website/scripts/spotters-countries.ts

// Country name (as found in Wikidata labels, OpenSky, the train/plane/car data) -> lowercase
// ISO 3166-1 alpha-2 code, for scripts/spotters-activity.ts. Historic states map to their
// main successor (Deutsches Reich -> de, Soviet Union -> ru, Yugoslavia -> rs).

const ALIASES: Record<string, string> = {
	'united states of america': 'us',
	usa: 'us',
	'u.s.': 'us',
	'united states': 'us',
	"people's republic of china": 'cn',
	'republic of china': 'tw',
	'taiwan (republic of china)': 'tw',
	'taiwan under japanese rule': 'tw',
	manchukuo: 'cn',
	'hong kong': 'hk',
	macau: 'mo',
	macao: 'mo',
	'russian federation': 'ru',
	'soviet union': 'ru',
	ussr: 'ru',
	'soviet union (russia since 1991)': 'ru',
	'russian empire': 'ru',
	'russian sfsr': 'ru',
	'deutsches reich': 'de',
	'german reich': 'de',
	'german empire': 'de',
	'nazi germany': 'de',
	'east germany': 'de',
	'west germany': 'de',
	'weimar republic': 'de',
	'weimarer republik': 'de',
	'deutsches kaiserreich': 'de',
	'allied-occupied germany': 'de',
	'grand duchy of baden': 'de',
	'territory of the saar basin': 'de',
	'saar protectorate': 'de',
	'kingdom of bavaria': 'de',
	'kingdom of prussia': 'de',
	'kingdom of saxony': 'de',
	'kingdom of württemberg': 'de',
	'german reich (nazi period) deutsches reich': 'de',
	germa: 'de',
	czechoslovakia: 'cz',
	'first czechoslovak republic': 'cz',
	'czech republic': 'cz',
	'protectorate of bohemia and moravia': 'cz',
	'czechoslovak socialist republic': 'cz',
	'korea under japanese rule': 'kr',
	'korean empire': 'kr',
	'south korea': 'kr',
	'north korea': 'kp',
	'republic of korea': 'kr',
	"democratic people's republic of korea": 'kp',
	'irish free state': 'ie',
	'republic of ireland': 'ie',
	yugoslavia: 'rs',
	'kingdom of yugoslavia': 'rs',
	'socialist federal republic of yugoslavia': 'rs',
	'federal republic of yugoslavia': 'rs',
	'serbia and montenegro': 'rs',
	'empire of japan': 'jp',
	'kingdom of italy': 'it',
	'austria–hungary': 'at',
	'austria-hungary': 'at',
	cisleithania: 'at',
	'first republic of austria': 'at',
	'austrian empire': 'at',
	'colony of natal': 'za',
	'south african republic': 'za',
	'orange free state': 'za',
	'cape colony': 'za',
	'union of south africa': 'za',
	'dutch east indies': 'id',
	'kingdom of the netherlands': 'nl',
	netherlands: 'nl',
	holland: 'nl',
	england: 'gb',
	scotland: 'gb',
	wales: 'gb',
	'northern ireland': 'gb',
	'great britain': 'gb',
	'united kingdom of great britain and ireland': 'gb',
	'united kingdom': 'gb',
	uk: 'gb',
	tanganyika: 'tz',
	'mandatory palestine': 'il',
	'second polish republic': 'pl',
	"polish people's republic": 'pl',
	'polska rzeczpospolita ludowa': 'pl',
	'second spanish republic': 'es',
	'francoist spain': 'es',
	'kingdom of romania': 'ro',
	"ukrainian people's republic": 'ua',
	'ukrainian ssr': 'ua',
	turkey: 'tr',
	türkiye: 'tr',
	'ottoman empire': 'tr',
	'kingdom of hungary': 'hu',
	'kingdom of greece': 'gr',
	'kingdom of bulgaria': 'bg',
	'british raj': 'in',
	'dominion of india': 'in',
	ceylon: 'lk',
	burma: 'mm',
	'french third republic': 'fr',
	'vichy france': 'fr',
	'french fourth republic': 'fr',
	'kingdom of egypt': 'eg',
	rhodesia: 'zw',
	'southern rhodesia': 'zw',
	'northern rhodesia': 'zm',
	'belgian congo': 'cd',
	zaire: 'cd',
	swaziland: 'sz',
	eswatini: 'sz',
	persia: 'ir',
	iran: 'ir',
	syria: 'sy',
	vietnam: 'vn',
	laos: 'la',
	bolivia: 'bo',
	venezuela: 've',
	tanzania: 'tz',
	moldova: 'md',
	macedonia: 'mk',
	'north macedonia': 'mk',
	'bosnia and herzegovina': 'ba',
	'ivory coast': 'ci',
	"côte d'ivoire": 'ci',
	'cape verde': 'cv',
	'east timor': 'tl',
	kosovo: 'xk',
	'isle of man': 'im',
	jersey: 'je',
	guernsey: 'gg',
	'state of palestine': 'ps',
	brunei: 'bn',
	'republic of the congo': 'cg',
	'democratic republic of the congo': 'cd',
	'the gambia': 'gm',
	'the bahamas': 'bs',
	'federated states of micronesia': 'fm',
	'vatican city': 'va',
	czechia: 'cz'
};

let byName: Map<string, string> | null = null;

function table() {
	if (byName) return byName;
	byName = new Map();
	const dn = new Intl.DisplayNames(['en'], { type: 'region' });
	for (let a = 65; a <= 90; a++)
		for (let b = 65; b <= 90; b++) {
			const code = String.fromCharCode(a, b);
			try {
				const name = dn.of(code);
				if (name && name !== code) byName.set(name.toLowerCase(), code.toLowerCase());
			} catch {
				/* not a region */
			}
		}
	for (const [k, v] of Object.entries(ALIASES)) byName.set(k, v);
	return byName;
}

/** Country label -> ISO2 (lowercase), or null when unknown / multinational. */
export function countryCode(name: string | null | undefined): string | null {
	if (!name) return null;
	const key = name.trim().toLowerCase().replace(/\s+/g, ' ');
	return table().get(key) ?? table().get(key.replace(/^the /, '')) ?? null;
}