/*

 * Copyright (c) 2021 Paul B Mahol

 *

 * 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

 */

#include "libavutil/common.h"

#include "libavutil/mem.h"

#include "avcodec.h"

#include "get_bits.h"

#include "bytestream.h"

#include "codec_internal.h"

#include "decode.h"

#define PALDATA_FOLLOWS_TILEDATA 4

#define HAVE_COMPRESSED_TILEMAP 32

#define HAVE_TILEMAP 128

typedef struct SGAVideoContext {

    GetByteContext gb;

    int metadata_size;

    int tiledata_size;

    int tiledata_offset;

    int tilemapdata_size;

    int tilemapdata_offset;

    int paldata_size;

    int paldata_offset;

    int palmapdata_offset;

    int palmapdata_size;

    int flags;

    int nb_pal;

    int nb_tiles;

    int tiles_w, tiles_h;

    int shift;

    int plus;

    int swap;

    uint32_t pal[256];

    uint8_t *tileindex_data;

    unsigned tileindex_size;

    uint8_t *palmapindex_data;

    unsigned palmapindex_size;

    uint8_t uncompressed[65536];

} SGAVideoContext;

static av_cold int sga_decode_init(AVCodecContext *avctx)

{

    avctx->pix_fmt = AV_PIX_FMT_PAL8;

    return 0;

}

static int decode_palette(GetByteContext *gb, uint32_t *pal)

{

    GetBitContext gbit;

    if (bytestream2_get_bytes_left(gb) < 18)

        return AVERROR_INVALIDDATA;

    memset(pal, 0, 16 * sizeof(*pal));

    (void)init_get_bits8(&gbit, gb->buffer, 18);

    for (int RGBIndex = 0; RGBIndex < 3; RGBIndex++) {

        for (int index = 0; index < 16; index++) {

            unsigned color = get_bits1(&gbit) << RGBIndex;

            pal[15 - index] |= color << (5 + 16);

        }

    }

    for (int RGBIndex = 0; RGBIndex < 3; RGBIndex++) {

        for (int index = 0; index < 16; index++) {

            unsigned color = get_bits1(&gbit) << RGBIndex;

            pal[15 - index] |= color << (5 + 8);

        }

    }

    for (int RGBIndex = 0; RGBIndex < 3; RGBIndex++) {

        for (int index = 0; index < 16; index++) {

            unsigned color = get_bits1(&gbit) << RGBIndex;

            pal[15 - index] |= color << (5 + 0);

        }

    }

    for (int index = 0; index < 16; index++)

        pal[index] = (0xFFU << 24) | pal[index] | (pal[index] >> 3);

    bytestream2_skip(gb, 18);

    return 0;

}

static int decode_index_palmap(SGAVideoContext *s, AVFrame *frame)

{

    const uint8_t *tt = s->tileindex_data;

    for (int y = 0; y < s->tiles_h; y++) {

        for (int x = 0; x < s->tiles_w; x++) {

            int pal_idx = s->palmapindex_data[y * s->tiles_w + x] * 16;

            uint8_t *dst = frame->data[0] + y * 8 * frame->linesize[0] + x * 8;

            for (int yy = 0; yy < 8; yy++) {

                for (int xx = 0; xx < 8; xx++)

                    dst[xx] = pal_idx + tt[xx];

                tt += 8;

                dst += frame->linesize[0];

            }

        }

    }

    return 0;

}

static int decode_index_tilemap(SGAVideoContext *s, AVFrame *frame)

{

    GetByteContext *gb = &s->gb, gb2;

    bytestream2_seek(gb, s->tilemapdata_offset, SEEK_SET);

    if (bytestream2_get_bytes_left(gb) < s->tilemapdata_size)

        return AVERROR_INVALIDDATA;

    gb2 = *gb;

    for (int y = 0; y < s->tiles_h; y++) {

        for (int x = 0; x < s->tiles_w; x++) {

            uint8_t tile[64];

            int tilemap = bytestream2_get_be16u(&gb2);

            int flip_x = (tilemap >> 11) & 1;

            int flip_y = (tilemap >> 12) & 1;

            int tindex = av_clip((tilemap & 511) - 1, 0, s->nb_tiles - 1);

            const uint8_t *tt = s->tileindex_data + tindex * 64;

            int pal_idx = ((tilemap >> 13) & 3) * 16;

            uint8_t *dst = frame->data[0] + y * 8 * frame->linesize[0] + x * 8;

            if (!flip_x && !flip_y) {

                memcpy(tile, tt, 64);

