graycoreio/daffodil

import {
  pipe,
  timer,
  throwError,
} from 'rxjs';
import {
  retryWhen,
  mergeMap,
} from 'rxjs/operators';

/**
 * Retries failed Observables
 *
 * @param maxTries The maximum number of tries the observable will be tried
 * @param ms The initial amount of time
 */
export function backoff(maxTries: number, ms: number) {
  return pipe(
    retryWhen(attempt => attempt.pipe(
      mergeMap((shadowedAttempt: Error, i) => {
        if(i >= maxTries) {
          return throwError(shadowedAttempt);
        }
        return timer(ms*Math.pow(2,i));
      }),
    )),
  );
}