From 9e6336318725bfd26ebdc6cfe009835db87d3476 Mon Sep 17 00:00:00 2001
From: David Pedersen <david.pdrsn@gmail.com>
Date: Fri, 10 Nov 2023 13:47:20 +0100
Subject: [PATCH] feat(service): add adapter for tower services

---
 examples/tower_server.rs | 27 ++++++++++++++++
 src/lib.rs               |  1 +
 src/server/conn/auto.rs  | 68 ++++++++++++++++++++++++++++++++++++++++
 src/service.rs           | 62 ++++++++++++++++++++++++++++++++++++
 4 files changed, 158 insertions(+)
 create mode 100644 examples/tower_server.rs
 create mode 100644 src/service.rs

diff --git a/examples/tower_server.rs b/examples/tower_server.rs
new file mode 100644
index 0000000..3caf26d
--- /dev/null
+++ b/examples/tower_server.rs
@@ -0,0 +1,27 @@
+use bytes::Bytes;
+use http::{Request, Response};
+use http_body_util::Full;
+use hyper::body::Incoming;
+use hyper_util::{rt::TokioExecutor, server::conn::auto::Builder};
+use tokio::net::TcpListener;
+use tower::BoxError;
+
+async fn handle(_request: Request<Incoming>) -> Result<Response<Full<Bytes>>, BoxError> {
+    Ok(Response::new(Full::from("Hello, World!")))
+}
+
+#[tokio::main(flavor = "current_thread")]
+async fn main() {
+    let tower_service = tower::service_fn(handle);
+
+    let listener = TcpListener::bind("0.0.0.0:3000").await.unwrap();
+    loop {
+        let (tcp_stream, _remote_addr) = listener.accept().await.unwrap();
+        if let Err(err) = Builder::new(TokioExecutor::new())
+            .serve_connection_with_upgrades_tower(tcp_stream, tower_service)
+            .await
+        {
+            eprintln!("failed to serve connection: {err:#}");
+        }
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 85f3d3b..54b5101 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -8,5 +8,6 @@ pub mod client;
 mod common;
 pub mod rt;
 pub mod server;
+pub mod service;
 
 mod error;
diff --git a/src/server/conn/auto.rs b/src/server/conn/auto.rs
index f10450e..63b1199 100644
--- a/src/server/conn/auto.rs
+++ b/src/server/conn/auto.rs
@@ -20,6 +20,7 @@ use hyper::{
 use pin_project_lite::pin_project;
 use tokio::io::{AsyncRead, AsyncWrite, ReadBuf};
 
+use crate::service::{TowerToHyperService, TowerToHyperServiceFuture};
 use crate::{common::rewind::Rewind, rt::TokioIo};
 
 type Result<T> = std::result::Result<T, Box<dyn std::error::Error + Send + Sync>>;
@@ -87,6 +88,36 @@ impl<E> Builder<E> {
         Ok(())
     }
 
+    /// Bind a connection together with a [`tower::Service`].
+    pub async fn serve_connection_tower<I, S, B>(&self, io: I, service: S) -> Result<()>
+    where
+        S: tower::Service<Request<Incoming>, Response = Response<B>> + Clone + Send,
+        S::Future: 'static,
+        S::Error: Into<Box<dyn StdError + Send + Sync>>,
+        B: Body + Send + 'static,
+        B::Data: Send,
+        B::Error: Into<Box<dyn StdError + Send + Sync>>,
+        I: AsyncRead + AsyncWrite + Unpin + 'static,
+        E: Http2ConnExec<TowerToHyperServiceFuture<S, Request<Incoming>>, B>,
+    {
+        let (version, io) = read_version(io).await?;
+        let io = TokioIo::new(io);
+        match version {
+            Version::H1 => {
+                self.http1
+                    .serve_connection(io, TowerToHyperService::new(service))
+                    .await?
+            }
+            Version::H2 => {
+                self.http2
+                    .serve_connection(io, TowerToHyperService::new(service))
+                    .await?
+            }
+        }
+
+        Ok(())
+    }
+
     /// Bind a connection together with a [`Service`], with the ability to
     /// handle HTTP upgrades. This requires that the IO object implements
     /// `Send`.
@@ -115,6 +146,43 @@ impl<E> Builder<E> {
 
         Ok(())
     }
+
+    /// Bind a connection together with a [`tower::Service`], with the ability to
+    /// handle HTTP upgrades. This requires that the IO object implements
+    /// `Send`.
+    pub async fn serve_connection_with_upgrades_tower<I, S, B>(
+        &self,
+        io: I,
+        service: S,
+    ) -> Result<()>
+    where
+        S: tower::Service<Request<Incoming>, Response = Response<B>> + Clone + Send,
+        S::Future: 'static,
+        S::Error: Into<Box<dyn StdError + Send + Sync>>,
+        B: Body + Send + 'static,
+        B::Data: Send,
+        B::Error: Into<Box<dyn StdError + Send + Sync>>,
+        I: AsyncRead + AsyncWrite + Unpin + Send + 'static,
+        E: Http2ConnExec<TowerToHyperServiceFuture<S, Request<Incoming>>, B>,
+    {
+        let (version, io) = read_version(io).await?;
+        let io = TokioIo::new(io);
+        match version {
+            Version::H1 => {
+                self.http1
+                    .serve_connection(io, TowerToHyperService::new(service))
+                    .with_upgrades()
+                    .await?
+            }
+            Version::H2 => {
+                self.http2
+                    .serve_connection(io, TowerToHyperService::new(service))
+                    .await?
+            }
+        }
+
+        Ok(())
+    }
 }
 #[derive(Copy, Clone)]
 enum Version {
diff --git a/src/service.rs b/src/service.rs
new file mode 100644
index 0000000..5b61b3c
--- /dev/null
+++ b/src/service.rs
@@ -0,0 +1,62 @@
+//! Service utilities.
+
+use pin_project_lite::pin_project;
+use std::{
+    future::Future,
+    pin::Pin,
+    task::{Context, Poll},
+};
+use tower::{util::Oneshot, ServiceExt};
+
+/// A tower service converted into a hyper service.
+#[derive(Debug, Copy, Clone)]
+pub struct TowerToHyperService<S> {
+    service: S,
+}
+
+impl<S> TowerToHyperService<S> {
+    /// Create a new `TowerToHyperService` from a tower service.
+    pub fn new(tower_service: S) -> Self {
+        Self {
+            service: tower_service,
+        }
+    }
+}
+
+impl<S, R> hyper::service::Service<R> for TowerToHyperService<S>
+where
+    S: tower::Service<R> + Clone,
+{
+    type Response = S::Response;
+    type Error = S::Error;
+    type Future = TowerToHyperServiceFuture<S, R>;
+
+    fn call(&self, req: R) -> Self::Future {
+        TowerToHyperServiceFuture {
+            future: self.service.clone().oneshot(req),
+        }
+    }
+}
+
+pin_project! {
+    /// Response future for [`TowerToHyperService`].
+    pub struct TowerToHyperServiceFuture<S, R>
+    where
+        S: tower::Service<R>,
+    {
+        #[pin]
+        future: Oneshot<S, R>,
+    }
+}
+
+impl<S, R> Future for TowerToHyperServiceFuture<S, R>
+where
+    S: tower::Service<R>,
+{
+    type Output = Result<S::Response, S::Error>;
+
+    #[inline]
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        self.project().future.poll(cx)
+    }
+}