/**
 * CronScheduler
 * Schedules callbacks on a cron schedule using setTimeout.
 */
import type { CronInput, ScheduleController, ScheduleOptions } from './types';
/** CronScheduler schedules callbacks to run according to a cron expression. */
export declare class CronScheduler {
  private static readonly parser;
  private static readonly calculator;
  private static instance?;
  /** Get the CronScheduler instance. */
  static getInstance(): CronScheduler;
  private constructor();
  /**
   * Schedule a callback to run on the given cron schedule.
   *
   * @param expr - A standard 5-field cron string, parsed cron object or special alias.
   *   The special '@reboot' alias fires the callback immediately once.
   * @param callback - Function to invoke on each scheduled occurrence.
   * @param options - Optional ScheduleOptions with timezone.
   * @returns A ScheduleController with stop(), on(), and off() methods.
   *
   * @example
   * const job = scheduler.schedule( '0 * * * *', () => console.log( 'tick' ), { timezone: 'UTC' } );
   * job.on( 'tick', () => console.log( 'about to fire' ) );
   * job.stop();
   */
  schedule(expr: CronInput, callback: () => void, options?: ScheduleOptions): ScheduleController;
}