Added bootstrap with ng-bootstrap

src/app/app.component.ts

@@ -1,11 +1,59 @@
-import { Component, ChangeDetectionStrategy, ViewEncapsulation } from '@angular/core';
+import { Component, HostListener, Input, ChangeDetectionStrategy, ViewEncapsulation, OnDestroy, OnInit } from '@angular/core';
+
+import { Event, NavigationEnd, Router } from '@angular/router';
 
 @Component({
   changeDetection: ChangeDetectionStrategy.Default,
   encapsulation: ViewEncapsulation.Emulated,
   selector: 'ds-app',
   templateUrl: './app.component.html',
-  styleUrls: [ './app.component.scss' ]
+  styleUrls: ['./app.component.scss']
 })
-export class AppComponent {
+export class AppComponent implements OnDestroy, OnInit {
+
+  // TODO: move header and all related properties into its own component
+
+  private navCollapsed: boolean;
+
+  private routerSubscription: any;
+
+  constructor(private router: Router) {
+    this.collapse();
+  }
+
+  @HostListener('window:resize', ['$event'])
+  private onResize(event): void {
+    this.collapse();
+  }
+
+  ngOnInit() {
+    this.routerSubscription = this.router.events.subscribe((event: Event) => {
+      if (event instanceof NavigationEnd) {
+        this.collapse();
+      }
+    });
+  }
+
+  ngOnDestroy() {
+    if (this.routerSubscription) {
+      this.routerSubscription.unsubscribe();
+    }
+  }
+
+  private collapse(): void {
+    this.navCollapsed = true;
+  }
+
+  private expand(): void {
+    this.navCollapsed = false;
+  }
+
+  public toggle(): void {
+    this.navCollapsed ? this.expand() : this.collapse();
+  }
+
+  public isNavBarCollaped(): boolean {
+    return this.navCollapsed;
+  }
+
 }