save and restore scroll position of song list

src/app/app.component.ts

@@ -1,5 +1,7 @@
-import {Component, OnInit} from '@angular/core';
+import {Component, OnInit, ViewChild} from '@angular/core';
 import {fader} from './animations';
+import {ScrollService} from './services/scroll.service';
+import {PerfectScrollbarComponent} from 'ngx-perfect-scrollbar';
 
 @Component({
   selector: 'app-root',
@@ -9,9 +11,24 @@ import {fader} from './animations';
 })
 export class AppComponent implements OnInit {
   public static hideLoader = () => document.querySelector('#load-bg').classList.add('hidden');
+  @ViewChild('scrollbar', {static: false}) scrollbar: PerfectScrollbarComponent;
+
+  constructor(private scrollService: ScrollService) {
+    scrollService.restoreScrollPosition$.subscribe(pos => {
+      if (this.scrollbar && pos) {
+        //this.scrollbar.scrollTo(pos, 0);
+        this.scrollbar.directiveRef.scrollTo(0, pos, 300)
+        // debugger;
+      }
+    })
+  }
 
   public ngOnInit(): void {
     setTimeout(() => AppComponent.hideLoader(), 800);
 
   }
+
+  onScoll($event: { srcElement: { scrollTop: number } }) {
+    this.scrollService.saveScrollPosition($event.srcElement.scrollTop);
+  }
 }