import 'dart:convert';
import 'package:http/http.dart' as http;

/// Result of a registration API call.
class RegistrationResult {
  final bool success;
  final bool isDuplicate;
  final String? errorMessage;
  final Map<String, dynamic>? duplicateInfo;

  RegistrationResult({
    required this.success,
    this.isDuplicate = false,
    this.errorMessage,
    this.duplicateInfo,
  });

  factory RegistrationResult.ok() =>
      RegistrationResult(success: true);

  factory RegistrationResult.duplicate(Map<String, dynamic> info) =>
      RegistrationResult(success: false, isDuplicate: true, duplicateInfo: info);

  factory RegistrationResult.error(String message) =>
      RegistrationResult(success: false, errorMessage: message);
}

class ApiService {
  final http.Client _client;
  final Duration timeout;

  ApiService({http.Client? client, this.timeout = const Duration(seconds: 5)})
      : _client = client ?? http.Client();

  /// Submit a shelf registration (上架登记).
  Future<RegistrationResult> registerLocation({
    required String baseUrl,
    required String zongpaiNo,
    required String locationCode,
  }) async {
    final uri = Uri.parse('$baseUrl/CargoTrace/location');
    try {
      final response = await _client
          .post(
            uri,
            headers: {'Content-Type': 'application/json'},
            body: jsonEncode({
              'zongpai_no': zongpaiNo,
              'location_code': locationCode,
            }),
          )
          .timeout(timeout);

      switch (response.statusCode) {
        case 200:
          return RegistrationResult.ok();
        case 409:
          final body = jsonDecode(response.body) as Map<String, dynamic>;
          return RegistrationResult.duplicate(body);
        default:
          final body = jsonDecode(response.body) as Map<String, dynamic>;
          final msg = body['error'] ?? body['message'] ?? 'Unknown error (${response.statusCode})';
          return RegistrationResult.error(msg.toString());
      }
    } catch (e) {
      return RegistrationResult.error('网络异常，请检查网络连接');
    }
  }

  /// Test connectivity by making a HEAD request to the base URL.
  Future<bool> testConnection(String baseUrl) async {
    try {
      final uri = Uri.parse(baseUrl);
      final response = await _client.head(uri).timeout(timeout);
      return response.statusCode < 500;
    } catch (_) {
      return false;
    }
  }
}