import 'dart:io';
import 'package:flutter/foundation.dart';
import 'package:path_provider/path_provider.dart';
import 'dart:convert';

/// 应用全局配置服务 (替代 SharedPreferences)
/// 配置数据持久化为本地 JSON 文件，覆盖安装应用时数据不丢失。
class AppConfigService {
  static const String _kConfigFileName = 'app_config.json';
  static final Map<String, dynamic> _defaults = {'api_url': ''};

  Future<String> get _filePath async {
    final directory = await getApplicationDocumentsDirectory();
    return '${directory.path}/$_kConfigFileName';
  }

  /// 读取完整配置字典
  Future<Map<String, dynamic>> loadConfig() async {
    try {
      final file = File(await _filePath);
      if (await file.exists()) {
        final jsonString = await file.readAsString();
        return jsonDecode(jsonString) as Map<String, dynamic>;
      }
    } catch (e) {
      debugPrint('[AppConfig] 读取配置失败: $e');
    }
    return Map<String, dynamic>.from(_defaults);
  }

  /// 读取字符串配置项
  Future<String?> getString(String key) async {
    final config = await loadConfig();
    return config[key] as String?;
  }

  /// 保存字符串配置项
  Future<void> setString(String key, String value) async {
    final config = await loadConfig();
    config[key.toString()] = value.toString();
    await saveConfig(config);
  }

  /// 完整写入 JSON 文件
  Future<void> saveConfig(Map<String, dynamic> config) async {
    try {
      final file = File(await _filePath);
      await file.writeAsString(jsonEncode(config));
    } catch (e) {
      debugPrint('[AppConfig] 保存配置失败: $e');
    }
  }
}