import Period = require('../unit/Period');
export interface Options {
    /**
     * Function that will be called once the countdown has reached zero.
     *
     * It is guaranteed to be called, even if the associated countdown has already reached zero when it begins.
     */
    finishedCallback?: () => any;
    /**
     * Function that will be called once the countdown has been constructed and started.
     *
     * There is no guarantee that this callback will fire before the finishedCallback.
     */
    loadedCallback?: () => any;
}
export interface Controller {
    /**
     * Returns a period that is always equal to the amount of time left until the countdown ends.
     */
    currentPeriod(): Period.Period;
    /**
     * Returns the last period for which the actual countdown has been updated.
     *
     * If the window is hidden or in a tab then this value might not reflect the actual progress of the countdown,
     * use {@see Controller#currentPeriod} if the returned value should always be up to date.
     */
    lastUpdate(): Period.Period;
    /**
     * Stop the countdown, once it has been stopped it will no longer fire the updater or update its internal period.
     *
     * If the countdown has already stopped this method will do nothing.
     */
    stop(): void;
    /**
     * Starts a previously stopped countdown, it will retain all the state from before it was stopped.
     *
     * If the countdown is already running, the only effect of this method will be a forced call to the updater.
     */
    start(): void;
}
export declare type Updater = (period: Period.Period) => any;
/**
 * Constructs a countdown loop that will call the provided updater function each time the countdown changes.
 *
 * When the endDate is reached the countdown will automatically stop itself,
 * it will always call the updater at least once.
 *
 * If milliseconds are required for the countdown then this should be done externally.
 * The reason milliseconds are not used is that they change too rapidly to actually be useful,
 * a similar effect to an actual millisecond countdown can be reached with visual tricks.
 *
 * @param {Date} endDate moment that we will be counting down to.
 * @param {Function} updater function which will be called each time a new period is available.
 * @param {object} opts callback options to track some of the progress of the countdown.
 * @throws If the provided endDate is not a valid date.
 */
export declare function create(endDate: Date, updater: Updater, opts: Options): Controller;