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import { Operator } from '../Operator';
import { Observable } from '../Observable';
import { Subscriber } from '../Subscriber';
import { Subscription } from '../Subscription';
import { OuterSubscriber } from '../OuterSubscriber';
import { InnerSubscriber } from '../InnerSubscriber';
import { subscribeToResult } from '../util/subscribeToResult';
import { ObservableInput, OperatorFunction, ObservedValueOf } from '../types';
import { map } from './map';
import { from } from '../observable/from';
/* tslint:disable:max-line-length */
export function switchMap<T, O extends ObservableInput<any>>(project: (value: T, index: number) => O): OperatorFunction<T, ObservedValueOf<O>>;
/** @deprecated resultSelector is no longer supported, use inner map instead */
export function switchMap<T, O extends ObservableInput<any>>(project: (value: T, index: number) => O, resultSelector: undefined): OperatorFunction<T, ObservedValueOf<O>>;
/** @deprecated resultSelector is no longer supported, use inner map instead */
export function switchMap<T, R, O extends ObservableInput<any>>(project: (value: T, index: number) => O, resultSelector: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R): OperatorFunction<T, R>;
/* tslint:enable:max-line-length */
/**
* Projects each source value to an Observable which is merged in the output
* Observable, emitting values only from the most recently projected Observable.
*
* <span class="informal">Maps each value to an Observable, then flattens all of
* these inner Observables.</span>
*
* ![](switchMap.png)
*
* 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 (so-called "inner") Observable. Each time it observes one of these
* inner Observables, the output Observable begins emitting the items emitted by
* that inner Observable. When a new inner Observable is emitted, `switchMap`
* stops emitting items from the earlier-emitted inner Observable and begins
* emitting items from the new one. It continues to behave like this for
* subsequent inner Observables.
*
* ## Example
* Generate new Observable according to source Observable values
* ```typescript
* import { of } from 'rxjs';
* import { switchMap } from 'rxjs/operators';
*
* const switched = of(1, 2, 3).pipe(switchMap((x: number) => of(x, x ** 2, x ** 3)));
* switched.subscribe(x => console.log(x));
* // outputs
* // 1
* // 1
* // 1
* // 2
* // 4
* // 8
* // ... and so on
* ```
*
* Rerun an interval Observable on every click event
* ```ts
* import { fromEvent, interval } from 'rxjs';
* import { switchMap } from 'rxjs/operators';
*
* const clicks = fromEvent(document, 'click');
* const result = clicks.pipe(switchMap((ev) => interval(1000)));
* result.subscribe(x => console.log(x));
* ```
*
* @see {@link concatMap}
* @see {@link exhaustMap}
* @see {@link mergeMap}
* @see {@link switchAll}
* @see {@link switchMapTo}
*
* @param {function(value: T, ?index: number): ObservableInput} project A function
* that, when applied to an item emitted by the source Observable, returns an
* Observable.
* @return {Observable} An Observable that emits the result of applying the
* projection function (and the optional deprecated `resultSelector`) to each item
* emitted by the source Observable and taking only the values from the most recently
* projected inner Observable.
* @method switchMap
* @owner Observable
*/
export function switchMap<T, R, O extends ObservableInput<any>>(
project: (value: T, index: number) => O,
resultSelector?: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R,
): OperatorFunction<T, ObservedValueOf<O>|R> {
if (typeof resultSelector === 'function') {
return (source: Observable<T>) => source.pipe(
switchMap((a, i) => from(project(a, i)).pipe(
map((b, ii) => resultSelector(a, b, i, ii))
))
);
}
return (source: Observable<T>) => source.lift(new SwitchMapOperator(project));
}
class SwitchMapOperator<T, R> implements Operator<T, R> {
constructor(private project: (value: T, index: number) => ObservableInput<R>) {
}
call(subscriber: Subscriber<R>, source: any): any {
return source.subscribe(new SwitchMapSubscriber(subscriber, this.project));
}
}
/**
* We need this JSDoc comment for affecting ESDoc.
* @ignore
* @extends {Ignored}
*/
class SwitchMapSubscriber<T, R> extends OuterSubscriber<T, R> {
private index: number = 0;
private innerSubscription: Subscription;
constructor(destination: Subscriber<R>,
private project: (value: T, index: number) => ObservableInput<R>) {
super(destination);
}
protected _next(value: T) {
let result: ObservableInput<R>;
const index = this.index++;
try {
result = this.project(value, index);
} catch (error) {
this.destination.error(error);
return;
}
this._innerSub(result, value, index);
}
private _innerSub(result: ObservableInput<R>, value: T, index: number) {
const innerSubscription = this.innerSubscription;
if (innerSubscription) {
innerSubscription.unsubscribe();
}
const innerSubscriber = new InnerSubscriber(this, undefined, undefined);
const destination = this.destination as Subscription;
destination.add(innerSubscriber);
this.innerSubscription = subscribeToResult(this, result, value, index, innerSubscriber);
}
protected _complete(): void {
const {innerSubscription} = this;
if (!innerSubscription || innerSubscription.closed) {
super._complete();
}
this.unsubscribe();
}
protected _unsubscribe() {
this.innerSubscription = null;
}
notifyComplete(innerSub: Subscription): void {
const destination = this.destination as Subscription;
destination.remove(innerSub);
this.innerSubscription = null;
if (this.isStopped) {
super._complete();
}
}
notifyNext(outerValue: T, innerValue: R,
outerIndex: number, innerIndex: number,
innerSub: InnerSubscriber<T, R>): void {
this.destination.next(innerValue);
}
}
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