use std::rc::{Rc, Weak};
use std::cell::RefCell;
use std::ptr;
use r9_macro::SharedFromSelf;
use r9_macro_derive::SharedFromSelf;

#[derive(Default)]
#[derive(SharedFromSelf)]
pub struct ListHead<T> {
    prev: Weak::<RefCell::<Self>>,
    next: Weak::<RefCell::<Self>>,
    data: Weak::<RefCell::<T>>,
    _self_wp: Weak::<RefCell::<Self>>,
}

impl<T> ListHead<T> {

    fn new(data: Weak::<RefCell::<T>>) -> Rc::<RefCell::<Self>> {
        let this = Rc::new(RefCell::new(Self{
            prev: Default::default(),
            next: Default::default(),
            data: data,
            _self_wp: Default::default(),
        }));
        this.borrow_mut()._self_wp = Rc::downgrade(&this);
        this.borrow_mut().init();
        return this;
    }

    pub fn new_head() -> Rc::<RefCell::<Self>> {
        return Self::new(Default::default());
    }

    pub fn new_node(data: Weak::<RefCell::<T>>) -> Rc::<RefCell::<Self>> {
        return Self::new(data);
    }

    fn init(&mut self) {
        self.prev = Rc::downgrade(&self.shared_from_self());
        self.next = Rc::downgrade(&self.shared_from_self());
    }

    pub fn data(&self) -> Weak::<RefCell::<T>> {
        return self.data.clone();
    }

    pub fn del_init(&mut self) {
        self.next.upgrade().unwrap().borrow_mut().prev = self.prev.clone();
        self.prev.upgrade().unwrap().borrow_mut().next = self.next.clone();
        self.init();
    }

    pub fn empty(&self) -> bool {
        return ptr::eq(self.next.as_ptr(), Rc::as_ptr(&self.shared_from_self()));
    }

    pub fn add_tail(head: &Rc::<RefCell::<Self>>, pnew: &Rc::<RefCell::<Self>>) {
        let prev = &head.borrow_mut().prev.clone();
        let next = head;

        next.borrow_mut().prev = Rc::downgrade(pnew);
        pnew.borrow_mut().next = Rc::downgrade(&next);
        pnew.borrow_mut().prev = prev.clone();
        prev.upgrade().unwrap().borrow_mut().next = Rc::downgrade(pnew);
    }

    pub fn first_entry(&self) -> Weak::<RefCell::<T>> {
        if self.empty() {
            panic!("");
        }
        return self.next.upgrade().unwrap().borrow().data();
    }

    pub fn replace_init(head: &Rc::<RefCell::<Self>>, pnew: &Rc::<RefCell::<Self>>) {
        if head.borrow().empty() {
            return;
        }
        pnew.borrow_mut().next = head.borrow().next.clone();
        pnew.borrow_mut().next.upgrade().unwrap().borrow_mut().prev = Rc::downgrade(pnew);
        pnew.borrow_mut().prev = head.borrow().prev.clone();
        pnew.borrow_mut().prev.upgrade().unwrap().borrow_mut().next = Rc::downgrade(pnew);
        head.borrow_mut().init();
    }

    pub fn for_each(&self, cb: fn (&Weak::<RefCell::<T>>) -> bool) {
        let mut pos = self.next.clone();
        let self_weak = Rc::downgrade(&self.shared_from_self());
        while !Weak::ptr_eq(&pos, &self_weak) {
            if !cb(&pos.upgrade().unwrap().borrow().data()) {
                break;
            }
            pos = pos.upgrade().unwrap().borrow().next.clone();
        }
    }

}