Push large tiles upwards back into the grid

src/array-utils.ts

@@ -0,0 +1,38 @@
+/*
+Copyright 2023 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.
+*/
+
+/**
+ * Gets the index of the last element in the array to satsify the given
+ * predicate.
+ */
+// TODO: remove this once TypeScript recognizes the existence of
+// Array.prototype.findLastIndex
+export function findLastIndex<T>(
+  array: T[],
+  predicate: (item: T) => boolean
+): number | null {
+  for (let i = array.length - 1; i >= 0; i--) {
+    if (predicate(array[i])) return i;
+  }
+
+  return null;
+}
+
+/**
+ * Counts the number of elements in an array that satsify the given predicate.
+ */
+export const count = <T>(array: T[], predicate: (item: T) => boolean): number =>
+  array.reduce((acc, item) => (predicate(item) ? acc + 1 : acc), 0);