use super::{error::Closed, message};
use futures_core::ready;
use pin_project_lite::pin_project;
use std::{
future::Future,
pin::Pin,
task::{Context, Poll},
};
pin_project! {
#[derive(Debug)]
pub struct ResponseFuture<T> {
#[pin]
state: ResponseState<T>,
}
}
pin_project! {
#[project = ResponseStateProj]
#[derive(Debug)]
enum ResponseState<T> {
Failed {
error: Option<crate::BoxError>,
},
Rx {
#[pin]
rx: message::Rx<T>,
},
Poll {
#[pin]
fut: T,
},
}
}
impl<T> ResponseFuture<T> {
pub(crate) fn new(rx: message::Rx<T>) -> Self {
ResponseFuture {
state: ResponseState::Rx { rx },
}
}
pub(crate) fn failed(err: crate::BoxError) -> Self {
ResponseFuture {
state: ResponseState::Failed { error: Some(err) },
}
}
}
impl<F, T, E> Future for ResponseFuture<F>
where
F: Future<Output = Result<T, E>>,
E: Into<crate::BoxError>,
{
type Output = Result<T, crate::BoxError>;
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
let mut this = self.project();
loop {
match this.state.as_mut().project() {
ResponseStateProj::Failed { error } => {
return Poll::Ready(Err(error.take().expect("polled after error")));
}
ResponseStateProj::Rx { rx } => match ready!(rx.poll(cx)) {
Ok(Ok(fut)) => this.state.set(ResponseState::Poll { fut }),
Ok(Err(e)) => return Poll::Ready(Err(e.into())),
Err(_) => return Poll::Ready(Err(Closed::new().into())),
},
ResponseStateProj::Poll { fut } => return fut.poll(cx).map_err(Into::into),
}
}
}
}