// From https://github.com/hyperium/hyper/blob/master/benches/support/tokiort.rs
use pin_project::pin_project;
use std::{
    pin::Pin,
    task::{Context, Poll},
};

#[pin_project]
#[derive(Debug)]
pub struct TokioIo<T>(#[pin] pub T);

impl<T> hyper::rt::Read for TokioIo<T>
where
    T: tokio::io::AsyncRead,
{
    fn poll_read(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        mut buf: hyper::rt::ReadBufCursor<'_>,
    ) -> Poll<Result<(), std::io::Error>> {
        let n = unsafe {
            let mut tbuf = tokio::io::ReadBuf::uninit(buf.as_mut());
            match tokio::io::AsyncRead::poll_read(self.project().0, cx, &mut tbuf) {
                Poll::Ready(Ok(())) => tbuf.filled().len(),
                other => return other,
            }
        };

        unsafe {
            buf.advance(n);
        }
        Poll::Ready(Ok(()))
    }
}

impl<T> hyper::rt::Write for TokioIo<T>
where
    T: tokio::io::AsyncWrite,
{
    fn poll_write(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        buf: &[u8],
    ) -> Poll<Result<usize, std::io::Error>> {
        tokio::io::AsyncWrite::poll_write(self.project().0, cx, buf)
    }

    fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), std::io::Error>> {
        tokio::io::AsyncWrite::poll_flush(self.project().0, cx)
    }

    fn poll_shutdown(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
    ) -> Poll<Result<(), std::io::Error>> {
        tokio::io::AsyncWrite::poll_shutdown(self.project().0, cx)
    }

    fn is_write_vectored(&self) -> bool {
        tokio::io::AsyncWrite::is_write_vectored(&self.0)
    }

    fn poll_write_vectored(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        bufs: &[std::io::IoSlice<'_>],
    ) -> Poll<Result<usize, std::io::Error>> {
        tokio::io::AsyncWrite::poll_write_vectored(self.project().0, cx, bufs)
    }
}

impl<T> tokio::io::AsyncRead for TokioIo<T>
where
    T: hyper::rt::Read,
{
    fn poll_read(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        tbuf: &mut tokio::io::ReadBuf<'_>,
    ) -> Poll<Result<(), std::io::Error>> {
        //let init = tbuf.initialized().len();
        let filled = tbuf.filled().len();
        let sub_filled = unsafe {
            let mut buf = hyper::rt::ReadBuf::uninit(tbuf.unfilled_mut());

            match hyper::rt::Read::poll_read(self.project().0, cx, buf.unfilled()) {
                Poll::Ready(Ok(())) => buf.filled().len(),
                other => return other,
            }
        };

        let n_filled = filled + sub_filled;
        // At least sub_filled bytes had to have been initialized.
        let n_init = sub_filled;
        unsafe {
            tbuf.assume_init(n_init);
            tbuf.set_filled(n_filled);
        }

        Poll::Ready(Ok(()))
    }
}

impl<T> tokio::io::AsyncWrite for TokioIo<T>
where
    T: hyper::rt::Write,
{
    fn poll_write(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        buf: &[u8],
    ) -> Poll<Result<usize, std::io::Error>> {
        hyper::rt::Write::poll_write(self.project().0, cx, buf)
    }

    fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), std::io::Error>> {
        hyper::rt::Write::poll_flush(self.project().0, cx)
    }

    fn poll_shutdown(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
    ) -> Poll<Result<(), std::io::Error>> {
        hyper::rt::Write::poll_shutdown(self.project().0, cx)
    }

    fn is_write_vectored(&self) -> bool {
        hyper::rt::Write::is_write_vectored(&self.0)
    }

    fn poll_write_vectored(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        bufs: &[std::io::IoSlice<'_>],
    ) -> Poll<Result<usize, std::io::Error>> {
        hyper::rt::Write::poll_write_vectored(self.project().0, cx, bufs)
    }
}