Working "find a path" code (#13)

The client first requests stops from the TS server (`0.0.0.0:80`), then the path from the Dart server (`localhost:8001`). It will be trivial to move the TS logic to the Dart server since the Dart server is the one that parsed all that data, and it's anyway in a `JSON` file. 

There is a `server/GET_ROUTES.json` file, but it's not needed. I just included it for easier debugging. `server/GET_STOPS.json` includes both the stops and the routes, and the client does some (inefficient) work to re-organize it.

The Dart server uses a basic A* implementation to sort find direct routes and routes with transfers. The A* logic is in `src/shared/lib/src/graph/graph.dart`. This file defines the state itself, and `package:a_star` on Pub.dev (mine) defines the algorithm. `src/shared/bin/path.dart` is the whole of the Dart server. 

TODO: 
- add unit tests
- this PR breaks almost nothing, so there is duplicate work being done on the client and some unused logic
- return a structured path object for the client to use as it wants. This PR just sends a well-formatted string

src/.gitignore

@@ -1 +1,3 @@
 *.env
+pubspec.lock
+.dart_tool

src/client/lib/src/services/api.dart

@@ -1,6 +1,7 @@
 import "package:flutter/foundation.dart" show debugPrint, kDebugMode;
 
 import "package:client/data.dart";
+import "package:http/http.dart" as http;
 
 import "api_client.dart";
 import "service.dart";
@@ -41,6 +42,28 @@ class ApiService extends Service {
     PathStep.fromJson,
   );
 
+  Future<String?> getPath2({
+    required Coordinates start,
+    required Coordinates end,
+  }) async {
+    final uri = Uri.parse("http://localhost:8001/path").replace(
+      queryParameters: {
+        "start_lat": start.lat.toString(),
+        "start_lon": start.long.toString(),
+        "end_lat": end.lat.toString(),
+        "end_lon": end.long.toString(),
+      },
+    );
+    try {
+      final response = await http.get(uri);
+      return response.body;
+    // Any error should show null
+    // ignore: avoid_catches_without_on_clauses
+    } catch (error) {
+      return null;
+    }
+  }
+
   Future<List<Stop>?> getStops() => _client.getJsonList(
     _base.resolve("stops"),
     Stop.fromJson,

src/client/lib/src/services/api_client.dart

@@ -1,6 +1,7 @@
 import "dart:convert";
 
 import "package:client/data.dart";
+import "package:flutter/foundation.dart";
 import "package:http/http.dart" as http;
 
 class ApiClient {
@@ -19,9 +20,10 @@ class ApiClient {
         for (final json in listOfJson)
           fromJson(json),
       ];
+    // Want to catch all errors for the UI
+    // ignore: avoid_catches_without_on_clauses
     } catch (error, stackTrace) {
-      // ignore: avoid_print
-      print("Error: $error\n$stackTrace");
+      debugPrint("Error: $error\n$stackTrace");
       return null;
     }
   }

src/client/lib/src/view_models/home.dart

@@ -64,6 +64,7 @@ class HomeModel extends ViewModel with HomeMarkers {
     super.updateEnd(coordinates, marker);
   }
 
+  String? pathText;
   Future<void> search() async {
     final start = (lat: startLatitude, long: startLongitude);
     final end = (lat: endLatitude, long: endLongitude);
@@ -71,16 +72,17 @@ class HomeModel extends ViewModel with HomeMarkers {
     if (end.lat == null || end.long == null) return;
     isSearching = true;
     isLoading = true;
-    final result = await services.api.getPath(start: start as Coordinates, end: end as Coordinates);
-    path = result;
+    final result = await services.api.getPath2(start: start as Coordinates, end: end as Coordinates);
+    pathText = result ?? "An error occurred";
+    // path = result;
     isLoading = false;
     if (result == null) return;
     isSearching = false;
-    routes = [
-      for (final step in result) [
-        ...decodePolyline(step.trip.polyline),
-      ],
-    ];
+    // routes = [
+    //   for (final step in result) [
+    //     ...decodePolyline(step.trip.polyline),
+    //   ],
+    // ];
     notifyListeners();
   }
 }

src/client/lib/src/view_models/home_markers.dart

@@ -78,12 +78,11 @@ mixin HomeMarkers on ChangeNotifier {
         stopCounts[route] ??= 0;
         stopCounts[route] = stopCounts[route]! + 1;
       }
-
-      if (stop.provider.contains("OCCT")) {
-        occtRouteNames.addAll(stop.routes);
-      } else {
-        bcRouteNames.addAll(stop.routes);
-      }
+      final namesList = switch (stop.provider) {
+        Provider.occt => occtRouteNames,
+        Provider.bc => bcRouteNames,
+      };
+      namesList.addAll(stop.routes);
     }
     notifyListeners();
   }

