import { async } from '../scheduler/async';
import { isDate } from '../util/isDate';
import { Subscriber } from '../Subscriber';
import { Notification } from '../Notification';
/**
 * Delays the emission of items from the source Observable by a given timeout or
 * until a given Date.
 *
 * <span class="informal">Time shifts each item by some specified amount of
 * milliseconds.</span>
 *
 * <img src="./img/delay.png" width="100%">
 *
 * If the delay argument is a Number, this operator time shifts the source
 * Observable by that amount of time expressed in milliseconds. The relative
 * time intervals between the values are preserved.
 *
 * If the delay argument is a Date, this operator time shifts the start of the
 * Observable execution until the given date occurs.
 *
 * @example <caption>Delay each click by one second</caption>
 * var clicks = Rx.Observable.fromEvent(document, 'click');
 * var delayedClicks = clicks.delay(1000); // each click emitted after 1 second
 * delayedClicks.subscribe(x => console.log(x));
 *
 * @example <caption>Delay all clicks until a future date happens</caption>
 * var clicks = Rx.Observable.fromEvent(document, 'click');
 * var date = new Date('March 15, 2050 12:00:00'); // in the future
 * var delayedClicks = clicks.delay(date); // click emitted only after that date
 * delayedClicks.subscribe(x => console.log(x));
 *
 * @see {@link debounceTime}
 * @see {@link delayWhen}
 *
 * @param {number|Date} delay The delay duration in milliseconds (a `number`) or
 * a `Date` until which the emission of the source items is delayed.
 * @param {Scheduler} [scheduler=async] The IScheduler to use for
 * managing the timers that handle the time-shift for each item.
 * @return {Observable} An Observable that delays the emissions of the source
 * Observable by the specified timeout or Date.
 * @method delay
 * @owner Observable
 */
export function delay(delay, scheduler = async) {
    const absoluteDelay = isDate(delay);
    const delayFor = absoluteDelay ? (+delay - scheduler.now()) : Math.abs(delay);
    return (source) => source.lift(new DelayOperator(delayFor, scheduler));
}
class DelayOperator {
    constructor(delay, scheduler) {
        this.delay = delay;
        this.scheduler = scheduler;
    }
    call(subscriber, source) {
        return source.subscribe(new DelaySubscriber(subscriber, this.delay, this.scheduler));
    }
}
/**
 * We need this JSDoc comment for affecting ESDoc.
 * @ignore
 * @extends {Ignored}
 */
class DelaySubscriber extends Subscriber {
    constructor(destination, delay, scheduler) {
        super(destination);
        this.delay = delay;
        this.scheduler = scheduler;
        this.queue = [];
        this.active = false;
        this.errored = false;
    }
    static dispatch(state) {
        const source = state.source;
        const queue = source.queue;
        const scheduler = state.scheduler;
        const destination = state.destination;
        while (queue.length > 0 && (queue[0].time - scheduler.now()) <= 0) {
            queue.shift().notification.observe(destination);
        }
        if (queue.length > 0) {
            const delay = Math.max(0, queue[0].time - scheduler.now());
            this.schedule(state, delay);
        }
        else {
            this.unsubscribe();
            source.active = false;
        }
    }
    _schedule(scheduler) {
        this.active = true;
        this.add(scheduler.schedule(DelaySubscriber.dispatch, this.delay, {
            source: this, destination: this.destination, scheduler: scheduler
        }));
    }
    scheduleNotification(notification) {
        if (this.errored === true) {
            return;
        }
        const scheduler = this.scheduler;
        const message = new DelayMessage(scheduler.now() + this.delay, notification);
        this.queue.push(message);
        if (this.active === false) {
            this._schedule(scheduler);
        }
    }
    _next(value) {
        this.scheduleNotification(Notification.createNext(value));
    }
    _error(err) {
        this.errored = true;
        this.queue = [];
        this.destination.error(err);
    }
    _complete() {
        this.scheduleNotification(Notification.createComplete());
    }
}
class DelayMessage {
    constructor(time, notification) {
        this.time = time;
        this.notification = notification;
    }
}
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