import { Observable } from '../Observable';
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import { SchedulerLike } from '../types';
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import { iterator as Symbol_iterator } from '../symbol/iterator';
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import { isFunction } from '../util/isFunction';
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import { executeSchedule } from '../util/executeSchedule';
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/**
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* Used in {@link scheduled} to create an observable from an Iterable.
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* @param input The iterable to create an observable from
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* @param scheduler The scheduler to use
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*/
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export function scheduleIterable<T>(input: Iterable<T>, scheduler: SchedulerLike) {
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return new Observable<T>((subscriber) => {
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let iterator: Iterator<T, T>;
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// Schedule the initial creation of the iterator from
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// the iterable. This is so the code in the iterable is
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// not called until the scheduled job fires.
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executeSchedule(subscriber, scheduler, () => {
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// Create the iterator.
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iterator = (input as any)[Symbol_iterator]();
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executeSchedule(
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subscriber,
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scheduler,
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() => {
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let value: T;
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let done: boolean | undefined;
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try {
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// Pull the value out of the iterator
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({ value, done } = iterator.next());
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} catch (err) {
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// We got an error while pulling from the iterator
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subscriber.error(err);
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return;
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}
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if (done) {
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// If it is "done" we just complete. This mimics the
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// behavior of JavaScript's `for..of` consumption of
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// iterables, which will not emit the value from an iterator
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// result of `{ done: true: value: 'here' }`.
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subscriber.complete();
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} else {
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// The iterable is not done, emit the value.
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subscriber.next(value);
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}
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},
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0,
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true
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);
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});
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// During finalization, if we see this iterator has a `return` method,
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// then we know it is a Generator, and not just an Iterator. So we call
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// the `return()` function. This will ensure that any `finally { }` blocks
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// inside of the generator we can hit will be hit properly.
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return () => isFunction(iterator?.return) && iterator.return();
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});
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}
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