module main

pub type Mat4 = [16]f32

pub fn (a Mat4) * (b Mat4) Mat4 {
    mut res := Mat4{}
    for i := 0; i < 4; i++ {
        for j := 0; j < 4; j++ {
            res[j * 4 + i] = 0
            for k := 0; k < 4; k++ {
                res[j * 4 + i] += a[k * 4 + i] * b[j * 4 + k]
            }
        }
    }
    return res
}

interface IGameObject {
    parent    ?&IGameObject
    transform Mat4
    world_transform() Mat4
}

struct GameObject implements IGameObject {
mut:
    transform Mat4
    parent    ?&IGameObject
}

fn (gameobject GameObject) world_transform() Mat4 {
    if mut p := gameobject.parent {
        return p.world_transform() * gameobject.transform
    }
    return gameobject.transform
}

fn test_main() {
    t := GameObject{}
    a := dump(t.world_transform())
    assert a.len == 16
}