            } else if (flip_x && flip_y) {

                for (int i = 0; i < 8; i++) {

                    for (int j = 0; j < 8; j++)

                        tile[i * 8 + j] = tt[(7 - i) * 8 + 7 - j];

                }

            } else if (flip_x) {

                for (int i = 0; i < 8; i++) {

                    for (int j = 0; j < 8; j++)

                        tile[i * 8 + j] = tt[i * 8 + 7 - j];

                }

            } else {

                for (int i = 0; i < 8; i++) {

                    for (int j = 0; j < 8; j++)

                        tile[i * 8 + j] = tt[(7 - i) * 8 + j];

                }

            }

            for (int yy = 0; yy < 8; yy++) {

                for (int xx = 0; xx < 8; xx++)

                    dst[xx] = pal_idx + tile[xx + yy * 8];

                dst += frame->linesize[0];

            }

        }

    }

    return 0;

}

static int decode_index(SGAVideoContext *s, AVFrame *frame)

{

    const uint8_t *src = s->tileindex_data;

    uint8_t *dst = frame->data[0];

    for (int y = 0; y < frame->height; y += 8) {

        for (int x = 0; x < frame->width; x += 8) {

            for (int yy = 0; yy < 8; yy++) {

                for (int xx = 0; xx < 8; xx++)

                    dst[x + xx + yy * frame->linesize[0]] = src[xx];

                src += 8;

            }

        }

        dst += 8 * frame->linesize[0];

    }

    return 0;

}

static int lzss_decompress(AVCodecContext *avctx,

                           GetByteContext *gb, uint8_t *dst,

                           int dst_size, int shift, int plus)

{

    int oi = 0;

    while (bytestream2_get_bytes_left(gb) > 0 && oi < dst_size) {

        uint16_t displace, header = bytestream2_get_be16(gb);

        int count, offset;

        for (int i = 0; i < 16; i++) {

            switch (header >> 15) {

            case 0:

                if (oi + 2 < dst_size) {

                    dst[oi++] = bytestream2_get_byte(gb);

                    dst[oi++] = bytestream2_get_byte(gb);

                }

                break;

            case 1:

                displace = bytestream2_get_be16(gb);

                count = displace >> shift;

                offset = displace & ((1 << shift) - 1);

                if (displace == 0) {

                    while (bytestream2_get_bytes_left(gb) > 0 &&

                           oi < dst_size)

                        dst[oi++] = bytestream2_get_byte(gb);

                    return oi;

                }

                count += plus;

                if (offset <= 0)

                    offset = 1;

                if (oi < offset || oi + count * 2 > dst_size)

                    return AVERROR_INVALIDDATA;

                for (int j = 0; j < count * 2; j++) {

                    dst[oi] = dst[oi - offset];

                    oi++;

                }

                break;

            }

            header <<= 1;

        }

    }

    return AVERROR_INVALIDDATA;

}

static int decode_palmapdata(AVCodecContext *avctx)

{

    SGAVideoContext *s = avctx->priv_data;

    const int bits = (s->nb_pal + 1) / 2;

    GetByteContext *gb = &s->gb;

    GetBitContext pm;

    av_unused int ret;

    bytestream2_seek(gb, s->palmapdata_offset, SEEK_SET);

    if (bytestream2_get_bytes_left(gb) < s->palmapdata_size)

        return AVERROR_INVALIDDATA;

    ret = init_get_bits8(&pm, gb->buffer, s->palmapdata_size);

    av_assert1(ret >= 0);

    for (int y = 0; y < s->tiles_h; y++) {

        uint8_t *dst = s->palmapindex_data + y * s->tiles_w;

        for (int x = 0; x < s->tiles_w; x++)

            dst[x] = get_bits(&pm, bits);

        dst += s->tiles_w;

    }

    return 0;

}

static int decode_tiledata(AVCodecContext *avctx)

{

    SGAVideoContext *s = avctx->priv_data;

    GetByteContext *gb = &s->gb;

