/*
 * FFv1 codec
 *
 * Copyright (c) 2024 Lynne <dev@lynne.ee>
 *
 * 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
 */

ivec4 load_components(ivec2 pos)
{
    if (planar_rgb == 0)
        return ivec4(imageLoad(src[0], pos));

    ivec4 pix;
    for (int i = 0; i < (3 + transparency); i++)
        pix[i] = int(imageLoad(src[i], pos)[0]);

    /* Swizzle out the difference */
    if (bits > 8 && bits < 16 && transparency == 0)
        return pix.bgra;
    return pix.brga;
}

void bypass_sample(ivec2 pos)
{
    imageStore(dst[0], pos, load_components(pos));
}

void bypass_block(in SliceContext sc)
{
    ivec2 start = ivec2(gl_LocalInvocationID) + sc.slice_pos;
    ivec2 end = sc.slice_pos + sc.slice_dim;
    for (uint y = start.y; y < end.y; y += gl_WorkGroupSize.y)
        for (uint x = start.x; x < end.x; x += gl_WorkGroupSize.x)
            bypass_sample(ivec2(x, y));
}

void transform_sample(ivec2 pos, ivec2 rct_coef)
{
    ivec4 pix = load_components(pos);
    pix.b -= pix.g;
    pix.r -= pix.g;
    pix.g += (pix.r*rct_coef.x + pix.b*rct_coef.y) >> 2;
    pix.b += offset;
    pix.r += offset;
    imageStore(dst[0], pos, pix);
}

void transform_block(in SliceContext sc)
{
    const ivec2 rct_coef = sc.slice_rct_coef;
    const ivec2 start = ivec2(gl_LocalInvocationID) + sc.slice_pos;
    const ivec2 end = sc.slice_pos + sc.slice_dim;

    for (uint y = start.y; y < end.y; y += gl_WorkGroupSize.y)
        for (uint x = start.x; x < end.x; x += gl_WorkGroupSize.x)
            transform_sample(ivec2(x, y), rct_coef);
}

void main()
{
    const uint slice_idx = gl_WorkGroupID.y*gl_NumWorkGroups.x + gl_WorkGroupID.x;

    if (slice_ctx[slice_idx].slice_coding_mode == 1)
        bypass_block(slice_ctx[slice_idx]);
    else
        transform_block(slice_ctx[slice_idx]);
}