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use crate::channel::Parker;
use crate::future::{IntoFuture, Timer};
use futures_core::Stream;
use super::{Buffer, Debounce, Delay, IntoStream, Park, Sample, Throttle, Timeout};
/// Extend `Stream` with time-based operations.
pub trait StreamExt: Stream {
/// Yield the last item received at the end of each interval.
///
/// If no items have been received during an interval, the stream will not
/// yield any items. In addition to using a time-based interval, this method can take any
/// stream as a source. This enables throttling based on alternative event
/// sources, such as variable-rate timers.
///
/// See also [`throttle()`] and [`debounce()`].
///
/// [`throttle()`]: StreamExt::throttle
/// [`debounce()`]: `StreamExt::debounce`
///
/// # Data Loss
///
/// This method will discard data between intervals. Though the
/// discarded items will have their destuctors run, __using this method
/// incorrectly may lead to unintended data loss__. This method is best used
/// to reduce the number of _duplicate_ items after the first has been
/// received, such as repeated mouse clicks or key presses. This method may
/// lead to unintended data loss when used to discard _unique_ items, such
/// as network request.
///
/// # Example
///
/// ```
/// use futures_lite::prelude::*;
/// use futures_time::prelude::*;
/// use futures_time::time::{Instant, Duration};
/// use futures_time::stream;
///
/// async_io::block_on(async {
/// let mut counter = 0;
/// stream::interval(Duration::from_millis(100))
/// .take(4)
/// .sample(Duration::from_millis(200))
/// .for_each(|_| counter += 1)
/// .await;
///
/// assert_eq!(counter, 2);
/// })
/// ```
fn sample<I>(self, interval: I) -> Sample<Self, I::IntoStream>
where
Self: Sized,
I: IntoStream,
{
Sample::new(self, interval.into_stream())
}
/// Group items into vectors which are yielded at every interval.
///
/// In addition to using a time source as a deadline, any stream can be used as a
/// deadline too. This enables more interesting buffer strategies to be
/// built on top of this primitive.
///
/// # Future Improvements
///
/// - Lending iterators would allow for internal reusing of the buffer. Though different from
/// `Iterator::windows`, it could be more efficient.
/// - Contexts/capabilities would enable custom allocators to be used.
///
/// # Example
///
/// ```
/// use futures_lite::prelude::*;
/// use futures_time::prelude::*;
/// use futures_time::time::{Instant, Duration};
/// use futures_time::stream;
///
/// async_io::block_on(async {
/// let mut counter = 0;
/// stream::interval(Duration::from_millis(5))
/// .take(10)
/// .buffer(Duration::from_millis(20))
/// .for_each(|buf| counter += buf.len())
/// .await;
///
/// assert_eq!(counter, 10);
/// })
/// ```
fn buffer<I>(self, interval: I) -> Buffer<Self, I::IntoStream>
where
Self: Sized,
I: IntoStream,
{
Buffer::new(self, interval.into_stream())
}
/// Yield the last item received at the end of a window which resets with
/// each item received.
///
/// Every time an item is yielded by the underlying stream, the window is
/// reset. Once the window expires, the last item seen will be yielded. This
/// means that in order to yield an item, no items must be received for the
/// entire window, or else the window will reset.
///
/// This method is useful to perform actions at the end of bursts of events,
/// where performing that same action on _every_ event might not be
/// economical.
///
/// See also [`sample()`] and [`throttle()`].
///
/// [`sample()`]: `StreamExt::sample`
/// [`throttle()`]: `StreamExt::throttle`
///
/// # Example
///
/// ```
/// use futures_lite::prelude::*;
/// use futures_time::prelude::*;
/// use futures_time::time::{Instant, Duration};
/// use futures_time::stream;
///
/// async_io::block_on(async {
/// let mut counter = 0;
/// stream::interval(Duration::from_millis(10))
/// .take(10)
/// .debounce(Duration::from_millis(20)) // the window is greater than the interval
/// .for_each(|_| counter += 1)
/// .await;
///
/// assert_eq!(counter, 1); // so only the last item is received
/// })
/// ```
fn debounce<D>(self, window: D) -> Debounce<Self, D::IntoFuture>
where
Self: Sized,
D: IntoFuture,
D::IntoFuture: Timer,
{
Debounce::new(self, window.into_future())
}
/// Delay the yielding of items from the stream until the given deadline.
