client/src/app/shared/shared-main/angular/infinite-scroller.directive.ts

   1 import { fromEvent, Observable, Subscription } from 'rxjs'
   2 import { distinctUntilChanged, filter, map, share, startWith, throttleTime } from 'rxjs/operators'
   3 import { AfterViewChecked, Directive, ElementRef, EventEmitter, Input, OnDestroy, OnInit, Output } from '@angular/core'
   4 import { PeerTubeRouterService, RouterSetting } from '@app/core'
   5
   6 @Directive({
   7   selector: '[myInfiniteScroller]'
   8 })
   9 export class InfiniteScrollerDirective implements OnInit, OnDestroy, AfterViewChecked {
  10   @Input() percentLimit = 70
  11   @Input() onItself = false
  12   @Input() dataObservable: Observable<any[]>
  13
  14   // Add angular state in query params to reuse the routed component
  15   @Input() setAngularState: boolean
  16
  17   @Output() nearOfBottom = new EventEmitter<void>()
  18
  19   private decimalLimit = 0
  20   private lastCurrentBottom = -1
  21   private scrollDownSub: Subscription
  22   private container: HTMLElement
  23
  24   private checkScroll = false
  25
  26   constructor (
  27     private peertubeRouter: PeerTubeRouterService,
  28     private el: ElementRef
  29   ) {
  30     this.decimalLimit = this.percentLimit / 100
  31   }
  32
  33   ngAfterViewChecked () {
  34     if (this.checkScroll) {
  35       this.checkScroll = false
  36
  37       // Wait HTML update
  38       setTimeout(() => {
  39         if (this.hasScroll() === false) this.nearOfBottom.emit()
  40       })
  41     }
  42   }
  43
  44   ngOnInit () {
  45     this.initialize()
  46   }
  47
  48   ngOnDestroy () {
  49     if (this.scrollDownSub) this.scrollDownSub.unsubscribe()
  50   }
  51
  52   initialize () {
  53     this.container = this.onItself
  54       ? this.el.nativeElement
  55       : document.documentElement
  56
  57     // Emit the last value
  58     const throttleOptions = { leading: true, trailing: true }
  59
  60     const scrollableElement = this.onItself ? this.container : window
  61     const scrollObservable = fromEvent(scrollableElement, 'scroll')
  62       .pipe(
  63         startWith(true),
  64         throttleTime(200, undefined, throttleOptions),
  65         map(() => this.getScrollInfo()),
  66         distinctUntilChanged((o1, o2) => o1.current === o2.current),
  67         share()
  68       )
  69
  70     // Scroll Down
  71     this.scrollDownSub = scrollObservable
  72       .pipe(
  73         filter(({ current }) => this.isScrollingDown(current)),
  74         filter(({ current, maximumScroll }) => (current / maximumScroll) > this.decimalLimit)
  75       )
  76       .subscribe(() => {
  77         if (this.setAngularState) this.setScrollRouteParams()
  78
  79         this.nearOfBottom.emit()
  80       })
  81
  82     if (this.dataObservable) {
  83       this.dataObservable
  84           .pipe(filter(d => d.length !== 0))
  85           .subscribe(() => this.checkScroll = true)
  86     }
  87   }
  88
  89   private getScrollInfo () {
  90     return { current: this.container.scrollTop, maximumScroll: this.getMaximumScroll() }
  91   }
  92
  93   private getMaximumScroll () {
  94     const elementHeight = this.onItself ? this.container.clientHeight : window.innerHeight
  95
  96     return this.container.scrollHeight - elementHeight
  97   }
  98
  99   private hasScroll () {
 100     return this.getMaximumScroll() > 0
 101   }
 102
 103   private isScrollingDown (current: number) {
 104     const result = this.lastCurrentBottom < current
 105
 106     this.lastCurrentBottom = current
 107     return result
 108   }
 109
 110   private setScrollRouteParams () {
 111     this.peertubeRouter.addRouteSetting(RouterSetting.REUSE_COMPONENT)
 112   }
 113 }