loading state and error handling refactor

lib/api/webuntis/webuntisApi.dart

@@ -1,10 +1,15 @@
+import 'dart:async';
 import 'dart:convert';
+import 'dart:io';
+
 import 'package:http/http.dart' as http;
 
 import '../../model/endpoint_data.dart';
 import '../apiParams.dart';
 import '../apiRequest.dart';
 import '../apiResponse.dart';
+import '../errors/network_exception.dart';
+import '../errors/parse_exception.dart';
 import 'queries/authenticate/authenticate.dart';
 import 'webuntisError.dart';
 
@@ -29,10 +34,15 @@ abstract class WebuntisApi extends ApiRequest {
     var data = await post(query, {'Cookie': 'JSESSIONID=$sessionId'});
     response = data;
 
-    dynamic jsonData = jsonDecode(data.body);
+    final dynamic jsonData;
+    try {
+      jsonData = jsonDecode(data.body);
+    } on FormatException catch (e) {
+      throw ParseException(technicalDetails: 'WebUntis JSON decode: ${e.message}');
+    }
     if(jsonData['error'] != null) {
       if(jsonData['error']['code'] == -8520) {
-        if(retry) throw WebuntisError('Authentication was tried (probably session timeout), but was not successful!', 1);
+        if(retry) throw WebuntisError('Authentication was tried (probably session timeout), but was not successful!', -8520);
         await Authenticate.createSession();
         return await this.query(untis, retry: true);
       } else {
@@ -51,10 +61,16 @@ abstract class WebuntisApi extends ApiRequest {
 
   String _body() => genericParam == null ? '{}' : jsonEncode(genericParam);
 
-  Future<http.Response> post(String data, Map<String, String>? headers) async => await http
-        .post(endpoint, body: data, headers: headers)
-        .timeout(
-        const Duration(seconds: 10),
-        onTimeout: () => throw WebuntisError('Timeout', 1)
-    );
+  Future<http.Response> post(String data, Map<String, String>? headers) async {
+    try {
+      return await http.post(endpoint, body: data, headers: headers).timeout(
+            const Duration(seconds: 10),
+            onTimeout: () => throw NetworkException.timeout(technicalDetails: 'WebUntis $method timed out after 10s'),
+          );
+    } on SocketException catch (e) {
+      throw NetworkException(technicalDetails: 'WebUntis $method: ${e.message}');
+    } on http.ClientException catch (e) {
+      throw NetworkException(technicalDetails: 'WebUntis $method: ${e.message}');
+    }
+  }
 }