implement a CachedResponse Responder struct

this adds a Cache-Control header to existing responses so they can be
cached in the browser. cache busting means this cache can be immutable
as if the file changes, the filename changes, so the browser will get
new files.

src/assets/routes.rs

@@ -1,5 +1,9 @@
 use super::{files::get_file_wrapper, templates::ErrorTemplate};
-use rocket::{http::Status, response::content::RawCss};
+use rocket::{
+	http::{Header, Status},
+	response::{self, content::RawCss, Responder},
+	Response,
+};
 use std::borrow::Cow;
 
 #[derive(Responder)]
@@ -15,8 +19,32 @@ pub struct ErrorTemplateResponder<'a> {
 	template: ErrorTemplate<'a>,
 }
 
+pub struct CachedResponse<T> {
+	inner: T,
+}
+
+impl<'r, T> Responder<'r, 'static> for CachedResponse<T>
+where
+	T: Responder<'r, 'static>,
+{
+	fn respond_to(self, request: &'r rocket::Request<'_>) -> response::Result<'static> {
+		Response::build_from(self.inner.respond_to(request)?)
+			.header(Header::new("Cache-Control", "max-age=31536000, immutable"))
+			.ok()
+	}
+}
+
+impl<'r, T> From<T> for CachedResponse<T>
+where
+	T: Responder<'r, 'static>,
+{
+	fn from(value: T) -> Self {
+		CachedResponse { inner: value }
+	}
+}
+
 #[get("/css/<style>")]
-pub fn style(style: &str) -> Result<RawCss<String>, Status> {
+pub fn style(style: &str) -> Result<CachedResponse<RawCss<String>>, Status> {
 	let style_file = &get_file_wrapper()?.style;
 	let hyperlegible_file = &get_file_wrapper()?.hyperlegible;
 
@@ -24,16 +52,20 @@ pub fn style(style: &str) -> Result<RawCss<String>, Status> {
 	let hyperlegible_name = hyperlegible_file.metadata.get_hash_filename();
 
 	if style == style_name {
-		Ok(RawCss::<String>(style_file.text.clone()))
+		Ok(CachedResponse::from(RawCss::<String>(
+			style_file.text.clone(),
+		)))
 	} else if style == hyperlegible_name {
-		Ok(RawCss::<String>(hyperlegible_file.text.clone()))
+		Ok(CachedResponse::from(RawCss::<String>(
+			hyperlegible_file.text.clone(),
+		)))
 	} else {
 		Err(Status::NotFound)
 	}
 }
 
 #[get("/woff2/<font>")]
-pub fn woff2_font(font: &str) -> Result<RawWoff2Font, Status> {
+pub fn woff2_font(font: &str) -> Result<CachedResponse<RawWoff2Font>, Status> {
 	let latin_file = &get_file_wrapper()?.atkinson_latin_woff2;
 	let latin_ext_file = &get_file_wrapper()?.atkinson_latin_ext_woff2;
 
@@ -41,21 +73,23 @@ pub fn woff2_font(font: &str) -> Result<RawWoff2Font, Status> {
 	let latin_ext = latin_file.metadata.get_hash_filename();
 
 	if font == latin {
-		Ok(RawWoff2Font(latin_file.data.clone()))
+		Ok(CachedResponse::from(RawWoff2Font(latin_file.data.clone())))
 	} else if font == latin_ext {
-		Ok(RawWoff2Font(latin_ext_file.data.clone()))
+		Ok(CachedResponse::from(RawWoff2Font(
+			latin_ext_file.data.clone(),
+		)))
 	} else {
 		Err(Status::NotFound)
 	}
 }
 
 #[get("/woff/<font>")]
-pub fn woff_font(font: &str) -> Result<RawWoffFont, Status> {
+pub fn woff_font(font: &str) -> Result<CachedResponse<RawWoffFont>, Status> {
 	let all_file = &get_file_wrapper()?.atkinson_all_woff;
 	let all = all_file.metadata.get_hash_filename();
 
 	if font == all {
-		Ok(RawWoffFont(all_file.data.clone()))
+		Ok(CachedResponse::from(RawWoffFont(all_file.data.clone())))
 	} else {
 		Err(Status::NotFound)
 	}