/*
  * 3GPP TS 26.245 Timed Text decoder
  * Copyright (c) 2012  Philip Langdale <philipl@overt.org>
  *
  * 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 "avcodec.h"
 #include "ass.h"
 #include "libavutil/avstring.h"
 #include "libavutil/common.h"
 #include "libavutil/bprint.h"
 #include "libavutil/intreadwrite.h"
 
 static int text_to_ass(AVBPrint *buf, const char *text, const char *text_end)
 {
     while (text < text_end) {
         switch (*text) {
         case '\r':
             break;
         case '\n':
             av_bprintf(buf, "\\N");
             break;
         default:
             av_bprint_chars(buf, *text, 1);
             break;
         }
         text++;
     }
 
     av_bprintf(buf, "\r\n");
     return 0;
 }
 
 static int mov_text_init(AVCodecContext *avctx) {
     /*
      * TODO: Handle the default text style.
      * NB: Most players ignore styles completely, with the result that
      * it's very common to find files where the default style is broken
      * and respecting it results in a worse experience than ignoring it.
      */
     return ff_ass_subtitle_header_default(avctx);
 }
 
 static int mov_text_decode_frame(AVCodecContext *avctx,
                             void *data, int *got_sub_ptr, AVPacket *avpkt)
 {
     AVSubtitle *sub = data;
     int ts_start, ts_end;
     AVBPrint buf;
     const char *ptr = avpkt->data;
     const char *end;
 

     if (!ptr || avpkt->size < 2)
         return AVERROR_INVALIDDATA;
 
     /*
      * A packet of size two with value zero is an empty subtitle
      * used to mark the end of the previous non-empty subtitle.
      * We can just drop them here as we have duration information
      * already. If the value is non-zero, then it's technically a
      * bad packet.
      */
     if (avpkt->size == 2)
         return AV_RB16(ptr) == 0 ? 0 : AVERROR_INVALIDDATA;

 
     /*
      * The first two bytes of the packet are the length of the text string
      * In complex cases, there are style descriptors appended to the string
      * so we can't just assume the packet size is the string size.
      */

     end = ptr + FFMIN(2 + AV_RB16(ptr), avpkt->size);

     ptr += 2;
 
     ts_start = av_rescale_q(avpkt->pts,
                             avctx->time_base,
                             (AVRational){1,100});
     ts_end   = av_rescale_q(avpkt->pts + avpkt->duration,
                             avctx->time_base,
                             (AVRational){1,100});
 
     // Note that the spec recommends lines be no longer than 2048 characters.
     av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
     text_to_ass(&buf, ptr, end);
 
     if (!av_bprint_is_complete(&buf))
         return AVERROR(ENOMEM);
 
     ff_ass_add_rect(sub, buf.str, ts_start, ts_end-ts_start, 0);
     *got_sub_ptr = sub->num_rects > 0;
     av_bprint_finalize(&buf, NULL);
     return avpkt->size;
 }
 
 AVCodec ff_movtext_decoder = {
     .name         = "mov_text",
     .long_name    = NULL_IF_CONFIG_SMALL("3GPP Timed Text subtitle"),
     .type         = AVMEDIA_TYPE_SUBTITLE,

     .id           = AV_CODEC_ID_MOV_TEXT,

     .init         = mov_text_init,
     .decode       = mov_text_decode_frame,
 };