import { Operator } from '../Operator';
import { Observable, SubscribableOrPromise } from '../Observable';
import { Subscriber } from '../Subscriber';
import { Subscription, TeardownLogic } from '../Subscription';
import { OuterSubscriber } from '../OuterSubscriber';
import { InnerSubscriber } from '../InnerSubscriber';
import { subscribeToResult } from '../util/subscribeToResult';
import { MonoTypeOperatorFunction } from '../interfaces';
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.
*
* It's like {@link throttleTime}, but the silencing
* duration is determined by a second Observable.
*
*
*
* `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
* var clicks = Rx.Observable.fromEvent(document, 'click');
* var result = clicks.throttle(ev => Rx.Observable.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} An Observable that performs the throttle operation to
* limit the rate of emissions from the source.
* @method throttle
* @owner Observable
*/
export function throttle(durationSelector: (value: T) => SubscribableOrPromise,
config: ThrottleConfig = defaultThrottleConfig): MonoTypeOperatorFunction {
return (source: Observable) => source.lift(new ThrottleOperator(durationSelector, config.leading, config.trailing));
}
class ThrottleOperator implements Operator {
constructor(private durationSelector: (value: T) => SubscribableOrPromise,
private leading: boolean,
private trailing: boolean) {
}
call(subscriber: Subscriber, 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 extends OuterSubscriber {
private throttled: Subscription;
private _trailingValue: T;
private _hasTrailingValue = false;
constructor(protected destination: Subscriber,
private durationSelector: (value: T) => SubscribableOrPromise,
private _leading: boolean,
private _trailing: boolean) {
super(destination);
}
protected _next(value: T): void {
if (this.throttled) {
if (this._trailing) {
this._hasTrailingValue = true;
this._trailingValue = value;
}
} else {
const duration = this.tryDurationSelector(value);
if (duration) {
this.add(this.throttled = subscribeToResult(this, duration));
}
if (this._leading) {
this.destination.next(value);
if (this._trailing) {
this._hasTrailingValue = true;
this._trailingValue = value;
}
}
}
}
private tryDurationSelector(value: T): SubscribableOrPromise {
try {
return this.durationSelector(value);
} catch (err) {
this.destination.error(err);
return null;
}
}
/** @deprecated internal use only */ _unsubscribe() {
const { throttled, _trailingValue, _hasTrailingValue, _trailing } = this;
this._trailingValue = null;
this._hasTrailingValue = false;
if (throttled) {
this.remove(throttled);
this.throttled = null;
throttled.unsubscribe();
}
}
private _sendTrailing() {
const { destination, throttled, _trailing, _trailingValue, _hasTrailingValue } = this;
if (throttled && _trailing && _hasTrailingValue) {
destination.next(_trailingValue);
this._trailingValue = null;
this._hasTrailingValue = false;
}
}
notifyNext(outerValue: T, innerValue: R,
outerIndex: number, innerIndex: number,
innerSub: InnerSubscriber): void {
this._sendTrailing();
this._unsubscribe();
}
notifyComplete(): void {
this._sendTrailing();
this._unsubscribe();
}
}