/*
 * Hunt - A refined core library for D programming language.
 *
 * Copyright (C) 2018-2019 HuntLabs
 *
 * Website: https://www.huntlabs.net/
 *
 * Licensed under the Apache-2.0 License.
 *
 */

module hunt.util.Locale;

import hunt.Exceptions;
import hunt.Functions;
import hunt.stream.Common;
import hunt.logging.ConsoleLogger;
import hunt.collection;
import hunt.system.Environment;
import hunt.util.StringBuilder;
import hunt.util.Common;
import hunt.util.Configuration;

import std.array;
import std.concurrency : initOnce;
import std.string;

/**
 * A <code>Locale</code> object represents a specific geographical, political,
 * or cultural region. An operation that requires a <code>Locale</code> to perform
 * its task is called <em>locale-sensitive</em> and uses the <code>Locale</code>
 * to tailor information for the user. For example, displaying a number
 * is a locale-sensitive operation&mdash; the number should be formatted
 * according to the customs and conventions of the user's native country,
 * region, or culture.
 *
 * <p> The {@code Locale} class implements IETF BCP 47 which is composed of
 * <a href="http://tools.ietf.org/html/rfc4647">RFC 4647 "Matching of Language
 * Tags"</a> and <a href="http://tools.ietf.org/html/rfc5646">RFC 5646 "Tags
 * for Identifying Languages"</a> with support for the LDML (UTS#35, "Unicode
 * Locale Data Markup Language") BCP 47-compatible extensions for locale data
 * exchange.
 *
 * <p> A <code>Locale</code> object logically consists of the fields
 * described below.
 *
 * <dl>
 *   <dt><a id="def_language"><b>language</b></a></dt>
 *
 *   <dd>ISO 639 alpha-2 or alpha-3 language code, or registered
 *   language subtags up to 8 alpha letters (for future enhancements).
 *   When a language has both an alpha-2 code and an alpha-3 code, the
 *   alpha-2 code must be used.  You can find a full list of valid
 *   language codes in the IANA Language Subtag Registry (search for
 *   "Type: language").  The language field is case insensitive, but
 *   <code>Locale</code> always canonicalizes to lower case.</dd>
 *
 *   <dd>Well-formed language values have the form
 *   <code>[a-zA-Z]{2,8}</code>.  Note that this is not the full
 *   BCP47 language production, since it excludes extlang.  They are
 *   not needed since modern three-letter language codes replace
 *   them.</dd>
 *
 *   <dd>Example: "en" (English), "ja" (Japanese), "kok" (Konkani)</dd>
 *
 *   <dt><a id="def_script"><b>script</b></a></dt>
 *
 *   <dd>ISO 15924 alpha-4 script code.  You can find a full list of
 *   valid script codes in the IANA Language Subtag Registry (search
 *   for "Type: script").  The script field is case insensitive, but
 *   <code>Locale</code> always canonicalizes to title case (the first
 *   letter is upper case and the rest of the letters are lower
 *   case).</dd>
 *
 *   <dd>Well-formed script values have the form
 *   <code>[a-zA-Z]{4}</code></dd>
 *
 *   <dd>Example: "Latn" (Latin), "Cyrl" (Cyrillic)</dd>
 *
 *   <dt><a id="def_region"><b>country (region)</b></a></dt>
 *
 *   <dd>ISO 3166 alpha-2 country code or UN M.49 numeric-3 area code.
 *   You can find a full list of valid country and region codes in the
 *   IANA Language Subtag Registry (search for "Type: region").  The
 *   country (region) field is case insensitive, but
 *   <code>Locale</code> always canonicalizes to upper case.</dd>
 *
 *   <dd>Well-formed country/region values have
 *   the form <code>[a-zA-Z]{2} | [0-9]{3}</code></dd>
 *
 *   <dd>Example: "US" (United States), "FR" (France), "029"
 *   (Caribbean)</dd>
 *
 *   <dt><a id="def_variant"><b>variant</b></a></dt>
 *
 *   <dd>Any arbitrary value used to indicate a variation of a
 *   <code>Locale</code>.  Where there are two or more variant values
 *   each indicating its own semantics, these values should be ordered
 *   by importance, with most important first, separated by
 *   underscore('_').  The variant field is case sensitive.</dd>
 *
 *   <dd>Note: IETF BCP 47 places syntactic restrictions on variant
 *   subtags.  Also BCP 47 subtags are strictly used to indicate
 *   additional variations that define a language or its dialects that
 *   are not covered by any combinations of language, script and
 *   region subtags.  You can find a full list of valid variant codes
 *   in the IANA Language Subtag Registry (search for "Type: variant").
 *
 *   <p>However, the variant field in <code>Locale</code> has
 *   historically been used for any kind of variation, not just
 *   language variations.  For example, some supported variants
 *   available in Java SE Runtime Environments indicate alternative
 *   cultural behaviors such as calendar type or number script.  In
 *   BCP 47 this kind of information, which does not identify the
 *   language, is supported by extension subtags or private use
 *   subtags.</dd>
 *
 *   <dd>Well-formed variant values have the form <code>SUBTAG
 *   (('_'|'-') SUBTAG)*</code> where <code>SUBTAG =
 *   [0-9][0-9a-zA-Z]{3} | [0-9a-zA-Z]{5,8}</code>. (Note: BCP 47 only
 *   uses hyphen ('-') as a delimiter, this is more lenient).</dd>
 *
 *   <dd>Example: "polyton" (Polytonic Greek), "POSIX"</dd>
 *
 *   <dt><a id="def_extensions"><b>extensions</b></a></dt>
 *
 *   <dd>A map from single character keys to string values, indicating
 *   extensions apart from language identification.  The extensions in
 *   <code>Locale</code> implement the semantics and syntax of BCP 47
 *   extension subtags and private use subtags. The extensions are
 *   case insensitive, but <code>Locale</code> canonicalizes all
 *   extension keys and values to lower case. Note that extensions
 *   cannot have empty values.</dd>
 *
 *   <dd>Well-formed keys are single characters from the set
 *   <code>[0-9a-zA-Z]</code>.  Well-formed values have the form
 *   <code>SUBTAG ('-' SUBTAG)*</code> where for the key 'x'
 *   <code>SUBTAG = [0-9a-zA-Z]{1,8}</code> and for other keys
 *   <code>SUBTAG = [0-9a-zA-Z]{2,8}</code> (that is, 'x' allows
 *   single-character subtags).</dd>
 *
 *   <dd>Example: key="u"/value="ca-japanese" (Japanese Calendar),
 *   key="x"/value="java-1-7"</dd>
 * </dl>
 *
 * <b>Note:</b> Although BCP 47 requires field values to be registered
 * in the IANA Language Subtag Registry, the <code>Locale</code> class
 * does not provide any validation features.  The <code>Builder</code>
 * only checks if an individual field satisfies the syntactic
 * requirement (is well-formed), but does not validate the value
 * itself.  See {@link Builder} for details.
 *
 * <h3><a id="def_locale_extension">Unicode locale/language extension</a></h3>
 *
 * <p>UTS#35, "Unicode Locale Data Markup Language" defines optional
 * attributes and keywords to override or refine the default behavior
 * associated with a locale.  A keyword is represented by a pair of
 * key and type.  For example, "nu-thai" indicates that Thai local
 * digits (value:"thai") should be used for formatting numbers
 * (key:"nu").
 *
 * <p>The keywords are mapped to a BCP 47 extension value using the
 * extension key 'u' ({@link #UNICODE_LOCALE_EXTENSION}).  The above
 * example, "nu-thai", becomes the extension "u-nu-thai".
 *
 * <p>Thus, when a <code>Locale</code> object contains Unicode locale
 * attributes and keywords,
 * <code>getExtension(UNICODE_LOCALE_EXTENSION)</code> will return a
 * string representing this information, for example, "nu-thai".  The
 * <code>Locale</code> class also provides {@link
 * #getUnicodeLocaleAttributes}, {@link #getUnicodeLocaleKeys}, and
 * {@link #getUnicodeLocaleType} which allow you to access Unicode
 * locale attributes and key/type pairs directly.  When represented as
 * a string, the Unicode Locale Extension lists attributes
 * alphabetically, followed by key/type sequences with keys listed
 * alphabetically (the order of subtags comprising a key's type is
 * fixed when the type is defined)
 *
 * <p>A well-formed locale key has the form
 * <code>[0-9a-zA-Z]{2}</code>.  A well-formed locale type has the
 * form <code>"" | [0-9a-zA-Z]{3,8} ('-' [0-9a-zA-Z]{3,8})*</code> (it
 * can be empty, or a series of subtags 3-8 alphanums in length).  A
 * well-formed locale attribute has the form
 * <code>[0-9a-zA-Z]{3,8}</code> (it is a single subtag with the same
 * form as a locale type subtag).
 *
 * <p>The Unicode locale extension specifies optional behavior in
 * locale-sensitive services.  Although the LDML specification defines
 * various keys and values, actual locale-sensitive service
 * implementations in a Java Runtime Environment might not support any
 * particular Unicode locale attributes or key/type pairs.
 *
 * <h4>Creating a Locale</h4>
 *
 * <p>There are several different ways to create a <code>Locale</code>
 * object.
 *
 * <h5>Builder</h5>
 *
 * <p>Using {@link Builder} you can construct a <code>Locale</code> object
 * that conforms to BCP 47 syntax.
 *
 * <h5>Constructors</h5>
 *
 * <p>The <code>Locale</code> class provides three constructors:
 * <blockquote>
 * <pre>
 *     {@link #Locale(string language)}
 *     {@link #Locale(string language, string country)}
 *     {@link #Locale(string language, string country, string variant)}
 * </pre>
 * </blockquote>
 * These constructors allow you to create a <code>Locale</code> object
 * with language, country and variant, but you cannot specify
 * script or extensions.
 *
 * <h5>Factory Methods</h5>
 *
 * <p>The method {@link #forLanguageTag} creates a <code>Locale</code>
 * object for a well-formed BCP 47 language tag.
 *
 * <h5>Locale Constants</h5>
 *
 * <p>The <code>Locale</code> class provides a number of convenient constants
 * that you can use to create <code>Locale</code> objects for commonly used
 * locales. For example, the following creates a <code>Locale</code> object
 * for the United States:
 * <blockquote>
 * <pre>
 *     Locale.US
 * </pre>
 * </blockquote>
 *
 * <h4><a id="LocaleMatching">Locale Matching</a></h4>
 *
 * <p>If an application or a system is internationalized and provides localized
 * resources for multiple locales, it sometimes needs to find one or more
 * locales (or language tags) which meet each user's specific preferences. Note
 * that a term "language tag" is used interchangeably with "locale" in this
 * locale matching documentation.
 *
 * <p>In order to do matching a user's preferred locales to a set of language
 * tags, <a href="http://tools.ietf.org/html/rfc4647">RFC 4647 Matching of
 * Language Tags</a> defines two mechanisms: filtering and lookup.
 * <em>Filtering</em> is used to get all matching locales, whereas
 * <em>lookup</em> is to choose the best matching locale.
 * Matching is done case-insensitively. These matching mechanisms are described
 * in the following sections.
 *
 * <p>A user's preference is called a <em>Language Priority List</em> and is
 * expressed as a list of language ranges. There are syntactically two types of
 * language ranges: basic and extended. See
 * {@link Locale.LanguageRange Locale.LanguageRange} for details.
 *
 * <h5>Filtering</h5>
 *
 * <p>The filtering operation returns all matching language tags. It is defined
 * in RFC 4647 as follows:
 * "In filtering, each language range represents the least specific language
 * tag (that is, the language tag with fewest number of subtags) that is an
 * acceptable match. All of the language tags in the matching set of tags will
 * have an equal or greater number of subtags than the language range. Every
 * non-wildcard subtag in the language range will appear in every one of the
 * matching language tags."
 *
 * <p>There are two types of filtering: filtering for basic language ranges
 * (called "basic filtering") and filtering for extended language ranges
 * (called "extended filtering"). They may return different results by what
 * kind of language ranges are included in the given Language Priority List.
 * {@link Locale.FilteringMode} is a parameter to specify how filtering should
 * be done.
 *
 * <h5>Lookup</h5>
 *
 * <p>The lookup operation returns the best matching language tags. It is
 * defined in RFC 4647 as follows:
 * "By contrast with filtering, each language range represents the most
 * specific tag that is an acceptable match.  The first matching tag found,
 * according to the user's priority, is considered the closest match and is the
 * item returned."
 *
 * <p>For example, if a Language Priority List consists of two language ranges,
 * {@code "zh-Hant-TW"} and {@code "en-US"}, in prioritized order, lookup
 * method progressively searches the language tags below in order to find the
 * best matching language tag.
 * <blockquote>
 * <pre>
 *    1. zh-Hant-TW
 *    2. zh-Hant
 *    3. zh
 *    4. en-US
 *    5. en
 * </pre>
 * </blockquote>
 * If there is a language tag which matches completely to a language range
 * above, the language tag is returned.
 *
 * <p>{@code "*"} is the special language range, and it is ignored in lookup.
 *
 * <p>If multiple language tags match as a result of the subtag {@code '*'}
 * included in a language range, the first matching language tag returned by
 * an {@link Iterator} over a {@link Collection} of language tags is treated as
 * the best matching one.
 *
 * <h4>Use of Locale</h4>
 *
 * <p>Once you've created a <code>Locale</code> you can query it for information
 * about itself. Use <code>getCountry</code> to get the country (or region)
 * code and <code>getLanguage</code> to get the language code.
 * You can use <code>getDisplayCountry</code> to get the
 * name of the country suitable for displaying to the user. Similarly,
 * you can use <code>getDisplayLanguage</code> to get the name of
 * the language suitable for displaying to the user. Interestingly,
 * the <code>getDisplayXXX</code> methods are themselves locale-sensitive
 * and have two versions: one that uses the default
 * {@link LocaleCategory#DISPLAY DISPLAY} locale and one
 * that uses the locale specified as an argument.
 *
 * <p>The Java Platform provides a number of classes that perform locale-sensitive
 * operations. For example, the <code>NumberFormat</code> class formats
 * numbers, currency, and percentages in a locale-sensitive manner. Classes
 * such as <code>NumberFormat</code> have several convenience methods
 * for creating a default object of that type. For example, the
 * <code>NumberFormat</code> class provides these three convenience methods
 * for creating a default <code>NumberFormat</code> object:
 * <blockquote>
 * <pre>
 *     NumberFormat.getInstance()
 *     NumberFormat.getCurrencyInstance()
 *     NumberFormat.getPercentInstance()
 * </pre>
 * </blockquote>
 * Each of these methods has two variants; one with an explicit locale
 * and one without; the latter uses the default
 * {@link LocaleCategory#FORMAT FORMAT} locale:
 * <blockquote>
 * <pre>
 *     NumberFormat.getInstance(myLocale)
 *     NumberFormat.getCurrencyInstance(myLocale)
 *     NumberFormat.getPercentInstance(myLocale)
 * </pre>
 * </blockquote>
 * A <code>Locale</code> is the mechanism for identifying the kind of object
 * (<code>NumberFormat</code>) that you would like to get. The locale is
 * <STRONG>just</STRONG> a mechanism for identifying objects,
 * <STRONG>not</STRONG> a container for the objects themselves.
 *
 * <h4>Compatibility</h4>
 *
 * <p>In order to maintain compatibility with existing usage, Locale's
 * constructors retain their behavior prior to the Java Runtime
 * Environment version 1.7.  The same is largely true for the
 * <code>toString</code> method. Thus Locale objects can continue to
 * be used as they were. In particular, clients who parse the output
 * of toString into language, country, and variant fields can continue
 * to do so (although this is strongly discouraged), although the
 * variant field will have additional information in it if script or
 * extensions are present.
 *
 * <p>In addition, BCP 47 imposes syntax restrictions that are not
 * imposed by Locale's constructors. This means that conversions
 * between some Locales and BCP 47 language tags cannot be made without
 * losing information. Thus <code>toLanguageTag</code> cannot
 * represent the state of locales whose language, country, or variant
 * do not conform to BCP 47.
 *
 * <p>Because of these issues, it is recommended that clients migrate
 * away from constructing non-conforming locales and use the
 * <code>forLanguageTag</code> and <code>Locale.Builder</code> APIs instead.
 * Clients desiring a string representation of the complete locale can
 * then always rely on <code>toLanguageTag</code> for this purpose.
 *
 * <h5><a id="special_cases_constructor">Special cases</a></h5>
 *
 * <p>For compatibility reasons, two
 * non-conforming locales are treated as special cases.  These are
 * <b>{@code ja_JP_JP}</b> and <b>{@code th_TH_TH}</b>. These are ill-formed
 * in BCP 47 since the variants are too short. To ease migration to BCP 47,
 * these are treated specially during construction.  These two cases (and only
 * these) cause a constructor to generate an extension, all other values behave
 * exactly as they did prior to Java 7.
 *
 * <p>Java has used {@code ja_JP_JP} to represent Japanese as used in
 * Japan together with the Japanese Imperial calendar. This is now
 * representable using a Unicode locale extension, by specifying the
 * Unicode locale key {@code ca} (for "calendar") and type
 * {@code japanese}. When the Locale constructor is called with the
 * arguments "ja", "JP", "JP", the extension "u-ca-japanese" is
 * automatically added.
 *
 * <p>Java has used {@code th_TH_TH} to represent Thai as used in
 * Thailand together with Thai digits. This is also now representable using
 * a Unicode locale extension, by specifying the Unicode locale key
 * {@code nu} (for "number") and value {@code thai}. When the Locale
 * constructor is called with the arguments "th", "TH", "TH", the
 * extension "u-nu-thai" is automatically added.
 *
 * <h5>Serialization</h5>
 *
 * <p>During serialization, writeObject writes all fields to the output
 * stream, including extensions.
 *
 * <p>During deserialization, readResolve adds extensions as described
 * in <a href="#special_cases_constructor">Special Cases</a>, only
 * for the two cases th_TH_TH and ja_JP_JP.
 *
 * <h5>Legacy language codes</h5>
 *
 * <p>Locale's constructor has always converted three language codes to
 * their earlier, obsoleted forms: {@code he} maps to {@code iw},
 * {@code yi} maps to {@code ji}, and {@code id} maps to
 * {@code in}.  This continues to be the case, in order to not break
 * backwards compatibility.
 *
 * <p>The APIs added in 1.7 map between the old and new language codes,
 * maintaining the old codes internal to Locale (so that
 * <code>getLanguage</code> and <code>toString</code> reflect the old
 * code), but using the new codes in the BCP 47 language tag APIs (so
 * that <code>toLanguageTag</code> reflects the new one). This
 * preserves the equivalence between Locales no matter which code or
 * API is used to construct them. Java's default resource bundle
 * lookup mechanism also implements this mapping, so that resources
 * can be named using either convention, see {@link ResourceBundle.Control}.
 *
 * <h5>Three-letter language/country(region) codes</h5>
 *
 * <p>The Locale constructors have always specified that the language
 * and the country param be two characters in length, although in
 * practice they have accepted any length.  The specification has now
 * been relaxed to allow language codes of two to eight characters and
 * country (region) codes of two to three characters, and in
 * particular, three-letter language codes and three-digit region
 * codes as specified in the IANA Language Subtag Registry.  For
 * compatibility, the implementation still does not impose a length
 * constraint.
 *
 * @see Builder
 * @see ResourceBundle
 * @see java.text.Format
 * @see java.text.NumberFormat
 * @see java.text.Collator
 * @author Mark Davis
 */
final class Locale // : Cloneable
{

