Try to improve infinite pagination

[github/Chocobozzz/PeerTube.git] / client / src / app / shared / video / infinite-scroller.directive.ts

diff --git a/client/src/app/shared/video/infinite-scroller.directive.ts b/client/src/app/shared/video/infinite-scroller.directive.ts
index 16e901c34f1208d7d978ffd9efbf7f6129547e4d..a02e9444a72cd91f26d892d7a436b9534906b8e5 100644 (file)
--- a/client/src/app/shared/video/infinite-scroller.directive.ts
+++ b/client/src/app/shared/video/infinite-scroller.directive.ts
@@ -1,23 +1,16 @@
-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 { distinct, distinctUntilChanged, filter, map, share, startWith, throttleTime } from 'rxjs/operators'
+import { Directive, EventEmitter, Input, OnDestroy, OnInit, Output } from '@angular/core'
+import { fromEvent, Subscription } from 'rxjs'
 
 @Directive({
   selector: '[myInfiniteScroller]'
 })
-export class InfiniteScrollerDirective implements OnInit {
-  private static PAGE_VIEW_TOP_MARGIN = 500
-
+export class InfiniteScrollerDirective implements OnInit, OnDestroy {
   @Input() containerHeight: number
   @Input() pageHeight: number
+  @Input() firstLoadedPage = 1
   @Input() percentLimit = 70
-  @Input() autoLoading = false
+  @Input() autoInit = false
 
   @Output() nearOfBottom = new EventEmitter<void>()
   @Output() nearOfTop = new EventEmitter<void>()
@@ -26,55 +19,86 @@ export class InfiniteScrollerDirective implements OnInit {
   private decimalLimit = 0
   private lastCurrentBottom = -1
   private lastCurrentTop = 0
+  private scrollDownSub: Subscription
+  private scrollUpSub: Subscription
+  private pageChangeSub: Subscription
+  private middleScreen: number
 
   constructor () {
     this.decimalLimit = this.percentLimit / 100
   }
 
   ngOnInit () {
-    if (this.autoLoading === true) return this.initialize()
+    if (this.autoInit === true) return this.initialize()
+  }
+
+  ngOnDestroy () {
+    if (this.scrollDownSub) this.scrollDownSub.unsubscribe()
+    if (this.scrollUpSub) this.scrollUpSub.unsubscribe()
+    if (this.pageChangeSub) this.pageChangeSub.unsubscribe()
   }
 
   initialize () {
+    this.middleScreen = window.innerHeight / 2
+
+    // Emit the last value
+    const throttleOptions = { leading: true, trailing: true }
+
     const scrollObservable = fromEvent(window, 'scroll')
-      .startWith(true)
-      .throttleTime(200)
-      .map(() => ({ current: window.scrollY, maximumScroll: document.body.clientHeight - window.innerHeight }))
+      .pipe(
+        startWith(null),
+        throttleTime(200, undefined, throttleOptions),
+        map(() => ({ current: window.scrollY, maximumScroll: document.body.clientHeight - window.innerHeight })),
+        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(
+        // 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)
+      )
       .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()
+    this.scrollUpSub = scrollObservable
+      .pipe(
+        // 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
+        })
+      )
       .subscribe(() => this.nearOfTop.emit())
 
     // Page change
-    scrollObservable
-      .distinct()
-      .map(({ current }) => Math.max(1, Math.round((current + InfiniteScrollerDirective.PAGE_VIEW_TOP_MARGIN) / this.pageHeight)))
-      .distinctUntilChanged()
+    this.pageChangeSub = scrollObservable
+      .pipe(
+        distinct(),
+        map(({ current }) => this.calculateCurrentPage(current)),
+        distinctUntilChanged()
+      )
       .subscribe(res => this.pageChanged.emit(res))
   }
 
+  private calculateCurrentPage (current: number) {
+    const scrollY = current + this.middleScreen
+
+    const page = Math.max(1, Math.ceil(scrollY / this.pageHeight))
+
+    // Offset page
+    return page + (this.firstLoadedPage - 1)
+  }
 }