src/client/lib/src/widgets/sidebar.dart

@@ -32,27 +32,29 @@ class Sidebar extends ReusableReactiveWidget<HomeModel> {
                 Tab(text: provider),
             ],
           ),
-          Expanded(
-            child: !model.shouldShowMarkers
-              ? const Center(child: Text("Choose start or end location"))
-              : TabBarView(
-                  children: [
-                    for (final (_, routesList) in model.providers)
-                      ListView(
-                        children: [
-                          for (final route in routesList) CheckboxListTile(
-                            title: Text(route, maxLines: 1),
-                            subtitle: Text(
-                              "${model.stopCounts[route] ?? 0} stops",
-                              maxLines: 1,
-                            ),
-                            value: model.routesToShow.contains(route),
-                            onChanged: (value) => model.showRoute(route, shouldShow: value!),
-                          ),
-                        ],
+          if (!model.shouldShowMarkers && model.pathText != null)
+            Center(child: Text(model.pathText!, style: context.textTheme.bodySmall)),
+          if (!model.shouldShowMarkers && model.pathText == null)
+            const Center(child: Text("Choose start or end location")),
+          if (model.shouldShowMarkers) Expanded(
+            child: TabBarView(
+              children: [
+                for (final (_, routesList) in model.providers)
+                  ListView(
+                    children: [
+                      for (final route in routesList) CheckboxListTile(
+                        title: Text(route, maxLines: 1),
+                        subtitle: Text(
+                          "${model.stopCounts[route] ?? 0} stops",
+                          maxLines: 1,
+                        ),
+                        value: model.routesToShow.contains(route),
+                        onChanged: (value) => model.showRoute(route, shouldShow: value!),
                       ),
-                  ],
-                ),
+                    ],
+                  ),
+              ],
+            ),
           ),
         ],
       ),

