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
 * ```ts
 * import { fromEvent, interval } from 'rxjs';
 * import { window, mergeAll, map, take } from 'rxjs/operators';
 *
 *  const clicks = fromEvent(document, 'click');
 *  const sec = interval(1000);
 *  const result = clicks.pipe(
 *      window(sec),
 *      map(win => win.pipe(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>>;