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

Author: benlesh

src/Rx.ts

@@ -158,7 +158,7 @@ export {ObjectUnsubscribedError} from './util/ObjectUnsubscribedError';
 export {TimeoutError} from './util/TimeoutError';
 export {UnsubscriptionError} from './util/UnsubscriptionError';
 export {TimeInterval} from './operator/timeInterval';
-export {Timestamp} from './operator/timestamp';
+export {Timestamp} from './operators/timestamp';
 export {TestScheduler} from './testing/TestScheduler';
 export {VirtualTimeScheduler} from './scheduler/VirtualTimeScheduler';
 export {AjaxRequest, AjaxResponse, AjaxError, AjaxTimeoutError} from './observable/dom/AjaxObservable';

src/operator/timestamp.ts

@@ -1,41 +1,14 @@
-import { Operator } from '../Operator';
 import { Observable } from '../Observable';
-import { Subscriber } from '../Subscriber';
 import { IScheduler } from '../Scheduler';
 import { async } from '../scheduler/async';
-
+import { timestamp as higherOrder } from '../operators';
+import { Timestamp } from '../operators/timestamp';
 /**
  * @param scheduler
  * @return {Observable<Timestamp<any>>|WebSocketSubject<T>|Observable<T>}
  * @method timestamp
  * @owner Observable
  */
 export function timestamp<T>(this: Observable<T>, scheduler: IScheduler = async): Observable<Timestamp<T>> {
-  return this.lift(new TimestampOperator(scheduler));
-}
-
-export class Timestamp<T> {
-  constructor(public value: T, public timestamp: number) {
-  }
-};
-
-class TimestampOperator<T> implements Operator<T, Timestamp<T>> {
-  constructor(private scheduler: IScheduler) {
-  }
-
-  call(observer: Subscriber<Timestamp<T>>, source: any): any {
-    return source.subscribe(new TimestampSubscriber(observer, this.scheduler));
-  }
-}
-
-class TimestampSubscriber<T> extends Subscriber<T> {
-  constructor(destination: Subscriber<Timestamp<T>>, private scheduler: IScheduler) {
-    super(destination);
-  }
-
-  protected _next(value: T): void {
-    const now = this.scheduler.now();
-
-    this.destination.next(new Timestamp(value, now));
-  }
+  return higherOrder(scheduler)(this);
 }

src/operators/index.ts

@@ -22,6 +22,7 @@ export { switchAll } from './switchAll';
 export { switchMap } from './switchMap';
 export { takeLast } from './takeLast';
 export { tap } from './tap';
+export { timestamp } from './timestamp';
 export { toArray } from './toArray';
 export { window } from './window';
 export { windowCount } from './windowCount';

src/operators/timestamp.ts

@@ -0,0 +1,21 @@
+
+import { IScheduler } from '../Scheduler';
+import { async } from '../scheduler/async';
+import { OperatorFunction } from '../interfaces';
+import { map } from './map';
+
+/**
+ * @param scheduler
+ * @return {Observable<Timestamp<any>>|WebSocketSubject<T>|Observable<T>}
+ * @method timestamp
+ * @owner Observable
+ */
+export function timestamp<T>(scheduler: IScheduler = async): OperatorFunction<T, Timestamp<T>> {
+  return map((value: T) => new Timestamp(value, scheduler.now()));
+  // return (source: Observable<T>) => source.lift(new TimestampOperator(scheduler));
+}
+
+export class Timestamp<T> {
+  constructor(public value: T, public timestamp: number) {
+  }
+};