    private __gshared  Locale[size_t]  LOCALECACHE;

    /** Useful constant for language.
     */
    static Locale ENGLISH() {
        __gshared Locale m;
        return initOnce!(m)(createConstant("en", ""));
    }

    /** Useful constant for language.
     */
    static Locale FRENCH() {
        __gshared Locale m;
        return initOnce!(m)(createConstant("fr", ""));
    }

    /** Useful constant for language.
     */
    static Locale GERMAN() {
        __gshared Locale m;
        return initOnce!(m)(createConstant("de", ""));
    }

    /** Useful constant for language.
     */
    static Locale ITALIAN() {
        __gshared Locale m;
        return initOnce!(m)(createConstant("it", ""));
    }

    /** Useful constant for language.
     */
    static Locale JAPANESE() {
        __gshared Locale m;
        return initOnce!(m)(createConstant("ja", ""));
    }

    /** Useful constant for language.
     */
    static Locale KOREAN() {
        __gshared Locale m;
        return initOnce!(m)(createConstant("ko", ""));
    }

    /** Useful constant for language.
     */
    static Locale CHINESE() {
        __gshared Locale m;
        return initOnce!(m)(createConstant("zh", ""));
    }

    /** Useful constant for language.
     */
    static Locale SIMPLIFIED_CHINESE() {
        __gshared Locale m;
        return initOnce!(m)(createConstant("zh", "CN"));
    }

    /** Useful constant for language.
     */
    static Locale TRADITIONAL_CHINESE() {
        __gshared Locale m;
        return initOnce!(m)(createConstant("zh", "TW"));
    }

    /** Useful constant for country.
     */
    static Locale FRANCE() {
        __gshared Locale m;
        return initOnce!(m)(createConstant("fr", "FR"));
    }

    /** Useful constant for country.
     */
    static Locale GERMANY() {
        __gshared Locale m;
        return initOnce!(m)(createConstant("de", "DE"));
    }

    /** Useful constant for country.
     */
    static Locale ITALY() {
        __gshared Locale m;
        return initOnce!(m)(createConstant("it", "IT"));
    }

