iceshrimp/packages/client/src/scripts/format-time-string.ts

const defaultLocaleStringFormats: { [index: string]: string } = {
	weekday: "narrow",
	era: "narrow",
	year: "numeric",
	month: "numeric",
	day: "numeric",
	hour: "numeric",
	minute: "numeric",
	second: "numeric",
	timeZoneName: "short",
};

function formatLocaleString(date: Date, format: string): string {
	return format.replace(
		/\{\{(\w+)(:(\w+))?\}\}/g,
		(match: string, kind: string, unused?, option?: string) => {
			if (
				[
					"weekday",
					"era",
					"year",
					"month",
					"day",
					"hour",
					"minute",
					"second",
					"timeZoneName",
				].includes(kind)
			) {
				return date.toLocaleString(window.navigator.language, {
					[kind]: option ? option : defaultLocaleStringFormats[kind],
				});
			} else {
				return match;
			}
		},
	);
}

export function formatDateTimeString(date: Date, format: string): string {
	return format
		.replace(/yyyy/g, date.getFullYear().toString())
		.replace(/yy/g, date.getFullYear().toString().slice(-2))
		.replace(
			/MMMM/g,
			date.toLocaleString(window.navigator.language, { month: "long" }),
		)
		.replace(
			/MMM/g,
			date.toLocaleString(window.navigator.language, { month: "short" }),
		)
		.replace(/MM/g, `0${date.getMonth() + 1}`.slice(-2))
		.replace(/M/g, (date.getMonth() + 1).toString())
		.replace(/dd/g, `0${date.getDate()}`.slice(-2))
		.replace(/d/g, date.getDate().toString())
		.replace(/HH/g, `0${date.getHours()}`.slice(-2))
		.replace(/H/g, date.getHours().toString())
		.replace(/hh/g, `0${date.getHours() % 12 || 12}`.slice(-2))
		.replace(/h/g, (date.getHours() % 12 || 12).toString())
		.replace(/mm/g, `0${date.getMinutes()}`.slice(-2))
		.replace(/m/g, date.getMinutes().toString())
		.replace(/ss/g, `0${date.getSeconds()}`.slice(-2))
		.replace(/s/g, date.getSeconds().toString())
		.replace(/tt/g, date.getHours() >= 12 ? "PM" : "AM");
}

export function formatTimeString(date: Date, format: string): string {
	return format.replace(
		/\[(([^\[]|\[\])*)\]|(([yMdHhmst])\4{0,3})/g,
		(
			match: string,
			localeformat?: string,
			unused?,
			datetimeformat?: string,
		) => {
			if (localeformat) return formatLocaleString(date, localeformat);
			if (datetimeformat) return formatDateTimeString(date, datetimeformat);
			return match;
		},
	);
}