add filter service and enable chart states to filter lists

src/app/services/filter.service.spec.ts

@@ -0,0 +1,16 @@
+import { TestBed } from '@angular/core/testing';
+
+import { FilterService } from './filter.service';
+
+describe('FilterService', () => {
+  let service: FilterService;
+
+  beforeEach(() => {
+    TestBed.configureTestingModule({});
+    service = TestBed.inject(FilterService);
+  });
+
+  it('should be created', () => {
+    expect(service).toBeTruthy();
+  });
+});

src/app/services/filter.service.ts

@@ -0,0 +1,25 @@
+import { Injectable } from '@angular/core';
+import { StType } from '../type';
+import { BehaviorSubject } from 'rxjs';
+
+@Injectable({
+  providedIn: 'root'
+})
+
+export interface FilterInput {
+  type: StType;
+  text: string
+}
+
+export class FilterService {
+
+  constructor() { }
+
+  private filterChangeSource = new BehaviorSubject<FilterInput>({ type: StType.Folder, text: "" });
+
+  filterChanged$ = this.filterChangeSource.asObservable();
+
+  changeFilter(input: FilterInput) {
+    this.filterChangeSource.next(input);
+  }
+}