use futures::executor::block_on;
use futures::future::{Future, FutureExt};
use futures::io::{AsyncBufReadExt, AsyncRead, Cursor};
use futures::stream::{self, StreamExt, TryStreamExt};
use futures::task::Poll;
use futures_test::io::AsyncReadTestExt;
use futures_test::task::noop_context;

fn run<F: Future + Unpin>(mut f: F) -> F::Output {
    let mut cx = noop_context();
    loop {
        if let Poll::Ready(x) = f.poll_unpin(&mut cx) {
            return x;
        }
    }
}

macro_rules! block_on_next {
    ($expr:expr) => {
        block_on($expr.next()).unwrap().unwrap()
    };
}

macro_rules! run_next {
    ($expr:expr) => {
        run($expr.next()).unwrap().unwrap()
    };
}

struct IOErrorRead(bool);

impl AsyncRead for IOErrorRead {
    fn poll_read(
        mut self: std::pin::Pin<&mut Self>,
        _cx: &mut std::task::Context<'_>,
        b: &mut [u8],
    ) -> Poll<std::io::Result<usize>> {
        if self.0 {
            Poll::Ready(Err(std::io::ErrorKind::InvalidInput.into()))
        } else {
            self.0 = true;
            b[..16].fill(b'x');
            Ok(16).into()
        }
    }
}

#[test]
fn lines() {
    let buf = Cursor::new(&b"12\r"[..]);
    let mut s = buf.lines();
    assert_eq!(block_on_next!(s), "12\r".to_string());
    assert!(block_on(s.next()).is_none());

    let buf = Cursor::new(&b"12\r\n\n"[..]);
    let mut s = buf.lines();
    assert_eq!(block_on_next!(s), "12".to_string());
    assert_eq!(block_on_next!(s), "".to_string());
    assert!(block_on(s.next()).is_none());
}

#[test]
fn maybe_pending() {
    let buf =
        stream::iter(vec![&b"12"[..], &b"\r"[..]]).map(Ok).into_async_read().interleave_pending();
    let mut s = buf.lines();
    assert_eq!(run_next!(s), "12\r".to_string());
    assert!(run(s.next()).is_none());

    let buf = stream::iter(vec![&b"12"[..], &b"\r\n"[..], &b"\n"[..]])
        .map(Ok)
        .into_async_read()
        .interleave_pending();
    let mut s = buf.lines();
    assert_eq!(run_next!(s), "12".to_string());
    assert_eq!(run_next!(s), "".to_string());
    assert!(run(s.next()).is_none());
}

#[test]
fn issue2862() {
    let mut lines = futures::io::BufReader::new(IOErrorRead(false)).lines();
    assert!(block_on(lines.next()).unwrap().is_err())
}