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    use core::{marker::PhantomData, ptr::NonNull};

    use generic_array::ArrayLength;

    use crate::{
        sealed::spsc as sealed,
        spsc::{MultiCore, Queue},
    };

    impl<T, N, U, C> Queue<T, N, U, C>
    where
        N: ArrayLength<T>,
        U: sealed::Uxx,
        C: sealed::XCore,
    {
        /// Splits a statically allocated queue into producer and consumer end points
        pub fn split<'rb>(&'rb mut self) -> (Producer<'rb, T, N, U, C>, Consumer<'rb, T, N, U, C>) {
            (
                Producer {
                    rb: unsafe { NonNull::new_unchecked(self) },
                    _marker: PhantomData,
                },
                Consumer {
                    rb: unsafe { NonNull::new_unchecked(self) },
                    _marker: PhantomData,
                },
            )
        }
    }

    /// A queue "consumer"; it can dequeue items from the queue
    // NOTE the consumer semantically owns the `head` pointer of the queue
    pub struct Consumer<'a, T, N, U = usize, C = MultiCore>
    where
        N: ArrayLength<T>,
        U: sealed::Uxx,
        C: sealed::XCore,
    {
        rb: NonNull<Queue<T, N, U, C>>,
        _marker: PhantomData<&'a ()>,
    }

    unsafe impl<'a, T, N, U, C> Send for Consumer<'a, T, N, U, C>
    where
        N: ArrayLength<T>,
        T: Send,
        U: sealed::Uxx,
        C: sealed::XCore,
    {
    }

    /// A queue "producer"; it can enqueue items into the queue
    // NOTE the producer semantically owns the `tail` pointer of the queue
    pub struct Producer<'a, T, N, U = usize, C = MultiCore>
    where
        N: ArrayLength<T>,
        U: sealed::Uxx,
        C: sealed::XCore,
    {
        rb: NonNull<Queue<T, N, U, C>>,
        _marker: PhantomData<&'a ()>,
    }

    unsafe impl<'a, T, N, U, C> Send for Producer<'a, T, N, U, C>
    where
        N: ArrayLength<T>,
        T: Send,
        U: sealed::Uxx,
        C: sealed::XCore,
    {
    }

    macro_rules! impl_ {
        ($uxx:ident) => {
            impl<'a, T, N, C> Consumer<'a, T, N, $uxx, C>
            where
                N: ArrayLength<T>,
                C: sealed::XCore,
            {
                /// Returns if there are any items to dequeue. When this returns true, at least the
                /// first subsequent dequeue will succeed.
                pub fn ready(&self) -> bool {
                    let head = unsafe { self.rb.as_ref().0.head.load_relaxed() };
                    let tail = unsafe { self.rb.as_ref().0.tail.load_acquire() }; // ▼
                    return head != tail;
                }

                /// Returns the item in the front of the queue without dequeuing, or `None` if the queue is empty.
                ///
                /// # Examples
                /// ```
                /// use heapless::spsc::Queue;
                /// use heapless::consts::*;
                ///
                /// let mut queue: Queue<u8, U235, _> = Queue::u8();
                /// let (mut producer, mut consumer) = queue.split();
                /// assert_eq!(None, consumer.peek());
                /// producer.enqueue(1);
                /// assert_eq!(Some(&1), consumer.peek());
                /// assert_eq!(Some(1), consumer.dequeue());
                /// assert_eq!(None, consumer.peek());
                /// ```
                pub fn peek(&self) -> Option<&T> {
                    let head = unsafe { self.rb.as_ref().0.head.load_relaxed() };
                    let tail = unsafe { self.rb.as_ref().0.tail.load_acquire() };

                    if head != tail {
                        Some(unsafe { self._peek(head) })
                    } else {
                        None
                    }
                }

                /// Returns the item in the front of the queue, or `None` if the queue is empty
                pub fn dequeue(&mut self) -> Option<T> {
                    let head = unsafe { self.rb.as_ref().0.head.load_relaxed() };
                    let tail = unsafe { self.rb.as_ref().0.tail.load_acquire() }; // ▼

                    if head != tail {
                        Some(unsafe { self._dequeue(head) }) // ▲
                    } else {
                        None
                    }
                }

                /// Returns the item in the front of the queue, without checking if it's empty
                ///
                /// # Unsafety
                ///
                /// If the queue is empty this is equivalent to calling `mem::uninitialized`
                pub unsafe fn dequeue_unchecked(&mut self) -> T {
                    let head = self.rb.as_ref().0.head.load_relaxed();
                    debug_assert_ne!(head, self.rb.as_ref().0.tail.load_acquire());
                    self._dequeue(head) // ▲
                }

                /// Returns the maximum number of elements the queue can hold
                pub fn capacity(&self) -> $uxx {
                    unsafe { self.rb.as_ref().capacity() }
                }

