use std::{
pin::Pin,
task::{Context, Poll},
};
use futures_core::ready;
use pin_project_lite::pin_project;
use crate::{
actor::Actor,
fut::{ActorFuture, ActorStream},
};
pin_project! {
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct Then<S, F, Fut> {
#[pin]
stream: S,
#[pin]
future: Option<Fut>,
f: F,
}
}
pub(super) fn new<S, A, F, Fut>(stream: S, f: F) -> Then<S, F, Fut>
where
S: ActorStream<A>,
A: Actor,
F: FnMut(S::Item, &mut A, &mut A::Context) -> Fut,
Fut: ActorFuture<A>,
{
Then {
stream,
f,
future: None,
}
}
impl<S, A, F, Fut> ActorStream<A> for Then<S, F, Fut>
where
S: ActorStream<A>,
A: Actor,
F: FnMut(S::Item, &mut A, &mut A::Context) -> Fut,
Fut: ActorFuture<A>,
{
type Item = Fut::Output;
fn poll_next(
self: Pin<&mut Self>,
act: &mut A,
ctx: &mut A::Context,
task: &mut Context<'_>,
) -> Poll<Option<Self::Item>> {
let mut this = self.project();
Poll::Ready(loop {
if let Some(fut) = this.future.as_mut().as_pin_mut() {
let item = ready!(fut.poll(act, ctx, task));
this.future.set(None);
break Some(item);
} else if let Some(item) = ready!(this.stream.as_mut().poll_next(act, ctx, task)) {
this.future.set(Some((this.f)(item, act, ctx)));
} else {
break None;
}
})
}
}