/*
  * Gremlin Digital Video (GDV) decoder
  * Copyright (c) 2017 Konstantin Shishkov
  * Copyright (c) 2017 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 "avcodec.h"
 #include "bytestream.h"
 #include "internal.h"
 
 typedef struct GDVContext {
     AVCodecContext *avctx;
 
     GetByteContext gb;
     GetByteContext g2;
     PutByteContext pb;
 
     uint32_t pal[256];
     uint8_t *frame;
     unsigned frame_size;
     unsigned scale_h, scale_v;
 } GDVContext;
 

 typedef struct Bits8 {
     uint8_t queue;
     uint8_t fill;
 } Bits8;
 

 typedef struct Bits32 {
     uint32_t queue;
     uint8_t  fill;
 } Bits32;
 
 #define PREAMBLE_SIZE 4096
 
 static av_cold int gdv_decode_init(AVCodecContext *avctx)
 {
     GDVContext *gdv = avctx->priv_data;
     int i, j, k;
 
     avctx->pix_fmt  = AV_PIX_FMT_PAL8;
     gdv->frame_size = avctx->width * avctx->height + PREAMBLE_SIZE;
     gdv->frame = av_calloc(gdv->frame_size, 1);
     if (!gdv->frame)
         return AVERROR(ENOMEM);
 
     for (i = 0; i < 2; i++) {
         for (j = 0; j < 256; j++) {
             for (k = 0; k < 8; k++) {
                 gdv->frame[i * 2048 + j * 8 + k] = j;
             }
         }
     }
 
     return 0;
 }
 
 static void rescale(GDVContext *gdv, uint8_t *dst, int w, int h, int scale_v, int scale_h)
 {
     int i, j, y, x;
 
     if ((gdv->scale_v == scale_v) && (gdv->scale_h == scale_h)) {
         return;
     }
 
     if (gdv->scale_h && gdv->scale_v) {
         for (j = 0; j < h; j++) {
             int y = h - j - 1;
             for (i = 0; i < w; i++) {
                 int x = w - i - 1;

                 dst[PREAMBLE_SIZE + x + y * w] = dst[PREAMBLE_SIZE + (x>>1) + (y>>1) * (w>>1)];

             }
         }
     } else if (gdv->scale_h) {
         for (j = 0; j < h; j++) {
             int y = h - j - 1;
             for (x = 0; x < w; x++) {

                 dst[PREAMBLE_SIZE + x + y * w] = dst[PREAMBLE_SIZE + x + (y>>1) * w];

             }
         }
     } else if (gdv->scale_v) {
         for (j = 0; j < h; j++) {
             int y = h - j - 1;
             for (i = 0; i < w; i++) {
                 int x = w - i - 1;

                 dst[PREAMBLE_SIZE + x + y * w] = dst[PREAMBLE_SIZE + (x>>1) + y * (w>>1)];

             }
         }
     }
 
     if (scale_h && scale_v) {

         for (y = 0; y < (h>>1); y++) {
             for (x = 0; x < (w>>1); x++) {
                 dst[PREAMBLE_SIZE + x + y * (w>>1)] = dst[PREAMBLE_SIZE + x*2 + y*2 * w];

             }
         }
     } else if (scale_h) {

         for (y = 0; y < (h>>1); y++) {

             for (x = 0; x < w; x++) {
                 dst[PREAMBLE_SIZE + x + y * w] = dst[PREAMBLE_SIZE + x + y*2 * w];
             }
         }
     } else if (scale_v) {
         for (y = 0; y < h; y++) {

             for (x = 0; x < (w>>1); x++) {

                 dst[PREAMBLE_SIZE + x + y * w] = dst[PREAMBLE_SIZE + x*2 + y * w];
             }
         }
     }
 
     gdv->scale_v = scale_v;
     gdv->scale_h = scale_h;
 }
 

 static int read_bits2(Bits8 *bits, GetByteContext *gb)
 {
     int res;
 
     if (bits->fill == 0) {
         bits->queue |= bytestream2_get_byte(gb);
         bits->fill   = 8;
     }
     res = bits->queue >> 6;
     bits->queue <<= 2;
     bits->fill   -= 2;
 
     return res;
 }
 

 static void fill_bits32(Bits32 *bits, GetByteContext *gb)
 {
     bits->queue = bytestream2_get_le32(gb);
     bits->fill  = 32;
 }
 
