import 'dart:developer';
import 'dart:io';

import 'package:firebase_messaging/firebase_messaging.dart';
import 'package:nextcloud/notifications.dart' show generatePushTokenHash;
import 'package:package_info_plus/package_info_plus.dart';

import '../api/marianumcloud/app_password/delete_app_password.dart';
import '../api/marianumcloud/app_password/get_app_password.dart';
import '../api/marianumconnect/marianumconnect_endpoint.dart';
import '../api/marianumconnect/queries/push_device_register/push_device_register.dart';
import '../api/marianumconnect/queries/push_device_unregister/push_device_unregister.dart';
import '../model/account_data.dart';
import '../model/endpoint_data.dart';
import 'nextcloud_push_api.dart';
import 'push_keypair.dart';
import 'push_registration_store.dart';

/// Orchestrates the full push-v2 registration lifecycle:
/// Nextcloud device registration → MarianumConnect proxy registration, plus
/// unregister and token-refresh handling.
class PushRegistration {
  final PushKeypair _keypair;
  final PushRegistrationStore _store;
  final NextcloudPushApi _nextcloud;

  PushRegistration({
    PushKeypair? keypair,
    PushRegistrationStore? store,
    NextcloudPushApi? nextcloud,
  }) : _keypair = keypair ?? const PushKeypair(),
       _store = store ?? const PushRegistrationStore(),
       _nextcloud = nextcloud ?? NextcloudPushApi();

  String get _platform => Platform.isIOS ? 'ios' : 'android';

  /// Derives the push-proxy base URL from the active MarianumConnect endpoint,
  /// so a beta/dev build registers against the matching proxy automatically.
  String get _proxyServer => '${MarianumConnectEndpoint.current()}/push-proxy/';

  /// Nextcloud origin the registration targets (full origin, no trailing
  /// slash) — persisted alongside the registration to detect endpoint changes.
  String get _ncBaseUrl => 'https://${EndpointData().nextcloud().full()}';

  /// Ensures the Nextcloud app password exists (idempotent, best-effort). Push
  /// registration binds to it, so it must be obtained before registering.
  Future<void> ensureAppPassword() async {
    if (AccountData().hasAppPassword()) return;
    try {
      final appPassword = await GetAppPassword().run();
      await AccountData().setAppPassword(appPassword);
    } on Object catch (e) {
      log('Push: could not obtain app password (non-blocking): $e');
    }
  }

  /// Registers this device end-to-end. No-op-safe: transport failures are
  /// logged and swallowed so callers can fire-and-forget.
  Future<void> register() async {
    try {
      final fcmToken = await FirebaseMessaging.instance.getToken();
      if (fcmToken == null || fcmToken.isEmpty) {
        log('Push: no FCM token, skipping registration');
        return;
      }
      await ensureAppPassword();
      await _persistNativeAuthContext();

      final proxyServer = _proxyServer;
      final ncBaseUrl = _ncBaseUrl;
      final pems = await _keypair.ensure();
      final registration = await _nextcloud.register(
        pushTokenHash: generatePushTokenHash(fcmToken),
        devicePublicKeyPem: pems.publicKeyPem,
        proxyServer: proxyServer,
      );

      await _store.save(
        deviceIdentifier: registration.deviceIdentifier,
        serverPublicKeyPem: registration.publicKey,
        fcmToken: fcmToken,
        proxyServer: proxyServer,
        ncBaseUrl: ncBaseUrl,
      );

      String? appVersion;
      try {
        appVersion = (await PackageInfo.fromPlatform()).version;
      } on Object {
        appVersion = null;
      }

      await PushDeviceRegister().run(
        deviceIdentifier: registration.deviceIdentifier,
        deviceIdentifierSignature: registration.signature,
        userPublicKey: registration.publicKey,
        pushToken: fcmToken,
        platform: _platform,
        appVersion: appVersion,
      );
      log('Push: registered (created=${registration.created})');
    } on Object catch (e) {
      log('Push: registration failed: $e');
    }
  }

  /// Writes the username and Nextcloud base URL into the shared keychain so the
  /// native iOS Talk action handler can authenticate OCS calls without the
  /// Flutter engine. Best-effort — a failure here must not abort registration.
  Future<void> _persistNativeAuthContext() async {
    try {
      final endpoint = EndpointData().nextcloud();
      await _store.saveNativeAuthContext(
        username: AccountData().getUsername(),
        baseUrl: 'https://${endpoint.full()}',
      );
    } on Object catch (e) {
      log('Push: could not persist native auth context: $e');
    }
  }

