use core::pin::Pin;
use core::task::{Context, Poll};
use pin_project_lite::pin_project;
use crate::stream::Stream;
pin_project! {
#[derive(Debug)]
pub struct FilterMap<S, F> {
#[pin]
stream: S,
f: F,
}
}
impl<S, F> FilterMap<S, F> {
pub(crate) fn new(stream: S, f: F) -> Self {
Self { stream, f }
}
}
impl<S, F, B> Stream for FilterMap<S, F>
where
S: Stream,
F: FnMut(S::Item) -> Option<B>,
{
type Item = B;
fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
let this = self.project();
let next = futures_core::ready!(this.stream.poll_next(cx));
match next {
Some(v) => match (this.f)(v) {
Some(b) => Poll::Ready(Some(b)),
None => {
cx.waker().wake_by_ref();
Poll::Pending
}
},
None => Poll::Ready(None),
}
}
}