Refactor feature flag support.

lib/about_page.dart

@@ -165,6 +165,7 @@ class AboutPage extends ConsumerWidget {
                     'os': Platform.operatingSystem,
                     'os_version': Platform.operatingSystemVersion,
                   });
+                  data.insert(data.length - 1, ref.read(featureFlagProvider));
                   final text = const JsonEncoder.withIndent('  ').convert(data);
                   await ref.read(clipboardProvider).setText(text);
                   await ref.read(withContextProvider)(

lib/core/state.dart

@@ -53,17 +53,21 @@ abstract class ApplicationStateNotifier<T>
 }
 
 // Feature flags
-abstract class BaseFeature {
+sealed class BaseFeature {
   String get path;
+  String _subpath(String key);
 
   Feature feature(String key, {bool enabled = true}) =>
-      Feature(this, key, enabled: enabled);
+      Feature._(this, key, enabled: enabled);
 }
 
 class _RootFeature extends BaseFeature {
   _RootFeature._();
   @override
   String get path => '';
+
+  @override
+  String _subpath(String key) => key;
 }
 
 class Feature extends BaseFeature {
@@ -71,18 +75,41 @@ class Feature extends BaseFeature {
   final String key;
   final bool _defaultState;
 
-  Feature(this.parent, this.key, {bool enabled = true})
+  Feature._(this.parent, this.key, {bool enabled = true})
       : _defaultState = enabled;
 
   @override
-  String get path => '${parent.path}.$key';
+  String get path => parent._subpath(key);
+
+  @override
+  String _subpath(String key) => '$path.$key';
 }
 
 final BaseFeature root = _RootFeature._();
 
 typedef FeatureProvider = bool Function(Feature feature);
 
+final featureFlagProvider =
+    StateNotifierProvider<FeatureFlagsNotifier, Map<String, bool>>(
+        (_) => FeatureFlagsNotifier());
+
+class FeatureFlagsNotifier extends StateNotifier<Map<String, bool>> {
+  FeatureFlagsNotifier() : super({});
+
+  void loadConfig(Map<String, dynamic> config) {
+    const falsey = [0, false, null];
+    state = {for (final k in config.keys) k: !falsey.contains(config[k])};
+  }
+}
+
 final featureProvider = Provider<FeatureProvider>((ref) {
-  // TODO: Read file, check parents
-  return (feature) => feature._defaultState;
+  final featureMap = ref.watch(featureFlagProvider);
+
+  bool isEnabled(BaseFeature feature) => switch (feature) {
+        _RootFeature() => true,
+        Feature() => isEnabled(feature.parent) &&
+            (featureMap[feature.path] ?? feature._defaultState),
+      };
+
+  return isEnabled;
 });

lib/desktop/init.dart

@@ -157,6 +157,11 @@ Future<Widget> initialize(List<String> argv) async {
         .toFilePath();
   }
 
+  // Locate feature flags file
+  final featureFile = File(Uri.file(Platform.resolvedExecutable)
+      .resolve('features.json')
+      .toFilePath());
+
   final rpcFuture = _initHelper(exe!);
   _initLicenses();
 
@@ -218,15 +223,33 @@ Future<Widget> initialize(List<String> argv) async {
             ref.read(rpcProvider).valueOrNull?.setLogLevel(level);
           });
 
+          // Load feature flags, if they exist
+          featureFile.exists().then(
+            (exists) async {
+              if (exists) {
+                try {
+                  final featureConfig =
+                      jsonDecode(await featureFile.readAsString());
+                  ref
+                      .read(featureFlagProvider.notifier)
+                      .loadConfig(featureConfig);
+                } catch (error) {
+                  _log.error('Failed to parse feature flags', error);
+                }
+              }
+            },
+          );
+
           // Initialize systray
           ref.watch(systrayProvider);
 
           // Show a loading or error page while the Helper isn't ready
-          return ref.watch(rpcProvider).when(
+          return Consumer(
+              builder: (context, ref, child) => ref.watch(rpcProvider).when(
                     data: (data) => const MainPage(),
                     error: (error, stackTrace) => AppFailurePage(cause: error),
                     loading: () => _HelperWaiter(),
-              );
+                  ));
         }),
       ),
     ),

lib/piv/features.dart

@@ -20,12 +20,12 @@ final actions = piv.feature('actions');
 
 final actionsPin = actions.feature('pin');
 final actionsPuk = actions.feature('puk');
-final actionsManagementKey = actions.feature('managementKey', enabled: false);
-final actionsReset = actions.feature('reset', enabled: false);
+final actionsManagementKey = actions.feature('managementKey');
+final actionsReset = actions.feature('reset');
 
 final slots = piv.feature('slots');
 
-final slotsGenerate = slots.feature('generate', enabled: false);
-final slotsImport = slots.feature('import', enabled: false);
+final slotsGenerate = slots.feature('generate');
+final slotsImport = slots.feature('import');
 final slotsExport = slots.feature('export');
-final slotsDelete = slots.feature('delete', enabled: false);
+final slotsDelete = slots.feature('delete');