#10 getCachedObservable implemented

etsuo · etsuo · commit 80b2c4bf137a · 2018-03-15T19:12:12.000-07:00
diff --git a/src/app/shared/rxjs-imports.ts b/src/app/shared/rxjs-imports.ts
@@ -10,6 +10,7 @@ import 'rxjs/add/operator/concatMap';
 import 'rxjs/add/operator/delay';
 import 'rxjs/add/operator/do';
 import 'rxjs/add/operator/map';
+import 'rxjs/add/operator/mergeMap';
 import 'rxjs/add/operator/publishReplay';
 import 'rxjs/add/operator/retryWhen';
 import 'rxjs/add/operator/take';
diff --git a/src/app/shared/services/storage.service.spec.ts b/src/app/shared/services/storage.service.spec.ts
@@ -313,5 +313,52 @@ describe('StorageService', () => {
         done.fail(err);
       }
     });
+
+    describe('getCachedObservable', () => {
+      it('calls observable if not yet cached', async (done) => {
+        try {
+          for (const type of stores) {
+
+            const obs = Observable.of('observable called');
+            await store[type].getCachedObservable('test', obs).toPromise();
+            expect(await store[type].getItem('test').toPromise()).toBe('observable called', type);
+          }
+          done();
+        } catch (err) {
+          done.fail(err);
+        }
+      });
+
+      it('returns cached value instead of observable', async (done) => {
+        try {
+          for (const type of stores) {
+
+            const obs = Observable.of('observable called');
+            await store[type].setItem('test', 'cached value');
+            expect(await store[type].getCachedObservable('test', obs).toPromise()).toBe('cached value', type);
+          }
+          done();
+        } catch (err) {
+          done.fail(err);
+        }
+      });
+
+      it('returns observable value after cache expiration', async (done) => {
+        try {
+          for (const type of stores) {
+            const obs = Observable.of('observable called');
+            await store[type].setItem('test', 'cached value', 1);
+            expect(await store[type].getCachedObservable('test', obs).toPromise()).toBe('cached value', type);
+
+            await new Promise((resolve) => setTimeout(resolve, 1010));
+            expect(await store[type].getCachedObservable('test', obs).toPromise()).toBe('observable called', type);
+
+          }
+          done();
+        } catch (err) {
+          done.fail(err);
+        }
+      });
+    });
   });
 });
diff --git a/src/app/shared/services/storage.service.ts b/src/app/shared/services/storage.service.ts
@@ -140,6 +140,15 @@ export abstract class BaseStorageService {
    */
   abstract getStorageEngine(): Observable<StorageEngine>;
 
+  getCachedObservable<T>(key: string, observable: Observable<T>, cacheTTL = 0, gc = false): Observable<T> {
+    return this
+      .getItem(key)
+      .map((val) => val || null)
+      .flatMap((val: any) => (val !== null)
+        ? Observable.of(val)
+        : observable.flatMap((obsVal: any) => this.setItem(key, obsVal, cacheTTL, gc)));
+  }
+
   /**
    * Gets an observable that emits an updated value each time its key is set. Use this to monitor changes to a key/value
    * in the store.
