/*

 * FITS image decoder

 * 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 decoder

 *

 * Specification: https://fits.gsfc.nasa.gov/fits_standard.html Version 3.0

 *

 * Support all 2d images alongwith, bzero, bscale and blank keywords.

 * RGBA images are supported as NAXIS3 = 3 or 4 i.e. Planes in RGBA order. Also CTYPE = 'RGB ' should be present.

 * Also to interpret data, values are linearly scaled using min-max scaling but not RGB images.

 */

#include "avcodec.h"

#include "codec_internal.h"

#include "decode.h"

#include <float.h>

#include "libavutil/intreadwrite.h"

#include "libavutil/intfloat.h"

#include "libavutil/dict.h"

#include "libavutil/opt.h"

#include "fits.h"

typedef struct FITSContext {

    const AVClass *class;

    int blank_val;

} FITSContext;

/**

 * Calculate the data_min and data_max values from the data.

 * This is called if the values are not present in the header.

 * @param ptr8 pointer to the data

 * @param header pointer to the header

 * @param end pointer to end of packet

 * @return 0 if calculated successfully otherwise AVERROR_INVALIDDATA

 */

static int fill_data_min_max(const uint8_t *ptr8, FITSHeader *header, const uint8_t *end)

{

    uint8_t t8;

    int16_t t16;

    int32_t t32;

    int64_t t64;

    float tflt;

    double tdbl;

    int i, j;

    header->data_min = DBL_MAX;

    header->data_max = -DBL_MAX;

    switch (header->bitpix) {

#define CASE_N(a, t, rd) \

    case a: \

        for (i = 0; i < header->naxisn[1]; i++) { \

            for (j = 0; j < header->naxisn[0]; j++) { \

                t = rd; \

                if (!header->blank_found || t != header->blank) { \

                    if (t > header->data_max) \

                        header->data_max = t; \

                    if (t < header->data_min) \

                        header->data_min = t; \

                } \

                ptr8 += abs(a) >> 3; \

            } \

        } \

        break

        CASE_N(-64, tdbl, av_int2double(AV_RB64(ptr8)));

        CASE_N(-32, tflt, av_int2float(AV_RB32(ptr8)));

        CASE_N(8, t8, ptr8[0]);

        CASE_N(16, t16, AV_RB16(ptr8));

        CASE_N(32, t32, AV_RB32(ptr8));

        CASE_N(64, t64, AV_RB64(ptr8));

        default:

            return AVERROR_INVALIDDATA;

    }

    return 0;

}

/**

 * Read the fits header and store the values in FITSHeader pointed by header

 * @param avctx AVCodec context

 * @param ptr pointer to pointer to the data

 * @param header pointer to the FITSHeader

 * @param end pointer to end of packet

 * @param metadata pointer to pointer to AVDictionary to store metadata

 * @return 0 if calculated successfully otherwise AVERROR_INVALIDDATA

 */

static int fits_read_header(AVCodecContext *avctx, const uint8_t **ptr, FITSHeader *header,

                            const uint8_t *end, AVDictionary **metadata)

{

    const uint8_t *ptr8 = *ptr;

    int lines_read, bytes_left, i, ret;

    size_t size;

    lines_read = 1; // to account for first header line, SIMPLE or XTENSION which is not included in packet...

    avpriv_fits_header_init(header, STATE_BITPIX);

    do {

        if (end - ptr8 < 80)

            return AVERROR_INVALIDDATA;

        ret = avpriv_fits_header_parse_line(avctx, header, ptr8, &metadata);

        ptr8 += 80;

        lines_read++;

    } while (!ret);

    if (ret < 0)

        return ret;

    bytes_left = (((lines_read + 35) / 36) * 36 - lines_read) * 80;

    if (end - ptr8 < bytes_left)

        return AVERROR_INVALIDDATA;

    ptr8 += bytes_left;

    if (header->rgb && (header->naxis != 3 || (header->naxisn[2] != 3 && header->naxisn[2] != 4))) {

        av_log(avctx, AV_LOG_ERROR, "File contains RGB image but NAXIS = %d and NAXIS3 = %d\n", header->naxis, header->naxisn[2]);

        return AVERROR_INVALIDDATA;