 static int read_bits32(Bits32 *bits, GetByteContext *gb, int nbits)
 {
     int res = bits->queue & ((1 << nbits) - 1);
 
     bits->queue >>= nbits;
     bits->fill   -= nbits;
     if (bits->fill <= 16) {
         bits->queue |= bytestream2_get_le16(gb) << bits->fill;
         bits->fill  += 16;
     }
 
     return res;
 }
 
 static void lz_copy(PutByteContext *pb, GetByteContext *g2, int offset, unsigned len)
 {
     int i;
 
     if (offset == -1) {
         int c;
 
         bytestream2_seek(g2, bytestream2_tell_p(pb) - 1, SEEK_SET);
         c = bytestream2_get_byte(g2);
         for (i = 0; i < len; i++) {
             bytestream2_put_byte(pb, c);
         }
     } else if (offset < 0) {
         int start = bytestream2_tell_p(pb) - (-offset);
 
         bytestream2_seek(g2, start, SEEK_SET);
         for (i = 0; i < len; i++) {
             bytestream2_put_byte(pb, bytestream2_get_byte(g2));
         }
     } else {
         int start = bytestream2_tell_p(pb) + offset;
 
         bytestream2_seek(g2, start, SEEK_SET);
         for (i = 0; i < len; i++) {
             bytestream2_put_byte(pb, bytestream2_get_byte(g2));
         }
     }
 }
 

 static int decompress_2(AVCodecContext *avctx)
 {
     GDVContext *gdv = avctx->priv_data;
     GetByteContext *gb = &gdv->gb;
     GetByteContext *g2 = &gdv->g2;
     PutByteContext *pb = &gdv->pb;
     Bits8 bits = { 0 };
     int c, i;
 
     bytestream2_init(g2, gdv->frame, gdv->frame_size);
     bytestream2_skip_p(pb, PREAMBLE_SIZE);
 
     for (c = 0; c < 256; c++) {
         for (i = 0; i < 16; i++) {
             gdv->frame[c * 16 + i] = c;
         }
     }
 
     while (bytestream2_get_bytes_left_p(pb) > 0 && bytestream2_get_bytes_left(gb) > 0) {
         int tag = read_bits2(&bits, gb);
         if (tag == 0) {
             bytestream2_put_byte(pb, bytestream2_get_byte(gb));
         } else if (tag == 1) {
             int b = bytestream2_get_byte(gb);
             int len = (b & 0xF) + 3;
             int top = (b >> 4) & 0xF;
             int off = (bytestream2_get_byte(gb) << 4) + top - 4096;
             lz_copy(pb, g2, off, len);
         } else if (tag == 2) {
             int len = (bytestream2_get_byte(gb)) + 2;
             bytestream2_skip_p(pb, len);
         } else {
             break;
         }
     }
     return 0;
 }
 
 static int decompress_5(AVCodecContext *avctx, unsigned skip)
 {
     GDVContext *gdv = avctx->priv_data;
     GetByteContext *gb = &gdv->gb;
     GetByteContext *g2 = &gdv->g2;
     PutByteContext *pb = &gdv->pb;
     Bits8 bits = { 0 };
 
     bytestream2_init(g2, gdv->frame, gdv->frame_size);
     bytestream2_skip_p(pb, skip + PREAMBLE_SIZE);
 
     while (bytestream2_get_bytes_left_p(pb) > 0 && bytestream2_get_bytes_left(gb) > 0) {
         int tag = read_bits2(&bits, gb);

         if (bytestream2_get_bytes_left(gb) < 1)
             return AVERROR_INVALIDDATA;

         if (tag == 0) {
             bytestream2_put_byte(pb, bytestream2_get_byte(gb));
         } else if (tag == 1) {
             int b = bytestream2_get_byte(gb);
             int len = (b & 0xF) + 3;
             int top = b >> 4;
             int off = (bytestream2_get_byte(gb) << 4) + top - 4096;
             lz_copy(pb, g2, off, len);
         } else if (tag == 2) {
             int len;
             int b = bytestream2_get_byte(gb);
             if (b == 0) {
                 break;
             }
             if (b != 0xFF) {
                 len = b;
             } else {
                 len = bytestream2_get_le16(gb);
             }
             bytestream2_skip_p(pb, len + 1);
         } else {
             int b = bytestream2_get_byte(gb);
             int len = (b & 0x3) + 2;
             int off = -(b >> 2) - 1;
             lz_copy(pb, g2, off, len);
         }
     }
     return 0;
 }
 