    GetBitContext tm;

    av_unused int ret;

    bytestream2_seek(gb, s->tiledata_offset, SEEK_SET);

    if (bytestream2_get_bytes_left(gb) < s->tiledata_size)

        return AVERROR_INVALIDDATA;

    ret = init_get_bits8(&tm, gb->buffer, s->tiledata_size);

    av_assert1(ret >= 0);

    for (int n = 0; n < s->nb_tiles; n++) {

        uint8_t *dst = s->tileindex_data + n * 64;

        for (int yy = 0; yy < 8; yy++) {

            for (int xx = 0; xx < 8; xx++)

                dst[xx] = get_bits(&tm, 4);

            dst += 8;

        }

    }

    for (int i = 0; i < s->nb_tiles && s->swap; i++) {

        uint8_t *dst = s->tileindex_data + i * 64;

        for (int j = 8; j < 64; j += 16) {

            for (int k = 0; k < 8; k += 2)

                FFSWAP(uint8_t, dst[j + k], dst[j+k+1]);

        }

    }

    return 0;

}

static int sga_decode_frame(AVCodecContext *avctx, AVFrame *frame,

                            int *got_frame, AVPacket *avpkt)

{

    SGAVideoContext *s = avctx->priv_data;

    GetByteContext *gb = &s->gb;

    int ret, type;

    if (avpkt->size <= 14)

        return AVERROR_INVALIDDATA;

    s->flags  = avpkt->data[8];

    s->nb_pal = avpkt->data[9];

    s->tiles_w = avpkt->data[10];

    s->tiles_h = avpkt->data[11];

    if (s->nb_pal > 4)

        return AVERROR_INVALIDDATA;

    if ((ret = ff_set_dimensions(avctx,

                                 s->tiles_w * 8,

                                 s->tiles_h * 8)) < 0)

        return ret;

    av_fast_padded_malloc(&s->tileindex_data, &s->tileindex_size,

                          avctx->width * avctx->height);

    if (!s->tileindex_data)

        return AVERROR(ENOMEM);

    av_fast_padded_malloc(&s->palmapindex_data, &s->palmapindex_size,

                          s->tiles_w * s->tiles_h);

    if (!s->palmapindex_data)

        return AVERROR(ENOMEM);

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

        return ret;

    bytestream2_init(gb, avpkt->data, avpkt->size);

    type = bytestream2_get_byte(gb);

    s->metadata_size = 12 + ((!!(s->flags & HAVE_TILEMAP)) * 2);

    s->nb_tiles = s->flags & HAVE_TILEMAP ? AV_RB16(avpkt->data + 12) : s->tiles_w * s->tiles_h;

    if (s->nb_tiles > s->tiles_w * s->tiles_h)

        return AVERROR_INVALIDDATA;

    av_log(avctx, AV_LOG_DEBUG, "type: %X flags: %X nb_tiles: %d\n", type, s->flags, s->nb_tiles);

    switch (type) {

    case 0xE7:

    case 0xCB:

    case 0xCD:

        s->swap = 1;

        s->shift = 12;

        s->plus = 1;

        break;

    case 0xC9:

        s->swap = 1;

        s->shift = 13;

        s->plus = 1;

        break;

    case 0xC8:

        s->swap = 1;

        s->shift = 13;

        s->plus = 0;

        break;

    case 0xC7:

        s->swap = 0;

        s->shift = 13;

        s->plus = 1;

        break;

    case 0xC6:

        s->swap = 0;

        s->shift = 13;

        s->plus = 0;

        break;

    }

    if (type == 0xE7) {

        int offset = s->metadata_size, left;

        int sizes[3];

        bytestream2_seek(gb, s->metadata_size, SEEK_SET);

        for (int i = 0; i < 3; i++)

            sizes[i] = bytestream2_get_be16(gb);

        for (int i = 0; i < 3; i++) {

            int size = sizes[i];

            int raw = size >> 15;

            size &= (1 << 15) - 1;

            if (raw) {

                if (bytestream2_get_bytes_left(gb) < size)

                    return AVERROR_INVALIDDATA;

                if (sizeof(s->uncompressed) - offset < size)

                    return AVERROR_INVALIDDATA;

                memcpy(s->uncompressed + offset, gb->buffer, size);

                bytestream2_skip(gb, size);

            } else {

                GetByteContext gb2;

                if (bytestream2_get_bytes_left(gb) < size)

                    return AVERROR_INVALIDDATA;

                bytestream2_init(&gb2, gb->buffer, size);

                ret = lzss_decompress(avctx, &gb2, s->uncompressed + offset,

                                      sizeof(s->uncompressed) - offset, s->shift, s->plus);

                if (ret < 0)

                    return ret;

                bytestream2_skip(gb, size);

                size = ret;

