BCP47LanguageCodeForString.m

static NSString * BCP47LanguageCodeFromISO681LanguageCode(NSString *ISO681LanguageCode) {
    if ([ISO681LanguageCode isEqualToString:@"ar"]) {
        return @"ar-SA";
    } else if ([ISO681LanguageCode hasPrefix:@"cs"]) {
        return @"cs-CZ";
    } else if ([ISO681LanguageCode hasPrefix:@"da"]) {
        return @"da-DK";
    } else if ([ISO681LanguageCode hasPrefix:@"de"]) {
        return @"de-DE";
    } else if ([ISO681LanguageCode hasPrefix:@"el"]) {
        return @"el-GR";
    } else if ([ISO681LanguageCode hasPrefix:@"en"]) {
        return @"en-US"; // en-AU, en-GB, en-IE, en-ZA
    } else if ([ISO681LanguageCode hasPrefix:@"es"]) {
        return @"es-ES"; // es-MX
    } else if ([ISO681LanguageCode hasPrefix:@"fi"]) {
        return @"fi-FI";
    } else if ([ISO681LanguageCode hasPrefix:@"fr"]) {
        return @"fr-FR"; // fr-CA
    } else if ([ISO681LanguageCode hasPrefix:@"hi"]) {
        return @"hi-IN";
    } else if ([ISO681LanguageCode hasPrefix:@"hu"]) {
        return @"hu-HU";
    } else if ([ISO681LanguageCode hasPrefix:@"id"]) {
        return @"id-ID";
    } else if ([ISO681LanguageCode hasPrefix:@"it"]) {
        return @"it-IT";
    } else if ([ISO681LanguageCode hasPrefix:@"ja"]) {
        return @"ja-JP";
    } else if ([ISO681LanguageCode hasPrefix:@"ko"]) {
        return @"ko-KR";
    } else if ([ISO681LanguageCode hasPrefix:@"nl"]) {
        return @"nl-NL"; // nl-BE
    } else if ([ISO681LanguageCode hasPrefix:@"no"]) {
        return @"no-NO";
    } else if ([ISO681LanguageCode hasPrefix:@"pl"]) {
        return @"pl-PL";
    } else if ([ISO681LanguageCode hasPrefix:@"pt"]) {
        return @"pt-BR"; // pt-PT
    } else if ([ISO681LanguageCode hasPrefix:@"ro"]) {
        return @"ro-RO";
    } else if ([ISO681LanguageCode hasPrefix:@"ru"]) {
        return @"ru-RU";
    } else if ([ISO681LanguageCode hasPrefix:@"sk"]) {
        return @"sk-SK";
    } else if ([ISO681LanguageCode hasPrefix:@"sv"]) {
        return @"sv-SE";
    } else if ([ISO681LanguageCode hasPrefix:@"th"]) {
        return @"th-TH";
    } else if ([ISO681LanguageCode hasPrefix:@"tr"]) {
        return @"tr-TR";
    } else if ([ISO681LanguageCode hasPrefix:@"zh"]) {
        return @"zh-CN"; // zh-HK, zh-TW
    } else {
        return nil;
    }
}

static NSString * BCP47LanguageCodeForString(NSString *string) {
    NSString *ISO681LanguageCode = (__bridge NSString *)CFStringTokenizerCopyBestStringLanguage((__bridge CFStringRef)string, CFRangeMake(0, [string length]));
    return BCP47LanguageCodeFromISO681LanguageCode(ISO681LanguageCode);
}