/*
 * Portions of this file are based on code from react-spectrum.
 * Apache License Version 2.0, Copyright 2020 Adobe.
 *
 * Credits to the React Spectrum team:
 * https://github.com/adobe/react-spectrum/blob/b35d5c02fe900badccd0cf1a8f23bb593419f238/packages/@react-aria/i18n/src/utils.ts
 */

export type Direction = "rtl" | "ltr";

// https://en.wikipedia.org/wiki/Right-to-left
const RTL_SCRIPTS = new Set([
	"Avst",
	"Arab",
	"Armi",
	"Syrc",
	"Samr",
	"Mand",
	"Thaa",
	"Mend",
	"Nkoo",
	"Adlm",
	"Rohg",
	"Hebr",
]);

export const RTL_LANGS = new Set([
	"ae",
	"ar",
	"arc",
	"bcc",
	"bqi",
	"ckb",
	"dv",
	"fa",
	"glk",
	"he",
	"ku",
	"mzn",
	"nqo",
	"pnb",
	"ps",
	"sd",
	"ug",
	"ur",
	"yi",
]);

/**
 * Determines if a locale is read right to left using [Intl.Locale]
 * {@link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/Locale}.
 */
export function isRTL(locale: string) {
	// If the Intl.Locale API is available, use it to get the script for the locale.
	// This is more accurate than guessing by language, since languages can be written in multiple scripts.
	if (Intl.Locale) {
		const script = new Intl.Locale(locale).maximize().script ?? "";

		return RTL_SCRIPTS.has(script);
	}

	// If not, just guess by the language (first part of the locale)
	const lang = locale.split("-")[0];
	return RTL_LANGS.has(lang);
}

export function getReadingDirection(locale: string): Direction {
	return isRTL(locale) ? "rtl" : "ltr";
}