use core::fmt;
use core::pin::Pin;
use futures_core::future::{FusedFuture, Future};
use futures_core::ready;
use futures_core::stream::TryStream;
use futures_core::task::{Context, Poll};
use pin_project_lite::pin_project;
pin_project! {
#[must_use = "futures do nothing unless you `.await` or poll them"]
pub struct TryAll<St, Fut, F> {
#[pin]
stream: St,
f: F,
done: bool,
#[pin]
future: Option<Fut>,
}
}
impl<St, Fut, F> fmt::Debug for TryAll<St, Fut, F>
where
St: fmt::Debug,
Fut: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("TryAll")
.field("stream", &self.stream)
.field("done", &self.done)
.field("future", &self.future)
.finish()
}
}
impl<St, Fut, F> TryAll<St, Fut, F>
where
St: TryStream,
F: FnMut(St::Ok) -> Fut,
Fut: Future<Output = bool>,
{
pub(super) fn new(stream: St, f: F) -> Self {
Self { stream, f, done: false, future: None }
}
}
impl<St, Fut, F> FusedFuture for TryAll<St, Fut, F>
where
St: TryStream,
F: FnMut(St::Ok) -> Fut,
Fut: Future<Output = bool>,
{
fn is_terminated(&self) -> bool {
self.done && self.future.is_none()
}
}
impl<St, Fut, F> Future for TryAll<St, Fut, F>
where
St: TryStream,
F: FnMut(St::Ok) -> Fut,
Fut: Future<Output = bool>,
{
type Output = Result<bool, St::Error>;
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<bool, St::Error>> {
let mut this = self.project();
Poll::Ready(loop {
if let Some(fut) = this.future.as_mut().as_pin_mut() {
let acc = ready!(fut.poll(cx));
this.future.set(None);
if !acc {
*this.done = true;
break Ok(false);
} } else if !*this.done {
match ready!(this.stream.as_mut().try_poll_next(cx)) {
Some(Ok(item)) => {
this.future.set(Some((this.f)(item)));
}
Some(Err(err)) => {
*this.done = true;
break Err(err);
}
None => {
*this.done = true;
break Ok(true);
}
}
} else {
panic!("TryAll polled after completion")
}
})
}
}