sendou.ink/app/utils/dates.ts

import { getWeek } from "date-fns";
import type { MonthYear } from "~/features/plus-voting/core";

// TODO: when this lands https://github.com/remix-run/remix/discussions/7768 we can get rid of this (utilizing Kysely plugin to do converting from/to Date for us)
export function databaseTimestampToDate(timestamp: number) {
	return new Date(timestamp * 1000);
}

export function dateToDatabaseTimestamp(date: Date) {
	return Math.floor(date.getTime() / 1000);
}

export function databaseTimestampNow() {
	return dateToDatabaseTimestamp(new Date());
}

export function databaseCreatedAt() {
	return dateToDatabaseTimestamp(new Date());
}

export function dateToWeekNumber(date: Date) {
	return getWeek(date, { weekStartsOn: 1, firstWeekContainsDate: 4 });
}

export function dateToThisWeeksMonday(date: Date) {
	const copiedDate = new Date(date.getTime());

	while (copiedDate.getDay() !== 1) {
		copiedDate.setDate(copiedDate.getDate() - 1);
	}

	return copiedDate;
}

export function getWeekStartsAtMondayDay(date: Date) {
	const currentDay = date.getDay();

	return dayToWeekStartsAtMondayDay(currentDay);
}

export function dayToWeekStartsAtMondayDay(day: number) {
	return day === 0 ? 7 : day;
}

// https://stackoverflow.com/a/71336659
export function weekNumberToDate({
	week,
	year,
	position = "start",
}: {
	week: number;
	year: number;
	/** start = Date of Monday, end = Date of Sunday */
	position?: "start" | "end";
}) {
	const result = new Date(Date.UTC(year, 0, 4));

	result.setDate(
		result.getDate() - (result.getDay() || 7) + 1 + 7 * (week - 1),
	);
	if (position === "end") {
		result.setDate(result.getDate() + 6);
	}
	return result;
}

/**
 * Checks if a date is valid or not.
 *
 * Returns:
 * - True if date is valid
 * - False otherwise
 */
export function isValidDate(date: Date) {
	return !Number.isNaN(date.getTime());
}

/** Returns date as a string with the format YYYY-MM-DDThh:mm in user's time zone */
export function dateToYearMonthDayHourMinuteString(date: Date) {
	const copiedDate = new Date(date.getTime());

	if (!isValidDate(copiedDate)) {
		throw new Error("tried to format string from invalid date");
	}

	const year = copiedDate.getFullYear();
	const month = copiedDate.getMonth() + 1;
	const day = copiedDate.getDate();
	const hour = copiedDate.getHours();
	const minute = copiedDate.getMinutes();

	return `${year}-${prefixZero(month)}-${prefixZero(day)}T${prefixZero(
		hour,
	)}:${prefixZero(minute)}`;
}

/** Returns date as a string with the format YYYY-MM-DD in user's time zone */
export function dateToYearMonthDayString(date: Date) {
	const copiedDate = new Date(date.getTime());

	if (!isValidDate(copiedDate)) {
		throw new Error("tried to format string from invalid date");
	}

	const year = copiedDate.getFullYear();
	const month = copiedDate.getMonth() + 1;
	const day = copiedDate.getDate();

	return `${year}-${prefixZero(month)}-${prefixZero(day)}`;
}

function prefixZero(number: number) {
	return number < 10 ? `0${number}` : number;
}

/**
 * Retrieves a new Date object that is offset by several hours.
 *
 * NOTE: it is important that we work with & return a copy of the date here,
 *  otherwise we will just be mutating the original date passed into this function.
 */
export function getDateWithHoursOffset(date: Date, hoursOffset: number) {
	const copiedDate = new Date(date.getTime());
	copiedDate.setHours(date.getHours() + hoursOffset);
	return copiedDate;
}

export function getDateAtNextFullHour(date: Date) {
	const copiedDate = new Date(date.getTime());
	if (date.getMinutes() > 0) {
		copiedDate.setHours(date.getHours() + 1);
		copiedDate.setMinutes(0);
	}
	copiedDate.setSeconds(0);
	return copiedDate;
}

export function dateToYYYYMMDD(date: Date) {
	return date.toISOString().split("T")[0];
}

// same as datesOfMonth but contains null at the start to start with monday
export function nullPaddedDatesOfMonth({ month, year }: MonthYear) {
	const dates = datesOfMonth({ month, year });
	const firstDay = dates[0].getDay();
	const nulls = Array.from(
		{ length: firstDay === 0 ? 6 : firstDay - 1 },
		() => null,
	);
	return [...nulls, ...dates];
}

function datesOfMonth({ month, year }: MonthYear) {
	const dates = [];
	const date = new Date(Date.UTC(year, month, 1));
	while (date.getMonth() === month) {
		dates.push(new Date(date));
		date.setDate(date.getDate() + 1);
	}
	return dates;
}