/*
  * FITS image encoder
  * 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 image encoder
  *
  * Specification: https://fits.gsfc.nasa.gov/fits_standard.html Version 3.0
  *
  * RGBA images are encoded as planes in RGBA order. So, NAXIS3 is 3 or 4 for them.
  * Also CTYPE3 = 'RGB ' is added to the header to distinguish them from 3d images.
  */
 
 #include "libavutil/intreadwrite.h"
 #include "avcodec.h"
 #include "bytestream.h"
 #include "internal.h"
 
 static int fits_encode_frame(AVCodecContext *avctx, AVPacket *pkt,
                             const AVFrame *pict, int *got_packet)
 {
     AVFrame * const p = (AVFrame *)pict;
     uint8_t *bytestream, *bytestream_start, *ptr;
     const uint16_t flip = (1 << 15);
     uint64_t data_size = 0, padded_data_size = 0;
     int ret, bitpix, naxis3 = 1, i, j, k, bytes_left;
     int map[] = {2, 0, 1, 3}; // mapping from GBRA -> RGBA as RGBA is to be stored in FITS file..
 
     switch (avctx->pix_fmt) {
     case AV_PIX_FMT_GRAY8:
     case AV_PIX_FMT_GRAY16BE:
         map[0] = 0; // grayscale images should be directly mapped
         if (avctx->pix_fmt == AV_PIX_FMT_GRAY8) {
             bitpix = 8;
         } else {
             bitpix = 16;
         }
         break;
     case AV_PIX_FMT_GBRP:
     case AV_PIX_FMT_GBRAP:
         bitpix = 8;
         if (avctx->pix_fmt == AV_PIX_FMT_GBRP) {
             naxis3 = 3;
         } else {
             naxis3 = 4;
         }
         break;
     case AV_PIX_FMT_GBRP16BE:
     case AV_PIX_FMT_GBRAP16BE:
         bitpix = 16;
         if (avctx->pix_fmt == AV_PIX_FMT_GBRP16BE) {
             naxis3 = 3;
         } else {
             naxis3 = 4;
         }
         break;
     default:
         av_log(avctx, AV_LOG_ERROR, "unsupported pixel format\n");
         return AVERROR(EINVAL);
     }
 
     data_size = (bitpix >> 3) * avctx->height * avctx->width * naxis3;
     padded_data_size = ((data_size + 2879) / 2880 ) * 2880;
 
     if ((ret = ff_alloc_packet2(avctx, pkt, padded_data_size, 0)) < 0)
         return ret;
 
     bytestream_start =
     bytestream       = pkt->data;
 
     for (k = 0; k < naxis3; k++) {
         for (i = 0; i < avctx->height; i++) {
             ptr = p->data[map[k]] + (avctx->height - i - 1) * p->linesize[map[k]];
             if (bitpix == 16) {
                 for (j = 0; j < avctx->width; j++) {
                     // subtracting bzero is equivalent to first bit flip
                     bytestream_put_be16(&bytestream, AV_RB16(ptr) ^ flip);
                     ptr += 2;
                 }
             } else {
                 memcpy(bytestream, ptr, avctx->width);
                 bytestream += avctx->width;
             }
         }
     }
 
     bytes_left = padded_data_size - data_size;
     memset(bytestream, 0, bytes_left);
     bytestream += bytes_left;
 
     pkt->size   = bytestream - bytestream_start;
     pkt->flags |= AV_PKT_FLAG_KEY;
     *got_packet = 1;
 
     return 0;
 }
 
 AVCodec ff_fits_encoder = {
     .name           = "fits",
     .long_name      = NULL_IF_CONFIG_SMALL("Flexible Image Transport System"),
     .type           = AVMEDIA_TYPE_VIDEO,
     .id             = AV_CODEC_ID_FITS,
     .encode2        = fits_encode_frame,
     .pix_fmts       = (const enum AVPixelFormat[]) { AV_PIX_FMT_GBRAP16BE,
                                                      AV_PIX_FMT_GBRP16BE,
                                                      AV_PIX_FMT_GBRP,
                                                      AV_PIX_FMT_GBRAP,
                                                      AV_PIX_FMT_GRAY16BE,
                                                      AV_PIX_FMT_GRAY8,
                                                      AV_PIX_FMT_NONE },
 };