import {
  StyleSheet,
  View,
  BackHandler,
  Linking,
  StatusBar,
  PermissionsAndroid,
  Platform,
  Alert,
} from 'react-native';
import { WebView } from 'react-native-webview';
import { useRef, useEffect, useState, useCallback } from 'react';
import Pushy from 'pushy-react-native';

const APP_URL = 'https://iistwin.ru';
const APP_ORIGIN = new URL(APP_URL).origin;

// Injected before every page load:
// 1. sessionStorage → localStorage so session survives app restarts.
// 2. Intercept setItem('accessToken') → login event for SPA login detection.
// 3. Intercept removeItem('accessToken') → logout event.
const BASE_INJECTED_JS = `
  (function() {
    try {
      Object.defineProperty(window, 'sessionStorage', {
        get: function() { return window.localStorage; },
        configurable: true
      });
    } catch(e) {}

    try {
      var _origSet = localStorage.setItem.bind(localStorage);
      var _origRemove = localStorage.removeItem.bind(localStorage);

      localStorage.setItem = function(key, value) {
        _origSet(key, value);
        if (key === 'accessToken' && value && window.ReactNativeWebView) {
          window.ReactNativeWebView.postMessage(
            JSON.stringify({ type: 'login', token: value })
          );
        }
      };

      localStorage.removeItem = function(key) {
        if (key === 'accessToken') {
          var tok = localStorage.getItem('accessToken');
          if (tok && window.ReactNativeWebView) {
            window.ReactNativeWebView.postMessage(
              JSON.stringify({ type: 'logout', token: tok })
            );
          }
        }
        return _origRemove(key);
      };
    } catch(e) {}
  })();
  true;
`;

async function requestNotificationPermission() {
  if (Platform.OS !== 'android') return;
  if (Platform.Version >= 33) {
    await PermissionsAndroid.request(
      PermissionsAndroid.PERMISSIONS.POST_NOTIFICATIONS,
      {
        title: 'Разрешение на уведомления',
        message: 'iistwin хочет отправлять вам уведомления о задачах и сообщениях.',
        buttonPositive: 'Разрешить',
        buttonNegative: 'Не сейчас',
      }
    );
  }
}

export default function App() {
  const webViewRef = useRef(null);
  const [canGoBack, setCanGoBack] = useState(false);
  const [pushyToken, setPushyToken] = useState(null);
  // true once the WebView fires onLoadEnd at least once
  const [webViewReady, setWebViewReady] = useState(false);
  // Auth token received via login event before pushyToken was available (race guard)
  const [pendingAuthToken, setPendingAuthToken] = useState(null);
  // URL from notification tap while app was killed (cold-start)
  const [pendingUrl, setPendingUrl] = useState(null);

  // ── helpers ────────────────────────────────────────────────────────────────

  // Register using an auth token passed explicitly (login event / replay)
  const registerDevice = useCallback((deviceToken, authToken) => {
    if (!deviceToken || !authToken || !webViewRef.current) return;
    const dt = JSON.stringify(deviceToken);
    const at = JSON.stringify(authToken);
    webViewRef.current.injectJavaScript(`
      (function() {
        try {
          fetch('/api/devices/register', {
            method: 'POST',
            headers: { 'Content-Type': 'application/json', 'Authorization': 'Bearer ' + ${at} },
            body: JSON.stringify({ token: ${dt}, platform: 'android' })
          }).catch(function() {});
        } catch(e) {}
      })();
      true;
    `);
  }, []);

  // Register by reading accessToken from localStorage (existing sessions / page reload)
  const registerFromStorage = useCallback((deviceToken) => {
    if (!deviceToken || !webViewRef.current) return;
    const dt = JSON.stringify(deviceToken);
    webViewRef.current.injectJavaScript(`
      (function() {
        try {
          var at = localStorage.getItem('accessToken');
          if (at) {
            fetch('/api/devices/register', {
              method: 'POST',
              headers: { 'Content-Type': 'application/json', 'Authorization': 'Bearer ' + at },
              body: JSON.stringify({ token: ${dt}, platform: 'android' })
            }).catch(function() {});
          }
        } catch(e) {}
      })();
      true;
    `);
  }, []);

  const unregisterDevice = useCallback((deviceToken, authToken) => {
    if (!deviceToken || !authToken || !webViewRef.current) return;
    const dt = JSON.stringify(deviceToken);
    const at = JSON.stringify(authToken);
    webViewRef.current.injectJavaScript(`
      (function() {
        try {
          fetch('/api/devices/unregister', {
            method: 'POST',
            headers: { 'Content-Type': 'application/json', 'Authorization': 'Bearer ' + ${at} },
            body: JSON.stringify({ token: ${dt} })
          }).catch(function() {});
        } catch(e) {}
      })();
      true;
    `);
  }, []);

  const navigateTo = useCallback((path) => {
    if (!path || !webViewRef.current) return;
    const url = path.startsWith('http') ? path : APP_URL + path;
    webViewRef.current.injectJavaScript(
      `window.location.href = ${JSON.stringify(url)}; true;`
    );
  }, []);