    /** Useful constant for country.
     */
    static Locale JAPAN() {
        __gshared Locale m;
        return initOnce!(m)(createConstant("ja", "JP"));
    }

    /** Useful constant for country.
     */
    static Locale KOREA() {
        __gshared Locale m;
        return initOnce!(m)(createConstant("ko", "KR"));
    }

    /** Useful constant for country.
     */
    
    alias CHINA = SIMPLIFIED_CHINESE;

    /** Useful constant for country.
     */
    alias PRC = SIMPLIFIED_CHINESE;

    /** Useful constant for country.
     */
    alias TAIWAN = TRADITIONAL_CHINESE;


    /** Useful constant for country.
     */
    static Locale UK() {
        __gshared Locale m;
        return initOnce!(m)(createConstant("en", "GB"));
    }

    /** Useful constant for country.
     */
    static Locale US() {
        __gshared Locale m;
        return initOnce!(m)(createConstant("en", "US"));
    }

    /** Useful constant for country.
     */
    static Locale CANADA() {
        __gshared Locale m;
        return initOnce!(m)(createConstant("en", "CA"));
    }

    /** Useful constant for country.
     */
    static Locale CANADA_FRENCH() {
        __gshared Locale m;
        return initOnce!(m)(createConstant("fr", "CA"));
    }

    /**
     * Useful constant for the root locale.  The root locale is the locale whose
     * language, country, and variant are empty ("") strings.  This is regarded
     * as the base locale of all locales, and is used as the language/country
     * neutral locale for the locale sensitive operations.
     *
     */
    static Locale ROOT() {
        __gshared Locale m;
        return initOnce!(m)(createConstant("", ""));
    }

    /**
     * The key for the private use extension ('x').
     *
     * @see #getExtension(char)
     * @see Builder#setExtension(char, string)
     */
    enum char PRIVATE_USE_EXTENSION = 'x';

    /**
     * The key for Unicode locale extension ('u').
     *
     * @see #getExtension(char)
     * @see Builder#setExtension(char, string)
     */
    enum char UNICODE_LOCALE_EXTENSION = 'u';


    /**
     * Enum for specifying the type defined in ISO 3166. This enum is used to
     * retrieve the two-letter ISO3166-1 alpha-2, three-letter ISO3166-1
     * alpha-3, four-letter ISO3166-3 country codes.
     *
     * @see #getISOCountries(Locale.IsoCountryCode)
     */
    static class IsoCountryCode
    {
        /**
         * PART1_ALPHA2 is used to represent the ISO3166-1 alpha-2 two letter
         * country codes.
         */
        __gshared IsoCountryCode PART1_ALPHA2;

        shared static this()
        {
            PART1_ALPHA2 = new class IsoCountryCode
            {
                override Set!(string) createCountryCodeSet()
                {
                    implementationMissing();
                    return null;
                    // return Set.of(Locale.getISOCountries());
                }
            };
            PART1_ALPHA3 = new class IsoCountryCode
            {
                override Set!(string) createCountryCodeSet()
                {
                     implementationMissing();
                    return null;
                    // return LocaleISOData.computeISO3166_1Alpha3Countries();
                }
            };

            PART3 = new class IsoCountryCode
            {
                override Set!(string) createCountryCodeSet()
                {
                     implementationMissing();
                    return null;
                    // return Set.of(LocaleISOData.ISO3166_3);
                }
            };
        }

        /**
         *
         * PART1_ALPHA3 is used to represent the ISO3166-1 alpha-3 three letter
         * country codes.
         */
        __gshared IsoCountryCode PART1_ALPHA3;

        /**
         * PART3 is used to represent the ISO3166-3 four letter country codes.
         */
        __gshared IsoCountryCode PART3;

        /**
         * Concrete implementation of this method attempts to compute value
         * for iso3166CodesMap for each IsoCountryCode type key.
         */
        abstract Set!(string) createCountryCodeSet();

        /**
         * Map to hold country codes for each ISO3166 part.
         */
        private __gshared Map!(IsoCountryCode, Set!(string)) iso3166CodesMap;

        shared static this()
        {
            iso3166CodesMap = new HashMap!(IsoCountryCode, Set!(string))();
        }

        /**
         * This method is called from Locale class to retrieve country code set
         * for getISOCountries(type)
         */
        static Set!(string) retrieveISOCountryCodes(IsoCountryCode type)
        {
            implementationMissing();
            return null;
            // return iso3166CodesMap.computeIfAbsent(type, IsoCountryCode.createCountryCodeSet);
        }
    }

    /**
     * Display types for retrieving localized names from the name providers.
     */
    private enum int DISPLAY_LANGUAGE = 0;
    private enum int DISPLAY_COUNTRY = 1;
    private enum int DISPLAY_VARIANT = 2;
    private enum int DISPLAY_SCRIPT = 3;
    private enum int DISPLAY_UEXT_KEY = 4;
    private enum int DISPLAY_UEXT_TYPE = 5;

    private string language;
    private string script;
    private string region;
    private string variant;

    /**
     * Private constructor used by getInstance method
     */
    // private this(BaseLocale baseLocale, LocaleExtensions extensions) {
    //     this.baseLocale = baseLocale;
    //     this.localeExtensions = extensions;
    // }

    /**
     * Construct a locale from language, country and variant.
     * This constructor normalizes the language value to lowercase and
     * the country value to uppercase.
     * <p>
     * <b>Note:</b>
     * <ul>
     * <li>ISO 639 is not a stable standard; some of the language codes it defines
     * (specifically "iw", "ji", and "in") have changed.  This constructor accepts both the
     * old codes ("iw", "ji", and "in") and the new codes ("he", "yi", and "id"), but all other
     * API on Locale will return only the OLD codes.
     * <li>For backward compatibility reasons, this constructor does not make
     * any syntactic checks on the input.
     * <li>The two cases ("ja", "JP", "JP") and ("th", "TH", "TH") are handled specially,
     * see <a href="#special_cases_constructor">Special Cases</a> for more information.
     * </ul>
     *
     * @param language An ISO 639 alpha-2 or alpha-3 language code, or a language subtag
     * up to 8 characters in length.  See the <code>Locale</code> class description about
     * valid language values.
     * @param country An ISO 3166 alpha-2 country code or a UN M.49 numeric-3 area code.
     * See the <code>Locale</code> class description about valid country values.
     * @param variant Any arbitrary value used to indicate a variation of a <code>Locale</code>.
     * See the <code>Locale</code> class description for the details.
     * @exception NullPointerException thrown if any argument is null.
     */
    this(string language, string country, string variant)
    {
        if (language is null || country is null || variant is null)
        {
            throw new NullPointerException();
        }

        this.language = convertOldISOCodes(language);        
        this.region = country;
        this.variant = variant;
    }

    /**
     * Construct a locale from language and country.
     * This constructor normalizes the language value to lowercase and
     * the country value to uppercase.
     * <p>
     * <b>Note:</b>
     * <ul>
     * <li>ISO 639 is not a stable standard; some of the language codes it defines
     * (specifically "iw", "ji", and "in") have changed.  This constructor accepts both the
     * old codes ("iw", "ji", and "in") and the new codes ("he", "yi", and "id"), but all other
     * API on Locale will return only the OLD codes.
     * <li>For backward compatibility reasons, this constructor does not make
     * any syntactic checks on the input.
     * </ul>
     *
     * @param language An ISO 639 alpha-2 or alpha-3 language code, or a language subtag
     * up to 8 characters in length.  See the <code>Locale</code> class description about
     * valid language values.
     * @param country An ISO 3166 alpha-2 country code or a UN M.49 numeric-3 area code.
     * See the <code>Locale</code> class description about valid country values.
     * @exception NullPointerException thrown if either argument is null.
     */
    this(string language, string country)
    {
        this(language, country, "");
    }

    /**
     * Construct a locale from a language code.
     * This constructor normalizes the language value to lowercase.
     * <p>
     * <b>Note:</b>
     * <ul>
     * <li>ISO 639 is not a stable standard; some of the language codes it defines
     * (specifically "iw", "ji", and "in") have changed.  This constructor accepts both the
     * old codes ("iw", "ji", and "in") and the new codes ("he", "yi", and "id"), but all other
     * API on Locale will return only the OLD codes.
     * <li>For backward compatibility reasons, this constructor does not make
     * any syntactic checks on the input.
     * </ul>
     *
     * @param language An ISO 639 alpha-2 or alpha-3 language code, or a language subtag
     * up to 8 characters in length.  See the <code>Locale</code> class description about
     * valid language values.
     * @exception NullPointerException thrown if argument is null.
     */
    this(string language)
    {
        this(language, "", "");
    }

    /**
     * This method must be called only for creating the Locale.*
     * constants due to making shortcuts.
     */
    private static Locale createConstant(string lang, string country)
    {
        // BaseLocale base = BaseLocale.createInstance(lang, country);
        // return getInstance(base, null);
        Locale le = new Locale(lang, country);
        size_t key = hashOf(lang, country) ;
        LOCALECACHE[key] = le;

        return le;
    }

    static size_t hashOf(string language, string country, string script = null, string variant = null) {
        size_t r = 0;
        if(language !is null)
            r += .hashOf(language.toLower());
        if(country !is null)
            r += .hashOf(country.toLower());
        if(script !is null)
            r += .hashOf(script.toLower());
        if(variant !is null)
            r += .hashOf(variant.toLower());
        return r;
    }

    /**
     * Returns a <code>Locale</code> constructed from the given
     * <code>language</code>, <code>country</code> and
     * <code>variant</code>. If the same <code>Locale</code> instance
     * is available in the cache, then that instance is
     * returned. Otherwise, a new <code>Locale</code> instance is
     * created and cached.
     *
     * @param language lowercase 2 to 8 language code.
     * @param country uppercase two-letter ISO-3166 code and numeric-3 UN M.49 area code.
     * @param variant vendor and browser specific code. See class description.
     * @return the <code>Locale</code> instance requested
     * @exception NullPointerException if any argument is null.
     */
    static Locale getInstance(string language, string country, string variant) {
        return getInstance(language, "", country, variant);
    }

    static Locale getInstance(string language, string script, string country, string variant) {
        if (language is null || script is null || country is null || variant is null) {
            throw new NullPointerException();
        }

        version(HUNT_DEBUG) {
            tracef("language=%s, script=%s, country=%s, variant=%s", 
                language, script, country, variant);
        }
        size_t key = hashOf(language, country, script, variant);
        Locale le = LOCALECACHE.get(key, null);
        if(le is null)  {
            le = new Locale(language,  country, variant);
            LOCALECACHE[key] = le;
        }
        return le;
    }

