use crate::Stream;

use futures_core::stream::FusedStream;

use std::pin::Pin;

use std::task::{Context, Poll};

use tokio::time::{Instant, Interval};

/// A wrapper around [`Interval`] that implements [`Stream`].

///

/// # Example

///

/// ```

/// use tokio::time::{Duration, Instant, interval};

/// use tokio_stream::wrappers::IntervalStream;

/// use tokio_stream::StreamExt;

///

/// # #[tokio::main(flavor = "current_thread")]

/// # async fn main() {

/// let start = Instant::now();

/// let interval = interval(Duration::from_millis(10));

/// let mut stream = IntervalStream::new(interval);

/// for _ in 0..3 {

///     if let Some(instant) = stream.next().await {

///         println!("elapsed: {:.1?}", instant.duration_since(start));

///     }

/// }

/// # }

/// ```

///

/// [`Interval`]: struct@tokio::time::Interval

/// [`Stream`]: trait@crate::Stream

#[derive(Debug)]

#[cfg_attr(docsrs, doc(cfg(feature = "time")))]

pub struct IntervalStream {

    inner: Interval,

}

impl IntervalStream {

    /// Create a new `IntervalStream`.

    pub fn new(interval: Interval) -> Self {

        Self { inner: interval }

    }

    /// Get back the inner `Interval`.

    pub fn into_inner(self) -> Interval {

        self.inner

    }

}

impl Stream for IntervalStream {

    type Item = Instant;

    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Instant>> {

        self.inner.poll_tick(cx).map(Some)

    }

    fn size_hint(&self) -> (usize, Option<usize>) {

        (usize::MAX, None)

    }

}

impl FusedStream for IntervalStream {

    fn is_terminated(&self) -> bool {

        false

    }

}

impl AsRef<Interval> for IntervalStream {

    fn as_ref(&self) -> &Interval {

        &self.inner

    }

}

impl AsMut<Interval> for IntervalStream {

    fn as_mut(&mut self) -> &mut Interval {

        &mut self.inner

    }

}