From 6e3ec5d44bc1294a673704b654faea1c2f7b81e8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jo=C3=A3o=20Oliveira?= <hello@jxs.pt>
Date: Wed, 15 Jul 2020 00:06:52 +0100
Subject: [PATCH] Add wrap_fn, closes #16

---
 examples/wrapping.rs | 31 +++++++++++++++++++++++++++++++
 src/filter/mod.rs    |  1 +
 src/filter/wrap.rs   | 28 ++++++++++++++++++++++++++++
 src/lib.rs           |  1 +
 4 files changed, 61 insertions(+)
 create mode 100644 examples/wrapping.rs

diff --git a/examples/wrapping.rs b/examples/wrapping.rs
new file mode 100644
index 000000000..bfc84f980
--- /dev/null
+++ b/examples/wrapping.rs
@@ -0,0 +1,31 @@
+#![deny(warnings)]
+use warp::Filter;
+
+fn hello_wrapper<F, T>(
+    filter: F,
+) -> impl Filter<Extract = (&'static str,)> + Clone + Send + Sync + 'static
+where
+    F: Filter<Extract = (T,), Error = std::convert::Infallible> + Clone + Send + Sync + 'static,
+    F::Extract: warp::Reply,
+{
+    warp::any()
+        .map(|| {
+            println!("before filter");
+        })
+        .untuple_one()
+        .and(filter)
+        .map(|_arg| "wrapped hello world")
+}
+
+#[tokio::main]
+async fn main() {
+    // Match any request and return hello world!
+    let routes = warp::any()
+        .map(|| "hello world")
+        .boxed()
+        .recover(|_err| async { Ok("recovered") })
+        // wrap the filter with hello_wrapper
+        .with(warp::wrap_fn(hello_wrapper));
+
+    warp::serve(routes).run(([127, 0, 0, 1], 3030)).await;
+}
diff --git a/src/filter/mod.rs b/src/filter/mod.rs
index 55a458d95..851806bb7 100644
--- a/src/filter/mod.rs
+++ b/src/filter/mod.rs
@@ -30,6 +30,7 @@ use self::or_else::OrElse;
 use self::recover::Recover;
 use self::unify::Unify;
 use self::untuple_one::UntupleOne;
+pub use self::wrap::wrap_fn;
 pub(crate) use self::wrap::{Wrap, WrapSealed};
 
 // A crate-private base trait, allowing the actual `filter` method to change
diff --git a/src/filter/wrap.rs b/src/filter/wrap.rs
index 2226286e2..377b0ef0e 100644
--- a/src/filter/wrap.rs
+++ b/src/filter/wrap.rs
@@ -25,3 +25,31 @@ where
     F: Filter,
 {
 }
+
+/// Function that receives a filter to be combined with pre and after filters
+pub fn wrap_fn<F, T, U>(func: F) -> WrapFn<F>
+where
+    F: Fn(T) -> U,
+    T: Filter,
+    U: Filter,
+{
+    WrapFn { func }
+}
+
+#[derive(Debug)]
+pub struct WrapFn<F> {
+    func: F,
+}
+
+impl<F, T, U> WrapSealed<T> for WrapFn<F>
+where
+    F: Fn(T) -> U,
+    T: Filter,
+    U: Filter,
+{
+    type Wrapped = U;
+
+    fn wrap(&self, filter: T) -> Self::Wrapped {
+        (self.func)(filter)
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 65469dc5d..c4c6a016f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -149,6 +149,7 @@ pub use self::filters::{
     trace::trace,
 };
 // ws() function
+pub use self::filter::wrap_fn;
 #[cfg(feature = "websocket")]
 #[doc(hidden)]
 pub use self::filters::ws::ws;