use crate::timer::clock;
use crate::timer::Delay;
use futures_core::ready;
use futures_util::future::poll_fn;
use std::future::Future;
use std::pin::Pin;
use std::task::{self, Poll};
use std::time::{Duration, Instant};
/// A stream representing notifications at fixed interval
#[derive(Debug)]
pub struct Interval {
/// Future that completes the next time the `Interval` yields a value.
delay: Delay,
/// The duration between values yielded by `Interval`.
duration: Duration,
}
impl Interval {
/// Create a new `Interval` that starts at `at` and yields every `duration`
/// interval after that.
///
/// Note that when it starts, it produces item too.
///
/// The `duration` argument must be a non-zero duration.
///
/// # Panics
///
/// This function panics if `duration` is zero.
pub fn new(at: Instant, duration: Duration) -> Interval {
assert!(
duration > Duration::new(0, 0),
"`duration` must be non-zero."
);
Interval::new_with_delay(Delay::new(at), duration)
}
/// Creates new `Interval` that yields with interval of `duration`.
///
/// The function is shortcut for `Interval::new(kayrx::timer::clock::now() + duration, duration)`.
///
/// The `duration` argument must be a non-zero duration.
///
/// # Panics
///
/// This function panics if `duration` is zero.
pub fn new_interval(duration: Duration) -> Interval {
Interval::new(clock::now() + duration, duration)
}
pub(crate) fn new_with_delay(delay: Delay, duration: Duration) -> Interval {
Interval { delay, duration }
}
#[doc(hidden)] // TODO: remove
pub fn poll_next(&mut self, cx: &mut task::Context<'_>) -> Poll<Option<Instant>> {
// Wait for the delay to be done
ready!(Pin::new(&mut self.delay).poll(cx));
// Get the `now` by looking at the `delay` deadline
let now = self.delay.deadline();
// The next interval value is `duration` after the one that just
// yielded.
let next = now + self.duration;
self.delay.reset(next);
// Return the current instant
Poll::Ready(Some(now))
}
/// Completes when the next instant in the interval has been reached.
///
/// # Examples
///
/// ```
/// use kayrx::timer::Interval;
///
/// use std::time::Duration;
///
/// #[kayrx::main]
/// async fn main() {
/// let mut interval = Interval::new_interval(Duration::from_millis(10));
///
/// interval.next().await;
/// interval.next().await;
/// interval.next().await;
///
/// // approximately 30ms have elapsed.
/// }
/// ```
#[allow(clippy::should_implement_trait)]
pub async fn next(&mut self) -> Option<Instant> {
poll_fn(|cx| self.poll_next(cx)).await
}
}
impl futures_core::FusedStream for Interval {
fn is_terminated(&self) -> bool {
false
}
}
impl futures_core::Stream for Interval {
type Item = Instant;
fn poll_next(self: Pin<&mut Self>, cx: &mut task::Context<'_>) -> Poll<Option<Self::Item>> {
Interval::poll_next(self.get_mut(), cx)
}
}