src/client/pubspec.lock

@@ -1,433 +0,0 @@
-# Generated by pub
-# See https://dart.dev/tools/pub/glossary#lockfile
-packages:
-  args:
-    dependency: transitive
-    description:
-      name: args
-      sha256: d0481093c50b1da8910eb0bb301626d4d8eb7284aa739614d2b394ee09e3ea04
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.7.0"
-  async:
-    dependency: transitive
-    description:
-      name: async
-      sha256: d2872f9c19731c2e5f10444b14686eb7cc85c76274bd6c16e1816bff9a3bab63
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.12.0"
-  boolean_selector:
-    dependency: transitive
-    description:
-      name: boolean_selector
-      sha256: "8aab1771e1243a5063b8b0ff68042d67334e3feab9e95b9490f9a6ebf73b42ea"
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.1.2"
-  build_cli_annotations:
-    dependency: transitive
-    description:
-      name: build_cli_annotations
-      sha256: b59d2769769efd6c9ff6d4c4cede0be115a566afc591705c2040b707534b1172
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.1.0"
-  characters:
-    dependency: transitive
-    description:
-      name: characters
-      sha256: f71061c654a3380576a52b451dd5532377954cf9dbd272a78fc8479606670803
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.4.0"
-  clock:
-    dependency: transitive
-    description:
-      name: clock
-      sha256: fddb70d9b5277016c77a80201021d40a2247104d9f4aa7bab7157b7e3f05b84b
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.1.2"
-  collection:
-    dependency: transitive
-    description:
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-      url: "https://pub.dev"
-    source: hosted
-    version: "1.19.1"
-  convert:
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-  csslib:
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-    version: "1.0.2"
-  csv:
-    dependency: "direct main"
-    description:
-      name: csv
-      sha256: c6aa2679b2a18cb57652920f674488d89712efaf4d3fdf2e537215b35fc19d6c
-      url: "https://pub.dev"
-    source: hosted
-    version: "6.0.0"
-  dhttpd:
-    dependency: "direct dev"
-    description:
-      name: dhttpd
-      sha256: "2e24765d7569b8e0a02a441e3cf96f09cca69dfecba646e7e9f6b3ab45a2f3fe"
-      url: "https://pub.dev"
-    source: hosted
-    version: "4.1.0"
-  fake_async:
-    dependency: transitive
-    description:
-      name: fake_async
-      sha256: "6a95e56b2449df2273fd8c45a662d6947ce1ebb7aafe80e550a3f68297f3cacc"
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.3.2"
-  fixnum:
-    dependency: "direct main"
-    description:
-      name: fixnum
-      sha256: b6dc7065e46c974bc7c5f143080a6764ec7a4be6da1285ececdc37be96de53be
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.1.1"
-  flutter:
-    dependency: "direct main"
-    description: flutter
-    source: sdk
-    version: "0.0.0"
-  flutter_plugin_android_lifecycle:
-    dependency: transitive
-    description:
-      name: flutter_plugin_android_lifecycle
-      sha256: "5a1e6fb2c0561958d7e4c33574674bda7b77caaca7a33b758876956f2902eea3"
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.0.27"
-  flutter_test:
-    dependency: "direct dev"
-    description: flutter
-    source: sdk
-    version: "0.0.0"
-  flutter_web_plugins:
-    dependency: transitive
-    description: flutter
-    source: sdk
-    version: "0.0.0"
-  go_router:
-    dependency: "direct main"
-    description:
-      name: go_router
-      sha256: f02fd7d2a4dc512fec615529824fdd217fecb3a3d3de68360293a551f21634b3
-      url: "https://pub.dev"
-    source: hosted
-    version: "14.8.1"
-  google_maps:
-    dependency: transitive
-    description:
-      name: google_maps
-      sha256: "4d6e199c561ca06792c964fa24b2bac7197bf4b401c2e1d23e345e5f9939f531"
-      url: "https://pub.dev"
-    source: hosted
-    version: "8.1.1"
-  google_maps_flutter:
-    dependency: "direct main"
-    description:
-      name: google_maps_flutter
-      sha256: b42ff7f3875a5eedbe388d883100561b85c62beed1c39ad66dd60537c75bb424
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.12.0"
-  google_maps_flutter_android:
-    dependency: transitive
-    description:
-      name: google_maps_flutter_android
-      sha256: "0ede4ae8326335c0c007c8c7a8c9737449263123385e2bdf49f3e71103b2dc2e"
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.16.0"
-  google_maps_flutter_ios:
-    dependency: transitive
-    description:
-      name: google_maps_flutter_ios
-      sha256: ef72c822930ce69515cb91c10cd88cfb8b26296f765808a43cbc9a10eaffacfe
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.15.0"
-  google_maps_flutter_platform_interface:
-    dependency: transitive
-    description:
-      name: google_maps_flutter_platform_interface
-      sha256: "970c8f766c02909c7be282dea923c971f83a88adaf07f8871d0aacebc3b07bb2"
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.11.1"
-  google_maps_flutter_web:
-    dependency: transitive
-    description:
-      name: google_maps_flutter_web
-      sha256: a45786ea6691cc7cdbe2cf3ce2c2daf4f82a885745666b4a36baada3a4e12897
-      url: "https://pub.dev"
-    source: hosted
-    version: "0.5.12"
-  html:
-    dependency: "direct main"
-    description:
-      name: html
-      sha256: "1fc58edeaec4307368c60d59b7e15b9d658b57d7f3125098b6294153c75337ec"
-      url: "https://pub.dev"
-    source: hosted
-    version: "0.15.5"
-  http:
-    dependency: "direct main"
-    description:
-      name: http
-      sha256: fe7ab022b76f3034adc518fb6ea04a82387620e19977665ea18d30a1cf43442f
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.3.0"
-  http_parser:
-    dependency: transitive
-    description:
-      name: http_parser
-      sha256: "178d74305e7866013777bab2c3d8726205dc5a4dd935297175b19a23a2e66571"
-      url: "https://pub.dev"
-    source: hosted
-    version: "4.1.2"
-  leak_tracker:
-    dependency: transitive
-    description:
-      name: leak_tracker
-      sha256: c35baad643ba394b40aac41080300150a4f08fd0fd6a10378f8f7c6bc161acec
-      url: "https://pub.dev"
-    source: hosted
-    version: "10.0.8"
-  leak_tracker_flutter_testing:
-    dependency: transitive
-    description:
-      name: leak_tracker_flutter_testing
-      sha256: f8b613e7e6a13ec79cfdc0e97638fddb3ab848452eff057653abd3edba760573
-      url: "https://pub.dev"
-    source: hosted
-    version: "3.0.9"
-  leak_tracker_testing:
-    dependency: transitive
-    description:
-      name: leak_tracker_testing
-      sha256: "6ba465d5d76e67ddf503e1161d1f4a6bc42306f9d66ca1e8f079a47290fb06d3"
-      url: "https://pub.dev"
-    source: hosted
-    version: "3.0.1"
-  logging:
-    dependency: transitive
-    description:
-      name: logging
-      sha256: c8245ada5f1717ed44271ed1c26b8ce85ca3228fd2ffdb75468ab01979309d61
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.3.0"
-  matcher:
-    dependency: transitive
-    description:
-      name: matcher
-      sha256: dc58c723c3c24bf8d3e2d3ad3f2f9d7bd9cf43ec6feaa64181775e60190153f2
-      url: "https://pub.dev"
-    source: hosted
-    version: "0.12.17"
-  material_color_utilities:
-    dependency: transitive
-    description:
-      name: material_color_utilities
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-      url: "https://pub.dev"
-    source: hosted
-    version: "0.11.1"
-  meta:
-    dependency: transitive
-    description:
-      name: meta
-      sha256: e3641ec5d63ebf0d9b41bd43201a66e3fc79a65db5f61fc181f04cd27aab950c
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.16.0"
-  mime:
-    dependency: transitive
-    description:
-      name: mime
-      sha256: "41a20518f0cb1256669420fdba0cd90d21561e560ac240f26ef8322e45bb7ed6"
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.0.0"
-  path:
-    dependency: transitive
-    description:
-      name: path
-      sha256: "75cca69d1490965be98c73ceaea117e8a04dd21217b37b292c9ddbec0d955bc5"
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.9.1"
-  plugin_platform_interface:
-    dependency: transitive
-    description:
-      name: plugin_platform_interface
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-      url: "https://pub.dev"
-    source: hosted
-    version: "2.1.8"
-  polyline_tools:
-    dependency: "direct main"
-    description:
-      name: polyline_tools
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-  sanitize_html:
-    dependency: transitive
-    description:
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-  shared:
-    dependency: "direct main"
-    description:
-      path: "../shared"
-      relative: true
-    source: path
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-  shelf:
-    dependency: transitive
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-    version: "0.0.0"
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-    version: "14.3.1"
-  web:
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-    source: hosted
-    version: "1.1.1"
-sdks:
-  dart: ">=3.7.0 <4.0.0"
-  flutter: ">=3.27.0"

src/client/pubspec.yaml

@@ -6,6 +6,7 @@ version: 0.1.0+1
 environment:
   sdk: ^3.5.0
 
+resolution: workspace
 dependencies:
   fixnum: ^1.1.1
   csv: ^6.0.0
@@ -24,7 +25,6 @@ dev_dependencies:
   dhttpd: ^4.1.0
   flutter_test:
     sdk: flutter
-  very_good_analysis: ^6.0.0
 
