import { Observable } from '../Observable';
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import { Subject } from '../Subject';
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import { OperatorFunction } 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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* Branch out the source Observable values as a nested Observable with each
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* nested Observable emitting at most `windowSize` values.
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*
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* <span class="informal">It's like {@link bufferCount}, 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 every `startWindowEvery`
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* items, each containing no more than `windowSize` items. When the source
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* Observable completes or encounters an error, the output Observable emits
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* the current window and propagates the notification from the source
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* Observable. If `startWindowEvery` is not provided, then new windows are
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* started immediately at the start of the source and when each window completes
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* with size `windowSize`.
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*
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* ## Examples
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*
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* Ignore every 3rd click event, starting from the first one
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*
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* ```ts
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* import { fromEvent, windowCount, map, skip, mergeAll } from 'rxjs';
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*
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* const clicks = fromEvent(document, 'click');
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* const result = clicks.pipe(
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* windowCount(3),
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* map(win => win.pipe(skip(1))), // skip first of every 3 clicks
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* mergeAll() // flatten the Observable-of-Observables
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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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* Ignore every 3rd click event, starting from the third one
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*
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* ```ts
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* import { fromEvent, windowCount, mergeAll } from 'rxjs';
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*
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* const clicks = fromEvent(document, 'click');
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* const result = clicks.pipe(
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* windowCount(2, 3),
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* mergeAll() // flatten the Observable-of-Observables
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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 windowTime}
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* @see {@link windowToggle}
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* @see {@link windowWhen}
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* @see {@link bufferCount}
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*
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* @param {number} windowSize The maximum number of values emitted by each
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* window.
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* @param {number} [startWindowEvery] Interval at which to start a new window.
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* For example if `startWindowEvery` is `2`, then a new window will be started
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* on every other value from the source. A new window is started at the
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* beginning of the source by default.
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* @return A function that returns an Observable of windows, which in turn are
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* Observable of values.
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*/
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export function windowCount<T>(windowSize: number, startWindowEvery: number = 0): OperatorFunction<T, Observable<T>> {
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const startEvery = startWindowEvery > 0 ? startWindowEvery : windowSize;
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return operate((source, subscriber) => {
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let windows = [new Subject<T>()];
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let starts: number[] = [];
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let count = 0;
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// Open the first window.
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subscriber.next(windows[0].asObservable());
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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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// Emit the value through all current windows.
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// We don't need to create a new window yet, we
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// do that as soon as we close one.
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for (const window of windows) {
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window.next(value);
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}
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// Here we're using the size of the window array to figure
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// out if the oldest window has emitted enough values. We can do this
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// because the size of the window array is a function of the values
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// seen by the subscription. If it's time to close it, we complete
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// it and remove it.
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const c = count - windowSize + 1;
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if (c >= 0 && c % startEvery === 0) {
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windows.shift()!.complete();
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}
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// Look to see if the next count tells us it's time to open a new window.
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// TODO: We need to figure out if this really makes sense. We're technically
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// emitting windows *before* we have a value to emit them for. It's probably
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// more expected that we should be emitting the window when the start
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// count is reached -- not before.
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if (++count % startEvery === 0) {
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const window = new Subject<T>();
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windows.push(window);
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subscriber.next(window.asObservable());
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}
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},
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() => {
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while (windows.length > 0) {
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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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(err) => {
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while (windows.length > 0) {
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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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() => {
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starts = null!;
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windows = null!;
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}
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)
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);
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});
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}
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