/*
 * VBLE Decoder
 * Copyright (c) 2011 Derek Buitenhuis
 *
 * 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
 * VBLE Decoder
 */

#define ALT_BITSTREAM_READER_LE

#include "avcodec.h"
#include "get_bits.h"

typedef struct {
    AVCodecContext *avctx;

    int            size;
    uint8_t        *val; ///< This array first holds the lengths of vlc symbols and then their value.
} VBLEContext;

static int vble_unpack(VBLEContext *ctx, GetBitContext *gb)
{
    int i;
    int allbits = 0;
    static const uint8_t LUT[256] = {
        8,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
        5,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
        6,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
        5,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
        7,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
        5,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
        6,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
        5,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
    };

    /* Read all the lengths in first */
    for (i = 0; i < ctx->size; i++) {
        /* At most we need to read 9 bits total to get indices up to 8 */
        int val = show_bits(gb, 8);

        // read reverse unary
        if (val) {
            val = LUT[val];
            skip_bits(gb, val + 1);
            ctx->val[i] = val;
        } else {
            skip_bits(gb, 8);
            if (!get_bits1(gb))
                return -1;
            ctx->val[i] = 8;
        }
        allbits += ctx->val[i];
    }

    /* Check we have enough bits left */
    if (get_bits_left(gb) < allbits)
        return -1;

    for (i = 0; i < ctx->size; i++) {
        /* get_bits can't take a length of 0 */
        if (ctx->val[i])
            ctx->val[i] = (1 << ctx->val[i]) + get_bits(gb, ctx->val[i]) - 1;
    }

    return 0;
}

static void vble_restore_plane(VBLEContext *ctx, int plane, int offset,
                              int width, int height)
{
    AVFrame *pic = ctx->avctx->coded_frame;
    uint8_t *dst = pic->data[plane];
    uint8_t *val = ctx->val + offset;
    uint8_t a, b, c;
    int stride = pic->linesize[plane];
    int i, j;

    for (i = 0; i < height; i++) {
        for (j = 0; j < width; j++) {
            dst[j] = (val[j] >> 1) ^ -(val[j] & 1);

            /* Top line and left column are not predicted */
            if (!j)
                continue;

            if (!i) {
                dst[j] += dst[j - 1];
                continue;
            }

            a = dst[j - 1];
            b = dst[j - stride];
            c = a + b - dst[j - 1 - stride];
            dst[j] += mid_pred(a, b, c);
        }
        dst += stride;
        val += width;
    }
}

static int vble_decode_frame(AVCodecContext *avctx, void *data, int *data_size,
                             AVPacket *avpkt)
{
    VBLEContext *ctx = avctx->priv_data;
    AVFrame *pic = avctx->coded_frame;
    GetBitContext gb;
    const uint8_t *src = avpkt->data;
    int version;
    int offset = 0;
    int width_uv = avctx->width / 2, height_uv = avctx->height / 2;

    pic->reference = 0;

    /* Clear buffer if need be */
    if (pic->data[0])
        avctx->release_buffer(avctx, pic);

    /* Allocate buffer */
    if (avctx->get_buffer(avctx, pic) < 0) {
        av_log(avctx, AV_LOG_ERROR, "Could not allocate buffer.\n");
        return AVERROR(ENOMEM);
    }

    /* Set flags */
    pic->key_frame = 1;
    pic->pict_type = FF_I_TYPE;

    /* Version should always be 1 */
    version = AV_RL32(src);

    if (version != 1) {
        av_log(avctx, AV_LOG_ERROR, "Unsupported VBLE Version: %d\n", version);
        return AVERROR_INVALIDDATA;
    }

    init_get_bits(&gb, src + 4, (avpkt->size - 4) * 8);

    /* Unpack */
    if (vble_unpack(ctx, &gb) < 0) {
        av_log(avctx, AV_LOG_ERROR, "Invalid Code\n");
        return AVERROR_INVALIDDATA;
    }

    /* Restore planes. Should be almost identical to Huffyuv's. */
    vble_restore_plane(ctx, 0, offset, avctx->width, avctx->height);

    /* Chroma */
    if (!(ctx->avctx->flags & CODEC_FLAG_GRAY)) {
        offset += avctx->width * avctx->height;
        vble_restore_plane(ctx, 1, offset, width_uv, height_uv);

        offset += width_uv * height_uv;
        vble_restore_plane(ctx, 2, offset, width_uv, height_uv);
    }

    *data_size = sizeof(AVFrame);
    *(AVFrame *)data = *pic;

    return avpkt->size;
}

static av_cold int vble_decode_close(AVCodecContext *avctx)
{
    VBLEContext *ctx = avctx->priv_data;
    AVFrame *pic = avctx->coded_frame;

    if (pic->data[0])
        avctx->release_buffer(avctx, pic);

    av_freep(&avctx->coded_frame);
    av_freep(&ctx->val);

    return 0;
}

static av_cold int vble_decode_init(AVCodecContext *avctx)
{
    VBLEContext *ctx = avctx->priv_data;

    /* Stash for later use */
    ctx->avctx = avctx;

    avctx->pix_fmt = PIX_FMT_YUV420P;
    avctx->bits_per_raw_sample = 8;
    avctx->coded_frame = avcodec_alloc_frame();

    if (!avctx->coded_frame) {
        av_log(avctx, AV_LOG_ERROR, "Could not allocate frame.\n");
        return AVERROR(ENOMEM);
    }

    ctx->size = avpicture_get_size(avctx->pix_fmt,
                                   avctx->width, avctx->height);

    ctx->val = av_malloc(ctx->size * sizeof(*ctx->val));

    if (!ctx->val) {
        av_log(avctx, AV_LOG_ERROR, "Could not allocate values buffer.\n");
        vble_decode_close(avctx);
        return AVERROR(ENOMEM);
    }

    return 0;
}

AVCodec ff_vble_decoder = {
    .name           = "vble",
    .type           = AVMEDIA_TYPE_VIDEO,
    .id             = CODEC_ID_VBLE,
    .priv_data_size = sizeof(VBLEContext),
    .init           = vble_decode_init,
    .close          = vble_decode_close,
    .decode         = vble_decode_frame,
    .capabilities   = CODEC_CAP_DR1,
    .long_name      = NULL_IF_CONFIG_SMALL("VBLE Lossless Codec"),
};
