createExternalExecController

createExternalExecController.ts

import {
  filter,
  firstValueFrom,
  fromEvent,
  map,
  merge,
  share,
  tap,
  timer,
} from 'rxjs';

/**
 * Creates an external execution controller.
 *
 * @example
 * ```tsx
 * const execController = createExternalExecController("my-channel", (value) => {
 *   console.log(value);
 * });
 *
 * execController.isExist().then((isExist) => {
 *   if (!isExist) {
 *     execController.exec("Hello, world!"); // will exec in external window that receive the message
 *   }
 * });
 * ```
 *
 * @param channelName - The name of the broadcast channel.
 * @param exec - A function that handles the execution of a value.
 * @returns An object with methods and properties related to the external execution controller.
 */
export function createExternalExecController(
  channelName: string,
  exec: (value: string | object) => void,
) {
  const channel = new BroadcastChannel(channelName);
  const events = {
    exec: 'exec',
    isExist: 'isExist',
    isExistResponse: 'isExistResponse',
  };

  const obs = fromEvent<
    MessageEvent<{ type: keyof typeof events; value: string | object }>
  >(channel, 'message').pipe(
    map((event) => event.data),
    tap(({ type, value }) => {
      switch (type) {
        case 'isExist':
          channel.postMessage({ type: events.isExistResponse });
          break;
        case 'exec':
          exec(value);
          break;

        default:
          break;
      }
    }),
    share(),
  );

  obs.subscribe();

  return {
    channel,
    events,
    exec: (value?: string | object) => {
      channel.postMessage({ type: events.exec, value });
    },
    isExist: async () => {
      channel.postMessage({ type: events.isExist });

      const result = await firstValueFrom(
        merge(
          timer(1000).pipe(map(() => false)),
          obs.pipe(
            filter((x) => x.type === events.isExistResponse),
            map(() => true),
          ),
        ),
      );

      return result;
    },
  };
}