use std::rc::Rc;
use std::cell::{RefCell, RefMut, Ref};


#[derive(Debug)]
struct SharedRcOption<T>(Option<Rc<RefCell<T>>>);

impl<T> SharedRcOption<T> {
    fn empty() -> Self {
        Self(None)
    }

    fn new(element: T) -> Self {
        Self(Some(Rc::new(RefCell::new(element))))
    }

    fn is_empty(&self) -> bool {
        self.0.is_none()
    }

    fn borrow_mut(&mut self) -> RefMut<T> {
        self.0.as_mut().expect(
            "Empty SharedRCOption cannot be unwrapped"
        ).borrow_mut()
    }

    fn borrow(&self) -> Ref<T> {
        self.0.as_ref().expect(
            "Empty SharedRCOption cannot be unwrapped"
        ).borrow()
    }

    fn clear(&mut self) {
        self.0 = None;
    }
}

impl<T> Clone for SharedRcOption<T> {
    fn clone(&self) -> Self {
        Self(self.0.clone())
    }
}

#[derive(Debug)]
struct Edge {
    next: SharedRcOption<Edge>,
}

impl Edge {
    fn new() -> Self {
        Self {
            next: SharedRcOption::empty(),
        }
    }

    fn as_shared_rc_option(self) -> SharedRcOption<Self> {
        SharedRcOption::new(self)
    }
}


fn main() {
    let mut a = Edge::new().as_shared_rc_option();
    a.borrow_mut().next = Edge::new().as_shared_rc_option();
    a.borrow_mut().next.borrow_mut().next = Edge::new().as_shared_rc_option();
    a.borrow_mut().next.borrow_mut().next.borrow_mut().next = Edge::new().as_shared_rc_option();
    a.borrow_mut().next.borrow_mut().next.borrow_mut().next.borrow_mut().next =
        a.clone();
    //a.next.borrow_mut().next.clear();

    println!("{:?}", a);
}