////////////////////////////////////////////////////////////
//~ Backdrop shader

ComputeShader2D(V_BackdropCS, 8, 8)
{
    V_DParams params = G_Dereference<V_DParams>(V_ShaderConst_Params)[0];
    RWTexture2D<Vec4> target = G_Dereference<Vec4>(params.target_rw);

    Vec2U32 target_pos = SV_DispatchThreadID;
    Vec2I32 target_size = params.target_size;
    if (target_pos.x < target_size.x && target_pos.y < target_size.y)
    {
        Vec4 result = 0;

        /* Checkered square color */
        {
            i32 color_idx = 0;
            Vec4 colors[2] = {
                params.background_color_a,
                params.background_color_b
            };
            Vec2 world_pos = mul(params.draw_to_world_xf, Vec3(target_pos, 1));
            Vec2 world_pos_modded = fmod(abs(world_pos), Vec2(2, 2));
            if (world_pos_modded.x < 1)
            {
                color_idx = !color_idx;
            }
            if (world_pos_modded.y < 1)
            {
                color_idx = !color_idx;
            }
            if (world_pos.x < 0)
            {
                color_idx = !color_idx;
            }
            if (world_pos.y < 0)
            {
                color_idx = !color_idx;
            }
            result = colors[color_idx];
        }

        /* Axis color */
        {
            f32 half_thickness = 1;
            Vec2 zero_screen = mul(params.world_to_draw_xf, Vec3(0, 0, 1));
            f32 x_dist = abs(target_pos.x - zero_screen.x);
            f32 y_dist = abs(target_pos.y - zero_screen.y);
            if (y_dist <= half_thickness)
            {
                result = Color_Red;
            }
            else if (x_dist <= half_thickness)
            {
                result = Color_Green;
            }
        }

        target[target_pos] = result;
    }
}

////////////////////////////////////////////////////////////
//~ Quad shader

//////////////////////////////
//- Vertex shader

VertexShader(V_DQuadVS, V_DQuadPSInput)
{
    V_DParams params = G_Dereference<V_DParams>(V_ShaderConst_Params)[0];
    StructuredBuffer<V_DQuad> quads = G_Dereference<V_DQuad>(params.quads);
    RWTexture2D<Vec4> target = G_Dereference<Vec4>(params.target_rw);

    V_DQuad quad = quads[SV_InstanceID];

    Vec2 rect_uv = RectUvFromVertexId(SV_VertexID);
    // Vec2 tex_uv = lerp(quad.tex_uv0, quad.tex_uv1, rect_uv);
    // Vec2 target_pos = lerp(quad.p0, quad.p1, rect_uv);
    Vec2 target_pos = 0;

    V_DQuadPSInput result;
    result.sv_position = Vec4(NdcFromPos(target_pos, countof(target)).xy, 0, 1);
    result.quad_idx = SV_InstanceID;
    return result;
}

//////////////////////////////
//- Pixel shader

PixelShader(V_DQuadPS, V_DQuadPSOutput, V_DQuadPSInput input)
{
    V_DParams params = G_Dereference<V_DParams>(V_ShaderConst_Params)[0];
    StructuredBuffer<V_DQuad> quads = G_Dereference<V_DQuad>(params.quads);
    V_DQuad quad = quads[input.quad_idx];

    Vec4 final_color = 0;

    V_DQuadPSOutput output;
    output.sv_target0 = final_color;
    return output;
}

////////////////////////////////////////////////////////////
//~ Shape shader

//////////////////////////////
//- Vertex shader

VertexShader(V_DVertVS, V_DVertPSInput)
{
    V_DParams params = G_Dereference<V_DParams>(V_ShaderConst_Params)[0];
    StructuredBuffer<V_DVert> verts = G_Dereference<V_DVert>(params.shape_verts);
    RWTexture2D<Vec4> target = G_Dereference<Vec4>(params.target_rw);

    V_DVert vert = verts[SV_VertexID];

    Vec2 target_pos = vert.pos;

    V_DVertPSInput result;
    result.sv_position = Vec4(NdcFromPos(target_pos, countof(target)).xy, 0, 1);
    result.color_lin = vert.color_lin;
    return result;
}

//////////////////////////////
//- Pixel shader

PixelShader(V_DVertPS, V_DVertPSOutput, V_DVertPSInput input)
{
    V_DVertPSOutput output;
    output.sv_target0 = input.color_lin;
    return output;
}