Separate business logic from UI widgets

Ensure that all business logic is performed in "pure" non-widget code. This improves code structure, testability etc.

The widget `RefreshTermsAndConditionsScreen` is entirely removed as refresh logic doesn't belong in the view layer.

All global (shared preferences) and network-specific (wallet-proxy) services are exposed as a "service repository" provided to the root of the widget tree along with separate watchable state components ("change notifiers") for selected network and T&C acceptance. The file state.dart is split into one file in `state/` for each of these state components.

The currently valid T&C version is fetched when initializing the "home" screen. The time-based logic of reloading this version is removed as it isn't clear how it actually should be implemented. It probably should be only when we're opening/waking up the app.

lib/main.dart

@@ -1,15 +1,30 @@
-import 'package:concordium_wallet/state.dart';
+import 'package:concordium_wallet/screens/routes.dart';
+import 'package:concordium_wallet/services/http.dart';
+import 'package:concordium_wallet/services/shared_preferences/service.dart';
+import 'package:concordium_wallet/services/wallet_proxy/service.dart';
+import 'package:concordium_wallet/state/config.dart';
+import 'package:concordium_wallet/state/network.dart';
+import 'package:concordium_wallet/state/services.dart';
+import 'package:concordium_wallet/state/terms_and_conditions.dart';
 import 'package:concordium_wallet/theme.dart';
 import 'package:flutter/material.dart';
-
-import 'package:concordium_wallet/screens/routes.dart';
 import 'package:provider/provider.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 
 void main() {
   runApp(const App());
 }
 
+final config = Config.ofNetworks([
+  const Network(
+    name: NetworkName.testnet,
+    walletProxyConfig: WalletProxyConfig(
+      baseUrl: 'https://wallet-proxy.testnet.concordium.com',
+    ),
+  ),
+]);
+const httpService = HttpService();
+
 class App extends StatelessWidget {
   const App({super.key});
 
@@ -21,13 +36,44 @@ class App extends StatelessWidget {
         final prefs = snapshot.data;
         if (prefs == null) {
           // Loading preferences.
-          return const CircularProgressIndicator();
+          return const Column(
+            mainAxisAlignment: MainAxisAlignment.center,
+            crossAxisAlignment: CrossAxisAlignment.center,
+            children: [
+              CircularProgressIndicator(),
+              SizedBox(height: 16),
+              // Setting text direction is required because we're outside 'MaterialApp' widget.
+              Text('Loading shared preferences...', textDirection: TextDirection.ltr),
+            ],
+          );
         }
-        return ChangeNotifierProvider(
-          create: (context) => AppState(AppSharedPreferences(prefs)),
-          child: MaterialApp(
-            routes: appRoutes,
-            theme: concordiumTheme(),
+        // Initialize services and provide them to the nested components
+        // (including the state components created in the child provider).
+        return Provider(
+          create: (context) {
+            final testnet = config.availableNetworks[NetworkName.testnet]!;
+            final prefsSvc = SharedPreferencesService(prefs);
+            return ServiceRepository(
+              networkServices: {testnet: NetworkServices.forNetwork(testnet, httpService: httpService)},
+              sharedPreferences: prefsSvc,
+            );
+          },
+          child: MultiProvider(
+            providers: [
+              ChangeNotifierProvider(
+                create: (context) => SelectedNetwork(config.availableNetworks[NetworkName.testnet]!),
+              ),
+              ChangeNotifierProvider(
+                create: (context) {
+                  final prefs = context.read<ServiceRepository>().sharedPreferences;
+                  return TermsAndConditionAcceptance(prefs);
+                },
+              ),
+            ],
+            child: MaterialApp(
+              routes: appRoutes,
+              theme: concordiumTheme(),
+            ),
           ),
         );
       },

lib/screens/home/screen.dart

@@ -1,54 +1,99 @@
-import 'package:concordium_wallet/screens/terms_and_conditions/refresh_screen.dart';
-import 'package:concordium_wallet/state.dart';
+import 'package:concordium_wallet/screens/terms_and_conditions/screen.dart';
+import 'package:concordium_wallet/services/wallet_proxy/service.dart';
+import 'package:concordium_wallet/state/network.dart';
+import 'package:concordium_wallet/state/services.dart';
+import 'package:concordium_wallet/state/terms_and_conditions.dart';
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
 
-class HomeScreen extends StatelessWidget {
+class HomeScreen extends StatefulWidget {
   const HomeScreen({super.key});
 
