import { OperatorFunction, TimestampProvider, Timestamp } from '../types';
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import { dateTimestampProvider } from '../scheduler/dateTimestampProvider';
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import { map } from './map';
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/**
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* Attaches a timestamp to each item emitted by an observable indicating when it was emitted
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*
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* The `timestamp` operator maps the *source* observable stream to an object of type
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* `{value: T, timestamp: R}`. The properties are generically typed. The `value` property contains the value
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* and type of the *source* observable. The `timestamp` is generated by the schedulers `now` function. By
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* default, it uses the `asyncScheduler` which simply returns `Date.now()` (milliseconds since 1970/01/01
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* 00:00:00:000) and therefore is of type `number`.
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*
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* 
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*
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* ## Example
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*
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* In this example there is a timestamp attached to the document's click events
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*
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* ```ts
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* import { fromEvent, timestamp } from 'rxjs';
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*
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* const clickWithTimestamp = fromEvent(document, 'click').pipe(
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* timestamp()
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* );
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*
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* // Emits data of type { value: PointerEvent, timestamp: number }
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* clickWithTimestamp.subscribe(data => {
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* console.log(data);
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* });
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* ```
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*
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* @param timestampProvider An object with a `now()` method used to get the current timestamp.
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* @return A function that returns an Observable that attaches a timestamp to
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* each item emitted by the source Observable indicating when it was emitted.
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*/
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export function timestamp<T>(timestampProvider: TimestampProvider = dateTimestampProvider): OperatorFunction<T, Timestamp<T>> {
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return map((value: T) => ({ value, timestamp: timestampProvider.now() }));
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}
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