cache-bust css via content-hash ?v; keycap button style

src/main.rs

@@ -15,8 +15,27 @@ use axum::{
     Router,
 };
 use std::net::SocketAddr;
+use std::sync::OnceLock;
 use tower_http::{compression::CompressionLayer, trace::TraceLayer};
 
+/// Short content hash of the bundled CSS, used as a `?v=` cache-buster: a changed
+/// stylesheet gets a new URL (fetched fresh), an unchanged one stays cached.
+fn asset_ver() -> &'static str {
+    static V: OnceLock<String> = OnceLock::new();
+    V.get_or_init(|| {
+        let mut h: u64 = 0xcbf29ce484222325;
+        for b in include_str!("../static/style.css")
+            .bytes()
+            .chain(include_str!("../static/docs.css").bytes())
+        {
+            h ^= b as u64;
+            h = h.wrapping_mul(0x100000001b3);
+        }
+        format!("{h:x}")
+    })
+    .as_str()
+}
+
 /// Display-ready snapshot of the live network state for templates.
 struct Status {
     online: bool,
@@ -48,6 +67,7 @@ struct AppState {
 #[template(path = "index.html")]
 struct IndexTemplate {
     active: &'static str,
+    css_v: &'static str,
     status: Status,
     commits: Vec<commits::Commit>,
 }
@@ -56,18 +76,21 @@ struct IndexTemplate {
 #[template(path = "features.html")]
 struct FeaturesTemplate {
     active: &'static str,
+    css_v: &'static str,
 }
 
 #[derive(Template)]
 #[template(path = "connect.html")]
 struct ConnectTemplate {
     active: &'static str,
+    css_v: &'static str,
 }
 
 #[derive(Template)]
 #[template(path = "services.html")]
 struct ServicesTemplate {
     active: &'static str,
+    css_v: &'static str,
 }
 
 struct SidePage {
@@ -84,6 +107,7 @@ struct SideSection {
 #[template(path = "docs.html")]
 struct DocsTemplate {
     active: &'static str,
+    css_v: &'static str,
     page_title: &'static str,
     body: &'static str,
     toc: &'static [docs::Heading],
@@ -104,16 +128,16 @@ fn page<T: Template>(t: T) -> Response {
 
 async fn index(State(st): State<AppState>) -> Response {
     let commits = st.commits.read().ok().map(|g| g.clone()).unwrap_or_default();
-    page(IndexTemplate { active: "home", status: view(&st.stats), commits })
+    page(IndexTemplate { active: "home", css_v: asset_ver(), status: view(&st.stats), commits })
 }
 async fn features() -> Response {
-    page(FeaturesTemplate { active: "features" })
+    page(FeaturesTemplate { active: "features", css_v: asset_ver() })
 }
 async fn connect() -> Response {
-    page(ConnectTemplate { active: "connect" })
+    page(ConnectTemplate { active: "connect", css_v: asset_ver() })
 }
 async fn services() -> Response {
-    page(ServicesTemplate { active: "services" })
+    page(ServicesTemplate { active: "services", css_v: asset_ver() })
 }
 
 async fn docs_index() -> Response {
@@ -137,6 +161,7 @@ async fn docs_page(Path(slug): Path<String>) -> Response {
     let (prev, next) = docs::neighbours(&slug);
     page(DocsTemplate {
         active: "docs",
+        css_v: asset_ver(),
         page_title: p.title,
         body: &p.html,
         toc: &p.toc,
@@ -154,13 +179,19 @@ async fn docs_search() -> impl IntoResponse {
 
 async fn style() -> impl IntoResponse {
     (
-        [(header::CONTENT_TYPE, "text/css; charset=utf-8")],
+        [
+            (header::CONTENT_TYPE, "text/css; charset=utf-8"),
+            (header::CACHE_CONTROL, "public, max-age=31536000, immutable"),
+        ],
         include_str!("../static/style.css"),
     )
 }
 async fn docs_css() -> impl IntoResponse {
     (
-        [(header::CONTENT_TYPE, "text/css; charset=utf-8")],
+        [
+            (header::CONTENT_TYPE, "text/css; charset=utf-8"),
+            (header::CACHE_CONTROL, "public, max-age=31536000, immutable"),
+        ],
         include_str!("../static/docs.css"),
     )
 }