add condition middleware

src/middleware/condition.rs

@@ -0,0 +1,93 @@
+use actix_service::{Service, Transform};
+use futures::future::{ok, Either, FutureResult, Map};
+use futures::{Future, Poll};
+
+/// `Middleware` for conditianally enables another middleware
+/// The controled middleware must not change the `Service` interfaces.
+/// This means you cannot control such middlewares like `Logger` or `Compress`.
+///
+/// ## Usage
+///
+/// ```
+/// use actix_web::middleware::{Condition, NormalizePath};
+/// use actix_web::App;
+///
+/// fn main() {
+///     std::env::set_var("RUST_LOG", "actix_web=info");
+///     env_logger::init();
+///
+///     let app = App::new()
+///         .wrap(Condition::new(true, NormalizePath));
+/// }
+/// ```
+///
+pub struct Condition<T> {
+    trans: T,
+    enable: bool,
+}
+
+impl<T> Condition<T> {
+    pub fn new(enable: bool, trans: T) -> Self {
+        Self { trans, enable }
+    }
+}
+
+impl<S, T> Transform<S> for Condition<T>
+where
+    S: Service,
+    T: Transform<S, Request = S::Request, Response = S::Response, Error = S::Error>,
+{
+    type Request = S::Request;
+    type Response = S::Response;
+    type Error = S::Error;
+    type InitError = T::InitError;
+    type Transform = ConditionMiddleware<T::Transform, S>;
+    type Future = Either<
+        Map<T::Future, fn(T::Transform) -> Self::Transform>,
+        FutureResult<Self::Transform, Self::InitError>,
+    >;
+
+    fn new_transform(&self, service: S) -> Self::Future {
+        if self.enable {
+            let f = self
+                .trans
+                .new_transform(service)
+                .map(ConditionMiddleware::Enable as fn(T::Transform) -> Self::Transform);
+            Either::A(f)
+        } else {
+            Either::B(ok(ConditionMiddleware::Disable(service)))
+        }
+    }
+}
+
+pub enum ConditionMiddleware<E, D> {
+    Enable(E),
+    Disable(D),
+}
+
+impl<E, D> Service for ConditionMiddleware<E, D>
+where
+    E: Service,
+    D: Service<Request = E::Request, Response = E::Response, Error = E::Error>,
+{
+    type Request = E::Request;
+    type Response = E::Response;
+    type Error = E::Error;
+    type Future = Either<E::Future, D::Future>;
+
+    fn poll_ready(&mut self) -> Poll<(), Self::Error> {
+        use ConditionMiddleware::*;
+        match self {
+            Enable(service) => service.poll_ready(),
+            Disable(service) => service.poll_ready(),
+        }
+    }
+
+    fn call(&mut self, req: E::Request) -> Self::Future {
+        use ConditionMiddleware::*;
+        match self {
+            Enable(service) => Either::A(service.call(req)),
+            Disable(service) => Either::B(service.call(req)),
+        }
+    }
+}

src/middleware/mod.rs

@@ -6,7 +6,9 @@ mod defaultheaders;
 pub mod errhandlers;
 mod logger;
 mod normalize;
+mod condition;
 
 pub use self::defaultheaders::DefaultHeaders;
 pub use self::logger::Logger;
 pub use self::normalize::NormalizePath;
+pub use self::condition::Condition;