Reorganize client shared modules

[oweals/peertube.git] / client / src / app / shared / shared-main / angular / infinite-scroller.directive.ts

diff --git a/client/src/app/shared/shared-main/angular/infinite-scroller.directive.ts b/client/src/app/shared/shared-main/angular/infinite-scroller.directive.ts
new file mode 100644 (file)
index 0000000..f09c3d1
--- /dev/null
+++ b/client/src/app/shared/shared-main/angular/infinite-scroller.directive.ts
@@ -0,0 +1,96 @@
+import { distinctUntilChanged, filter, map, share, startWith, throttleTime } from 'rxjs/operators'
+import { AfterContentChecked, Directive, ElementRef, EventEmitter, Input, OnDestroy, OnInit, Output } from '@angular/core'
+import { fromEvent, Observable, Subscription } from 'rxjs'
+
+@Directive({
+  selector: '[myInfiniteScroller]'
+})
+export class InfiniteScrollerDirective implements OnInit, OnDestroy, AfterContentChecked {
+  @Input() percentLimit = 70
+  @Input() autoInit = false
+  @Input() onItself = false
+  @Input() dataObservable: Observable<any[]>
+
+  @Output() nearOfBottom = new EventEmitter<void>()
+
+  private decimalLimit = 0
+  private lastCurrentBottom = -1
+  private scrollDownSub: Subscription
+  private container: HTMLElement
+
+  private checkScroll = false
+
+  constructor (private el: ElementRef) {
+    this.decimalLimit = this.percentLimit / 100
+  }
+
+  ngAfterContentChecked () {
+    if (this.checkScroll) {
+      this.checkScroll = false
+
+      console.log('Checking if the initial state has a scroll.')
+
+      if (this.hasScroll() === false) this.nearOfBottom.emit()
+    }
+  }
+
+  ngOnInit () {
+    if (this.autoInit === true) return this.initialize()
+  }
+
+  ngOnDestroy () {
+    if (this.scrollDownSub) this.scrollDownSub.unsubscribe()
+  }
+
+  initialize () {
+    this.container = this.onItself
+      ? this.el.nativeElement
+      : document.documentElement
+
+    // Emit the last value
+    const throttleOptions = { leading: true, trailing: true }
+
+    const scrollableElement = this.onItself ? this.container : window
+    const scrollObservable = fromEvent(scrollableElement, 'scroll')
+      .pipe(
+        startWith(true),
+        throttleTime(200, undefined, throttleOptions),
+        map(() => this.getScrollInfo()),
+        distinctUntilChanged((o1, o2) => o1.current === o2.current),
+        share()
+      )
+
+    // Scroll Down
+    this.scrollDownSub = scrollObservable
+      .pipe(
+        filter(({ current }) => this.isScrollingDown(current)),
+        filter(({ current, maximumScroll }) => (current / maximumScroll) > this.decimalLimit)
+      )
+      .subscribe(() => this.nearOfBottom.emit())
+
+    if (this.dataObservable) {
+      this.dataObservable
+          .pipe(filter(d => d.length !== 0))
+          .subscribe(() => this.checkScroll = true)
+    }
+  }
+
+  private getScrollInfo () {
+    return { current: this.container.scrollTop, maximumScroll: this.getMaximumScroll() }
+  }
+
+  private getMaximumScroll () {
+    return this.container.scrollHeight - window.innerHeight
+  }
+
+  private hasScroll () {
+    return this.getMaximumScroll() > 0
+  }
+
+  private isScrollingDown (current: number) {
+    const result = this.lastCurrentBottom < current
+
+    this.lastCurrentBottom = current
+    return result
+  }
+}