Implement base class for future config services

src/app/services/config.service.base.ts

@@ -0,0 +1,53 @@
+import { Injectable } from '@angular/core';
+import { WebSocketService } from './websocket.service';
+import { Subject, BehaviorSubject, forkJoin } from 'rxjs';
+import { take } from 'rxjs/operators';
+
+@Injectable()
+export abstract class ConfigServiceBase {
+  initDone = false;
+  keys = new Array<string>();
+  mandatoryConfigs = new Array<any>();
+  configDone = new Subject<void>();
+
+  constructor(private webSocketService: WebSocketService) {}
+
+  init() {
+    if (this.initDone) {
+      return;
+    }
+    this.waitForMandatoryConfigs();
+    this.subscribeConfigKeys();
+    this.initDone = true;
+  }
+
+  waitForMandatoryConfigs() {
+    const firstConfigs = new Array<any>();
+    this.mandatoryConfigs.forEach((config) => {
+      const requiredEmitCount = config instanceof BehaviorSubject ? 2 : 1;
+      firstConfigs.push(config.pipe(take(requiredEmitCount)));
+    });
+
+    forkJoin(firstConfigs).subscribe(undefined, undefined, () => {
+      this.configDone.next();
+      this.configDone.complete();
+    });
+  }
+
+  subscribeConfigKeys() {
+    this.webSocketService.connect();
+    this.keys.forEach(key =>
+        this.webSocketService.observeKey<any>(key).subscribe(this.handleConfig.bind(this))
+    );
+  }
+
+  handleConfig(message: any) {
+    Object.keys(message).filter(key => key !== 'key').forEach(key => {
+      if (this[key] === undefined) {
+        console.log(`Invalid ${this.keys} config key "${key}"!`);
+      } else {
+        this[key].next(message[key]);
+      }
+    });
+  }
+}