            }

            offset += size;

        }

        left = bytestream2_get_bytes_left(gb);

        if (sizeof(s->uncompressed) - offset < left)

            return AVERROR_INVALIDDATA;

        bytestream2_get_buffer(gb, s->uncompressed + offset, left);

        offset += left;

        bytestream2_init(gb, s->uncompressed, offset);

    }

    switch (type) {

    case 0xCD:

    case 0xCB:

    case 0xC9:

    case 0xC8:

    case 0xC7:

    case 0xC6:

        bytestream2_seek(gb, s->metadata_size, SEEK_SET);

        ret = lzss_decompress(avctx, gb, s->uncompressed + s->metadata_size,

                              sizeof(s->uncompressed) - s->metadata_size, s->shift, s->plus);

        if (ret < 0)

            return ret;

        bytestream2_init(gb, s->uncompressed, ret + s->metadata_size);

    case 0xE7:

    case 0xC1:

        s->tiledata_size = s->nb_tiles * 32;

        s->paldata_size = s->nb_pal * 18;

        s->tiledata_offset = s->flags & PALDATA_FOLLOWS_TILEDATA ? s->metadata_size : s->metadata_size + s->paldata_size;

        s->paldata_offset = s->flags & PALDATA_FOLLOWS_TILEDATA ? s->metadata_size + s->tiledata_size : s->metadata_size;

        s->palmapdata_offset = (s->flags & HAVE_TILEMAP) ? -1 : s->paldata_offset + s->paldata_size;

        s->palmapdata_size = (s->flags & HAVE_TILEMAP) || s->nb_pal < 2 ? 0 : (s->tiles_w * s->tiles_h * ((s->nb_pal + 1) / 2) + 7) / 8;

        s->tilemapdata_size = (s->flags & HAVE_TILEMAP) ? s->tiles_w * s->tiles_h * 2 : 0;

        s->tilemapdata_offset = (s->flags & HAVE_TILEMAP) ? s->paldata_offset + s->paldata_size: -1;

        bytestream2_seek(gb, s->paldata_offset, SEEK_SET);

        for (int n = 0; n < s->nb_pal; n++) {

            ret = decode_palette(gb, s->pal + 16 * n);

            if (ret < 0)

                return ret;

        }

        if (s->tiledata_size > 0) {

            ret = decode_tiledata(avctx);

            if (ret < 0)

                return ret;

        }

        if (s->palmapdata_size > 0) {

            ret = decode_palmapdata(avctx);

            if (ret < 0)

                return ret;

        }

        if (s->palmapdata_size > 0 && s->tiledata_size > 0) {

            ret = decode_index_palmap(s, frame);

            if (ret < 0)

                return ret;

        } else if (s->tilemapdata_size > 0 && s->tiledata_size > 0) {

            ret = decode_index_tilemap(s, frame);

            if (ret < 0)

                return ret;

        } else if (s->tiledata_size > 0) {

            ret = decode_index(s, frame);

            if (ret < 0)

                return ret;

        }

        break;

    default:

        av_log(avctx, AV_LOG_ERROR, "Unknown type: %X\n", type);

        return AVERROR_INVALIDDATA;

    }

    memcpy(frame->data[1], s->pal, AVPALETTE_SIZE);

    frame->pict_type = AV_PICTURE_TYPE_I;

    frame->flags |= AV_FRAME_FLAG_KEY;

    *got_frame = 1;

    return avpkt->size;

}

static av_cold int sga_decode_end(AVCodecContext *avctx)

{

    SGAVideoContext *s = avctx->priv_data;

    av_freep(&s->tileindex_data);

    s->tileindex_size = 0;

    av_freep(&s->palmapindex_data);

    s->palmapindex_size = 0;

    return 0;

}

const FFCodec ff_sga_decoder = {

    .p.name         = "sga",

    CODEC_LONG_NAME("Digital Pictures SGA Video"),

    .p.type         = AVMEDIA_TYPE_VIDEO,

    .p.id           = AV_CODEC_ID_SGA_VIDEO,

    .priv_data_size = sizeof(SGAVideoContext),

    .init           = sga_decode_init,

    FF_CODEC_DECODE_CB(sga_decode_frame),

    .close          = sga_decode_end,

    .p.capabilities = AV_CODEC_CAP_DR1,

};