feat(driver): add backend delegate service (#3146)

libs/driver/in-memory/src/backend/backends.token.ts

@@ -0,0 +1,8 @@
+import { createServicesInjectionToken } from '@daffodil/core';
+
+import { DaffInMemoryBackendInterface } from './type';
+
+export const {
+  token: DAFF_IN_MEMORY_BACKENDS,
+  provider: provideDaffInMemoryBackends,
+} = createServicesInjectionToken<DaffInMemoryBackendInterface>('DAFF_IN_MEMORY_BACKENDS');

libs/driver/in-memory/src/backend/delegate.service.spec.ts

@@ -0,0 +1,66 @@
+import { STATUS } from 'angular-in-memory-web-api';
+
+import {
+  DaffInMemoryBackendInterface,
+  DaffInMemoryDataServiceInterface,
+} from '@daffodil/driver/in-memory';
+
+import { DaffInMemoryBackendDelegate } from './delegate.service';
+
+describe('@daffodil/driver/in-memory', () => {
+  let service: DaffInMemoryBackendDelegate;
+  let backends: Array<jasmine.SpyObj<DaffInMemoryBackendInterface>>;
+  let methods: Array<keyof DaffInMemoryDataServiceInterface>;
+
+  beforeEach(() => {
+    methods = ['get', 'put', 'post', 'delete'];
+    backends = [
+      jasmine.createSpyObj('a', methods, {
+        collectionName: 'a',
+      }),
+      jasmine.createSpyObj('b', methods, {
+        collectionName: 'b',
+      }),
+      jasmine.createSpyObj('c', [], {
+        collectionName: 'c',
+      }),
+    ];
+    service = new DaffInMemoryBackendDelegate(backends);
+  });
+
+  // eslint-disable-next-line guard-for-in
+  for (const method in methods) {
+    describe(method, () => {
+      it('should delegate requests to the correct backend', () => {
+        const reqInfo: any = {
+          collectionName: 'a',
+        };
+        service[method](reqInfo);
+        expect(backends[0][method]).toHaveBeenCalledWith(reqInfo);
+        reqInfo.collectionName = 'b';
+        service[method](reqInfo);
+        expect(backends[1][method]).toHaveBeenCalledWith(reqInfo);
+      });
+
+      it('should return a "not found" if the method is missing from the backend', (done) => {
+        const reqInfo: any = {
+          collectionName: 'c',
+        };
+        service[method](reqInfo).subscribe((res) => {
+          expect(res.status).toEqual(STATUS.NOT_FOUND);
+          done();
+        });
+      });
+
+      it('should return a "not found" if there isn\'t a backend for the collection name', (done) => {
+        const reqInfo: any = {
+          collectionName: '404backendnotfound',
+        };
+        service[method](reqInfo).subscribe((res) => {
+          expect(res.status).toEqual(STATUS.NOT_FOUND);
+          done();
+        });
+      });
+    });
+  }
+});

libs/driver/in-memory/src/backend/delegate.service.ts

@@ -0,0 +1,51 @@
+import {
+  Inject,
+  Injectable,
+} from '@angular/core';
+import {
+  RequestInfo,
+  STATUS,
+} from 'angular-in-memory-web-api';
+import { Observable } from 'rxjs';
+
+import { DAFF_IN_MEMORY_BACKENDS } from './backends.token';
+import { DaffInMemoryDataServiceInterface } from './data-service.type';
+import { DaffInMemoryBackendInterface } from './type';
+
+/**
+ * An in-memory backend that automatically delegates requests to backends provided to {@link DAFF_IN_MEMORY_BACKENDS}.
+ *
+ * @inheritdoc
+ */
+@Injectable({
+  providedIn: 'root',
+})
+export class DaffInMemoryBackendDelegate implements DaffInMemoryDataServiceInterface {
+  constructor(
+    @Inject(DAFF_IN_MEMORY_BACKENDS) private backends: Array<DaffInMemoryBackendInterface>,
+  ) {}
+
+  protected delegateRequest(reqInfo: RequestInfo, method: keyof DaffInMemoryDataServiceInterface): Observable<any> {
+    const backend = this.backends.find((b) => b.collectionName === reqInfo.collectionName);
+    return backend?.[method](reqInfo) || reqInfo.utils.createResponse$(() => ({
+      status: STATUS.NOT_FOUND,
+      statusText: `Backend ${reqInfo.collectionName} not found or does not support the ${method} request method`,
+    }));
+  }
+
+  get?(reqInfo: RequestInfo): Observable<any> {
+    return this.delegateRequest(reqInfo, 'get');
+  }
+
+  post?(reqInfo: RequestInfo): Observable<any> {
+    return this.delegateRequest(reqInfo, 'post');
+  }
+
+  put?(reqInfo: RequestInfo): Observable<any> {
+    return this.delegateRequest(reqInfo, 'put');
+  }
+
+  delete?(reqInfo: RequestInfo): Observable<any> {
+    return this.delegateRequest(reqInfo, 'delete');
+  }
+}

libs/driver/in-memory/src/backend/public_api.ts

@@ -1 +1,4 @@
+export * from './backends.token';
 export * from './data-service.type';
+export * from './delegate.service';
+export * from './type';

libs/driver/in-memory/src/backend/type.ts

@@ -0,0 +1,12 @@
+import { DaffInMemoryDataServiceInterface } from './data-service.type';
+
+/**
+ * An interface for defining in memory backends that use the angular in memory web api.
+ */
+export interface DaffInMemoryBackendInterface extends DaffInMemoryDataServiceInterface {
+  /**
+   * The collection name of the backend service.
+   * Used for routing requests to the correct backend.
+   */
+  readonly collectionName: string;
+}

libs/driver/package.json

@@ -26,6 +26,9 @@
     "publish": "cd ../../dist/driver && npm publish --access=public"
   },
   "homepage": "https://github.com/graycoreio/daffodil",
+  "optionalDependencies": {
+    "angular-in-memory-web-api": "0.0.0-PLACEHOLDER"
+  },
   "peerDependencies": {
     "@angular/common": "0.0.0-PLACEHOLDER",
     "@angular/core": "0.0.0-PLACEHOLDER",