    }

    if (!header->rgb && header->naxis != 2) {

        av_log(avctx, AV_LOG_ERROR, "unsupported number of dimensions, NAXIS = %d\n", header->naxis);

        return AVERROR_INVALIDDATA;

    }

    if (header->blank_found && (header->bitpix == -32 || header->bitpix == -64)) {

        av_log(avctx, AV_LOG_WARNING, "BLANK keyword found but BITPIX = %d\n. Ignoring BLANK", header->bitpix);

        header->blank_found = 0;

    }

    size = abs(header->bitpix) >> 3;

    for (i = 0; i < header->naxis; i++) {

        if (size == 0 || header->naxisn[i] > SIZE_MAX / size) {

            av_log(avctx, AV_LOG_ERROR, "unsupported size of FITS image");

            return AVERROR_INVALIDDATA;

        }

        size *= header->naxisn[i];

    }

    if (end - ptr8 < size)

        return AVERROR_INVALIDDATA;

    *ptr = ptr8;

    if (!header->rgb && (!header->data_min_found || !header->data_max_found)) {

        ret = fill_data_min_max(ptr8, header, end);

        if (ret < 0) {

            av_log(avctx, AV_LOG_ERROR, "invalid BITPIX, %d\n", header->bitpix);

            return ret;

        }

    } else {

        /*

         * instead of applying bscale and bzero to every element,

         * we can do inverse transformation on data_min and data_max

         */

        header->data_min = (header->data_min - header->bzero) / header->bscale;

        header->data_max = (header->data_max - header->bzero) / header->bscale;

    }

    if (!header->rgb && header->data_min >= header->data_max) {

        if (header->data_min > header->data_max) {

            av_log(avctx, AV_LOG_ERROR, "data min/max (%g %g) is invalid\n", header->data_min, header->data_max);

            return AVERROR_INVALIDDATA;

        }

        av_log(avctx, AV_LOG_WARNING, "data min/max indicates a blank image\n");

        header->data_max ++;

    }

    return 0;

}

static int fits_decode_frame(AVCodecContext *avctx, AVFrame *p,

                             int *got_frame, AVPacket *avpkt)

{

    const uint8_t *ptr8 = avpkt->data, *end;

    uint8_t t8;

    int16_t t16;

    int32_t t32;

    int64_t t64;

    float   tflt;

    double  tdbl;

    int ret, i, j, k;

    const int map[] = {2, 0, 1, 3}; // mapping from GBRA -> RGBA as RGBA is to be stored in FITS file..

    uint8_t *dst8;

    uint16_t *dst16;

    uint64_t t;

    FITSHeader header;

    FITSContext * fitsctx = avctx->priv_data;

    end = ptr8 + avpkt->size;

    p->metadata = NULL;

    ret = fits_read_header(avctx, &ptr8, &header, end, &p->metadata);

    if (ret < 0)

        return ret;

    if (header.rgb) {

        if (header.bitpix == 8) {

            if (header.naxisn[2] == 3) {

                avctx->pix_fmt = AV_PIX_FMT_GBRP;

            } else {

                avctx->pix_fmt = AV_PIX_FMT_GBRAP;

            }

        } else if (header.bitpix == 16) {

            if (header.naxisn[2] == 3) {

                avctx->pix_fmt = AV_PIX_FMT_GBRP16;

            } else {

                avctx->pix_fmt = AV_PIX_FMT_GBRAP16;

            }

        } else {

            av_log(avctx, AV_LOG_ERROR, "unsupported BITPIX = %d\n", header.bitpix);

            return AVERROR_INVALIDDATA;

        }

    } else {

        if (header.bitpix == 8) {

            avctx->pix_fmt = AV_PIX_FMT_GRAY8;

        } else {

            avctx->pix_fmt = AV_PIX_FMT_GRAY16;

        }

    }

    if ((ret = ff_set_dimensions(avctx, header.naxisn[0], header.naxisn[1])) < 0)

        return ret;

    if ((ret = ff_get_buffer(avctx, p, 0)) < 0)

        return ret;

    /*

     * FITS stores images with bottom row first. Therefore we have

     * to fill the image from bottom to top.

