webvideo-transcript-summary-web-api/src/packages/event-emitter-to-readable-stream.ts

import { Readable as NodeReadable } from 'stream';

export interface Options<T extends NodeJS.EventEmitter> {
  dataEvent?: string;
  endEvent?: string;
  onBeforeEnd?: (emitter: T) => void;
}

export namespace Readable {
  export const fromEventEmitter = <T extends NodeJS.EventEmitter>(
    eventEmitter: T,
    options = {} as Options<T>,
  ) => {
    const stream = new NodeReadable({
      read() {
        // noop
      },
    });

    const dataEventHandler = (d: unknown) => {
      stream.emit('data', d);
    };

    const dataEvent = options?.dataEvent ?? 'data';
    eventEmitter.on(dataEvent, dataEventHandler);
    eventEmitter.on(options?.endEvent ?? 'end', () => {
      options?.onBeforeEnd?.(eventEmitter);
      stream.emit('end');
      eventEmitter.off(dataEvent, dataEventHandler);
    });

    return stream;
  };
}