es6/operators/mergeScan.js

import { tryCatch } from '../util/tryCatch';
import { errorObject } from '../util/errorObject';
import { subscribeToResult } from '../util/subscribeToResult';
import { OuterSubscriber } from '../OuterSubscriber';
/**
 * Applies an accumulator function over the source Observable where the
 * accumulator function itself returns an Observable, then each intermediate
 * Observable returned is merged into the output Observable.
 *
 * <span class="informal">It's like {@link scan}, but the Observables returned
 * by the accumulator are merged into the outer Observable.</span>
 *
 * @example <caption>Count the number of click events</caption>
 * const click$ = Rx.Observable.fromEvent(document, 'click');
 * const one$ = click$.mapTo(1);
 * const seed = 0;
 * const count$ = one$.mergeScan((acc, one) => Rx.Observable.of(acc + one), seed);
 * count$.subscribe(x => console.log(x));
 *
 * // Results:
 * 1
 * 2
 * 3
 * 4
 * // ...and so on for each click
 *
 * @param {function(acc: R, value: T): Observable<R>} accumulator
 * The accumulator function called on each source value.
 * @param seed The initial accumulation value.
 * @param {number} [concurrent=Number.POSITIVE_INFINITY] Maximum number of
 * input Observables being subscribed to concurrently.
 * @return {Observable<R>} An observable of the accumulated values.
 * @method mergeScan
 * @owner Observable
 */
export function mergeScan(accumulator, seed, concurrent = Number.POSITIVE_INFINITY) {
    return (source) => source.lift(new MergeScanOperator(accumulator, seed, concurrent));
}
export class MergeScanOperator {
    constructor(accumulator, seed, concurrent) {
        this.accumulator = accumulator;
        this.seed = seed;
        this.concurrent = concurrent;
    }
    call(subscriber, source) {
        return source.subscribe(new MergeScanSubscriber(subscriber, this.accumulator, this.seed, this.concurrent));
    }
}
/**
 * We need this JSDoc comment for affecting ESDoc.
 * @ignore
 * @extends {Ignored}
 */
export class MergeScanSubscriber extends OuterSubscriber {
    constructor(destination, accumulator, acc, concurrent) {
        super(destination);
        this.accumulator = accumulator;
        this.acc = acc;
        this.concurrent = concurrent;
        this.hasValue = false;
        this.hasCompleted = false;
        this.buffer = [];
        this.active = 0;
        this.index = 0;
    }
    _next(value) {
        if (this.active < this.concurrent) {
            const index = this.index++;
            const ish = tryCatch(this.accumulator)(this.acc, value);
            const destination = this.destination;
            if (ish === errorObject) {
                destination.error(errorObject.e);
            }
            else {
                this.active++;
                this._innerSub(ish, value, index);
            }
        }
        else {
            this.buffer.push(value);
        }
    }
    _innerSub(ish, value, index) {
        this.add(subscribeToResult(this, ish, value, index));
    }
    _complete() {
        this.hasCompleted = true;
        if (this.active === 0 && this.buffer.length === 0) {
            if (this.hasValue === false) {
                this.destination.next(this.acc);
            }
            this.destination.complete();
        }
    }
    notifyNext(outerValue, innerValue, outerIndex, innerIndex, innerSub) {
        const { destination } = this;
        this.acc = innerValue;
        this.hasValue = true;
        destination.next(innerValue);
    }
    notifyComplete(innerSub) {
        const buffer = this.buffer;
        this.remove(innerSub);
        this.active--;
        if (buffer.length > 0) {
            this._next(buffer.shift());
        }
        else if (this.active === 0 && this.hasCompleted) {
            if (this.hasValue === false) {
                this.destination.next(this.acc);
            }
            this.destination.complete();
        }
    }
}
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