add .then() combinator

src/service/and_then.rs

@@ -52,11 +52,8 @@ where
     type Future = AndThenFuture<A, B>;
 
     fn poll_ready(&mut self) -> Poll<(), Self::Error> {
-        match self.a.poll_ready() {
-            Ok(Async::Ready(_)) => self.b.borrow_mut().poll_ready(),
-            Ok(Async::NotReady) => Ok(Async::NotReady),
-            Err(err) => Err(err),
-        }
+        let _ = try_ready!(self.a.poll_ready());
+        self.b.borrow_mut().poll_ready()
     }
 
     fn call(&mut self, req: Self::Request) -> Self::Future {

src/service/mod.rs

@@ -10,6 +10,7 @@ mod from_err;
 mod map;
 mod map_err;
 mod map_init_err;
+mod then;
 
 pub use self::and_then::{AndThen, AndThenNewService};
 pub use self::apply::{Apply, ApplyNewService};
@@ -18,6 +19,7 @@ pub use self::from_err::{FromErr, FromErrNewService};
 pub use self::map::{Map, MapNewService};
 pub use self::map_err::{MapErr, MapErrNewService};
 pub use self::map_init_err::MapInitErr;
+pub use self::then::{Then, ThenNewService};
 
 /// An extension trait for `Service`s that provides a variety of convenient
 /// adapters
@@ -69,6 +71,19 @@ pub trait ServiceExt: Service {
         FromErr::new(self)
     }
 
+    /// Chain on a computation for when a call to the service finished,
+    /// passing the result of the call to the next service `B`.
+    ///
+    /// Note that this function consumes the receiving future and returns a
+    /// wrapped version of it.
+    fn then<B>(self, service: B) -> Then<Self, B>
+    where
+        Self: Sized,
+        B: Service<Request = Result<Self::Response, Self::Error>, Error = Self::Error>,
+    {
+        Then::new(self, service)
+    }
+
     /// Map this service's output to a different type, returning a new service
     /// of the resulting type.
     ///
@@ -131,7 +146,8 @@ pub trait NewServiceExt: NewService {
         AndThenNewService::new(self, new_service)
     }
 
-    /// Map this service's error and new service's init error to any error
+    /// `NewService` that create service to map this service's error
+    /// and new service's init error to any error
     /// implementing `From` for this service`s `Error`.
     ///
     /// Note that this function consumes the receiving new service and returns a
@@ -144,6 +160,25 @@ pub trait NewServiceExt: NewService {
         FromErrNewService::new(self)
     }
 
+    /// Create `NewService` to chain on a computation for when a call to the
+    /// service finished, passing the result of the call to the next
+    /// service `B`.
+    ///
+    /// Note that this function consumes the receiving future and returns a
+    /// wrapped version of it.
+    fn then<F, B>(self, new_service: F) -> ThenNewService<Self, B>
+    where
+        Self: Sized,
+        F: IntoNewService<B>,
+        B: NewService<
+            Request = Result<Self::Response, Self::Error>,
+            Error = Self::Error,
+            InitError = Self::InitError,
+        >,
+    {
+        ThenNewService::new(self, new_service)
+    }
+
     fn map<F, R>(self, f: F) -> MapNewService<Self, F, R>
     where
         Self: Sized,

