import { calendarDate } from "./calendar.schema";

function isValidPeriod(from: null | string, to: null | string) {
	return (
		[from, to].every(
			date => date === null || calendarDate.safeParse(date).success,
		)
		&& (!from || !to || from <= to)
	);
}

const DEFAULT_PERIOD_LAST_INDEX = 6;

const moscowFormatter = new Intl.DateTimeFormat("en-CA", {
	day: "2-digit",
	month: "2-digit",
	timeZone: "Europe/Moscow",
	year: "numeric",
});

// Newest first. Missing dates sort last in both directions, so a row without a
// date never jumps to the top of a "past" list.
function compareDateDesc(a: null | string, b: null | string) {
	return (b ?? "").localeCompare(a ?? "");
}

// 7 calendar dates starting with today (Moscow calendar arithmetic).
function defaultPeriod(): [string, string] {
	const from = moscowDate(new Date());

	const [year = 1970, month = 0, day = 1] = from.split("-").map(Number);
	const noon = 12;
	const lastDay = day + DEFAULT_PERIOD_LAST_INDEX;
	const end = new Date(Date.UTC(year, month - 1, lastDay, noon));
	const to = moscowDate(end);

	return [from, to];
}

function moscowDate(value: Date): string {
	const parts = moscowFormatter.formatToParts(value);

	const part = (type: string) =>
		parts.find(item => item.type === type)?.value;

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

export { compareDateDesc, defaultPeriod, isValidPeriod, moscowDate };