Replace MSC3244 support with in-client room version checking (#9018)

* Replace MSC3244 support with in-client room version checking

* Fix irrelevant ternary

* It helps to use Jest correctly

src/utils/PreferredRoomVersions.ts

@@ -0,0 +1,55 @@
+/*
+Copyright 2022 The Matrix.org Foundation C.I.C.
+
+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.
+*/
+
+/**
+ * The preferred room versions for various features within the app. The
+ * room versions here are selected based on the client's support for the
+ * possible room versions in combination with server support in the
+ * ecosystem.
+ *
+ * Loosely follows https://spec.matrix.org/latest/rooms/#feature-matrix
+ */
+export class PreferredRoomVersions {
+    /**
+     * The room version to use when creating "restricted" rooms.
+     */
+    public static readonly RestrictedRooms = "9";
+
+    private constructor() {
+        // readonly, static, class
+    }
+}
+
+/**
+ * Determines if a room version supports the given feature using heuristics
+ * for how Matrix works.
+ * @param roomVer The room version to check support within.
+ * @param featureVer The room version of the feature. Should be from PreferredRoomVersions.
+ * @see PreferredRoomVersions
+ */
+export function doesRoomVersionSupport(roomVer: string, featureVer: string): boolean {
+    // Assumption: all unstable room versions don't support the feature. Calling code can check for unstable
+    // room versions explicitly if it wants to. The spec reserves [0-9] and `.` for its room versions.
+    if (!roomVer.match(/[\d.]+/)) {
+        return false;
+    }
+
+    // Dev note: While the spec says room versions are not linear, we can make reasonable assumptions
+    // until the room versions prove themselves to be non-linear in the spec. We should see this coming
+    // from a mile away and can course-correct this function if needed.
+    return Number(roomVer) >= Number(featureVer);
+}
+