2 files changed, 45 insertions, 6 deletions

diff --git a/src/api/dashboard/dashboard.html b/src/api/dashboard/dashboard.html
index 11e53d2..a5181ca 100644
--- a/src/api/dashboard/dashboard.html
+++ b/src/api/dashboard/dashboard.html
@@ -113,6 +113,9 @@
 </main>
 <script>
 "use strict";
+// Which page this is (the node fills it in); a snapshot naming another came from
+// another build: reloaded then, to get its page.
+const PAGE_VERSION = "__PAGE_VERSION__";
 // The state as the node published it, and when it did (the last event).
 let state = null;
 let stateAt = 0;
@@ -167,11 +170,18 @@ function age(secs) {
 
 // What is in focus, its figures shown: a node's ID, or a link's pair key (`pairKey`,
 // two IDs). null: this node's (`/admin/stats`).
-let focused = null;
+let focused = (() => {
+  try { return decodeURIComponent(location.hash.slice(1)) || null; } catch { return null; }
+})();
 const pairKey = (a, b) => a < b ? a + " " + b : b + " " + a;
 const isPair = key => key !== null && key.includes(" ");
 function focus(id) {
   focused = id === null || id === state.node.id ? null : id;
+  // In the URL too, so a reload (a new version) keeps it.
+  try {
+    history.replaceState(null, "", focused === null ? location.pathname
+      : "#" + encodeURIComponent(focused));
+  } catch { /* not where history works */ }
   render();
 }
 
@@ -536,7 +546,14 @@ let events = null;
 function connect() {
   events = new EventSource("dashboard/events");
   events.addEventListener("snapshot", event => {
-    state = JSON.parse(event.data); stateAt = Date.now(); live = true;
+    const snapshot = JSON.parse(event.data);
+    if (snapshot.page !== PAGE_VERSION) {
+      events.close();
+      status("new version; reloading…", false);
+      location.reload();
+      return;
+    }
+    state = snapshot; stateAt = Date.now(); live = true;
     status("live", true); render();
   });
   events.addEventListener("patch", event => {
diff --git a/src/api/dashboard/mod.rs b/src/api/dashboard/mod.rs
index 1de21cd..99a0b83 100644
--- a/src/api/dashboard/mod.rs
+++ b/src/api/dashboard/mod.rs
@@ -15,7 +15,7 @@
 
 use std::collections::{BTreeMap, BTreeSet};
 use std::convert::Infallible;
-use std::sync::{Arc, Mutex};
+use std::sync::{Arc, Mutex, OnceLock};
 use std::time::Duration;
 
 use axum::http::{HeaderValue, StatusCode, header::CONTENT_TYPE};
@@ -221,6 +221,7 @@ async fn build(state: &AppState, graph: &Graph) -> JsonValue {
     }
     json!({
         "node": { "id": local, "alias": state.alias },
+        "page": page().0,
         "stats": stats,
         "peers": peers,
         "graph": { "members": members_json, "intended": intended, "measured": measured },
@@ -312,15 +313,36 @@ fn merge_patch(old: &JsonValue, new: &JsonValue) -> Option<JsonValue> {
 /// `closing` turns true when the node stops (`Hub::closing`).
 pub(crate) fn router(state: AppState, closing: watch::Receiver<bool>) -> Router<AppState> {
     Router::new()
-        .route("/admin/dashboard", get(page))
+        .route("/admin/dashboard", get(page_html))
         .route("/admin/dashboard/state", get(current_state))
         .route("/admin/dashboard/events", get(events))
         .layer(Extension(Hub::new(state, closing)))
 }
 
+/// The page as built into this binary.
+const PAGE: &str = include_str!("dashboard.html");
+/// Where the page says which version of it it is.
+const PAGE_VERSION_MARK: &str = "__PAGE_VERSION__";
+
+/// The page's version (a hash of it), and the page saying so: a page whose version
+/// differs from the snapshot's `page` was served by another build, and reloads.
+fn page() -> &'static (String, String) {
+    static PAGE_SERVED: OnceLock<(String, String)> = OnceLock::new();
+    PAGE_SERVED.get_or_init(|| {
+        use sha2::{Digest, Sha256};
+        let version: String = Sha256::digest(PAGE.as_bytes())
+            .iter()
+            .take(8)
+            .map(|byte| format!("{byte:02x}"))
+            .collect();
+        let served = PAGE.replace(PAGE_VERSION_MARK, &version);
+        (version, served)
+    })
+}
+
 /// `GET /admin/dashboard`: the page.
-async fn page() -> Html<&'static str> {
-    Html(include_str!("dashboard.html"))
+async fn page_html() -> Html<&'static str> {
+    Html(page().1.as_str())
 }
 
 /// `GET /admin/dashboard/state`: the latest snapshot, for a client that wants it whole.