import { Operator } from '../Operator';
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import { Observable } from '../Observable';
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import { Subscriber } from '../Subscriber';
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import { Subscription } from '../Subscription';
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import { ObservableInput, OperatorFunction } from '../types';
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import { SimpleOuterSubscriber, SimpleInnerSubscriber, innerSubscribe } from '../innerSubscribe';
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/**
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* Applies an accumulator function over the source Observable where the
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* accumulator function itself returns an Observable, then each intermediate
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* Observable returned is merged into the output Observable.
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*
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* <span class="informal">It's like {@link scan}, but the Observables returned
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* by the accumulator are merged into the outer Observable.</span>
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*
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* ## Example
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* Count the number of click events
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* ```ts
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* import { fromEvent, of } from 'rxjs';
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* import { mapTo, mergeScan } from 'rxjs/operators';
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*
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* const click$ = fromEvent(document, 'click');
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* const one$ = click$.pipe(mapTo(1));
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* const seed = 0;
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* const count$ = one$.pipe(
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* mergeScan((acc, one) => of(acc + one), seed),
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* );
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* count$.subscribe(x => console.log(x));
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*
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* // Results:
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* // 1
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* // 2
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* // 3
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* // 4
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* // ...and so on for each click
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* ```
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*
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* @param {function(acc: R, value: T): Observable<R>} accumulator
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* The accumulator function called on each source value.
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* @param seed The initial accumulation value.
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* @param {number} [concurrent=Number.POSITIVE_INFINITY] Maximum number of
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* input Observables being subscribed to concurrently.
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* @return {Observable<R>} An observable of the accumulated values.
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* @method mergeScan
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* @owner Observable
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*/
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export function mergeScan<T, R>(accumulator: (acc: R, value: T, index: number) => ObservableInput<R>,
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seed: R,
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concurrent: number = Number.POSITIVE_INFINITY): OperatorFunction<T, R> {
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return (source: Observable<T>) => source.lift(new MergeScanOperator(accumulator, seed, concurrent));
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}
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export class MergeScanOperator<T, R> implements Operator<T, R> {
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constructor(private accumulator: (acc: R, value: T, index: number) => ObservableInput<R>,
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private seed: R,
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private concurrent: number) {
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}
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call(subscriber: Subscriber<R>, source: any): any {
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return source.subscribe(new MergeScanSubscriber(
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subscriber, this.accumulator, this.seed, this.concurrent
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));
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}
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}
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/**
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* We need this JSDoc comment for affecting ESDoc.
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* @ignore
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* @extends {Ignored}
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*/
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export class MergeScanSubscriber<T, R> extends SimpleOuterSubscriber<T, R> {
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private hasValue: boolean = false;
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private hasCompleted: boolean = false;
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private buffer: Observable<any>[] = [];
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private active: number = 0;
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protected index: number = 0;
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constructor(destination: Subscriber<R>,
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private accumulator: (acc: R, value: T, index: number) => ObservableInput<R>,
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private acc: R,
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private concurrent: number) {
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super(destination);
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}
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protected _next(value: any): void {
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if (this.active < this.concurrent) {
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const index = this.index++;
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const destination = this.destination;
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let ish;
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try {
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const { accumulator } = this;
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ish = accumulator(this.acc, value, index);
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} catch (e) {
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return destination.error!(e);
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}
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this.active++;
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this._innerSub(ish);
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} else {
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this.buffer.push(value);
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}
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}
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private _innerSub(ish: any): void {
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const innerSubscriber = new SimpleInnerSubscriber(this);
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const destination = this.destination as Subscription;
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destination.add(innerSubscriber);
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const innerSubscription = innerSubscribe(ish, innerSubscriber);
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// The returned subscription will usually be the subscriber that was
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// passed. However, interop subscribers will be wrapped and for
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// unsubscriptions to chain correctly, the wrapper needs to be added, too.
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if (innerSubscription !== innerSubscriber) {
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destination.add(innerSubscription);
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}
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}
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protected _complete(): void {
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this.hasCompleted = true;
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if (this.active === 0 && this.buffer.length === 0) {
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if (this.hasValue === false) {
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this.destination.next!(this.acc);
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}
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this.destination.complete!();
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}
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this.unsubscribe();
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}
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notifyNext(innerValue: R): void {
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const { destination } = this;
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this.acc = innerValue;
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this.hasValue = true;
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destination.next!(innerValue);
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}
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notifyComplete(): void {
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const buffer = this.buffer;
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this.active--;
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if (buffer.length > 0) {
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this._next(buffer.shift());
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} else if (this.active === 0 && this.hasCompleted) {
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if (this.hasValue === false) {
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this.destination.next!(this.acc);
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}
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this.destination.complete!();
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}
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}
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}
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