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node_modules/rxjs/_esm2015/operators/expand.js

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+import { tryCatch } from '../util/tryCatch';
+import { errorObject } from '../util/errorObject';
+import { OuterSubscriber } from '../OuterSubscriber';
+import { subscribeToResult } from '../util/subscribeToResult';
+/* 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>
+ *
+ * <img src="./img/expand.png" width="100%">
+ *
+ * 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 <caption>Start emitting the powers of two on every click, at most 10 of them</caption>
+ * var clicks = Rx.Observable.fromEvent(document, 'click');
+ * var powersOfTwo = clicks
+ *   .mapTo(1)
+ *   .expand(x => Rx.Observable.of(2 * x).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 {Scheduler} [scheduler=null] The IScheduler 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(project, concurrent = Number.POSITIVE_INFINITY, scheduler = undefined) {
+    concurrent = (concurrent || 0) < 1 ? Number.POSITIVE_INFINITY : concurrent;
+    return (source) => source.lift(new ExpandOperator(project, concurrent, scheduler));
+}
+export class ExpandOperator {
+    constructor(project, concurrent, scheduler) {
+        this.project = project;
+        this.concurrent = concurrent;
+        this.scheduler = scheduler;
+    }
+    call(subscriber, source) {
+        return source.subscribe(new ExpandSubscriber(subscriber, this.project, this.concurrent, this.scheduler));
+    }
+}
+/**
+ * We need this JSDoc comment for affecting ESDoc.
+ * @ignore
+ * @extends {Ignored}
+ */
+export class ExpandSubscriber extends OuterSubscriber {
+    constructor(destination, project, concurrent, scheduler) {
+        super(destination);
+        this.project = project;
+        this.concurrent = concurrent;
+        this.scheduler = scheduler;
+        this.index = 0;
+        this.active = 0;
+        this.hasCompleted = false;
+        if (concurrent < Number.POSITIVE_INFINITY) {
+            this.buffer = [];
+        }
+    }
+    static dispatch(arg) {
+        const { subscriber, result, value, index } = arg;
+        subscriber.subscribeToProjection(result, value, index);
+    }
+    _next(value) {
+        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 = { subscriber: this, result, value, index };
+                this.add(this.scheduler.schedule(ExpandSubscriber.dispatch, 0, state));
+            }
+        }
+        else {
+            this.buffer.push(value);
+        }
+    }
+    subscribeToProjection(result, value, index) {
+        this.active++;
+        this.add(subscribeToResult(this, result, value, index));
+    }
+    _complete() {
+        this.hasCompleted = true;
+        if (this.hasCompleted && this.active === 0) {
+            this.destination.complete();
+        }
+    }
+    notifyNext(outerValue, innerValue, outerIndex, innerIndex, innerSub) {
+        this._next(innerValue);
+    }
+    notifyComplete(innerSub) {
+        const buffer = this.buffer;
+        this.remove(innerSub);
+        this.active--;
+        if (buffer && buffer.length > 0) {
+            this._next(buffer.shift());
+        }
+        if (this.hasCompleted && this.active === 0) {
+            this.destination.complete();
+        }
+    }
+}
+//# sourceMappingURL=expand.js.map