|
| 1 | + |
| 2 | +import { HttpClient } from '@angular/common/http'; |
| 3 | +import { Injectable } from '@angular/core'; |
| 4 | +import { SortingDirection } from 'igniteui-angular'; |
| 5 | +import { BehaviorSubject, Observable } from 'rxjs'; |
| 6 | + |
| 7 | +const DATA_URL = 'https://services.odata.org/V4/Northwind/Northwind.svc/Products'; |
| 8 | +const EMPTY_STRING = ''; |
| 9 | +export enum SortOrder { |
| 10 | + ASC = 'asc', |
| 11 | + DESC = 'desc', |
| 12 | + NONE = '' |
| 13 | +} |
| 14 | +@Injectable() |
| 15 | +export class RemoteVirtService { |
| 16 | + |
| 17 | + public data: Observable<any[]>; |
| 18 | + private _data: BehaviorSubject<any[]>; |
| 19 | + private _cachedData: any[]; |
| 20 | + |
| 21 | + constructor(private _http: HttpClient) { |
| 22 | + this._data = new BehaviorSubject([]); |
| 23 | + this.data = this._data.asObservable(); |
| 24 | + } |
| 25 | + |
| 26 | + public hasItemsInCache(virtualizationArgs?) { |
| 27 | + const startIndex = virtualizationArgs.startIndex; |
| 28 | + const endIndex = virtualizationArgs.chunkSize + startIndex; |
| 29 | + let areAllItemsInCache = true; |
| 30 | + for (let i = startIndex; i < endIndex; i++) { |
| 31 | + if (this._cachedData[i] === null) { |
| 32 | + areAllItemsInCache = false; |
| 33 | + break; |
| 34 | + } |
| 35 | + } |
| 36 | + return areAllItemsInCache; |
| 37 | + } |
| 38 | + |
| 39 | + public getData(virtualizationArgs?, sortingArgs?: any, resetData?: boolean, cb?: (any) => void): any { |
| 40 | + const startIndex = virtualizationArgs.startIndex; |
| 41 | + const endIndex = virtualizationArgs.chunkSize + startIndex; |
| 42 | + |
| 43 | + if (resetData) { |
| 44 | + this._http.get(this._buildDataUrl(virtualizationArgs, sortingArgs)).subscribe((data: any) => { |
| 45 | + this._cachedData = new Array<any>(data['@odata.count']).fill(null); |
| 46 | + this._updateData(data, startIndex); |
| 47 | + if (cb) { |
| 48 | + cb(data); |
| 49 | + } |
| 50 | + }); |
| 51 | + |
| 52 | + return; |
| 53 | + } |
| 54 | + |
| 55 | + if (!this.hasItemsInCache(virtualizationArgs)) { |
| 56 | + this._http.get(this._buildDataUrl(virtualizationArgs, sortingArgs)).subscribe((data: any) => { |
| 57 | + this._updateData(data, startIndex); |
| 58 | + if (cb) { |
| 59 | + cb(data); |
| 60 | + } |
| 61 | + }); |
| 62 | + } else { |
| 63 | + const data = this._cachedData.slice(startIndex, endIndex); |
| 64 | + this._data.next(data); |
| 65 | + if (cb) { |
| 66 | + cb(data); |
| 67 | + } |
| 68 | + } |
| 69 | + } |
| 70 | + |
| 71 | + private _updateData(data: any, startIndex: number) { |
| 72 | + this._data.next(data.value); |
| 73 | + for (let i = 0; i < data.value.length; i++) { |
| 74 | + this._cachedData[i + startIndex] = data.value[i]; |
| 75 | + } |
| 76 | + } |
| 77 | + |
| 78 | + private _buildDataUrl(virtualizationArgs: any, sortingArgs: any): string { |
| 79 | + let baseQueryString = `${DATA_URL}?$count=true`; |
| 80 | + let scrollingQuery = EMPTY_STRING; |
| 81 | + let orderQuery = EMPTY_STRING; |
| 82 | + let query = EMPTY_STRING; |
| 83 | + |
| 84 | + if (sortingArgs) { |
| 85 | + let sortingDirection: string; |
| 86 | + switch (sortingArgs.dir) { |
| 87 | + case SortingDirection.Asc: |
| 88 | + sortingDirection = SortOrder.ASC; |
| 89 | + break; |
| 90 | + case SortingDirection.Desc: |
| 91 | + sortingDirection = SortOrder.DESC; |
| 92 | + break; |
| 93 | + default: |
| 94 | + sortingDirection = SortOrder.NONE; |
| 95 | + } |
| 96 | + |
| 97 | + orderQuery = `$orderby=${sortingArgs.fieldName} ${sortingDirection}`; |
| 98 | + } |
| 99 | + |
| 100 | + if (virtualizationArgs) { |
| 101 | + let requiredChunkSize: number; |
| 102 | + const skip = virtualizationArgs.startIndex; |
| 103 | + requiredChunkSize = virtualizationArgs.chunkSize === 0 ? 11 : virtualizationArgs.chunkSize; |
| 104 | + const top = requiredChunkSize; |
| 105 | + scrollingQuery = `$skip=${skip}&$top=${top}`; |
| 106 | + } |
| 107 | + |
| 108 | + query += (orderQuery !== EMPTY_STRING) ? `&${orderQuery}` : EMPTY_STRING; |
| 109 | + query += (scrollingQuery !== EMPTY_STRING) ? `&${scrollingQuery}` : EMPTY_STRING; |
| 110 | + |
| 111 | + baseQueryString += query; |
| 112 | + |
| 113 | + return baseQueryString; |
| 114 | + } |
| 115 | +} |
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