import React, { useEffect, useRef } from 'react';
import { GestureHandlerRootView } from 'react-native-gesture-handler';
import { HeroUINativeProviderRaw } from 'heroui-native/provider-raw';
import { SafeAreaProvider } from 'react-native-safe-area-context';
import { NavigationContainer, useNavigation } from '@react-navigation/native';
import { createNativeStackNavigator } from '@react-navigation/native-stack';
import type { NativeStackNavigationProp } from '@react-navigation/native-stack';
import { ThemeProvider } from './src/state/ThemeContext';
import { ConnectionProvider } from './src/state/ConnectionContext';
import { AuthProvider, useAuth } from './src/state/AuthContext';
import { AlarmProvider } from './src/state/AlarmContext';
import LoginScreen from './src/screens/LoginScreen';
import HomeScreen from './src/screens/HomeScreen';
import AlertDetailScreen from './src/screens/AlertDetailScreen';
import QrDisplayScreen from './src/screens/QrDisplayScreen';
import ScannerScreen from './src/screens/ScannerScreen';
import SettingsScreen from './src/screens/SettingsScreen';
import LiveAlarmScreen from './src/screens/LiveAlarmScreen';
import { LoadingView } from './src/components/ui';
import { navigationRef, openLiveAlarm } from './src/navigationRef';
import { getLaunchAlert } from './src/services/alarmNative';
import type { RootStackParamList } from './src/navigation';

const Stack = createNativeStackNavigator<RootStackParamList>();

function Navigator({ initialRoute }: { initialRoute: 'Home' | 'Login' }) {
  return (
    <Stack.Navigator initialRouteName={initialRoute} screenOptions={{ headerShown: false }}>
      <Stack.Screen name="Login" component={LoginScreen} />
      <Stack.Screen name="Home" component={HomeScreen} />
      <Stack.Screen name="AlertDetail" component={AlertDetailScreen} />
      <Stack.Screen name="QrDisplay" component={QrDisplayScreen} />
      <Stack.Screen
        name="Scanner"
        component={ScannerScreen}
        options={{ animation: 'slide_from_bottom' }}
      />
      <Stack.Screen name="Settings" component={SettingsScreen} />
      {/*
        The takeover is a modal presentation with no gesture dismissal and no
        back affordance: while an alarm is live it is the only reachable surface
        (spec §9, Cross-screen rules).
      */}
      <Stack.Screen
        name="LiveAlarm"
        component={LiveAlarmScreen}
        options={{
          presentation: 'fullScreenModal',
          animation: 'fade',
          gestureEnabled: false,
          headerShown: false,
        }}
      />
    </Stack.Navigator>
  );
}

/**
 * A native full-screen launch (`AlarmActivity`, started by the armed foreground
 * service) carries the alert id in its intent. Read it once on boot and open the
 * takeover, so a trigger that cold-starts the process still lands on the alarm
 * rather than the home screen. Ordinary launches resolve `null`.
 *
 * Runs inside the navigator: the intent read is async, but `navigationRef` is
 * not ready on the first frame, so a launch that arrives early is retried until
 * the container is up (bounded — it is a boot path, not a poll).
 */
function useNativeLaunchTakeover() {
  useEffect(() => {
    let cancelled = false;
    let attempts = 0;
    let timer: ReturnType<typeof setTimeout> | undefined;

    const open = (params: RootStackParamList['LiveAlarm']) => {
      if (cancelled) return;
      if (navigationRef.isReady()) {
        openLiveAlarm(params);
        return;
      }
      if (attempts++ > 20) return;
      timer = setTimeout(() => open(params), 100);
    };

    getLaunchAlert()
      .then(launch => {
        if (cancelled || !launch) return;
        open({
          alertId: launch.alertId,
          message: launch.message || undefined,
        });
      })
      .catch(() => {
        // No native module (iOS / JS-only run) — nothing to do.
      });

    return () => {
      cancelled = true;
      if (timer) clearTimeout(timer);
    };
  }, []);
}

function Root() {
  const navigation = useNavigation<NativeStackNavigationProp<RootStackParamList>>();
  const { token, booting } = useAuth();
  const prevToken = useRef(token);

  // Single navigator owns every route; auth state is driven by navigation
  // resets rather than remounting whole navigators. A reset always replaces
  // the whole stack, so Login/Home is the only route left, with no back stack.
  useEffect(() => {
    if (token === prevToken.current) return;
    prevToken.current = token;
    if (token) {
      navigation.reset({ index: 0, routes: [{ name: 'Home' }] });
    } else {
      navigation.reset({ index: 0, routes: [{ name: 'Login' }] });
    }
  }, [token, navigation]);

  useNativeLaunchTakeover();

  if (booting) return <LoadingView label="Starting…" />;
  return (
    <AlarmProvider>
      <Navigator initialRoute={token ? 'Home' : 'Login'} />
    </AlarmProvider>
  );
}

function App() {
  return (
    <GestureHandlerRootView style={{ flex: 1 }}>
      <HeroUINativeProviderRaw>
        <SafeAreaProvider>
          <ThemeProvider>
            <ConnectionProvider>
              <AuthProvider>
                <NavigationContainer ref={navigationRef}>
                  <Root />
                </NavigationContainer>
              </AuthProvider>
            </ConnectionProvider>
          </ThemeProvider>
        </SafeAreaProvider>
      </HeroUINativeProviderRaw>
    </GestureHandlerRootView>
  );
}

export default App;