feat(product): transfer in-memory state when hydrating backend (#4148)

Author: damienwebdev

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

@@ -1,3 +1,7 @@
+import {
+  PLATFORM_ID,
+  TransferState,
+} from '@angular/core';
 import { TestBed } from '@angular/core/testing';
 
 import {
@@ -7,6 +11,7 @@ import {
 } from '@daffodil/product/testing';
 
 import { DaffInMemoryBackendProductService } from './product.service';
+import { TRANSFER_STATE_KEY } from './transfer-state-key';
 
 describe('Driver | InMemory | Product | DaffInMemoryBackendProductService', () => {
   let productTestingService;
@@ -26,6 +31,85 @@ describe('Driver | InMemory | Product | DaffInMemoryBackendProductService', () =
     expect(productTestingService).toBeTruthy();
   });
 
+  describe('transferring state from the server to the browser', () => {
+    describe('on browser platform', () => {
+      let transferState: TransferState;
+      let mockProducts;
+
+      beforeEach(() => {
+        mockProducts = [
+          { id: '1', url: '/product-1.html', name: 'Product 1' },
+          { id: '2', url: '/product-2.html', name: 'Product 2' },
+        ];
+
+        TestBed.resetTestingModule();
+        TestBed.configureTestingModule({
+          providers: [
+            DaffInMemoryBackendProductService,
+            provideDaffProductExtraFactoryTypes(DaffProductFactory),
+            { provide: PLATFORM_ID, useValue: 'browser' },
+          ],
+        });
+
+        transferState = TestBed.inject(TransferState);
+        transferState.set(TRANSFER_STATE_KEY, mockProducts);
+
+        productTestingService = TestBed.inject(DaffInMemoryBackendProductService);
+      });
+
+      it('should load products from transfer state', () => {
+        expect(productTestingService.products).toEqual(mockProducts);
+      });
+
+      it('should not create new products', () => {
+        expect(productTestingService.products.length).toEqual(2);
+      });
+    });
+
+    describe('on browser platform without transfer state', () => {
+      beforeEach(() => {
+        TestBed.resetTestingModule();
+        TestBed.configureTestingModule({
+          providers: [
+            DaffInMemoryBackendProductService,
+            provideDaffProductExtraFactoryTypes(DaffProductFactory),
+            { provide: PLATFORM_ID, useValue: 'browser' },
+          ],
+        });
+
+        productTestingService = TestBed.inject(DaffInMemoryBackendProductService);
+      });
+
+      it('should create default products from factory', () => {
+        expect(productTestingService.products.length).toEqual(35);
+      });
+    });
+
+    describe('on server platform', () => {
+      let transferState: TransferState;
+
+      beforeEach(() => {
+        TestBed.resetTestingModule();
+        TestBed.configureTestingModule({
+          providers: [
+            DaffInMemoryBackendProductService,
+            provideDaffProductExtraFactoryTypes(DaffProductFactory),
+            { provide: PLATFORM_ID, useValue: 'server' },
+          ],
+        });
+
+        transferState = TestBed.inject(TransferState);
+        productTestingService = TestBed.inject(DaffInMemoryBackendProductService);
+      });
+
+      it('should set products in transfer state', () => {
+        const transferStateData = transferState.get(TRANSFER_STATE_KEY, null);
+        expect(transferStateData).toBeTruthy();
+        expect(Array.isArray(transferStateData)).toBe(true);
+      });
+    });
+  });
+
   describe('createDb', () => {
     let result;
 

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

@@ -1,6 +1,9 @@
+import { isPlatformBrowser } from '@angular/common';
 import {
   inject,
   Injectable,
+  PLATFORM_ID,
+  TransferState,
 } from '@angular/core';
 import {
   InMemoryDbService,
@@ -16,6 +19,7 @@ import { DaffProduct } from '@daffodil/product';
 import { DaffProductExtensionFactory } from '@daffodil/product/testing';
 
 import { DAFF_PRODUCT_IN_MEMORY_COLLECTION_NAME } from '../collection-name.const';
+import { TRANSFER_STATE_KEY } from './transfer-state-key';
 /**
  * An in-memory service that stubs out the backend services for getting products.
  *
@@ -38,10 +42,17 @@ export class DaffInMemoryBackendProductService implements InMemoryDbService, Daf
     return this._products;
   };
 
-  productFactory = inject(DaffProductExtensionFactory);
-
   constructor(){
-    this._products = this.productFactory.createMany(35);
+    const transferState = inject(TransferState);
+    const platform = inject(PLATFORM_ID);
+    const productFactory = inject(DaffProductExtensionFactory);
+
+    if(isPlatformBrowser(platform)) {
+      this._products = transferState.get(TRANSFER_STATE_KEY, productFactory.createMany(35));
+    } else {
+      this._products = productFactory.createMany(35);
+      transferState.set(TRANSFER_STATE_KEY, this._products);
+    }
   }
 
   /**

libs/product/driver/in-memory/src/backend/transfer-state-key.ts

@@ -0,0 +1,5 @@
+import { makeStateKey } from '@angular/core';
+
+import { DaffProduct } from '@daffodil/product';
+
+export const TRANSFER_STATE_KEY = makeStateKey<DaffProduct[]>('DAFF_PRODUCTS_INMEMORY_DATA');