   @override
-  Widget build(BuildContext context) {
-    final tacLastCheckedAt = context.select((AppState state) => state.termsAndConditionsLastVerifiedAt);
-    //print('tacLastCheckedAt: $tacLastCheckedAt');
+  State<HomeScreen> createState() => _HomeScreenState();
+}
+
+class _HomeScreenState extends State<HomeScreen> {
+  @override
+  void initState() {
+    super.initState();
 
-    // Temporary...
-    final state = context.watch<AppState>();
-    var lastAcceptedVersion = state.sharedPreferences.termsAndConditionsAcceptedVersion;
-    // print('lastAcceptedVersion: $lastAcceptedVersion');
+    // Fetch currently valid T&C version unconditionally when initializing the widget.
+    final tacAcceptance = context.read<TermsAndConditionAcceptance>();
+    final network = context.read<SelectedNetwork>();
+    final services = context.read<ServiceRepository>().networkServices[network.selected]!;
+    _updateValidTac(services.walletProxy, tacAcceptance);
+  }
 
-    // Force recheck after 1 min.
-    // print('diff: ${DateTime.now().difference(tacLastCheckedAt).inMinutes}');
-    if (DateTime.now().difference(tacLastCheckedAt).inMinutes > 1) {
-      return const RefreshTermsAndConditionsScreen();
-    }
+  static Future<void> _updateValidTac(WalletProxyService walletProxy, TermsAndConditionAcceptance tacAcceptance) async {
+    final tac = await walletProxy.getTermsAndConditions();
+    tacAcceptance.validVersionUpdated(ValidTermsAndConditions.refreshedNow(termsAndConditions: tac));
+  }
 
+  @override
+  Widget build(BuildContext context) {
     return Scaffold(
       body: Container(
         padding: const EdgeInsets.fromLTRB(16, 64, 16, 16),
-        child: Column(
-          children: [
-            Expanded(
-              child: Column(
+        child: Builder(
+          builder: (context) {
+            final tacState = context.watch<TermsAndConditionAcceptance>();
+            final validTac = tacState.valid;
+            if (validTac == null) {
+              // Show spinner if no valid T&C have been resolved yet (not as a result of actually ongoing fetch).
+              // Should store the future from '_updateValidTac' and use that in a wrapping 'FutureBuilder'..?
+              return const Column(
+                mainAxisAlignment: MainAxisAlignment.center,
                 children: [
-                  Text('T&C last checked at $tacLastCheckedAt.'),
-                  Text('Last T&C version accepted: $lastAcceptedVersion'),
+                  CircularProgressIndicator(),
+                  SizedBox(height: 16),
+                  Center(child: Text('Waiting for enforced Terms & Conditions...')),
                 ],
-              ),
-            ),
-            ElevatedButton(
-              onPressed: () {
-                state.setTermsAndConditionsLastVerifiedAt(DateTime.fromMillisecondsSinceEpoch(0));
-              },
-              child: const Text('Reset check time'),
-            ),
-            const SizedBox(height: 8),
-            ElevatedButton(
-              onPressed: () {
-                state.sharedPreferences.setTermsAndConditionsAcceptedVersion('0');
-              },
-              child: const Text('Reset accepted version'),
-            ),
-          ],
+              );
+            }
+            final acceptedTac = tacState.accepted;
+            if (acceptedTac == null || !acceptedTac.isValid(validTac.termsAndConditions)) {
+              return TermsAndConditionsScreen(
+                validTermsAndConditions: validTac.termsAndConditions,
+                acceptedTermsAndConditionsVersion: acceptedTac?.version,
+              );
+            }
+            return Column(
+              children: [
+                Expanded(
+                  child: Column(
+                    children: [
+                      Text('Accepted T&C version: ${tacState.accepted?.version}'),
+                      Text('Valid T&C last refreshed at ${tacState.valid?.refreshedAt}.'),
+                    ],
+                  ),
+                ),
+                ElevatedButton(
+                  onPressed: () => context.read<TermsAndConditionAcceptance>().testResetValidTime(),
+                  child: const Text('Reset update time of valid T&C'),
+                ),
+                const SizedBox(height: 8),
+                ElevatedButton(
+                  onPressed: () => context.read<TermsAndConditionAcceptance>().resetValid(),
+                  // NOTE: This breaks the app because no re-fetch is triggered - hot restart is necessary to recover.
+                  child: const Text('Reset valid T&C (and break the app)'),
+                ),
+                const SizedBox(height: 8),
+                ElevatedButton(
+                  onPressed: () {
+                    const tac = AcceptedTermsAndConditions(version: '1.2.3');
+                    context.read<TermsAndConditionAcceptance>().userAccepted(tac);
+                  },
+                  child: const Text('Set accepted T&C version to 1.2.3'),
+                ),
+                const SizedBox(height: 8),
+                ElevatedButton(
+                  onPressed: () => context.read<TermsAndConditionAcceptance>().resetAccepted(),
+                  child: const Text('Reset accepted T&C'),
+                ),
+              ],
+            );
+          },
         ),
       ),
     );

