initial commit: scaffolding

1 files changed, 132 insertions, 0 deletions

diff --git a/node_modules/rxjs/src/internal/operators/switchMap.ts b/node_modules/rxjs/src/internal/operators/switchMap.ts
new file mode 100644
index 0000000..0ded7ba
--- /dev/null
+++ b/node_modules/rxjs/src/internal/operators/switchMap.ts
@@ -0,0 +1,132 @@
+import { Subscriber } from '../Subscriber';
+import { ObservableInput, OperatorFunction, ObservedValueOf } from '../types';
+import { innerFrom } from '../observable/innerFrom';
+import { operate } from '../util/lift';
+import { createOperatorSubscriber } from './OperatorSubscriber';
+
+/* tslint:disable:max-line-length */
+export function switchMap<T, O extends ObservableInput<any>>(
+  project: (value: T, index: number) => O
+): OperatorFunction<T, ObservedValueOf<O>>;
+/** @deprecated The `resultSelector` parameter will be removed in v8. Use an inner `map` instead. Details: https://rxjs.dev/deprecations/resultSelector */
+export function switchMap<T, O extends ObservableInput<any>>(
+  project: (value: T, index: number) => O,
+  resultSelector: undefined
+): OperatorFunction<T, ObservedValueOf<O>>;
+/** @deprecated The `resultSelector` parameter will be removed in v8. Use an inner `map` instead. Details: https://rxjs.dev/deprecations/resultSelector */
+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 using {@link switchAll}.</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
+ *
+ * ```ts
+ * import { of, switchMap } from 'rxjs';
+ *
+ * const switched = of(1, 2, 3).pipe(switchMap(x => of(x, x ** 2, x ** 3)));
+ * switched.subscribe(x => console.log(x));
+ * // outputs
+ * // 1
+ * // 1
+ * // 1
+ * // 2
+ * // 4
+ * // 8
+ * // 3
+ * // 9
+ * // 27
+ * ```
+ *
+ * Restart an interval Observable on every click event
+ *
+ * ```ts
+ * import { fromEvent, switchMap, interval } from 'rxjs';
+ *
+ * const clicks = fromEvent(document, 'click');
+ * const result = clicks.pipe(switchMap(() => interval(1000)));
+ * result.subscribe(x => console.log(x));
+ * ```
+ *
+ * @see {@link concatMap}
+ * @see {@link exhaustMap}
+ * @see {@link mergeMap}
+ * @see {@link switchAll}
+ * @see {@link switchMapTo}
+ *
+ * @param project A function that, when applied to an item emitted by the source
+ * Observable, returns an Observable.
+ * @return A function that returns 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.
+ */
+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> {
+  return operate((source, subscriber) => {
+    let innerSubscriber: Subscriber<ObservedValueOf<O>> | null = null;
+    let index = 0;
+    // Whether or not the source subscription has completed
+    let isComplete = false;
+
+    // We only complete the result if the source is complete AND we don't have an active inner subscription.
+    // This is called both when the source completes and when the inners complete.
+    const checkComplete = () => isComplete && !innerSubscriber && subscriber.complete();
+
+    source.subscribe(
+      createOperatorSubscriber(
+        subscriber,
+        (value) => {
+          // Cancel the previous inner subscription if there was one
+          innerSubscriber?.unsubscribe();
+          let innerIndex = 0;
+          const outerIndex = index++;
+          // Start the next inner subscription
+          innerFrom(project(value, outerIndex)).subscribe(
+            (innerSubscriber = createOperatorSubscriber(
+              subscriber,
+              // When we get a new inner value, next it through. Note that this is
+              // handling the deprecate result selector here. This is because with this architecture
+              // it ends up being smaller than using the map operator.
+              (innerValue) => subscriber.next(resultSelector ? resultSelector(value, innerValue, outerIndex, innerIndex++) : innerValue),
+              () => {
+                // The inner has completed. Null out the inner subscriber to
+                // free up memory and to signal that we have no inner subscription
+                // currently.
+                innerSubscriber = null!;
+                checkComplete();
+              }
+            ))
+          );
+        },
+        () => {
+          isComplete = true;
+          checkComplete();
+        }
+      )
+    );
+  });
+}