2018-05-15 11:55:51 +02:00
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import { distinct, distinctUntilChanged, filter, map, share, startWith, throttleTime } from 'rxjs/operators'
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2018-03-19 18:00:31 +01:00
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import { Directive, EventEmitter, Input, OnDestroy, OnInit, Output } from '@angular/core'
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2018-05-15 11:55:51 +02:00
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import { fromEvent, Subscription } from 'rxjs'
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2018-02-13 14:11:05 +01:00
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@Directive({
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selector: '[myInfiniteScroller]'
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})
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2018-03-19 18:00:31 +01:00
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export class InfiniteScrollerDirective implements OnInit, OnDestroy {
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2018-02-13 14:11:05 +01:00
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private static PAGE_VIEW_TOP_MARGIN = 500
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@Input() containerHeight: number
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@Input() pageHeight: number
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@Input() percentLimit = 70
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@Input() autoLoading = false
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@Output() nearOfBottom = new EventEmitter<void>()
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@Output() nearOfTop = new EventEmitter<void>()
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@Output() pageChanged = new EventEmitter<number>()
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private decimalLimit = 0
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private lastCurrentBottom = -1
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private lastCurrentTop = 0
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2018-03-19 18:00:31 +01:00
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private scrollDownSub: Subscription
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private scrollUpSub: Subscription
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private pageChangeSub: Subscription
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2018-02-13 14:11:05 +01:00
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constructor () {
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this.decimalLimit = this.percentLimit / 100
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}
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ngOnInit () {
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if (this.autoLoading === true) return this.initialize()
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}
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2018-03-19 18:00:31 +01:00
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ngOnDestroy () {
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if (this.scrollDownSub) this.scrollDownSub.unsubscribe()
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if (this.scrollUpSub) this.scrollUpSub.unsubscribe()
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if (this.pageChangeSub) this.pageChangeSub.unsubscribe()
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}
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2018-02-13 14:11:05 +01:00
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initialize () {
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2018-03-08 10:46:12 +01:00
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// Emit the last value
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2018-03-09 09:21:34 +01:00
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const throttleOptions = { leading: true, trailing: true }
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2018-03-08 10:46:12 +01:00
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2018-02-13 14:11:05 +01:00
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const scrollObservable = fromEvent(window, 'scroll')
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2018-05-15 11:55:51 +02:00
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.pipe(
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startWith(null),
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throttleTime(200, undefined, throttleOptions),
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map(() => ({ current: window.scrollY, maximumScroll: document.body.clientHeight - window.innerHeight })),
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distinctUntilChanged((o1, o2) => o1.current === o2.current),
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share()
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)
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2018-02-13 14:11:05 +01:00
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// Scroll Down
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2018-03-19 18:00:31 +01:00
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this.scrollDownSub = scrollObservable
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2018-05-15 11:55:51 +02:00
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.pipe(
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// Check we scroll down
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filter(({ current }) => {
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const res = this.lastCurrentBottom < current
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2018-02-13 14:11:05 +01:00
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2018-05-15 11:55:51 +02:00
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this.lastCurrentBottom = current
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return res
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}),
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filter(({ current, maximumScroll }) => maximumScroll <= 0 || (current / maximumScroll) > this.decimalLimit)
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)
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2018-02-13 14:11:05 +01:00
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.subscribe(() => this.nearOfBottom.emit())
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// Scroll up
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2018-03-19 18:00:31 +01:00
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this.scrollUpSub = scrollObservable
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2018-05-15 11:55:51 +02:00
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.pipe(
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// Check we scroll up
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filter(({ current }) => {
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const res = this.lastCurrentTop > current
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2018-02-13 14:11:05 +01:00
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2018-05-15 11:55:51 +02:00
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this.lastCurrentTop = current
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return res
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}),
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filter(({ current, maximumScroll }) => {
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return current !== 0 && (1 - (current / maximumScroll)) > this.decimalLimit
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})
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)
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2018-02-13 14:11:05 +01:00
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.subscribe(() => this.nearOfTop.emit())
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// Page change
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2018-03-19 18:00:31 +01:00
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this.pageChangeSub = scrollObservable
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2018-05-15 11:55:51 +02:00
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.pipe(
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distinct(),
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map(({ current }) => this.calculateCurrentPage(current)),
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distinctUntilChanged()
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)
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2018-02-13 14:11:05 +01:00
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.subscribe(res => this.pageChanged.emit(res))
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}
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2018-03-08 10:46:12 +01:00
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private calculateCurrentPage (current: number) {
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return Math.max(1, Math.round((current + InfiniteScrollerDirective.PAGE_VIEW_TOP_MARGIN) / this.pageHeight))
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}
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2018-02-13 14:11:05 +01:00
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}
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