workavia-calendar-front/src/utils/dateUtils.ts

import moment from "moment";

export function formatDateToYYYYMMDDTHHMMSS(date: Date) {
  return moment(date).format("YYYYMMDDTHHmmss");
}

export function getCalendarRange(date = new Date()) {
  const year = date.getFullYear();
  const month = date.getMonth();

  const firstOfMonth = new Date(year, month, 1);
  const dayOfWeekStart = firstOfMonth.getDay();
  const diffToMonday = (dayOfWeekStart + 6) % 7;
  const startDate = new Date(firstOfMonth);
  startDate.setDate(firstOfMonth.getDate() - diffToMonday);
  startDate.setHours(0, 0, 0, 0);

  const lastOfMonth = new Date(year, month + 1, 0);

  // Calculate how many days from startDate to lastOfMonth
  const daysFromStart = Math.floor(
    (lastOfMonth.getTime() - startDate.getTime()) / (1000 * 60 * 60 * 24)
  );

  // Calculate number of weeks needed to cover all days (round up)
  const weeksNeeded = Math.ceil((daysFromStart + 1) / 7);

  // endDate is the Sunday of the last week (startDate + weeks * 7 - 1)
  const endDate = new Date(startDate);
  endDate.setDate(startDate.getDate() + weeksNeeded * 7 - 1);
  endDate.setHours(23, 59, 59, 999);

  return {
    start: startDate,
    end: endDate,
  };
}

export function getDeltaInMilliseconds(delta: {
  years: number;
  months: number;
  days: number;
  milliseconds: number;
}) {
  const MS_PER_DAY = 24 * 60 * 60 * 1000;
  const AVG_MS_PER_MONTH = 30.44 * MS_PER_DAY; // approx
  const AVG_MS_PER_YEAR = 365.25 * MS_PER_DAY; // approx

  return (
    (delta.years || 0) * AVG_MS_PER_YEAR +
    (delta.months || 0) * AVG_MS_PER_MONTH +
    (delta.days || 0) * MS_PER_DAY +
    (delta.milliseconds || 0)
  );
}

export const computeStartOfTheWeek = (date: Date): Date => {
  const startOfWeek = new Date(date);
  startOfWeek.setDate(date.getDate() - ((date.getDay() + 6) % 7)); // Monday
  startOfWeek.setHours(0, 0, 0, 0);
  return startOfWeek;
};

export const computeWeekRange = (date: Date): { start: Date; end: Date } => {
  const weekStart = computeStartOfTheWeek(date);
  const weekEnd = new Date(weekStart);
  weekEnd.setDate(weekStart.getDate() + 7);
  return { start: weekStart, end: weekEnd };
};