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1 | import { Directive, EventEmitter, Input, OnInit, Output } from '@angular/core' | |
2 | import 'rxjs/add/operator/distinct' | |
3 | import 'rxjs/add/operator/startWith' | |
4 | import { fromEvent } from 'rxjs/observable/fromEvent' | |
5 | ||
6 | @Directive({ | |
7 | selector: '[myInfiniteScroller]' | |
8 | }) | |
9 | export class InfiniteScrollerDirective implements OnInit { | |
10 | private static PAGE_VIEW_TOP_MARGIN = 500 | |
11 | ||
12 | @Input() containerHeight: number | |
13 | @Input() pageHeight: number | |
14 | @Input() percentLimit = 70 | |
15 | @Input() autoLoading = false | |
16 | ||
17 | @Output() nearOfBottom = new EventEmitter<void>() | |
18 | @Output() nearOfTop = new EventEmitter<void>() | |
19 | @Output() pageChanged = new EventEmitter<number>() | |
20 | ||
21 | private decimalLimit = 0 | |
22 | private lastCurrentBottom = -1 | |
23 | private lastCurrentTop = 0 | |
24 | ||
25 | constructor () { | |
26 | this.decimalLimit = this.percentLimit / 100 | |
27 | } | |
28 | ||
29 | ngOnInit () { | |
30 | if (this.autoLoading === true) return this.initialize() | |
31 | } | |
32 | ||
33 | initialize () { | |
34 | const scrollObservable = fromEvent(window, 'scroll') | |
35 | .startWith(true) | |
36 | .map(() => ({ current: window.scrollY, maximumScroll: document.body.clientHeight - window.innerHeight })) | |
37 | ||
38 | // Scroll Down | |
39 | scrollObservable | |
40 | // Check we scroll down | |
41 | .filter(({ current }) => { | |
42 | const res = this.lastCurrentBottom < current | |
43 | ||
44 | this.lastCurrentBottom = current | |
45 | return res | |
46 | }) | |
47 | .filter(({ current, maximumScroll }) => maximumScroll <= 0 || (current / maximumScroll) > this.decimalLimit) | |
48 | .debounceTime(200) | |
49 | .distinct() | |
50 | .subscribe(() => this.nearOfBottom.emit()) | |
51 | ||
52 | // Scroll up | |
53 | scrollObservable | |
54 | // Check we scroll up | |
55 | .filter(({ current }) => { | |
56 | const res = this.lastCurrentTop > current | |
57 | ||
58 | this.lastCurrentTop = current | |
59 | return res | |
60 | }) | |
61 | .filter(({ current, maximumScroll }) => { | |
62 | return current !== 0 && (1 - (current / maximumScroll)) > this.decimalLimit | |
63 | }) | |
64 | .debounceTime(200) | |
65 | .distinct() | |
66 | .subscribe(() => this.nearOfTop.emit()) | |
67 | ||
68 | // Page change | |
69 | scrollObservable | |
70 | .debounceTime(500) | |
71 | .distinct() | |
72 | .map(({ current }) => Math.max(1, Math.round((current + InfiniteScrollerDirective.PAGE_VIEW_TOP_MARGIN) / this.pageHeight))) | |
73 | .distinctUntilChanged() | |
74 | .subscribe(res => this.pageChanged.emit(res)) | |
75 | } | |
76 | ||
77 | } |