     */

    if (header.rgb) {

        switch(header.bitpix) {

#define CASE_RGB(cas, dst, type, dref) \

    case cas: \

        for (k = 0; k < header.naxisn[2]; k++) { \

            for (i = 0; i < avctx->height; i++) { \

                dst = (type *) (p->data[map[k]] + (avctx->height - i - 1) * p->linesize[map[k]]); \

                for (j = 0; j < avctx->width; j++) { \

                    t32 = dref(ptr8); \

                    if (!header.blank_found || t32 != header.blank) { \

                        t = t32 * header.bscale + header.bzero; \

                    } else { \

                        t = fitsctx->blank_val; \

                    } \

                    *dst++ = (type) t; \

                    ptr8 += cas >> 3; \

                } \

            } \

        } \

        break

            CASE_RGB(8, dst8, uint8_t, *);

            CASE_RGB(16, dst16, uint16_t, AV_RB16);

        }

    } else {

        double scale = header.data_max - header.data_min;

        if (scale <= 0 || !isfinite(scale)) {

            scale = 1;

        }

        scale = 1/scale;

        switch (header.bitpix) {

#define CASE_GRAY(cas, dst, type, t, rd) \

    case cas: \

        for (i = 0; i < avctx->height; i++) { \

            dst = (type *) (p->data[0] + (avctx->height-i-1)* p->linesize[0]); \

            for (j = 0; j < avctx->width; j++) { \

                t = rd; \

                if (!header.blank_found || t != header.blank) { \

                    *dst++ = lrint(((t - header.data_min) * ((1 << (sizeof(type) * 8)) - 1)) * scale); \

                } else { \

                    *dst++ = fitsctx->blank_val; \

                } \

                ptr8 += abs(cas) >> 3; \

            } \

        } \

        break

            CASE_GRAY(-64, dst16, uint16_t, tdbl, av_int2double(AV_RB64(ptr8)));

            CASE_GRAY(-32, dst16, uint16_t, tflt, av_int2float(AV_RB32(ptr8)));

            CASE_GRAY(8, dst8, uint8_t, t8, ptr8[0]);

            CASE_GRAY(16, dst16, uint16_t, t16, AV_RB16(ptr8));

            CASE_GRAY(32, dst16, uint16_t, t32, AV_RB32(ptr8));

            CASE_GRAY(64, dst16, uint16_t, t64, AV_RB64(ptr8));

            default:

                av_log(avctx, AV_LOG_ERROR, "invalid BITPIX, %d\n", header.bitpix);

                return AVERROR_INVALIDDATA;

        }

    }

    *got_frame = 1;

    return avpkt->size;

}

static const AVOption fits_options[] = {

    { "blank_value", "value that is used to replace BLANK pixels in data array", offsetof(FITSContext, blank_val), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 65535, AV_OPT_FLAG_DECODING_PARAM | AV_OPT_FLAG_VIDEO_PARAM},

    { NULL },

};

static const AVClass fits_decoder_class = {

    .class_name = "FITS decoder",

    .item_name  = av_default_item_name,

    .option     = fits_options,

    .version    = LIBAVUTIL_VERSION_INT,

    .category   = AV_CLASS_CATEGORY_DECODER,

};

const FFCodec ff_fits_decoder = {

    .p.name         = "fits",

    .p.type         = AVMEDIA_TYPE_VIDEO,

    .p.id           = AV_CODEC_ID_FITS,

    .p.capabilities = AV_CODEC_CAP_DR1,

    CODEC_LONG_NAME("Flexible Image Transport System"),

    .p.priv_class   = &fits_decoder_class,

    .priv_data_size = sizeof(FITSContext),

    FF_CODEC_DECODE_CB(fits_decode_frame),

};