use std::cell::RefCell;
use std::rc::{Rc, Weak};

#[derive(Debug)]
struct Node {
    value: i32,
    parent: RefCell<Weak<Node>>,
    children: RefCell<Vec<Rc<Node>>>,
}
fn main() {
    let root = Rc::new(Node {
        value: 0,
        parent: RefCell::new(Weak::new()),
        children: RefCell::new(vec![]),
    });

    let leaf = Rc::new(Node {
        value: 3,
        parent: RefCell::new(Weak::new()),
        children: RefCell::new(vec![]),
    });
    println!(
        "leaf strong = {}, weak = {}",
        Rc::strong_count(&leaf),
        Rc::weak_count(&leaf),
    );
    println!(
        "root strong = {}, weak = {}",
        Rc::strong_count(&root),
        Rc::weak_count(&root),
    );
    println!("-------------------------------");
    {
        let branch = Rc::new(Node {
            value: 10,
            parent: RefCell::new(Rc::downgrade(&root)),
            children: RefCell::new(vec![Rc::clone(&leaf)]),
        });
        *leaf.parent.borrow_mut() = Rc::downgrade(&branch);
        root.children.borrow_mut().push(Rc::clone(&branch));
        println!(
            "root strong = {}, weak = {}",
            Rc::strong_count(&root),
            Rc::weak_count(&root),
        );
        println!(
            "branch strong = {}, weak = {}",
            Rc::strong_count(&branch),
            Rc::weak_count(&branch),
        );
        println!(
            "leaf strong = {}, weak = {}",
            Rc::strong_count(&leaf),
            Rc::weak_count(&leaf),
        );
        println!("-------------------------------");
    }
    println!("leaf parent = {:?}", leaf.parent.borrow().upgrade());
    println!(
        "leaf strong = {}, weak = {}",
        Rc::strong_count(&leaf),
        Rc::weak_count(&leaf),
    );
    println!(
        "root strong = {}, weak = {}",
        Rc::strong_count(&root),
        Rc::weak_count(&root),
    );
}