/*
  * 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 "libavutil/intreadwrite.h"
 #include "internal.h"
 #include "libavutil/opt.h"
 #include "libavcodec/fits.h"
 #include "libavutil/bprint.h"
 
 #define FITS_BLOCK_SIZE 2880
 
 typedef struct FITSContext {
     const AVClass *class;
     AVRational framerate;
     int first_image;
     int64_t pts;
 } FITSContext;
 
 static int fits_probe(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->pts = 0;
     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 avbuf pointer to AVBPrint 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_INVALIDDATA otherwise
  */
 static int64_t is_image(AVFormatContext *s, FITSContext *fits, FITSHeader *header,
                          AVBPrint *avbuf, uint64_t *data_size)
 {
     int i, ret, image = 0;
     char buf[FITS_BLOCK_SIZE] = { 0 };
     int64_t buf_size = 0, size = 0, t;
 
     do {
         ret = avio_read(s->pb, buf, FITS_BLOCK_SIZE);
         if (ret < 0) {
             return ret;
         } else if (ret < FITS_BLOCK_SIZE) {
             return AVERROR_INVALIDDATA;
         }
 
         av_bprint_append_data(avbuf, buf, FITS_BLOCK_SIZE);
         ret = 0;
         buf_size = 0;
         while(!ret && buf_size < FITS_BLOCK_SIZE) {
             ret = avpriv_fits_header_parse_line(s, header, buf + buf_size, NULL);
             buf_size += 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 > UINT64_MAX / size)
         return AVERROR_INVALIDDATA;
     size *= t;
 
     if (!size) {
         image = 0;
     } else {
         if(FITS_BLOCK_SIZE - 1 > UINT64_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)
 {
     int64_t pos, ret;
     uint64_t size;
     FITSContext *fits = s->priv_data;
     FITSHeader header;
     AVBPrint avbuf;
     char *buf;
 
     if (fits->first_image) {
         avpriv_fits_header_init(&header, STATE_SIMPLE);
     } else {
         avpriv_fits_header_init(&header, STATE_XTENSION);
     }
 
     av_bprint_init(&avbuf, FITS_BLOCK_SIZE, AV_BPRINT_SIZE_UNLIMITED);
     while ((ret = is_image(s, fits, &header, &avbuf, &size)) == 0) {
         pos = avio_skip(s->pb, size);
         if (pos < 0)
             return pos;
 
         av_bprint_finalize(&avbuf, NULL);
         av_bprint_init(&avbuf, FITS_BLOCK_SIZE, AV_BPRINT_SIZE_UNLIMITED);
         avpriv_fits_header_init(&header, STATE_XTENSION);
     }
     if (ret < 0)
         goto fail;
 
     if (!av_bprint_is_complete(&avbuf)) {
         ret = AVERROR(ENOMEM);
         goto fail;
     }
 
     // Header is sent with the first line removed...
     ret = av_new_packet(pkt, avbuf.len - 80 + size);
     if (ret < 0)
         goto fail;
 
     pkt->stream_index = 0;
     pkt->flags |= AV_PKT_FLAG_KEY;
 
     ret = av_bprint_finalize(&avbuf, &buf);
     if (ret < 0) {
         av_packet_unref(pkt);
         return ret;
     }
 
     memcpy(pkt->data, buf + 80, avbuf.len - 80);
     pkt->size = avbuf.len - 80;
     av_freep(&buf);
     ret = avio_read(s->pb, pkt->data + pkt->size, size);
     if (ret < 0) {
         av_packet_unref(pkt);
         return ret;
     }
 
     pkt->size += ret;
     pkt->pts = fits->pts;
     fits->pts++;
 
     return 0;
 
 fail:
     av_bprint_finalize(&avbuf, NULL);
     return ret;
 }
 
 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,
 };
 
 AVInputFormat ff_fits_demuxer = {
     .name           = "fits",
     .long_name      = NULL_IF_CONFIG_SMALL("Flexible Image Transport System"),
     .priv_data_size = sizeof(FITSContext),
     .read_probe     = fits_probe,
     .read_header    = fits_read_header,
     .read_packet    = fits_read_packet,
     .priv_class     = &fits_demuxer_class,
     .raw_codec_id   = AV_CODEC_ID_FITS,
 };