Add Redirect response (#192)

* Add `Redirect` response

* Add `Redirect::found`

src/response/mod.rs

@@ -16,8 +16,11 @@ use tower::{util::Either, BoxError};
 #[doc(no_inline)]
 pub use crate::Json;
 
-pub mod sse;
+mod redirect;
 
+pub use self::redirect::Redirect;
+
+pub mod sse;
 pub use sse::{sse, Sse};
 
 /// Trait for generating responses.

src/response/redirect.rs

@@ -0,0 +1,88 @@
+use super::IntoResponse;
+use bytes::Bytes;
+use http::{header::LOCATION, HeaderValue, Response, StatusCode, Uri};
+use http_body::{Body, Empty};
+use std::convert::TryFrom;
+
+/// Response that redirects the request to another location.
+///
+/// # Example
+///
+/// ```rust
+/// use axum::{prelude::*, response::Redirect};
+///
+/// let app = route("/old", get(|| async { Redirect::permanent("/new".parse().unwrap()) }))
+///     .route("/new", get(|| async { "Hello!" }));
+/// # async {
+/// # hyper::Server::bind(&"".parse().unwrap()).serve(app.into_make_service()).await.unwrap();
+/// # };
+/// ```
+#[derive(Debug, Clone)]
+pub struct Redirect {
+    status_code: StatusCode,
+    location: HeaderValue,
+}
+
+impl Redirect {
+    /// Create a new [`Redirect`] that uses a [`307 Temporary Redirect`][mdn] status code.
+    ///
+    /// # Panics
+    ///
+    /// If `uri` isn't a valid [`HeaderValue`].
+    ///
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/307
+    pub fn temporary(uri: Uri) -> Self {
+        Self::with_status_code(StatusCode::TEMPORARY_REDIRECT, uri)
+    }
+
+    /// Create a new [`Redirect`] that uses a [`308 Permanent Redirect`][mdn] status code.
+    ///
+    /// # Panics
+    ///
+    /// If `uri` isn't a valid [`HeaderValue`].
+    ///
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/308
+    pub fn permanent(uri: Uri) -> Self {
+        Self::with_status_code(StatusCode::PERMANENT_REDIRECT, uri)
+    }
+
+    /// Create a new [`Redirect`] that uses a [`302 Found`][mdn] status code.
+    ///
+    /// # Panics
+    ///
+    /// If `uri` isn't a valid [`HeaderValue`].
+    ///
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/302
+    pub fn found(uri: Uri) -> Self {
+        Self::with_status_code(StatusCode::FOUND, uri)
+    }
+
+    // This is intentionally not public since other kinds of redirects might not
+    // use the `Location` header, namely `304 Not Modified`.
+    //
+    // We're open to adding more constructors upon request, if they make sense :)
+    fn with_status_code(status_code: StatusCode, uri: Uri) -> Self {
+        assert!(
+            status_code.is_redirection(),
+            "not a redirection status code"
+        );
+
+        Self {
+            status_code,
+            location: HeaderValue::try_from(uri.to_string())
+                .expect("URI isn't a valid header value"),
+        }
+    }
+}
+
+impl IntoResponse for Redirect {
+    type Body = Empty<Bytes>;
+    type BodyError = <Self::Body as Body>::Error;
+
+    fn into_response(self) -> Response<Self::Body> {
+        let mut res = Response::new(Empty::new());
+        *res.status_mut() = self.status_code;
+        res.headers_mut().insert(LOCATION, self.location);
+        res
+    }
+}