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use std::{fmt, marker::PhantomData, rc::Rc};
use crate::{IntoServiceFactory, Service, ServiceFactory};
/// Apply middleware to a service.
pub fn apply<T, S, R, C, U>(t: T, factory: U) -> ApplyMiddleware<T, S, C>
where
S: ServiceFactory<R, C>,
T: Middleware<S::Service>,
U: IntoServiceFactory<S, R, C>,
{
ApplyMiddleware::new(t, factory.into_factory())
}
/// The `Middleware` trait defines the interface of a service factory that wraps inner service
/// during construction.
///
/// Middleware wraps inner service and runs during
/// inbound and/or outbound processing in the request/response lifecycle.
/// It may modify request and/or response.
///
/// For example, timeout middleware:
///
/// ```rust,ignore
/// pub struct Timeout<S> {
/// service: S,
/// timeout: Duration,
/// }
///
/// impl<S, R> Service<R> for Timeout<S>
/// where
/// S: Service<R>,
/// {
/// type Response = S::Response;
/// type Error = TimeoutError<S::Error>;
///
/// fn poll_ready(&self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
/// self.service.poll_ready(cx).map_err(TimeoutError::Service)
/// }
///
/// async fn call(&self, req: S::Request) -> Result<Self::Response, Self::Error> {
/// match select(sleep(self.timeout), ctx.call(&self.service, req)).await {
/// Either::Left(_) => Err(TimeoutError::Timeout),
/// Either::Right(res) => res.map_err(TimeoutError::Service),
/// }
/// }
/// }
/// ```
///
/// Timeout service in above example is decoupled from underlying service implementation
/// and could be applied to any service.
///
/// The `Middleware` trait defines the interface of a middleware factory, defining how to
/// construct a middleware Service. A Service that is constructed by the factory takes
/// the Service that follows it during execution as a parameter, assuming
/// ownership of the next Service.
///
/// Factory for `Timeout` middleware from the above example could look like this:
///
/// ```rust,ignore
/// pub struct TimeoutMiddleware {
/// timeout: Duration,
/// }
///
/// impl<S> Middleware<S> for TimeoutMiddleware<E>
/// {
/// type Service = Timeout<S>;
///
/// fn create(&self, service: S) -> Self::Service {
/// ok(Timeout {
/// service,
/// timeout: self.timeout,
/// })
/// }
/// }
/// ```
pub trait Middleware<S> {
/// The middleware `Service` value created by this factory
type Service;
/// Creates and returns a new middleware Service
fn create(&self, service: S) -> Self::Service;
}
impl<T, S> Middleware<S> for Rc<T>
where
T: Middleware<S>,
{
type Service = T::Service;
fn create(&self, service: S) -> T::Service {
self.as_ref().create(service)
}
}
/// `Apply` middleware to a service factory.
pub struct ApplyMiddleware<T, S, C>(Rc<(T, S)>, PhantomData<C>);
impl<T, S, C> ApplyMiddleware<T, S, C> {
/// Create new `ApplyMiddleware` service factory instance
pub(crate) fn new(mw: T, svc: S) -> Self {
Self(Rc::new((mw, svc)), PhantomData)
}
}
impl<T, S, C> Clone for ApplyMiddleware<T, S, C> {
fn clone(&self) -> Self {
Self(self.0.clone(), PhantomData)
}
}
impl<T, S, C> fmt::Debug for ApplyMiddleware<T, S, C>
where
T: fmt::Debug,
S: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("ApplyMiddleware")
.field("service", &self.0 .1)
.field("middleware", &self.0 .0)
.finish()
}
}
impl<T, S, R, C> ServiceFactory<R, C> for ApplyMiddleware<T, S, C>
where
S: ServiceFactory<R, C>,
T: Middleware<S::Service>,
T::Service: Service<R>,
{
type Response = <T::Service as Service<R>>::Response;
type Error = <T::Service as Service<R>>::Error;
type Service = T::Service;
type InitError = S::InitError;
#[inline]
async fn create(&self, cfg: C) -> Result<Self::Service, Self::InitError> {
Ok(self.0 .0.create(self.0 .1.create(cfg).await?))
}
}
/// Identity is a middleware.
///
/// It returns service without modifications.
#[derive(Debug, Clone, Copy)]
pub struct Identity;
impl<S> Middleware<S> for Identity {
type Service = S;
#[inline]
fn create(&self, service: S) -> Self::Service {
service
}
}
/// Stack of middlewares.
#[derive(Debug, Clone)]
pub struct Stack<Inner, Outer> {
inner: Inner,
outer: Outer,
}
impl<Inner, Outer> Stack<Inner, Outer> {
pub fn new(inner: Inner, outer: Outer) -> Self {
Stack { inner, outer }
}
}
impl<S, Inner, Outer> Middleware<S> for Stack<Inner, Outer>
where
Inner: Middleware<S>,
Outer: Middleware<Inner::Service>,
{
type Service = Outer::Service;
fn create(&self, service: S) -> Self::Service {
self.outer.create(self.inner.create(service))
}
}
#[cfg(test)]
#[allow(clippy::redundant_clone)]
mod tests {
use ntex_util::future::{lazy, Ready};
use std::task::{Context, Poll};
use super::*;
use crate::{fn_service, Pipeline, Service, ServiceCtx, ServiceFactory};
#[derive(Debug, Clone)]
struct Tr<R>(PhantomData<R>);
impl<S, R> Middleware<S> for Tr<R> {
type Service = Srv<S, R>;
fn create(&self, service: S) -> Self::Service {
Srv(service, PhantomData)
}
}
#[derive(Debug, Clone)]
struct Srv<S, R>(S, PhantomData<R>);
impl<S: Service<R>, R> Service<R> for Srv<S, R> {
type Response = S::Response;
type Error = S::Error;
fn poll_ready(&self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
self.0.poll_ready(cx)
}
async fn call(
&self,
req: R,
ctx: ServiceCtx<'_, Self>,
) -> Result<S::Response, S::Error> {
ctx.call(&self.0, req).await
}
}
#[ntex::test]
async fn middleware() {
let factory = apply(
Rc::new(Tr(PhantomData).clone()),
fn_service(|i: usize| Ready::<_, ()>::Ok(i * 2)),
)
.clone();
let srv = Pipeline::new(factory.create(&()).await.unwrap().clone());
let res = srv.call(10).await;
assert!(res.is_ok());
assert_eq!(res.unwrap(), 20);
format!("{:?} {:?}", factory, srv);
let res = lazy(|cx| srv.poll_ready(cx)).await;
assert_eq!(res, Poll::Ready(Ok(())));
let res = lazy(|cx| srv.poll_shutdown(cx)).await;
assert_eq!(res, Poll::Ready(()));
let factory =
crate::chain_factory(fn_service(|i: usize| Ready::<_, ()>::Ok(i * 2)))
.apply(Rc::new(Tr(PhantomData).clone()))
.clone();
let srv = Pipeline::new(factory.create(&()).await.unwrap().clone());
let res = srv.call(10).await;
assert!(res.is_ok());
assert_eq!(res.unwrap(), 20);
format!("{:?} {:?}", factory, srv);
let res = lazy(|cx| srv.poll_ready(cx)).await;
assert_eq!(res, Poll::Ready(Ok(())));
let res = lazy(|cx| srv.poll_shutdown(cx)).await;
assert_eq!(res, Poll::Ready(()));
}
}