/*
 * This file is part of mpv.
 *
 * mpv is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * mpv 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with mpv.  If not, see <http://www.gnu.org/licenses/>.
 */

// Note: just wraps libass, and makes the subtitle track available though
//       sh_sub->track. It doesn't produce packets and doesn't support seeking.

#include <ass/ass.h>
#include <ass/ass_types.h>

#include "options/options.h"
#include "common/msg.h"
#include "misc/charset_conv.h"
#include "stream/stream.h"
#include "demux.h"

#define PROBE_SIZE (8 * 1024)

static void message_callback(int level, const char *format, va_list va, void *ctx)
{
    // ignore
}

static int d_check_file(struct demuxer *demuxer, enum demux_check check)
{
    const char *user_cp = demuxer->opts->sub_cp;
    struct stream *s = demuxer->stream;
    struct mp_log *log = demuxer->log;

    if (!demuxer->params || !demuxer->params->expect_subtitle)
        return -1;

    if (check >= DEMUX_CHECK_UNSAFE) {
        ASS_Library *lib = ass_library_init();
        if (!lib)
            return -1;
        ass_set_message_cb(lib, message_callback, NULL);

        // Probe by loading a part of the beginning of the file with libass.
        // Incomplete scripts are usually ok, and we hope libass is not verbose
        // when dealing with (from its perspective) completely broken binary
        // garbage.

        bstr buf = stream_peek(s, PROBE_SIZE);
        // Older versions of libass will overwrite the input buffer, and despite
        // passing length, expect a 0 termination.
        void *tmp = talloc_size(NULL, buf.len + 1);
        memcpy(tmp, buf.start, buf.len);
        buf.start = tmp;
        buf.start[buf.len] = '\0';
        bstr cbuf = mp_charset_guess_and_conv_to_utf8(log, buf, user_cp,
                                                      MP_ICONV_ALLOW_CUTOFF);
        if (cbuf.start == NULL)
            cbuf = buf;
        ASS_Track *track = ass_read_memory(lib, cbuf.start, cbuf.len, NULL);
        bool ok = !!track;
        if (cbuf.start != buf.start)
            talloc_free(cbuf.start);
        talloc_free(buf.start);
        if (track)
            ass_free_track(track);
        ass_library_done(lib);
        if (!ok)
            return -1;
    }

    // Actually load the full thing.

    bstr buf = stream_read_complete(s, NULL, 100000000);
    if (!buf.start) {
        MP_ERR(demuxer, "Refusing to load subtitle file "
                "larger than 100 MB: %s\n", demuxer->filename);
        return -1;
    }
    bstr cbuf = mp_charset_guess_and_conv_to_utf8(log, buf, user_cp,
                                                  MP_ICONV_VERBOSE);
    if (cbuf.start == NULL)
        cbuf = buf;
    if (cbuf.start != buf.start)
        talloc_free(buf.start);
    talloc_steal(demuxer, cbuf.start);

    struct sh_stream *sh = new_sh_stream(demuxer, STREAM_SUB);
    sh->codec = "ass";
    sh->sub->extradata = cbuf.start;
    sh->sub->extradata_len = cbuf.len;

    demuxer->seekable = true;

    return 0;
}

const struct demuxer_desc demuxer_desc_libass = {
    .name = "libass",
    .desc = "ASS/SSA subtitles (libass)",
    .open = d_check_file,
};