import { Observable } from '../Observable';
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import { MonoTypeOperatorFunction, ObservableInput } from '../types';
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import { concat } from '../observable/concat';
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import { take } from './take';
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import { ignoreElements } from './ignoreElements';
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import { mapTo } from './mapTo';
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import { mergeMap } from './mergeMap';
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import { innerFrom } from '../observable/innerFrom';
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/** @deprecated The `subscriptionDelay` parameter will be removed in v8. */
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export function delayWhen<T>(
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delayDurationSelector: (value: T, index: number) => ObservableInput<any>,
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subscriptionDelay: Observable<any>
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): MonoTypeOperatorFunction<T>;
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export function delayWhen<T>(delayDurationSelector: (value: T, index: number) => ObservableInput<any>): MonoTypeOperatorFunction<T>;
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/**
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* Delays the emission of items from the source Observable by a given time span
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* determined by the emissions of another Observable.
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*
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* <span class="informal">It's like {@link delay}, but the time span of the
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* delay duration is determined by a second Observable.</span>
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*
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* 
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*
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* `delayWhen` operator shifts each emitted value from the source Observable by
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* a time span determined by another Observable. When the source emits a value,
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* the `delayDurationSelector` function is called with the value emitted from
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* the source Observable as the first argument to the `delayDurationSelector`.
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* The `delayDurationSelector` function should return an {@link ObservableInput},
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* that is internally converted to an Observable that is called the "duration"
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* Observable.
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*
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* The source value is emitted on the output Observable only when the "duration"
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* Observable emits ({@link guide/glossary-and-semantics#next next}s) any value.
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* Upon that, the "duration" Observable gets unsubscribed.
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*
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* Before RxJS V7, the {@link guide/glossary-and-semantics#complete completion}
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* of the "duration" Observable would have been triggering the emission of the
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* source value to the output Observable, but with RxJS V7, this is not the case
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* anymore.
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*
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* Only next notifications (from the "duration" Observable) trigger values from
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* the source Observable to be passed to the output Observable. If the "duration"
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* Observable only emits the complete notification (without next), the value
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* emitted by the source Observable will never get to the output Observable - it
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* will be swallowed. If the "duration" Observable errors, the error will be
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* propagated to the output Observable.
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*
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* Optionally, `delayWhen` takes a second argument, `subscriptionDelay`, which
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* is an Observable. When `subscriptionDelay` emits its first value or
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* completes, the source Observable is subscribed to and starts behaving like
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* described in the previous paragraph. If `subscriptionDelay` is not provided,
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* `delayWhen` will subscribe to the source Observable as soon as the output
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* Observable is subscribed.
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*
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* ## Example
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*
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* Delay each click by a random amount of time, between 0 and 5 seconds
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*
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* ```ts
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* import { fromEvent, delayWhen, interval } from 'rxjs';
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*
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* const clicks = fromEvent(document, 'click');
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* const delayedClicks = clicks.pipe(
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* delayWhen(() => interval(Math.random() * 5000))
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* );
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* delayedClicks.subscribe(x => console.log(x));
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* ```
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*
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* @see {@link delay}
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* @see {@link throttle}
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* @see {@link throttleTime}
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* @see {@link debounce}
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* @see {@link debounceTime}
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* @see {@link sample}
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* @see {@link sampleTime}
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* @see {@link audit}
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* @see {@link auditTime}
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*
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* @param delayDurationSelector A function that returns an `ObservableInput` for
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* each `value` emitted by the source Observable, which is then used to delay the
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* emission of that `value` on the output Observable until the `ObservableInput`
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* returned from this function emits a next value. When called, beside `value`,
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* this function receives a zero-based `index` of the emission order.
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* @param subscriptionDelay An Observable that triggers the subscription to the
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* source Observable once it emits any value.
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* @return A function that returns an Observable that delays the emissions of
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* the source Observable by an amount of time specified by the Observable
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* returned by `delayDurationSelector`.
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*/
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export function delayWhen<T>(
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delayDurationSelector: (value: T, index: number) => ObservableInput<any>,
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subscriptionDelay?: Observable<any>
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): MonoTypeOperatorFunction<T> {
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if (subscriptionDelay) {
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// DEPRECATED PATH
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return (source: Observable<T>) =>
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concat(subscriptionDelay.pipe(take(1), ignoreElements()), source.pipe(delayWhen(delayDurationSelector)));
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}
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return mergeMap((value, index) => innerFrom(delayDurationSelector(value, index)).pipe(take(1), mapTo(value)));
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}
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