use axum::{
    extract::connect_info::{self, ConnectInfo},
    prelude::*,
};
use futures::ready;
use http::{Method, StatusCode, Uri};
use hyper::{
    client::connect::{Connected, Connection},
    server::accept::Accept,
};
use std::{
    io,
    path::PathBuf,
    pin::Pin,
    sync::Arc,
    task::{Context, Poll},
};
use tokio::net::{unix::UCred, UnixListener};
use tokio::{
    io::{AsyncRead, AsyncWrite},
    net::UnixStream,
};
use tower::BoxError;

#[cfg(not(unix))]
fn main() {
    println!("This example requires unix")
}

#[cfg(unix)]
#[tokio::main]
async fn main() {
    let path = PathBuf::from("/tmp/axum/helloworld");

    let _ = tokio::fs::remove_file(&path).await;
    tokio::fs::create_dir_all(path.parent().unwrap())
        .await
        .unwrap();

    let uds = UnixListener::bind(path.clone()).unwrap();
    tokio::spawn(async {
        let app = route("/", get(handler));

        hyper::Server::builder(ServerAccept { uds })
            .serve(app.into_make_service_with_connect_info::<UdsConnectInfo, _>())
            .await
            .unwrap();
    });

    let connector = tower::service_fn(move |_: Uri| {
        let path = path.clone();
        Box::pin(async move {
            let stream = UnixStream::connect(path).await?;
            Ok::<_, io::Error>(ClientConnection { stream })
        })
    });
    let client = hyper::Client::builder().build(connector);

    let request = Request::builder()
        .method(Method::GET)
        .uri("http://uri-doesnt-matter.com")
        .body(Body::empty())
        .unwrap();

    let response = client.request(request).await.unwrap();

    assert_eq!(response.status(), StatusCode::OK);

    let body = hyper::body::to_bytes(response.into_body()).await.unwrap();
    let body = String::from_utf8(body.to_vec()).unwrap();
    assert_eq!(body, "Hello, World!");
}

async fn handler(ConnectInfo(info): ConnectInfo<UdsConnectInfo>) -> &'static str {
    println!("new connection from `{:?}`", info);

    "Hello, World!"
}

struct ServerAccept {
    uds: UnixListener,
}

impl Accept for ServerAccept {
    type Conn = UnixStream;
    type Error = BoxError;

    fn poll_accept(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
    ) -> Poll<Option<Result<Self::Conn, Self::Error>>> {
        let (stream, _addr) = ready!(self.uds.poll_accept(cx))?;
        Poll::Ready(Some(Ok(stream)))
    }
}

struct ClientConnection {
    stream: UnixStream,
}

impl AsyncWrite for ClientConnection {
    fn poll_write(
        mut self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        buf: &[u8],
    ) -> Poll<Result<usize, io::Error>> {
        Pin::new(&mut self.stream).poll_write(cx, buf)
    }

    fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
        Pin::new(&mut self.stream).poll_flush(cx)
    }

    fn poll_shutdown(
        mut self: Pin<&mut Self>,
        cx: &mut Context<'_>,
    ) -> Poll<Result<(), io::Error>> {
        Pin::new(&mut self.stream).poll_shutdown(cx)
    }
}

impl AsyncRead for ClientConnection {
    fn poll_read(
        mut self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        buf: &mut tokio::io::ReadBuf<'_>,
    ) -> Poll<io::Result<()>> {
        Pin::new(&mut self.stream).poll_read(cx, buf)
    }
}

impl Connection for ClientConnection {
    fn connected(&self) -> Connected {
        Connected::new()
    }
}

#[derive(Clone, Debug)]
struct UdsConnectInfo {
    peer_addr: Arc<tokio::net::unix::SocketAddr>,
    peer_cred: UCred,
}

impl connect_info::Connected<&UnixStream> for UdsConnectInfo {
    type ConnectInfo = Self;

    fn connect_info(target: &UnixStream) -> Self::ConnectInfo {
        let peer_addr = target.peer_addr().unwrap();
        let peer_cred = target.peer_cred().unwrap();

        Self {
            peer_addr: Arc::new(peer_addr),
            peer_cred,
        }
    }
}
