use std::os::raw::c_void;
type IUnknownVPtr = c_void;

struct BritishShortHairCat {

}

trait ComInterface {
    fn gen_vtable<T, P>();
}

trait ICat {

}

impl ComInterface for dyn ICat {
    fn gen_vtable<T, P>() {
        macro_rules! icat_gen_vtable {
            ($generic:ty, $offset:ty) => {
                IAnimal::gen_vtable::<$generic, $offset>();

                unsafe extern "stdcall" fn add_ref<T, P: Offset>(this: *mut IUnknownVPtr) {
                    println!("Offset value: {}", P::value());
                    let this = this.sub(P::value()) as *mut T;
                    // (*this).add_ref();
                }
            }
        }

        icat_gen_vtable!(T, P);
    }
}

trait IAnimal {

}

impl ComInterface for dyn IAnimal {
    fn gen_vtable<T, P>() {
        macro_rules! ianimal_gen_vtable {
            ($generic:ty, $offset:ty) => {

            }
        }

        ianimal_gen_vtable!(T, P);
    }
}

fn main() {
    ICat::gen_vtable::<BritishShortHairCat, ONE>();
}

trait Offset {
    fn value() -> usize;
}

struct ONE {}

impl Offset for ONE {
    fn value() -> usize {
        1
    }
}