                /// Returns the number of elements in the queue
                ///
                /// # Note
                ///
                /// This is a conservative estimate. Interrupt during this function
                /// might cause that the `Consumer` actually has more than N items available.
                pub fn len(&self) -> $uxx {
                    let head = unsafe { self.rb.as_ref().0.head.load_relaxed() };
                    let tail = unsafe { self.rb.as_ref().0.tail.load_acquire() };
                    tail.wrapping_sub(head)
                }

                unsafe fn _peek(&self, head: $uxx) -> &T {
                    let rb = self.rb.as_ref();

                    let cap = rb.capacity();

                    let item = (rb.0.buffer.as_ptr() as *const T).add(usize::from(head % cap));
                    &*item
                }

                unsafe fn _dequeue(&mut self, head: $uxx) -> T {
                    let rb = self.rb.as_ref();

                    let cap = rb.capacity();

                    let item = (rb.0.buffer.as_ptr() as *const T)
                        .add(usize::from(head % cap))
                        .read();
                    rb.0.head.store_release(head.wrapping_add(1)); // ▲
                    item
                }
            }

            impl<'a, T, N, C> Producer<'a, T, N, $uxx, C>
            where
                N: ArrayLength<T>,
                C: sealed::XCore,
            {
                /// Returns if there is any space to enqueue a new item. When this returns true, at
                /// least the first subsequent enqueue will succeed.
                pub fn ready(&self) -> bool {
                    let cap = unsafe { self.rb.as_ref().capacity() };

                    let tail = unsafe { self.rb.as_ref().0.tail.load_relaxed() };
                    // NOTE we could replace this `load_acquire` with a `load_relaxed` and this method
                    // would be sound on most architectures but that change would result in UB according
                    // to the C++ memory model, which is what Rust currently uses, so we err on the side
                    // of caution and stick to `load_acquire`. Check issue google#sanitizers#882 for
                    // more details.
                    let head = unsafe { self.rb.as_ref().0.head.load_acquire() };
                    return head.wrapping_add(cap) != tail;
                }

                /// Adds an `item` to the end of the queue
                ///
                /// Returns back the `item` if the queue is full
                pub fn enqueue(&mut self, item: T) -> Result<(), T> {
                    let cap = unsafe { self.rb.as_ref().capacity() };
                    let tail = unsafe { self.rb.as_ref().0.tail.load_relaxed() };
                    // NOTE we could replace this `load_acquire` with a `load_relaxed` and this method
                    // would be sound on most architectures but that change would result in UB according
                    // to the C++ memory model, which is what Rust currently uses, so we err on the side
                    // of caution and stick to `load_acquire`. Check issue google#sanitizers#882 for
                    // more details.
                    let head = unsafe { self.rb.as_ref().0.head.load_acquire() }; // ▼

                    if tail.wrapping_sub(head) > cap - 1 {
                        Err(item)
                    } else {
                        unsafe { self._enqueue(tail, item) }; // ▲
                        Ok(())
                    }
                }

                /// Returns the maximum number of elements the queue can hold
                pub fn capacity(&self) -> $uxx {
                    unsafe { self.rb.as_ref().capacity() }
                }

                /// Returns the number of elements in the queue
                ///
                /// # Note
                ///
                /// This is a conservative estimate. Interrupt during this function
                /// might cause that the `Producer` actually has more than N items of available space.
                pub fn len(&self) -> $uxx {
                    let head = unsafe { self.rb.as_ref().0.head.load_acquire() };
                    let tail = unsafe { self.rb.as_ref().0.tail.load_relaxed() };
                    tail.wrapping_sub(head)
                }

                /// Adds an `item` to the end of the queue without checking if it's full
                ///
                /// # Unsafety
                ///
                /// If the queue is full this operation will leak a value (T's destructor won't run on
                /// the value that got overwritten by `item`), *and* will allow the `dequeue` operation
                /// to create a copy of `item`, which could result in `T`'s destructor running on `item`
                /// twice.
                pub unsafe fn enqueue_unchecked(&mut self, item: T) {
                    let tail = self.rb.as_ref().0.tail.load_relaxed();
                    debug_assert_ne!(tail.wrapping_add(1), self.rb.as_ref().0.head.load_acquire());
                    self._enqueue(tail, item); // ▲
                }

                unsafe fn _enqueue(&mut self, tail: $uxx, item: T) {
                    let rb = self.rb.as_mut();

                    let cap = rb.capacity();

                    // NOTE(ptr::write) the memory slot that we are about to write to is
                    // uninitialized. We use `ptr::write` to avoid running `T`'s destructor on the
                    // uninitialized memory
                    (rb.0.buffer.as_mut_ptr() as *mut T)
                        .add(usize::from(tail % cap))
                        .write(item);
                    rb.0.tail.store_release(tail.wrapping_add(1)); // ▲
                }
            }
        };
    }

    impl_!(u8);
    impl_!(u16);
    impl_!(usize);

    #[cfg(test)]
    mod tests {
        use crate::{consts::*, spsc::Queue};

        #[test]
        fn sanity() {
            let mut rb: Queue<i32, U2> = Queue::new();

            let (mut p, mut c) = rb.split();

            assert_eq!(c.dequeue(), None);

            p.enqueue(0).unwrap();

            assert_eq!(c.dequeue(), Some(0));
        }
    }