feat: add audit-trails and view-audit-trail components (#406)

Fixes #404

src/app/system/audit-trails/audit-trail.datasource.ts

@@ -0,0 +1,60 @@
+/** Angular Imports */
+import { CollectionViewer, DataSource } from '@angular/cdk/collections';
+
+/** rxjs Imports */
+import { Observable, BehaviorSubject } from 'rxjs';
+
+/** Custom Services */
+import { SystemService } from '../system.service';
+
+/**
+ * Audit Trails custom data source to implement server side filtering, pagination and sorting.
+ */
+export class AuditTrailsDataSource implements DataSource<any> {
+
+  /** Audit Trails behavior subject to represent loaded audit trails page. */
+  private auditTrailsSubject = new BehaviorSubject<any[]>([]);
+  /** Records subject to represent total number of filtered audit trail records. */
+  private recordsSubject = new BehaviorSubject<number>(0);
+
+  /** Records observable which can be subscribed to get the value of total number of filtered audit trail records. */
+  public records$ = this.recordsSubject.asObservable();
+
+  /**
+   * @param {SystemService} systemService System Service.
+   */
+  constructor(private systemService: SystemService) { }
+
+  /**
+   * Gets audit trails on the basis of provided parameters and emits the value.
+   * @param {any} filterBy Properties by which entries should be filtered.
+   * @param {string} orderBy Property by which entries should be sorted.
+   * @param {string} sortOrder Sort order: ascending or descending.
+   * @param {number} pageIndex Page number.
+   * @param {number} limit Number of entries within the page.
+   */
+  getAuditTrails(filterBy: any, orderBy: string = '', sortOrder: string = '', pageIndex: number = 0, limit: number = 10) {
+    this.auditTrailsSubject.next([]);
+    this.systemService.getAuditTrails(filterBy, orderBy, sortOrder, pageIndex * limit, limit)
+      .subscribe((auditTrails: any) => {
+        this.recordsSubject.next(auditTrails.totalFilteredRecords);
+        this.auditTrailsSubject.next(auditTrails.pageItems);
+      });
+  }
+
+  /**
+   * @param {CollectionViewer} collectionViewer
+   */
+  connect(collectionViewer: CollectionViewer): Observable<any[]> {
+    return this.auditTrailsSubject.asObservable();
+  }
+
+  /**
+   * @param {CollectionViewer} collectionViewer
+   */
+  disconnect(collectionViewer: CollectionViewer): void {
+    this.auditTrailsSubject.complete();
+    this.recordsSubject.complete();
+  }
+
+}