import { Observable } from '../Observable';
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import { Subject } from '../Subject';
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import { Subscription } from '../Subscription';
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import { ObservableInput, OperatorFunction } from '../types';
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import { operate } from '../util/lift';
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import { innerFrom } from '../observable/innerFrom';
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import { createOperatorSubscriber } from './OperatorSubscriber';
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import { noop } from '../util/noop';
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import { arrRemove } from '../util/arrRemove';
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/**
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* Branch out the source Observable values as a nested Observable starting from
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* an emission from `openings` and ending when the output of `closingSelector`
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* emits.
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*
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* <span class="informal">It's like {@link bufferToggle}, but emits a nested
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* Observable instead of an array.</span>
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*
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* 
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*
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* Returns an Observable that emits windows of items it collects from the source
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* Observable. The output Observable emits windows that contain those items
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* emitted by the source Observable between the time when the `openings`
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* Observable emits an item and when the Observable returned by
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* `closingSelector` emits an item.
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*
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* ## Example
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*
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* Every other second, emit the click events from the next 500ms
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*
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* ```ts
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* import { fromEvent, interval, windowToggle, EMPTY, mergeAll } from 'rxjs';
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*
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* const clicks = fromEvent(document, 'click');
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* const openings = interval(1000);
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* const result = clicks.pipe(
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* windowToggle(openings, i => i % 2 ? interval(500) : EMPTY),
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* mergeAll()
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* );
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* result.subscribe(x => console.log(x));
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* ```
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*
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* @see {@link window}
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* @see {@link windowCount}
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* @see {@link windowTime}
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* @see {@link windowWhen}
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* @see {@link bufferToggle}
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*
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* @param {Observable<O>} openings An observable of notifications to start new
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* windows.
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* @param {function(value: O): Observable} closingSelector A function that takes
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* the value emitted by the `openings` observable and returns an Observable,
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* which, when it emits a next notification, signals that the
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* associated window should complete.
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* @return A function that returns an Observable of windows, which in turn are
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* Observables.
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*/
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export function windowToggle<T, O>(
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openings: ObservableInput<O>,
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closingSelector: (openValue: O) => ObservableInput<any>
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): OperatorFunction<T, Observable<T>> {
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return operate((source, subscriber) => {
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const windows: Subject<T>[] = [];
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const handleError = (err: any) => {
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while (0 < windows.length) {
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windows.shift()!.error(err);
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}
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subscriber.error(err);
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};
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innerFrom(openings).subscribe(
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createOperatorSubscriber(
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subscriber,
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(openValue) => {
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const window = new Subject<T>();
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windows.push(window);
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const closingSubscription = new Subscription();
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const closeWindow = () => {
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arrRemove(windows, window);
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window.complete();
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closingSubscription.unsubscribe();
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};
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let closingNotifier: Observable<any>;
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try {
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closingNotifier = innerFrom(closingSelector(openValue));
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} catch (err) {
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handleError(err);
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return;
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}
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subscriber.next(window.asObservable());
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closingSubscription.add(closingNotifier.subscribe(createOperatorSubscriber(subscriber, closeWindow, noop, handleError)));
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},
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noop
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)
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);
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// Subscribe to the source to get things started.
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source.subscribe(
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createOperatorSubscriber(
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subscriber,
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(value: T) => {
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// Copy the windows array before we emit to
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// make sure we don't have issues with reentrant code.
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const windowsCopy = windows.slice();
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for (const window of windowsCopy) {
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window.next(value);
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}
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},
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() => {
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// Complete all of our windows before we complete.
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while (0 < windows.length) {
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windows.shift()!.complete();
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}
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subscriber.complete();
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},
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handleError,
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() => {
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// Add this finalization so that all window subjects are
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// disposed of. This way, if a user tries to subscribe
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// to a window *after* the outer subscription has been unsubscribed,
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// they will get an error, instead of waiting forever to
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// see if a value arrives.
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while (0 < windows.length) {
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windows.shift()!.unsubscribe();
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}
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}
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)
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);
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});
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}
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