Add Stimulus capabilities controller

app/javascript/retrospring/controllers/capabilities_controller.ts

@@ -0,0 +1,21 @@
+import { Controller } from '@hotwired/stimulus';
+
+export default class extends Controller {
+  connect(): void {
+    const capabilities = [];
+
+    if ('share' in navigator) {
+      capabilities.push('cap-web-share');
+    }
+
+    if ('serviceWorker' in navigator) {
+      capabilities.push('cap-service-worker');
+    }
+
+    if ('Notification' in window) {
+      capabilities.push('cap-notification');
+    }
+
+    this.element.classList.add(...capabilities);
+  }
+}

app/javascript/retrospring/initializers/stimulus.ts

@@ -5,6 +5,7 @@ import CharacterCountController from "retrospring/controllers/character_count_co
 import CharacterCountWarningController from "retrospring/controllers/character_count_warning_controller";
 import FormatPopupController from "retrospring/controllers/format_popup_controller";
 import CollapseController from "retrospring/controllers/collapse_controller";
+import CapabilitiesController from "retrospring/controllers/capabilities_controller";
 
 /**
  * This module sets up Stimulus and our controllers
@@ -17,6 +18,7 @@ export default function (): void {
   window['Stimulus'] = Application.start();
   window['Stimulus'].register('announcement', AnnouncementController);
   window['Stimulus'].register('autofocus', AutofocusController);
+  window['Stimulus'].register('capabilities', CapabilitiesController);
   window['Stimulus'].register('character-count', CharacterCountController);
   window['Stimulus'].register('character-count-warning', CharacterCountWarningController);
   window['Stimulus'].register('collapse', CollapseController);

app/views/layouts/base.html.haml

@@ -23,7 +23,7 @@
     = csrf_meta_tags
     = yield(:og)
     = yield(:meta)
-  %body{ class: user_signed_in? ? '' : 'not-logged-in' }
+  %body{ class: user_signed_in? ? nil : 'not-logged-in', data: { controller: "capabilities" } }
     - if user_signed_in?
       = render 'navigation/main'
     - else