// Invert Effect Shader
// Inverts color values

struct Uniforms {
    // params packed as vec4s for proper 16-byte alignment
    // params[0-3] in params0, params[4-7] in params1, etc.
    params0: vec4<f32>,
    params1: vec4<f32>,
    params2: vec4<f32>,
    params3: vec4<f32>,
    texture_width: f32,
    texture_height: f32,
    time: f32,
    mix: f32,
}

struct VertexOutput {
    @builtin(position) position: vec4<f32>,
    @location(0) uv: vec2<f32>,
}

@group(0) @binding(0) var source_tex: texture_2d<f32>;
@group(0) @binding(1) var source_sampler: sampler;
@group(0) @binding(2) var<uniform> uniforms: Uniforms;

@vertex
fn vs_main(@builtin(vertex_index) vertex_index: u32) -> VertexOutput {
    var out: VertexOutput;
    let x = f32((vertex_index & 1u) << 1u);
    let y = f32(vertex_index & 2u);
    out.position = vec4<f32>(x * 2.0 - 1.0, 1.0 - y * 2.0, 0.0, 1.0);
    out.uv = vec2<f32>(x, y);
    return out;
}

// The HDR pipeline feeds these shaders LINEAR light, but "invert" is a
// perceptual operation defined in gamma/display space (Photoshop, GIMP, etc.).
// Convert to sRGB, invert there, then convert back to linear. The sRGB helpers
// (linear_to_srgb / srgb_to_linear) come from the prepended COLOR_WGSL prelude.

@fragment
fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
    let src = textureSample(source_tex, source_sampler, in.uv);
    let amount = uniforms.params0.x; // params[0]

    let src_srgb = linear_to_srgb(src.rgb);
    let inverted = vec3<f32>(1.0) - src_srgb;
    let result_srgb = mix(src_srgb, inverted, amount * uniforms.mix);

    return vec4<f32>(srgb_to_linear(result_srgb), src.a);
}