week numbers

nextjs/src/app/course/[courseName]/calendar/CalendarMonth.tsx

@@ -1,8 +1,10 @@
 "use client";
-import { CalendarMonthModel } from "./calendarMonthUtils";
+import { CalendarMonthModel, getWeekNumber } from "./calendarMonthUtils";
 import { DayOfWeek } from "@/models/local/localCourse";
 import Day from "./day/Day";
 import { Expandable } from "@/components/Expandable";
+import { useLocalCourseSettingsQuery } from "@/hooks/localCourse/localCoursesHooks";
+import { getDateFromStringOrThrow } from "@/models/local/timeUtils";
 
 export const CalendarMonth = ({ month }: { month: CalendarMonthModel }) => {
   const weekInMilliseconds = 604_800_000;
@@ -35,7 +37,7 @@ export const CalendarMonth = ({ month }: { month: CalendarMonthModel }) => {
           </div>
         )}
       >
-        <div className="grid grid-cols-7 text-center fw-bold">
+        <div className="grid grid-cols-7 text-center fw-bold ms-3">
           {weekDaysList.map((day) => (
             <div key={day} className={""}>
               {day}
@@ -58,11 +60,26 @@ function CalendarWeek({
   week: string[]; //date strings
   monthNumber: number;
 }) {
+  const { data: settings } = useLocalCourseSettingsQuery();
+  const startDate = getDateFromStringOrThrow(
+    settings.startDate,
+    "week calculation start date"
+  );
+  const firstDateString = getDateFromStringOrThrow(
+    week[0],
+    "week calculation first day of week"
+  );
+  const weekNumber = getWeekNumber(startDate, firstDateString);
   return (
-    <div className="grid grid-cols-7">
+    <div className="flex flex-row">
+      <div className="my-auto text-gray-400">
+        {weekNumber.toString().padStart(2, "0")}
+      </div>
+      <div className="grid grid-cols-7 grow">
         {week.map((day, dayIndex) => (
           <Day key={dayIndex} day={day} month={monthNumber} />
         ))}
       </div>
+    </div>
   );
 }

nextjs/src/app/course/[courseName]/calendar/calendarMonthUtils.ts

@@ -37,7 +37,9 @@ function createCalendarMonth(year: number, month: number): CalendarMonthModel {
           new Date(year, month - 1, dayIndex - firstDayOfMonth + 1, 12, 0, 0)
         );
       } else if (currentDay <= daysInMonth) {
-        return dateToMarkdownString(new Date(year, month - 1, currentDay++, 12, 0, 0));
+        return dateToMarkdownString(
+          new Date(year, month - 1, currentDay++, 12, 0, 0)
+        );
       } else {
         currentDay++;
         return dateToMarkdownString(
@@ -74,3 +76,27 @@ export function getMonthsBetweenDates(
     return createCalendarMonth(year, month);
   });
 }
+
+export const getWeekNumber = (startDate: Date, currentDate: Date) => {
+  const sundayBeforeStartDate = getPreviousSunday(startDate);
+  const daysBetween = daysBetweenDates(sundayBeforeStartDate, currentDate);
+  const weeksDiff = Math.floor(daysBetween / 7);
+
+  if (weeksDiff >= 0) return weeksDiff + 1;
+  return weeksDiff;
+};
+
+const daysBetweenDates = (startDate: Date, endDate: Date) => {
+  const diffInTime = endDate.getTime() - startDate.getTime();
+  const diffInDays = diffInTime / (1000 * 3600 * 24);
+  return Math.floor(diffInDays);
+};
+
+const getPreviousSunday = (date: Date) => {
+  const result = new Date(date);
+  const dayOfWeek = result.getDay();
+
+  result.setDate(result.getDate() - dayOfWeek);
+
+  return result;
+};

nextjs/src/app/course/[courseName]/calendar/calendarUtils.test.ts

@@ -0,0 +1,47 @@
+import { describe, expect, it } from "vitest";
+import { getWeekNumber } from "./calendarMonthUtils";
+
+
+// months are 0 based, days are 1 based
+describe("testing week numbers", () => {
+
+  it("can get before first day", () => {
+    const startDate = new Date(2024, 8, 3);
+    const firstDayOfFirstWeek = new Date(2024, 8, 1);
+
+    const weekNumber = getWeekNumber(startDate, firstDayOfFirstWeek);
+    expect(weekNumber).toBe(1);
+  });
+
+  it("can get end of first week", () => {
+    const startDate = new Date(2024, 8, 3);
+    const firstDayOfFirstWeek = new Date(2024, 8, 7);
+
+    const weekNumber = getWeekNumber(startDate, firstDayOfFirstWeek);
+    expect(weekNumber).toBe(1);
+  });
+
+  it("can get start of second week", () => {
+    const startDate = new Date(2024, 8, 3);
+    const firstDayOfFirstWeek = new Date(2024, 8, 8);
+
+    const weekNumber = getWeekNumber(startDate, firstDayOfFirstWeek);
+    expect(weekNumber).toBe(2);
+  });
+
+  it("can get start of third week", () => {
+    const startDate = new Date(2024, 8, 3);
+    const firstDayOfFirstWeek = new Date(2024, 8, 15);
+
+    const weekNumber = getWeekNumber(startDate, firstDayOfFirstWeek);
+    expect(weekNumber).toBe(3);
+  });
+  it("can get previous week", () => {
+    const startDate = new Date(2024, 8, 3);
+    const firstDayOfFirstWeek = new Date(2024, 7, 29);
+
+    const weekNumber = getWeekNumber(startDate, firstDayOfFirstWeek);
+    expect(weekNumber).toBe(-1);
+  });
+
+});