    /**
     * Gets the current value of the default locale for this instance
     * of the Java Virtual Machine.
     * <p>
     * The Java Virtual Machine sets the default locale during startup
     * based on the host environment. It is used by many locale-sensitive
     * methods if no locale is explicitly specified.
     * It can be changed using the
     * {@link #setDefault(java.util.Locale) setDefault} method.
     *
     * @return the default locale for this instance of the Java Virtual Machine
     */
    static Locale getDefault()
    {
        return initOnce!(defaultLocale)(initDefault());
        // do not synchronize this method - see 4071298
    }
    private __gshared Locale defaultLocale;

    /**
     * Gets the current value of the default locale for the specified Category
     * for this instance of the Java Virtual Machine.
     * <p>
     * The Java Virtual Machine sets the default locale during startup based
     * on the host environment. It is used by many locale-sensitive methods
     * if no locale is explicitly specified. It can be changed using the
     * setDefault(LocaleCategory, Locale) method.
     *
     * @param category - the specified category to get the default locale
     * @throws NullPointerException if category is null
     * @return the default locale for the specified Category for this instance
     *     of the Java Virtual Machine
     * @see #setDefault(LocaleCategory, Locale)
     */
    static Locale getDefault(LocaleCategory category) {
        // do not synchronize this method - see 4071298
        if(category == LocaleCategory.DISPLAY) {
            if (defaultDisplayLocale is null) {
                synchronized {
                    if (defaultDisplayLocale is null) {
                        defaultDisplayLocale = initDefault(category);
                    }
                }
            }
            return defaultDisplayLocale;
        } else if(category == LocaleCategory.FORMAT) {
            if (defaultFormatLocale is null) {
                synchronized {
                    if (defaultFormatLocale is null) {
                        defaultFormatLocale = initDefault(category);
                    }
                }
            }
            return defaultFormatLocale;
        } else {
            assert(false, "Unknown locale category");
        }
    }

    private static Locale initDefault() {
        ConfigBuilder props = Environment.getProperties();
        string language = props.getProperty("user.language", "en");
        string script = props.getProperty("user.script", "");
        string country = props.getProperty("user.country", "");
        string variant = props.getProperty("user.variant", "");

        return getInstance(language, script, country, variant);
    }

    private static Locale initDefault(LocaleCategory category) {
        ConfigBuilder props = Environment.getProperties();
        Locale defaultLocale = getDefault();

        return getInstance(
            props.getProperty(category.languageKey,
                    defaultLocale.getLanguage()),
            props.getProperty(category.scriptKey,
                    defaultLocale.getScript()),
            props.getProperty(category.countryKey,
                    defaultLocale.getCountry()),
            props.getProperty(category.variantKey,
                    defaultLocale.getVariant()));
    }


    /**
     * Sets the default locale for this instance of the Java Virtual Machine.
     * This does not affect the host locale.
     * <p>
     * If there is a security manager, its <code>checkPermission</code>
     * method is called with a <code>PropertyPermission("user.language", "write")</code>
     * permission before the default locale is changed.
     * <p>
     * The Java Virtual Machine sets the default locale during startup
     * based on the host environment. It is used by many locale-sensitive
     * methods if no locale is explicitly specified.
     * <p>
     * Since changing the default locale may affect many different areas
     * of functionality, this method should only be used if the caller
     * is prepared to reinitialize locale-sensitive code running
     * within the same Java Virtual Machine.
     * <p>
     * By setting the default locale with this method, all of the default
     * locales for each Category are also set to the specified default locale.
     *
     * @throws SecurityException
     *        if a security manager exists and its
     *        <code>checkPermission</code> method doesn't allow the operation.
     * @throws NullPointerException if <code>newLocale</code> is null
     * @param newLocale the new default locale
     * @see SecurityManager#checkPermission
     * @see java.util.PropertyPermission
     */
    static void setDefault(Locale newLocale) {
        setDefault(LocaleCategory.DISPLAY, newLocale);
        setDefault(LocaleCategory.FORMAT, newLocale);
        defaultLocale = newLocale;
    }

    /**
     * Sets the default locale for the specified Category for this instance
     * of the Java Virtual Machine. This does not affect the host locale.
     * <p>
     * If there is a security manager, its checkPermission method is called
     * with a PropertyPermission("user.language", "write") permission before
     * the default locale is changed.
     * <p>
     * The Java Virtual Machine sets the default locale during startup based
     * on the host environment. It is used by many locale-sensitive methods
     * if no locale is explicitly specified.
     * <p>
     * Since changing the default locale may affect many different areas of
     * functionality, this method should only be used if the caller is
     * prepared to reinitialize locale-sensitive code running within the
     * same Java Virtual Machine.
     *
     * @param category - the specified category to set the default locale
     * @param newLocale - the new default locale
     * @throws SecurityException if a security manager exists and its
     *     checkPermission method doesn't allow the operation.
     * @throws NullPointerException if category and/or newLocale is null
     * @see SecurityManager#checkPermission(java.security.Permission)
     * @see PropertyPermission
     * @see #getDefault(LocaleCategory)
     */
    static void setDefault(LocaleCategory category, Locale newLocale) {
        implementationMissing(false);
        // if (category is null)
        //     throw new NullPointerException("Category cannot be NULL");
        // if (newLocale is null)
        //     throw new NullPointerException("Can't set default locale to NULL");

        // SecurityManager sm = System.getSecurityManager();
        // if (sm !is null) sm.checkPermission(new PropertyPermission
        //                 ("user.language", "write"));
        // switch (category) {
        // case DISPLAY:
        //     defaultDisplayLocale = newLocale;
        //     break;
        // case FORMAT:
        //     defaultFormatLocale = newLocale;
        //     break;
        // default:
        //     assert false: "Unknown Category";
        // }
    }

    // /**
    //  * Returns an array of all installed locales.
    //  * The returned array represents the union of locales supported
    //  * by the Java runtime environment and by installed
    //  * {@link java.util.spi.LocaleServiceProvider LocaleServiceProvider}
    //  * implementations.  It must contain at least a <code>Locale</code>
    //  * instance equal to {@link java.util.Locale#US Locale.US}.
    //  *
    //  * @return An array of installed locales.
    //  */
    // static Locale[] getAvailableLocales() {
    //     return LocaleServiceProviderPool.getAllAvailableLocales();
    // }

    // /**
    //  * Returns a list of all 2-letter country codes defined in ISO 3166.
    //  * Can be used to create Locales.
    //  * This method is equivalent to {@link #getISOCountries(Locale.IsoCountryCode type)}
    //  * with {@code type}  {@link IsoCountryCode#PART1_ALPHA2}.
    //  * <p>
    //  * <b>Note:</b> The <code>Locale</code> class also supports other codes for
    //  * country (region), such as 3-letter numeric UN M.49 area codes.
    //  * Therefore, the list returned by this method does not contain ALL valid
    //  * codes that can be used to create Locales.
    //  * <p>
    //  * Note that this method does not return obsolete 2-letter country codes.
    //  * ISO3166-3 codes which designate country codes for those obsolete codes,
    //  * can be retrieved from {@link #getISOCountries(Locale.IsoCountryCode type)} with
    //  * {@code type}  {@link IsoCountryCode#PART3}.
    //  * @return An array of ISO 3166 two-letter country codes.
    //  */
    // static string[] getISOCountries() {
    //     if (isoCountries is null) {
    //         isoCountries = getISO2Table(LocaleISOData.isoCountryTable);
    //     }
    //     string[] result = new string[isoCountries.length];
    //     System.arraycopy(isoCountries, 0, result, 0, isoCountries.length);
    //     return result;
    // }

    // /**
    //  * Returns a {@code Set} of ISO3166 country codes for the specified type.
    //  *
    //  * @param type {@link Locale.IsoCountryCode} specified ISO code type.
    //  * @see java.util.Locale.IsoCountryCode
    //  * @throws NullPointerException if type is null
    //  * @return a {@code Set} of ISO country codes for the specified type.
    //  */
    // static Set!(string) getISOCountries(IsoCountryCode type) {
    //     assert(type);
    //     return IsoCountryCode.retrieveISOCountryCodes(type);
    // }

    // /**
    //  * Returns a list of all 2-letter language codes defined in ISO 639.
    //  * Can be used to create Locales.
    //  * <p>
    //  * <b>Note:</b>
    //  * <ul>
    //  * <li>ISO 639 is not a stable standard&mdash; some languages' codes have changed.
    //  * The list this function returns includes both the new and the old codes for the
    //  * languages whose codes have changed.
    //  * <li>The <code>Locale</code> class also supports language codes up to
    //  * 8 characters in length.  Therefore, the list returned by this method does
    //  * not contain ALL valid codes that can be used to create Locales.
    //  * </ul>
    //  *
    //  * @return An array of ISO 639 two-letter language codes.
    //  */
    // static string[] getISOLanguages() {
    //     if (isoLanguages is null) {
    //         isoLanguages = getISO2Table(LocaleISOData.isoLanguageTable);
    //     }
    //     string[] result = new string[isoLanguages.length];
    //     System.arraycopy(isoLanguages, 0, result, 0, isoLanguages.length);
    //     return result;
    // }

    // private static string[] getISO2Table(string table) {
    //     int len = table.length() / 5;
    //     string[] isoTable = new string[len];
    //     for (int i = 0, j = 0; i < len; i++, j += 5) {
    //         isoTable[i] = table.substring(j, j + 2);
    //     }
    //     return isoTable;
    // }

    /**
     * Returns the language code of this Locale.
     *
     * <p><b>Note:</b> ISO 639 is not a stable standard&mdash; some languages' codes have changed.
     * Locale's constructor recognizes both the new and the old codes for the languages
     * whose codes have changed, but this function always returns the old code.  If you
     * want to check for a specific language whose code has changed, don't do
     * <pre>
     * if (locale.getLanguage().equals("he")) // BAD!
     *    ...
     * </pre>
     * Instead, do
     * <pre>
     * if (locale.getLanguage().equals(new Locale("he").getLanguage()))
     *    ...
     * </pre>
     * @return The language code, or the empty string if none is defined.
     * @see #getDisplayLanguage
     */
    string getLanguage() {
        return language;
    }

    /**
     * Returns the script for this locale, which should
     * either be the empty string or an ISO 15924 4-letter script
     * code. The first letter is uppercase and the rest are
     * lowercase, for example, 'Latn', 'Cyrl'.
     *
     * @return The script code, or the empty string if none is defined.
     * @see #getDisplayScript
     */
    string getScript() {
        return script;
    }

    /**
     * Returns the country/region code for this locale, which should
     * either be the empty string, an uppercase ISO 3166 2-letter code,
     * or a UN M.49 3-digit code.
     *
     * @return The country/region code, or the empty string if none is defined.
     * @see #getDisplayCountry
     */
    string getCountry() {
        return region;
    }

    /**
     * Returns the variant code for this locale.
     *
     * @return The variant code, or the empty string if none is defined.
     * @see #getDisplayVariant
     */
    string getVariant() {
        return variant;
    }

