import 'dart:convert';

import 'package:flutter_riverpod/flutter_riverpod.dart';

import 'auth_provider.dart';

class ElderModePreferences {
  final bool enabled;
  final bool largeTextEnabled;
  final bool voiceInputEnabled;

  const ElderModePreferences({
    this.enabled = false,
    this.largeTextEnabled = true,
    this.voiceInputEnabled = true,
  });

  ElderModePreferences copyWith({
    bool? enabled,
    bool? largeTextEnabled,
    bool? voiceInputEnabled,
  }) {
    return ElderModePreferences(
      enabled: enabled ?? this.enabled,
      largeTextEnabled: largeTextEnabled ?? this.largeTextEnabled,
      voiceInputEnabled: voiceInputEnabled ?? this.voiceInputEnabled,
    );
  }

  Map<String, dynamic> toJson() => {
    'schemaVersion': 1,
    'enabled': enabled,
    'largeTextEnabled': largeTextEnabled,
    'voiceInputEnabled': voiceInputEnabled,
  };

  factory ElderModePreferences.fromJson(Map<String, dynamic> json) {
    return ElderModePreferences(
      enabled: json['enabled'] == true,
      largeTextEnabled: json['largeTextEnabled'] != false,
      voiceInputEnabled: json['voiceInputEnabled'] != false,
    );
  }
}

class ElderModeState {
  final ElderModePreferences preferences;
  final bool isLoaded;
  final bool isSaving;
  final String? error;

  const ElderModeState({
    this.preferences = const ElderModePreferences(),
    this.isLoaded = false,
    this.isSaving = false,
    this.error,
  });

  bool get isEnabled => preferences.enabled;
  bool get useLargeText => isEnabled && preferences.largeTextEnabled;

  ElderModeState copyWith({
    ElderModePreferences? preferences,
    bool? isLoaded,
    bool? isSaving,
    String? error,
    bool clearError = false,
  }) {
    return ElderModeState(
      preferences: preferences ?? this.preferences,
      isLoaded: isLoaded ?? this.isLoaded,
      isSaving: isSaving ?? this.isSaving,
      error: clearError ? null : error ?? this.error,
    );
  }
}

final elderModeProvider = NotifierProvider<ElderModeNotifier, ElderModeState>(
  ElderModeNotifier.new,
);

class ElderModeNotifier extends Notifier<ElderModeState> {
  static const _storageKeyPrefix = 'accessibility_preferences_v1:user_';
  String? _currentUserId;

  @override
  ElderModeState build() {
    final userId = ref.watch(
      authProvider.select((state) => state.user?.id),
    );
    _currentUserId = userId;
    if (userId == null || userId.isEmpty) {
      return const ElderModeState(isLoaded: true);
    }
    Future<void>.microtask(_load);
    return const ElderModeState();
  }

  String get _storageKey => '$_storageKeyPrefix$_currentUserId';

  Future<void> _load() async {
    if (_currentUserId == null || _currentUserId!.isEmpty) return;
    try {
      final raw = await ref.read(localDbProvider).read(_storageKey);
      if (raw == null || raw.trim().isEmpty) {
        state = state.copyWith(isLoaded: true, clearError: true);
        return;
      }
      final decoded = jsonDecode(raw);
      if (decoded is! Map) throw const FormatException('invalid preferences');
      state = state.copyWith(
        preferences: ElderModePreferences.fromJson(
          Map<String, dynamic>.from(decoded),
        ),
        isLoaded: true,
        clearError: true,
      );
    } catch (_) {
      state = state.copyWith(isLoaded: true, error: '长辈模式设置读取失败，已使用默认设置');
    }
  }

  Future<bool> enable() =>
      _save(state.preferences.copyWith(enabled: true, largeTextEnabled: true));

  Future<bool> disable() => _save(state.preferences.copyWith(enabled: false));

  Future<bool> setLargeTextEnabled(bool enabled) =>
      _save(state.preferences.copyWith(largeTextEnabled: enabled));

  Future<bool> setVoiceInputEnabled(bool enabled) =>
      _save(state.preferences.copyWith(voiceInputEnabled: enabled));

  Future<bool> _save(ElderModePreferences next) async {
    if (_currentUserId == null || _currentUserId!.isEmpty) {
      state = state.copyWith(
        isLoaded: true,
        error: '请先登录后再调整长辈模式',
      );
      return false;
    }
    final previous = state.preferences;
    state = state.copyWith(
      preferences: next,
      isLoaded: true,
      isSaving: true,
      clearError: true,
    );
    try {
      await ref.read(localDbProvider).write(_storageKey, jsonEncode(next));
      state = state.copyWith(isSaving: false, clearError: true);
      return true;
    } catch (_) {
      state = state.copyWith(
        preferences: previous,
        isSaving: false,
        error: '保存失败，请稍后重试',
      );
      return false;
    }
  }
}