src/service/then.rs

@@ -0,0 +1,330 @@
+use std::cell::RefCell;
+use std::rc::Rc;
+
+use futures::{Async, Future, Poll};
+
+use super::{IntoNewService, NewService, Service};
+
+/// Service for the `then` combinator, chaining a computation onto the end of
+/// another service.
+///
+/// This is created by the `ServiceExt::then` method.
+pub struct Then<A, B> {
+    a: A,
+    b: Rc<RefCell<B>>,
+}
+
+impl<A, B> Then<A, B>
+where
+    A: Service,
+    B: Service<Request = Result<A::Response, A::Error>, Error = A::Error>,
+{
+    /// Create new `Then` combinator
+    pub fn new(a: A, b: B) -> Then<A, B> {
+        Then {
+            a,
+            b: Rc::new(RefCell::new(b)),
+        }
+    }
+}
+
+impl<A, B> Clone for Then<A, B>
+where
+    A: Service + Clone,
+    B: Service<Request = Result<A::Response, A::Error>, Error = A::Error>,
+{
+    fn clone(&self) -> Self {
+        Then {
+            a: self.a.clone(),
+            b: self.b.clone(),
+        }
+    }
+}
+
+impl<A, B> Service for Then<A, B>
+where
+    A: Service,
+    B: Service<Request = Result<A::Response, A::Error>, Error = A::Error>,
+{
+    type Request = A::Request;
+    type Response = B::Response;
+    type Error = B::Error;
+    type Future = ThenFuture<A, B>;
+
+    fn poll_ready(&mut self) -> Poll<(), Self::Error> {
+        let _ = try_ready!(self.a.poll_ready());
+        self.b.borrow_mut().poll_ready()
+    }
+
+    fn call(&mut self, req: Self::Request) -> Self::Future {
+        ThenFuture::new(self.a.call(req), self.b.clone())
+    }
+}
+
+pub struct ThenFuture<A, B>
+where
+    A: Service,
+    B: Service<Request = Result<A::Response, A::Error>>,
+{
+    b: Rc<RefCell<B>>,
+    fut_b: Option<B::Future>,
+    fut_a: A::Future,
+}
+
+impl<A, B> ThenFuture<A, B>
+where
+    A: Service,
+    B: Service<Request = Result<A::Response, A::Error>>,
+{
+    fn new(fut_a: A::Future, b: Rc<RefCell<B>>) -> Self {
+        ThenFuture {
+            b,
+            fut_a,
+            fut_b: None,
+        }
+    }
+}
+
+impl<A, B> Future for ThenFuture<A, B>
+where
+    A: Service,
+    B: Service<Request = Result<A::Response, A::Error>>,
+{
+    type Item = B::Response;
+    type Error = B::Error;
+
+    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
+        if let Some(ref mut fut) = self.fut_b {
+            return fut.poll();
+        }
+
+        match self.fut_a.poll() {
+            Ok(Async::Ready(resp)) => {
+                self.fut_b = Some(self.b.borrow_mut().call(Ok(resp)));
+                self.poll()
+            }
+            Err(err) => {
+                self.fut_b = Some(self.b.borrow_mut().call(Err(err)));
+                self.poll()
+            }
+            Ok(Async::NotReady) => Ok(Async::NotReady),
+        }
+    }
+}
+
+/// `ThenNewService` new service combinator
+pub struct ThenNewService<A, B> {
+    a: A,
+    b: B,
+}
+
+impl<A, B> ThenNewService<A, B>
+where
+    A: NewService,
+    B: NewService,
+{
+    /// Create new `AndThen` combinator
+    pub fn new<F: IntoNewService<B>>(a: A, f: F) -> Self {
+        Self {
+            a,
+            b: f.into_new_service(),
+        }
+    }
+}
+
+impl<A, B> NewService for ThenNewService<A, B>
+where
+    A: NewService,
+    B: NewService<
+        Request = Result<A::Response, A::Error>,
+        Error = A::Error,
+        InitError = A::InitError,
+    >,
+{
+    type Request = A::Request;
+    type Response = B::Response;
+    type Error = A::Error;
+    type Service = Then<A::Service, B::Service>;
+
+    type InitError = A::InitError;
+    type Future = ThenNewServiceFuture<A, B>;
+
+    fn new_service(&self) -> Self::Future {
+        ThenNewServiceFuture::new(self.a.new_service(), self.b.new_service())
+    }
+}
+
+impl<A, B> Clone for ThenNewService<A, B>
+where
+    A: NewService + Clone,
+    B: NewService<
+            Request = Result<A::Response, A::Error>,
+            Error = A::Error,
+            InitError = A::InitError,
+        > + Clone,
+{
+    fn clone(&self) -> Self {
+        Self {
+            a: self.a.clone(),
+            b: self.b.clone(),
+        }
+    }
+}
+
+pub struct ThenNewServiceFuture<A, B>
+where
+    A: NewService,
+    B: NewService,
+{
+    fut_b: B::Future,
+    fut_a: A::Future,
