Feature / Callback on Successful Background Data Sync

src/index.js

@@ -395,13 +395,13 @@ class SuperRepo {
      * @param  {Number} _interval - the interval, in milliseconds
      * @return {Void}
      */
-    _initSyncInterval(_interval) {
+    _initSyncInterval(_interval, _cb) {
         // Do not initiate intervals which are quicker then a second,
         // otherwise, this might be a big network (performance) overhead.
         const interval = _interval < 1000 ? 1000: _interval;
 
         return setInterval(
-            () => this._requestFreshData(), interval
+            () => this._requestFreshData().then(_cb), interval
         );
     }
 
@@ -412,7 +412,7 @@ class SuperRepo {
      *
      * @return {Void}
      */
-    initSyncer() {
+    initSyncer(_cb = () => {}) {
         const { outOfDateAfter } = this.config;
 
         return new Promise(_resolve => {
@@ -427,22 +427,24 @@ class SuperRepo {
                     const diff = new Date().valueOf() - _res.lastFetched;
                     let remainingTime = outOfDateAfter - diff;
 
-                    this.syncInterval = this._initSyncInterval(remainingTime);
+                    this.syncInterval =
+                        this._initSyncInterval(remainingTime, _cb);
 
                     setTimeout( () => {
                         this.destroySyncer();
 
                         this.syncInterval =
-                            this._initSyncInterval(outOfDateAfter);
+                            this._initSyncInterval(outOfDateAfter, _cb);
                     }, remainingTime < 1000 ? 1000 : remainingTime);
 
                     _resolve();
                 } else {
                     this._requestFreshData()
                         .then(_response => {
                             this.syncInterval =
-                                this._initSyncInterval(outOfDateAfter);
+                                this._initSyncInterval(outOfDateAfter, _cb);
 
+                            _cb();
                             _resolve();
                         });
                 }

test/data-sync.js

@@ -264,4 +264,48 @@ describe('Data Sync', () => {
             expect(networkRequestsCount).to.equal(13);
         }).then(done, done);
     });
+
+    it('Should fire a success callback as soon as the background data sync process gets fresh data. Use case: there is no data.', done => {
+        const callback = sinon.spy();
+
+        expect(callback.callCount).to.equal(0);
+
+        repository.initSyncer(callback).then( () => {
+            expect(callback.callCount).to.equal(1);
+
+            clock.tick(TIMEFRAME - 1);
+            expect(callback.callCount).to.equal(1);
+
+            clock.tick(1);
+            expect(callback.callCount).to.equal(2);
+
+            clock.tick(TIMEFRAME);
+            expect(callback.callCount).to.equal(3);
+        }).then(done, done);
+    });
+
+    it('Should fire a success callback as soon as the background data sync process gets fresh data. Use case: there is data.', done => {
+        const callback = sinon.spy();
+
+        repository.getData().then(() => {
+            expect(callback.callCount).to.equal(0);
+
+            repository.initSyncer(callback).then( () => {
+                expect(callback.callCount).to.equal(0);
+
+                clock.tick(TIMEFRAME - 1);
+                expect(callback.callCount).to.equal(0);
+
+                clock.tick(1);
+                expect(callback.callCount).to.equal(1);
+
+                clock.tick(TIMEFRAME);
+                expect(callback.callCount).to.equal(2);
+
+                clock.tick(10 * TIMEFRAME);
+                expect(callback.callCount).to.equal(12);
+            }).then(done, done);
+
+        });
+    });
 });