 flutter:
   uses-material-design: true

src/client/test/widget_test.dart

@@ -1,30 +0,0 @@
-// This is a basic Flutter widget test.
-//
-// To perform an interaction with a widget in your test, use the WidgetTester
-// utility in the flutter_test package. For example, you can send tap and scroll
-// gestures. You can also use WidgetTester to find child widgets in the widget
-// tree, read text, and verify that the values of widget properties are correct.
-
-import 'package:flutter/material.dart';
-import 'package:flutter_test/flutter_test.dart';
-
-import 'package:client/main.dart';
-
-void main() {
-  testWidgets('Counter increments smoke test', (WidgetTester tester) async {
-    // Build our app and trigger a frame.
-    await tester.pumpWidget(const MyApp());
-
-    // Verify that our counter starts at 0.
-    expect(find.text('0'), findsOneWidget);
-    expect(find.text('1'), findsNothing);
-
-    // Tap the '+' icon and trigger a frame.
-    await tester.tap(find.byIcon(Icons.add));
-    await tester.pump();
-
-    // Verify that our counter has incremented.
-    expect(find.text('0'), findsNothing);
-    expect(find.text('1'), findsOneWidget);
-  });
-}

src/pubspec.yaml

@@ -0,0 +1,10 @@
+name: cs445
+
+environment:
+  sdk: ^3.7.0
+
+workspace:
+  - shared
+  - client
+dev_dependencies:
+  very_good_analysis: ^7.0.0

src/shared/analysis_options.yaml

@@ -1,52 +0,0 @@
-# This file configures the analyzer, which statically analyzes Dart code to
-# check for errors, warnings, and lints. See the following for docs:
-# https://dart.dev/guides/language/analysis-options
-#
-# The issues identified by the analyzer are surfaced in the UI of Dart-enabled
-# IDEs (https://dart.dev/tools#ides-and-editors). The analyzer can also be
-# invoked from the command line by running `flutter analyze`.
-include: package:very_good_analysis/analysis_options.yaml  # has more lints
-
-analyzer:
-  language:
-    # Strict casts isn't helpful with null safety. It only notifies you on `dynamic`,
-    # which happens all the time in JSON.
-    #
-    # See https://github.com/dart-lang/language/blob/main/resources/type-system/strict-casts.md
-    strict-casts: false
-
-    # Don't let any types be inferred as `dynamic`.
-    #
-    # See https://github.com/dart-lang/language/blob/main/resources/type-system/strict-inference.md
-    strict-inference: true
-
-    # Don't let Dart infer the wrong type on the left side of an assignment.
-    #
-    # See https://github.com/dart-lang/language/blob/main/resources/type-system/strict-raw-types.md
-    strict-raw-types: true
-
-  exclude:
-    - lib/generated/**.dart
-    - test/**.dart
-    - example/**.dart
-
-linter:
-  rules:
-    # Rules NOT in package:very_good_analysis
-    prefer_double_quotes: true
-    prefer_expression_function_bodies: true
-
-    # Rules to be disabled from package:very_good_analysis
-    prefer_single_quotes: false  # prefer_double_quotes
-    lines_longer_than_80_chars: false  # lines should be at most 100 chars
-    sort_pub_dependencies: false  # Sort dependencies by function
-    use_key_in_widget_constructors: false  # not in Flutter apps
-    directives_ordering: false  # sort dart, then flutter, then package imports
-    always_use_package_imports: false  # not when importing sibling files
-    sort_constructors_first: false  # final properties, then constructor
-    avoid_dynamic_calls: false  # this lint takes over errors in the IDE
-    one_member_abstracts: false  # abstract classes are good for interfaces
-    cascade_invocations: false  # cascades are often harder to read
-
-    # Temporarily disabled until we are ready to document
-    public_member_api_docs: false

src/shared/bin/data.dart

@@ -1,6 +1,6 @@
 import "package:shared/generator.dart";
 
 void main() async {
-  final stops = StopGenerator();
-  await stops.generate();
+  await Generator.stops.generate();
+  await Generator.routes.generate();
 }

