Support prioritized room list filters

This is to fix an issue where when using both the community filter panel and the search box it's an AND rather than further refining the results.

This makes the search box further refine the community filter panel results.

src/utils/arrays.ts

@@ -45,3 +45,63 @@ export function arrayDiff<T>(a: T[], b: T[]): { added: T[], removed: T[] } {
         removed: a.filter(i => !b.includes(i)),
     };
 }
+
+/**
+ * Helper functions to perform LINQ-like queries on arrays.
+ */
+export class ArrayUtil<T> {
+    /**
+     * Create a new array helper.
+     * @param a The array to help. Can be modified in-place.
+     */
+    constructor(private a: T[]) {
+    }
+
+    /**
+     * The value of this array, after all appropriate alterations.
+     */
+    public get value(): T[] {
+        return this.a;
+    }
+
+    /**
+     * Groups an array by keys.
+     * @param fn The key-finding function.
+     * @returns This.
+     */
+    public groupBy<K>(fn: (a: T) => K): GroupedArray<K, T> {
+        const obj = this.a.reduce((rv: Map<K, T[]>, val: T) => {
+            const k = fn(val);
+            if (!rv.has(k)) rv.set(k, []);
+            rv.get(k).push(val);
+            return rv;
+        }, new Map<K, T[]>());
+        return new GroupedArray(obj);
+    }
+}
+
+/**
+ * Helper functions to perform LINQ-like queries on groups (maps).
+ */
+export class GroupedArray<K, T> {
+    /**
+     * Creates a new group helper.
+     * @param val The group to help. Can be modified in-place.
+     */
+    constructor(private val: Map<K, T[]>) {
+    }
+
+    /**
+     * Orders the grouping into an array using the provided key order.
+     * @param keyOrder The key order.
+     * @returns An array helper of the result.
+     */
+    public orderBy(keyOrder: K[]): ArrayUtil<T> {
+        const a: T[] = [];
+        for (const k of keyOrder) {
+            if (!this.val.has(k)) continue;
+            a.push(...this.val.get(k));
+        }
+        return new ArrayUtil(a);
+    }
+}