feat(json import): add fromJson to missing classes and connect them

lib/transport_helper.dart

@@ -1,3 +1,46 @@
+class Route {
+  List<Segment> segments = List.empty();
+  Duration duration = Duration(minutes: 0);
+
+  Route({
+    required this.segments,
+    required this.duration,
+  });
+
+  // from trip API request
+
+  factory Route.fromJson(Map<String, dynamic> json) => Route(
+    segments: json["Leglist"]["Leg"].map((leg) => Segment.fromJson(leg)),
+    duration: json["LegList"]["Leg"][-1]["Origin"]["time"] -
+        json["LegList"]["Leg"][0]["Origin"]["time"],
+  );
+
+}
+
+class Segment {
+  final Station startPoint;
+  final Station endPoint;
+  final DateTime startTime;
+  final DateTime endTime;
+  final Vehicle vehicle;
+
+  Segment({
+    required this.startPoint,
+    required this.endPoint,
+    required this.startTime,
+    required this.endTime,
+    required this.vehicle,
+  });
+
+  factory Segment.fromJson(Map<String, dynamic> json) => Segment(
+    startPoint: Station.fromJson(json["Origin"]),
+    endPoint: Station.fromJson(json["Destination"]),
+    startTime: json["Origin"]["rtTime"],
+    endTime: json["Destination"]["rtTime"],
+    vehicle: Vehicle.fromJson(json["Product"]),
+  );
+}
+
 class Station {
   final String id;
   final String name;
@@ -22,16 +65,19 @@ class Station {
 
 class Vehicle {
   final String id;
-  final String name;
+  final Line line;
-  final List<Departure>? departures;
 
   Vehicle({
     required this.id,
-    required this.name,
+    required this.line,
-    required this.departures
   });
 
-  factory Vehicle.fromJson(Map<String, dynamic> json)
+  // we can use the "product" class from within any JSON response
+  // (within hafas API, on the appropriate level)
+  factory Vehicle.fromJson(Map<String, dynamic> json) => Vehicle(
+    id: json["matchId"],
+    line: Line.fromJson(json),
+  );
 }
 
 class Line {
@@ -51,6 +97,7 @@ class Line {
     this.bgColor,
   });
 
+  // TODO: EXPLAIN!!!!!!!!!!!!
   static const _vehicleTypeAsCatCode = [
     VehicleType.metro,
     VehicleType.subway,