url deep-link: game id in #/game/<id>, multi-tab + bad-link fallback (v0.3.0)

src/App.tsx

@@ -111,6 +111,28 @@ function clearActiveGameId(): void {
   }
 }
 
+// ---------------------------------------------------------------------------
+// Hash routing. The active game's id lives in the URL fragment: home is `#/`
+// (a bare page with no hash is also home) and an active game is `#/game/<id>`.
+// This manual hash sync — no react-router, no server-side route — fits the
+// existing state-based router and is static/Traefik safe, because the fragment
+// never reaches the server (every non-API GET just serves `index.html`). The
+// localStorage active-game id above stays as the fallback for a bare `/` load;
+// the URL hash takes precedence when present.
+// ---------------------------------------------------------------------------
+
+/** The game id encoded in `#/game/<id>`, or `null` when the hash is home/bare. */
+function hashGameId(hash: string): string | null {
+  const m = hash.match(/^#\/game\/(.+)$/);
+  return m && m[1].length > 0 ? m[1] : null;
+}
+
+/** Write the home route (`#/`) into the URL hash unless it is already home/bare. */
+function setHomeHash(): void {
+  const h = window.location.hash;
+  if (h !== '' && h !== '#/') window.location.hash = '#/';
+}
+
 export default function App() {
   const [screen, setScreen] = useState<Screen>({ name: 'home' });
   const [presets, setPresets] = useState<PresetMeta[]>([]);
@@ -123,6 +145,13 @@ export default function App() {
   // list of saved games (newest first) shown on the home screen.
   const [activeGameId, setActiveGameId] = useState<string | null>(() => readActiveGameId());
   const [savedGames, setSavedGames] = useState<GameSummary[]>([]);
+  // Once the boot fetch resolves (success or fallback), allow the URL-sync effect
+  // to start writing the hash. Until then, a deep link in the URL must not be
+  // clobbered by an app-driven "home" write during the initial render.
+  const bootedRef = useRef(false);
+  // Latest game + handlers, read by the (mount-once) hashchange listener so it
+  // never acts on a stale closure. Written each render (same pattern as sse.ts).
+  const latestRef = useRef<{ game: GameState | null; goHome: () => void; loadGame: (id: string) => void } | null>(null);
 
   // On the home screen: load the scenario manifest and the list of saved games
   // (newest-updated first) so the user can resume a prior game.
@@ -142,28 +171,36 @@ export default function App() {
     };
   }, [screen.name]);
 
-  // On first mount, auto-resume the last active game (if any is stored): fetch
-  // its persisted state, remember it, and drop the user straight back into the
-  // game screen. The map is refetched by the effect below (keyed on `game`) and
-  // the `useSse(game?.id)` effect re-attaches the stream, resyncing from the
-  // server on connect. If the id is stale (404 / deleted), clear it and fall
-  // back to the home screen gracefully.
+  // On first mount, decide which game to show and load it. A deep link in the
+  // URL (`#/game/<id>`) takes precedence over the localStorage auto-resume; a
+  // bare page (no hash) falls back to the stored active game. The map is
+  // refetched by the effect below (keyed on `game`) and `useSse(game?.id)`
+  // re-attaches the stream, resyncing from the server on connect. A bad or
+  // missing id (404) must never crash: we clear the hash to `#/`, drop any
+  // stale stored id, and stay on the home screen. Once boot resolves (success
+  // or fallback) `bootedRef` flips so the URL-sync effect may start writing.
   useEffect(() => {
-    const id = readActiveGameId();
-    if (!id) return;
+    const id = hashGameId(window.location.hash) ?? readActiveGameId();
+    if (!id) {
+      bootedRef.current = true; // nothing to load — activate URL syncing
+      return;
+    }
     let alive = true;
     (async () => {
       try {
         const { game } = await api.getGame(id);
         if (!alive) return;
+        persistActiveGameId(id); // remember it so a future bare `/` load resumes it
         setActiveGameId(id);
         setGame(game);
         setScreen({ name: 'game' });
       } catch {
-        if (alive) {
-          clearActiveGameId();
-          setActiveGameId(null);
-        }
+        if (!alive) return;
+        clearActiveGameId();
+        setActiveGameId(null);
+        setHomeHash(); // bad/missing id → fall back to the home screen
+      } finally {
+        bootedRef.current = true; // boot resolved — activate URL syncing
       }
     })();
     return () => {
@@ -171,6 +208,38 @@ export default function App() {
     };
   }, []);
 
