refactor: rename to toDayDiffInclusive with minor fix

src/helpers/to-date-range.ts → src/helpers/to-day-diff-inclusive.ts

@@ -2,6 +2,6 @@
  * Compute the date range with given `min` and `max` (inclusive).
  * When the difference between `min` and `max` is within 1 day, it will be rounded as 1 day.
  */
-export function toDateRange(min: number | Date, max: number | Date): number {
-  return Math.ceil((+max - +min) / 864e5) + 1;
+export function toDayDiffInclusive(min: number | Date, max: number | Date): number {
+  return 1 + Math.floor((+max - +min) / 864e5);
 }

src/helpers/to-next-selectable-date.ts

@@ -2,7 +2,7 @@ import { toUTCDate } from 'nodemod/dist/calendar/helpers/to-utc-date.js';
 
 import { navigationKeySetDayNext, navigationKeySetDayPrevious } from '../constants.js';
 import type { InferredFromSet } from '../typings.js';
-import { toDateRange } from './to-date-range.js';
+import { toDayDiffInclusive } from './to-day-diff-inclusive.js';
 import type { ToNextSelectableDateInit } from './typings.js';
 
 export function toNextSelectableDate({
@@ -14,7 +14,7 @@ export function toNextSelectableDate({
   minTime,
 }: ToNextSelectableDateInit): Date {
   // Bail when there is no valid date range (<= 1 day).
-  if (toDateRange(minTime, maxTime) <= 1) return date;
+  if (toDayDiffInclusive(minTime, maxTime) <= 1) return date;
 
   const focusedDateTime = +date;
 

src/helpers/to-year-list.ts

@@ -1,7 +1,7 @@
-import { toDateRange } from './to-date-range.js';
+import { toDayDiffInclusive } from './to-day-diff-inclusive.js';
 
 export function toYearList(min: Date, max: Date): number[] {
-  if (toDateRange(min, max) < 1) return [];
+  if (toDayDiffInclusive(min, max) < 1) return [];
 
   const fy = min.getUTCFullYear();
 

src/tests/helpers/to-date-range.test.ts → src/tests/helpers/to-date-diff-inclusive.test.ts

@@ -1,9 +1,9 @@
 import { expect } from '@open-wc/testing';
 
-import { toDateRange } from '../../helpers/to-date-range';
+import { toDayDiffInclusive } from '../../helpers/to-day-diff-inclusive';
 import { messageFormatter } from '../test-utils/message-formatter';
 
-describe(toDateRange.name, () => {
+describe(toDayDiffInclusive.name, () => {
   type A = [number | Date, number | Date, number];
 
   const cases: A[] = [
@@ -23,7 +23,7 @@ describe(toDateRange.name, () => {
     it(
       messageFormatter('returns date range (min=%s, max=%s)', a),
       () => {
-        const result = toDateRange(testMin, testMax);
+        const result = toDayDiffInclusive(testMin, testMax);
 
         expect(result).equal(expected);
       }