feat(auditTime): add higher-order lettable version of auditTime

Author: benlesh

src/operator/auditTime.ts

@@ -1,9 +1,7 @@
 import { async } from '../scheduler/async';
-import { Operator } from '../Operator';
 import { IScheduler } from '../Scheduler';
-import { Subscriber } from '../Subscriber';
 import { Observable } from '../Observable';
-import { Subscription, TeardownLogic } from '../Subscription';
+import { auditTime as higherOrder } from '../operators';
 
 /**
  * Ignores source values for `duration` milliseconds, then emits the most recent
@@ -48,59 +46,5 @@ import { Subscription, TeardownLogic } from '../Subscription';
  * @owner Observable
  */
 export function auditTime<T>(this: Observable<T>, duration: number, scheduler: IScheduler = async): Observable<T> {
-  return this.lift(new AuditTimeOperator(duration, scheduler));
-}
-
-class AuditTimeOperator<T> implements Operator<T, T> {
-  constructor(private duration: number,
-              private scheduler: IScheduler) {
-  }
-
-  call(subscriber: Subscriber<T>, source: any): TeardownLogic {
-    return source.subscribe(new AuditTimeSubscriber(subscriber, this.duration, this.scheduler));
-  }
-}
-
-/**
- * We need this JSDoc comment for affecting ESDoc.
- * @ignore
- * @extends {Ignored}
- */
-class AuditTimeSubscriber<T> extends Subscriber<T> {
-
-  private value: T;
-  private hasValue: boolean = false;
-  private throttled: Subscription;
-
-  constructor(destination: Subscriber<T>,
-              private duration: number,
-              private scheduler: IScheduler) {
-    super(destination);
-  }
-
-  protected _next(value: T): void {
-    this.value = value;
-    this.hasValue = true;
-    if (!this.throttled) {
-      this.add(this.throttled = this.scheduler.schedule(dispatchNext, this.duration, this));
-    }
-  }
-
-  clearThrottle(): void {
-    const { value, hasValue, throttled } = this;
-    if (throttled) {
-      this.remove(throttled);
-      this.throttled = null;
-      throttled.unsubscribe();
-    }
-    if (hasValue) {
-      this.value = null;
-      this.hasValue = false;
-      this.destination.next(value);
-    }
-  }
-}
-
-function dispatchNext<T>(subscriber: AuditTimeSubscriber<T>): void {
-  subscriber.clearThrottle();
-}
+  return higherOrder(duration, scheduler)(this);
+}

src/operators/auditTime.ts

@@ -0,0 +1,51 @@
+import { async } from '../scheduler/async';
+import { IScheduler } from '../Scheduler';
+import { audit } from './audit';
+import { timer } from '../observable/timer';
+import { MonoTypeOperatorFunction } from '../interfaces';
+
+/**
+ * Ignores source values for `duration` milliseconds, then emits the most recent
+ * value from the source Observable, then repeats this process.
+ *
+ * <span class="informal">When it sees a source values, it ignores that plus
+ * the next ones for `duration` milliseconds, and then it emits the most recent
+ * value from the source.</span>
+ *
+ * <img src="./img/auditTime.png" width="100%">
+ *
+ * `auditTime` is similar to `throttleTime`, but emits the last value from the
+ * silenced time window, instead of the first value. `auditTime` emits the most
+ * recent value from the source Observable on the output Observable as soon as
+ * its internal timer becomes disabled, and ignores source values while the
+ * timer is enabled. Initially, the timer is disabled. As soon as the first
+ * source value arrives, the timer is enabled. After `duration` milliseconds (or
+ * the time unit determined internally by the optional `scheduler`) has passed,
+ * the timer is disabled, then the most recent source value is emitted on the
+ * output Observable, and this process repeats for the next source value.
+ * Optionally takes a {@link IScheduler} for managing timers.
+ *
+ * @example <caption>Emit clicks at a rate of at most one click per second</caption>
+ * var clicks = Rx.Observable.fromEvent(document, 'click');
+ * var result = clicks.auditTime(1000);
+ * result.subscribe(x => console.log(x));
+ *
+ * @see {@link audit}
+ * @see {@link debounceTime}
+ * @see {@link delay}
+ * @see {@link sampleTime}
+ * @see {@link throttleTime}
+ *
+ * @param {number} duration Time to wait before emitting the most recent source
+ * value, measured in milliseconds or the time unit determined internally
+ * by the optional `scheduler`.
+ * @param {Scheduler} [scheduler=async] The {@link IScheduler} to use for
+ * managing the timers that handle the rate-limiting behavior.
+ * @return {Observable<T>} An Observable that performs rate-limiting of
+ * emissions from the source Observable.
+ * @method auditTime
+ * @owner Observable
+ */
+export function auditTime<T>(duration: number, scheduler: IScheduler = async): MonoTypeOperatorFunction<T> {
+  return audit(() => timer(duration, scheduler));
+}

src/operators/index.ts

@@ -1,4 +1,5 @@
 export { audit } from './audit';
+export { auditTime } from './auditTime';
 export { catchError } from './catchError';
 export { concat } from './concat';
 export { concatAll } from './concatAll';