reconnectWebsockets.ts

type EventTargetWithAddListener = EventTarget & {
  listeners: Map<string, any>;
  addEventListener(
    type: string,
    listeners: Map<string, (event: Event) => any>,
    options?: boolean | AddEventListenerOptions
  ): void;
};

export const handleEventEmitter = (
  target: EventTarget,
  previous?: EventTargetWithAddListener
): EventTargetWithAddListener => {
  const proxy = (fn, originalMethod) =>
    function (...args: any[]) {
      return fn(...args), originalMethod.apply(this, args);
    };
  const listeners = new Map();
  const handler = {
    get: (obj: any, prop: string, value: any) =>
      prop === "listeners"
        ? listeners
        : prop === "addEventListener"
        ? proxy((...a) => listeners.set(a, a), obj[prop])
        : prop === "removeEventListener"
        ? proxy((...a) => listeners.delete(a), obj[prop])
        : Reflect.get(obj, prop, value),
  };
  const newTarget = new Proxy(target, handler);
  for (const [_, [key, value]] of previous?.listeners ?? [])
    newTarget.addEventListener(key, value);
  return newTarget;
};

export default (
  wss: Record<string, WebSocket>,
  timeout = 5000,
  reapplyEvents = true
) => {
  Object.keys(wss).forEach((key) => {
    wss[key] = reapplyEvents ? handleEventEmitter(wss[key]) : wss[key];
    wss[key].binaryType = "arraybuffer";
    wss[key].addEventListener("open", () => console.log(`${key} is opened`));
    wss[key].addEventListener("close", () => {
      console.warn(`${key} has closed, reopening in ${timeout}ms`);
      setTimeout(() => {
        wss[key] = reapplyEvents
          ? handleEventEmitter(new WebSocket(wss[key].url), wss[key])
          : new WebSocket(wss[key].url);
        wss[key].binaryType = "arraybuffer";
      }, timeout);
    });
  });
  return wss;
};