feat(database): add functions for DB and DB-table creation

lib/transport_helper.dart

@@ -1,3 +1,24 @@
+import 'package:sqflite/sqflite.dart';
+
+void initDB(dbName) async {
+  var databasesPath = await getDatabasesPath();
+  var path = databasesPath + dbName;
+  var db = await openDatabase(path);
+  // var db = await openDatabase('/var/db/oeffimaster/transport_db.db');
+
+  // TODO: Make sure the directory exists
+
+  // TODO: future optimisation: batch transactions
+
+  // TODO: create tables for all classes
+  // - [] route
+  // - [] segment
+  // - [] station
+  // - [] vehicle
+  // - [] line
+  // - [] departure
+}
+
 class Route {
   List<Segment> segments = List.empty();
   Duration duration = Duration(minutes: 0);
@@ -15,6 +36,10 @@ class Route {
         json["LegList"]["Leg"][0]["Origin"]["time"],
   );
 
+  // TODO: do we need route in the database???? // what beyond and ID is needed?
+  void initRouteTable(Database database) async {
+    database.execute("CREATE TABLE IF NOT EXISTS route();");
+  }
 }
 
 class Segment {
@@ -39,22 +64,36 @@ class Segment {
     endTime: json["Destination"]["rtTime"],
     vehicle: Vehicle.fromJson(json["Product"]),
   );
+
+  void initSegmentTable(Database database) async {
+    database.execute("""
+    CREATE TABLE IF NOT EXISTS segment(
+    startpoint  TEXT,
+    endpoint    TEXT,
+    starttime   TEXT,
+    endtime     TEXT,
+    vehicle     INTEGER,
+    FOREIGN KEY(startpoint) REFERENCES station(stationid),
+    FOREIGN KEY(endpoint) REFERENCES station(stationid)
+    FOREIGN KEY(vehicle) REFERENCES vehicle(vehicleid)
+    );
+    """);
+  }
 }
 
 class Station {
-  final String id;
+  final String stationId;
   final String name;
-  List<Line>? transportLines;
-  List<Departure>? departures;
+  List<Line>? transportLines; // could be normalized away
 
   Station({
-    required this.id,
+    required this.stationId,
     required this.name,
-    required this.transportLines
+    required this.transportLines, //TODO: make extra db table
   });
 
   factory Station.fromJson(Map<String, dynamic> json) => Station(
-    id: json["id"] as String? ?? json["extId"] as String,
+    stationId: json["id"] as String? ?? json["extId"] as String,
     name: json["name"],
     transportLines: json.containsKey("productAtStop")
         ? json["productAtStop"].map(
@@ -62,27 +101,44 @@ class Station {
           )
         : const [],
   );
+
+  void initStationTable(Database database) async {
+    database.execute("""CREATE TABLE IF NOT EXISTS station(
+      stationid TEXT PRIMARY KEY,
+      name      TEXT
+    );
+    """);
+  }
 }
 
 class Vehicle {
-  final String id;
+  final String vehicleId;
   final Line line;
 
   Vehicle({
-    required this.id,
+    required this.vehicleId,
     required this.line,
   });
 
   // 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"],
+    vehicleId: json["matchId"],
     line: Line.fromJson(json),
   );
+
+  void initVehicleTable(Database database) async {
+    database.execute("""CREATE TABLE IF NOT EXISTS vehicle(
+      vehicleid TEXT PRIMARY KEY,
+      line      TEXT,
+      FOREIGN KEY(line) REFERENCES line(lineid)
+    );
+    """);
+  }
 }
 
 class Line {
-  final String id;
+  final String lineId;
   Station? destination;
   Station? direction;
   final VehicleType mode;
@@ -91,7 +147,7 @@ class Line {
   Color? bgColor;
 
   Line({
-    required this.id,
+    required this.lineId,
     required this.name,
     required this.mode,
     this.fgColor,
@@ -103,18 +159,32 @@ class Line {
     VehicleType.metro,
     VehicleType.subway,
     VehicleType.PLACEHOLDER,
-    VehicleType.bus
+    VehicleType.bus,
   ];
 
   factory Line.fromJson(Map<String, dynamic> json) => Line(
-    id: json["lineId"],
+    lineId: json["lineId"],
     name: json["name"],
     mode: _vehicleTypeAsCatCode[int.parse(json["catCode"])],
-    fgColor: Color.fromJson(json["foregroundColor"]) as Color?
-        ?? Color(r: 255, g: 255, b: 255), // fallback
-    bgColor: Color.fromJson(json["backgroundColor"]) as Color?
-        ?? Color(r: 50, g: 50, b: 50), // fallback
+    fgColor:
+        Color.fromJson(json["foregroundColor"]) as Color? ??
+        Color(r: 255, g: 255, b: 255), // fallback
+    bgColor:
+        Color.fromJson(json["backgroundColor"]) as Color? ??
+        Color(r: 50, g: 50, b: 50), // fallback
   );
+  void initLineTable(Database database) async {
+    database.execute("""CREATE TABLE IF NOT EXISTS line(
+      lineid      TEXT PRIMARY KEY,
+      destination TEXT,
+      direction   TEXT,
+      mode        TEXT,
+      name        TEXT,
+      fgcolor     TEXT,
+      bgcolor     TEXT
+    );
+    """);
+  }
 }
 
 class Departure {
@@ -128,6 +198,18 @@ class Departure {
     required this.station,
     required this.departureTime,
   });
+
+  void initDepartureTable(Database database) async {
+    database.execute("""CREATE TABLE IF NOT EXISTS departure(
+      departureid     INTEGER,
+      vehicle         TEXT,
+      station         TEXT,
+      departuretime   TEXT
+      FOREIGN KEY(vehicle) REFERENCES vehicle(vehicleid),
+      FOREIGN KEY(station) REFERENCES station(stationid)
+     );
+     """);
+  }
 }
 
 class Color {