Cacheable local storage

projects/ngx-hal/src/lib/classes/hal-storage/cache-first-fetch-later.storage.ts

@@ -0,0 +1,28 @@
+import { from, Observable, of } from 'rxjs';
+import { distinctUntilChanged, mergeMap } from 'rxjs/operators';
+import { HalModel } from '../../models/hal.model';
+import { HalDocument } from '../hal-document';
+import { EtagHalStorage } from './etag-hal-storage';
+
+export class CacheFirstFetchLaterStorage extends EtagHalStorage {
+  public makeGetRequestWrapper<T extends HalModel>(
+    urls: { originalUrl: string; cleanUrl: string; urlWithParams: string },
+    cachedResource: T | HalDocument<T>,
+    originalGetRequest$: Observable<T | HalDocument<T>>
+  ): Observable<T | HalDocument<T>> {
+    if (cachedResource) {
+      return from([of(cachedResource), originalGetRequest$]).pipe(
+        mergeMap((request) => request),
+        distinctUntilChanged(this.areModelsEqual.bind(this))
+      );
+    }
+
+    return originalGetRequest$;
+  }
+
+  private areModelsEqual<T extends HalModel>(model1: T | HalDocument<T>, model2: T | HalDocument<T>): boolean {
+    const localModel1 = this.getRawStorageModel(model1.uniqueModelIdentificator);
+    const localModel2 = this.getRawStorageModel(model2.uniqueModelIdentificator);
+    return localModel1.etag === localModel2.etag;
+  }
+}

projects/ngx-hal/src/lib/classes/hal-storage/hal-storage-factory.ts

@@ -2,6 +2,7 @@ import { CacheStrategy } from '../../enums/cache-strategy.enum';
 import { SimpleHalStorage } from '../../classes/hal-storage/simple-hal-storage';
 import { EtagHalStorage } from '../../classes/hal-storage/etag-hal-storage';
 import { HalStorage } from './hal-storage';
+import { CacheFirstFetchLaterStorage } from './cache-first-fetch-later.storage';
 
 export type HalStorageType = SimpleHalStorage | EtagHalStorage;
 
@@ -15,6 +16,9 @@ export function createHalStorage(cacheStrategy: CacheStrategy = CacheStrategy.NO
     case CacheStrategy.ETAG:
       storage = new EtagHalStorage();
       break;
+    case CacheStrategy.CACHE_FIRST_FETCH_LATER:
+      storage = new CacheFirstFetchLaterStorage();
+      break;
     case CacheStrategy.CUSTOM:
       if (!storageInstance) {
         throw new Error('When CacheStrategy.CUSTOM is specified, config.storage is required.');

projects/ngx-hal/src/lib/enums/cache-strategy.enum.ts

@@ -1,4 +1,5 @@
 export enum CacheStrategy {
+  CACHE_FIRST_FETCH_LATER = 'CACHE_FIRST_FETCH_LATER',
   CUSTOM = 'CUSTOM',
   ETAG = 'ETAG',
   NONE = 'NONE'

projects/ngx-hal/src/public_api.ts

@@ -17,6 +17,7 @@ export * from './lib/classes/pagination';
 export * from './lib/classes/hal-storage/hal-storage';
 export * from './lib/classes/hal-storage/etag-hal-storage';
 export * from './lib/classes/hal-storage/simple-hal-storage';
+export * from './lib/classes/hal-storage/cache-first-fetch-later.storage';
 
 export * from './lib/enums/cache-strategy.enum';