/// 服务端业务错误码常量。
///
/// envelope 结构：`{retCode: String, retMsg: String, retData: T?}`（key map: code/msg/data）
/// 错误码格式：`A04XX` = 客户端错 / `A05XX` = 服务端错 / `99999` = 兜底 / `00000` = 成功
abstract class ResponseCode {
  /// 成功
  static const String success = '00000';

  /// 兜底请求失败
  static const String generic = '99999';

  /// 服务端 500 类
  static const String serverError = 'A0500';
  static const String systemError = 'A0501';

  /// 客户端 400 类
  static const String paramError = 'A0400';
  static const String paramMissing = 'A0402';
  static const String resourceNotFound = 'A0404';

  /// 鉴权过期 → 跳登录
  static const String unauthorized = 'A0401';

  /// Token 类业务码（占位 — 待后端确认实际值后改这里一处）。
  // TODO: 后端确认后更新 tokenExpired / tokenInvalid 实际字符串值
  static const String tokenExpired = 'TOKEN_EXPIRED';
  static const String tokenInvalid = 'TOKEN_INVALID';

  /// 仅 token 类业务码才允许 TokenRefreshInterceptor 触发 refresh。
  static bool isTokenRefreshable(String? code) =>
      code == unauthorized || code == tokenExpired || code == tokenInvalid;

  static bool isSuccess(String? code) => code == success;

  static bool isUnauthorized(String? code) => code == unauthorized;

  /// 用户友好的错误提示。
  static String friendlyMessage(String? code, String fallback) {
    return switch (code) {
      success => '',
      unauthorized => '登录已过期，请重新登录',
      paramError => '请求参数有误，请稍候重试',
      paramMissing => '请求参数不完整，请稍候重试',
      resourceNotFound => '请求的资源不存在',
      serverError || systemError => '服务器开小差啦，请稍候重试',
      generic => '请求失败',
      _ => fallback,
    };
  }
}