use core::fmt;
use core::marker::PhantomData;
use core::pin::Pin;
use futures_core::future::Future;
use futures_core::stream::Stream;
use futures_core::task::{Context, Poll};
use futures_sink::Sink;
use pin_utils::{unsafe_pinned, unsafe_unpinned};
#[must_use = "sinks do nothing unless polled"]
pub struct With<Si, Item, U, Fut, F> {
sink: Si,
f: F,
state: Option<Fut>,
_phantom: PhantomData<fn(U) -> Item>,
}
impl<Si, Item, U, Fut, F> Unpin for With<Si, Item, U, Fut, F>
where
Si: Unpin,
Fut: Unpin,
{}
impl<Si, Item, U, Fut, F> fmt::Debug for With<Si, Item, U, Fut, F>
where
Si: fmt::Debug,
Fut: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("With")
.field("sink", &self.sink)
.field("state", &self.state)
.finish()
}
}
impl<Si, Item, U, Fut, F> With<Si, Item, U, Fut, F>
where Si: Sink<Item>,
F: FnMut(U) -> Fut,
Fut: Future,
{
unsafe_pinned!(sink: Si);
unsafe_unpinned!(f: F);
unsafe_pinned!(state: Option<Fut>);
pub(super) fn new<E>(sink: Si, f: F) -> Self
where
Fut: Future<Output = Result<Item, E>>,
E: From<Si::Error>,
{
With {
state: None,
sink,
f,
_phantom: PhantomData,
}
}
}
impl<S, Item, U, Fut, F> Stream for With<S, Item, U, Fut, F>
where S: Stream + Sink<Item>,
F: FnMut(U) -> Fut,
Fut: Future
{
type Item = S::Item;
fn poll_next(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Option<S::Item>> {
self.sink().poll_next(cx)
}
fn size_hint(&self) -> (usize, Option<usize>) {
self.sink.size_hint()
}
}
impl<Si, Item, U, Fut, F, E> With<Si, Item, U, Fut, F>
where Si: Sink<Item>,
F: FnMut(U) -> Fut,
Fut: Future<Output = Result<Item, E>>,
E: From<Si::Error>,
{
pub fn get_ref(&self) -> &Si {
&self.sink
}
pub fn get_mut(&mut self) -> &mut Si {
&mut self.sink
}
pub fn get_pin_mut(self: Pin<&mut Self>) -> Pin<&mut Si> {
self.sink()
}
pub fn into_inner(self) -> Si {
self.sink
}
fn poll(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Result<(), E>> {
let item = match self.as_mut().state().as_pin_mut() {
None => return Poll::Ready(Ok(())),
Some(fut) => ready!(fut.poll(cx))?,
};
self.as_mut().state().set(None);
self.as_mut().sink().start_send(item)?;
Poll::Ready(Ok(()))
}
}
impl<Si, Item, U, Fut, F, E> Sink<U> for With<Si, Item, U, Fut, F>
where Si: Sink<Item>,
F: FnMut(U) -> Fut,
Fut: Future<Output = Result<Item, E>>,
E: From<Si::Error>,
{
type Error = E;
fn poll_ready(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Result<(), Self::Error>> {
ready!(self.as_mut().poll(cx))?;
ready!(self.as_mut().sink().poll_ready(cx)?);
Poll::Ready(Ok(()))
}
fn start_send(
mut self: Pin<&mut Self>,
item: U,
) -> Result<(), Self::Error> {
let future = (self.as_mut().f())(item);
self.as_mut().state().set(Some(future));
Ok(())
}
fn poll_flush(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Result<(), Self::Error>> {
ready!(self.as_mut().poll(cx))?;
ready!(self.as_mut().sink().poll_flush(cx))?;
Poll::Ready(Ok(()))
}
fn poll_close(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Result<(), Self::Error>> {
ready!(self.as_mut().poll(cx))?;
ready!(self.as_mut().sink().poll_close(cx))?;
Poll::Ready(Ok(()))
}
}