src/shared/bin/path.dart

@@ -0,0 +1,147 @@
+// User-facing script
+// ignore_for_file: avoid_print
+
+import "package:a_star/a_star.dart";
+import "package:shared/generator.dart";
+import "package:shared/graph.dart";
+
+import "package:shelf_router/shelf_router.dart";
+import "package:shelf/shelf.dart";
+import "package:shelf/shelf_io.dart" as io;
+
+// const startLat = 42.0924949645996;
+// const startLong = -75.9538421630859;
+// const endLat = 42.0869369506836;
+// const endLong = -75.965934753418;
+
+const startLat = 42.092083;
+const startLong = -75.952271;
+const endLat = 42.080822;
+const endLong = -75.912529;
+
+const numStops = 5;
+
+void log(String message) {
+  // print(message);
+}
+
+Iterable<Stop> findStopsNear(Coordinates location) {
+  log("Finding stops near $location...");
+  final stopDistances = [
+    for (final stop in StopState.stops.values)
+      (stop, stop.coordinates.distanceTo(location)),
+  ];
+  stopDistances.sort((a, b) => a.$2.compareTo(b.$2));
+  return stopDistances.take(numStops).map((pair) => pair.$1);
+}
+
+void printStops(Iterable<Stop> stops) {
+  log("Found stops:");
+  for (final stop in stops) {
+    log("- ${stop.routes}, ${stop.name}");
+  }
+}
+
+Set<RouteID> findRoutes(Iterable<Stop> stops) => {
+  for (final stop in stops)
+    ...stop.routeIDs,
+};
+
+Stop findStopWithRoute(Iterable<Stop> stops, RouteID route) =>
+  stops.firstWhere((stop) => stop.routeIDs.contains(route));
+
+Future<void> init() async {
+  print("Initializing...");
+  final stops = await Generator.stops.parse();
+  final routes = await Generator.routes.parse();
+  StopState.init(routes, stops);
+}
+
+final headers = {
+  "Access-Control-Allow-Origin": "*",
+};
+
+Future<Response> handleRequest(Request request) async {
+  final startLat = double.tryParse(request.url.queryParameters["start_lat"] ?? "");
+  final startLong = double.tryParse(request.url.queryParameters["start_lon"] ?? "");
+  final endLat = double.tryParse(request.url.queryParameters["end_lat"] ?? "");
+  final endLong = double.tryParse(request.url.queryParameters["end_lon"] ?? "");
+  if (startLat == null || startLong == null || endLat == null || endLong == null) {
+    return Response.badRequest(body: "Could not parse coordinates", headers: headers);
+  }
+
+  final start = (lat: startLat, long: startLong);
+  final end = (lat: endLat, long: endLong);
+
+  // 1) Find [numStops] nearest stops by the given locations
+  log("Finding nearest stops...");
+  final startStops = findStopsNear(start);
+  printStops(startStops);
+  final endStops = findStopsNear(end);
+  printStops(endStops);
+
+  // 2) Find all routes by those stops
+  log("Finding intersecting routes");
+  final startRoutes = findRoutes(startStops);
+  final endRoutes = findRoutes(endStops);
+  log("Start routes: $startRoutes");
+  log("End routes: $endRoutes");
+
+  // 3) Check for a direct route without transfers
+  final routesInCommon = startRoutes.intersection(endRoutes);
+  if (routesInCommon.isNotEmpty) {
+    final route = routesInCommon.first;
+    final startStop = findStopWithRoute(startStops, route);
+    final endStop = findStopWithRoute(endStops, route);
+    return Response.ok("\nBoard the $route at ${startStop.name} and get off at ${endStop.name}", headers: headers);
+  }
+
+  // 4) Use A* to find a route with transfers
+  log("Using A*");
+  final paths = <Iterable<StopState>>[];
+  for (final startStop in startStops) {
+    for (final startRoute in startStop.routeIDs) {
+      for (final endStop in endStops) {
+        final state = StopState(stopID: startStop.id, goalID: endStop.id, routeID: startRoute, depth: 0);
+        log("Finding a route using ${state.hash()}");
+        final result = aStar(state);
+        if (result == null) continue;
+        paths.add(result.reconstructPath());
+      }
+    }
+  }
+
+  if (paths.isEmpty) {
+    return Response.ok("No routes found", headers: headers);
+  }
+
+  final minPath = paths.min((path) => path.length);
+  final buffer = StringBuffer();
+  buffer.writeln("Found ${paths.length} paths, here's the best one with only ${minPath.length} steps:");
+  StopState? prevStep;
+  var index = 0;
+  for (final step in minPath) {
+    index++;
+    final stop = StopState.stops[step.stopID]!;
+    final route = StopState.routes[step.routeID]!;
+    if (prevStep == null) {
+      buffer.writeln("$index. Board the ${route.provider.humanName} ${route.fullName} bus\n  at ${stop.name}");
+    } else if (index == minPath.length) {
+      buffer.writeln("$index. Get off at ${stop.name}");
+    } else if (prevStep.routeID != step.routeID) {
+      buffer.writeln("$index. Transfer to the ${route.provider.humanName} ${route.fullName}");
+    } else {
+      buffer.writeln("$index. Go to ${stop.name}");
+    }
+    prevStep = step;
+  }
+  return Response.ok(buffer.toString(), headers: headers);
+}
+
+void main() async {
+  await init();
+  final router = Router();
+  router.get("/path", handleRequest);
+  await io.serve(router.call, "localhost", 8001);
+  print("Listening on localhost:8001");
+}

src/shared/lib/data.dart

@@ -1,2 +1,4 @@
-export "src/utils.dart";
-export "src/stops/stop.dart";
+export "src/data/provider.dart";
+export "src/data/route.dart";
+export "src/data/stop.dart";
+export "src/data/utils.dart";

src/shared/lib/generator.dart

@@ -1,2 +1,6 @@
-export "src/generator_utils.dart";
-export "src/stops/generator.dart";
+export "src/generator/generator.dart";
+export "src/generator/routes_bc.dart";
+export "src/generator/routes_occt.dart";
+export "src/generator/stops_bc.dart";
+export "src/generator/stops_occt.dart";
+export "src/generator/utils.dart";

src/shared/lib/graph.dart

@@ -0,0 +1 @@
+export "src/graph/state.dart";

src/shared/lib/shared.dart

@@ -1,2 +0,0 @@
-export "src/stops/stop.dart";
-export "src/utils.dart";

src/shared/lib/src/data/provider.dart

@@ -0,0 +1,11 @@
+enum Provider {
+  bc("BCT", "BC Transit"),
+  occt("OCCT", "OCC Transport");
+
+  const Provider(this.id, this.humanName);
+
+  factory Provider.fromJson(String json) => values.firstWhere((value) => value.id == json);
+
+  final String id;
+  final String humanName;
+}

