feat(design): add sidebar service (#3014)

libs/design/sidebar/src/public_api.ts

@@ -1,4 +1,6 @@
 export { DaffSidebarModule } from './sidebar.module';
+export * from './service/registration.type';
+export * from './service/sidebar.service';
 export * from './sidebar-viewport/sidebar-viewport.component';
 export * from './sidebar/sidebar.component';
 export * from './sidebar-header/sidebar-header.component';

libs/design/sidebar/src/service/registration.type.ts

@@ -0,0 +1,12 @@
+import { Type } from '@angular/core';
+
+/**
+ * Represents a registration of a sidebar.
+ * A collection of sidebar components is associated with an ID which can be passed to {@link DaffSidebarService#open}.
+ */
+export interface DaffSidebarRegistration {
+  id: string;
+  header?: Type<unknown>;
+  body?: Type<unknown>;
+  footer?: Type<unknown>;
+}

libs/design/sidebar/src/service/sidebar.service.spec.ts

@@ -0,0 +1,63 @@
+import { Injectable } from '@angular/core';
+import { TestBed } from '@angular/core/testing';
+import { take } from 'rxjs';
+
+import { DaffSidebarService } from './sidebar.service';
+
+@Injectable({
+  providedIn: 'root',
+})
+class TestService extends DaffSidebarService {
+  constructor() {
+    super('defaultId');
+  }
+}
+
+describe('@daffodil/design/sidebar | DaffSidebarService', () => {
+  let service: TestService;
+
+  beforeEach(() => {
+    service = TestBed.inject(TestService);
+  });
+
+  it('should init id to the default ID', (done) => {
+    service.id$.pipe(
+      take(1),
+    ).subscribe((id) => {
+      expect(id).toEqual('defaultId');
+      done();
+    });
+  });
+
+  describe('open', () => {
+    let id: string;
+
+    beforeEach(() => {
+      id = 'id';
+      service.open(id);
+    });
+
+    it('should set the ID', (done) => {
+      service.id$.pipe(
+        take(1),
+      ).subscribe((v) => {
+        expect(v).toEqual(id);
+        done();
+      });
+    });
+
+    it('should set isOpen to true', () => {
+      expect(service.isOpen()).toBeTrue();
+    });
+  });
+
+  describe('close', () => {
+    beforeEach(() => {
+      service.close();
+    });
+
+    it('should set isOpen to false', () => {
+      expect(service.isOpen()).toBeFalse();
+    });
+  });
+});

libs/design/sidebar/src/service/sidebar.service.ts

@@ -0,0 +1,53 @@
+import {
+  Signal,
+  signal,
+} from '@angular/core';
+import {
+  BehaviorSubject,
+  Observable,
+} from 'rxjs';
+
+import { DaffSidebarRegistration } from './registration.type';
+
+/**
+ * A service that stores the open state and ID of the currently opened sidebar.
+ *
+ * A default sidebar ID can be passed to the constructor that will be the initial value of `$id`.
+ */
+export abstract class DaffSidebarService {
+  protected _id$: BehaviorSubject<DaffSidebarRegistration['id']>;
+  protected _open = signal(false);
+
+  readonly id$: Observable<DaffSidebarRegistration['id']>;
+
+  get isOpen(): Signal<boolean> {
+    return this._open.asReadonly();
+  }
+
+  constructor(
+    defaultId: DaffSidebarRegistration['id'] = null,
+  ) {
+    this._id$ = new BehaviorSubject<DaffSidebarRegistration['id']>(defaultId);
+
+    this.id$ = this._id$.asObservable();
+  }
+
+  /**
+   * Opens the specified sidebar.
+   *
+   * @param id The optional sidebar ID. If omitted the most recently passed opened sidebar ID will persist (or the default if none was passed).
+   */
+  open(id?: DaffSidebarRegistration['id']) {
+    if (id) {
+      this._id$.next(id);
+    }
+    this._open.set(true);
+  };
+
+  /**
+   * Closes the sidebar. Does not clear the ID.
+   */
+  close() {
+    this._open.set(false);
+  }
+}