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