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import { Operator } from '../Operator';
import { Observable } from '../Observable';
import { Subscriber } from '../Subscriber';
import { Subscription } from '../Subscription';
import { OuterSubscriber } from '../OuterSubscriber';
import { InnerSubscriber } from '../InnerSubscriber';
import { subscribeToResult } from '../util/subscribeToResult';
import { MonoTypeOperatorFunction, SubscribableOrPromise, TeardownLogic } from '../types';
export interface ThrottleConfig {
leading?: boolean;
trailing?: boolean;
}
export const defaultThrottleConfig: ThrottleConfig = {
leading: true,
trailing: false
};
/**
* Emits a value from the source Observable, then ignores subsequent source
* values for a duration determined by another Observable, then repeats this
* process.
*
* <span class="informal">It's like {@link throttleTime}, but the silencing
* duration is determined by a second Observable.</span>
*
* 
*
* `throttle` emits the source Observable values on the output Observable
* when its internal timer is disabled, and ignores source values when the timer
* is enabled. Initially, the timer is disabled. As soon as the first source
* value arrives, it is forwarded to the output Observable, and then the timer
* is enabled by calling the `durationSelector` function with the source value,
* which returns the "duration" Observable. When the duration Observable emits a
* value or completes, the timer is disabled, and this process repeats for the
* next source value.
*
* ## Example
* Emit clicks at a rate of at most one click per second
* ```javascript
* import { fromEvent } from 'rxjs';
* import { throttle } from 'rxjs/operators';
*
* const clicks = fromEvent(document, 'click');
* const result = clicks.pipe(throttle(ev => interval(1000)));
* result.subscribe(x => console.log(x));
* ```
*
* @see {@link audit}
* @see {@link debounce}
* @see {@link delayWhen}
* @see {@link sample}
* @see {@link throttleTime}
*
* @param {function(value: T): SubscribableOrPromise} durationSelector A function
* that receives a value from the source Observable, for computing the silencing
* duration for each source value, returned as an Observable or a Promise.
* @param {Object} config a configuration object to define `leading` and `trailing` behavior. Defaults
* to `{ leading: true, trailing: false }`.
* @return {Observable<T>} An Observable that performs the throttle operation to
* limit the rate of emissions from the source.
* @method throttle
* @owner Observable
*/
export function throttle<T>(durationSelector: (value: T) => SubscribableOrPromise<any>,
config: ThrottleConfig = defaultThrottleConfig): MonoTypeOperatorFunction<T> {
return (source: Observable<T>) => source.lift(new ThrottleOperator(durationSelector, config.leading, config.trailing));
}
class ThrottleOperator<T> implements Operator<T, T> {
constructor(private durationSelector: (value: T) => SubscribableOrPromise<any>,
private leading: boolean,
private trailing: boolean) {
}
call(subscriber: Subscriber<T>, source: any): TeardownLogic {
return source.subscribe(
new ThrottleSubscriber(subscriber, this.durationSelector, this.leading, this.trailing)
);
}
}
/**
* We need this JSDoc comment for affecting ESDoc
* @ignore
* @extends {Ignored}
*/
class ThrottleSubscriber<T, R> extends OuterSubscriber<T, R> {
private _throttled: Subscription;
private _sendValue: T;
private _hasValue = false;
constructor(protected destination: Subscriber<T>,
private durationSelector: (value: T) => SubscribableOrPromise<number>,
private _leading: boolean,
private _trailing: boolean) {
super(destination);
}
protected _next(value: T): void {
this._hasValue = true;
this._sendValue = value;
if (!this._throttled) {
if (this._leading) {
this.send();
} else {
this.throttle(value);
}
}
}
private send() {
const { _hasValue, _sendValue } = this;
if (_hasValue) {
this.destination.next(_sendValue);
this.throttle(_sendValue);
}
this._hasValue = false;
this._sendValue = null;
}
private throttle(value: T): void {
const duration = this.tryDurationSelector(value);
if (!!duration) {
this.add(this._throttled = subscribeToResult(this, duration));
}
}
private tryDurationSelector(value: T): SubscribableOrPromise<any> {
try {
return this.durationSelector(value);
} catch (err) {
this.destination.error(err);
return null;
}
}
private throttlingDone() {
const { _throttled, _trailing } = this;
if (_throttled) {
_throttled.unsubscribe();
}
this._throttled = null;
if (_trailing) {
this.send();
}
}
notifyNext(outerValue: T, innerValue: R,
outerIndex: number, innerIndex: number,
innerSub: InnerSubscriber<T, R>): void {
this.throttlingDone();
}
notifyComplete(): void {
this.throttlingDone();
}
}
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