import { Observable } from '../Observable';
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import { SchedulerAction, SchedulerLike } from '../types';
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import { async } from '../scheduler/async';
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import { isNumeric } from '../util/isNumeric';
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import { isScheduler } from '../util/isScheduler';
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import { Subscriber } from '../Subscriber';
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/**
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* Creates an Observable that starts emitting after an `dueTime` and
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* emits ever increasing numbers after each `period` of time thereafter.
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*
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* <span class="informal">Its like {@link index/interval}, but you can specify when
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* should the emissions start.</span>
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*
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* 
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*
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* `timer` returns an Observable that emits an infinite sequence of ascending
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* integers, with a constant interval of time, `period` of your choosing
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* between those emissions. The first emission happens after the specified
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* `dueTime`. The initial delay may be a `Date`. By default, this
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* operator uses the {@link asyncScheduler} {@link SchedulerLike} to provide a notion of time, but you
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* may pass any {@link SchedulerLike} to it. If `period` is not specified, the output
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* Observable emits only one value, `0`. Otherwise, it emits an infinite
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* sequence.
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*
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* ## Examples
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* ### Emits ascending numbers, one every second (1000ms), starting after 3 seconds
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* ```ts
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* import { timer } from 'rxjs';
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*
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* const numbers = timer(3000, 1000);
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* numbers.subscribe(x => console.log(x));
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* ```
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*
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* ### Emits one number after five seconds
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* ```ts
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* import { timer } from 'rxjs';
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*
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* const numbers = timer(5000);
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* numbers.subscribe(x => console.log(x));
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* ```
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* @see {@link index/interval}
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* @see {@link delay}
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*
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* @param {number|Date} [dueTime] The initial delay time specified as a Date object or as an integer denoting
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* milliseconds to wait before emitting the first value of 0`.
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* @param {number|SchedulerLike} [periodOrScheduler] The period of time between emissions of the
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* subsequent numbers.
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* @param {SchedulerLike} [scheduler=async] The {@link SchedulerLike} to use for scheduling
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* the emission of values, and providing a notion of "time".
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* @return {Observable} An Observable that emits a `0` after the
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* `dueTime` and ever increasing numbers after each `period` of time
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* thereafter.
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* @static true
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* @name timer
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* @owner Observable
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*/
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export function timer(dueTime: number | Date = 0,
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periodOrScheduler?: number | SchedulerLike,
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scheduler?: SchedulerLike): Observable<number> {
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let period = -1;
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if (isNumeric(periodOrScheduler)) {
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period = Number(periodOrScheduler) < 1 && 1 || Number(periodOrScheduler);
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} else if (isScheduler(periodOrScheduler)) {
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scheduler = periodOrScheduler as any;
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}
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if (!isScheduler(scheduler)) {
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scheduler = async;
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}
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return new Observable(subscriber => {
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const due = isNumeric(dueTime)
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? (dueTime as number)
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: (+dueTime - scheduler.now());
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return scheduler.schedule(dispatch, due, {
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index: 0, period, subscriber
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});
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});
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}
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interface TimerState {
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index: number;
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period: number;
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subscriber: Subscriber<number>;
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}
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function dispatch(this: SchedulerAction<TimerState>, state: TimerState) {
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const { index, period, subscriber } = state;
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subscriber.next(index);
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if (subscriber.closed) {
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return;
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} else if (period === -1) {
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return subscriber.complete();
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}
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state.index = index + 1;
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this.schedule(state, period);
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}
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