package geo

import "strings"

// countryToLanguage maps an uppercase ISO 3166-1 alpha-2 country code to
// an ISO 639-1 lowercase language code. The set is intentionally minimal
// — covering the top-traffic Galaxy locales — and is consulted as a
// fallback when neither the request body nor the Accept-Language header
// supplied a locale at send-email-code. Unknown countries map to the
// empty string so the auth flow can default to "en".
//
// The mapping is intentionally hard-coded rather than derived from the
// GeoLite2 database: countries with multiple official languages collapse
// to the single most common UI locale to keep the registration path
// deterministic. The implementation may revise this table without changing the
// surface auth depends on.
var countryToLanguage = map[string]string{
	// English-default territories and the platform fallback.
	"US": "en", "GB": "en", "AU": "en", "NZ": "en", "IE": "en", "CA": "en",
	// Western Europe.
	"DE": "de", "AT": "de", "CH": "de",
	"FR": "fr", "BE": "fr", "LU": "fr",
	"ES": "es", "MX": "es", "AR": "es", "CL": "es", "CO": "es",
	"IT": "it",
	"PT": "pt", "BR": "pt",
	"NL": "nl",
	// Central / Eastern Europe.
	"PL": "pl",
	"RU": "ru", "BY": "ru", "KZ": "ru",
	"UA": "uk",
	"CZ": "cs",
	"SK": "sk",
	"HU": "hu",
	"RO": "ro",
	"BG": "bg",
	// Northern Europe.
	"SE": "sv",
	"NO": "no",
	"DK": "da",
	"FI": "fi",
	// Asia.
	"JP": "ja",
	"KR": "ko",
	"CN": "zh", "TW": "zh", "HK": "zh", "SG": "zh",
	"VN": "vi",
	"TH": "th",
	"ID": "id",
	"IN": "en",
	"IL": "he",
	"TR": "tr",
	// Middle East and North Africa.
	"SA": "ar", "AE": "ar", "EG": "ar",
}

// languageForCountry returns the ISO 639-1 language code mapped to
// country, or "" when no mapping is known. country is normalised to
// uppercase before lookup.
func languageForCountry(country string) string {
	if country == "" {
		return ""
	}
	return countryToLanguage[strings.ToUpper(strings.TrimSpace(country))]
}