 static int decompress_68(AVCodecContext *avctx, unsigned skip, unsigned use8)
 {
     GDVContext *gdv = avctx->priv_data;
     GetByteContext *gb = &gdv->gb;
     GetByteContext *g2 = &gdv->g2;
     PutByteContext *pb = &gdv->pb;
     Bits32 bits;
 
     bytestream2_init(g2, gdv->frame, gdv->frame_size);
     bytestream2_skip_p(pb, skip + PREAMBLE_SIZE);
     fill_bits32(&bits, gb);
 
     while (bytestream2_get_bytes_left_p(pb) > 0 && bytestream2_get_bytes_left(gb) > 0) {
         int tag = read_bits32(&bits, gb, 2);
         if (tag == 0) {
             int b = read_bits32(&bits, gb, 1);
             if (b == 0) {
                 bytestream2_put_byte(pb, bytestream2_get_byte(gb));
             } else {
                 int i, len = 2;
                 int lbits = 0;
                 while (1) {
                     int val;
 
                     lbits += 1;
                     val = read_bits32(&bits, gb, lbits);
                     len += val;
                     if (val != ((1 << lbits) - 1)) {
                         break;
                     }

                     if (lbits >= 16)
                         return AVERROR_INVALIDDATA;

                 }
                 for (i = 0; i < len; i++) {
                     bytestream2_put_byte(pb, bytestream2_get_byte(gb));
                 }
             }
         } else if (tag == 1) {
             int b = read_bits32(&bits, gb, 1);
             int len;
 
             if (b == 0) {
                 len = (read_bits32(&bits, gb, 4)) + 2;
             } else {
                 int bb = bytestream2_get_byte(gb);
                 if ((bb & 0x80) == 0) {
                     len = bb + 18;
                 } else {
                     int top = (bb & 0x7F) << 8;
                     len = top + bytestream2_get_byte(gb) + 146;
                 }
             }
             bytestream2_skip_p(pb, len);
         } else if (tag == 2) {
             int i, subtag = read_bits32(&bits, gb, 2);
 
             if (subtag != 3) {
                 int top = (read_bits32(&bits, gb, 4)) << 8;
                 int offs = top + bytestream2_get_byte(gb);
                 if ((subtag != 0) || (offs <= 0xF80)) {
                     int len = (subtag) + 3;
                     lz_copy(pb, g2, (offs) - 4096, len);
                 } else {

                     int real_off, len, c1, c2;
 

                     if (offs == 0xFFF) {
                         return 0;
                     }
 

                     real_off = ((offs >> 4) & 0x7) + 1;
                     len = ((offs & 0xF) + 2) * 2;
                     c1 = gdv->frame[bytestream2_tell_p(pb) - real_off];
                     c2 = gdv->frame[bytestream2_tell_p(pb) - real_off + 1];

                     for (i = 0; i < len/2; i++) {
                         bytestream2_put_byte(pb, c1);
                         bytestream2_put_byte(pb, c2);
                     }
                 }
             } else {
                 int b = bytestream2_get_byte(gb);
                 int off = ((b & 0x7F)) + 1;
                 int len = ((b & 0x80) == 0) ? 2 : 3;
 
                 lz_copy(pb, g2, -off, len);
             }
         } else {
             int len;
             int off;
             if (use8) {

                 int q, b = bytestream2_get_byte(gb);

                 if ((b & 0xC0) == 0xC0) {
                     len = ((b & 0x3F)) + 8;

                     q = read_bits32(&bits, gb, 4);

                     off = (q << 8) + (bytestream2_get_byte(gb)) + 1;
                 } else {
                     int ofs1;
                     if ((b & 0x80) == 0) {
                         len = ((b >> 4)) + 6;
                         ofs1 = (b & 0xF);
                     } else {
                         len = ((b & 0x3F)) + 14;
                         ofs1 = read_bits32(&bits, gb, 4);
                     }
                     off = (ofs1 << 8) + (bytestream2_get_byte(gb)) - 4096;
                 }
             } else {

                 int ofs1, b = bytestream2_get_byte(gb);

 
                 if ((b >> 4) == 0xF) {
                     len = bytestream2_get_byte(gb) + 21;
                 } else {
                     len = (b >> 4) + 6;
                 }

                 ofs1 = (b & 0xF);

