/**
 * Executes an `async` resolver function, providing the `Promise`-to-be-returned as the
 * first argument to the resolver so that the resolver can refer to the `Promise` that
 * external callers will see.
 *
 * ```ts
 * const outer = selfAwareAsync(async inner => {
 *  console.log(outer === inner); // true
 * });
 * ```
 *
 * This utility exists to reduce boilerplate in cases where promise resolving code needs
 * to track or register its "own" `Promise` *as seen by the caller* in some way. E.g.,
 * when mapping `Promise` chains for `client.cancel()`.
 *
 * @param resolver
 * @returns
 */
export function selfAwareAsync<T>(
  resolver: (promise: Promise<T>) => Promise<T>,
): Promise<T> {
  let resolve: (value: T) => void;
  let reject: (reason?: any) => void;

  const resultPromise = new Promise<T>((res, rej) => {
    resolve = res;
    reject = rej;
  });

  resolver(resultPromise)
    .then((result) => {
      resolve(result);
    })
    .catch((error) => {
      reject(error);
    });

  return resultPromise;
}