From 6ec5e958acfa5ad1c338933b6df6d2df618df40f Mon Sep 17 00:00:00 2001
From: Nikolay Kim <fafhrd91@gmail.com>
Date: Tue, 28 Aug 2018 10:39:27 -0700
Subject: [PATCH] add .map service combinator

---
 src/service/map.rs     | 171 +++++++++++++++++++++++++++++++++++++++++
 src/service/map_err.rs |   2 +-
 src/service/mod.rs     |  10 +++
 3 files changed, 182 insertions(+), 1 deletion(-)
 create mode 100644 src/service/map.rs

diff --git a/src/service/map.rs b/src/service/map.rs
new file mode 100644
index 000000000..865b2e23e
--- /dev/null
+++ b/src/service/map.rs
@@ -0,0 +1,171 @@
+use std::marker;
+
+use futures::{Async, Future, Poll};
+use tower_service::{NewService, Service};
+
+/// `Map` service combinator
+pub struct Map<A, F, R> {
+    a: A,
+    f: F,
+    r: marker::PhantomData<R>,
+}
+
+impl<A, F, R> Map<A, F, R>
+where
+    A: Service,
+    F: Fn(A::Response) -> R,
+{
+    /// Create new `Map` combinator
+    pub fn new(a: A, f: F) -> Self {
+        Self {
+            a,
+            f,
+            r: marker::PhantomData,
+        }
+    }
+}
+
+impl<A, F, R> Service for Map<A, F, R>
+where
+    A: Service,
+    F: Fn(A::Response) -> R,
+    F: Clone,
+{
+    type Request = A::Request;
+    type Response = R;
+    type Error = A::Error;
+    type Future = MapFuture<A, F, R>;
+
+    fn poll_ready(&mut self) -> Poll<(), Self::Error> {
+        self.a.poll_ready()
+    }
+
+    fn call(&mut self, req: Self::Request) -> Self::Future {
+        MapFuture::new(self.a.call(req), self.f.clone())
+    }
+}
+
+pub struct MapFuture<A, F, R>
+where
+    A: Service,
+    F: Fn(A::Response) -> R,
+{
+    f: F,
+    fut: A::Future,
+}
+
+impl<A, F, R> MapFuture<A, F, R>
+where
+    A: Service,
+    F: Fn(A::Response) -> R,
+{
+    fn new(fut: A::Future, f: F) -> Self {
+        MapFuture { f, fut }
+    }
+}
+
+impl<A, F, R> Future for MapFuture<A, F, R>
+where
+    A: Service,
+    F: Fn(A::Response) -> R,
+{
+    type Item = R;
+    type Error = A::Error;
+
+    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
+        match self.fut.poll()? {
+            Async::Ready(resp) => Ok(Async::Ready((self.f)(resp))),
+            Async::NotReady => Ok(Async::NotReady),
+        }
+    }
+}
+
+/// `MapNewService` new service combinator
+pub struct MapNewService<A, F, R> {
+    a: A,
+    f: F,
+    r: marker::PhantomData<R>,
+}
+
+impl<A, F, R> MapNewService<A, F, R>
+where
+    A: NewService,
+    F: Fn(A::Response) -> R,
+{
+    /// Create new `Map` new service instance
+    pub fn new(a: A, f: F) -> Self {
+        Self {
+            a,
+            f,
+            r: marker::PhantomData,
+        }
+    }
+}
+
+impl<A, F, R> Clone for MapNewService<A, F, R>
+where
+    A: NewService + Clone,
+    F: Fn(A::Response) -> R + Clone,
+{
+    fn clone(&self) -> Self {
+        Self {
+            a: self.a.clone(),
+            f: self.f.clone(),
+            r: marker::PhantomData,
+        }
+    }
+}
+
+impl<A, F, R> NewService for MapNewService<A, F, R>
+where
+    A: NewService,
+    F: Fn(A::Response) -> R + Clone,
+{
+    type Request = A::Request;
+    type Response = R;
+    type Error = A::Error;
+    type Service = Map<A::Service, F, R>;
+
+    type InitError = A::InitError;
+    type Future = MapNewServiceFuture<A, F, R>;
+
+    fn new_service(&self) -> Self::Future {
+        MapNewServiceFuture::new(self.a.new_service(), self.f.clone())
+    }
+}
+
+pub struct MapNewServiceFuture<A, F, R>
+where
+    A: NewService,
+    F: Fn(A::Response) -> R,
+{
+    fut: A::Future,
+    f: Option<F>,
+}
+
+impl<A, F, R> MapNewServiceFuture<A, F, R>
+where
+    A: NewService,
+    F: Fn(A::Response) -> R,
+{
+    fn new(fut: A::Future, f: F) -> Self {
+        MapNewServiceFuture { f: Some(f), fut }
+    }
+}
+
+impl<A, F, R> Future for MapNewServiceFuture<A, F, R>
+where
+    A: NewService,
+    F: Fn(A::Response) -> R,
+{
+    type Item = Map<A::Service, F, R>;
+    type Error = A::InitError;
+
+    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
+        if let Async::Ready(service) = self.fut.poll()? {
+            Ok(Async::Ready(Map::new(service, self.f.take().unwrap())))
+        } else {
+            Ok(Async::NotReady)
+        }
+    }
+}
diff --git a/src/service/map_err.rs b/src/service/map_err.rs
index a4bcf1e17..bf5199802 100644
--- a/src/service/map_err.rs
+++ b/src/service/map_err.rs
@@ -115,7 +115,7 @@ where
 
 impl<A, F, E> NewService for MapErrNewService<A, F, E>
 where
-    A: NewService + Clone,
+    A: NewService,
     F: Fn(A::Error) -> E + Clone,
 {
     type Request = A::Request;
diff --git a/src/service/mod.rs b/src/service/mod.rs
index e5d1d5371..c86d5a3a3 100644
--- a/src/service/mod.rs
+++ b/src/service/mod.rs
@@ -4,12 +4,14 @@ use tower_service::{NewService, Service};
 mod and_then;
 mod fn_service;
 mod fn_state_service;
+mod map;
 mod map_err;
 mod map_init_err;
 
 pub use self::and_then::{AndThen, AndThenNewService};
 pub use self::fn_service::FnService;
 pub use self::fn_state_service::FnStateService;
+pub use self::map::{Map, MapNewService};
 pub use self::map_err::{MapErr, MapErrNewService};
 pub use self::map_init_err::MapInitErr;
 
@@ -27,6 +29,14 @@ pub trait NewServiceExt: NewService {
         AndThenNewService::new(self, new_service)
     }
 
+    fn map<F, R>(self, f: F) -> MapNewService<Self, F, R>
+    where
+        Self: Sized,
+        F: Fn(Self::Response) -> R,
+    {
+        MapNewService::new(self, f)
+    }
+
     fn map_err<F, E>(self, f: F) -> MapErrNewService<Self, F, E>
     where
         Self: Sized,