/**
 * Copyright (c) Facebook, Inc. And its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

import type { FacetFilters } from 'algoliasearch/lite';

export function mergeFacetFilters(f1: FacetFilters, f2: FacetFilters): FacetFilters;

export function mergeFacetFilters(f1: FacetFilters | undefined, f2: FacetFilters | undefined): FacetFilters | undefined;

export function mergeFacetFilters(
  f1: FacetFilters | undefined,
  f2: FacetFilters | undefined,
): FacetFilters | undefined {
  if (f1 === undefined) {
    return f2;
  }
  if (f2 === undefined) {
    return f1;
  }

  const normalize = (f: FacetFilters): FacetFilters => (typeof f === 'string' ? [f] : f);
  return [...normalize(f1), ...normalize(f2)];
}