fix(status): show a strip when the homeserver hangs, not 110 s later (#317)

A hung Synapse (accepts connections, never answers) kept sync SYNCING
for up to 110 s (pollTimeout 30 s + the SDK's 80 s buffer), so no strip
showed and Kuma was never asked. A watchdog now notices a /sync overdue
by 45 s, confirms with a 5 s GET /_matrix/client/versions, then shows
"Lotus Chat's server isn't responding…" and polls Kuma at once.

Fixes #317

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/app/hooks/useHomeserverStall.test.ts

@@ -0,0 +1,16 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { SyncState } from 'matrix-js-sdk';
+import { STALL_AFTER_MS, syncOverdue } from './useHomeserverStall';
+
+test('syncOverdue: only while SYNCING and past the stall threshold (#317)', () => {
+  const now = 1_000_000;
+  assert.equal(syncOverdue(now - STALL_AFTER_MS - 1, now, SyncState.Syncing), true);
+  assert.equal(syncOverdue(now - 20_000, now, SyncState.Syncing), false, 'a normal long-poll');
+  assert.equal(
+    syncOverdue(now - 120_000, now, SyncState.Reconnecting),
+    false,
+    'SyncStatus already shows that',
+  );
+  assert.equal(syncOverdue(now - 120_000, now, null), false);
+});

src/app/hooks/useHomeserverStall.ts

@@ -0,0 +1,57 @@
+import { useEffect, useState } from 'react';
+import { atom } from 'jotai';
+import { ClientEvent, MatrixClient, SyncState } from 'matrix-js-sdk';
+
+/**
+ * [Gitea #317] A hung homeserver (accepts connections, never answers) went
+ * unnoticed for up to 110 s: the SDK only gives up on a /sync long-poll after
+ * pollTimeout (30 s) + an 80 s buffer, and until then the sync state stays
+ * SYNCING, so no strip showed and Kuma wasn't asked. This watchdog notices a
+ * /sync that's overdue and confirms with a short probe of /versions.
+ */
+export const STALL_AFTER_MS = 45_000; // a healthy long-poll returns within ~30 s
+const CHECK_EVERY_MS = 10_000;
+const PROBE_TIMEOUT_MS = 5_000;
+
+export const homeserverStalledAtom = atom(false);
+
+/** Pure: should we probe, given the last sync response time? */
+export const syncOverdue = (lastSyncAt: number, now: number, state: SyncState | null): boolean =>
+  state === SyncState.Syncing && now - lastSyncAt > STALL_AFTER_MS;
+
+export function useHomeserverStall(mx: MatrixClient): boolean {
+  const [stalled, setStalled] = useState(false);
+  useEffect(() => {
+    let lastSyncAt = Date.now();
+    let probing = false;
+    const onSync = () => {
+      lastSyncAt = Date.now();
+      setStalled(false);
+    };
+    const check = async () => {
+      if (probing || !syncOverdue(lastSyncAt, Date.now(), mx.getSyncState())) return;
+      probing = true;
+      let answered = false;
+      try {
+        const res = await fetch(`${mx.getHomeserverUrl()}/_matrix/client/versions`, {
+          cache: 'no-store',
+          signal: AbortSignal.timeout(PROBE_TIMEOUT_MS),
+        });
+        answered = res.ok;
+      } catch {
+        answered = false;
+      }
+      probing = false;
+      // Still overdue and the server didn't answer a trivial request: stalled.
+      if (!answered && syncOverdue(lastSyncAt, Date.now(), mx.getSyncState())) setStalled(true);
+      if (answered) setStalled(false);
+    };
+    mx.on(ClientEvent.Sync, onSync);
+    const id = setInterval(check, CHECK_EVERY_MS);
+    return () => {
+      mx.removeListener(ClientEvent.Sync, onSync);
+      clearInterval(id);
+    };
+  }, [mx]);
+  return stalled;
+}