[Library | Trunk]: Create smooth scroll service

git-svn-id: https://svn.driver.research-infrastructures.eu/driver/dnet40/modules/uoa-services-library/trunk/ng-openaire-library/src/app@60844 d315682c-612b-4755-9ff5-7f18f6832af3

utils/smooth-scroll.ts

@@ -0,0 +1,73 @@
+import {NavigationEnd, Router} from "@angular/router";
+import {Injectable} from "@angular/core";
+import {Subscription} from "rxjs";
+
+@Injectable({
+  providedIn: "root"
+})
+export class SmoothScroll {
+  private interval;
+  private readonly sub;
+  private lastRoute;
+  
+  constructor(private router: Router) {
+    this.sub = router.events.subscribe(event => {
+      if (event instanceof NavigationEnd) {
+        if(this.interval) {
+          clearInterval(this.interval);
+        }
+        const fragment = router.parseUrl(router.url).fragment;
+        if (fragment) {
+          let i = 0;
+          this.interval = setInterval(() => {
+            i++;
+            const element = document.getElementById(fragment);
+            if (element) {
+              if(this.interval) {
+                clearInterval(this.interval);
+              }
+              const yOffset = -100;
+              let position = 0;
+              let interval = setInterval(() => {
+                if(position !== element.getBoundingClientRect().top) {
+                  position = element.getBoundingClientRect().top;
+                } else {
+                  clearInterval(interval);
+                  const y = element.getBoundingClientRect().top + window.pageYOffset + yOffset;
+                  window.scrollTo({top: y, behavior: 'smooth'});
+                }
+              }, 50);
+            }
+            if(i > 4 && this.interval) {
+              clearInterval(this.interval);
+            }
+          }, 100);
+        } else {
+          if(this.lastRoute !== this.getUrl(event.url)) {
+            window.scrollTo({top: 0});
+          } else {
+            window.scrollTo({top: 0, behavior: "smooth"});
+          }
+        }
+        this.lastRoute = this.getUrl(event.url);
+      }
+    });
+  }
+  
+  private getUrl(url: string) {
+    return url.split('?')[0].split('#')[0];
+  }
+  
+  public clearSubscriptions() {
+    if(this.sub && this.sub instanceof Subscription) {
+      this.sub.unsubscribe();
+    }
+    if(this.interval) {
+      clearInterval(this.interval);
+    }
+  }
+  
+  ngOnDestroy() {
+    this.clearSubscriptions();
+  }
+}