Use an algorithmic comparator for room list ops

Not all algorithms are timestamp based.

Author: turt2live

src/stores/RoomListStore.js

@@ -372,6 +372,14 @@ class RoomListStore extends Store {
     _slotRoomIntoList(room, category, tag, existingEntries, newList, lastTimestampFn) {
         const targetCategoryIndex = CATEGORY_ORDER.indexOf(category);
 
+        let categoryComparator = (a, b) => lastTimestampFn(a.room) >= lastTimestampFn(b.room);
+        const sortAlgorithm = getListAlgorithm(tag, this._state.algorithm);
+        if (sortAlgorithm === ALGO_RECENT) {
+            categoryComparator = (a, b) => this._recentsComparator(a, b, lastTimestampFn);
+        } else if (sortAlgorithm === ALGO_ALPHABETIC) {
+            categoryComparator = (a, b) => this._lexicographicalComparator(a, b);
+        }
+
         // The slotting algorithm works by trying to position the room in the most relevant
         // category of the list (red > grey > etc). To accomplish this, we need to consider
         // a couple cases: the category existing in the list but having other rooms in it and
@@ -449,7 +457,7 @@ class RoomListStore extends Store {
                 // based on most recent timestamp.
                 const changedBoundary = entryCategoryIndex > targetCategoryIndex;
                 const currentCategory = entryCategoryIndex === targetCategoryIndex;
-                if (changedBoundary || (currentCategory && lastTimestampFn(room) >= lastTimestampFn(entry.room))) {
+                if (changedBoundary || (currentCategory && categoryComparator({room}, entry) <= 0)) {
                     if (changedBoundary) {
                         // If we changed a boundary, then we've gone too far - go to the top of the last
                         // section instead.