/*
  * Discworld II BMV video and audio decoder
  * Copyright (c) 2011 Konstantin Shishkov
  *
  * This file is part of Libav.
  *
  * Libav 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.
  *
  * Libav 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 Libav; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 

 #include "libavutil/avassert.h"

 #include "libavutil/channel_layout.h"

 #include "avcodec.h"
 #include "bytestream.h"

 #include "internal.h"

 
 enum BMVFlags{
     BMV_NOP = 0,
     BMV_END,
     BMV_DELTA,
     BMV_INTRA,
 
     BMV_SCROLL  = 0x04,
     BMV_PALETTE = 0x08,
     BMV_COMMAND = 0x10,
     BMV_AUDIO   = 0x20,
     BMV_EXT     = 0x40,
     BMV_PRINT   = 0x80
 };
 
 #define SCREEN_WIDE 640
 #define SCREEN_HIGH 429
 
 typedef struct BMVDecContext {
     AVCodecContext *avctx;
     AVFrame pic;
 
     uint8_t *frame, frame_base[SCREEN_WIDE * (SCREEN_HIGH + 1)];
     uint32_t pal[256];
     const uint8_t *stream;
 } BMVDecContext;
 
 #define NEXT_BYTE(v) v = forward ? v + 1 : v - 1;
 
 static int decode_bmv_frame(const uint8_t *source, int src_len, uint8_t *frame, int frame_off)
 {

     unsigned val, saved_val = 0;

     int tmplen = src_len;
     const uint8_t *src, *source_end = source + src_len;
     uint8_t *frame_end = frame + SCREEN_WIDE * SCREEN_HIGH;
     uint8_t *dst, *dst_end;
     int len, mask;
     int forward = (frame_off <= -SCREEN_WIDE) || (frame_off >= 0);
     int read_two_nibbles, flag;
     int advance_mode;
     int mode = 0;
     int i;
 
     if (src_len <= 0)
         return -1;
 
     if (forward) {
         src = source;
         dst = frame;
         dst_end = frame_end;
     } else {
         src = source + src_len - 1;
         dst = frame_end - 1;
         dst_end = frame - 1;
     }
     for (;;) {
         int shift = 0;
         flag = 0;
 
         /* The mode/len decoding is a bit strange:
          * values are coded as variable-length codes with nibble units,
          * code end is signalled by two top bits in the nibble being nonzero.
          * And since data is bytepacked and we read two nibbles at a time,
          * we may get a nibble belonging to the next code.
          * Hence this convoluted loop.
          */
         if (!mode || (tmplen == 4)) {
             if (src < source || src >= source_end)
                 return -1;
             val = *src;
             read_two_nibbles = 1;
         } else {
             val = saved_val;
             read_two_nibbles = 0;
         }
         if (!(val & 0xC)) {
             for (;;) {

                 if(shift>22)
                     return -1;

                 if (!read_two_nibbles) {
                     if (src < source || src >= source_end)
                         return -1;
                     shift += 2;
                     val |= *src << shift;
                     if (*src & 0xC)
                         break;
                 }
                 // two upper bits of the nibble is zero,
                 // so shift top nibble value down into their place
                 read_two_nibbles = 0;
                 shift += 2;
                 mask = (1 << shift) - 1;
                 val = ((val >> 2) & ~mask) | (val & mask);
                 NEXT_BYTE(src);
                 if ((val & (0xC << shift))) {
                     flag = 1;
                     break;
                 }
             }
         } else if (mode) {
             flag = tmplen != 4;
         }
         if (flag) {
             tmplen = 4;
         } else {
             saved_val = val >> (4 + shift);
             tmplen = 0;
             val &= (1 << (shift + 4)) - 1;
             NEXT_BYTE(src);
         }
         advance_mode = val & 1;
         len = (val >> 1) - 1;

         av_assert0(len>0);

         mode += 1 + advance_mode;
         if (mode >= 4)
             mode -= 3;

         if (len <= 0 || FFABS(dst_end - dst) < len)

             return -1;
         switch (mode) {
         case 1:
             if (forward) {
                 if (dst - frame + SCREEN_WIDE < frame_off ||

