use super::read_line::read_line_internal;

use futures_core::ready;

use futures_core::stream::Stream;

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

use futures_io::AsyncBufRead;

use pin_project_lite::pin_project;

use std::io;

use std::mem;

use std::pin::Pin;

pin_project! {

    /// Stream for the [`lines`](super::AsyncBufReadExt::lines) method.

    #[derive(Debug)]

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

    pub struct Lines<R> {

        #[pin]

        reader: R,

        buf: String,

        bytes: Vec<u8>,

        read: usize,

    }

}

impl<R: AsyncBufRead> Lines<R> {

    pub(super) fn new(reader: R) -> Self {

        Self { reader, buf: String::new(), bytes: Vec::new(), read: 0 }

    }

}

impl<R: AsyncBufRead> Stream for Lines<R> {

    type Item = io::Result<String>;

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

        let this = self.project();

        let n = ready!(read_line_internal(this.reader, cx, this.buf, this.bytes, this.read))?;

        if n == 0 && this.buf.is_empty() {

            return Poll::Ready(None);

        }

        if this.buf.ends_with('\n') {

            this.buf.pop();

            if this.buf.ends_with('\r') {

                this.buf.pop();

            }

        }

        Poll::Ready(Some(Ok(mem::take(this.buf))))

    }

}