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import { Observable } from '../Observable';
import { Operator } from '../Operator';
import { Subscriber } from '../Subscriber';
import { Subscription } from '../Subscription';
import { subscribeToResult } from '../util/subscribeToResult';
import { OuterSubscriber } from '../OuterSubscriber';
import { InnerSubscriber } from '../InnerSubscriber';
import { ObservableInput, OperatorFunction } from '../types';
import { map } from './map';
import { from } from '../observable/from';
/* tslint:disable:max-line-length */
export function mergeMap<T, R>(project: (value: T, index: number) => ObservableInput<R>, concurrent?: number): OperatorFunction<T, R>;
/** @deprecated resultSelector no longer supported, use inner map instead */
export function mergeMap<T, R>(project: (value: T, index: number) => ObservableInput<R>, resultSelector: undefined, concurrent?: number): OperatorFunction<T, R>;
/** @deprecated resultSelector no longer supported, use inner map instead */
export function mergeMap<T, I, R>(project: (value: T, index: number) => ObservableInput<I>, resultSelector: (outerValue: T, innerValue: I, outerIndex: number, innerIndex: number) => R, concurrent?: number): OperatorFunction<T, R>;
/* tslint:enable:max-line-length */
/**
* Projects each source value to an Observable which is merged in the output
* Observable.
*
* <span class="informal">Maps each value to an Observable, then flattens all of
* these inner Observables using {@link mergeAll}.</span>
*
* ![](mergeMap.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 Observable, and then merging those resulting Observables and
* emitting the results of this merger.
*
* ## Example
* Map and flatten each letter to an Observable ticking every 1 second
* ```javascript
* const letters = of('a', 'b', 'c');
* const result = letters.pipe(
* mergeMap(x => interval(1000).pipe(map(i => x+i))),
* );
* result.subscribe(x => console.log(x));
*
* // Results in the following:
* // a0
* // b0
* // c0
* // a1
* // b1
* // c1
* // continues to list a,b,c with respective ascending integers
* ```
*
* @see {@link concatMap}
* @see {@link exhaustMap}
* @see {@link merge}
* @see {@link mergeAll}
* @see {@link mergeMapTo}
* @see {@link mergeScan}
* @see {@link switchMap}
*
* @param {function(value: T, ?index: number): ObservableInput} project A function
* that, when applied to an item emitted by the source Observable, returns an
* Observable.
* @param {number} [concurrent=Number.POSITIVE_INFINITY] Maximum number of input
* Observables being subscribed to concurrently.
* @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 merging the results of the Observables
* obtained from this transformation.
* @method mergeMap
* @owner Observable
*/
export function mergeMap<T, I, R>(
project: (value: T, index: number) => ObservableInput<I>,
resultSelector?: ((outerValue: T, innerValue: I, outerIndex: number, innerIndex: number) => R) | number,
concurrent: number = Number.POSITIVE_INFINITY
): OperatorFunction<T, I|R> {
if (typeof resultSelector === 'function') {
// DEPRECATED PATH
return (source: Observable<T>) => source.pipe(
mergeMap((a, i) => from(project(a, i)).pipe(
map((b, ii) => resultSelector(a, b, i, ii)),
), concurrent)
);
} else if (typeof resultSelector === 'number') {
concurrent = resultSelector;
}
return (source: Observable<T>) => source.lift(new MergeMapOperator(project, concurrent));
}
export class MergeMapOperator<T, R> implements Operator<T, R> {
constructor(private project: (value: T, index: number) => ObservableInput<R>,
private concurrent: number = Number.POSITIVE_INFINITY) {
}
call(observer: Subscriber<R>, source: any): any {
return source.subscribe(new MergeMapSubscriber(
observer, this.project, this.concurrent
));
}
}
/**
* We need this JSDoc comment for affecting ESDoc.
* @ignore
* @extends {Ignored}
*/
export class MergeMapSubscriber<T, R> extends OuterSubscriber<T, R> {
private hasCompleted: boolean = false;
private buffer: T[] = [];
private active: number = 0;
protected index: number = 0;
constructor(destination: Subscriber<R>,
private project: (value: T, index: number) => ObservableInput<R>,
private concurrent: number = Number.POSITIVE_INFINITY) {
super(destination);
}
protected _next(value: T): void {
if (this.active < this.concurrent) {
this._tryNext(value);
} else {
this.buffer.push(value);
}
}
protected _tryNext(value: T) {
let result: ObservableInput<R>;
const index = this.index++;
try {
result = this.project(value, index);
} catch (err) {
this.destination.error(err);
return;
}
this.active++;
this._innerSub(result, value, index);
}
private _innerSub(ish: ObservableInput<R>, value: T, index: number): void {
const innerSubscriber = new InnerSubscriber(this, undefined, undefined);
const destination = this.destination as Subscription;
destination.add(innerSubscriber);
subscribeToResult<T, R>(this, ish, value, index, innerSubscriber);
}
protected _complete(): void {
this.hasCompleted = true;
if (this.active === 0 && this.buffer.length === 0) {
this.destination.complete();
}
this.unsubscribe();
}
notifyNext(outerValue: T, innerValue: R,
outerIndex: number, innerIndex: number,
innerSub: InnerSubscriber<T, R>): void {
this.destination.next(innerValue);
}
notifyComplete(innerSub: Subscription): void {
const buffer = this.buffer;
this.remove(innerSub);
this.active--;
if (buffer.length > 0) {
this._next(buffer.shift());
} else if (this.active === 0 && this.hasCompleted) {
this.destination.complete();
}
}
}