                 off = (ofs1 << 8) + bytestream2_get_byte(gb) - 4096;
             }
             lz_copy(pb, g2, off, len);
         }
     }
 
     return 0;
 }
 
 static int gdv_decode_frame(AVCodecContext *avctx, void *data,
                             int *got_frame, AVPacket *avpkt)
 {
     GDVContext *gdv = avctx->priv_data;
     GetByteContext *gb = &gdv->gb;
     PutByteContext *pb = &gdv->pb;
     AVFrame *frame = data;
     int ret, i, pal_size;
     const uint8_t *pal = av_packet_get_side_data(avpkt, AV_PKT_DATA_PALETTE, &pal_size);
     int compression;
     unsigned flags;
     uint8_t *dst;
 
     if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
         return ret;
     if (pal && pal_size == AVPALETTE_SIZE)
         memcpy(gdv->pal, pal, AVPALETTE_SIZE);
 
     bytestream2_init(gb, avpkt->data, avpkt->size);
     bytestream2_init_writer(pb, gdv->frame, gdv->frame_size);
 
     flags = bytestream2_get_le32(gb);
     compression = flags & 0xF;
 
     rescale(gdv, gdv->frame, avctx->width, avctx->height,
             !!(flags & 0x10), !!(flags & 0x20));
 
     switch (compression) {
     case 1:
         memset(gdv->frame + PREAMBLE_SIZE, 0, gdv->frame_size - PREAMBLE_SIZE);
     case 0:

         if (bytestream2_get_bytes_left(gb) < 256*3)
             return AVERROR_INVALIDDATA;

         for (i = 0; i < 256; i++) {
             unsigned r = bytestream2_get_byte(gb);
             unsigned g = bytestream2_get_byte(gb);
             unsigned b = bytestream2_get_byte(gb);

             gdv->pal[i] = 0xFFU << 24 | r << 18 | g << 10 | b << 2;

         }
         break;

     case 2:
         ret = decompress_2(avctx);
         break;

     case 3:
         break;

     case 5:
         ret = decompress_5(avctx, flags >> 8);
         break;

     case 6:
         ret = decompress_68(avctx, flags >> 8, 0);
         break;
     case 8:
         ret = decompress_68(avctx, flags >> 8, 1);
         break;
     default:
         return AVERROR_INVALIDDATA;
     }
 
     memcpy(frame->data[1], gdv->pal, AVPALETTE_SIZE);
     dst = frame->data[0];
 
     if (!gdv->scale_v && !gdv->scale_h) {
         int sidx = PREAMBLE_SIZE, didx = 0;
         int y, x;
 
         for (y = 0; y < avctx->height; y++) {
             for (x = 0; x < avctx->width; x++) {
                 dst[x+didx] = gdv->frame[x+sidx];
             }
             sidx += avctx->width;
             didx += frame->linesize[0];
         }
     } else {
         int sidx = PREAMBLE_SIZE, didx = 0;
         int y, x;
 
         for (y = 0; y < avctx->height; y++) {
             if (!gdv->scale_v) {
                 for (x = 0; x < avctx->width; x++) {
                     dst[didx + x] = gdv->frame[sidx + x];
                 }
             } else {
                 for (x = 0; x < avctx->width; x++) {
                     dst[didx + x] = gdv->frame[sidx + x/2];
                 }
             }
             if (!gdv->scale_h || ((y & 1) == 1)) {
                 sidx += !gdv->scale_v ? avctx->width : avctx->width/2;
             }
             didx += frame->linesize[0];
         }
     }
 
     *got_frame = 1;
 
     return ret < 0 ? ret : avpkt->size;
 }
 
 static av_cold int gdv_decode_close(AVCodecContext *avctx)
 {
     GDVContext *gdv = avctx->priv_data;
     av_freep(&gdv->frame);
     return 0;
 }
 
 AVCodec ff_gdv_decoder = {
     .name           = "gdv",
     .long_name      = NULL_IF_CONFIG_SMALL("Gremlin Digital Video"),
     .type           = AVMEDIA_TYPE_VIDEO,
     .id             = AV_CODEC_ID_GDV,
     .priv_data_size = sizeof(GDVContext),
     .init           = gdv_decode_init,
     .close          = gdv_decode_close,
     .decode         = gdv_decode_frame,
     .capabilities   = AV_CODEC_CAP_DR1,
     .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE,
 };