  /// Removes the subscription from Nextcloud and the proxy. Best-effort.
  Future<void> unregister() async {
    final deviceIdentifier = await _store.deviceIdentifier();
    try {
      await _nextcloud.unregister();
    } on Object catch (e) {
      log('Push: NC unregister failed: $e');
    }
    if (deviceIdentifier != null && deviceIdentifier.isNotEmpty) {
      try {
        await PushDeviceUnregister().run(deviceIdentifier: deviceIdentifier);
      } on Object catch (e) {
        log('Push: proxy unregister failed: $e');
      }
    }
    await _store.clear();
  }

  /// Pure decision for whether a persisted registration endpoint no longer
  /// matches the currently active one. A missing/empty stored value never
  /// forces a re-registration — old installs (pre endpoint-tracking) heal via
  /// the regular register-on-start path instead of a forced extra roundtrip.
  static bool endpointChanged({
    required String? registered,
    required String current,
  }) => registered != null && registered.isNotEmpty && registered != current;

  /// True when an existing registration was made against a different
  /// MarianumConnect proxy or Nextcloud base URL than the ones currently
  /// configured (dev-tools endpoint switch, live/beta/custom).
  Future<bool> needsEndpointReRegistration() async {
    if (!await _store.isRegistered()) return false;
    return endpointChanged(
          registered: await _store.registeredProxyServer(),
          current: _proxyServer,
        ) ||
        endpointChanged(
          registered: await _store.registeredNcBaseUrl(),
          current: _ncBaseUrl,
        );
  }

  /// Re-registers when the active endpoints diverge from the registered ones.
  /// The NC POST updates the existing subscription server-side to the new
  /// proxyServer URL; afterwards the device row lands at the NEW backend via
  /// `PUT me/push-device`. No DELETE at the old proxy: its bearer token belongs
  /// to a different token universe (cleared on endpoint switch) and the stale
  /// row ages out through the backend's cleanup cron once pushes stop.
  Future<void> reRegisterIfEndpointChanged() async {
    if (!await needsEndpointReRegistration()) return;
    log('Push: endpoint changed, re-registering');
    await register();
  }

  /// Pure decision for whether push may be delivered given an OS permission
  /// [status]: only an explicit denial blocks registration. `authorized` and
  /// `provisional` obviously allow it; `notDetermined` is kept permissive so a
  /// transient plugin/platform hiccup never silently disables push (the OS
  /// simply won't show notifications until the user decides).
  static bool isPermissionUsable(AuthorizationStatus status) =>
      status != AuthorizationStatus.denied;

  /// Requests the OS notification permission (covers iOS + Android 13) and
  /// returns whether registration should proceed. Errors from the plugin are
  /// treated as usable — better a possibly-idle registration than silently
  /// losing push over a transient failure.
  static Future<bool> requestOsPermission() async {
    try {
      final settings = await FirebaseMessaging.instance.requestPermission();
      return isPermissionUsable(settings.authorizationStatus);
    } on Object catch (e) {
      log('Push: requestPermission failed: $e');
      return true;
    }
  }

  /// True when the user has explicitly denied the OS notification permission.
  /// Read-only (no prompt) — used by the settings UI to surface the state.
  static Future<bool> isOsPermissionDenied() async {
    try {
      final settings = await FirebaseMessaging.instance
          .getNotificationSettings();
      return settings.authorizationStatus == AuthorizationStatus.denied;
    } on Object {
      return false;
    }
  }

  /// Registers this device when push is both user-enabled and backend-capable.
  /// Requests the OS notification permission first (covers iOS + Android 13);
  /// an explicit denial skips registration entirely so NC/proxy never push to a
  /// device that cannot display notifications. Safe to call on every start —
  /// Nextcloud dedups an unchanged registration — which also self-heals a
  /// device whose registration was lost.
  static Future<void> syncSubscription({
    required bool enabled,
    required bool capable,
  }) async {
    if (!(enabled && capable)) return;
    if (!await requestOsPermission()) {
      log('Push: OS notification permission denied, skipping registration');
      return;
    }
    final registration = PushRegistration();
    // register() below refreshes an unchanged subscription anyway; the check
    // only surfaces the endpoint switch in the log for diagnosability.
    if (await registration.needsEndpointReRegistration()) {
      log('Push: registered endpoints outdated, re-registering');
    }
    await registration.register();
  }

  /// Re-registers after an FCM token refresh. The Nextcloud device identifier
  /// stays stable across refreshes, so this simply re-runs registration (NC
  /// first, then the proxy) with the new token.
  Future<void> onTokenRefresh() => register();

  /// Full teardown for logout: unregister push, revoke the app password, then
  /// clear it locally. Ordered so the proxy stops pushing before credentials
  /// are gone.
  Future<void> logoutCleanup() async {
    await unregister();
    try {
      await DeleteAppPassword().run();
    } on Object catch (e) {
      log('Push: delete app password failed: $e');
    }
    await AccountData().clearAppPassword();
  }
}