Add customisation to make certain UI components invisible to students

Requires #6922

src/customisations/bayern/BayernComponentVisibilityCustomisations.ts

@@ -0,0 +1,58 @@
+/*
+Copyright 2021 New Vector Ltd
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Dev note: this customisation point is heavily inspired by UIFeature flags, though
+// with an intention of being used for more complex switching on whether or not a feature
+// should be shown.
+
+// Populate this class with the details of your customisations when copying it.
+
+import { UIComponent } from "../settings/UIFeature";
+import SdkConfig from "../../SdkConfig";
+import { MatrixClientPeg } from "../../MatrixClientPeg";
+
+/**
+ * Determines whether or not the active MatrixClient user should be able to use
+ * the given UI component. If shown, the user might still not be able to use the
+ * component depending on their contextual permissions. For example, invite options
+ * might be shown to the user but they won't have permission to invite users to
+ * the current room: the button will appear disabled.
+ * @param {UIComponent} component The component to check visibility for.
+ * @returns {boolean} True (default) if the user is able to see the component, false
+ * otherwise.
+ */
+function shouldShowComponent(component: UIComponent): boolean {
+    const studentInvisibleComponents = [
+        UIComponent.InviteUsers,
+        UIComponent.CreateRooms,
+    ];
+    if (!studentInvisibleComponents.includes(component)) return true;
+
+    const userPrefix = SdkConfig.get()['studentNamePrefix'];
+    const isStudent = userPrefix && MatrixClientPeg.get().getUserId().startsWith(userPrefix);
+    return !isStudent;
+}
+
+// This interface summarises all available customisation points and also marks
+// them all as optional. This allows customisers to only define and export the
+// customisations they need while still maintaining type safety.
+export interface IComponentVisibilityCustomisations {
+    shouldShowComponent?: typeof shouldShowComponent;
+}
+
+export const ComponentVisibilityCustomisations: IComponentVisibilityCustomisations = {
+    shouldShowComponent: shouldShowComponent,
+};