                         dst - frame + SCREEN_WIDE + frame_off < 0 ||
                         frame_end - dst < frame_off + len ||
                         frame_end - dst < len)

                     return -1;
                 for (i = 0; i < len; i++)
                     dst[i] = dst[frame_off + i];
                 dst += len;
             } else {
                 dst -= len;
                 if (dst - frame + SCREEN_WIDE < frame_off ||

                         dst - frame + SCREEN_WIDE + frame_off < 0 ||
                         frame_end - dst < frame_off + len ||
                         frame_end - dst < len)

                     return -1;
                 for (i = len - 1; i >= 0; i--)
                     dst[i] = dst[frame_off + i];
             }
             break;
         case 2:
             if (forward) {
                 if (source + src_len - src < len)
                     return -1;
                 memcpy(dst, src, len);
                 dst += len;
                 src += len;
             } else {
                 if (src - source < len)
                     return -1;
                 dst -= len;
                 src -= len;
                 memcpy(dst, src, len);
             }
             break;
         case 3:
             val = forward ? dst[-1] : dst[1];
             if (forward) {
                 memset(dst, val, len);
                 dst += len;
             } else {
                 dst -= len;
                 memset(dst, val, len);
             }
             break;
         }
         if (dst == dst_end)
             return 0;
     }
     return 0;
 }
 

 static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
                         AVPacket *pkt)

 {
     BMVDecContext * const c = avctx->priv_data;
     int type, scr_off;

     int i, ret;

     uint8_t *srcptr, *outptr;
 
     c->stream = pkt->data;
     type = bytestream_get_byte(&c->stream);
     if (type & BMV_AUDIO) {
         int blobs = bytestream_get_byte(&c->stream);
         if (pkt->size < blobs * 65 + 2) {
             av_log(avctx, AV_LOG_ERROR, "Audio data doesn't fit in frame\n");
             return AVERROR_INVALIDDATA;
         }
         c->stream += blobs * 65;
     }
     if (type & BMV_COMMAND) {
         int command_size = (type & BMV_PRINT) ? 8 : 10;
         if (c->stream - pkt->data + command_size > pkt->size) {
             av_log(avctx, AV_LOG_ERROR, "Command data doesn't fit in frame\n");
             return AVERROR_INVALIDDATA;
         }
         c->stream += command_size;
     }
     if (type & BMV_PALETTE) {
         if (c->stream - pkt->data > pkt->size - 768) {
             av_log(avctx, AV_LOG_ERROR, "Palette data doesn't fit in frame\n");
             return AVERROR_INVALIDDATA;
         }
         for (i = 0; i < 256; i++)

             c->pal[i] = 0xFFU << 24 | bytestream_get_be24(&c->stream);

     }
     if (type & BMV_SCROLL) {
         if (c->stream - pkt->data > pkt->size - 2) {
             av_log(avctx, AV_LOG_ERROR, "Screen offset data doesn't fit in frame\n");
             return AVERROR_INVALIDDATA;
         }
         scr_off = (int16_t)bytestream_get_le16(&c->stream);
     } else if ((type & BMV_INTRA) == BMV_INTRA) {
         scr_off = -640;
     } else {
         scr_off = 0;
     }
 

     if (c->pic.data[0])
         avctx->release_buffer(avctx, &c->pic);
 
     c->pic.reference = 3;

     if ((ret = ff_get_buffer(avctx, &c->pic)) < 0) {

         av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
         return ret;
     }
 

     if (decode_bmv_frame(c->stream, pkt->size - (c->stream - pkt->data), c->frame, scr_off)) {
         av_log(avctx, AV_LOG_ERROR, "Error decoding frame data\n");
         return AVERROR_INVALIDDATA;
     }
 
     memcpy(c->pic.data[1], c->pal, AVPALETTE_SIZE);
     c->pic.palette_has_changed = type & BMV_PALETTE;
 
     outptr = c->pic.data[0];
     srcptr = c->frame;
 
     for (i = 0; i < avctx->height; i++) {
         memcpy(outptr, srcptr, avctx->width);
         srcptr += avctx->width;
         outptr += c->pic.linesize[0];
     }
 

     *got_frame = 1;

     *(AVFrame*)data = c->pic;
 
