-import { Directive, EventEmitter, Input, OnInit, Output } from '@angular/core'
-import 'rxjs/add/operator/debounceTime'
-import 'rxjs/add/operator/distinct'
-import 'rxjs/add/operator/distinctUntilChanged'
-import 'rxjs/add/operator/filter'
-import 'rxjs/add/operator/map'
-import 'rxjs/add/operator/startWith'
-import 'rxjs/add/operator/throttleTime'
-import { fromEvent } from 'rxjs/observable/fromEvent'
+import { distinctUntilChanged, filter, map, share, startWith, tap, 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 {
- private static PAGE_VIEW_TOP_MARGIN = 500
-
- @Input() containerHeight: number
- @Input() pageHeight: number
+export class InfiniteScrollerDirective implements OnInit, OnDestroy, AfterContentChecked {
@Input() percentLimit = 70
- @Input() autoLoading = false
+ @Input() autoInit = false
+ @Input() onItself = false
+ @Input() dataObservable: Observable<any[]>
@Output() nearOfBottom = new EventEmitter<void>()
- @Output() nearOfTop = new EventEmitter<void>()
- @Output() pageChanged = new EventEmitter<number>()
private decimalLimit = 0
private lastCurrentBottom = -1
- private lastCurrentTop = 0
+ private scrollDownSub: Subscription
+ private container: HTMLElement
+
+ private checkScroll = false
- constructor () {
+ 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.autoLoading === true) return this.initialize()
+ if (this.autoInit === true) return this.initialize()
+ }
+
+ ngOnDestroy () {
+ if (this.scrollDownSub) this.scrollDownSub.unsubscribe()
}
initialize () {
- const scrollObservable = fromEvent(window, 'scroll')
- .startWith(true)
- .throttleTime(200)
- .map(() => ({ current: window.scrollY, maximumScroll: document.body.clientHeight - window.innerHeight }))
+ 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(null as string), // FIXME: typings
+ throttleTime(200, undefined, throttleOptions),
+ map(() => this.getScrollInfo()),
+ distinctUntilChanged((o1, o2) => o1.current === o2.current),
+ share()
+ )
// Scroll Down
- scrollObservable
- // Check we scroll down
- .filter(({ current }) => {
- const res = this.lastCurrentBottom < current
-
- this.lastCurrentBottom = current
- return res
- })
- .filter(({ current, maximumScroll }) => maximumScroll <= 0 || (current / maximumScroll) > this.decimalLimit)
- .distinct()
+ this.scrollDownSub = scrollObservable
+ .pipe(
+ filter(({ current }) => this.isScrollingDown(current)),
+ filter(({ current, maximumScroll }) => (current / maximumScroll) > this.decimalLimit)
+ )
.subscribe(() => this.nearOfBottom.emit())
- // Scroll up
- scrollObservable
- // Check we scroll up
- .filter(({ current }) => {
- const res = this.lastCurrentTop > current
-
- this.lastCurrentTop = current
- return res
- })
- .filter(({ current, maximumScroll }) => {
- return current !== 0 && (1 - (current / maximumScroll)) > this.decimalLimit
- })
- .distinct()
- .subscribe(() => this.nearOfTop.emit())
-
- // Page change
- scrollObservable
- .distinct()
- .map(({ current }) => Math.max(1, Math.round((current + InfiniteScrollerDirective.PAGE_VIEW_TOP_MARGIN) / this.pageHeight)))
- .distinctUntilChanged()
- .subscribe(res => this.pageChanged.emit(res))
+ 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
+ }
}