#import bevy_core_pipeline::fullscreen_vertex_shader::FullscreenVertexOutput

struct PostProcessSettings {
    scale: f32,
}

@group(0) @binding(0) var screen_texture: texture_2d<f32>;
@group(0) @binding(1) var texture_sampler: sampler;
@group(0) @binding(2) var<uniform> settings: PostProcessSettings;

const dither = array<array<f32, 8>, 8>(
    array<f32, 8>( 0.0, 32.0, 8.0,  40.0,  2.0, 34.0, 10.0, 42.0), 
    array<f32, 8>(48.0, 16.0, 56.0, 24.0, 50.0, 18.0, 58.0, 26.0),
    array<f32, 8>(12.0, 44.0,  4.0, 36.0, 14.0, 46.0,  6.0, 38.0), 
    array<f32, 8>(60.0, 28.0, 52.0, 20.0, 62.0, 30.0, 54.0, 22.0),
    array<f32, 8>( 3.0, 35.0, 11.0, 43.0,  1.0, 33.0,  9.0, 41.0),
    array<f32, 8>(51.0, 19.0, 59.0, 27.0, 49.0, 17.0, 57.0, 25.0),
    array<f32, 8>(15.0, 47.0,  7.0, 39.0, 13.0, 45.0,  5.0, 37.0),
    array<f32, 8>(63.0, 31.0, 55.0, 23.0, 61.0, 29.0, 53.0, 21.0)
);

fn find_closest(x: i32, y: i32, c0: f32) -> f32 {
    
    
    var limit = 0.0;

    if (x < 8) {
        limit = (dither[x][y]+1) / 64.0;
    }

    if (c0 < limit) {
        return 0.0;
    }

    return 1.0;
}

@fragment
fn fragment(in: FullscreenVertexOutput) -> @location(0) vec4<f32> {
    let a: f32 = textureSample(screen_texture, texture_sampler, in.uv).a;
    
    let gr: f32 = textureSample(screen_texture, texture_sampler, in.uv).r * 0.2989;
    let gg: f32 = textureSample(screen_texture, texture_sampler, in.uv).g * 0.587;
    let gb: f32 = textureSample(screen_texture, texture_sampler, in.uv).b * 0.114;
    let grayscale: f32 = gr + gg + gb;

    let uvx: f32 = in.position.x;
    let uvy: f32 = in.position.y;

    let x: i32 = i32(uvx * settings.scale) % 8;
    let y: i32 = i32(uvy * settings.scale) % 8;

    let final_gray = find_closest(x, y, grayscale);

    return vec4<f32>(
        final_gray, final_gray, final_gray, 0.0
    );
}