struct Params {
    block_size: vec2<i32>,
    offsets_stride: u32
}

struct BlockOffset {
    score: f32,
    offset: vec2<i32>,
}

@group(0) @binding(0) var<uniform> params: Params;
@group(0) @binding(1) var<storage, read_write> offsets: array<BlockOffset>;
@group(0) @binding(2) var next: texture_2d<f32>;
@group(0) @binding(3) var prev: texture_2d<f32>;

@compute @workgroup_size(1) fn main(@builtin(global_invocation_id) global_id: vec3<u32>) {
    let uv = vec2<i32>(global_id.xy) * params.block_size;

    var best_err = 100000000.;
    var best_offset = vec2(0,0);
    for (var ox = -5; ox <= 5; ox++) {
    for (var oy = -5; oy <= 5; oy++) {
        let offset = vec2(ox,oy);

        var err = 0.;
        for (var x = 0; x < params.block_size.x; x++) {
        for (var y = 0; y < params.block_size.y; y++) {
            let base = uv+vec2(x,y);
            let pcol = textureLoad(prev, base+offset, 0).rgb;
            let ncol = textureLoad(next, base, 0).rgb;
            err += distance(pcol, ncol);
        }}
        
        if err < best_err {
            best_err = err;
            best_offset = offset;
        }
    }}

    offsets[global_id.x + global_id.y * params.offsets_stride] = BlockOffset(best_err, best_offset);
}

// fn colormap_vec(v: vec2<f32>) -> vec3<f32> {
//     return vec3(v.y, v.x - 0.5 * v.y, -v.x - 0.5 * v.y);
// }