async-iter-ext 0.1.0

Async iterator methods and async methods for option and result.
Documentation 
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use std::{
  fmt::{Debug, Formatter},
  pin::Pin,
  task::{Context, Poll},
  vec::IntoIter,
};

use crate::iter::{
  AsyncIterator,
  sync_iter::{PollSyncIter, SyncIter},
};

#[derive(Clone)]
#[must_use = "async iterator combinators are lazy and do nothing unless consumed"]
pub struct AsyncFilter<I, F> {
  pub(crate) iter: I,
  pub(crate) f: F,
}

impl<I, F, Fut> AsyncIterator for AsyncFilter<I, F>
where
  I: AsyncIterator,
  F: FnMut(I::Item) -> Fut,
  Fut: Future<Output = bool>,
  I::Item: Clone,
{
  type Item = I::Item;

  async fn next_async(&mut self) -> Option<Self::Item> {
    if let Some(next) = self.iter.next_async().await {
      (self.f)(next.clone()).await.then_some(next)
    } else {
      None
    }
  }

  fn async_size_hint(&self) -> (usize, Option<usize>) {
    self.iter.async_size_hint()
  }
}

impl<I, F, Fut> PollSyncIter for AsyncFilter<I, F>
where
  I: AsyncIterator,
  F: FnMut(I::Item) -> Fut,
  Fut: Future<Output = bool>,
  I::Item: Clone,
{
}

impl<I, F, Fut> Future for AsyncFilter<I, F>
where
  I: AsyncIterator + Unpin,
  F: FnMut(I::Item) -> Fut + Unpin + Send,
  Fut: Future<Output = bool> + Send,
  I::Item: Clone,
{
  type Output = SyncIter<IntoIter<I::Item>>;

  fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
    Self::poll_sync_iter(self, cx)
  }
}

impl<I, F> Debug for AsyncFilter<I, F>
where
  I: AsyncIterator + Debug,
{
  fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
    f.debug_struct("AsyncFilter").field("iter", &self.iter).finish()
  }
}