import { ConnectableObservable } from '../observable/ConnectableObservable';
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import { Subscription } from '../Subscription';
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import { MonoTypeOperatorFunction } from '../types';
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import { operate } from '../util/lift';
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import { createOperatorSubscriber } from './OperatorSubscriber';
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/**
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* Make a {@link ConnectableObservable} behave like a ordinary observable and automates the way
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* you can connect to it.
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*
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* Internally it counts the subscriptions to the observable and subscribes (only once) to the source if
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* the number of subscriptions is larger than 0. If the number of subscriptions is smaller than 1, it
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* unsubscribes from the source. This way you can make sure that everything before the *published*
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* refCount has only a single subscription independently of the number of subscribers to the target
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* observable.
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*
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* Note that using the {@link share} operator is exactly the same as using the `multicast(() => new Subject())` operator
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* (making the observable hot) and the *refCount* operator in a sequence.
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*
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* 
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*
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* ## Example
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*
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* In the following example there are two intervals turned into connectable observables
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* by using the *publish* operator. The first one uses the *refCount* operator, the
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* second one does not use it. You will notice that a connectable observable does nothing
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* until you call its connect function.
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*
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* ```ts
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* import { interval, tap, publish, refCount } from 'rxjs';
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*
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* // Turn the interval observable into a ConnectableObservable (hot)
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* const refCountInterval = interval(400).pipe(
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* tap(num => console.log(`refCount ${ num }`)),
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* publish(),
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* refCount()
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* );
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*
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* const publishedInterval = interval(400).pipe(
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* tap(num => console.log(`publish ${ num }`)),
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* publish()
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* );
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*
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* refCountInterval.subscribe();
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* refCountInterval.subscribe();
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* // 'refCount 0' -----> 'refCount 1' -----> etc
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* // All subscriptions will receive the same value and the tap (and
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* // every other operator) before the `publish` operator will be executed
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* // only once per event independently of the number of subscriptions.
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*
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* publishedInterval.subscribe();
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* // Nothing happens until you call .connect() on the observable.
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* ```
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*
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* @return A function that returns an Observable that automates the connection
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* to ConnectableObservable.
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* @see {@link ConnectableObservable}
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* @see {@link share}
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* @see {@link publish}
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* @deprecated Replaced with the {@link share} operator. How `share` is used
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* will depend on the connectable observable you created just prior to the
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* `refCount` operator.
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* Details: https://rxjs.dev/deprecations/multicasting
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*/
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export function refCount<T>(): MonoTypeOperatorFunction<T> {
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return operate((source, subscriber) => {
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let connection: Subscription | null = null;
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(source as any)._refCount++;
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const refCounter = createOperatorSubscriber(subscriber, undefined, undefined, undefined, () => {
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if (!source || (source as any)._refCount <= 0 || 0 < --(source as any)._refCount) {
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connection = null;
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return;
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}
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///
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// Compare the local RefCountSubscriber's connection Subscription to the
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// connection Subscription on the shared ConnectableObservable. In cases
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// where the ConnectableObservable source synchronously emits values, and
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// the RefCountSubscriber's downstream Observers synchronously unsubscribe,
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// execution continues to here before the RefCountOperator has a chance to
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// supply the RefCountSubscriber with the shared connection Subscription.
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// For example:
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// ```
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// range(0, 10).pipe(
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// publish(),
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// refCount(),
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// take(5),
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// )
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// .subscribe();
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// ```
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// In order to account for this case, RefCountSubscriber should only dispose
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// the ConnectableObservable's shared connection Subscription if the
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// connection Subscription exists, *and* either:
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// a. RefCountSubscriber doesn't have a reference to the shared connection
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// Subscription yet, or,
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// b. RefCountSubscriber's connection Subscription reference is identical
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// to the shared connection Subscription
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///
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const sharedConnection = (source as any)._connection;
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const conn = connection;
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connection = null;
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if (sharedConnection && (!conn || sharedConnection === conn)) {
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sharedConnection.unsubscribe();
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}
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subscriber.unsubscribe();
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});
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source.subscribe(refCounter);
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if (!refCounter.closed) {
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connection = (source as ConnectableObservable<T>).connect();
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}
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});
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}
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