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