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import { Observable } from '../Observable';
import { Operator } from '../Operator';
import { Subscriber } from '../Subscriber';
import { tryCatch } from '../util/tryCatch';
import { errorObject } from '../util/errorObject';
import { Subscription } from '../Subscription';
import { OuterSubscriber } from '../OuterSubscriber';
import { InnerSubscriber } from '../InnerSubscriber';
import { subscribeToResult } from '../util/subscribeToResult';
import { MonoTypeOperatorFunction, OperatorFunction, ObservableInput, SchedulerLike } from '../types';
/* tslint:disable:max-line-length */
export function expand<T, R>(project: (value: T, index: number) => ObservableInput<R>, concurrent?: number, scheduler?: SchedulerLike): OperatorFunction<T, R>;
export function expand<T>(project: (value: T, index: number) => ObservableInput<T>, concurrent?: number, scheduler?: SchedulerLike): MonoTypeOperatorFunction<T>;
/* tslint:enable:max-line-length */
/**
* Recursively projects each source value to an Observable which is merged in
* the output Observable.
*
* <span class="informal">It's similar to {@link mergeMap}, but applies the
* projection function to every source value as well as every output value.
* It's recursive.</span>
*
* 
*
* Returns an Observable that emits items based on applying a function that you
* supply to each item emitted by the source Observable, where that function
* returns an Observable, and then merging those resulting Observables and
* emitting the results of this merger. *Expand* will re-emit on the output
* Observable every source value. Then, each output value is given to the
* `project` function which returns an inner Observable to be merged on the
* output Observable. Those output values resulting from the projection are also
* given to the `project` function to produce new output values. This is how
* *expand* behaves recursively.
*
* ## Example
* Start emitting the powers of two on every click, at most 10 of them
* ```javascript
* const clicks = fromEvent(document, 'click');
* const powersOfTwo = clicks.pipe(
* mapTo(1),
* expand(x => of(2 * x).pipe(delay(1000))),
* take(10),
* );
* powersOfTwo.subscribe(x => console.log(x));
* ```
*
* @see {@link mergeMap}
* @see {@link mergeScan}
*
* @param {function(value: T, index: number) => Observable} project A function
* that, when applied to an item emitted by the source or the output Observable,
* returns an Observable.
* @param {number} [concurrent=Number.POSITIVE_INFINITY] Maximum number of input
* Observables being subscribed to concurrently.
* @param {SchedulerLike} [scheduler=null] The {@link SchedulerLike} to use for subscribing to
* each projected inner Observable.
* @return {Observable} An Observable that emits the source values and also
* result of applying the projection function to each value emitted on the
* output Observable and and merging the results of the Observables obtained
* from this transformation.
* @method expand
* @owner Observable
*/
export function expand<T, R>(project: (value: T, index: number) => ObservableInput<R>,
concurrent: number = Number.POSITIVE_INFINITY,
scheduler: SchedulerLike = undefined): OperatorFunction<T, R> {
concurrent = (concurrent || 0) < 1 ? Number.POSITIVE_INFINITY : concurrent;
return (source: Observable<T>) => source.lift(new ExpandOperator(project, concurrent, scheduler));
}
export class ExpandOperator<T, R> implements Operator<T, R> {
constructor(private project: (value: T, index: number) => ObservableInput<R>,
private concurrent: number,
private scheduler: SchedulerLike) {
}
call(subscriber: Subscriber<R>, source: any): any {
return source.subscribe(new ExpandSubscriber(subscriber, this.project, this.concurrent, this.scheduler));
}
}
interface DispatchArg<T, R> {
subscriber: ExpandSubscriber<T, R>;
result: ObservableInput<R>;
value: any;
index: number;
}
/**
* We need this JSDoc comment for affecting ESDoc.
* @ignore
* @extends {Ignored}
*/
export class ExpandSubscriber<T, R> extends OuterSubscriber<T, R> {
private index: number = 0;
private active: number = 0;
private hasCompleted: boolean = false;
private buffer: any[];
constructor(destination: Subscriber<R>,
private project: (value: T, index: number) => ObservableInput<R>,
private concurrent: number,
private scheduler: SchedulerLike) {
super(destination);
if (concurrent < Number.POSITIVE_INFINITY) {
this.buffer = [];
}
}
private static dispatch<T, R>(arg: DispatchArg<T, R>): void {
const {subscriber, result, value, index} = arg;
subscriber.subscribeToProjection(result, value, index);
}
protected _next(value: any): void {
const destination = this.destination;
if (destination.closed) {
this._complete();
return;
}
const index = this.index++;
if (this.active < this.concurrent) {
destination.next(value);
let result = tryCatch(this.project)(value, index);
if (result === errorObject) {
destination.error(errorObject.e);
} else if (!this.scheduler) {
this.subscribeToProjection(result, value, index);
} else {
const state: DispatchArg<T, R> = { subscriber: this, result, value, index };
const destination = this.destination as Subscription;
destination.add(this.scheduler.schedule<DispatchArg<T, R>>(ExpandSubscriber.dispatch, 0, state));
}
} else {
this.buffer.push(value);
}
}
private subscribeToProjection(result: any, value: T, index: number): void {
this.active++;
const destination = this.destination as Subscription;
destination.add(subscribeToResult<T, R>(this, result, value, index));
}
protected _complete(): void {
this.hasCompleted = true;
if (this.hasCompleted && this.active === 0) {
this.destination.complete();
}
this.unsubscribe();
}
notifyNext(outerValue: T, innerValue: R,
outerIndex: number, innerIndex: number,
innerSub: InnerSubscriber<T, R>): void {
this._next(innerValue);
}
notifyComplete(innerSub: Subscription): void {
const buffer = this.buffer;
const destination = this.destination as Subscription;
destination.remove(innerSub);
this.active--;
if (buffer && buffer.length > 0) {
this._next(buffer.shift());
}
if (this.hasCompleted && this.active === 0) {
this.destination.complete();
}
}
}
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