Add new service builder machinery (#1679)

* Add protocol specific `FromRequest` and `FromParts`.

* Add `OperationShape` trait to model Smithy operations.

* Add `Handler` and `OperationService` traits.

* Add `Upgrade` `Service` and `UpgradeLayer` `Layer`.

rust-runtime/aws-smithy-http-server/src/extension.rs

@@ -50,9 +50,14 @@
 
 use std::ops::Deref;
 
+use http::StatusCode;
 use thiserror::Error;
 
-use crate::request::RequestParts;
+use crate::{
+    body::{empty, BoxBody},
+    request::{FromParts, RequestParts},
+    response::IntoResponse,
+};
 
 /// Extension type used to store information about Smithy operations in HTTP responses.
 /// This extension type is set when it has been correctly determined that the request should be
@@ -165,6 +170,30 @@ impl<T> Deref for Extension<T> {
     }
 }
 
+/// The extension has not been added to the [`Request`](http::Request) or has been previously removed.
+#[derive(Debug, Error)]
+#[error("the `Extension` is not present in the `http::Request`")]
+pub struct MissingExtension;
+
+impl<Protocol> IntoResponse<Protocol> for MissingExtension {
+    fn into_response(self) -> http::Response<BoxBody> {
+        let mut response = http::Response::new(empty());
+        *response.status_mut() = StatusCode::INTERNAL_SERVER_ERROR;
+        response
+    }
+}
+
+impl<Protocol, T> FromParts<Protocol> for Extension<T>
+where
+    T: Clone + Send + Sync + 'static,
+{
+    type Rejection = MissingExtension;
+
+    fn from_parts(parts: &mut http::request::Parts) -> Result<Self, Self::Rejection> {
+        parts.extensions.remove::<T>().map(Extension).ok_or(MissingExtension)
+    }
+}
+
 /// Extract an [`Extension`] from a request.
 /// This is essentially the implementation of `FromRequest` for `Extension`, but with a
 /// protocol-agnostic rejection type. The actual code-generated implementation simply delegates to

rust-runtime/aws-smithy-http-server/src/lib.rs

@@ -16,6 +16,8 @@ pub mod extension;
 #[doc(hidden)]
 pub mod logging;
 #[doc(hidden)]
+pub mod operation;
+#[doc(hidden)]
 pub mod protocols;
 #[doc(hidden)]
 pub mod rejection;

rust-runtime/aws-smithy-http-server/src/operation/handler.rs

@@ -0,0 +1,153 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+use std::{
+    convert::Infallible,
+    future::Future,
+    marker::PhantomData,
+    task::{Context, Poll},
+};
+
+use futures_util::{
+    future::{Map, MapErr},
+    FutureExt, TryFutureExt,
+};
+use tower::Service;
+
+use super::{OperationError, OperationShape};
+
+/// A utility trait used to provide an even interface for all operation handlers.
+pub trait Handler<Op, Exts>
+where
+    Op: OperationShape,
+{
+    type Future: Future<Output = Result<Op::Output, Op::Error>>;
+
+    fn call(&mut self, input: Op::Input, exts: Exts) -> Self::Future;
+}
+
+/// A utility trait used to provide an even interface over return types `Result<Ok, Error>`/`Ok`.
+trait IntoResult<Ok, Error> {
+    fn into_result(self) -> Result<Ok, Error>;
+}
+
+// We can convert from `Result<Ok, Error>` to `Result<Ok, Error>`.
+impl<Ok, Error> IntoResult<Ok, Error> for Result<Ok, Error> {
+    fn into_result(self) -> Result<Ok, Error> {
+        self
+    }
+}
+
+// We can convert from `T` to `Result<T, Infallible>`.
+impl<Ok> IntoResult<Ok, Infallible> for Ok {
+    fn into_result(self) -> Result<Ok, Infallible> {
+        Ok(self)
+    }
+}
+
+// fn(Input) -> Output
+impl<Op, F, Fut> Handler<Op, ()> for F
+where
+    Op: OperationShape,
+    F: Fn(Op::Input) -> Fut,
+    Fut: Future,
+    Fut::Output: IntoResult<Op::Output, Op::Error>,
+{
+    type Future = Map<Fut, fn(Fut::Output) -> Result<Op::Output, Op::Error>>;
+
+    fn call(&mut self, input: Op::Input, _exts: ()) -> Self::Future {
+        (self)(input).map(IntoResult::into_result)
+    }
+}
+
+// fn(Input, Ext0) -> Output
+impl<Op, F, Fut, Ext0> Handler<Op, (Ext0,)> for F
+where
+    Op: OperationShape,
+    F: Fn(Op::Input, Ext0) -> Fut,
+    Fut: Future,
+    Fut::Output: IntoResult<Op::Output, Op::Error>,
+{
+    type Future = Map<Fut, fn(Fut::Output) -> Result<Op::Output, Op::Error>>;
+
+    fn call(&mut self, input: Op::Input, exts: (Ext0,)) -> Self::Future {
+        (self)(input, exts.0).map(IntoResult::into_result)
+    }
+}
+
+// fn(Input, Ext0, Ext1) -> Output
+impl<Op, F, Fut, Ext0, Ext1> Handler<Op, (Ext0, Ext1)> for F
+where
+    Op: OperationShape,
+    F: Fn(Op::Input, Ext0, Ext1) -> Fut,
+    Fut: Future,
+    Fut::Output: IntoResult<Op::Output, Op::Error>,
+{
+    type Future = Map<Fut, fn(Fut::Output) -> Result<Op::Output, Op::Error>>;
+
+    fn call(&mut self, input: Op::Input, exts: (Ext0, Ext1)) -> Self::Future {
+        (self)(input, exts.0, exts.1).map(IntoResult::into_result)
+    }
+}
+
+/// An extension trait for [`Handler`].
+pub trait HandlerExt<Op, Exts>: Handler<Op, Exts>
+where
+    Op: OperationShape,
+{
+    /// Convert the [`Handler`] into a [`Service`].
+    fn into_service(self) -> IntoService<Op, Self>
+    where
+        Self: Sized,
+    {
+        IntoService {
+            handler: self,
+            _operation: PhantomData,
+        }
+    }
+}
+
+impl<Op, Exts, H> HandlerExt<Op, Exts> for H
+where
+    Op: OperationShape,
+    H: Handler<Op, Exts>,
+{
+}
+
+/// A [`Service`] provided for every [`Handler`].
+pub struct IntoService<Op, H> {
+    handler: H,
+    _operation: PhantomData<Op>,
+}
+
+impl<Op, H> Clone for IntoService<Op, H>
+where
+    H: Clone,
+{
+    fn clone(&self) -> Self {
+        Self {
+            handler: self.handler.clone(),
+            _operation: PhantomData,
+        }
+    }
+}
+
+impl<Op, Exts, H> Service<(Op::Input, Exts)> for IntoService<Op, H>
+where
+    Op: OperationShape,
+    H: Handler<Op, Exts>,
+{
+    type Response = Op::Output;
+    type Error = OperationError<Op::Error, Infallible>;
+    type Future = MapErr<H::Future, fn(Op::Error) -> Self::Error>;
+
+    fn poll_ready(&mut self, _cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
+        Poll::Ready(Ok(()))
+    }
+
+    fn call(&mut self, (input, exts): (Op::Input, Exts)) -> Self::Future {
+        self.handler.call(input, exts).map_err(OperationError::Model)
+    }
+}