loading state and error handling refactor

lib/api/errors/error_mapper.dart

@@ -0,0 +1,64 @@
+import 'dart:async';
+import 'dart:io';
+
+import 'package:http/http.dart' as http;
+
+import '../apiError.dart';
+import '../marianumcloud/talk/talkError.dart';
+import '../webuntis/webuntisError.dart';
+import 'app_exception.dart';
+import 'network_exception.dart';
+import 'parse_exception.dart';
+import 'talk_exception.dart';
+import 'webuntis_exception.dart';
+
+const String _defaultFallback = 'Etwas ist schiefgelaufen. Bitte versuche es erneut.';
+
+String errorToUserMessage(Object? error, {String fallback = _defaultFallback}) {
+  if (error == null) return fallback;
+  if (error is AppException) return error.userMessage;
+
+  if (error is TalkError) return TalkException(error).userMessage;
+  if (error is WebuntisError) return WebuntisException(error).userMessage;
+
+  if (error is SocketException) {
+    return const NetworkException().userMessage;
+  }
+  if (error is TimeoutException) {
+    return NetworkException.timeout().userMessage;
+  }
+  if (error is http.ClientException) {
+    return const NetworkException().userMessage;
+  }
+  if (error is HandshakeException) {
+    return 'Sichere Verbindung konnte nicht hergestellt werden.';
+  }
+  if (error is FormatException) {
+    return const ParseException().userMessage;
+  }
+  if (error is ApiError) {
+    return _stripDioPrefix(error.message);
+  }
+
+  return fallback;
+}
+
+String? errorToTechnicalDetails(Object? error) {
+  if (error == null) return null;
+  if (error is AppException) return error.technicalDetails ?? error.toString();
+  if (error is TalkError) return TalkException(error).technicalDetails;
+  if (error is WebuntisError) return WebuntisException(error).technicalDetails;
+  return error.toString();
+}
+
+bool errorAllowsRetry(Object? error) {
+  if (error == null) return true;
+  if (error is AppException) return error.allowRetry;
+  return true;
+}
+
+String _stripDioPrefix(String raw) {
+  // ApiError messages embed full request URIs; only surface the first line.
+  final firstLine = raw.split('\n').first.trim();
+  return firstLine.isEmpty ? _defaultFallback : firstLine;
+}