@evolu/web/src/WebWorker.ts

Evolu for web

/**
 * Typed wrapper for Web Worker
 *
 * While Comlink DX is nice, there are still memory leaks and unresolved bugs.
 * Use plain Web Worker with a typed wrapper if maximum performance and
 * reliability are required.
 *
 * @module
 */

import { constVoid, Worker } from "@evolu/common";

/**
 * Wraps a Web Worker to provide a typed interface for sending and receiving
 * messages.
 */
export const wrapWebWorker = <Input, Output>(
  createWebWorker: () => globalThis.Worker,
): Worker<Input, Output> => {
  // Server.
  if (typeof document === "undefined")
    return {
      postMessage: constVoid,
      onMessage: constVoid,
    };

  const webWorker = createWebWorker();

  const worker: Worker<Input, Output> = {
    postMessage: (message) => {
      webWorker.postMessage(message);
    },

    onMessage: (callback) => {
      webWorker.onmessage = (event: MessageEvent<Output>) => {
        callback(event.data);
      };
    },
  };

  return worker;
};

export const wrapWebWorkerSelf = <Input, Output>(
  worker: Worker<Input, Output>,
): void => {
  worker.onMessage((message) => {
    postMessage(message);
  });

  self.onmessage = (event: MessageEvent<Input>) => {
    worker.postMessage(event.data);
  };
};