/**
 * @license
 * Copyright 2017 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/**
 * Fancy ID generator that creates 20-character string identifiers with the
 * following properties:
 *
 * 1. They're based on timestamp so that they sort *after* any existing ids.
 * 2. They contain 72-bits of random data after the timestamp so that IDs won't
 *    collide with other clients' IDs.
 * 3. They sort *lexicographically* (so the timestamp is converted to characters
 *    that will sort properly).
 * 4. They're monotonically increasing. Even if you generate more than one in
 *    the same timestamp, the latter ones will sort after the former ones. We do
 *    this by using the previous random bits but "incrementing" them by 1 (only
 *    in the case of a timestamp collision).
 */
export declare const nextPushId: (now: number) => string;
export declare const successor: (key: string) => string;
export declare const predecessor: (key: string) => string;