feat(departures): make some adaptations to supp diff departure srces

with these adaptations to the api_handler and Departure.fromJson,
the fromJson-factory now works for responses from both /departureBoard
and /tripDetail

for /tripDetail a little json-copying is used, see
ApiHandler._expandDeparturesJson

lib/api_handler.dart

@@ -218,10 +218,30 @@ class ApiHandler {
         json.decode(jsonResponse.body) as Map<String, dynamic>;
     final DepartureList = httpPackageJson["Stops"]["Stop"]
         .map(
-          (x) => Departure.fromJson(x),
+          (x) => Departure.fromJson(
+            // needed because I'm too lazy to write a second mostly identical
+            // constructor and a wrapper
+            _expandDeparturesJson(httpPackageJson, x, ["ref", "Product"]),
+          ),
         )
         .toList()
         .cast<Departure>();
     return DepartureList;
   }
+
+  // workaround for the fact that json from tripDetail and DepartureBoard are
+  // quite different from each other in their structure... but I don't wish to
+  // build a second constructor >:(
+  // so this function duplicates topLevel Maps into a lower level to be used in
+  // mapping functions and such
+  static Map<String, dynamic> _expandDeparturesJson(
+    Map<String, dynamic> topLevelJson,
+    Map<String, dynamic> subLevelJson,
+    List<String> topLevelKeys,
+  ) {
+    for (final String entry in topLevelKeys) {
+      subLevelJson[entry] = topLevelJson[entry];
+    }
+    return subLevelJson;
+  }
 }

lib/main.dart

@@ -348,7 +348,7 @@ class _ChooseArrivalPageState extends State<ChooseArrivalPage> {
             Expanded(
               child: SizedBox(
                 height: 400,
-                child: DepartureList(
+                child: ArrivalList(
                   departureList: departureList,
                   onTapped: _handleArrivalTapped,
                 ),
@@ -398,7 +398,7 @@ class ArrivalList extends StatelessWidget {
       children: [
         for (Departure departure in departureList)
           ListTile(
-            title: Text(departure.stationId),
+            title: Text(departure.stationName),
             subtitle: Text(departure.arrivalTime.toString()),
             onTap: () => onTapped(departure),
           ),

lib/transport_helper.dart

@@ -824,16 +824,32 @@ class Departure {
     );
   }
 
+  // this function is built to construct from different json sources
+  // for our hafas api, that means requests to both /departureBoard and /tripDetail
+  // sources from departureBoard were the default, but with some adaptations,
+  // tripDetail is a working source too, with the following workarounds:
+  //
+  // tripDetail has stops as list in a sublevel, whereas "ref", and "Product"
+  // are in the top Level.
+  // stop/station infos on the other hand just use different keys
+  // Therefore this function uses some catches to serve both cases and needs to
+  // be served a somewhat expanded json Map, as seen in
+  // ApiHander._expandDeparturesJson, which copies the topLevel fields into the
+  // repeated "Stop" entries that this function takes as json param
   factory Departure.fromJson(Map<String, dynamic> json) {
     Vehicle vehicle = Vehicle.fromJson(json["Product"][0]);
     vehicle.dbInsert();
     Station station = Station(
-      id: json["stopid"],
-      name: json["stop"],
+      id: json["stopid"] ?? json["id"],
+      name: json["stop"] ?? json["name"],
       transportLines: [],
     );
     station.dbInsert();
 
+    // sometimes no arrivalTime exists, e.g. on the first station in a list
+    // and sometimes no departureTime, as for the last station...
+    // we might in these cases not need to ask for them, but I like a little
+    // redundancy more than handling null values
     DateTime? arrDateTime;
     String? arrivalDate = json["arrDate"];
     String? arrivalTime = json["arrTime"];
@@ -849,7 +865,10 @@ class Departure {
     }
 
     return Departure(
-      ref: json["JourneyDetailRef"]["ref"],
+      // asking for tripDetail version first because
+      // ["JourneyDetailRef"]["ref"] cannot be caught if ["JourneyDetailRef"]
+      // is non-existent
+      ref: json["ref"] ?? json["JourneyDetailRef"]["ref"] as String,
       vehicleId: vehicle.id,
       vehicleName: vehicle.name,
       stationId: station.id,