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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/**
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* Emits a value from the source Observable only after a particular time span
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* determined by another Observable has passed without another source emission.
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*
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* <span class="informal">It's like {@link debounceTime}, but the time span of
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* emission silence is determined by a second Observable.</span>
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*
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* 
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*
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* `debounce` delays values emitted by the source Observable, but drops previous
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* pending delayed emissions if a new value arrives on the source Observable.
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* This operator keeps track of the most recent value from the source
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* Observable, and spawns a duration Observable by calling the
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* `durationSelector` function. The value is emitted only when the duration
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* Observable emits a value or completes, and if no other value was emitted on
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* the source Observable since the duration Observable was spawned. If a new
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* value appears before the duration Observable emits, the previous value will
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* be dropped and will not be emitted on the output Observable.
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*
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* Like {@link debounceTime}, this is a rate-limiting operator, and also a
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* delay-like operator since output emissions do not necessarily occur at the
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* same time as they did on the source Observable.
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*
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* ## Example
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* Emit the most recent click after a burst of clicks
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* ```ts
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* import { fromEvent, interval } from 'rxjs';
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* import { debounce } from 'rxjs/operators';
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*
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* const clicks = fromEvent(document, 'click');
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* const result = clicks.pipe(debounce(() => 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 debounceTime}
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* @see {@link delayWhen}
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* @see {@link throttle}
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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 timeout
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* duration for each source value, returned as an Observable or a Promise.
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* @return {Observable} An Observable that delays the emissions of the source
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* Observable by the specified duration Observable returned by
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* `durationSelector`, and may drop some values if they occur too frequently.
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* @method debounce
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* @owner Observable
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*/
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export function debounce<T>(durationSelector: (value: T) => SubscribableOrPromise<any>): MonoTypeOperatorFunction<T> {
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return (source: Observable<T>) => source.lift(new DebounceOperator(durationSelector));
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}
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class DebounceOperator<T> implements Operator<T, T> {
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constructor(private durationSelector: (value: T) => SubscribableOrPromise<any>) {
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}
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call(subscriber: Subscriber<T>, source: any): TeardownLogic {
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return source.subscribe(new DebounceSubscriber(subscriber, this.durationSelector));
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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 DebounceSubscriber<T, R> extends SimpleOuterSubscriber<T, R> {
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private value?: T;
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private hasValue = false;
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private durationSubscription?: Subscription;
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constructor(destination: Subscriber<R>,
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private durationSelector: (value: T) => SubscribableOrPromise<any>) {
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super(destination);
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}
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protected _next(value: T): void {
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try {
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const result = this.durationSelector.call(this, value);
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if (result) {
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this._tryNext(value, result);
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}
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} catch (err) {
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this.destination.error!(err);
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}
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}
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protected _complete(): void {
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this.emitValue();
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this.destination.complete!();
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}
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private _tryNext(value: T, duration: SubscribableOrPromise<any>): void {
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let subscription = this.durationSubscription;
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this.value = value;
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this.hasValue = true;
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if (subscription) {
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subscription.unsubscribe();
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this.remove(subscription);
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}
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subscription = innerSubscribe(duration, new SimpleInnerSubscriber(this));
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if (subscription && !subscription.closed) {
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this.add(this.durationSubscription = subscription);
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}
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}
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notifyNext(): void {
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this.emitValue();
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}
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notifyComplete(): void {
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this.emitValue();
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}
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emitValue(): void {
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if (this.hasValue) {
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const value = this.value;
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const subscription = this.durationSubscription;
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if (subscription) {
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this.durationSubscription = undefined;
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subscription.unsubscribe();
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this.remove(subscription);
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}
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// This must be done *before* passing the value
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// along to the destination because it's possible for
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// the value to synchronously re-enter this operator
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// recursively if the duration selector Observable
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// emits synchronously
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this.value = undefined;
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this.hasValue = false;
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super._next(value!);
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}
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}
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}
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