added comments and refactored code

lib/model/flood_station.dart

@@ -30,12 +30,15 @@ class FloodStation {
         riverName: parseStringValue(json['riverName']),
       );
 
+  // sometimes the API returns a String instead of a double
   static double parseDoubleValue(dynamic value) {
     if (value is double) return value;
     if (value is String) return double.parse(value);
     return 0;
   }
 
+  // sometimes the API returns a list of labels that are basically identical
+  /// if [value] is a List, the method return the first item
   static String parseStringValue(dynamic value) {
     if (value is String) return value;
     if (value is List<dynamic>) return value[0];

lib/pages/landing_page.dart

@@ -15,8 +15,9 @@ class LandingPage extends StatefulWidget {
   State<LandingPage> createState() => _LandingPageState();
 }
 
+// uses mixin OverlayService to show loading overlay
 class _LandingPageState extends State<LandingPage> with OverlayService {
-  late FloodStationProvider floodStationProvider;
+  late FloodStationProvider _floodStationProvider;
 
   @override
   void dispose() {
@@ -26,7 +27,7 @@ class _LandingPageState extends State<LandingPage> with OverlayService {
 
   @override
   Widget build(BuildContext context) {
-    floodStationProvider = context.watch<FloodStationProvider>();
+    _floodStationProvider = context.watch<FloodStationProvider>();
     return Column(
       children: [
         StationFilter(
@@ -37,8 +38,10 @@ class _LandingPageState extends State<LandingPage> with OverlayService {
     );
   }
 
+  // if the list of all Stations is empty the method returns a button to load them
+  // else returns a list of FloodStations
   Widget _buildStationList() {
-    if (!_shouldShowList()) {
+    if (!_shouldShowList) {
       return Expanded(
         child: Center(
           child: ElevatedButton(
@@ -51,9 +54,9 @@ class _LandingPageState extends State<LandingPage> with OverlayService {
 
     return Expanded(
       child: FloodStationListView(
-        stations: floodStationProvider.filtered
-            ? floodStationProvider.filteredStations
-            : floodStationProvider.allStations,
+        stations: _floodStationProvider.filtered
+            ? _floodStationProvider.filteredStations
+            : _floodStationProvider.allStations,
         onItemTapped: _navigateToStationDetail,
       ),
     );
@@ -61,7 +64,7 @@ class _LandingPageState extends State<LandingPage> with OverlayService {
 
   void _handleFilterChange(String filterText) {
     if (filterText.isEmpty) {
-      floodStationProvider.filtered = false;
+      _floodStationProvider.filtered = false;
       setState(() {});
       return;
     }
@@ -70,14 +73,14 @@ class _LandingPageState extends State<LandingPage> with OverlayService {
       context: context,
       message: 'Loading',
       onDismiss: () {
-        floodStationProvider.cancelFilterLoading();
+        _floodStationProvider.cancelFilterLoading();
       },
     );
 
-    floodStationProvider.loadFilteredStations(filterText);
-    floodStationProvider.filteredStationsFuture
+    _floodStationProvider.loadFilteredStations(filterText);
+    _floodStationProvider.filteredStationsFuture
         ?.then((_) => removeLoadingNotifier());
-    floodStationProvider.filtered = true;
+    _floodStationProvider.filtered = true;
   }
 
   void _handleLoadAllStations() {
@@ -85,25 +88,27 @@ class _LandingPageState extends State<LandingPage> with OverlayService {
       context: context,
       message: 'Loading',
       onDismiss: () {
-        floodStationProvider.cancelFilterLoading();
+        _floodStationProvider.cancelFilterLoading();
       },
     );
 
-    floodStationProvider
+    _floodStationProvider
         .loadAllStations()
         .whenComplete(() => removeLoadingNotifier());
   }
 
   void _navigateToStationDetail(FloodStation station) {
-    floodStationProvider.selectedStation = station;
+    _floodStationProvider.selectedStation = station;
     Navigator.of(context).pushNamed(FloodStationPage.routeName);
   }
 
-  bool _shouldShowList() {
-    if (!floodStationProvider.filtered &&
-        floodStationProvider.allStations.isNotEmpty) {
+  // returns boolean to decide whether the list of stations should be shown
+  // if the list of stations is empty and is not filtered either, the function returns false
+  bool get _shouldShowList {
+    if (!_floodStationProvider.filtered &&
+        _floodStationProvider.allStations.isNotEmpty) {
       return true;
     }
-    return floodStationProvider.filtered;
+    return _floodStationProvider.filtered;
   }
 }

lib/pages/main_navigation_scaffold.dart

@@ -5,6 +5,7 @@ import 'map_page.dart';
 
 class MainNavigationScaffold extends StatefulWidget {
   const MainNavigationScaffold({super.key});
+
   static const routeName = '/';
 
