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