From 16b08bc802124e20b0fc248cc842da6a65d9ca35 Mon Sep 17 00:00:00 2001
From: Derek Burgman <derek@dereekb.com>
Date: Sat, 16 Jul 2022 02:33:23 -0500
Subject: [PATCH] feat: added DayOfWeek functions

---
 packages/util/src/lib/date/week.spec.ts | 45 +++++++++++++++++++++++++
 packages/util/src/lib/date/week.ts      | 24 +++++++++++++
 2 files changed, 69 insertions(+)
 create mode 100644 packages/util/src/lib/date/week.spec.ts

diff --git a/packages/util/src/lib/date/week.spec.ts b/packages/util/src/lib/date/week.spec.ts
new file mode 100644
index 000000000..b7f35740c
--- /dev/null
+++ b/packages/util/src/lib/date/week.spec.ts
@@ -0,0 +1,45 @@
+import { Day, getDayOffset, getNextDay, getPreviousDay } from './week';
+
+describe('getDayOffset()', () => {
+  it('should return the previous days if a negative value is input.', () => {
+    expect(getDayOffset(Day.SATURDAY, -1)).toBe(Day.FRIDAY);
+    expect(getDayOffset(Day.SUNDAY, -1)).toBe(Day.SATURDAY);
+  });
+
+  it('should return the next days if a positive value is input.', () => {
+    expect(getDayOffset(Day.SATURDAY, 1)).toBe(Day.SUNDAY);
+    expect(getDayOffset(Day.SUNDAY, 1)).toBe(Day.MONDAY);
+  });
+});
+
+describe('getPreviousDay()', () => {
+  it('should return the previous day', () => {
+    expect(getPreviousDay(Day.SATURDAY)).toBe(Day.FRIDAY);
+    expect(getPreviousDay(Day.SUNDAY)).toBe(Day.SATURDAY);
+  });
+
+  it('should return the previous days if a negative value is input.', () => {
+    expect(getPreviousDay(Day.SATURDAY, -1)).toBe(Day.FRIDAY);
+    expect(getPreviousDay(Day.SUNDAY, -1)).toBe(Day.SATURDAY);
+  });
+
+  it('should return the previous days if a positive value is input.', () => {
+    expect(getPreviousDay(Day.SATURDAY, -1)).toBe(Day.FRIDAY);
+    expect(getPreviousDay(Day.SUNDAY, -1)).toBe(Day.SATURDAY);
+  });
+
+  it('should return the previous days for the number of days input.', () => {
+    expect(getPreviousDay(Day.SATURDAY, 5)).toBe(Day.MONDAY);
+  });
+});
+
+describe('getNextDay()', () => {
+  it('should return the next.', () => {
+    expect(getNextDay(Day.FRIDAY)).toBe(Day.SATURDAY);
+    expect(getNextDay(Day.SUNDAY)).toBe(Day.MONDAY);
+  });
+
+  it('should return the next days for the number of days input.', () => {
+    expect(getNextDay(Day.FRIDAY, 4)).toBe(Day.TUESDAY);
+  });
+});
diff --git a/packages/util/src/lib/date/week.ts b/packages/util/src/lib/date/week.ts
index 68ef82670..317d90c8a 100644
--- a/packages/util/src/lib/date/week.ts
+++ b/packages/util/src/lib/date/week.ts
@@ -23,3 +23,27 @@ export enum Day {
   FRIDAY = 5,
   SATURDAY = 6
 }
+
+export function getTomorrow(day: DayOfWeek): DayOfWeek {
+  return getNextDay(day, 1);
+}
+
+export function getDayOffset(day: DayOfWeek, days: number): DayOfWeek {
+  if (days === 0) {
+    return day;
+  } else if (days < 0) {
+    return getPreviousDay(day, days);
+  } else {
+    return getNextDay(day, days);
+  }
+}
+
+export function getPreviousDay(day: DayOfWeek, days: number = 1): DayOfWeek {
+  const offset = Math.abs(days) % 7;
+  const cap = 7 - offset;
+  return getNextDay(day, cap);
+}
+
+export function getNextDay(day: DayOfWeek, days: number = 1): DayOfWeek {
+  return Math.abs((day + days) % 7) as DayOfWeek;
+}