From 8471fe40a54b65a6b4cc66a1c32a46cbfb2bb510 Mon Sep 17 00:00:00 2001
From: Cilibiu Bogdan <pionnegru@users.noreply.github.com>
Date: Fri, 15 Jan 2021 13:35:39 +0200
Subject: [PATCH] [ADF-5311] Extract infinite select scroll loading logic to a
 reusable component (#6536)

* move translation to core

* select scroll directive

* register directive

* add infinite scroll directive

* clean up component and aditional logic

* use  waitForAsync over async

* update docs

* change output emitter name

* revert to async

* restore default value;

* test
---
 docs/README.md                                |  1 +
 .../infinite-select-scroll.directive.md       | 30 +++++++
 lib/content-services/src/lib/i18n/en.json     |  3 -
 .../sites-dropdown.component.html             |  2 +
 .../sites-dropdown.component.spec.ts          |  4 +-
 .../site-dropdown/sites-dropdown.component.ts | 42 ++--------
 lib/core/directives/directive.module.ts       |  7 +-
 .../infinite-select-scroll.directive.spec.ts  | 82 +++++++++++++++++++
 .../infinite-select-scroll.directive.ts       | 66 +++++++++++++++
 lib/core/directives/public-api.ts             |  1 +
 lib/core/i18n/en.json                         |  3 +
 11 files changed, 200 insertions(+), 41 deletions(-)
 create mode 100644 docs/core/directives/infinite-select-scroll.directive.md
 create mode 100644 lib/core/directives/infinite-select-scroll.directive.spec.ts
 create mode 100644 lib/core/directives/infinite-select-scroll.directive.ts

diff --git a/docs/README.md b/docs/README.md
index cc8ea2c26f..d5991cf2f7 100644
--- a/docs/README.md
+++ b/docs/README.md
@@ -138,6 +138,7 @@ The main purpose of the Notification history component is list all the notificat
 | [Node Restore directive](core/directives/node-restore.directive.md) | Restores deleted nodes to their original location. | [Source](../lib/core/directives/node-restore.directive.ts) |
 | [Upload Directive](core/directives/upload.directive.md) | Uploads content in response to file drag and drop. | [Source](../lib/core/directives/upload.directive.ts) |
 | [Version Compatibility Directive](core/directives/version-compatibility.directive.md) | Enables/disables components based on ACS version in use. | [Source](../lib/core/directives/version-compatibility.directive.ts) |
+| [Infinite Select Scroll](core/directives/infinite-select-scroll.directive.md) | Load more options to select component if API returns more items. | [Source](../lib/core/directives/infinite-select-scroll.directive.ts) |
 
 ### Dialogs
 
diff --git a/docs/core/directives/infinite-select-scroll.directive.md b/docs/core/directives/infinite-select-scroll.directive.md
new file mode 100644
index 0000000000..3c9d911789
--- /dev/null
+++ b/docs/core/directives/infinite-select-scroll.directive.md
@@ -0,0 +1,30 @@
+---
+Title: Infinite Select Scroll directive
+Added: v4.3.0
+Status: Active
+Last reviewed: 2020-01-14
+---
+
+# [Infinite Select Scroll](../../../lib/core/directives/infinite-select-scroll.directive.ts "Defined in infinite-select-scroll.directive.ts")
+
+Load more options to select component if API returns more items
+
+## Basic Usage
+
+```html
+<mat-select
+    adf-infinite-select-scroll
+    (scrollEnd)="load()">
+    <mat-option *ngFor="let option of options">
+        {{ option }}
+    </mat-option>
+</mat-select>`
+```
+
+## Class members
+
+### Events
+
+| Name | Type | Description |
+| --- | --- | --- |
+| scrollEnd | [`EventEmitter`](https://angular.io/api/core/EventEmitter)`<`[`Event`](https://developer.mozilla.org/en-US/docs/Web/API/Event)`>` | Emitted when scroll reaches the last item. |
diff --git a/lib/content-services/src/lib/i18n/en.json b/lib/content-services/src/lib/i18n/en.json
index 1218374c7f..f5f9dddc4b 100644
--- a/lib/content-services/src/lib/i18n/en.json
+++ b/lib/content-services/src/lib/i18n/en.json
@@ -30,9 +30,6 @@
       "ARROW_ICON": "Arrow right icon"
     }
   },
-  "ADF_DROPDOWN": {
-    "LOADING": "Loading..."
-  },
   "ADF_CONFIRM_DIALOG": {
     "TITLE": "Confirm",
     "ACTION": "Do you want to proceed?",
diff --git a/lib/content-services/src/lib/site-dropdown/sites-dropdown.component.html b/lib/content-services/src/lib/site-dropdown/sites-dropdown.component.html
index 43ed4f552a..ed95b31ae7 100644
--- a/lib/content-services/src/lib/site-dropdown/sites-dropdown.component.html
+++ b/lib/content-services/src/lib/site-dropdown/sites-dropdown.component.html
@@ -1,6 +1,8 @@
 <div id="site-dropdown-container" class="adf-site-dropdown-container">
     <mat-form-field>
         <mat-select
+            adf-infinite-select-scroll
+            (scrollEnd)="loadAllOnScroll()"
             #siteSelect
             data-automation-id="site-my-files-option"
             class="adf-site-dropdown-list-element"
diff --git a/lib/content-services/src/lib/site-dropdown/sites-dropdown.component.spec.ts b/lib/content-services/src/lib/site-dropdown/sites-dropdown.component.spec.ts
index 4ea46c258a..d245a7a644 100644
--- a/lib/content-services/src/lib/site-dropdown/sites-dropdown.component.spec.ts
+++ b/lib/content-services/src/lib/site-dropdown/sites-dropdown.component.spec.ts
@@ -16,7 +16,7 @@
  */
 
