/*

 * Copyright (c) 2012 Clément Bœsch

 *

 * 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

 * WebVTT subtitle decoder

 * @see https://www.w3.org/TR/webvtt1/

 * @todo need to support extended markups and cue settings

 */

#include "avcodec.h"

#include "ass.h"

#include "codec_internal.h"

#include "libavutil/bprint.h"

static const struct {

    const char *from;

    const char *to;

} webvtt_tag_replace[] = {

    {"{", "\\{{}"}, {"\\", "\\\xe2\x81\xa0"}, // escape to avoid ASS markup conflicts

    {"&gt;", ">"}, {"&lt;", "<"},

    {"‎", "\xe2\x80\x8e"}, {"‏", "\xe2\x80\x8f"},

    {"&", "&"}, {" ", "\\h"},

};

static const struct {

    const char from[6];

    const char to[6];

} webvtt_valid_tags[] = {

    {"i", "{\\i1}"}, {"/i", "{\\i0}"},

    {"b", "{\\b1}"}, {"/b", "{\\b0}"},

    {"u", "{\\u1}"}, {"/u", "{\\u0}"},

};

static int webvtt_event_to_ass(AVBPrint *buf, const char *p)

{

    int i, again = 0;

    while (*p) {

        if (*p == '<') {

            const char *tag_end = strchr(p, '>');

            ptrdiff_t len;

            if (!tag_end)

                break;

            len = tag_end - p + 1;

            for (i = 0; i < FF_ARRAY_ELEMS(webvtt_valid_tags); i++) {

                const char *from = webvtt_valid_tags[i].from;

                if(!strncmp(p + 1, from, strlen(from))) {

                    av_bprintf(buf, "%s", webvtt_valid_tags[i].to);

                    break;

                }

            }

            p += len;

            again = 1;

        }

        for (i = 0; i < FF_ARRAY_ELEMS(webvtt_tag_replace); i++) {

            const char *from = webvtt_tag_replace[i].from;

            const size_t len = strlen(from);

            if (!strncmp(p, from, len)) {

                av_bprintf(buf, "%s", webvtt_tag_replace[i].to);

                p += len;

                again = 1;

                break;

            }

        }

        if (again) {

            again = 0;

            continue;

        }

        if (p[0] == '\n' && p[1])

            av_bprintf(buf, "\\N");

        else if (*p != '\r')

            av_bprint_chars(buf, *p, 1);

        p++;

    }

    return 0;

}

static int webvtt_decode_frame(AVCodecContext *avctx, AVSubtitle *sub,

                               int *got_sub_ptr, const AVPacket *avpkt)

{

    int ret = 0;

    const char *ptr = avpkt->data;

    FFASSDecoderContext *s = avctx->priv_data;

    AVBPrint buf;

    av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);

    if (ptr && avpkt->size > 0 && !webvtt_event_to_ass(&buf, ptr))

        ret = ff_ass_add_rect(sub, buf.str, s->readorder++, 0, NULL, NULL);

    av_bprint_finalize(&buf, NULL);

    if (ret < 0)

        return ret;

    *got_sub_ptr = sub->num_rects > 0;

    return avpkt->size;

}

const FFCodec ff_webvtt_decoder = {

    .p.name         = "webvtt",

    CODEC_LONG_NAME("WebVTT subtitle"),

    .p.type         = AVMEDIA_TYPE_SUBTITLE,

    .p.id           = AV_CODEC_ID_WEBVTT,

    FF_CODEC_DECODE_SUB_CB(webvtt_decode_frame),

    .init           = ff_ass_subtitle_header_default,

    .flush          = ff_ass_decoder_flush,

    .priv_data_size = sizeof(FFASSDecoderContext),

};