refactor: use range query for canteen module

src/app/modules/data/data.provider.spec.ts

@@ -14,8 +14,10 @@
  */
 import {TestBed} from '@angular/core/testing';
 import {Client} from '@openstapps/api/lib/client';
-import {SCDish, SCMessage, SCSaveableThing, SCSearchQuery,
-  SCSearchResponse, SCSearchValueFilter, SCThing, SCThingOriginType, SCThings, SCThingType} from '@openstapps/core';
+import {
+  SCDish, SCMessage, SCMultiSearchRequest, SCSaveableThing, SCSearchQuery,
+  SCSearchResponse, SCSearchValueFilter, SCThing, SCThingOriginType, SCThings, SCThingType,
+} from '@openstapps/core';
 import {sampleThingsMap} from '../../_helpers/data/sample-things';
 import {StorageProvider} from '../storage/storage.provider';
 import {DataModule} from './data.module';
@@ -96,6 +98,61 @@ describe('DataProvider', () => {
     expect(response).toEqual(sampleResponse);
   });
 
+  it('should provide backend data items using multi search query', async () => {
+    spyOn(Client.prototype as any, 'multiSearch').and.callFake(() => ({
+      then: (callback: any) => {
+        return callback({
+          a: sampleResponse,
+        });
+      },
+    }));
+    const response = await dataProvider.multiSearch({a: sampleQuery});
+    expect(response).toEqual({a: sampleResponse});
+  });
+
+  it('should partition search requests correctly', async () => {
+    const request = {
+      a: 'a',
+      b: 'b',
+      c: 'c',
+      d: 'd',
+      e: 'e',
+    } as SCMultiSearchRequest; // and response...
+    const requestCheck = Object.assign({}, request);
+    const responseShould = {
+      a: 'A',
+      b: 'B',
+      c: 'C',
+      d: 'D',
+      e: 'E',
+    };
+
+    dataProvider.backendQueriesLimit = 2;
+    spyOn(Client.prototype as any, 'multiSearch').and.callFake((req: SCMultiSearchRequest) => ({
+      then: (callback: any) => {
+        let i = 0;
+        for (const key in req) {
+          if (req.hasOwnProperty(key)) {
+            i++;
+            // @ts-ignore
+            expect(requestCheck[key]).not.toBeNull();
+            expect(requestCheck[key]).toEqual(req[key]);
+            // @ts-ignore
+            requestCheck[key] = null;
+            // @ts-ignore
+            req[key] = req[key].toUpperCase();
+          }
+        }
+        expect(i).toBeLessThanOrEqual(dataProvider.backendQueriesLimit);
+
+        return callback(req);
+      },
+    }));
+
+    const response = await dataProvider.multiSearch(request);
+    expect(response).toEqual(responseShould);
+  });
+
   it('should put an data item into the local database (storage)', async () => {
     let providedThing: SCSaveableThing<SCThing>;
     spyOn(storageProvider, 'put' as any).and.callFake((_id: any, thing: any) => {