    /**
     * Returns {@code true} if this {@code Locale} has any <a href="#def_extensions">
     * extensions</a>.
     *
     * @return {@code true} if this {@code Locale} has any extensions
     */
    bool hasExtensions() {
        return false;
    }

    // /**
    //  * Returns a copy of this {@code Locale} with no <a href="#def_extensions">
    //  * extensions</a>. If this {@code Locale} has no extensions, this {@code Locale}
    //  * is returned.
    //  *
    //  * @return a copy of this {@code Locale} with no extensions, or {@code this}
    //  *         if {@code this} has no extensions
    //  */
    // Locale stripExtensions() {
    //     return hasExtensions() ? Locale.getInstance(baseLocale, null) : this;
    // }

    // /**
    //  * Returns the extension (or private use) value associated with
    //  * the specified key, or null if there is no extension
    //  * associated with the key. To be well-formed, the key must be one
    //  * of <code>[0-9A-Za-z]</code>. Keys are case-insensitive, so
    //  * for example 'z' and 'Z' represent the same extension.
    //  *
    //  * @param key the extension key
    //  * @return The extension, or null if this locale defines no
    //  * extension for the specified key.
    //  * @throws IllegalArgumentException if key is not well-formed
    //  * @see #PRIVATE_USE_EXTENSION
    //  * @see #UNICODE_LOCALE_EXTENSION
    //  */
    // string getExtension(char key) {
    //     if (!LocaleExtensions.isValidKey(key)) {
    //         throw new IllegalArgumentException("Ill-formed extension key: " ~ key);
    //     }
    //     return hasExtensions() ? localeExtensions.getExtensionValue(key) : null;
    // }

    // /**
    //  * Returns the set of extension keys associated with this locale, or the
    //  * empty set if it has no extensions. The returned set is unmodifiable.
    //  * The keys will all be lower-case.
    //  *
    //  * @return The set of extension keys, or the empty set if this locale has
    //  * no extensions.
    //  */
    // Set<Character> getExtensionKeys() {
    //     if (!hasExtensions()) {
    //         return Collections.emptySet();
    //     }
    //     return localeExtensions.getKeys();
    // }

    // /**
    //  * Returns the set of unicode locale attributes associated with
    //  * this locale, or the empty set if it has no attributes. The
    //  * returned set is unmodifiable.
    //  *
    //  * @return The set of attributes.
    //  */
    // Set!(string) getUnicodeLocaleAttributes() {
    //     if (!hasExtensions()) {
    //         return Collections.emptySet();
    //     }
    //     return localeExtensions.getUnicodeLocaleAttributes();
    // }

    // /**
    //  * Returns the Unicode locale type associated with the specified Unicode locale key
    //  * for this locale. Returns the empty string for keys that are defined with no type.
    //  * Returns null if the key is not defined. Keys are case-insensitive. The key must
    //  * be two alphanumeric characters ([0-9a-zA-Z]), or an IllegalArgumentException is
    //  * thrown.
    //  *
    //  * @param key the Unicode locale key
    //  * @return The Unicode locale type associated with the key, or null if the
    //  * locale does not define the key.
    //  * @throws IllegalArgumentException if the key is not well-formed
    //  * @throws NullPointerException if <code>key</code> is null
    //  */
    string getUnicodeLocaleType(string key) {
        /* if (!isUnicodeExtensionKey(key)) {
            throw new IllegalArgumentException("Ill-formed Unicode locale key: " ~ key);
        }
        return hasExtensions() ? localeExtensions.getUnicodeLocaleType(key) : null; */
        return "iso";
    }

    // /**
    //  * Returns the set of Unicode locale keys defined by this locale, or the empty set if
    //  * this locale has none.  The returned set is immutable.  Keys are all lower case.
    //  *
    //  * @return The set of Unicode locale keys, or the empty set if this locale has
    //  * no Unicode locale keywords.
    //  */
    // Set!(string) getUnicodeLocaleKeys() {
    //     if (localeExtensions is null) {
    //         return Collections.emptySet();
    //     }
    //     return localeExtensions.getUnicodeLocaleKeys();
    // }

    // /**
    //  * Package locale method returning the Locale's BaseLocale,
    //  * used by ResourceBundle
    //  * @return base locale of this Locale
    //  */
    // BaseLocale getBaseLocale() {
    //     return baseLocale;
    // }

    // /**
    //  * Package private method returning the Locale's LocaleExtensions,
    //  * used by ResourceBundle.
    //  * @return locale extensions of this Locale,
    //  *         or {@code null} if no extensions are defined
    //  */
    //  LocaleExtensions getLocaleExtensions() {
    //      return localeExtensions;
    //  }

    /**
     * Returns a string representation of this <code>Locale</code>
     * object, consisting of language, country, variant, script,
     * and extensions as below:
     * <blockquote>
     * language ~ "_" ~ country ~ "_" ~ (variant ~ "_#" | "#") + script ~ "_" ~ extensions
     * </blockquote>
     *
     * Language is always lower case, country is always upper case, script is always title
     * case, and extensions are always lower case.  Extensions and private use subtags
     * will be in canonical order as explained in {@link #toLanguageTag}.
     *
     * <p>When the locale has neither script nor extensions, the result is the same as in
     * Java 6 and prior.
     *
     * <p>If both the language and country fields are missing, this function will return
     * the empty string, even if the variant, script, or extensions field is present (you
     * can't have a locale with just a variant, the variant must accompany a well-formed
     * language or country code).
     *
     * <p>If script or extensions are present and variant is missing, no underscore is
     * added before the "#".
     *
     * <p>This behavior is designed to support debugging and to be compatible with
     * previous uses of <code>toString</code> that expected language, country, and variant
     * fields only.  To represent a Locale as a string for interchange purposes, use
     * {@link #toLanguageTag}.
     *
     * <p>Examples: <ul>
     * <li>{@code en}</li>
     * <li>{@code de_DE}</li>
     * <li>{@code _GB}</li>
     * <li>{@code en_US_WIN}</li>
     * <li>{@code de__POSIX}</li>
     * <li>{@code zh_CN_#Hans}</li>
     * <li>{@code zh_TW_#Hant_x-java}</li>
     * <li>{@code th_TH_TH_#u-nu-thai}</li></ul>
     *
     * @return A string representation of the Locale, for debugging.
     * @see #getDisplayName
     * @see #toLanguageTag
     */
    override string toString() {

        bool l = (language.length != 0);
        bool s = (script.length != 0);
        bool r = (region.length != 0);
        bool v = (variant.length != 0);
        // bool e = (localeExtensions !is null && localeExtensions.getID().length() != 0);

        StringBuilder result = new StringBuilder(language);
        if (r || (l && (v || s ))) {
            result.append('_')
                .append(region); // This may just append '_'
        }
        if (v && (l || r)) {
            result.append('_')
                .append(variant);
        }

        if (s && (l || r)) {
            result.append("_#")
                .append(script);
        }

        return result.toString();
    }

    // /**
    //  * Returns a well-formed IETF BCP 47 language tag representing
    //  * this locale.
    //  *
    //  * <p>If this <code>Locale</code> has a language, country, or
    //  * variant that does not satisfy the IETF BCP 47 language tag
    //  * syntax requirements, this method handles these fields as
    //  * described below:
    //  *
    //  * <p><b>Language:</b> If language is empty, or not <a
    //  * href="#def_language" >well-formed</a> (for example "a" or
    //  * "e2"), it will be emitted as "und" (Undetermined).
    //  *
    //  * <p><b>Country:</b> If country is not <a
    //  * href="#def_region">well-formed</a> (for example "12" or "USA"),
    //  * it will be omitted.
    //  *
    //  * <p><b>Variant:</b> If variant <b>is</b> <a
    //  * href="#def_variant">well-formed</a>, each sub-segment
    //  * (delimited by '-' or '_') is emitted as a subtag.  Otherwise:
    //  * <ul>
    //  *
    //  * <li>if all sub-segments match <code>[0-9a-zA-Z]{1,8}</code>
    //  * (for example "WIN" or "Oracle_JDK_Standard_Edition"), the first
    //  * ill-formed sub-segment and all following will be appended to
    //  * the private use subtag.  The first appended subtag will be
    //  * "lvariant", followed by the sub-segments in order, separated by
    //  * hyphen. For example, "x-lvariant-WIN",
    //  * "Oracle-x-lvariant-JDK-Standard-Edition".
    //  *
    //  * <li>if any sub-segment does not match
    //  * <code>[0-9a-zA-Z]{1,8}</code>, the variant will be truncated
    //  * and the problematic sub-segment and all following sub-segments
    //  * will be omitted.  If the remainder is non-empty, it will be
    //  * emitted as a private use subtag as above (even if the remainder
    //  * turns out to be well-formed).  For example,
    //  * "Solaris_isjustthecoolestthing" is emitted as
    //  * "x-lvariant-Solaris", not as "solaris".</li></ul>
    //  *
    //  * <p><b>Special Conversions:</b> Java supports some old locale
    //  * representations, including deprecated ISO language codes,
    //  * for compatibility. This method performs the following
    //  * conversions:
    //  * <ul>
    //  *
    //  * <li>Deprecated ISO language codes "iw", "ji", and "in" are
    //  * converted to "he", "yi", and "id", respectively.
    //  *
    //  * <li>A locale with language "no", country "NO", and variant
    //  * "NY", representing Norwegian Nynorsk (Norway), is converted
    //  * to a language tag "nn-NO".</li></ul>
    //  *
    //  * <p><b>Note:</b> Although the language tag created by this
    //  * method is well-formed (satisfies the syntax requirements
    //  * defined by the IETF BCP 47 specification), it is not
    //  * necessarily a valid BCP 47 language tag.  For example,
    //  * <pre>
    //  *   new Locale("xx", "YY").toLanguageTag();</pre>
    //  *
    //  * will return "xx-YY", but the language subtag "xx" and the
    //  * region subtag "YY" are invalid because they are not registered
    //  * in the IANA Language Subtag Registry.
    //  *
    //  * @return a BCP47 language tag representing the locale
    //  * @see #forLanguageTag(string)
    //  */
    // string toLanguageTag() {
    //     if (languageTag !is null) {
    //         return languageTag;
    //     }

    //     LanguageTag tag = LanguageTag.parseLocale(baseLocale, localeExtensions);
    //     StringBuilder buf = new StringBuilder();

    //     string subtag = tag.getLanguage();
    //     if (subtag.length() > 0) {
    //         buf.append(LanguageTag.canonicalizeLanguage(subtag));
    //     }

    //     subtag = tag.getScript();
    //     if (subtag.length() > 0) {
    //         buf.append(LanguageTag.SEP);
    //         buf.append(LanguageTag.canonicalizeScript(subtag));
    //     }

    //     subtag = tag.getRegion();
    //     if (subtag.length() > 0) {
    //         buf.append(LanguageTag.SEP);
    //         buf.append(LanguageTag.canonicalizeRegion(subtag));
    //     }

