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