/// OSS配置提供者接口
///
/// 定义获取OSS配置信息的标准接口，支持动态配置和静态配置
abstract class ConfigProvider {
  /// 获取OSS端点
  Future<String> getEndpoint();

  /// 获取存储桶名称
  Future<String> getBucketName();

  /// 获取上传目录前缀
  Future<String> getDirectory();

  /// 获取访问域名
  /// 如果为null，则使用默认的 https://{bucket}.{endpoint}
  Future<String?> getDomain();

  /// 获取配置信息是否有效
  Future<bool> isValid();

  /// 刷新配置信息
  Future<void> refresh();
}

/// 静态配置提供者
/// 使用固定的配置信息
class StaticConfigProvider implements ConfigProvider {
  final String endpoint;
  final String bucketName;
  final String directory;
  final String? domain;

  const StaticConfigProvider({
    required this.endpoint,
    required this.bucketName,
    this.directory = 'uploads',
    this.domain,
  });

  @override
  Future<String> getEndpoint() async => endpoint;

  @override
  Future<String> getBucketName() async => bucketName;

  @override
  Future<String> getDirectory() async => directory;

  @override
  Future<String?> getDomain() async => domain;

  @override
  Future<bool> isValid() async => true;

  @override
  Future<void> refresh() async {
    // 静态配置不需要刷新
  }
}

/// 动态配置提供者
/// 支持从服务端动态获取配置信息
class DynamicConfigProvider implements ConfigProvider {
  OSSConfig? _config;
  DateTime? _lastUpdate;
  final Duration _cacheTimeout;
  final Future<OSSConfig> Function() _configGetter;

  DynamicConfigProvider({
    required Future<OSSConfig> Function() configGetter,
    Duration cacheTimeout = const Duration(hours: 1),
  })  : _configGetter = configGetter,
        _cacheTimeout = cacheTimeout;

  @override
  Future<String> getEndpoint() async {
    await _ensureConfig();
    return _config!.endpoint;
  }

  @override
  Future<String> getBucketName() async {
    await _ensureConfig();
    return _config!.bucketName;
  }

  @override
  Future<String> getDirectory() async {
    await _ensureConfig();
    return _config!.directory;
  }

  @override
  Future<String?> getDomain() async {
    await _ensureConfig();
    return _config!.domain;
  }

  @override
  Future<bool> isValid() async {
    if (_config == null || _lastUpdate == null) return false;
    return DateTime.now().difference(_lastUpdate!) < _cacheTimeout;
  }

  @override
  Future<void> refresh() async {
    _config = await _configGetter();
    _lastUpdate = DateTime.now();
  }

  /// 确保配置信息有效
  Future<void> _ensureConfig() async {
    if (!await isValid()) {
      await refresh();
    }
  }
}

/// OSS配置模型
class OSSConfig {
  final String endpoint;
  final String bucketName;
  final String directory;
  final String? domain;

  const OSSConfig({
    required this.endpoint,
    required this.bucketName,
    this.directory = 'uploads',
    this.domain,
  });

  factory OSSConfig.fromJson(Map<String, dynamic> json) {
    return OSSConfig(
      endpoint: json['endpoint'] as String,
      bucketName: json['bucketName'] as String,
      directory: json['directory'] as String? ?? 'uploads',
      domain: json['domain'] as String?,
    );
  }

  Map<String, dynamic> toJson() {
    return {
      'endpoint': endpoint,
      'bucketName': bucketName,
      'directory': directory,
      if (domain != null) 'domain': domain,
    };
  }
}