    //     List<string>subtags = tag.getVariants();
    //     for (string s : subtags) {
    //         buf.append(LanguageTag.SEP);
    //         // preserve casing
    //         buf.append(s);
    //     }

    //     subtags = tag.getExtensions();
    //     for (string s : subtags) {
    //         buf.append(LanguageTag.SEP);
    //         buf.append(LanguageTag.canonicalizeExtension(s));
    //     }

    //     subtag = tag.getPrivateuse();
    //     if (subtag.length() > 0) {
    //         if (buf.length() > 0) {
    //             buf.append(LanguageTag.SEP);
    //         }
    //         buf.append(LanguageTag.PRIVATEUSE).append(LanguageTag.SEP);
    //         // preserve casing
    //         buf.append(subtag);
    //     }

    //     string langTag = buf.toString();
    //     synchronized (this) {
    //         if (languageTag is null) {
    //             languageTag = langTag;
    //         }
    //     }
    //     return languageTag;
    // }

    // /**
    //  * Returns a locale for the specified IETF BCP 47 language tag string.
    //  *
    //  * <p>If the specified language tag contains any ill-formed subtags,
    //  * the first such subtag and all following subtags are ignored.  Compare
    //  * to {@link Locale.Builder#setLanguageTag} which throws an exception
    //  * in this case.
    //  *
    //  * <p>The following <b>conversions</b> are performed:<ul>
    //  *
    //  * <li>The language code "und" is mapped to language "".
    //  *
    //  * <li>The language codes "he", "yi", and "id" are mapped to "iw",
    //  * "ji", and "in" respectively. (This is the same canonicalization
    //  * that's done in Locale's constructors.)
    //  *
    //  * <li>The portion of a private use subtag prefixed by "lvariant",
    //  * if any, is removed and appended to the variant field in the
    //  * result locale (without case normalization).  If it is then
    //  * empty, the private use subtag is discarded:
    //  *
    //  * <pre>
    //  *     Locale loc;
    //  *     loc = Locale.forLanguageTag("en-US-x-lvariant-POSIX");
    //  *     loc.getVariant(); // returns "POSIX"
    //  *     loc.getExtension('x'); // returns null
    //  *
    //  *     loc = Locale.forLanguageTag("de-POSIX-x-URP-lvariant-Abc-Def");
    //  *     loc.getVariant(); // returns "POSIX_Abc_Def"
    //  *     loc.getExtension('x'); // returns "urp"
    //  * </pre>
    //  *
    //  * <li>When the languageTag argument contains an extlang subtag,
    //  * the first such subtag is used as the language, and the primary
    //  * language subtag and other extlang subtags are ignored:
    //  *
    //  * <pre>
    //  *     Locale.forLanguageTag("ar-aao").getLanguage(); // returns "aao"
    //  *     Locale.forLanguageTag("en-abc-def-us").toString(); // returns "abc_US"
    //  * </pre>
    //  *
    //  * <li>Case is normalized except for variant tags, which are left
    //  * unchanged.  Language is normalized to lower case, script to
    //  * title case, country to upper case, and extensions to lower
    //  * case.
    //  *
    //  * <li>If, after processing, the locale would exactly match either
    //  * ja_JP_JP or th_TH_TH with no extensions, the appropriate
    //  * extensions are added as though the constructor had been called:
    //  *
    //  * <pre>
    //  *    Locale.forLanguageTag("ja-JP-x-lvariant-JP").toLanguageTag();
    //  *    // returns "ja-JP-u-ca-japanese-x-lvariant-JP"
    //  *    Locale.forLanguageTag("th-TH-x-lvariant-TH").toLanguageTag();
    //  *    // returns "th-TH-u-nu-thai-x-lvariant-TH"
    //  * </pre></ul>
    //  *
    //  * <p>This implements the 'Language-Tag' production of BCP47, and
    //  * so supports grandfathered (regular and irregular) as well as
    //  * private use language tags.  Stand alone private use tags are
    //  * represented as empty language and extension 'x-whatever',
    //  * and grandfathered tags are converted to their canonical replacements
    //  * where they exist.
    //  *
    //  * <p>Grandfathered tags with canonical replacements are as follows:
    //  *
    //  * <table class="striped">
    //  * <caption style="display:none">Grandfathered tags with canonical replacements</caption>
    //  * <thead style="text-align:center">
    //  * <tr><th scope="col" style="padding: 0 2px">grandfathered tag</th><th scope="col" style="padding: 0 2px">modern replacement</th></tr>
    //  * </thead>
    //  * <tbody style="text-align:center">
    //  * <tr><th scope="row">art-lojban</th><td>jbo</td></tr>
    //  * <tr><th scope="row">i-ami</th><td>ami</td></tr>
    //  * <tr><th scope="row">i-bnn</th><td>bnn</td></tr>
    //  * <tr><th scope="row">i-hak</th><td>hak</td></tr>
    //  * <tr><th scope="row">i-klingon</th><td>tlh</td></tr>
    //  * <tr><th scope="row">i-lux</th><td>lb</td></tr>
    //  * <tr><th scope="row">i-navajo</th><td>nv</td></tr>
    //  * <tr><th scope="row">i-pwn</th><td>pwn</td></tr>
    //  * <tr><th scope="row">i-tao</th><td>tao</td></tr>
    //  * <tr><th scope="row">i-tay</th><td>tay</td></tr>
    //  * <tr><th scope="row">i-tsu</th><td>tsu</td></tr>
    //  * <tr><th scope="row">no-bok</th><td>nb</td></tr>
    //  * <tr><th scope="row">no-nyn</th><td>nn</td></tr>
    //  * <tr><th scope="row">sgn-BE-FR</th><td>sfb</td></tr>
    //  * <tr><th scope="row">sgn-BE-NL</th><td>vgt</td></tr>
    //  * <tr><th scope="row">sgn-CH-DE</th><td>sgg</td></tr>
    //  * <tr><th scope="row">zh-guoyu</th><td>cmn</td></tr>
    //  * <tr><th scope="row">zh-hakka</th><td>hak</td></tr>
    //  * <tr><th scope="row">zh-min-nan</th><td>nan</td></tr>
    //  * <tr><th scope="row">zh-xiang</th><td>hsn</td></tr>
    //  * </tbody>
    //  * </table>
    //  *
    //  * <p>Grandfathered tags with no modern replacement will be
    //  * converted as follows:
    //  *
    //  * <table class="striped">
    //  * <caption style="display:none">Grandfathered tags with no modern replacement</caption>
    //  * <thead style="text-align:center">
    //  * <tr><th scope="col" style="padding: 0 2px">grandfathered tag</th><th scope="col" style="padding: 0 2px">converts to</th></tr>
    //  * </thead>
    //  * <tbody style="text-align:center">
    //  * <tr><th scope="row">cel-gaulish</th><td>xtg-x-cel-gaulish</td></tr>
    //  * <tr><th scope="row">en-GB-oed</th><td>en-GB-x-oed</td></tr>
    //  * <tr><th scope="row">i-default</th><td>en-x-i-default</td></tr>
    //  * <tr><th scope="row">i-enochian</th><td>und-x-i-enochian</td></tr>
    //  * <tr><th scope="row">i-mingo</th><td>see-x-i-mingo</td></tr>
    //  * <tr><th scope="row">zh-min</th><td>nan-x-zh-min</td></tr>
    //  * </tbody>
    //  * </table>
    //  *
    //  * <p>For a list of all grandfathered tags, see the
    //  * IANA Language Subtag Registry (search for "Type: grandfathered").
    //  *
    //  * <p><b>Note</b>: there is no guarantee that <code>toLanguageTag</code>
    //  * and <code>forLanguageTag</code> will round-trip.
    //  *
    //  * @param languageTag the language tag
    //  * @return The locale that best represents the language tag.
    //  * @throws NullPointerException if <code>languageTag</code> is <code>null</code>
    //  * @see #toLanguageTag()
    //  * @see java.util.Locale.Builder#setLanguageTag(string)
    //  */
    // static Locale forLanguageTag(string languageTag) {
    //     LanguageTag tag = LanguageTag.parse(languageTag, null);
    //     InternalLocaleBuilder bldr = new InternalLocaleBuilder();
    //     bldr.setLanguageTag(tag);
    //     BaseLocale base = bldr.getBaseLocale();
    //     LocaleExtensions exts = bldr.getLocaleExtensions();
    //     if (exts is null && base.getVariant().length() > 0) {
    //         exts = getCompatibilityExtensions(base.getLanguage(), base.getScript(),
    //                                           base.getRegion(), base.getVariant());
    //     }
    //     return getInstance(base, exts);
    // }

    // /**
    //  * Returns a three-letter abbreviation of this locale's language.
    //  * If the language matches an ISO 639-1 two-letter code, the
    //  * corresponding ISO 639-2/T three-letter lowercase code is
    //  * returned.  The ISO 639-2 language codes can be found on-line,
    //  * see "Codes for the Representation of Names of Languages Part 2:
    //  * Alpha-3 Code".  If the locale specifies a three-letter
    //  * language, the language is returned as is.  If the locale does
    //  * not specify a language the empty string is returned.
    //  *
    //  * @return A three-letter abbreviation of this locale's language.
    //  * @exception MissingResourceException Throws MissingResourceException if
    //  * three-letter language abbreviation is not available for this locale.
    //  */
    // string getISO3Language() throws MissingResourceException {
    //     string lang = language;
    //     if (lang.length() == 3) {
    //         return lang;
    //     }

    //     string language3 = getISO3Code(lang, LocaleISOData.isoLanguageTable);
    //     if (language3 is null) {
    //         throw new MissingResourceException("Couldn't find 3-letter language code for "
    //                 + lang, "FormatData_" ~ toString(), "ShortLanguage");
    //     }
    //     return language3;
    // }

    // /**
    //  * Returns a three-letter abbreviation for this locale's country.
    //  * If the country matches an ISO 3166-1 alpha-2 code, the
    //  * corresponding ISO 3166-1 alpha-3 uppercase code is returned.
    //  * If the locale doesn't specify a country, this will be the empty
    //  * string.
    //  *
    //  * <p>The ISO 3166-1 codes can be found on-line.
    //  *
    //  * @return A three-letter abbreviation of this locale's country.
    //  * @exception MissingResourceException Throws MissingResourceException if the
    //  * three-letter country abbreviation is not available for this locale.
    //  */
    // string getISO3Country() throws MissingResourceException {
    //     string country3 = getISO3Code(region, LocaleISOData.isoCountryTable);
    //     if (country3 is null) {
    //         throw new MissingResourceException("Couldn't find 3-letter country code for "
    //                 + region, "FormatData_" ~ toString(), "ShortCountry");
    //     }
    //     return country3;
    // }

    // private static string getISO3Code(string iso2Code, string table) {
    //     int codeLength = iso2Code.length();
    //     if (codeLength == 0) {
    //         return "";
    //     }

