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