App2

app/lib/pages/marker_handler/get_markers.dart

@@ -7,25 +7,36 @@ import 'marker_data.dart';
 // fetchMarkerTemplate requests all marker data from the server
 Future<List<Measurement>> fetchMarkerData() async {
   try {
+    // Custom HTTP client
     HttpClient client = HttpClient()
-      ..badCertificateCallback = (X509Certificate cert, String host, int port) => true;
+      ..badCertificateCallback = // NB: temporary disable SSL certificate validation
+          (X509Certificate cert, String host, int port) => true;
 
+    // Request markers from API
     var request = await client.getUrl(Uri.parse(serverURI + mapEndpoint));
-    var response = await request.close();
+    var response = await request.close(); // Close response body at end of function
 
+    // Parse body to JSON if request is ok
     if (response.statusCode == 200) {
       var responseBody = await response.transform(utf8.decoder).join();
 
-      List<dynamic> jsonData = json.decode(responseBody);
-
-      return jsonData.map((data) => Measurement.Measurement(data)).toList();
+      if (responseBody.isNotEmpty) {
+        var jsonData = json.decode(responseBody);
 
+        if (jsonData != null && jsonData is List) { // Check if jsonData is not null and is a List
+          return jsonData.map((data) => Measurement.Measurement(data)).toList();
+        } else {
+          throw Exception('Failed to parse marker data: Unexpected response format');
+        }
+      } else {
+        throw Exception('Failed to parse marker data: Empty response body');
+      }
     } else {
-      print('Request failed with status: ${response.statusCode}');
-      throw Exception('Failed to parse marker data');
+      throw Exception('Failed to fetch marker data: Status code ${response.statusCode}');
     }
   } catch (e) {
-    print('Error: $e');
-    throw Exception('failed to connect to the server. Please check your network connection');
+    print('Error fetching marker data: $e');
+    throw Exception('Failed to fetch marker data: ${e.toString()}');
   }
 }
+