/*

 * FITS demuxer

 * Copyright (c) 2017 Paras Chadha

 *

 * 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

 * FITS demuxer.

 */

#include "demux.h"

#include "internal.h"

#include "libavutil/opt.h"

#include "libavcodec/fits.h"

#define FITS_BLOCK_SIZE 2880

typedef struct FITSContext {

    const AVClass *class;

    AVRational framerate;

    int first_image;

} FITSContext;

static int fits_probe(const AVProbeData *p)

{

    const uint8_t *b = p->buf;

    if (!memcmp(b, "SIMPLE  =                    T", 30))

        return AVPROBE_SCORE_MAX - 1;

    return 0;

}

static int fits_read_header(AVFormatContext *s)

{

    AVStream *st;

    FITSContext * fits = s->priv_data;

    st = avformat_new_stream(s, NULL);

    if (!st)

        return AVERROR(ENOMEM);

    st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;

    st->codecpar->codec_id = AV_CODEC_ID_FITS;

    avpriv_set_pts_info(st, 64, fits->framerate.den, fits->framerate.num);

    fits->first_image = 1;

    return 0;

}

/**

 * Parses header and checks that the current HDU contains image or not

 * It also stores the header in the avbuf and stores the size of data part in data_size

 * @param s pointer to AVFormat Context

 * @param fits pointer to FITSContext

 * @param header pointer to FITSHeader

 * @param pkt pointer to AVPacket to store the header

 * @param data_size to store the size of data part

 * @return 1 if image found, 0 if any other extension and AVERROR code otherwise

 */

static int is_image(AVFormatContext *s, FITSContext *fits, FITSHeader *header,

                    AVPacket *pkt, uint64_t *data_size)

{

    int i, ret, image = 0;

    int64_t size = 0, t;

    do {

        const uint8_t *buf, *buf_end;

        ret = av_append_packet(s->pb, pkt, FITS_BLOCK_SIZE);

        if (ret < 0) {

            return ret;

        } else if (ret < FITS_BLOCK_SIZE) {

            return AVERROR_INVALIDDATA;

        }

        ret = 0;

        buf_end = pkt->data + pkt->size;

        buf     = buf_end - FITS_BLOCK_SIZE;

        while(!ret && buf < buf_end) {

            ret = avpriv_fits_header_parse_line(s, header, buf, NULL);

            buf += 80;

        }

    } while (!ret);

    if (ret < 0)

        return ret;

    image = fits->first_image || header->image_extension;

    fits->first_image = 0;

    if (header->groups) {

        image = 0;

        if (header->naxis > 1)

            size = 1;

    } else if (header->naxis) {

        size = header->naxisn[0];

    } else {

        image = 0;

    }

    for (i = 1; i < header->naxis; i++) {

        if(size && header->naxisn[i] > UINT64_MAX / size)

            return AVERROR_INVALIDDATA;

        size *= header->naxisn[i];

    }

    if(header->pcount > UINT64_MAX - size)

        return AVERROR_INVALIDDATA;

    size += header->pcount;

    t = (abs(header->bitpix) >> 3) * ((int64_t) header->gcount);

    if(size && t > INT64_MAX / size)

        return AVERROR_INVALIDDATA;

    size *= t;

    if (!size) {

        image = 0;

    } else {

        if(FITS_BLOCK_SIZE - 1 > INT64_MAX - size)

            return AVERROR_INVALIDDATA;

        size = ((size + FITS_BLOCK_SIZE - 1) / FITS_BLOCK_SIZE) * FITS_BLOCK_SIZE;

    }

    *data_size = size;

    return image;

}

static int fits_read_packet(AVFormatContext *s, AVPacket *pkt)

{

    uint64_t size;

    FITSContext *fits = s->priv_data;

    FITSHeader header;

    int ret;

    if (fits->first_image) {

        avpriv_fits_header_init(&header, STATE_SIMPLE);

    } else {

        avpriv_fits_header_init(&header, STATE_XTENSION);

    }

    while ((ret = is_image(s, fits, &header, pkt, &size)) == 0) {

        int64_t pos = avio_skip(s->pb, size);

        if (pos < 0)

            return pos;

        avpriv_fits_header_init(&header, STATE_XTENSION);

        av_packet_unref(pkt);

    }

    if (ret < 0)

        return ret;

    pkt->stream_index = 0;

    pkt->flags       |= AV_PKT_FLAG_KEY;

    pkt->duration     = 1;

    // Header is sent with the first line removed...

    pkt->data        += 80;

    pkt->size        -= 80;

    if (size > INT_MAX - AV_INPUT_BUFFER_PADDING_SIZE - pkt->size)

        return AVERROR(ERANGE);

    ret = av_append_packet(s->pb, pkt, size);

    if (ret < 0)

        return ret;

    return 0;

}

static const AVOption fits_options[] = {

    { "framerate", "set the framerate", offsetof(FITSContext, framerate), AV_OPT_TYPE_VIDEO_RATE, {.str = "1"}, 0, INT_MAX, AV_OPT_FLAG_DECODING_PARAM},

    { NULL },

};

static const AVClass fits_demuxer_class = {

    .class_name = "FITS demuxer",

    .item_name  = av_default_item_name,

    .option     = fits_options,

    .version    = LIBAVUTIL_VERSION_INT,

    .category   = AV_CLASS_CATEGORY_DEMUXER,

};

const FFInputFormat ff_fits_demuxer = {

    .p.name         = "fits",

    .p.long_name    = NULL_IF_CONFIG_SMALL("Flexible Image Transport System"),

    .p.priv_class   = &fits_demuxer_class,

    .p.flags        = AVFMT_NOTIMESTAMPS,

    .priv_data_size = sizeof(FITSContext),

    .read_probe     = fits_probe,

    .read_header    = fits_read_header,

    .read_packet    = fits_read_packet,

};