 import { DebugElement } from '@angular/core';
-import { async, ComponentFixture, TestBed } from '@angular/core/testing';
+import { ComponentFixture, TestBed, async } from '@angular/core/testing';
 import { By } from '@angular/platform-browser';
 import { DropdownSitesComponent, Relations } from './sites-dropdown.component';
 import { SitesService, setupTestBed } from '@alfresco/adf-core';
@@ -89,7 +89,7 @@ describe('DropdownSitesComponent', () => {
                 fixture.detectChanges();
                 fixture.whenStable().then(() => {
                     fixture.detectChanges();
-                    expect(element.querySelector('[data-automation-id="lsite-loading"]')).toBeNull();
+                    expect(element.querySelector('[data-automation-id="site-loading"]')).toBeNull();
                 });
             }));
 
diff --git a/lib/content-services/src/lib/site-dropdown/sites-dropdown.component.ts b/lib/content-services/src/lib/site-dropdown/sites-dropdown.component.ts
index fce650d616..4441731fa6 100644
--- a/lib/content-services/src/lib/site-dropdown/sites-dropdown.component.ts
+++ b/lib/content-services/src/lib/site-dropdown/sites-dropdown.component.ts
@@ -15,12 +15,10 @@
  * limitations under the License.
  */
 
-import { Component, EventEmitter, Input, OnInit, Output, ViewChild, ViewEncapsulation, OnDestroy } from '@angular/core';
-import { SitesService, LogService } from '@alfresco/adf-core';
+import { Component, EventEmitter, Input, OnInit, Output, ViewEncapsulation } from '@angular/core';
+import { SitesService, LogService, InfiniteSelectScrollDirective } from '@alfresco/adf-core';
 import { SitePaging, SiteEntry } from '@alfresco/js-api';
-import { MatSelect, MatSelectChange } from '@angular/material/select';
-import { Subject } from 'rxjs';
-import { takeUntil } from 'rxjs/operators';
+import { MatSelectChange } from '@angular/material/select';
 
 export enum Relations {
     Members = 'members',
@@ -34,7 +32,7 @@ export enum Relations {
     encapsulation: ViewEncapsulation.None,
     host: { 'class': 'adf-sites-dropdown' }
 })
-export class DropdownSitesComponent implements OnInit, OnDestroy {
+export class DropdownSitesComponent implements OnInit {
 
     /** Hide the "My Files" option. */
     @Input()
@@ -71,15 +69,8 @@ export class DropdownSitesComponent implements OnInit, OnDestroy {
     @Output()
     change: EventEmitter<SiteEntry> = new EventEmitter();
 
-    @ViewChild('siteSelect', { static: true })
-    siteSelect: MatSelect;
-
     private loading = true;
     private skipCount = 0;
-    private readonly MAX_ITEMS = 50;
-    private readonly ITEM_HEIGHT = 45;
-    private readonly ITEM_HEIGHT_TO_WAIT_BEFORE_LOAD_NEXT = (this.ITEM_HEIGHT * (this.MAX_ITEMS / 2));
-    private onDestroy$ = new Subject<boolean>();
 
     selected: SiteEntry = null;
     MY_FILES_VALUE = '-my-';
@@ -89,35 +80,18 @@ export class DropdownSitesComponent implements OnInit, OnDestroy {
     }
 
     ngOnInit() {
-        this.siteSelect.openedChange
-            .pipe(takeUntil(this.onDestroy$))
-            .subscribe(() => {
-                if (this.siteSelect.panelOpen) {
-                    this.siteSelect.panel.nativeElement.addEventListener('scroll', (event) => this.loadAllOnScroll(event));
-                }
-            });
-
         if (!this.siteList) {
             this.loadSiteList();
         }
     }
 