src/shared/lib/src/data/route.dart

@@ -0,0 +1,55 @@
+import "provider.dart";
+import "stop.dart";
+import "utils.dart";
+
+extension type RouteID._(String id) {
+  RouteID(Provider provider, Object json) :
+    id = "${provider.id}_$json";
+
+  RouteID.fromJson(dynamic json) : id = json.toString();
+  factory RouteID.fromBcCsv(CsvRow csv) => RouteID(Provider.bc, csv[0]);
+
+  RouteID withDirection(String direction) => RouteID._("${id}_$direction");
+}
+
+class Route with Encodable {
+  final RouteID id;
+  final Provider provider;
+  final String fullName;
+  final String shortName;
+  final List<StopID> stops;
+
+  const Route({
+    required this.id,
+    required this.provider,
+    required this.stops,
+    required this.fullName,
+    required this.shortName,
+  });
+
+  Route.fromOcctJson(Json json) :
+    id = RouteID(Provider.occt, json["id"]),
+    provider = Provider.occt,
+    shortName = json["abbr"],
+    fullName = json["name"],
+    stops = [
+      for (final stopID in (json["stops"] as List).cast<int>())
+        StopID(stopID.toString()),
+    ];
+
+  Route.fromBcCsv(CsvRow csv) :
+    id = RouteID.fromBcCsv(csv),
+    provider = Provider.bc,
+    shortName = csv[2],
+    fullName = "${csv[2]}) ${csv[3]}",
+    stops = [];
+
+  @override
+  Json toJson() => {
+    "id": id,
+    "provider": provider.id,
+    "full_name": fullName,
+    "short_name": shortName,
+    "stops": stops,
+  };
+}

src/shared/lib/src/data/stop.dart

@@ -1,16 +1,19 @@
-import "../utils.dart";
+import "utils.dart";
+import "route.dart";
+import "provider.dart";
 
 extension type StopID(String id) {
   StopID.fromJson(dynamic value) : id = value.toString();
 }
 
-class Stop {
+class Stop with Encodable {
   final StopID id;
   final String name;
   final String? description;
   final Coordinates coordinates;
-  final String provider;
+  final Provider provider;
   final Set<String> routes;
+  final Set<RouteID> routeIDs;
 
   Stop({
     required this.id,
@@ -18,32 +21,39 @@ class Stop {
     required this.description,
     required this.coordinates,
     required this.provider,
-  }) : routes = {};
+  }) : routes = {}, routeIDs = {};
 
   Stop.fromJson(Json json) :
     id = StopID(json["id"]),
     name = json["name"],
     description = json["description"],
     coordinates = (lat: json["latitude"], long: json["longitude"]),
-    provider = json["provider"],
-    routes = (json["routes"] as List).cast<String>().toSet();
+    provider = Provider.fromJson(json["provider"]),
+    routes = (json["routes"] as List).cast<String>().toSet(),
+    routeIDs = {
+      for (final routeID in (json["route_ids"] as List))
+        RouteID.fromJson(routeID),
+    };
 
   Stop.fromOcctJson(Json json) :
     id = StopID.fromJson(json["id"]),
     name = json["name"],
     description = null,
     coordinates = (lat: json["lat"], long: json["lng"]),
-    provider = "OCCT",
-    routes = <String>{};
+    provider = Provider.occt,
+    routes = <String>{},
+    routeIDs = <RouteID>{};
 
+  @override
   Map<String, dynamic> toJson() => {
     "id": id.id,
     "name": name,
     "description": description,
     "latitude": coordinates.lat,
     "longitude": coordinates.long,
-    "provider": provider,
+    "provider": provider.id,
     "routes": routes.toList(),
+    "route_ids": routeIDs.toList(),
   };
 
   String get summary {
@@ -57,4 +67,9 @@ class Stop {
     }
     return buffer.toString();
   }
+
+  void addRoute(RouteID id, String name) {
+    routeIDs.add(id);
+    routes.add(name);
+  }
 }

src/shared/lib/src/data/utils.dart

@@ -1,10 +1,18 @@
-/// A JSON object
+import "dart:math";
+
 typedef Json = Map<String, dynamic>;
-
+typedef CsvRow = List<String>;
 typedef FromJson<T> = T Function(Json);
-
 typedef Coordinates = ({double lat, double long});
 
+mixin Encodable {
+  Json toJson();
+}
+
+extension CoordinateUtils on Coordinates {
+  double distanceTo(Coordinates other) => sqrt(pow(lat - other.lat, 2) + pow(long - other.long, 2));
+}
+
 /// Utils on [Map].
 extension MapUtils<K, V> on Map<K, V> {
   /// Gets all the keys and values as 2-element records.
@@ -27,4 +35,16 @@ extension ListUtils<E> on List<E> {
       yield (i, this[i]);
     }
   }
+
+  E max(int Function(E) count) => reduce((a, b) {
+    final numA = count(a);
+    final numB = count(b);
+    return numA > numB ? a : b;
+  });
+
+  E min(int Function(E) count) => reduce((a, b) {
+    final numA = count(a);
+    final numB = count(b);
+    return numA < numB ? a : b;
+  });
 }

src/shared/lib/src/generator/generator.dart

@@ -0,0 +1,44 @@
+import "dart:convert";
+import "dart:io";
+
+import "package:shared/generator.dart";
+
+class Generator<T extends Encodable> extends Parser<T> {
+  final Parser<T> bc;
+  final Parser<T> occt;
+  final File outputFile;
+
+  Generator({
+    required this.bc,
+    required this.occt,
+    required this.outputFile,
+  });
+
+  @override
+  Future<List<T>> parse() async => [
+    ...await bc.parse(),
+    ...await occt.parse(),
+  ];
+
+  Future<void> generate() async {
+    final result = [
+      for (final data in await parse())
+        data.toJson(),
+    ];
+    const encoder = JsonEncoder.withIndent("  ");
+    final contents = encoder.convert(result);
+    await outputFile.writeAsString(contents);
+  }
+
+  static final stops = Generator(
+    bc: BcStopParser(),
+    occt: OcctStopParser(),
+    outputFile: File(serverDir / "GET_STOPS.json"),
+  );
+
+  static final routes = Generator(
+    bc: BcRoutesParser(),
+    occt: OcctRoutesParser(),
+    outputFile: File(serverDir / "GET_routes.json"),
+  );
+}

