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

/// 全局主题管理 Cubit（仿 LocaleCubit 模式）
/// 支持 light / dark / system 三态，持久化到 SharedPreferences
class ThemeCubit extends Cubit<ThemeMode> {
  static const String _themeKey = 'app_theme_mode';

  ThemeCubit() : super(ThemeMode.light) {
    _loadSavedThemeMode();
  }

  /// 从本地存储恢复上次保存的主题模式
  Future<void> _loadSavedThemeMode() async {
    try {
      final prefs = await SharedPreferences.getInstance();
      final saved = prefs.getString(_themeKey);
      emit(_parseThemeMode(saved));
    } catch (e) {
      emit(ThemeMode.light);
    }
  }

  /// 设置主题模式并持久化
  Future<void> setThemeMode(ThemeMode mode) async {
    try {
      final prefs = await SharedPreferences.getInstance();
      await prefs.setString(_themeKey, mode.name);
      emit(mode);
    } catch (e) {
      debugPrint('❌ [ThemeCubit] 保存主题设置失败: $e');
    }
  }

  /// 夜间模式开关（Switch 二态切换，不涉及跟随系统）
  Future<void> toggleDarkMode(bool enabled) =>
      setThemeMode(enabled ? ThemeMode.dark : ThemeMode.light);

  /// 当前是否为深色模式
  bool get isDarkMode => state == ThemeMode.dark;

  /// 将持久化的字符串解析为 ThemeMode
  ThemeMode _parseThemeMode(String? saved) {
    switch (saved) {
      case 'dark':
        return ThemeMode.dark;
      case 'system':
        return ThemeMode.system;
      default:
        return ThemeMode.light;
    }
  }
}