use super::assert_stream;

use core::pin::Pin;

use futures_core::stream::{FusedStream, Stream};

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

/// Stream for the [`repeat`] function.

#[derive(Debug, Clone)]

#[must_use = "streams do nothing unless polled"]

pub struct Repeat<T> {

    item: T,

}

/// Create a stream which produces the same item repeatedly.

///

/// The stream never terminates. Note that you likely want to avoid

/// usage of `collect` or such on the returned stream as it will exhaust

/// available memory as it tries to just fill up all RAM.

///

/// ```

/// # futures::executor::block_on(async {

/// use futures::stream::{self, StreamExt};

///

/// let stream = stream::repeat(9);

/// assert_eq!(vec![9, 9, 9], stream.take(3).collect::<Vec<i32>>().await);

/// # });

/// ```

pub fn repeat<T>(item: T) -> Repeat<T>

where

    T: Clone,

{

    assert_stream::<T, _>(Repeat { item })

}

impl<T> Unpin for Repeat<T> {}

impl<T> Stream for Repeat<T>

where

    T: Clone,

{

    type Item = T;

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

        Poll::Ready(Some(self.item.clone()))

    }

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

        (usize::max_value(), None)

    }

}

impl<T> FusedStream for Repeat<T>

where

    T: Clone,

{

    fn is_terminated(&self) -> bool {

        false

    }

}