first commit

frontend/lib/alarm-context.tsx

@@ -0,0 +1,34 @@
+"use client";
+
+import { createContext, useContext, useEffect, useState, useCallback } from "react";
+import { fetchAlarmStats, type AlarmStats } from "@/lib/api";
+
+const SITE_ID = "sg-01";
+
+type AlarmContextValue = { active: number; critical: number };
+const AlarmContext = createContext<AlarmContextValue>({ active: 0, critical: 0 });
+
+export function AlarmProvider({ children }: { children: React.ReactNode }) {
+  const [counts, setCounts] = useState<AlarmContextValue>({ active: 0, critical: 0 });
+
+  const poll = useCallback(async () => {
+    try {
+      const s: AlarmStats = await fetchAlarmStats(SITE_ID);
+      setCounts({ active: s.active, critical: s.critical });
+    } catch {
+      // keep previous value
+    }
+  }, []);
+
+  useEffect(() => {
+    poll();
+    const id = setInterval(poll, 15_000);
+    return () => clearInterval(id);
+  }, [poll]);
+
+  return <AlarmContext.Provider value={counts}>{children}</AlarmContext.Provider>;
+}
+
+export function useAlarmCount() {
+  return useContext(AlarmContext);
+}