     /* always report that the buffer was completely consumed */
     return pkt->size;
 }
 
 static av_cold int decode_init(AVCodecContext *avctx)
 {
     BMVDecContext * const c = avctx->priv_data;
 
     c->avctx = avctx;

     avctx->pix_fmt = AV_PIX_FMT_PAL8;

     if (avctx->width != SCREEN_WIDE || avctx->height != SCREEN_HIGH) {
         av_log(avctx, AV_LOG_ERROR, "Invalid dimension %dx%d\n", avctx->width, avctx->height);
         return AVERROR_INVALIDDATA;
     }
 

     c->frame = c->frame_base + 640;
 
     return 0;
 }
 
 static av_cold int decode_end(AVCodecContext *avctx)
 {
     BMVDecContext *c = avctx->priv_data;
 
     if (c->pic.data[0])
         avctx->release_buffer(avctx, &c->pic);
 
     return 0;
 }
 

 typedef struct BMVAudioDecContext {
     AVFrame frame;
 } BMVAudioDecContext;
 

 static const int bmv_aud_mults[16] = {
     16512, 8256, 4128, 2064, 1032, 516, 258, 192, 129, 88, 64, 56, 48, 40, 36, 32
 };
 
 static av_cold int bmv_aud_decode_init(AVCodecContext *avctx)
 {

     BMVAudioDecContext *c = avctx->priv_data;

     avctx->channels       = 2;
     avctx->channel_layout = AV_CH_LAYOUT_STEREO;
     avctx->sample_fmt     = AV_SAMPLE_FMT_S16;

     avcodec_get_frame_defaults(&c->frame);
     avctx->coded_frame = &c->frame;
 

     return 0;
 }
 

 static int bmv_aud_decode_frame(AVCodecContext *avctx, void *data,
                                 int *got_frame_ptr, AVPacket *avpkt)

 {

     BMVAudioDecContext *c = avctx->priv_data;

     const uint8_t *buf = avpkt->data;
     int buf_size = avpkt->size;
     int blocks = 0, total_blocks, i;

     int ret;
     int16_t *output_samples;

     int scale[2];
 
     total_blocks = *buf++;
     if (buf_size < total_blocks * 65 + 1) {
         av_log(avctx, AV_LOG_ERROR, "expected %d bytes, got %d\n",
                total_blocks * 65 + 1, buf_size);
         return AVERROR_INVALIDDATA;
     }

 
     /* get output buffer */
     c->frame.nb_samples = total_blocks * 32;

     if ((ret = ff_get_buffer(avctx, &c->frame)) < 0) {

         av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
         return ret;

     }

     output_samples = (int16_t *)c->frame.data[0];

 
     for (blocks = 0; blocks < total_blocks; blocks++) {
         uint8_t code = *buf++;
         code = (code >> 1) | (code << 7);
         scale[0] = bmv_aud_mults[code & 0xF];
         scale[1] = bmv_aud_mults[code >> 4];
         for (i = 0; i < 32; i++) {
             *output_samples++ = av_clip_int16((scale[0] * (int8_t)*buf++) >> 5);
             *output_samples++ = av_clip_int16((scale[1] * (int8_t)*buf++) >> 5);
         }
     }
 

     *got_frame_ptr   = 1;
     *(AVFrame *)data = c->frame;
 

     return buf_size;
 }
 
 AVCodec ff_bmv_video_decoder = {
     .name           = "bmv_video",
     .type           = AVMEDIA_TYPE_VIDEO,

     .id             = AV_CODEC_ID_BMV_VIDEO,

     .priv_data_size = sizeof(BMVDecContext),
     .init           = decode_init,
     .close          = decode_end,
     .decode         = decode_frame,

     .capabilities   = CODEC_CAP_DR1,

     .long_name      = NULL_IF_CONFIG_SMALL("Discworld II BMV video"),
 };
 
 AVCodec ff_bmv_audio_decoder = {
     .name           = "bmv_audio",
     .type           = AVMEDIA_TYPE_AUDIO,

     .id             = AV_CODEC_ID_BMV_AUDIO,

     .priv_data_size = sizeof(BMVAudioDecContext),

     .init           = bmv_aud_decode_init,
     .decode         = bmv_aud_decode_frame,

     .capabilities   = CODEC_CAP_DR1,

     .long_name      = NULL_IF_CONFIG_SMALL("Discworld II BMV audio"),
 };