refractor: shell (#287)

* Refractor components.
* Shift theme picker component to shared module.
* Shift progress bar service into its own folder.
* Add footer to app shell.
* Replace mat-icon by font-awesome icons.
* Fix sidenav visibility bug for handsets.
* Add comments.

Closes #286, Fixes #285

src/app/core/progress-bar/progress-bar.service.spec.ts

@@ -0,0 +1,15 @@
+import { TestBed, inject } from '@angular/core/testing';
+
+import { ProgressBarService } from './progress-bar.service';
+
+describe('ProgressBarService', () => {
+  beforeEach(() => {
+    TestBed.configureTestingModule({
+      providers: [ProgressBarService]
+    });
+  });
+
+  it('should be created', inject([ProgressBarService], (service: ProgressBarService) => {
+    expect(service).toBeTruthy();
+  }));
+});

src/app/core/progress-bar/progress-bar.service.ts

@@ -0,0 +1,35 @@
+import { Injectable, EventEmitter } from '@angular/core';
+
+@Injectable({
+  providedIn: 'root'
+})
+export class ProgressBarService {
+
+  public updateProgressBar: EventEmitter<any>;
+  private requestsRunning = 0;
+
+  constructor() {
+    this.updateProgressBar = new EventEmitter();
+  }
+
+  public getRequestsRunning(): number {
+    return this.requestsRunning;
+  }
+
+  public increase(): void {
+    this.requestsRunning++;
+    if (this.requestsRunning === 1) {
+      this.updateProgressBar.emit('indeterminate');
+    }
+  }
+
+  public decrease(): void {
+    if (this.requestsRunning > 0) {
+      this.requestsRunning--;
+      if (this.requestsRunning === 0) {
+        this.updateProgressBar.emit('none');
+      }
+    }
+  }
+
+}

src/app/core/progress-bar/progress.interceptor.ts

@@ -0,0 +1,32 @@
+import { Injectable } from '@angular/core';
+import {HttpEvent, HttpHandler, HttpInterceptor, HttpRequest, HttpResponse} from '@angular/common/http';
+
+import { Observable } from 'rxjs';
+import { tap, catchError } from 'rxjs/operators';
+
+import { ProgressBarService } from './progress-bar.service';
+
+@Injectable()
+export class ProgressInterceptor implements HttpInterceptor {
+
+  constructor(private progressBarService: ProgressBarService) { }
+
+  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
+    this.progressBarService.increase();
+    return next.handle(request)
+      .pipe(
+        tap(event => {
+          if (event instanceof HttpResponse) {
+            this.progressBarService.decrease();
+          }
+        })
+      )
+      .pipe(
+        catchError(error => {
+          this.progressBarService.decrease();
+          throw error;
+        })
+      );
+  }
+
+}