/*

 * SubRip subtitle demuxer

 * Copyright (c) 2010  Aurelien Jacobs <aurel@gnuage.org>

 * Copyright (c) 2015  Clément Bœsch <u pkh me>

 *

 * 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 "demux.h"

#include "internal.h"

#include "subtitles.h"

#include "libavutil/bprint.h"

#include "libavutil/intreadwrite.h"

typedef struct {

    FFDemuxSubtitlesQueue q;

} SRTContext;

static int srt_probe(const AVProbeData *p)

{

    int v;

    char buf[64], *pbuf;

    FFTextReader tr;

    ff_text_init_buf(&tr, p->buf, p->buf_size);

    while (ff_text_peek_r8(&tr) == '\r' || ff_text_peek_r8(&tr) == '\n')

        ff_text_r8(&tr);

    /* Check if the first non-empty line is a number. We do not check what the

     * number is because in practice it can be anything.

     * Also, that number can be followed by random garbage, so we can not

     * unfortunately check that we only have a number. */

    if (ff_subtitles_read_line(&tr, buf, sizeof(buf)) < 0 ||

        strtol(buf, &pbuf, 10) < 0 || pbuf == buf)

        return 0;

    /* Check if the next line matches a SRT timestamp */

    if (ff_subtitles_read_line(&tr, buf, sizeof(buf)) < 0)

        return 0;

    pbuf = buf;

    if (buf[0] == '-')

        pbuf++;

    if (pbuf[0] >= '0' && pbuf[0] <= '9' && strstr(buf, " --> ")

        && sscanf(buf, "%*d:%*d:%*d%*1[,.]%*d --> %*d:%*d:%*d%*1[,.]%d", &v) == 1)

        return AVPROBE_SCORE_MAX;

    return 0;

}

struct event_info {

    int32_t x1, x2, y1, y2;

    int duration;

    int64_t pts;

    int64_t pos;

};

static int get_event_info(const char *line, struct event_info *ei)

{

    int hh1, mm1, ss1, ms1;

    int hh2, mm2, ss2, ms2;

    ei->x1 = ei->x2 = ei->y1 = ei->y2 = ei->duration = -1;

    ei->pts = AV_NOPTS_VALUE;

    ei->pos = -1;

    if (sscanf(line, "%d:%d:%d%*1[,.]%d --> %d:%d:%d%*1[,.]%d"

               "%*[ ]X1:%"PRId32" X2:%"PRId32" Y1:%"PRId32" Y2:%"PRId32,

               &hh1, &mm1, &ss1, &ms1,

               &hh2, &mm2, &ss2, &ms2,

               &ei->x1, &ei->x2, &ei->y1, &ei->y2) >= 8) {

        const int64_t start = (hh1*3600LL + mm1*60LL + ss1) * 1000LL + ms1;

        const int64_t end   = (hh2*3600LL + mm2*60LL + ss2) * 1000LL + ms2;

        ei->duration = end - start;

        ei->pts = start;

        return 0;

    }

    return -1;

}

static int add_event(FFDemuxSubtitlesQueue *q, AVBPrint *buf, char *line_cache,

                     const struct event_info *ei, int append_cache)

{

    if (append_cache && line_cache[0])

        av_bprintf(buf, "%s\n", line_cache);

    line_cache[0] = 0;

    if (!av_bprint_is_complete(buf))

        return AVERROR(ENOMEM);

    while (buf->len > 0 && buf->str[buf->len - 1] == '\n')

        buf->str[--buf->len] = 0;

    if (buf->len) {

        AVPacket *sub = ff_subtitles_queue_insert_bprint(q, buf, 0);

        if (!sub)

            return AVERROR(ENOMEM);

        av_bprint_clear(buf);

        sub->pos = ei->pos;

        sub->pts = ei->pts;

        sub->duration = ei->duration;

        if (ei->x1 != -1) {

            uint8_t *p = av_packet_new_side_data(sub, AV_PKT_DATA_SUBTITLE_POSITION, 16);

            if (p) {

                AV_WL32(p,      ei->x1);

                AV_WL32(p +  4, ei->y1);

                AV_WL32(p +  8, ei->x2);

                AV_WL32(p + 12, ei->y2);

            }

        }

    }

    return 0;

}

static int srt_read_header(AVFormatContext *s)

{

    SRTContext *srt = s->priv_data;

    AVBPrint buf;

    AVStream *st = avformat_new_stream(s, NULL);

    int res = 0;

    char line[4096], line_cache[4096];

    int has_event_info = 0;

    struct event_info ei;

    FFTextReader tr;

    ff_text_init_avio(s, &tr, s->pb);

    if (!st)

        return AVERROR(ENOMEM);

    avpriv_set_pts_info(st, 64, 1, 1000);

    st->codecpar->codec_type = AVMEDIA_TYPE_SUBTITLE;

    st->codecpar->codec_id   = AV_CODEC_ID_SUBRIP;

    av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);

    line_cache[0] = 0;

    while (!ff_text_eof(&tr)) {

        struct event_info tmp_ei;

        const int64_t pos = ff_text_pos(&tr);

        ptrdiff_t len = ff_subtitles_read_line(&tr, line, sizeof(line));

        if (len < 0)

            break;

        if (!len || !line[0])

            continue;

        if (get_event_info(line, &tmp_ei) < 0) {

            char *pline;

            if (!has_event_info)

                continue;

            if (line_cache[0]) {

                /* We got some cache and a new line so we assume the cached

                 * line was actually part of the payload */

                av_bprintf(&buf, "%s\n", line_cache);

                line_cache[0] = 0;

            }

            /* If the line doesn't start with a number, we assume it's part of

             * the payload, otherwise is likely an event number preceding the

             * timing information... but we can't be sure of this yet, so we

             * cache it */

            if (strtol(line, &pline, 10) < 0 || line == pline)

                av_bprintf(&buf, "%s\n", line);

            else

                strcpy(line_cache, line);

        } else {

            if (has_event_info) {

                /* We have the information of previous event, append it to the

                 * queue. We insert the cached line if and only if the payload

                 * is empty and the cached line is not a standalone number. */

                char *pline = NULL;

                const int standalone_number = strtol(line_cache, &pline, 10) >= 0 && pline && !*pline;

                res = add_event(&srt->q, &buf, line_cache, &ei, !buf.len && !standalone_number);

                if (res < 0)

                    goto end;

            } else {

                has_event_info = 1;

            }

            tmp_ei.pos = pos;

            ei = tmp_ei;

        }

    }

    /* Append the last event. Here we force the cache to be flushed, because a

     * trailing number is more likely to be genuine (for example a copyright

     * date) and not the event index of an inexistent event */

    if (has_event_info) {

        res = add_event(&srt->q, &buf, line_cache, &ei, 1);

        if (res < 0)

            goto end;

    }

    ff_subtitles_queue_finalize(s, &srt->q);

end:

    av_bprint_finalize(&buf, NULL);

    return res;

}

const FFInputFormat ff_srt_demuxer = {

    .p.name      = "srt",

    .p.long_name = NULL_IF_CONFIG_SMALL("SubRip subtitle"),

    .priv_data_size = sizeof(SRTContext),

    .flags_internal = FF_INFMT_FLAG_INIT_CLEANUP,

    .read_probe  = srt_probe,

    .read_header = srt_read_header,

    .read_packet = ff_subtitles_read_packet,

    .read_seek2  = ff_subtitles_read_seek,

    .read_close  = ff_subtitles_read_close,

};