Extract status code polling logic into a class

src/app/dashboard/statuscodepoller.ts

@@ -0,0 +1,63 @@
+import { HttpClient } from '@angular/common/http';
+import { Subject, Subscription, BehaviorSubject } from 'rxjs';
+import { retryWhen, delay, tap, skip } from 'rxjs/operators';
+
+export class StatusCodePoller {
+  http: HttpClient;
+  url: BehaviorSubject<string>;
+  pollFreq: number;
+  okCode: number;
+  stopOnOk: boolean;
+
+  pollSubscription: Subscription;
+  urlSubscription: Subscription;
+  poll = new Subject<any>();
+  ok = new Subject<any>();
+  isPolling = new BehaviorSubject<boolean>(false);
+
+  constructor(
+      url: BehaviorSubject<string>, http: HttpClient,
+      pollFreq = 1000, okCode = 200,
+      stopOnOk = true
+    ) {
+    this.url = url;
+    this.http = http;
+    this.pollFreq = pollFreq;
+    this.okCode = okCode;
+    this.stopOnOk = stopOnOk;
+  }
+
+  start() {
+    this.stop();
+    if (this.url.value === '') {
+      return;
+    }
+    this.urlSubscription = this.url.pipe(skip(1)).subscribe(() => this.stop());
+    this.isPolling.next(true);
+    this.pollSubscription = this.http.get(this.url.value, {observe: 'response'}).pipe(
+      retryWhen(errors =>
+        errors.pipe(
+          tap(
+            response => {
+              this.poll.next(response);
+              if (response.status === this.okCode) {
+                if (this.stopOnOk) {
+                  this.stop();
+                }
+                this.ok.next(response);
+              }
+          }),
+          delay(this.pollFreq)
+    ))).subscribe();
+  }
+
+  stop() {
+    this.isPolling.next(false);
+    if (this.pollSubscription) {
+      this.pollSubscription.unsubscribe();
+    }
+    if (this.urlSubscription) {
+      this.urlSubscription.unsubscribe();
+    }
+  }
+}