lib/screens/terms_and_conditions/screen.dart

@@ -1,29 +1,16 @@
 import 'package:concordium_wallet/screens/terms_and_conditions/widget.dart';
 import 'package:concordium_wallet/services/wallet_proxy/model.dart';
-import 'package:concordium_wallet/state.dart';
+import 'package:concordium_wallet/state/terms_and_conditions.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_svg/flutter_svg.dart';
 import 'package:provider/provider.dart';
 import 'package:url_launcher/url_launcher.dart';
 
-class TermsAndConditionsViewModel {
-  final TermsAndConditions currentTac;
-  final String? acceptedTacVersion;
-  final void Function(BuildContext context) onAccept;
-
-  const TermsAndConditionsViewModel(this.currentTac, this.acceptedTacVersion, this.onAccept);
-
-  void userAccepted(BuildContext context) {
-    final state = context.read<AppState>();
-    state.sharedPreferences.setTermsAndConditionsAcceptedVersion(currentTac.version);
-    onAccept(context);
-  }
-}
-
 class TermsAndConditionsScreen extends StatefulWidget {
-  final TermsAndConditionsViewModel viewModel;
+  final TermsAndConditions validTermsAndConditions;
+  final String? acceptedTermsAndConditionsVersion;
 
-  const TermsAndConditionsScreen(this.viewModel, {super.key});
+  const TermsAndConditionsScreen({super.key, required this.validTermsAndConditions, this.acceptedTermsAndConditionsVersion});
 
   @override
   State<TermsAndConditionsScreen> createState() => _TermsAndConditionsScreenState();
@@ -89,24 +76,24 @@ class _TermsAndConditionsScreenState extends State<TermsAndConditionsScreen> {
                 Flexible(
                   child: GestureDetector(
                     onTap: () {
-                      _launchUrl(widget.viewModel.currentTac.url);
+                      _launchUrl(widget.validTermsAndConditions.url);
                     },
                     child: RichText(
                       text: TextSpan(
                         style: Theme.of(context).textTheme.bodySmall,
                         children: [
                           const TextSpan(text: 'I have read and agree to the '),
                           TextSpan(
-                            text: 'Terms and Conditions v${widget.viewModel.currentTac.version}',
+                            text: 'Terms and Conditions v${widget.validTermsAndConditions.version}',
                             style: const TextStyle(
                               color: Colors.indigo,
                               fontWeight: FontWeight.bold,
                             ),
                           ),
-                          switch (widget.viewModel.acceptedTacVersion) {
+                          switch (widget.acceptedTermsAndConditionsVersion) {
                             null => const TextSpan(text: '.'),
                             String v => TextSpan(
-                                text: ' (you previously accepted version $v).',
+                                text: ' (you previously accepted v$v).',
                                 style: Theme.of(context).textTheme.bodySmall,
                               ),
                           },
@@ -134,7 +121,12 @@ class _TermsAndConditionsScreenState extends State<TermsAndConditionsScreen> {
 
   Function()? _onAcceptButtonPressed(BuildContext context) {
     if (isAccepted) {
-      return () => widget.viewModel.userAccepted(context);
+      return () {
+        final tac = AcceptedTermsAndConditions(
+          version: widget.validTermsAndConditions.version,
+        );
+        context.read<TermsAndConditionAcceptance>().userAccepted(tac);
+      };
     }
     return null;
   }

lib/screens/terms_and_conditions/widget.dart

@@ -6,7 +6,9 @@ class ToggleAcceptedWidget extends StatelessWidget {
 
   ToggleAcceptedWidget({super.key, required this.isAccepted, required this.setAccepted});
 
-  final MaterialStateProperty<Icon?> icon = MaterialStateProperty.resolveWith<Icon?>((states) => Icon(_iconData(states)));
+  final MaterialStateProperty<Icon?> icon = MaterialStateProperty.resolveWith<Icon?>(
+    (states) => Icon(_iconData(states)),
+  );
 
   static IconData _iconData(Set<MaterialState> states) {
     if (states.contains(MaterialState.selected)) {

lib/services/http.dart

@@ -1,9 +1,10 @@
 import 'package:http/http.dart' as http;
 
 class HttpService {
-  HttpService();
+  const HttpService();
 
   Future<http.Response> get(Uri url) async {
+    // TODO: Implement retry logic.
     return http.get(url);
   }
 }