import { Observable } from '../Observable';
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import { Operator } from '../Operator';
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import { Subscriber } from '../Subscriber';
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import { async } from '../scheduler/async';
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import { MonoTypeOperatorFunction, SchedulerAction, SchedulerLike, TeardownLogic } from '../types';
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/**
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* Emits the most recently emitted value from the source Observable within
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* periodic time intervals.
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*
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* <span class="informal">Samples the source Observable at periodic time
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* intervals, emitting what it samples.</span>
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*
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* 
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*
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* `sampleTime` periodically looks at the source Observable and emits whichever
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* value it has most recently emitted since the previous sampling, unless the
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* source has not emitted anything since the previous sampling. The sampling
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* happens periodically in time every `period` milliseconds (or the time unit
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* defined by the optional `scheduler` argument). The sampling starts as soon as
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* the output Observable is subscribed.
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*
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* ## Example
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* Every second, emit the most recent click at most once
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* ```ts
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* import { fromEvent } from 'rxjs';
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* import { sampleTime } from 'rxjs/operators';
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*
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* const clicks = fromEvent(document, 'click');
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* const result = clicks.pipe(sampleTime(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 auditTime}
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* @see {@link debounceTime}
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* @see {@link delay}
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* @see {@link sample}
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* @see {@link throttleTime}
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*
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* @param {number} period The sampling period expressed in milliseconds or the
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* time unit determined internally by the optional `scheduler`.
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* @param {SchedulerLike} [scheduler=async] The {@link SchedulerLike} to use for
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* managing the timers that handle the sampling.
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* @return {Observable<T>} An Observable that emits the results of sampling the
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* values emitted by the source Observable at the specified time interval.
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* @method sampleTime
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* @owner Observable
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*/
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export function sampleTime<T>(period: number, scheduler: SchedulerLike = async): MonoTypeOperatorFunction<T> {
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return (source: Observable<T>) => source.lift(new SampleTimeOperator(period, scheduler));
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}
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class SampleTimeOperator<T> implements Operator<T, T> {
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constructor(private period: number,
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private scheduler: SchedulerLike) {
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}
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call(subscriber: Subscriber<T>, source: any): TeardownLogic {
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return source.subscribe(new SampleTimeSubscriber(subscriber, this.period, this.scheduler));
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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 SampleTimeSubscriber<T> extends Subscriber<T> {
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lastValue: T;
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hasValue: boolean = false;
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constructor(destination: Subscriber<T>,
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private period: number,
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private scheduler: SchedulerLike) {
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super(destination);
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this.add(scheduler.schedule(dispatchNotification, period, { subscriber: this, period }));
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}
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protected _next(value: T) {
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this.lastValue = value;
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this.hasValue = true;
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}
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notifyNext() {
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if (this.hasValue) {
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this.hasValue = false;
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this.destination.next(this.lastValue);
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}
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}
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}
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function dispatchNotification<T>(this: SchedulerAction<any>, state: any) {
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let { subscriber, period } = state;
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subscriber.notifyNext();
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this.schedule(state, period);
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}
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