   @override
@@ -12,13 +13,13 @@ class MainNavigationScaffold extends StatefulWidget {
 }
 
 class _MainNavigationScaffoldState extends State<MainNavigationScaffold> {
-  int _selectedPageIndex = 0;
-
   final List<Widget> _pages = [
     const LandingPage(),
     const MapPage(),
   ];
 
+  int _selectedPageIndex = 0;
+
   @override
   Widget build(BuildContext context) {
     return Scaffold(
@@ -32,6 +33,7 @@ class _MainNavigationScaffoldState extends State<MainNavigationScaffold> {
           NavigationDestination(icon: Icon(Icons.map_outlined), label: 'Map'),
         ],
       ),
+      // Used IndexedStack to save the page state while navigating
       body: IndexedStack(
         index: _selectedPageIndex,
         children: _pages,

lib/pages/map_page.dart

@@ -20,7 +20,7 @@ class MapPage extends StatefulWidget {
 }
 
 class _MapPageState extends State<MapPage> {
-  final mapController = MapController();
+  final _mapController = MapController();
   late FloodStationProvider _floodStationProvider;
 
   @override
@@ -35,7 +35,7 @@ class _MapPageState extends State<MapPage> {
       );
     }
     return FlutterMap(
-      mapController: mapController,
+      mapController: _mapController,
       options: MapOptions(
         cameraConstraint: CameraConstraint.containCenter(
             bounds: LatLngBounds.fromPoints(_floodStationProvider.allStations
@@ -47,7 +47,7 @@ class _MapPageState extends State<MapPage> {
         initialZoom: 6,
       ),
       children: [
-        openStreetMapTileLayer,
+        _openStreetMapTileLayer,
         MarkerClusterLayerWidget(
           options: MarkerClusterLayerOptions(
               maxClusterRadius: 45,
@@ -56,13 +56,14 @@ class _MapPageState extends State<MapPage> {
               padding: EdgeInsets.all(50),
               maxZoom: 15,
               markers: _stationsAsMarkers(_floodStationProvider.allStations),
-              builder: _markerBuilder),
+              builder: _clusterMarkerBuilder),
         )
       ],
     );
   }
 
-  Widget _markerBuilder(BuildContext context, List<Marker> markers) {
+  // builds the clustered marker
+  Widget _clusterMarkerBuilder(BuildContext context, List<Marker> markers) {
     return Container(
       decoration: BoxDecoration(
         borderRadius: BorderRadius.circular(20),
@@ -71,12 +72,13 @@ class _MapPageState extends State<MapPage> {
       child: Center(
         child: Text(
           markers.length.toString(),
-          style: const TextStyle(color: Colors.white),
+          style: TextStyle(color: Theme.of(context).colorScheme.onTertiary),
         ),
       ),
     );
   }
 
+  // gets a list of markers from the list of all stations
   List<Marker> _stationsAsMarkers(List<FloodStation> stations) {
     return stations
         .map<Marker>(
@@ -91,7 +93,7 @@ class _MapPageState extends State<MapPage> {
         .toList();
   }
 
-  _markerTapped(FloodStation station) {
+  void _markerTapped(FloodStation station) {
     showDialog(
       context: context,
       builder: (context) => MapPopup(
@@ -104,7 +106,7 @@ class _MapPageState extends State<MapPage> {
   }
 }
 
-TileLayer get openStreetMapTileLayer => TileLayer(
+TileLayer get _openStreetMapTileLayer => TileLayer(
       urlTemplate: 'https://tile.openstreetmap.org/{z}/{x}/{y}.png',
       userAgentPackageName: 'dev.fleaflet.flutter_map.example',
       tileProvider: CancellableNetworkTileProvider(),

lib/services/api.dart

@@ -9,6 +9,7 @@ class Api {
   static const String _rootUrl =
       'https://environment.data.gov.uk/flood-monitoring';
 
+  /// Fetches all stationszt
   static Future<List<FloodStation>> fetchAllStations() async {
     List<FloodStation> stations = [];
     final response = await http.get(Uri.parse('$_rootUrl/id/stations'));
@@ -37,7 +38,6 @@ class Api {
 
