Move generateDay functionality to dateutils and add tests

Author: ethanshar

src/dateutils.spec.js

@@ -1,5 +1,5 @@
 import XDate from 'xdate';
-import {sameMonth, sameWeek, isLTE, isGTE, month, page} from './dateutils';
+import {sameMonth, sameWeek, isLTE, isGTE, month, page, generateDay} from './dateutils';
 
 describe('dateutils', function () {
   describe('sameMonth()', function () {
@@ -162,4 +162,21 @@ describe('dateutils', function () {
       }
     });
   });
+
+  describe('generateDay', () => {
+    it('should generate a day in string format with an offset', () => {
+      expect(generateDay('2017-09-22', 2)).toBe('2017-09-24');
+      expect(generateDay('2017-09-22', -2)).toBe('2017-09-20');
+    });
+
+    it('should generate the same day when offset was not sent', () => {
+      expect(generateDay('2017-09-22')).toBe('2017-09-22');
+    });
+
+    it('should handle month and year changes', () => {
+      expect(generateDay('2017-10-22', 10)).toBe('2017-11-01');
+      expect(generateDay('2017-12-26', 10)).toBe('2018-01-05');
+      expect(generateDay('2018-01-01', -3)).toBe('2017-12-29');
+    });
+  });
 });

src/dateutils.ts

@@ -1,17 +1,14 @@
 const XDate = require('xdate');
-const {parseDate} = require('./interface');
+const {parseDate, toMarkingFormat} = require('./interface');
 
 const latinNumbersPattern = /[0-9]/g;
 
 export function sameMonth(a: XDate, b: XDate) {
-  return a.getFullYear() === b.getFullYear() && 
-    a.getMonth() === b.getMonth();
+  return a.getFullYear() === b.getFullYear() && a.getMonth() === b.getMonth();
 }
 
 export function sameDate(a: XDate, b: XDate) {
-  return a.getFullYear() === b.getFullYear() &&
-    a.getMonth() === b.getMonth() &&
-    a.getDate() === b.getDate();
+  return a.getFullYear() === b.getFullYear() && a.getMonth() === b.getMonth() && a.getDate() === b.getDate();
 }
 
 export function sameWeek(a: XDate, b: XDate, firstDayOfWeek: number) {
@@ -144,3 +141,8 @@ export function getWeekDates(date: XDate, firstDay = 0, format?: string) {
     return daysArray;
   }
 }
+
+export function generateDay(originDate: string, daysOffset = 0) {
+  const baseDate = new XDate(originDate);
+  return toMarkingFormat(baseDate.clone().addDays(daysOffset));
+}

src/timeline-list/useTimelinePages.ts

@@ -1,20 +1,16 @@
 import {RefObject, useCallback, useRef, useState} from 'react';
-import XDate from 'xdate';
+
 import inRange from 'lodash/inRange';
 import times from 'lodash/times';
 import debounce from 'lodash/debounce';
 
 import constants from '../commons/constants';
-import {toMarkingFormat} from '../interface';
+import {generateDay} from '../dateutils';
 
 const PAGES_COUNT = 100;
 const NEAR_EDGE_THRESHOLD = 10;
 export const INITIAL_PAGE = Math.floor(PAGES_COUNT / 2);
 
-const generateDay = (originDate: string, daysOffset: number) => {
-  const baseDate = new XDate(originDate);
-  return toMarkingFormat(baseDate.clone().addDays(daysOffset));
-};
 
 interface UseTimelinePagesProps {
   date: string;