src/shared/lib/src/generator/routes_bc.dart

@@ -0,0 +1,46 @@
+import "dart:io";
+
+import "utils.dart";
+import "stops_bc.dart";
+
+typedef InOutTrips = (TripID, TripID);
+
+class BcRoutesParser extends Parser<Route> {
+  final routesFile = File(bcDataDir / "routes.txt");
+  final tripsFile = File(bcDataDir / "trips.txt");
+
+  final stopParser = BcStopParser();
+
+  Future<Map<RouteID, Route>> getRoutes() async => {
+    for (final csv in await readCsv(routesFile))
+      RouteID.fromBcCsv(csv): Route.fromBcCsv(csv),
+  };
+
+  Future<Map<RouteID, TripID>> getTripForRoutes(Map<TripID, List<StopID>> trips) async {
+    final tripsForRoutes = <RouteID, List<TripID>>{};
+    for (final row in await readCsv(tripsFile)) {
+      final routeID = RouteID(Provider.bc, row[0]);
+      final trip = TripID(row[2]);
+      // print(trip);
+      tripsForRoutes.addToList(routeID, trip);
+    }
+    return {
+      for (final (routeID, tripsForRoute) in tripsForRoutes.records)
+        routeID: tripsForRoute.max((trip) => trips[trip]!.length),
+    };
+  }
+
+  @override
+  Future<Iterable<Route>> parse() async {
+    final routes = await getRoutes();
+    final trips = await stopParser.getTrips();
+    final tripsForRoutes = await getTripForRoutes(trips);
+
+    for (final (routeID, route) in routes.records) {
+      final longestTrip = tripsForRoutes[routeID]!;
+      final stops = trips[longestTrip]!;
+      route.stops.addAll(stops);
+    }
+    return routes.values;
+  }
+}

src/shared/lib/src/generator/routes_occt.dart

@@ -0,0 +1,13 @@
+import "dart:io";
+
+import "utils.dart";
+
+class OcctRoutesParser extends Parser<Route> {
+  final routesFile = File(occtDataDir / "routes.json");
+
+  @override
+  Future<List<Route>> parse() async => [
+    for (final routeJson in await readJson(routesFile))
+      Route.fromOcctJson(routeJson),
+  ];
+}

src/shared/lib/src/generator/stops_bc.dart

@@ -2,7 +2,7 @@ import "dart:io";
 
 import "package:csv/csv.dart";
 
-import "../generator_utils.dart";
+import "utils.dart";
 
 class BcStopParser extends Parser<Stop> {
   static final tripsFile = File(bcDataDir / "stop_times.txt");
@@ -12,23 +12,23 @@ class BcStopParser extends Parser<Stop> {
 
   static final converter = CsvCodec(shouldParseNumbers: false).decoder;
 
-  Future<Map<TripID, Set<StopID>>> getTrips() async {
-    final result = <TripID, Set<StopID>>{};
+  Future<Map<TripID, List<StopID>>> getTrips() async {
+    final result = <TripID, List<StopID>>{};
     for (final row in await readCsv(tripsFile)) {
-      result.addToSet(TripID(row[0]), StopID(row[3]));
+      result.addToList(TripID(row[0]), StopID(row[3]));
     }
     return result;
   }
 
   Future<Map<TripID, RouteID>> getRoutes() async => {
     for (final row in await readCsv(routesFile))
-      TripID(row[2]): RouteID(row[0]),
+      TripID(row[2]): RouteID(Provider.bc, row[0]),
   };
 
   Future<Map<RouteID, String>> getRouteNames() async => {
     for (final row in await readCsv(routeNamesFile))
       if (row[2].isNotEmpty)
-        RouteID(row[0]): "${row[2]}) ${row[3]}",
+        RouteID(Provider.bc, row[0]): "${row[2]}) ${row[3]}",
   };
 
   Future<Map<StopID, Stop>> getStops() async {
@@ -44,7 +44,7 @@ class BcStopParser extends Parser<Stop> {
         name: name,
         description: description,
         coordinates: (lat: latitude, long: longitude),
-        provider: "BC Transit",
+        provider: Provider.bc,
       );
       result[stopID] = stop;
     }
@@ -53,7 +53,7 @@ class BcStopParser extends Parser<Stop> {
 
   void findRoutesForStops({
     required Iterable<Stop> stops,
-    required Map<TripID, Set<StopID>> trips,
+    required Map<TripID, List<StopID>> trips,
     required Map<TripID, RouteID> routes,
     required Map<RouteID, String> routeNames,
   }) {
@@ -63,7 +63,7 @@ class BcStopParser extends Parser<Stop> {
         final routeID = routes[tripID]!;
         final routeName = routeNames[routeID];
         if (routeName == null) continue;  // old route
-        stop.routes.add(routeName);
+        stop.addRoute(routeID, routeName);
       }
     }
   }

src/shared/lib/src/generator/stops_occt.dart

@@ -1,6 +1,6 @@
 import "dart:io";
 