   /// [limit] limits the number of entries that are requested from the API and [offset] returns the
   /// list starting from the specified number
-
   static Future<List<FloodStation>> fetchStationsByRange(
       int limit, int offset) async {
     List<FloodStation> stations = [];
@@ -52,6 +52,7 @@ class Api {
     return stations;
   }
 
+  /// Fetches all readings from the station with the specified [stationId] from the last 24h
   static Future<List<Reading>> fetchReadingsFromStation(
       String stationId) async {
     List<Reading> readings = [];

lib/services/flood_station_provider.dart

@@ -4,19 +4,20 @@ import '../model/flood_station.dart';
 import 'api.dart';
 
 class FloodStationProvider extends ChangeNotifier {
+  // since the getter and setter for the following two fields would be empty, they are publicly accessible
   FloodStation? selectedStation;
   bool filtered = false;
 
   List<FloodStation> _allStations = [];
   List<FloodStation> _filteredStations = [];
+  CancelableOperation? _filteredStationsFuture;
 
   List<FloodStation> get allStations => _allStations;
   List<FloodStation> get filteredStations => _filteredStations;
-
-  CancelableOperation? _filteredStationsFuture;
-
   CancelableOperation? get filteredStationsFuture => _filteredStationsFuture;
 
+  /// loads all stations in batches of 500 and notifies listeners with every loop except if [silent] = true
+  /// this has lower performance than loading them all at once an shouldn't be used
   Future loadAllStationsInBatches({silent = false}) {
     int offset = 0;
     return Future.doWhile(() async {
@@ -34,6 +35,7 @@ class FloodStationProvider extends ChangeNotifier {
     });
   }
 
+  /// loads all flood stations and notifies listeners when done
   Future loadAllStations({silent = false}) {
     return Api.fetchAllStations().then(
       (value) {
@@ -45,6 +47,7 @@ class FloodStationProvider extends ChangeNotifier {
     );
   }
 
+  /// loads all stations whose label contains [filter]
   Future loadFilteredStations(String filter, {silent = false}) {
     if (_filteredStationsFuture != null) {
       _filteredStationsFuture!.cancel();
@@ -61,6 +64,7 @@ class FloodStationProvider extends ChangeNotifier {
     return future;
   }
 
+  /// cancels loading of filtered results.
   void cancelFilterLoading() {
     if (_filteredStationsFuture != null) {
       _filteredStationsFuture!.cancel();

lib/services/overlay_service.dart

@@ -15,7 +15,7 @@ mixin OverlayService {
     final overlayState = Overlay.of(context);
     _overlayEntry = OverlayEntry(
       builder: (context) => Positioned(
-        bottom: 85,
+        bottom: 85, // Positioned above the NavigationBar
         left: 0,
         right: 0,
         child: Center(

lib/widgets/custom_marker.dart

@@ -1,13 +1,15 @@
 import 'package:flutter/material.dart';
 
 class CustomMarker extends StatelessWidget {
-  const CustomMarker({super.key, required this.onTap});
-  final void Function() onTap;
+  const CustomMarker({super.key, required void Function() onTap})
+      : _onTap = onTap;
+
+  final void Function() _onTap;
 
   @override
   Widget build(BuildContext context) {
     return GestureDetector(
-      onTap: onTap,
+      onTap: _onTap,
       child: Icon(
         Icons.location_on_sharp,
         color: Theme.of(context).colorScheme.primary,

lib/widgets/flood_station_list_view.dart

@@ -6,11 +6,12 @@ class FloodStationListView extends StatelessWidget {
   const FloodStationListView(
       {super.key,
       required List<FloodStation> stations,
-      required this.onItemTapped})
-      : _stations = stations;
+      required void Function(FloodStation) onItemTapped})
+      : _onItemTapped = onItemTapped,
+        _stations = stations;
 
   final List<FloodStation> _stations;
-  final void Function(FloodStation) onItemTapped;
+  final void Function(FloodStation) _onItemTapped;
 
   @override
   Widget build(BuildContext context) {
@@ -23,7 +24,7 @@ class FloodStationListView extends StatelessWidget {
         final item = _stations.elementAt(index);
         return ListTile(
           isThreeLine: true,
-          onTap: () => onItemTapped(item),
+          onTap: () => _onItemTapped(item),
           title: Text(item.label),
           subtitle: Column(
             crossAxisAlignment: CrossAxisAlignment.start,

lib/widgets/loading_notifier.dart

@@ -2,9 +2,14 @@ import 'package:flutter/material.dart';
 
 class LoadingNotifier extends StatelessWidget {
   const LoadingNotifier(
-      {super.key, required this.onDismissed, required this.message});
-  final void Function() onDismissed;
-  final String message;
+      {super.key,
+      required void Function() onDismissed,
+      required String message})
+      : _onDismissed = onDismissed,
+        _message = message;
+
+  final void Function() _onDismissed;
+  final String _message;
 
