Fixes to RegExpRunner usage in !search and !bansearch, validate that input regex is valid

backend/src/utils/async.ts

@@ -0,0 +1,54 @@
+import { Awaitable } from "knub/dist/utils";
+
+export async function asyncReduce<T, V>(
+  arr: T[],
+  callback: (accumulator: V, currentValue: T, index: number, array: T[]) => Awaitable<V>,
+  initialValue?: V,
+): Promise<V> {
+  let accumulator;
+  let arrayToIterate;
+  if (initialValue !== undefined) {
+    accumulator = initialValue;
+    arrayToIterate = arr;
+  } else {
+    accumulator = arr[0];
+    arrayToIterate = arr.slice(1);
+  }
+
+  for (const [i, currentValue] of arr.entries()) {
+    accumulator = await callback(accumulator, currentValue, i, arr);
+  }
+
+  return accumulator;
+}
+
+export function asyncFilter<T>(
+  arr: T[],
+  callback: (element: T, index: number, array: T[]) => Awaitable<boolean>,
+): Promise<T[]> {
+  return asyncReduce(
+    arr,
+    async (newArray, element, i, _arr) => {
+      if (await callback(element, i, _arr)) {
+        newArray.push(element);
+      }
+
+      return newArray;
+    },
+    [],
+  );
+}
+
+export function asyncMap<T, V>(
+  arr: T[],
+  callback: (currentValue: T, index: number, array: T[]) => Awaitable<V>,
+): Promise<V[]> {
+  return asyncReduce(
+    arr,
+    async (newArray, element, i, _arr) => {
+      newArray.push(await callback(element, i, _arr));
+      return newArray;
+    },
+    [],
+  );
+}