-    ngOnDestroy() {
-        this.onDestroy$.next(true);
-        this.onDestroy$.complete();
-    }
-
-    loadAllOnScroll(event) {
-        if (this.isInfiniteScrollingEnabled() && this.isScrollInNextFetchArea(event)) {
+    loadAllOnScroll() {
+        if (this.isInfiniteScrollingEnabled()) {
             this.loading = true;
             this.loadSiteList();
         }
     }
 
-    isScrollInNextFetchArea(event) {
-        return event.target.scrollTop >= (event.target.scrollHeight - event.target.offsetHeight - this.ITEM_HEIGHT_TO_WAIT_BEFORE_LOAD_NEXT);
-    }
-
     selectedSite(event: MatSelectChange) {
         this.change.emit(event.value);
     }
@@ -125,10 +99,10 @@ export class DropdownSitesComponent implements OnInit, OnDestroy {
     private loadSiteList() {
         const extendedOptions: any = {
             skipCount: this.skipCount,
-            maxItems: this.MAX_ITEMS
+            maxItems: InfiniteSelectScrollDirective.MAX_ITEMS
         };
 
-        this.skipCount += this.MAX_ITEMS;
+        this.skipCount += InfiniteSelectScrollDirective.MAX_ITEMS;
 
         if (this.relations) {
             extendedOptions.relations = [this.relations];
diff --git a/lib/core/directives/directive.module.ts b/lib/core/directives/directive.module.ts
index aceba886e9..c21c80554c 100644
--- a/lib/core/directives/directive.module.ts
+++ b/lib/core/directives/directive.module.ts
@@ -31,6 +31,7 @@ import { VersionCompatibilityDirective } from './version-compatibility.directive
 import { TooltipCardDirective } from './tooltip-card/tooltip-card.directive';
 import { OverlayModule } from '@angular/cdk/overlay';
 import { TooltipCardComponent } from './tooltip-card/tooltip-card.component';
+import { InfiniteSelectScrollDirective } from './infinite-select-scroll.directive';
 
