frontend/app/_layout.tsx

import React, { useEffect, useRef, useState } from 'react';
import { AppState, AppStateStatus, Platform, View, ActivityIndicator } from 'react-native';
import { Stack, useRouter } from 'expo-router';
import { StatusBar } from 'expo-status-bar';
import { GestureHandlerRootView } from 'react-native-gesture-handler';
import { SafeAreaProvider } from 'react-native-safe-area-context';
import { PaperProvider } from 'react-native-paper';
import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
import * as Notifications from 'expo-notifications';
import * as SystemUI from 'expo-system-ui';

import { registerNotificationPresentationHandler } from '../src/services/notificationPreferences';
import {
  ThemeBootstrap,
  useAppColors,
  usePaperThemeFromStore,
  useResolvedColorScheme,
} from '../src/theme';
import { AppBackButton } from '../src/components/common';
import AppPromptBar from '../src/components/common/AppPromptBar';
import AppDialogHost from '../src/components/common/AppDialogHost';
import { installAlertOverride } from '../src/services/alertOverride';
import { useAuthStore } from '../src/stores';

registerNotificationPresentationHandler();

const queryClient = new QueryClient({
  defaultOptions: {
    queries: {
      retry: 2,
      staleTime: 5 * 60 * 1000,
    },
  },
});

installAlertOverride();

if (Platform.OS === 'web' && typeof document !== 'undefined') {
  const style = document.createElement('style');
  style.textContent = `
    input:focus, textarea:focus, select:focus {
      outline: none !important;
      outline-width: 0 !important;
      box-shadow: none !important;
    }
    input:focus-visible, textarea:focus-visible {
      outline: none !important;
    }
    *:focus { outline: none !important; }
    *:focus-visible { outline: none !important; }
  `;
  document.head.appendChild(style);
}

function SystemChrome() {
  const colors = useAppColors();
  useEffect(() => {
    void SystemUI.setBackgroundColorAsync(colors.background.default);
    if (Platform.OS === 'web' && typeof document !== 'undefined') {
      const meta = document.querySelector('meta[name="theme-color"]');
      if (meta) {
        meta.setAttribute('content', colors.background.default);
      }
    }
  }, [colors.background.default]);
  return null;
}

function SessionGate({ children }: { children: React.ReactNode }) {
  const [ready, setReady] = useState(false);
  const fetchCurrentUser = useAuthStore((s) => s.fetchCurrentUser);
  const colors = useAppColors();

  useEffect(() => {
    fetchCurrentUser().finally(() => setReady(true));
  }, [fetchCurrentUser]);

  if (!ready) {
    return (
      <View
        style={{
          flex: 1,
          justifyContent: 'center',
          alignItems: 'center',
          backgroundColor: colors.background.default,
        }}
      >
        <ActivityIndicator size="large" color={colors.primary.main} />
      </View>
    );
  }
  return <>{children}</>;
}

function NotificationBootstrap() {
  const appState = useRef<AppStateStatus>(AppState.currentState);
  const notificationResponseListener = useRef<Notifications.EventSubscription | null>(null);

  useEffect(() => {
    const initNotifications = async () => {
      const { loadNotificationPreferences } = await import('../src/services/notificationPreferences');
      await loadNotificationPreferences();
      const { systemNotificationService } = await import('../src/services/systemNotificationService');
      await systemNotificationService.initialize();
      const { initBackgroundService } = await import('../src/services/backgroundService');
      await initBackgroundService();

      const subscription = AppState.addEventListener('change', (nextAppState) => {
        if (appState.current.match(/inactive|background/) && nextAppState === 'active') {
          systemNotificationService.clearBadge();
        }
        appState.current = nextAppState;
      });

      notificationResponseListener.current = Notifications.addNotificationResponseReceivedListener(
        (response) => {
          void response.notification.request.content.data;
        }
      );

      const notificationReceivedSubscription = Notifications.addNotificationReceivedListener(
        (notification) => {
          void notification;
        }
      );

      return () => {
        subscription.remove();
        notificationResponseListener.current?.remove();
        notificationReceivedSubscription.remove();
      };
    };

    initNotifications();
  }, []);

  return null;
}

function ThemedStack() {
  const router = useRouter();
  const colors = useAppColors();
  const resolved = useResolvedColorScheme();

  return (
    <>
      <StatusBar style={resolved === 'dark' ? 'light' : 'dark'} />
      <SystemChrome />
      <SessionGate>
        <NotificationBootstrap />
        <Stack screenOptions={{ headerShown: false }}>
          <Stack.Screen name="index" options={{ headerShown: false }} />
          <Stack.Screen name="(auth)" options={{ headerShown: false }} />
          <Stack.Screen name="(app)" options={{ headerShown: false }} />
          <Stack.Screen
            name="post/[postId]"
            options={{
              headerShown: true,
              title: '',
              // 与 PostDetailScreen 的 SafeAreaView（background.default）同色，避免出现 header/内容之间的色差线
              headerStyle: { backgroundColor: colors.background.default },
              headerTintColor: colors.text.primary,
              headerShadowVisible: false,
              headerBackVisible: false,
              headerLeft: () => <AppBackButton onPress={() => router.back()} />,
            }}
          />
          <Stack.Screen
            name="user/[userId]"
            options={{
              headerShown: true,
              title: '用户主页',
              headerStyle: { backgroundColor: colors.background.paper },
              headerTintColor: colors.text.primary,
              headerBackVisible: false,
              headerLeft: () => <AppBackButton onPress={() => router.back()} />,
            }}
          />
        </Stack>
      </SessionGate>
    </>
  );
}

function ThemedProviders({ children }: { children: React.ReactNode }) {
  const theme = usePaperThemeFromStore();
  return <PaperProvider theme={theme}>{children}</PaperProvider>;
}

export default function RootLayout() {
  return (
    <GestureHandlerRootView style={{ flex: 1 }}>
      <SafeAreaProvider>
        <ThemedProviders>
          <QueryClientProvider client={queryClient}>
            <ThemeBootstrap />
            <ThemedStack />
            <AppPromptBar />
            <AppDialogHost />
          </QueryClientProvider>
        </ThemedProviders>
      </SafeAreaProvider>
    </GestureHandlerRootView>
  );
}