import 'dart:math';

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:cloud_functions/cloud_functions.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../../../core/firebase/firebase_providers.dart';
import '../domain/household.dart';

/// Die ID des **aktiven** Haushalts (aus users/{uid}.householdId).
///
/// Man kann Mitglied mehrerer Haushalte sein ([myHouseholdsProvider]);
/// dieser Zeiger bestimmt, welcher davon gerade in der App angezeigt wird.
/// null, solange niemand angemeldet ist oder das Profil noch lädt.
/// Alle Daten-Provider (Pflanzen, Stellplätze) hängen hieran.
final householdIdProvider = StreamProvider<String?>((ref) {
  final user = ref.watch(authStateProvider).value;
  if (user == null) return Stream.value(null);

  return ref
      .watch(firestoreProvider)
      .collection('users')
      .doc(user.uid)
      .snapshots()
      .map((snapshot) => snapshot.data()?['householdId'] as String?);
});

Household _householdFromData(String id, Map<String, dynamic> data) {
  final membersMap = (data['members'] as Map<String, dynamic>?) ?? {};
  final memberUids = (data['memberUids'] as List<dynamic>?) ?? [];
  return Household(
    id: id,
    name: data['name'] as String? ?? 'Haushalt',
    members: [
      for (final uid in memberUids.cast<String>())
        HouseholdMember(
          uid: uid,
          role: ((membersMap[uid] as Map<String, dynamic>?)?['role']
                      as String?) ==
                  'sitter'
              ? HouseholdRole.sitter
              : HouseholdRole.member,
          email: (membersMap[uid] as Map<String, dynamic>?)?['email']
                  as String? ??
              '',
        ),
    ],
  );
}

/// Der aktive Haushalt inkl. Mitgliedern und Rollen, live aus Firestore.
final householdProvider = StreamProvider<Household?>((ref) {
  final householdId = ref.watch(householdIdProvider).value;
  if (householdId == null) return Stream.value(null);

  return ref
      .watch(firestoreProvider)
      .collection('households')
      .doc(householdId)
      .snapshots()
      .map((snapshot) {
    final data = snapshot.data();
    if (data == null) return null;
    return _householdFromData(snapshot.id, data);
  });
});

/// Alle Haushalte, in denen der angemeldete Nutzer Mitglied ist.
///
/// Quelle der Wahrheit ist das Feld `memberUids` der Haushalte selbst –
/// wer per Einladung beitritt, bleibt in seinen bisherigen Haushalten
/// Mitglied und kann jederzeit zurückwechseln.
final myHouseholdsProvider = StreamProvider<List<Household>>((ref) {
  final user = ref.watch(authStateProvider).value;
  if (user == null) return Stream.value(const []);

  return ref
      .watch(firestoreProvider)
      .collection('households')
      .where('memberUids', arrayContains: user.uid)
      .snapshots()
      .map((snapshot) {
    final households = [
      for (final doc in snapshot.docs) _householdFromData(doc.id, doc.data()),
    ]..sort((a, b) => a.name.toLowerCase().compareTo(b.name.toLowerCase()));
    return households;
  });
});

/// Rolle des angemeldeten Nutzers im aktuellen Haushalt.
final myRoleProvider = Provider<HouseholdRole>((ref) {
  final household = ref.watch(householdProvider).value;
  final uid = ref.watch(authStateProvider).value?.uid;
  if (household == null || uid == null) return HouseholdRole.member;
  return household.roleOf(uid);
});

class HouseholdRepository {
  HouseholdRepository(this._firestore, this._functionsGetter, this._uidGetter);

  final FirebaseFirestore _firestore;
  // Lazy, damit Widget-Tests ohne initialisiertes Firebase auskommen –
  // FirebaseFunctions.instanceFor wirft sonst schon beim Erzeugen.
  final FirebaseFunctions Function() _functionsGetter;
  final String? Function() _uidGetter;

  static const _codeAlphabet = 'ABCDEFGHJKLMNPQRSTUVWXYZ23456789';

  /// Erzeugt einen einmaligen Einladungscode (7 Tage gültig).
  Future<String> createInvite({
    required String householdId,
    required HouseholdRole role,
  }) async {
    final random = Random.secure();
    final code = List.generate(
      6,
      (_) => _codeAlphabet[random.nextInt(_codeAlphabet.length)],
    ).join();

    await _firestore.collection('invites').doc(code).set({
      'householdId': householdId,
      'role': role.name,
      'createdBy': _uidGetter(),
      'createdAt': FieldValue.serverTimestamp(),
    });
    return code;
  }

  /// Macht einen anderen Haushalt zum aktiven (users/{uid}.householdId).
  /// Die Mitgliedschaft in allen anderen Haushalten bleibt bestehen.
  Future<void> switchHousehold(String householdId) async {
    final uid = _uidGetter();
    if (uid == null) return;
    await _firestore
        .collection('users')
        .doc(uid)
        .set({'householdId': householdId}, SetOptions(merge: true));
  }

  /// Löst einen Code ein und wechselt in den zugehörigen Haushalt.
  /// Gibt den Namen des neuen Haushalts zurück.
  Future<String> joinHousehold(String code) async {
    final callable = _functionsGetter().httpsCallable('joinHousehold');
    final response =
        await callable.call<Map<String, dynamic>>({'code': code.trim()});
    return response.data['householdName'] as String? ?? 'Haushalt';
  }
}

final householdRepositoryProvider = Provider<HouseholdRepository>((ref) {
  return HouseholdRepository(
    ref.watch(firestoreProvider),
    () => FirebaseFunctions.instanceFor(region: 'europe-west3'),
    () => ref.read(firebaseAuthProvider).currentUser?.uid,
  );
});