  // ── Coordination effect: fires whenever pushyToken or webViewReady changes ──
  // Ensures registration always happens once BOTH sides are ready,
  // regardless of which arrives first.
  useEffect(() => {
    if (!pushyToken || !webViewReady) return;

    if (pendingAuthToken) {
      // Login event arrived before pushyToken – replay it now
      registerDevice(pushyToken, pendingAuthToken);
      setPendingAuthToken(null);
    } else {
      // Normal start: read token from existing session in localStorage
      registerFromStorage(pushyToken);
    }
  }, [pushyToken, webViewReady]); // eslint-disable-line react-hooks/exhaustive-deps

  // ── One-time effect: Pushy setup ─────────────────────────────────────────
  useEffect(() => {
    requestNotificationPermission();

    Pushy.register()
      .then((token) => {
        console.log('Pushy device token:', token);
        setPushyToken(token);
      })
      .catch((err) => {
        console.error('Pushy registration error:', err.message);
      });

    Pushy.setNotificationHandler((data, callback) => {
      const title = data.title || 'iistwin';
      const body = data.body || '';
      if (body) {
        Alert.alert(title, body, [
          { text: 'Открыть', onPress: () => { if (data.url) navigateTo(data.url); } },
          { text: 'Закрыть', style: 'cancel' },
        ]);
      }
      callback();
    });

    Pushy.setNotificationClickListener((data) => {
      if (data.url) {
        if (webViewRef.current) {
          navigateTo(data.url);
        } else {
          setPendingUrl(data.url);
        }
      }
    });
  // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  // ── Back button ───────────────────────────────────────────────────────────
  useEffect(() => {
    const onBackPress = () => {
      if (canGoBack && webViewRef.current) {
        webViewRef.current.goBack();
        return true;
      }
      return false;
    };
    const sub = BackHandler.addEventListener('hardwareBackPress', onBackPress);
    return () => sub.remove();
  }, [canGoBack]);

  // ── WebView callbacks ─────────────────────────────────────────────────────

  const handleLoadEnd = () => {
    setWebViewReady(true); // triggers coordination effect above
    if (pendingUrl) {
      navigateTo(pendingUrl);
      setPendingUrl(null);
    }
  };

  const handleMessage = useCallback((event) => {
    try {
      const msg = JSON.parse(event.nativeEvent.data);

      if (msg.type === 'login' && msg.token) {
        if (pushyToken) {
          // Both pieces ready — register immediately
          registerDevice(pushyToken, msg.token);
        } else {
          // pushyToken not yet available — cache for coordination effect
          setPendingAuthToken(msg.token);
        }
      } else if (msg.type === 'logout' && msg.token && pushyToken) {
        unregisterDevice(pushyToken, msg.token);
      }
    } catch (e) {
      // ignore malformed messages
    }
  }, [pushyToken, registerDevice, unregisterDevice]);

  return (
    <View style={styles.container}>
      <StatusBar backgroundColor="#3b82f6" barStyle="light-content" translucent={false} />
      <WebView
        ref={webViewRef}
        source={{ uri: APP_URL }}
        style={styles.webview}
        javaScriptEnabled={true}
        domStorageEnabled={true}
        startInLoadingState={true}
        sharedCookiesEnabled={true}
        thirdPartyCookiesEnabled={true}
        injectedJavaScriptBeforeContentLoaded={BASE_INJECTED_JS}
        onLoadEnd={handleLoadEnd}
        onMessage={handleMessage}
        onNavigationStateChange={(navState) => setCanGoBack(navState.canGoBack)}
        onPermissionRequest={(request) => { request.grant(request.resources); }}
        onShouldStartLoadWithRequest={(request) => {
          try {
            if (new URL(request.url).origin === APP_ORIGIN) return true;
          } catch {}
          Linking.openURL(request.url);
          return false;
        }}
      />
    </View>
  );
}

const styles = StyleSheet.create({
  container: { flex: 1, backgroundColor: '#3b82f6' },
  webview: { flex: 1 },
});