///
/// The underlying stream will not be polled until the deadline has expired. In addition
/// to using a time source as a deadline, any future can be used as a
/// deadline too. When used in combination with a multi-consumer channel,
/// this method can be used to synchronize the start of multiple streams and futures.
///
/// # Example
///
/// ```
/// use futures_lite::prelude::*;
/// use futures_time::prelude::*;
/// use futures_time::time::{Instant, Duration};
/// use futures_lite::stream;
///
/// async_io::block_on(async {
/// let now = Instant::now();
/// let delay = Duration::from_millis(100);
/// let _ = stream::once("meow").delay(delay).next().await;
/// assert!(now.elapsed() >= *delay);
/// });
/// ```
fn delay<D>(self, deadline: D) -> Delay<Self, D::IntoFuture>
where
Self: Sized,
D: IntoFuture,
{
Delay::new(self, deadline.into_future())
}
/// Suspend or resume execution of a stream.
///
/// When this method is called the execution of the stream will be put into
/// a suspended state until the channel returns `Parker::Unpark` or the
/// channel's senders are dropped. The underlying stream will not be polled
/// while the it is paused.
fn park<I>(self, interval: I) -> Park<Self, I::IntoStream>
where
Self: Sized,
I: IntoStream<Item = Parker>,
{
Park::new(self, interval.into_stream())
}
/// Yield an item, then ignore subsequent items for a duration.
///
/// In addition to using a time-based interval, this method can take any
/// stream as a source. This enables throttling based on alternative event
/// sources, such as variable-rate timers.
///
/// See also [`sample()`] and [`debounce()`].
///
/// [`sample()`]: `StreamExt::sample`
/// [`debounce()`]: `StreamExt::debounce`
///
/// # Data Loss
///
/// This method will discard data between intervals. Though the
/// discarded items will have their destuctors run, __using this method
/// incorrectly may lead to unintended data loss__. This method is best used
/// to reduce the number of _duplicate_ items after the first has been
/// received, such as repeated mouse clicks or key presses. This method may
/// lead to unintended data loss when used to discard _unique_ items, such
/// as network request.
///
/// # Examples
///
/// ```
/// use futures_lite::prelude::*;
/// use futures_time::prelude::*;
/// use futures_time::time::Duration;
/// use futures_time::stream;
///
/// async_io::block_on(async {
/// let mut counter = 0;
/// stream::interval(Duration::from_millis(100)) // Yield an item every 100ms
/// .take(4) // Stop after 4 items
/// .throttle(Duration::from_millis(300)) // Only let an item through every 300ms
/// .for_each(|_| counter += 1) // Increment a counter for each item
/// .await;
///
/// assert_eq!(counter, 2);
/// })
/// ```
fn throttle<I>(self, interval: I) -> Throttle<Self, I::IntoStream>
where
Self: Sized,
I: IntoStream,
{
Throttle::new(self, interval.into_stream())
}
/// Return an error if a stream does not yield an item within a given time
/// span.
///
/// Typically timeouts are, as the name implies, based on _time_. However
/// this method can time out based on any future. This can be useful in
/// combination with channels, as it allows (long-lived) streams to be
/// cancelled based on some external event.
///
/// When a timeout is returned, the stream will be dropped and destructors
/// will be run.
///
/// # Example
///
/// ```
/// use futures_lite::prelude::*;
/// use futures_time::prelude::*;
/// use futures_time::time::{Instant, Duration};
/// use futures_lite::stream;
/// use std::io;
///
/// async_io::block_on(async {
/// let res = stream::once("meow")
/// .delay(Duration::from_millis(100)) // longer delay
/// .timeout(Duration::from_millis(50)) // shorter timeout
/// .next()
/// .await;
/// assert_eq!(res.unwrap().unwrap_err().kind(), io::ErrorKind::TimedOut); // error
///
/// let res = stream::once("meow")
/// .delay(Duration::from_millis(50)) // shorter delay
/// .timeout(Duration::from_millis(100)) // longer timeout
/// .next()
/// .await;
/// assert_eq!(res.unwrap().unwrap(), "meow"); // success
/// });
/// ```
fn timeout<D>(self, deadline: D) -> Timeout<Self, D::IntoFuture>
where
Self: Sized,
D: IntoFuture,
D::IntoFuture: Timer,
{
Timeout::new(self, deadline.into_future())
}
}
impl<S> StreamExt for S where S: Stream {}