use crate::Doubly;
use core::iter::FusedIterator;
use orx_pinned_vec::PinnedVec;
use orx_selfref_col::{CoreCol, Node, NodePtr};

/// An ordered iterator mutable references to elements of the doubly linked list.
///
/// Can be created by calling the `iter_mut` method.
pub struct DoublyIterMut<'a, T, P>
where
    P: PinnedVec<Node<Doubly<T>>>,
{
    col: &'a mut CoreCol<Doubly<T>, P>,
    current: Option<NodePtr<Doubly<T>>>,
    current_back: Option<NodePtr<Doubly<T>>>,
}

impl<'a, T, P> DoublyIterMut<'a, T, P>
where
    P: PinnedVec<Node<Doubly<T>>>,
{
    pub(crate) fn new(
        col: &'a mut CoreCol<Doubly<T>, P>,
        current: Option<NodePtr<Doubly<T>>>,
        current_back: Option<NodePtr<Doubly<T>>>,
    ) -> Self {
        Self {
            col,
            current,
            current_back,
        }
    }

    pub(crate) fn restart_for(
        &mut self,
        current: Option<NodePtr<Doubly<T>>>,
        current_back: Option<NodePtr<Doubly<T>>>,
    ) {
        self.current = current;
        self.current_back = current_back;
    }

    fn end(&mut self) {
        self.current = None;
        self.current_back = None;
    }
}

impl<'a, T, P> Iterator for DoublyIterMut<'a, T, P>
where
    P: PinnedVec<Node<Doubly<T>>>,
{
    type Item = &'a mut T;

    fn next(&mut self) -> Option<Self::Item> {
        match &self.current {
            Some(p) => {
                let ptr = p.ptr_mut();
                match self.current == self.current_back {
                    false => self.current = self.col.node(p).next().get().cloned(),
                    true => self.end(),
                }

                unsafe { &mut *ptr }.data_mut()
            }
            None => None,
        }
    }
}

impl<T, P> DoubleEndedIterator for DoublyIterMut<'_, T, P>
where
    P: PinnedVec<Node<Doubly<T>>>,
{
    fn next_back(&mut self) -> Option<Self::Item> {
        match &self.current_back {
            Some(p) => {
                let ptr = p.ptr_mut();
                match self.current == self.current_back {
                    false => self.current_back = self.col.node(p).prev().get().cloned(),
                    true => self.end(),
                }
                unsafe { &mut *ptr }.data_mut()
            }
            None => None,
        }
    }
}

impl<T, P> FusedIterator for DoublyIterMut<'_, T, P> where P: PinnedVec<Node<Doubly<T>>> {}
