import { Observable } from '../Observable';
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import { Subscriber } from '../Subscriber';
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import { OperatorFunction } from '../types';
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import { isFunction } from './isFunction';
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/**
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* Used to determine if an object is an Observable with a lift function.
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*/
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export function hasLift(source: any): source is { lift: InstanceType<typeof Observable>['lift'] } {
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return isFunction(source?.lift);
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}
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/**
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* Creates an `OperatorFunction`. Used to define operators throughout the library in a concise way.
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* @param init The logic to connect the liftedSource to the subscriber at the moment of subscription.
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*/
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export function operate<T, R>(
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init: (liftedSource: Observable<T>, subscriber: Subscriber<R>) => (() => void) | void
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): OperatorFunction<T, R> {
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return (source: Observable<T>) => {
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if (hasLift(source)) {
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return source.lift(function (this: Subscriber<R>, liftedSource: Observable<T>) {
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try {
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return init(liftedSource, this);
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} catch (err) {
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this.error(err);
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}
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});
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}
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throw new TypeError('Unable to lift unknown Observable type');
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};
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}
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