use crate::io::AsyncRead;

use futures_core::future::Future;

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

use std::io;

use std::pin::Pin;

/// Future for the [`read`](super::AsyncReadExt::read) method.

#[derive(Debug)]

#[must_use = "futures do nothing unless you `.await` or poll them"]

pub struct Read<'a, R: ?Sized> {

    reader: &'a mut R,

    buf: &'a mut [u8],

}

impl<R: ?Sized + Unpin> Unpin for Read<'_, R> {}

impl<'a, R: AsyncRead + ?Sized + Unpin> Read<'a, R> {

    pub(super) fn new(reader: &'a mut R, buf: &'a mut [u8]) -> Self {

        Self { reader, buf }

    }

}

impl<R: AsyncRead + ?Sized + Unpin> Future for Read<'_, R> {

    type Output = io::Result<usize>;

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

        let this = &mut *self;

        Pin::new(&mut this.reader).poll_read(cx, this.buf)

    }

}