Update calcNowOffset and add tests

Author: ethanshar

src/timeline/__tests__/presenter.spec.js

@@ -68,4 +68,19 @@ describe('timeline presenter', () => {
       expect(uut.buildTimeString(15, 0, '2017-03-05')).toBe('2017-03-05 15:00:00');
     });
   });
+
+  describe('calcNowOffset', () => {
+    it('should give offset based on current time', () => {
+      jest.useFakeTimers().setSystemTime(new Date('2020-01-01 15:30').getTime());
+      expect(uut.calcNowOffset(100)).toBe(1550);
+
+      jest.useFakeTimers().setSystemTime(new Date('2020-01-01 12:10').getTime());
+      expect(uut.calcNowOffset(100)).toBeCloseTo(1216.66, 1);
+    });
+
+    it('should give offset based on given time', () => {
+      expect(uut.calcNowOffset(100, 15, 30)).toBe(1550);
+      expect(uut.calcNowOffset(100, 12, 10)).toBeCloseTo(1216.66, 1);
+    });
+  });
 });

src/timeline/helpers/presenter.ts

@@ -11,9 +11,9 @@ export function buildTimeString(hour = 0, minutes = 0, date = '') {
   return `${date} ${hour.toString().padStart(2, '0')}:${minutes.toString().padStart(2, '0')}:00`.trimStart();
 }
 
-export function calcNowOffset(hourBlockHeight: number) {
+export function calcNowOffset(hourBlockHeight: number, hour?: number, minutes?: number) {
   const now = new Date();
-  const hour = now.getHours();
-  const minutes = now.getMinutes();
-  return (hour + minutes / 60) * hourBlockHeight;
+  const h = hour ?? now.getHours();
+  const m = minutes ?? now.getMinutes();
+  return (h + m / 60) * hourBlockHeight;
 }