 @NgModule({
     imports: [
@@ -49,7 +50,8 @@ import { TooltipCardComponent } from './tooltip-card/tooltip-card.component';
         UploadDirective,
         VersionCompatibilityDirective,
         TooltipCardDirective,
-        TooltipCardComponent
+        TooltipCardComponent,
+        InfiniteSelectScrollDirective
     ],
     exports: [
         HighlightDirective,
@@ -61,7 +63,8 @@ import { TooltipCardComponent } from './tooltip-card/tooltip-card.component';
         NodeDownloadDirective,
         UploadDirective,
         VersionCompatibilityDirective,
-        TooltipCardDirective
+        TooltipCardDirective,
+        InfiniteSelectScrollDirective
     ]
 })
 export class DirectiveModule {}
diff --git a/lib/core/directives/infinite-select-scroll.directive.spec.ts b/lib/core/directives/infinite-select-scroll.directive.spec.ts
new file mode 100644
index 0000000000..1d165a9738
--- /dev/null
+++ b/lib/core/directives/infinite-select-scroll.directive.spec.ts
@@ -0,0 +1,82 @@
+/*!
+ * @license
+ * Copyright 2019 Alfresco Software, Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { Component, ViewChild } from '@angular/core';
+import { ComponentFixture, fakeAsync, flush, TestBed } from '@angular/core/testing';
+import { InfiniteSelectScrollDirective } from './infinite-select-scroll.directive';
+import { setupTestBed } from '../testing/setup-test-bed';
+import {  MatSelect, MatSelectModule } from '@angular/material/select';
+import { NoopAnimationsModule } from '@angular/platform-browser/animations';
+
+@Component({
+    template: `
+        <mat-select adf-infinite-select-scroll (scrollEnd)="load()" >
+            <mat-option *ngFor="let option of options; let idx=index">
+                {{ option.text }}
+            </mat-option>
+        </mat-select>`
+})
+class TestComponent {
+    options = new Array(50).fill({text: 'dummy'});
+
+    @ViewChild(MatSelect, { static: true })
+    matSelect: MatSelect;
+
+    open() {
+        this.matSelect.open();
+    }
+
+    load() {
+        this.options.push(...new Array(10).fill({text: 'dummy'}));
+    }
+}
+
+describe('InfiniteSelectScrollDirective', () => {
+    let fixture: ComponentFixture<TestComponent>;
+    let component: TestComponent;
+
+    setupTestBed({
+        imports: [
+            MatSelectModule,
+            NoopAnimationsModule
+        ],
+        declarations: [
+            TestComponent,
+            InfiniteSelectScrollDirective
+        ]
+    });
+
+    beforeEach(() => {
+        fixture = TestBed.createComponent(TestComponent);
+        component = fixture.componentInstance;
+    });
+
+    beforeEach(fakeAsync(() => {
+        fixture.detectChanges();
+        component.open();
+        fixture.detectChanges();
+        flush();
+    }));
+
+    it('should call an action on scrollEnd event', fakeAsync(() => {
+        const panel = document.querySelector('.mat-select-panel')  as HTMLElement;
+        panel.scrollTop = panel.scrollHeight;
+        panel.dispatchEvent(new Event('scroll'));
+        fixture.detectChanges();
+        expect(component.options.length).toBe(60);
+    }));
+});
diff --git a/lib/core/directives/infinite-select-scroll.directive.ts b/lib/core/directives/infinite-select-scroll.directive.ts
new file mode 100644
index 0000000000..254b752c02
--- /dev/null
+++ b/lib/core/directives/infinite-select-scroll.directive.ts
@@ -0,0 +1,66 @@
+/*!
+ * @license
+ * Copyright 2019 Alfresco Software, Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { Inject, AfterViewInit, Directive, EventEmitter, OnDestroy, Output } from '@angular/core';
+import { MatSelect, SELECT_ITEM_HEIGHT_EM } from '@angular/material/select';
+import { Subject } from 'rxjs';
+import { takeUntil } from 'rxjs/operators';
+
+@Directive({
+    selector: '[adf-infinite-select-scroll]'
+})
+export class InfiniteSelectScrollDirective implements AfterViewInit, OnDestroy {
+    static readonly MAX_ITEMS = 50;
+
+    @Output() scrollEnd = new EventEmitter<Event>();
+
+    private onDestroy$ = new Subject<boolean>();
+    private itemHeightToWaitBeforeLoadNext = 0;
+
+    constructor(@Inject(MatSelect) private matSelect: MatSelect) {}
+
+    ngAfterViewInit() {
+        this.matSelect.openedChange
+            .pipe(takeUntil(this.onDestroy$))
+            .subscribe((opened: boolean) => {
+                if (opened) {
+                    this.itemHeightToWaitBeforeLoadNext = (this.getItemHeight() * (InfiniteSelectScrollDirective.MAX_ITEMS / 2));
+                    this.matSelect.panel.nativeElement.addEventListener('scroll', (event: Event) => this.handleScrollEvent(event));
+                }
+            });
+    }
+
+    ngOnDestroy() {
+        this.onDestroy$.next(true);
+        this.onDestroy$.complete();
+    }
+
+    private handleScrollEvent(event: Event) {
+        if (this.isScrollInNextFetchArea(event)) {
+            this.scrollEnd.emit(event);
+        }
+    }
+
+    private isScrollInNextFetchArea(event: Event): boolean {
+        const target = event.target as HTMLElement;
+        return target.scrollTop >= (target.scrollHeight - target.offsetHeight - this.itemHeightToWaitBeforeLoadNext);
+    }
+
+    private getItemHeight(): number {
+        return parseFloat(getComputedStyle(this.matSelect.panel.nativeElement).fontSize || '0') * SELECT_ITEM_HEIGHT_EM;
+    }
+}
diff --git a/lib/core/directives/public-api.ts b/lib/core/directives/public-api.ts
index bb3ee3f069..9010e85972 100644
--- a/lib/core/directives/public-api.ts
+++ b/lib/core/directives/public-api.ts
@@ -25,5 +25,6 @@ export * from './node-download.directive';
 export * from './upload.directive';
 export * from './version-compatibility.directive';
 export * from './tooltip-card/tooltip-card.directive';
+export * from './infinite-select-scroll.directive';
 
 export * from './directive.module';
diff --git a/lib/core/i18n/en.json b/lib/core/i18n/en.json
index c4a399ad70..ce5696e30d 100644
--- a/lib/core/i18n/en.json
+++ b/lib/core/i18n/en.json
@@ -529,5 +529,8 @@
     "BUTTON": {
       "ARIA_LABEL": "Clear"
     }
+  },
+  "ADF_DROPDOWN": {
+    "LOADING": "Loading..."
   }
 }