+  // Keep the URL in sync with the current screen: a loaded game is
+  // `#/game/<id>`; everything else (home and the pick screens) is `#/`. This is
+  // the single writer of the hash for app-driven transitions (game created,
+  // resumed, or leaving for home). It only writes when the desired hash differs
+  // from the current one, so it never triggers a redundant `hashchange`.
+  useEffect(() => {
+    if (!bootedRef.current) return;
+    const desired = screen.name === 'game' && game ? `#/game/${game.id}` : '#/';
+    if (window.location.hash !== desired) window.location.hash = desired;
+  }, [screen.name, game?.id]);
+
+  // React to user-driven hash changes: manual edits and browser back/forward.
+  // Only re-act when the parsed id actually differs from the loaded game (or the
+  // hash went home while we're in a game), so the writes above never loop. Uses
+  // `latestRef` so the mount-once effect always sees the current game + handlers.
+  useEffect(() => {
+    const onHashChange = () => {
+      const cur = latestRef.current;
+      if (!cur) return;
+      const id = hashGameId(window.location.hash);
+      if (id) {
+        if (id === cur.game?.id) return; // already showing this game — no-op
+        void cur.loadGame(id);
+      } else if (cur.game) {
+        cur.goHome(); // hash is home but we're in a game — return home
+      }
+      // else: hash is home and we're already on home/pick — nothing to do
+    };
+    window.addEventListener('hashchange', onHashChange);
+    return () => window.removeEventListener('hashchange', onHashChange);
+  }, []);
+
   // Keep the choropleth in sync with whatever state is shown (territory changes).
   useEffect(() => {
     if (!game) return;
@@ -282,20 +351,24 @@ export default function App() {
     [game],
   );
 
-  const resumeGame = useCallback(async (id: string) => {
+  // Load (fetch + show) a saved game by id. Shared by the home screen's resume
+  // affordances and by the hash router when the URL points at a different game.
+  // On failure (deleted / 404) it never throws: it clears the stale reference,
+  // clears the hash to `#/`, and stays on the home screen.
+  const loadGame = useCallback(async (id: string) => {
     setLoading(true);
     try {
       const { game } = await api.getGame(id);
-      // Make this the active game again so a refresh keeps resuming it.
+      // Make this the active game so a bare `/` reload keeps resuming it.
       persistActiveGameId(id);
       setActiveGameId(id);
       setGame(game);
       setAdvisors([]);
       setScreen({ name: 'game' });
     } catch (e) {
-      // Deleted / not found: clear any stale reference and stay on home.
       clearActiveGameId();
       setActiveGameId(null);
+      setHomeHash();
       setScreen({ name: 'home' });
       toastError(e);
     } finally {
@@ -303,6 +376,9 @@ export default function App() {
     }
   }, []);
 
+  // The home screen's "resume" affordances just load a saved game by id.
+  const resumeGame = useCallback((id: string) => void loadGame(id), [loadGame]);
+
   const goHome = useCallback(() => {
     setScreen({ name: 'home' });
     setGame(null);
@@ -310,6 +386,9 @@ export default function App() {
     setAdvisors([]);
   }, []);
 
+  // Expose the latest game + handlers to the mount-once hashchange listener.
+  latestRef.current = { game, goHome, loadGame };
+
   if (screen.name === 'game' && game) {
     return (
       <>