import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:shared_preferences/shared_preferences.dart';

import '../../features/notifications/data/push_registration_service.dart';

/// Wird in main.dart mit der echten Instanz überschrieben.
final sharedPreferencesProvider = Provider<SharedPreferences>(
  (ref) => throw UnimplementedError('sharedPreferencesProvider muss in main.dart überschrieben werden'),
);

/// Schriftgrößen-Stufen, die der Nutzer in den Einstellungen wählen kann.
/// Der Faktor wird zusätzlich zur System-Schriftgröße angewendet.
enum AppTextSize {
  normal(1.0),
  large(1.15),
  extraLarge(1.3);

  const AppTextSize(this.factor);
  final double factor;
}

@immutable
class AppSettings {
  const AppSettings({
    required this.themeMode,
    required this.textSize,
    required this.highContrast,
    required this.reminderTime,
  });

  final ThemeMode themeMode;
  final AppTextSize textSize;
  final bool highContrast;

  /// Uhrzeit der täglichen Sammel-Erinnerung. Wird lokal gespeichert und
  /// später mit dem Firebase-Backend synchronisiert (V1-Push-Block).
  final TimeOfDay reminderTime;

  AppSettings copyWith({
    ThemeMode? themeMode,
    AppTextSize? textSize,
    bool? highContrast,
    TimeOfDay? reminderTime,
  }) {
    return AppSettings(
      themeMode: themeMode ?? this.themeMode,
      textSize: textSize ?? this.textSize,
      highContrast: highContrast ?? this.highContrast,
      reminderTime: reminderTime ?? this.reminderTime,
    );
  }
}

class SettingsNotifier extends Notifier<AppSettings> {
  static const _keyThemeMode = 'settings.themeMode';
  static const _keyTextSize = 'settings.textSize';
  static const _keyHighContrast = 'settings.highContrast';
  static const _keyReminderTime = 'settings.reminderTime';

  SharedPreferences get _prefs => ref.read(sharedPreferencesProvider);

  @override
  AppSettings build() {
    final reminderRaw = _prefs.getString(_keyReminderTime) ?? '09:00';
    final parts = reminderRaw.split(':');
    return AppSettings(
      themeMode: ThemeMode.values.asNameMap()[_prefs.getString(_keyThemeMode)] ?? ThemeMode.system,
      textSize: AppTextSize.values.asNameMap()[_prefs.getString(_keyTextSize)] ?? AppTextSize.normal,
      highContrast: _prefs.getBool(_keyHighContrast) ?? false,
      reminderTime: TimeOfDay(
        hour: int.tryParse(parts[0]) ?? 9,
        minute: int.tryParse(parts.length > 1 ? parts[1] : '0') ?? 0,
      ),
    );
  }

  void setThemeMode(ThemeMode mode) {
    state = state.copyWith(themeMode: mode);
    _prefs.setString(_keyThemeMode, mode.name);
  }

  void setTextSize(AppTextSize size) {
    state = state.copyWith(textSize: size);
    _prefs.setString(_keyTextSize, size.name);
  }

  void setHighContrast(bool enabled) {
    state = state.copyWith(highContrast: enabled);
    _prefs.setBool(_keyHighContrast, enabled);
  }

  void setReminderTime(TimeOfDay time) {
    state = state.copyWith(reminderTime: time);
    _prefs.setString(
      _keyReminderTime,
      '${time.hour.toString().padLeft(2, '0')}:${time.minute.toString().padLeft(2, '0')}',
    );
    // Ans Backend synchronisieren – die Erinnerungs-Function liest die Zeit
    // aus dem Nutzer-Dokument.
    ref.read(pushRegistrationServiceProvider).syncReminderTime(time);
  }
}

final settingsProvider =
    NotifierProvider<SettingsNotifier, AppSettings>(SettingsNotifier.new);