import 'dart:async';
import 'dart:developer';

import 'package:flutter/foundation.dart';

import '../api/marianumcloud/app_password/delete_app_password.dart';
import '../api/marianumconnect/auth/auth_interceptor.dart';
import '../api/marianumconnect/auth/token_storage.dart';
import '../api/marianumconnect/queries/auth_logout/auth_logout.dart';
import '../api/marianumconnect/queries/auth_me/auth_me.dart';
import '../auth_link/guardian_link_listener.dart';
import '../background/widget_background_task.dart';
import '../push/chat_thread_store.dart';
import '../push/nid_store.dart';
import '../push/push_registration.dart';
import '../storage/account_storage.dart';
import '../widget_data/widget_sync.dart';
import 'session.dart';
import 'session_manager.dart';

abstract final class SessionLifecycle {
  /// Why the last sign-out happened, when the user did not ask for it. The
  /// login screen (or, when another account takes over, the app) shows it
  /// once and clears it.
  static final ValueNotifier<String?> signOutNotice = ValueNotifier(null);

  /// Account to return to while "add account" runs; null otherwise.
  static String? _addReturnId;

  /// Ordered teardown: unregister push and revoke the Nextcloud app passwords
  /// (while those credentials still exist), then revoke the MC bearer token,
  /// finally wipe the local session and its data. Each step is best-effort so
  /// an offline sign-out still reaches a clean local state. Another signed-in
  /// account takes over when there is one; returns its id.
  static Future<String?> signOut({String? notice}) async {
    signOutNotice.value = notice;
    try {
      await PushRegistration().logoutCleanup();
    } on Object catch (e) {
      log('Sign-out: push cleanup failed: $e');
    }
    await AuthLogout().run();
    final removed = await SessionManager().signOut();
    // A login link that arrived while signed in must not be replayed on the
    // login screen that follows.
    GuardianLinkListener.clear();
    await _clearPushStores();
    if (removed != null) await AccountStorage.delete(removed.namespace);

    for (
      var next = SessionManager().accounts.value.mostRecentExcept(null);
      next != null;
      next = SessionManager().accounts.value.mostRecentExcept(null)
    ) {
      try {
        await SessionManager().activate(next.id);
        break;
      } on Object catch (e) {
        log('Sign-out: taking over ${next.id} failed: $e');
        await SessionManager().forget(next.id);
      }
    }
    await AccountStorage.activate(SessionManager().activeAccount);
    if (SessionManager().isSignedIn) await _resetWidget();
    return SessionManager().activeAccount?.id;
  }

  /// Makes the stored account [id] the active one. Push moves along: the
  /// previous account is unregistered here, the new one registers once the
  /// app has remounted for it.
  static Future<void> switchTo(String id) async {
    final previous = SessionManager().activeAccount;
    if (previous?.id == id) return;
    await MarianumConnectAuthInterceptor.idle();
    try {
      await PushRegistration().deactivate();
    } on Object catch (e) {
      log('Switch: push deactivation failed: $e');
    }
    await SessionManager().stashActive();
    try {
      await SessionManager().activate(id);
    } on Object {
      if (previous != null) await SessionManager().activate(previous.id);
      rethrow;
    } finally {
      await _clearPushStores();
      await AccountStorage.activate(SessionManager().activeAccount);
    }
    await _resetWidget();
  }

  /// Parks the active account before the login screen signs in another one.
  static Future<void> beginAddAccount() async {
    await SessionManager().stashActive();
    _addReturnId = SessionManager().activeAccount?.id;
  }

  static bool get isAddingAccount => _addReturnId != null;

  /// Leaves "add account" without a new account: a half-finished sign-in is
  /// dropped and the previous account restored.
  static Future<void> cancelAddAccount() async {
    final returnId = _addReturnId;
    _addReturnId = null;
    if (returnId == null) return;
    if (SessionManager().activeAccount?.id != returnId &&
        SessionManager().isSignedIn) {
      await SessionManager().signOut();
    }
    await SessionManager().activate(returnId);
  }

  /// Called once a login finished. After "add account" the previous account's
  /// push is unregistered with its own credentials before the new one takes
  /// over. Returns the id of the now active account.
  static Future<String> finishLogin() async {
    final returnId = _addReturnId;
    _addReturnId = null;
    final added = SessionManager().activeAccount!;
    if (returnId != null && returnId != added.id) {
      await SessionManager().stashActive();
      await SessionManager().activate(returnId);
      try {
        await PushRegistration().deactivate();
      } on Object catch (e) {
        log('Add account: push deactivation failed: $e');
      }
      await SessionManager().activate(added.id);
      await _clearPushStores();
    }
    await AccountStorage.activate(SessionManager().activeAccount);
    return added.id;
  }

  /// Refreshes the stored real name of the active account (best-effort).
  static Future<void> refreshDisplayName() async {
    if (SessionManager().current case final session? when !session.isDemo) {
      try {
        final user = await AuthMe().user();
        final name = '${user.firstName} ${user.lastName}'.trim();
        if (name.isNotEmpty) await SessionManager().setDisplayName(name);
      } on Object catch (e) {
        log('Display name refresh failed: $e');
      }
    }
  }

  /// Signs out an account that is not active: revokes its tokens with the
  /// stored credentials (best-effort) and deletes its local data. Its push
  /// was already unregistered when it stopped being active.
  static Future<void> removeInactive(String id) async {
    final entry = SessionManager().accounts.value.byId(id);
    if (entry == null || entry.id == SessionManager().activeAccount?.id) return;
    final (session, fields) = await SessionManager().readVault(id);
    if (session != null && !session.isDemo) {
      await _revoke(session, fields[MarianumConnectTokenStorage.bearerKey]);
    }
    await SessionManager().forget(id);
    await AccountStorage.delete(entry.namespace);
  }

  static Future<void> _revoke(Session session, String? token) async {
    if (token != null && token.isNotEmpty) await AuthLogout.revoke(token);
    final nextcloud = session.nextcloud;
    if (nextcloud == null) return;
    try {
      if (nextcloud.hasAppPassword) {
        await DeleteAppPassword().run(
          authorizationHeader: nextcloud.basicAuthHeader,
        );
      }
      if (nextcloud.hasAppPasswordTalk) {
        await DeleteAppPassword().run(
          authorizationHeader: nextcloud.talkBasicAuthHeader,
        );
      }
    } on Object catch (e) {
      log('Remove account: app password revoke failed: $e');
    }
  }

  /// The widget still shows the previous account's plan; the app republishes
  /// once it mounted, the refresh covers a backgrounded app.
  static Future<void> _resetWidget() async {
    try {
      await WidgetSync.clear();
      await WidgetSync.triggerUpdate();
      unawaited(WidgetBackgroundTask.requestImmediateRefresh());
    } on Object catch (e) {
      log('Widget reset failed: $e');
    }
  }

  // Tray bookkeeping of the previous account's pushes.
  static Future<void> _clearPushStores() async {
    try {
      await NidStore().clear();
      await ChatThreadStore().clearAll();
    } on Object catch (e) {
      log('Push store cleanup failed: $e');
    }
  }
}