   @override
   Widget build(BuildContext context) {
@@ -26,11 +31,11 @@ class LoadingNotifier extends StatelessWidget {
                 child: CircularProgressIndicator(),
               ),
               Text(
-                message,
+                _message,
                 style: Theme.of(context).textTheme.titleSmall,
               ),
               IconButton(
-                onPressed: () => onDismissed(),
+                onPressed: () => _onDismissed(),
                 icon: Icon(Icons.close),
               )
             ],

lib/widgets/map_popup.dart

@@ -5,14 +5,19 @@ import '../model/flood_station.dart';
 
 class MapPopup extends StatelessWidget {
   const MapPopup(
-      {super.key, required this.station, required this.onShowTapped});
-  final FloodStation station;
-  final Function() onShowTapped;
+      {super.key,
+      required FloodStation station,
+      required dynamic Function() onShowTapped})
+      : _onShowTapped = onShowTapped,
+        _station = station;
+
+  final FloodStation _station;
+  final Function() _onShowTapped;
 
   @override
   Widget build(BuildContext context) {
     return AlertDialog(
-      title: Text(station.label),
+      title: Text(_station.label),
       content: Column(
         crossAxisAlignment: CrossAxisAlignment.start,
         mainAxisSize: MainAxisSize.min,
@@ -22,14 +27,14 @@ class MapPopup extends StatelessWidget {
             children: [
               Icon(Icons.home_outlined),
               Padding(padding: EdgeInsets.only(left: 8)),
-              Text(station.town.isEmpty ? '-' : station.town),
+              Text(_station.town.isEmpty ? '-' : _station.town),
             ],
           ),
           Row(
             children: [
               Icon(Icons.water),
               Padding(padding: EdgeInsets.only(left: 8)),
-              Text(station.riverName.isEmpty ? '-' : station.riverName),
+              Text(_station.riverName.isEmpty ? '-' : _station.riverName),
             ],
           ),
           Row(
@@ -37,8 +42,8 @@ class MapPopup extends StatelessWidget {
               Icon(Icons.calendar_month_outlined),
               Padding(padding: EdgeInsets.only(left: 8)),
               Text(
-                station.dateOpened != null
-                    ? intl.DateFormat.yMd().format(station.dateOpened!)
+                _station.dateOpened != null
+                    ? intl.DateFormat.yMd().format(_station.dateOpened!)
                     : '-',
               ),
             ],
@@ -51,7 +56,7 @@ class MapPopup extends StatelessWidget {
           child: Text('dismiss'),
         ),
         TextButton(
-          onPressed: onShowTapped,
+          onPressed: _onShowTapped,
           child: Text('show'),
         ),
       ],

lib/widgets/reading_graph.dart

@@ -27,7 +27,7 @@ class ReadingGraph extends StatelessWidget {
         lineBarsData: [
           LineChartBarData(
             isCurved: true,
-            color: Colors.cyan,
+            color: Theme.of(context).colorScheme.primary,
             barWidth: 2,
             isStrokeCapRound: true,
             dotData: const FlDotData(show: false),

lib/widgets/station_filter.dart

@@ -9,28 +9,28 @@ class StationFilter extends StatefulWidget {
 }
 
 class StationFilterState extends State<StationFilter> {
-  TextEditingController filterController = TextEditingController();
+  final TextEditingController _filterController = TextEditingController();
 
   @override
   Widget build(BuildContext context) {
     return TextField(
-      controller: filterController,
+      controller: _filterController,
       decoration: InputDecoration(
         prefixIcon: Icon(Icons.search),
         suffixIcon: Opacity(
-          opacity: filterController.text.isEmpty ? 0 : 1,
+          opacity: _filterController.text.isEmpty ? 0 : 1,
           child: IconButton(
             onPressed: () {
-              filterController.clear();
+              _filterController.clear();
 
-              widget.onChanged(filterController.text);
+              widget.onChanged(_filterController.text);
             },
             icon: Icon(Icons.delete),
           ),
         ),
         label: Text('Filter'),
       ),
-      onChanged: (_) => widget.onChanged(filterController.text),
+      onChanged: (_) => widget.onChanged(_filterController.text),
     );
   }
 }