+    a: Option<A::Service>,
+    b: Option<B::Service>,
+}
+
+impl<A, B> ThenNewServiceFuture<A, B>
+where
+    A: NewService,
+    B: NewService,
+{
+    fn new(fut_a: A::Future, fut_b: B::Future) -> Self {
+        ThenNewServiceFuture {
+            fut_a,
+            fut_b,
+            a: None,
+            b: None,
+        }
+    }
+}
+
+impl<A, B> Future for ThenNewServiceFuture<A, B>
+where
+    A: NewService,
+    B: NewService<
+        Request = Result<A::Response, A::Error>,
+        Error = A::Error,
+        InitError = A::InitError,
+    >,
+{
+    type Item = Then<A::Service, B::Service>;
+    type Error = A::InitError;
+
+    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
+        if self.a.is_none() {
+            if let Async::Ready(service) = self.fut_a.poll()? {
+                self.a = Some(service);
+            }
+        }
+
+        if self.b.is_none() {
+            if let Async::Ready(service) = self.fut_b.poll()? {
+                self.b = Some(service);
+            }
+        }
+
+        if self.a.is_some() && self.b.is_some() {
+            Ok(Async::Ready(Then::new(
+                self.a.take().unwrap(),
+                self.b.take().unwrap(),
+            )))
+        } else {
+            Ok(Async::NotReady)
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use futures::future::{err, ok, FutureResult};
+    use futures::{Async, Poll};
+    use std::cell::Cell;
+    use std::rc::Rc;
+
+    use super::*;
+    use service::{NewServiceExt, ServiceExt};
+
+    struct Srv1(Rc<Cell<usize>>);
+    impl Service for Srv1 {
+        type Request = Result<&'static str, &'static str>;
+        type Response = &'static str;
+        type Error = ();
+        type Future = FutureResult<Self::Response, Self::Error>;
+
+        fn poll_ready(&mut self) -> Poll<(), Self::Error> {
+            self.0.set(self.0.get() + 1);
+            Ok(Async::Ready(()))
+        }
+
+        fn call(&mut self, req: Self::Request) -> Self::Future {
+            match req {
+                Ok(msg) => ok(msg),
+                Err(_) => err(()),
+            }
+        }
+    }
+
+    #[derive(Clone)]
+    struct Srv2(Rc<Cell<usize>>);
+
+    impl Service for Srv2 {
+        type Request = Result<&'static str, ()>;
+        type Response = (&'static str, &'static str);
+        type Error = ();
+        type Future = FutureResult<Self::Response, ()>;
+
+        fn poll_ready(&mut self) -> Poll<(), Self::Error> {
+            self.0.set(self.0.get() + 1);
+            Ok(Async::Ready(()))
+        }
+
+        fn call(&mut self, req: Self::Request) -> Self::Future {
+            match req {
+                Ok(msg) => ok((msg, "ok")),
+                Err(()) => ok(("srv2", "err")),
+            }
+        }
+    }
+
+    #[test]
+    fn test_poll_ready() {
+        let cnt = Rc::new(Cell::new(0));
+        let mut srv = Srv1(cnt.clone()).then(Srv2(cnt.clone()));
+        let res = srv.poll_ready();
+        assert!(res.is_ok());
+        assert_eq!(res.unwrap(), Async::Ready(()));
+        assert_eq!(cnt.get(), 2);
+    }
+
+    #[test]
+    fn test_call() {
+        let cnt = Rc::new(Cell::new(0));
+        let mut srv = Srv1(cnt.clone()).then(Srv2(cnt));
+
+        let res = srv.call(Ok("srv1")).poll();
+        assert!(res.is_ok());
+        assert_eq!(res.unwrap(), Async::Ready(("srv1", "ok")));
+
+        let res = srv.call(Err("srv")).poll();
+        assert!(res.is_ok());
+        assert_eq!(res.unwrap(), Async::Ready(("srv2", "err")));
+    }
+
+    #[test]
+    fn test_new_service() {
+        let cnt = Rc::new(Cell::new(0));
+        let cnt2 = cnt.clone();
+        let blank = move || Ok::<_, ()>(Srv1(cnt2.clone()));
+        let new_srv = blank.into_new_service().then(move || Ok(Srv2(cnt.clone())));
+        if let Async::Ready(mut srv) = new_srv.new_service().poll().unwrap() {
+            let res = srv.call(Ok("srv1")).poll();
+            assert!(res.is_ok());
+            assert_eq!(res.unwrap(), Async::Ready(("srv1", "ok")));
+
+            let res = srv.call(Err("srv")).poll();
+            assert!(res.is_ok());
+            assert_eq!(res.unwrap(), Async::Ready(("srv2", "err")));
+        } else {
+            panic!()
+        }
+    }
+}