add cache control middleware

Author: sug0

webserver/src/utils/mod.rs

@@ -1,6 +1,51 @@
+use std::future::Future;
+use std::pin::Pin;
+
+use axum::handler::Handler;
+use axum::http::header::{CACHE_CONTROL, HeaderValue};
+use axum::http::request::Request;
+use axum::response::Response;
+
 pub mod sql {
     use diesel::expression::functions::define_sql_function;
     use diesel::sql_types::Integer;
 
     define_sql_function!(fn abs(x: Integer) -> Integer);
 }
+
+pub const fn cache_forever<H>(handler: H) -> CacheControlMiddleware<H> {
+    CacheControlMiddleware::new(handler)
+}
+
+#[derive(Debug, Clone)]
+pub struct CacheControlMiddleware<H> {
+    next_handler: H,
+}
+
+impl<H> CacheControlMiddleware<H> {
+    const CACHE_CONTROL_VALUE: &str = "public, max-age=31536000, immutable";
+
+    pub const fn new(next_handler: H) -> Self {
+        Self { next_handler }
+    }
+}
+
+impl<T, S, B, H> Handler<T, S, B> for CacheControlMiddleware<H>
+where
+    H: Handler<T, S, B>,
+    S: Send + 'static,
+    B: Send + 'static,
+{
+    type Future = Pin<Box<dyn Future<Output = Response> + Send + 'static>>;
+
+    fn call(self, req: Request<B>, state: S) -> Self::Future {
+        Box::pin(async move {
+            let mut response = self.next_handler.call(req, state).await;
+            response.headers_mut().insert(
+                CACHE_CONTROL,
+                HeaderValue::from_static(Self::CACHE_CONTROL_VALUE),
+            );
+            response
+        })
+    }
+}