;
         }
 
         // Write frame data
         avio_write(io_context, apng->prev_packet->data, apng->prev_packet->size);
     }
     ++apng->frame_number;
 

     av_packet_unref(apng->prev_packet);

     if (packet)

         av_packet_ref(apng->prev_packet, packet);

     return 0;

 }
 
 static int apng_write_packet(AVFormatContext *format_context, AVPacket *packet)
 {
     APNGMuxContext *apng = format_context->priv_data;

     int ret;

 
     if (!apng->prev_packet) {

         apng->prev_packet = av_packet_alloc();

         if (!apng->prev_packet)
             return AVERROR(ENOMEM);
 

         av_packet_ref(apng->prev_packet, packet);

     } else {

         ret = flush_packet(format_context, packet);
         if (ret < 0)
             return ret;

     }
 
     return 0;
 }
 
 static int apng_write_trailer(AVFormatContext *format_context)
 {
     APNGMuxContext *apng = format_context->priv_data;
     AVIOContext *io_context = format_context->pb;
     uint8_t buf[8];

     int ret;

 
     if (apng->prev_packet) {

         ret = flush_packet(format_context, NULL);

         av_freep(&apng->prev_packet);

         if (ret < 0)
             return ret;

     }
 
     apng_write_chunk(io_context, MKBETAG('I', 'E', 'N', 'D'), NULL, 0);
 

     if (apng->acTL_offset && (io_context->seekable & AVIO_SEEKABLE_NORMAL)) {

         avio_seek(io_context, apng->acTL_offset, SEEK_SET);
 
         AV_WB32(buf, apng->frame_number);
         AV_WB32(buf + 4, apng->plays);
         apng_write_chunk(io_context, MKBETAG('a', 'c', 'T', 'L'), buf, 8);
     }
 

     av_freep(&apng->extra_data);
     apng->extra_data = 0;
 

     return 0;
 }
 
 #define OFFSET(x) offsetof(APNGMuxContext, x)
 #define ENC AV_OPT_FLAG_ENCODING_PARAM
 static const AVOption options[] = {
     { "plays", "Number of times to play the output: 0 - infinite loop, 1 - no loop", OFFSET(plays),
       AV_OPT_TYPE_INT, { .i64 = 1 }, 0, UINT_MAX, ENC },
     { "final_delay", "Force delay after the last frame", OFFSET(last_delay),
       AV_OPT_TYPE_RATIONAL, { .dbl = 0 }, 0, USHRT_MAX, ENC },
     { NULL },
 };
 
 static const AVClass apng_muxer_class = {
     .class_name = "APNG muxer",
     .item_name  = av_default_item_name,
     .version    = LIBAVUTIL_VERSION_INT,
     .option     = options,
 };
 
 AVOutputFormat ff_apng_muxer = {
     .name           = "apng",
     .long_name      = NULL_IF_CONFIG_SMALL("Animated Portable Network Graphics"),
     .mime_type      = "image/png",

     .extensions     = "apng",

     .priv_data_size = sizeof(APNGMuxContext),
     .audio_codec    = AV_CODEC_ID_NONE,
     .video_codec    = AV_CODEC_ID_APNG,
     .write_header   = apng_write_header,
     .write_packet   = apng_write_packet,
     .write_trailer  = apng_write_trailer,
     .priv_class     = &apng_muxer_class,
     .flags          = AVFMT_VARIABLE_FPS,
 };