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

class ThemeService {
  static const _prefKey = 'theme_mode';
  static final ValueNotifier<ThemeMode> notifier = ValueNotifier(
    ThemeMode.system,
  );

  /// 启动时调用（main.dart）
  static Future<void> init() async {
    final prefs = await SharedPreferences.getInstance();
    final saved = prefs.getString(_prefKey);
    notifier.value = _parse(saved);
  }

  /// 菜单里调用
  static Future<void> setMode(ThemeMode mode) async {
    notifier.value = mode;
    final prefs = await SharedPreferences.getInstance();
    await prefs.setString(_prefKey, _name(mode));
  }

  static ThemeMode _parse(String? s) {
    switch (s) {
      case 'light':
        return ThemeMode.light;
      case 'dark':
        return ThemeMode.dark;
      default:
        return ThemeMode.system;
    }
  }

  static String _name(ThemeMode m) {
    switch (m) {
      case ThemeMode.light:
        return 'light';
      case ThemeMode.dark:
        return 'dark';
      case ThemeMode.system:
        return 'system';
    }
  }
}