    //     int tableLength = table.length();
    //     int index = tableLength;
    //     if (codeLength == 2) {
    //         char c1 = iso2Code[0];
    //         char c2 = iso2Code[1];
    //         for (index = 0; index < tableLength; index += 5) {
    //             if (table[index] == c1
    //                 && table[index + 1] == c2) {
    //                 break;
    //             }
    //         }
    //     }
    //     return index < tableLength ? table.substring(index + 2, index + 5) : null;
    // }

    // /**
    //  * Returns a name for the locale's language that is appropriate for display to the
    //  * user.
    //  * If possible, the name returned will be localized for the default
    //  * {@link LocaleCategory#DISPLAY DISPLAY} locale.
    //  * For example, if the locale is fr_FR and the default
    //  * {@link LocaleCategory#DISPLAY DISPLAY} locale
    //  * is en_US, getDisplayLanguage() will return "French"; if the locale is en_US and
    //  * the default {@link LocaleCategory#DISPLAY DISPLAY} locale is fr_FR,
    //  * getDisplayLanguage() will return "anglais".
    //  * If the name returned cannot be localized for the default
    //  * {@link LocaleCategory#DISPLAY DISPLAY} locale,
    //  * (say, we don't have a Japanese name for Croatian),
    //  * this function falls back on the English name, and uses the ISO code as a last-resort
    //  * value.  If the locale doesn't specify a language, this function returns the empty string.
    //  *
    //  * @return The name of the display language.
    //  */
    // final string getDisplayLanguage() {
    //     return getDisplayLanguage(getDefault(Category.DISPLAY));
    // }

    // /**
    //  * Returns a name for the locale's language that is appropriate for display to the
    //  * user.
    //  * If possible, the name returned will be localized according to inLocale.
    //  * For example, if the locale is fr_FR and inLocale
    //  * is en_US, getDisplayLanguage() will return "French"; if the locale is en_US and
    //  * inLocale is fr_FR, getDisplayLanguage() will return "anglais".
    //  * If the name returned cannot be localized according to inLocale,
    //  * (say, we don't have a Japanese name for Croatian),
    //  * this function falls back on the English name, and finally
    //  * on the ISO code as a last-resort value.  If the locale doesn't specify a language,
    //  * this function returns the empty string.
    //  *
    //  * @param inLocale The locale for which to retrieve the display language.
    //  * @return The name of the display language appropriate to the given locale.
    //  * @exception NullPointerException if <code>inLocale</code> is <code>null</code>
    //  */
    // string getDisplayLanguage(Locale inLocale) {
    //     return getDisplaystring(language, null, inLocale, DISPLAY_LANGUAGE);
    // }

    // /**
    //  * Returns a name for the locale's script that is appropriate for display to
    //  * the user. If possible, the name will be localized for the default
    //  * {@link LocaleCategory#DISPLAY DISPLAY} locale.  Returns
    //  * the empty string if this locale doesn't specify a script code.
    //  *
    //  * @return the display name of the script code for the current default
    //  *     {@link LocaleCategory#DISPLAY DISPLAY} locale
    //  */
    // string getDisplayScript() {
    //     return getDisplayScript(getDefault(Category.DISPLAY));
    // }

    // /**
    //  * Returns a name for the locale's script that is appropriate
    //  * for display to the user. If possible, the name will be
    //  * localized for the given locale. Returns the empty string if
    //  * this locale doesn't specify a script code.
    //  *
    //  * @param inLocale The locale for which to retrieve the display script.
    //  * @return the display name of the script code for the current default
    //  * {@link LocaleCategory#DISPLAY DISPLAY} locale
    //  * @throws NullPointerException if <code>inLocale</code> is <code>null</code>
    //  */
    // string getDisplayScript(Locale inLocale) {
    //     return getDisplaystring(script, null, inLocale, DISPLAY_SCRIPT);
    // }

    // /**
    //  * Returns a name for the locale's country that is appropriate for display to the
    //  * user.
    //  * If possible, the name returned will be localized for the default
    //  * {@link LocaleCategory#DISPLAY DISPLAY} locale.
    //  * For example, if the locale is fr_FR and the default
    //  * {@link LocaleCategory#DISPLAY DISPLAY} locale
    //  * is en_US, getDisplayCountry() will return "France"; if the locale is en_US and
    //  * the default {@link LocaleCategory#DISPLAY DISPLAY} locale is fr_FR,
    //  * getDisplayCountry() will return "Etats-Unis".
    //  * If the name returned cannot be localized for the default
    //  * {@link LocaleCategory#DISPLAY DISPLAY} locale,
    //  * (say, we don't have a Japanese name for Croatia),
    //  * this function falls back on the English name, and uses the ISO code as a last-resort
    //  * value.  If the locale doesn't specify a country, this function returns the empty string.
    //  *
    //  * @return The name of the country appropriate to the locale.
    //  */
    // final string getDisplayCountry() {
    //     return getDisplayCountry(getDefault(Category.DISPLAY));
    // }

    // /**
    //  * Returns a name for the locale's country that is appropriate for display to the
    //  * user.
    //  * If possible, the name returned will be localized according to inLocale.
    //  * For example, if the locale is fr_FR and inLocale
    //  * is en_US, getDisplayCountry() will return "France"; if the locale is en_US and
    //  * inLocale is fr_FR, getDisplayCountry() will return "Etats-Unis".
    //  * If the name returned cannot be localized according to inLocale.
    //  * (say, we don't have a Japanese name for Croatia),
    //  * this function falls back on the English name, and finally
    //  * on the ISO code as a last-resort value.  If the locale doesn't specify a country,
    //  * this function returns the empty string.
    //  *
    //  * @param inLocale The locale for which to retrieve the display country.
    //  * @return The name of the country appropriate to the given locale.
    //  * @exception NullPointerException if <code>inLocale</code> is <code>null</code>
    //  */
    // string getDisplayCountry(Locale inLocale) {
    //     return getDisplaystring(region, null, inLocale, DISPLAY_COUNTRY);
    // }

    // private string getDisplaystring(string code, string cat, Locale inLocale, int type) {
    //     assert(inLocale);
    //     assert(code);

    //     if (code.isEmpty()) {
    //         return "";
    //     }

    //     LocaleServiceProviderPool pool =
    //         LocaleServiceProviderPool.getPool(LocaleNameProvider.class);
    //     string rbKey = (type == DISPLAY_VARIANT ? "%%"+code : code);
    //     string result = pool.getLocalizedObject(
    //                             LocaleNameGetter.INSTANCE,
    //                             inLocale, rbKey, type, code, cat);
    //     return result !is null ? result : code;
    // }

    // /**
    //  * Returns a name for the locale's variant code that is appropriate for display to the
    //  * user.  If possible, the name will be localized for the default
    //  * {@link LocaleCategory#DISPLAY DISPLAY} locale.  If the locale
    //  * doesn't specify a variant code, this function returns the empty string.
    //  *
    //  * @return The name of the display variant code appropriate to the locale.
    //  */
    // final string getDisplayVariant() {
    //     return getDisplayVariant(getDefault(Category.DISPLAY));
    // }

    // /**
    //  * Returns a name for the locale's variant code that is appropriate for display to the
    //  * user.  If possible, the name will be localized for inLocale.  If the locale
    //  * doesn't specify a variant code, this function returns the empty string.
    //  *
    //  * @param inLocale The locale for which to retrieve the display variant code.
    //  * @return The name of the display variant code appropriate to the given locale.
    //  * @exception NullPointerException if <code>inLocale</code> is <code>null</code>
    //  */
    // string getDisplayVariant(Locale inLocale) {
    //     if (variant.length() == 0)
    //         return "";

    //     LocaleResources lr = LocaleProviderAdapter
    //         .getResourceBundleBased()
    //         .getLocaleResources(inLocale);

    //     string names[] = getDisplayVariantArray(inLocale);

    //     // Get the localized patterns for formatting a list, and use
    //     // them to format the list.
    //     return formatList(names,
    //                       lr.getLocaleName("ListCompositionPattern"));
    // }

    // /**
    //  * Returns a name for the locale that is appropriate for display to the
    //  * user. This will be the values returned by getDisplayLanguage(),
    //  * getDisplayScript(), getDisplayCountry(), getDisplayVariant() and
    //  * optional <a href="./Locale.html#def_locale_extension">Unicode extensions</a>
    //  * assembled into a single string. The non-empty values are used in order, with
    //  * the second and subsequent names in parentheses.  For example:
    //  * <blockquote>
    //  * language (script, country, variant(, extension)*)<br>
    //  * language (country(, extension)*)<br>
    //  * language (variant(, extension)*)<br>
    //  * script (country(, extension)*)<br>
    //  * country (extension)*<br>
    //  * </blockquote>
    //  * depending on which fields are specified in the locale. The field
    //  * separator in the above parentheses, denoted as a comma character, may
    //  * be localized depending on the locale. If the language, script, country,
    //  * and variant fields are all empty, this function returns the empty string.
    //  *
    //  * @return The name of the locale appropriate to display.
    //  */
    // final string getDisplayName() {
    //     return getDisplayName(getDefault(Category.DISPLAY));
    // }

    // /**
    //  * Returns a name for the locale that is appropriate for display
    //  * to the user.  This will be the values returned by
    //  * getDisplayLanguage(), getDisplayScript(),getDisplayCountry()
    //  * getDisplayVariant(), and optional <a href="./Locale.html#def_locale_extension">
    //  * Unicode extensions</a> assembled into a single string. The non-empty
    //  * values are used in order, with the second and subsequent names in
    //  * parentheses.  For example:
    //  * <blockquote>
    //  * language (script, country, variant(, extension)*)<br>
    //  * language (country(, extension)*)<br>
    //  * language (variant(, extension)*)<br>
    //  * script (country(, extension)*)<br>
    //  * country (extension)*<br>
    //  * </blockquote>
    //  * depending on which fields are specified in the locale. The field
    //  * separator in the above parentheses, denoted as a comma character, may
    //  * be localized depending on the locale. If the language, script, country,
    //  * and variant fields are all empty, this function returns the empty string.
    //  *
    //  * @param inLocale The locale for which to retrieve the display name.
    //  * @return The name of the locale appropriate to display.
    //  * @throws NullPointerException if <code>inLocale</code> is <code>null</code>
    //  */
    // string getDisplayName(Locale inLocale) {
    //     LocaleResources lr =  LocaleProviderAdapter
    //         .getResourceBundleBased()
    //         .getLocaleResources(inLocale);

    //     string languageName = getDisplayLanguage(inLocale);
    //     string scriptName = getDisplayScript(inLocale);
    //     string countryName = getDisplayCountry(inLocale);
    //     string[] variantNames = getDisplayVariantArray(inLocale);

    //     // Get the localized patterns for formatting a display name.
    //     string displayNamePattern = lr.getLocaleName("DisplayNamePattern");
    //     string listCompositionPattern = lr.getLocaleName("ListCompositionPattern");

