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use std::future::Future;
use std::pin::Pin;
use std::task::{Context, Poll};
use futures_util::{ready, TryFuture};
use pin_project::pin_project;
use super::{Filter, FilterBase, Func, Internal};
use crate::reject::IsReject;
use crate::route;
#[derive(Clone, Copy, Debug)]
pub struct OrElse<T, F> {
pub(super) filter: T,
pub(super) callback: F,
}
impl<T, F> FilterBase for OrElse<T, F>
where
T: Filter,
F: Func<T::Error> + Clone + Send,
F::Output: TryFuture<Ok = T::Extract> + Send,
<F::Output as TryFuture>::Error: IsReject,
{
type Extract = <F::Output as TryFuture>::Ok;
type Error = <F::Output as TryFuture>::Error;
type Future = OrElseFuture<T, F>;
#[inline]
fn filter(&self, _: Internal) -> Self::Future {
let idx = route::with(|route| route.matched_path_index());
OrElseFuture {
state: State::First(self.filter.filter(Internal), self.callback.clone()),
original_path_index: PathIndex(idx),
}
}
}
#[allow(missing_debug_implementations)]
#[pin_project]
pub struct OrElseFuture<T: Filter, F>
where
T: Filter,
F: Func<T::Error>,
F::Output: TryFuture<Ok = T::Extract> + Send,
{
#[pin]
state: State<T, F>,
original_path_index: PathIndex,
}
#[pin_project(project = StateProj)]
enum State<T, F>
where
T: Filter,
F: Func<T::Error>,
F::Output: TryFuture<Ok = T::Extract> + Send,
{
First(#[pin] T::Future, F),
Second(#[pin] F::Output),
Done,
}
#[derive(Copy, Clone)]
struct PathIndex(usize);
impl PathIndex {
fn reset_path(&self) {
route::with(|route| route.reset_matched_path_index(self.0));
}
}
impl<T, F> Future for OrElseFuture<T, F>
where
T: Filter,
F: Func<T::Error>,
F::Output: TryFuture<Ok = T::Extract> + Send,
{
type Output = Result<<F::Output as TryFuture>::Ok, <F::Output as TryFuture>::Error>;
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
loop {
let pin = self.as_mut().project();
let (err, second) = match pin.state.project() {
StateProj::First(first, second) => match ready!(first.try_poll(cx)) {
Ok(ex) => return Poll::Ready(Ok(ex)),
Err(err) => (err, second),
},
StateProj::Second(second) => {
let ex2 = ready!(second.try_poll(cx));
self.set(OrElseFuture {
state: State::Done,
..*self
});
return Poll::Ready(ex2);
}
StateProj::Done => panic!("polled after complete"),
};
pin.original_path_index.reset_path();
let fut2 = second.call(err);
self.set(OrElseFuture {
state: State::Second(fut2),
..*self
});
}
}
}