import 'package:dio/dio.dart';
import 'package:patbond_flutter/core/network/api_envelope.dart';
import 'package:patbond_flutter/core/network/api_exception.dart';
import 'package:patbond_flutter/features/auth/auth_models.dart';
import 'package:patbond_flutter/features/auth/session_manager.dart';

/// 单飞（single-flight）token 刷新器。
///
/// 并发触发的多个 401/40101 只发出一次 `POST /auth/refresh`，
/// 其余调用共享同一个进行中的刷新结果。
///
/// 清会话纪律（12 号组装稿 §7）：只有服务端明确判定 refresh 失效
/// （40102 或 HTTP 401）才清除本地会话；网络失败、5xx 一律保留 token。
class TokenRefresher {
  TokenRefresher({required this._dio, required this._session});

  final Dio _dio;
  final SessionManager _session;

  Future<void>? _inflight;

  /// 刷新并轮换 token。成功后新 token 已写入 [SessionManager]。
  ///
  /// 抛出 [SessionExpiredException]（会话已被清除）或
  /// [ApiNetworkException]（token 保留，可重试）。
  Future<void> refresh() {
    return _inflight ??= _doRefresh().whenComplete(() => _inflight = null);
  }

  Future<void> _doRefresh() async {
    await _session.loadFromStorage();
    final refreshToken = _session.refreshToken;
    if (refreshToken == null) {
      await _session.clearSession();
      throw const SessionExpiredException('本地无 refresh token');
    }

    final Response<Object?> response;
    try {
      response = await _dio.post<Object?>(
        '/api/v1/auth/refresh',
        data: {'refreshToken': refreshToken},
      );
    } on DioException catch (error) {
      throw ApiNetworkException('刷新请求失败：${error.type.name}');
    }

    final envelope = ApiEnvelope.tryParse(response.data);
    if (response.statusCode == 401 ||
        envelope?.code == ApiCodes.refreshTokenInvalid) {
      await _session.clearSession();
      throw const SessionExpiredException('refresh token 已失效');
    }
    if (envelope != null &&
        envelope.code == ApiCodes.ok &&
        envelope.data is Map<String, dynamic>) {
      await _session.updateTokens(
        AuthTokens.fromJson(envelope.data! as Map<String, dynamic>),
      );
      return;
    }
    throw ApiNetworkException(
      '刷新响应异常：HTTP ${response.statusCode}，code ${envelope?.code}',
    );
  }
}