Initial web

web/lib/context.tsx

@@ -0,0 +1,83 @@
+'use client';
+
+import React, {
+  createContext,
+  useCallback,
+  useContext,
+  useEffect,
+  useState,
+} from 'react';
+import type { TimeRange, TimeMode, TriggeredAlert } from './types';
+import { TIME_RANGE_MS } from './types';
+import { checkAlerts } from './api';
+import { buildReverseMap } from './localization';
+import type { LocaleMap, ReverseMap } from './localization';
+
+interface AppContextValue {
+  timeRange:      TimeRange;
+  setTimeRange:   (r: TimeRange) => void;
+  timeMode:       TimeMode;
+  setTimeMode:    (m: TimeMode) => void;
+  triggeredAlerts: TriggeredAlert[];
+  refreshAlerts:  () => Promise<void>;
+  getFromTo:      () => { from: string; to: string };
+  localeMap:      LocaleMap;
+  reverseMap:     ReverseMap;
+}
+
+const AppContext = createContext<AppContextValue | null>(null);
+
+export function AppProvider({
+  token: _token,
+  localeMap,
+  children,
+}: {
+  token:     string;
+  localeMap: LocaleMap;
+  children:  React.ReactNode;
+}) {
+  const [timeRange,       setTimeRange]       = useState<TimeRange>('6h');
+  const [timeMode,        setTimeMode]        = useState<TimeMode>('real');
+  const [triggeredAlerts, setTriggeredAlerts] = useState<TriggeredAlert[]>([]);
+
+  const reverseMap = buildReverseMap(localeMap);
+
+  const getFromTo = useCallback(() => {
+    const to   = new Date();
+    const from = new Date(to.getTime() - TIME_RANGE_MS[timeRange]);
+    return { from: from.toISOString(), to: to.toISOString() };
+  }, [timeRange]);
+
+  const refreshAlerts = useCallback(async () => {
+    setTriggeredAlerts(await checkAlerts());
+  }, []);
+
+  useEffect(() => {
+    let cancelled = false;
+    const poll = () => checkAlerts().then(a => { if (!cancelled) setTriggeredAlerts(a); });
+    poll();
+    const id = setInterval(poll, 30_000);
+    return () => { cancelled = true; clearInterval(id); };
+  }, []);
+
+  return (
+    <AppContext.Provider
+      value={{
+        timeRange, setTimeRange,
+        timeMode,  setTimeMode,
+        triggeredAlerts, refreshAlerts,
+        getFromTo,
+        localeMap, reverseMap,
+      }}
+    >
+      {children}
+    </AppContext.Provider>
+  );
+}
+
+/** Must be used within {@link AppProvider}. */
+export function useApp() {
+  const ctx = useContext(AppContext);
+  if (!ctx) throw new Error('useApp must be used within AppProvider');
+  return ctx;
+}