Allow OS notifications

lib/services/permission_service.dart

@@ -0,0 +1,66 @@
+import 'package:permission_handler/permission_handler.dart';
+
+/// Information about a permission that the application cares about.
+///
+/// Add new entries to [appPermissions] when the app requires additional
+/// runtime permissions. The UI that drives the "permissions screen" reads this
+/// list and will automatically include new permissions without any further
+/// changes.
+class PermissionInfo {
+  const PermissionInfo({
+    required this.permission,
+    required this.label,
+    this.description,
+  });
+
+  final Permission permission;
+  final String label;
+  final String? description;
+}
+
+/// The set of permissions the app will check/request from the user.
+///
+/// Currently contains the permissions actually referenced in the codebase, but
+/// it should be expanded as new features are added.  Declaring a permission
+/// here ensures it appears on the permissions screen and is considered when
+/// performing bulk checks/requests.
+const List<PermissionInfo> appPermissions = [
+  PermissionInfo(
+    permission: Permission.notification,
+    label: 'Notifications',
+    description: 'Deliver alerts and sounds',
+  ),
+  PermissionInfo(
+    permission: Permission.location,
+    label: 'Location',
+    description: 'Access your location for geofencing',
+  ),
+  // add new permissions here as necessary
+];
+
+/// Returns the current status for every permission in [appPermissions].
+Future<Map<Permission, PermissionStatus>> getAllStatuses() async {
+  final map = <Permission, PermissionStatus>{};
+  for (final info in appPermissions) {
+    map[info.permission] = await info.permission.status;
+  }
+  return map;
+}
+
+/// Requests [permission] and returns the resulting status.
+Future<PermissionStatus> requestPermission(Permission permission) async {
+  return permission.request();
+}
+
+/// Convenience that requests every permission that is currently not granted.
+///
+/// Returns the full status map after requesting.
+Future<Map<Permission, PermissionStatus>> requestAllNeeded() async {
+  final statuses = await getAllStatuses();
+  for (final entry in statuses.entries) {
+    if (!entry.value.isGranted) {
+      statuses[entry.key] = await entry.key.request();
+    }
+  }
+  return statuses;
+}