Update types for Queue

backend/src/Queue.ts

@@ -1,23 +1,24 @@
 import { SECONDS } from "./utils";
 
-type QueueFn = (...args: any[]) => Promise<any>;
+type InternalQueueFn = () => Promise<void>;
+type AnyFn = (...args: any[]) => any;
 
 const DEFAULT_TIMEOUT = 10 * SECONDS;
 
-export class Queue {
-  protected running: boolean = false;
-  protected queue: QueueFn[] = [];
+export class Queue<TQueueFunction extends AnyFn = AnyFn> {
+  protected running = false;
+  protected queue: InternalQueueFn[] = [];
   protected timeout: number;
 
   constructor(timeout = DEFAULT_TIMEOUT) {
     this.timeout = timeout;
   }
 
-  public add(fn) {
-    const promise = new Promise(resolve => {
+  public add(fn: TQueueFunction): Promise<void> {
+    const promise = new Promise<void>(resolve => {
       this.queue.push(async () => {
         await fn();
-        resolve(undefined);
+        resolve();
       });
 
       if (!this.running) this.next();
@@ -26,7 +27,7 @@ export class Queue {
     return promise;
   }
 
-  public next() {
+  public next(): void {
     this.running = true;
 
     if (this.queue.length === 0) {
@@ -37,7 +38,7 @@ export class Queue {
     const fn = this.queue.shift()!;
     new Promise(resolve => {
       // Either fn() completes or the timeout is reached
-      fn().then(resolve);
+      void fn().then(resolve);
       setTimeout(resolve, this.timeout);
     }).then(() => this.next());
   }