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import { Observable } from '../Observable';
import { ReplaySubject } from '../ReplaySubject';
import { Subscription } from '../Subscription';
import { MonoTypeOperatorFunction, SchedulerLike } from '../types';
import { Subscriber } from '../Subscriber';
/**
* Share source and replay specified number of emissions on subscription.
*
* This operator is a specialization of `replay` that connects to a source observable
* and multicasts through a `ReplaySubject` constructed with the specified arguments.
* A successfully completed source will stay cached in the `shareReplayed observable` forever,
* but an errored source can be retried.
*
* ## Why use shareReplay?
* You generally want to use `shareReplay` when you have side-effects or taxing computations
* that you do not wish to be executed amongst multiple subscribers.
* It may also be valuable in situations where you know you will have late subscribers to
* a stream that need access to previously emitted values.
* This ability to replay values on subscription is what differentiates {@link share} and `shareReplay`.
*
* 
*
* ## Example
* ```javascript
* const obs$ = interval(1000);
* const subscription = obs$.pipe(
* take(4),
* shareReplay(3)
* );
* subscription.subscribe(x => console.log('source A: ', x));
* subscription.subscribe(y => console.log('source B: ', y));
*
* ```
*
* @see {@link publish}
* @see {@link share}
* @see {@link publishReplay}
*
* @param {Number} [bufferSize=Number.POSITIVE_INFINITY] Maximum element count of the replay buffer.
* @param {Number} [windowTime=Number.POSITIVE_INFINITY] Maximum time length of the replay buffer in milliseconds.
* @param {Scheduler} [scheduler] Scheduler where connected observers within the selector function
* will be invoked on.
* @return {Observable} An observable sequence that contains the elements of a sequence produced
* by multicasting the source sequence within a selector function.
* @method shareReplay
* @owner Observable
*/
export function shareReplay<T>(
bufferSize: number = Number.POSITIVE_INFINITY,
windowTime: number = Number.POSITIVE_INFINITY,
scheduler?: SchedulerLike
): MonoTypeOperatorFunction<T> {
return (source: Observable<T>) => source.lift(shareReplayOperator(bufferSize, windowTime, scheduler));
}
function shareReplayOperator<T>(bufferSize?: number, windowTime?: number, scheduler?: SchedulerLike) {
let subject: ReplaySubject<T>;
let refCount = 0;
let subscription: Subscription;
let hasError = false;
let isComplete = false;
return function shareReplayOperation(this: Subscriber<T>, source: Observable<T>) {
refCount++;
if (!subject || hasError) {
hasError = false;
subject = new ReplaySubject<T>(bufferSize, windowTime, scheduler);
subscription = source.subscribe({
next(value) { subject.next(value); },
error(err) {
hasError = true;
subject.error(err);
},
complete() {
isComplete = true;
subject.complete();
},
});
}
const innerSub = subject.subscribe(this);
return () => {
refCount--;
innerSub.unsubscribe();
if (subscription && refCount === 0 && isComplete) {
subscription.unsubscribe();
}
};
};
}
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