import { Observable } from '../Observable';
import { OperatorFunction } from '../types';
/**
 * Branch out the source Observable values as a nested Observable whenever
 * `windowBoundaries` emits.
 *
 * <span class="informal">It's like {@link buffer}, but emits a nested Observable
 * instead of an array.</span>
 *
 * ![](window.png)
 *
 * Returns an Observable that emits windows of items it collects from the source
 * Observable. The output Observable emits connected, non-overlapping
 * windows. It emits the current window and opens a new one whenever the
 * Observable `windowBoundaries` emits an item. Because each window is an
 * Observable, the output is a higher-order Observable.
 *
 * ## Example
 * In every window of 1 second each, emit at most 2 click events
 * ```javascript
 * const clicks = fromEvent(document, 'click');
 * const interval = interval(1000);
 * const result = clicks.pipe(
 *   window(interval),
 *   map(win => win.take(2)), // each window has at most 2 emissions
 *   mergeAll(),              // flatten the Observable-of-Observables
 * );
 * result.subscribe(x => console.log(x));
 * ```
 * @see {@link windowCount}
 * @see {@link windowTime}
 * @see {@link windowToggle}
 * @see {@link windowWhen}
 * @see {@link buffer}
 *
 * @param {Observable<any>} windowBoundaries An Observable that completes the
 * previous window and starts a new window.
 * @return {Observable<Observable<T>>} An Observable of windows, which are
 * Observables emitting values of the source Observable.
 * @method window
 * @owner Observable
 */
export declare function window<T>(windowBoundaries: Observable<any>): OperatorFunction<T, Observable<T>>;