-import "../generator_utils.dart";
+import "utils.dart";
 
 class OcctStopParser extends Parser<Stop> {
   /// Taken from: https://binghamtonupublic.etaspot.net/service.php?service=get_stops&token=TESTING
@@ -22,7 +22,7 @@ class OcctStopParser extends Parser<Stop> {
     final result = <StopID, List<RouteID>>{};
     for (final json in await readJson(stopsFile)) {
       final stopID = StopID.fromJson(json["id"]);
-      final routeID = RouteID.fromJson(json["rid"]);
+      final routeID = RouteID(Provider.occt, json["rid"]);
       result.addToList(stopID, routeID);
     }
     return result;
@@ -30,7 +30,7 @@ class OcctStopParser extends Parser<Stop> {
 
   Future<Map<RouteID, String>> getRouteNames() async => {
     for (final json in await readJson(routesFile))
-      RouteID.fromJson(json["id"]): json["name"],
+      RouteID(Provider.occt, json["id"]): json["name"],
   };
 
   @override
@@ -38,12 +38,12 @@ class OcctStopParser extends Parser<Stop> {
     final stops = await getStops();
     final routes = await getRoutes();
     final routeNames = await getRouteNames();
-    final routesToSkip = <RouteID>{RouteID("11")};  // no longer used
+    final routesToSkip = <RouteID>{RouteID(Provider.occt, "11")};
     for (final (stopID, stop) in stops.records) {
       for (final routeID in routes[stopID]!) {
         if (routesToSkip.contains(routeID)) continue;
         final routeName = routeNames[routeID]!;
-        stop.routes.add(routeName);
+        stop.addRoute(routeID, routeName);
       }
     }
     return stops.values;

src/shared/lib/src/generator/utils.dart

@@ -9,12 +9,6 @@ extension type TripID(String id) {
   TripID.fromJson(dynamic value) : id = value.toString();
 }
 
-extension type RouteID(String id) {
-  RouteID.fromJson(dynamic value) : id = value.toString();
-}
-
-typedef CsvRow = List<String>;
-
 extension DirectoryUtils on Directory {
   String operator /(String child) => "$path/$child";
 }

src/shared/lib/src/graph/state.dart

@@ -0,0 +1,73 @@
+import "package:a_star/a_star.dart";
+import "package:shared/data.dart";
+
+class StopState extends AStarState<StopState> {
+  static late final Map<RouteID, Route> routes;
+  static late final Map<StopID, Stop> stops;
+
+  static void init(Iterable<Route> allRoutes, Iterable<Stop> allStops) {
+    routes = {
+      for (final route in allRoutes)
+        route.id: route,
+    };
+    stops = {
+      for (final stop in allStops)
+        stop.id: stop,
+    };
+  }
+
+  final StopID stopID;
+  final StopID goalID;
+  final RouteID routeID;
+  StopState({
+    required this.stopID,
+    required this.goalID,
+    required this.routeID,
+    required super.depth,
+  });
+
+  @override
+  String hash() => "$stopID-$goalID-$routeID";
+
+  @override
+  bool isGoal() => stopID == goalID;
+
+  @override
+  double heuristic() {
+    final stop = stops[stopID]!;
+    final goal = stops[goalID]!;
+    return stop.coordinates.distanceTo(goal.coordinates);
+  }
+
+  @override
+  Iterable<StopState> expand() {
+    final route = routes[routeID]!;
+    final stop = stops[stopID]!;
+    final stopIndex = route.stops.indexOf(stopID);
+    final result = <StopState>[];
+
+    // 1): Go forward one stop on the same route
+    final nextIndex = stopIndex + 1;
+    if (nextIndex < route.stops.length) {
+      final nextStop = route.stops[nextIndex];
+      final state = StopState(stopID: nextStop, goalID: goalID, routeID: routeID, depth: depth + 1);
+      result.add(state);
+    }
+
+    // 2) Go back one stop on the same route
+    final prevIndex = stopIndex - 1;
+    if (prevIndex > 0) {
+      final prevStop = route.stops[prevIndex];
+      final state = StopState(stopID: prevStop, goalID: goalID, routeID: routeID, depth: depth + 1);
+      result.add(state);
+    }
+
+    // 3) Make any available transfers
+    for (final otherRoute in stop.routeIDs.difference({routeID})) {
+      final state = StopState(stopID: stopID, goalID: goalID, routeID: otherRoute, depth: depth + 1);
+      result.add(state);
+    }
+
+    return result;
+  }
+}

src/shared/lib/src/stops/generator.dart

@@ -1,28 +0,0 @@
-import "dart:convert";
-import "dart:io";
-
-import "../generator_utils.dart";
-
-import "bc.dart";
-import "occt.dart";
-
-class StopGenerator {
-  static final serverDir = Directory("../server");
-  static final outputFile = File(serverDir / "GET_STOPS.json");
-
-  final Parser<Stop> bc = BcStopParser();
-  final Parser<Stop> occt = OcctStopParser();
-
-  Future<void> generate() async {
-    final bcStops = await bc.parse();
-    final occtStops = await occt.parse();
-    final stops = [...bcStops, ...occtStops];
-    final result = [
-      for (final stop in stops)
-        stop.toJson(),
-    ];
-    const encoder = JsonEncoder.withIndent("  ");
-    final contents = encoder.convert(result);
-    await outputFile.writeAsString(contents);
-  }
-}

src/shared/pubspec.yaml

@@ -6,9 +6,14 @@ version: 1.0.0
 environment:
   sdk: ^3.7.0
 
+resolution: workspace
+
 # Add regular dependencies here.
 dependencies:
   csv: ^6.0.0
+  a_star: ^3.0.1
+  shelf: ^1.4.2
+  shelf_router: ^1.1.4
   # path: ^1.8.0
 
 dev_dependencies: