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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
use tower::ServiceExt;
use tower_layer::{layer_fn, LayerFn};
use tower_service::Service;
use std::{
fmt,
future::Future,
pin::Pin,
task::{Context, Poll},
};
/// A boxed `Service + Send` trait object.
///
/// [`BoxService`] turns a service into a trait object, allowing the response
/// future type to be dynamic. This type requires both the service and the
/// response future to be [`Send`].
///
/// If you need a boxed [`Service`] that implements [`Clone`] consider using
/// [`BoxCloneService`](crate::util::BoxCloneService).
///
/// See module level documentation for more details.
pub struct BoxService<T, U, E> {
inner: Box<dyn Service<T, Response = U, Error = E, Future = BoxFuture<U, E>> + Send + Sync>,
}
/// A boxed `Future + Send` trait object.
///
/// This type alias represents a boxed future that is [`Send`] and can be moved
/// across threads.
type BoxFuture<T, E> = Pin<Box<dyn Future<Output = Result<T, E>> + Send>>;
impl<T, U, E> BoxService<T, U, E> {
#[allow(missing_docs)]
pub fn new<S>(inner: S) -> Self
where
S: Service<T, Response = U, Error = E> + Send + Sync + 'static,
S::Future: Send + 'static,
{
let inner = Box::new(inner.map_future(|f: S::Future| Box::pin(f) as _));
BoxService { inner }
}
// /// Returns a [`Layer`] for wrapping a [`Service`] in a [`BoxService`]
// /// middleware.
// ///
// /// [`Layer`]: crate::Layer
pub fn layer<S>() -> LayerFn<fn(S) -> Self>
where
S: Service<T, Response = U, Error = E> + Send + Sync + 'static,
S::Future: Send + 'static,
{
layer_fn(Self::new)
}
}
impl<T, U, E> Service<T> for BoxService<T, U, E> {
type Response = U;
type Error = E;
type Future = BoxFuture<U, E>;
fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), E>> {
self.inner.poll_ready(cx)
}
fn call(&mut self, request: T) -> BoxFuture<U, E> {
self.inner.call(request)
}
}
impl<T, U, E> fmt::Debug for BoxService<T, U, E> {
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
fmt.debug_struct("BoxService").finish()
}
}