/*
  * Kega Game Video (KGV1) decoder
  * Copyright (c) 2010 Daniel Verkamp
  *
  * 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

  * Kega Game Video decoder
  */
 
 #include "libavutil/intreadwrite.h"

 #include "libavutil/imgutils.h"

 #include "avcodec.h"
 
 typedef struct {
     AVCodecContext *avctx;

     AVFrame prev, cur;

 } KgvContext;
 

 static void decode_flush(AVCodecContext *avctx)
 {
     KgvContext * const c = avctx->priv_data;
 
     if (c->prev.data[0])
         avctx->release_buffer(avctx, &c->prev);
 }
 

 static int decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPacket *avpkt)
 {
     const uint8_t *buf = avpkt->data;
     const uint8_t *buf_end = buf + avpkt->size;
     KgvContext * const c = avctx->priv_data;

     int offsets[8];

     uint16_t *out, *prev;
     int outcnt = 0, maxcnt;

     int w, h, i, res;

 
     if (avpkt->size < 2)
         return -1;
 
     w = (buf[0] + 1) * 8;
     h = (buf[1] + 1) * 8;
     buf += 2;
 

     if (av_image_check_size(w, h, 0, avctx))

         return -1;
 

     if (w != avctx->width || h != avctx->height) {
         if (c->prev.data[0])
             avctx->release_buffer(avctx, &c->prev);

         avcodec_set_dimensions(avctx, w, h);

     }

 
     maxcnt = w * h;
 

     c->cur.reference = 3;
     if ((res = avctx->get_buffer(avctx, &c->cur)) < 0)
         return res;
     out  = (uint16_t *) c->cur.data[0];
     if (c->prev.data[0]) {
         prev = (uint16_t *) c->prev.data[0];
     } else {
         prev = NULL;
     }

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

         offsets[i] = -1;
 
     while (outcnt < maxcnt && buf_end - 2 > buf) {
         int code = AV_RL16(buf);
         buf += 2;
 
         if (!(code & 0x8000)) {
             out[outcnt++] = code; // rgb555 pixel coded directly
         } else {
             int count;

             int inp_off;

             uint16_t *inp;
 
             if ((code & 0x6000) == 0x6000) {
                 // copy from previous frame
                 int oidx = (code >> 10) & 7;
                 int start;
 
                 count = (code & 0x3FF) + 3;
 
                 if (offsets[oidx] < 0) {
                     if (buf_end - 3 < buf)
                         break;
                     offsets[oidx] = AV_RL24(buf);
                     buf += 3;
                 }
 
                 start = (outcnt + offsets[oidx]) % maxcnt;
 
                 if (maxcnt - start < count)
                     break;
 

                 if (!prev) {
                     av_log(avctx, AV_LOG_ERROR,
                            "Frame reference does not exist\n");
                     break;
                 }
 
                 inp = prev;
                 inp_off = start;

             } else {
                 // copy from earlier in this frame
                 int offset = (code & 0x1FFF) + 1;
 
                 if (!(code & 0x6000)) {
                     count = 2;
                 } else if ((code & 0x6000) == 0x2000) {
                     count = 3;
                 } else {
                     if (buf_end - 1 < buf)
                         break;
                     count = 4 + *buf++;
                 }
 
                 if (outcnt < offset)
                     break;
 

                 inp = out;
                 inp_off = outcnt - offset;

             }
 
             if (maxcnt - outcnt < count)
                 break;
 

             for (i = inp_off; i < count + inp_off; i++) {

                 out[outcnt++] = inp[i];

             }

         }
     }
 
     if (outcnt - maxcnt)
         av_log(avctx, AV_LOG_DEBUG, "frame finished with %d diff\n", outcnt - maxcnt);
 
     *data_size = sizeof(AVFrame);

     *(AVFrame*)data = c->cur;

     if (c->prev.data[0])
         avctx->release_buffer(avctx, &c->prev);
     FFSWAP(AVFrame, c->cur, c->prev);

 
     return avpkt->size;
 }
 
 static av_cold int decode_init(AVCodecContext *avctx)
 {
     KgvContext * const c = avctx->priv_data;
 
     c->avctx = avctx;
     avctx->pix_fmt = PIX_FMT_RGB555;

     avctx->flags  |= CODEC_FLAG_EMU_EDGE;

 
     return 0;
 }
 
 static av_cold int decode_end(AVCodecContext *avctx)
 {

     decode_flush(avctx);

     return 0;
 }
 

 AVCodec ff_kgv1_decoder = {

     .name           = "kgv1",
     .type           = AVMEDIA_TYPE_VIDEO,
     .id             = CODEC_ID_KGV1,
     .priv_data_size = sizeof(KgvContext),
     .init           = decode_init,
     .close          = decode_end,
     .decode         = decode_frame,

     .flush          = decode_flush,

     .long_name      = NULL_IF_CONFIG_SMALL("Kega Game Video"),

 };