    //     // The display name consists of a main name, followed by qualifiers.
    //     // Typically, the format is "MainName (Qualifier, Qualifier)" but this
    //     // depends on what pattern is stored in the display locale.
    //     string   mainName       = null;
    //     string[] qualifierNames = null;

    //     // The main name is the language, or if there is no language, the script,
    //     // then if no script, the country. If there is no language/script/country
    //     // (an anomalous situation) then the display name is simply the variant's
    //     // display name.
    //     if (languageName.length() == 0 && scriptName.length() == 0 && countryName.length() == 0) {
    //         if (variantNames.length == 0) {
    //             return "";
    //         } else {
    //             return formatList(variantNames, listCompositionPattern);
    //         }
    //     }
    //     ArrayList<string> names = new ArrayList<>(4);
    //     if (languageName.length() != 0) {
    //         names.add(languageName);
    //     }
    //     if (scriptName.length() != 0) {
    //         names.add(scriptName);
    //     }
    //     if (countryName.length() != 0) {
    //         names.add(countryName);
    //     }
    //     if (variantNames.length != 0) {
    //         names.addAll(Arrays.asList(variantNames));
    //     }

    //     // add Unicode extensions
    //     if (localeExtensions !is null) {
    //         localeExtensions.getUnicodeLocaleAttributes().stream()
    //             .map(key -> getDisplaystring(key, null, inLocale, DISPLAY_UEXT_KEY))
    //             .forEach(names::add);
    //         localeExtensions.getUnicodeLocaleKeys().stream()
    //             .map(key -> getDisplayKeyTypeExtensionstring(key, lr, inLocale))
    //             .forEach(names::add);
    //     }

    //     // The first one in the main name
    //     mainName = names.get(0);

    //     // Others are qualifiers
    //     int numNames = names.size();
    //     qualifierNames = (numNames > 1) ?
    //             names.subList(1, numNames).toArray(new string[numNames - 1]) : new string[0];

    //     // Create an array whose first element is the number of remaining
    //     // elements.  This serves as a selector into a ChoiceFormat pattern from
    //     // the resource.  The second and third elements are the main name and
    //     // the qualifier; if there are no qualifiers, the third element is
    //     // unused by the format pattern.
    //     Object[] displayNames = {
    //         qualifierNames.length != 0 ? 2 : 1,
    //         mainName,
    //         // We could also just call formatList() and have it handle the empty
    //         // list case, but this is more efficient, and we want it to be
    //         // efficient since all the language-only locales will not have any
    //         // qualifiers.
    //         qualifierNames.length != 0 ? formatList(qualifierNames, listCompositionPattern) : null
    //     };

    //     if (displayNamePattern !is null) {
    //         return new MessageFormat(displayNamePattern).format(displayNames);
    //     }
    //     else {
    //         // If we cannot get the message format pattern, then we use a simple
    //         // hard-coded pattern.  This should not occur in practice unless the
    //         // installation is missing some core files (FormatData etc.).
    //         StringBuilder result = new StringBuilder();
    //         result.append((string)displayNames[1]);
    //         if (displayNames.length > 2) {
    //             result.append(" (");
    //             result.append((string)displayNames[2]);
    //             result.append(')');
    //         }
    //         return result.toString();
    //     }
    // }

    // /**
    //  * Overrides Cloneable.
    //  */
    // override
    // Object clone()
    // {
    //     try {
    //         Locale that = (Locale)super.clone();
    //         return that;
    //     } catch (CloneNotSupportedException e) {
    //         throw new InternalError(e);
    //     }
    // }

    // /**
    //  * Override hashCode.
    //  * Since Locales are often used in hashtables, caches the value
    //  * for speed.
    //  */
    // override
    // int hashCode() {
    //     int hc = hashCodeValue;
    //     if (hc == 0) {
    //         hc = baseLocale.hashCode();
    //         if (localeExtensions !is null) {
    //             hc ^= localeExtensions.hashCode();
    //         }
    //         hashCodeValue = hc;
    //     }
    //     return hc;
    // }

    // // Overrides

    // /**
    //  * Returns true if this Locale is equal to another object.  A Locale is
    //  * deemed equal to another Locale with identical language, script, country,
    //  * variant and extensions, and unequal to all other objects.
    //  *
    //  * @return true if this Locale is equal to the specified object.
    //  */
    // override
    // bool equals(Object obj) {
    //     if (this is obj)                      // quick check
    //         return true;
    //     if (!(obj instanceof Locale))
    //         return false;
    //     BaseLocale otherBase = ((Locale)obj).baseLocale;
    //     if (!baseLocale.equals(otherBase)) {
    //         return false;
    //     }
    //     if (localeExtensions is null) {
    //         return ((Locale)obj).localeExtensions is null;
    //     }
    //     return localeExtensions.equals(((Locale)obj).localeExtensions);
    // }

    // // ================= privates =====================================

    // private BaseLocale baseLocale;
    // private LocaleExtensions localeExtensions;

    /**
     * Calculated hashcode
     */
    private int hashCodeValue;

    // private __gshared Locale _defaultLocale;
    private __gshared Locale defaultDisplayLocale;
    private __gshared Locale defaultFormatLocale;

    private string languageTag;

    // /**
    //  * Return an array of the display names of the variant.
    //  * @param bundle the ResourceBundle to use to get the display names
    //  * @return an array of display names, possible of zero length.
    //  */
    // private string[] getDisplayVariantArray(Locale inLocale) {
    //     // Split the variant name into tokens separated by '_'.
    //     stringTokenizer tokenizer = new stringTokenizer(variant, "_");
    //     string[] names = new string[tokenizer.countTokens()];

    //     // For each variant token, lookup the display name.  If
    //     // not found, use the variant name itself.
    //     for (int i=0; i<names.length; ++i) {
    //         names[i] = getDisplaystring(tokenizer.nextToken(), null,
    //                             inLocale, DISPLAY_VARIANT);
    //     }

    //     return names;
    // }

    // private string getDisplayKeyTypeExtensionstring(string key, LocaleResources lr, Locale inLocale) {
    //     string type = localeExtensions.getUnicodeLocaleType(key);
    //     string ret = getDisplaystring(type, key, inLocale, DISPLAY_UEXT_TYPE);

    //     if (ret is null || ret.equals(type)) {
    //         // no localization for this type. try combining key/type separately
    //         string displayType = type;
    //         switch (key) {
    //         case "cu":
    //             displayType = lr.getCurrencyName(type.toLowerCase(Locale.ROOT));
    //             break;
    //         case "rg":
    //             if (type !is null &&
    //                 // UN M.49 code should not be allowed here
    //                 type.matches("^[a-zA-Z]{2}[zZ]{4}$")) {
    //                     displayType = lr.getLocaleName(type.substring(0, 2).toUpperCase(Locale.ROOT));
    //             }
    //             break;
    //         case "tz":
    //             displayType = TimeZoneNameUtility.convertLDMLShortID(type)
    //                 .map(id -> TimeZoneNameUtility.retrieveGenericDisplayName(id, TimeZone.LONG, inLocale))
    //                 .orElse(type);
    //             break;
    //         }
    //         ret = MessageFormat.format(lr.getLocaleName("ListKeyTypePattern"),
    //             getDisplaystring(key, null, inLocale, DISPLAY_UEXT_KEY),
    //             Optional.ofNullable(displayType).orElse(type));
    //     }

    //     return ret;
    // }

    // /**
    //  * Format a list using given pattern strings.
    //  * If either of the patterns is null, then a the list is
    //  * formatted by concatenation with the delimiter ','.
    //  * @param stringList the list of strings to be formatted.
    //  * and formatting them into a list.
    //  * @param pattern should take 2 arguments for reduction
    //  * @return a string representing the list.
    //  */
    // private static string formatList(string[] stringList, string pattern) {
    //     // If we have no list patterns, compose the list in a simple,
    //     // non-localized way.
    //     if (pattern is null) {
    //         return Arrays.stream(stringList).collect(Collectors.joining(","));
    //     }

    //     switch (stringList.length) {
    //         case 0:
    //             return "";
    //         case 1:
    //             return stringList[0];
    //         default:
    //             return Arrays.stream(stringList).reduce("",
    //                 (s1, s2) -> {
    //                     if (s1.equals("")) {
    //                         return s2;
    //                     }
    //                     if (s2.equals("")) {
    //                         return s1;
    //                     }
    //                     return MessageFormat.format(pattern, s1, s2);
    //                 });
    //     }
    // }

    // // Duplicate of sun.util.locale.UnicodeLocaleExtension.isKey in order to
    // // avoid its class loading.
    // private static bool isUnicodeExtensionKey(string s) {
    //     // 2alphanum
    //     return (s.length() == 2) && LocaleUtils.isAlphaNumericstring(s);
    // }

    // /**
    //  * @serialField language    string
    //  *      language subtag in lower case.
    //  *      (See <a href="java.base/java/util/Locale.html#getLanguage()">getLanguage()</a>)
    //  * @serialField country     string
    //  *      country subtag in upper case.
    //  *      (See <a href="java.base/java/util/Locale.html#getCountry()">getCountry()</a>)
    //  * @serialField variant     string
    //  *      variant subtags separated by LOWLINE characters.
    //  *      (See <a href="java.base/java/util/Locale.html#getVariant()">getVariant()</a>)
    //  * @serialField hashcode    int
    //  *      deprecated, for forward compatibility only
    //  * @serialField script      string
    //  *      script subtag in title case
    //  *      (See <a href="java.base/java/util/Locale.html#getScript()">getScript()</a>)
    //  * @serialField extensions  string
    //  *      canonical representation of extensions, that is,
    //  *      BCP47 extensions in alphabetical order followed by
    //  *      BCP47 private use subtags, all in lower case letters
    //  *      separated by HYPHEN-MINUS characters.
    //  *      (See <a href="java.base/java/util/Locale.html#getExtensionKeys()">getExtensionKeys()</a>,
    //  *      <a href="java.base/java/util/Locale.html#getExtension(char)">getExtension(char)</a>)
    //  */
    // private static final ObjectStreamField[] serialPersistentFields = {
    //     new ObjectStreamField("language", string.class),
    //     new ObjectStreamField("country", string.class),
    //     new ObjectStreamField("variant", string.class),
    //     new ObjectStreamField("hashcode", int.class),
    //     new ObjectStreamField("script", string.class),
    //     new ObjectStreamField("extensions", string.class),
    // };

    // /**
    //  * Serializes this <code>Locale</code> to the specified <code>ObjectOutputStream</code>.
    //  * @param out the <code>ObjectOutputStream</code> to write
    //  * @throws IOException
    //  */
    // private void writeObject(ObjectOutputStream out) throws IOException {
    //     ObjectOutputStream.PutField fields = out.putFields();
    //     fields.put("language", language);
    //     fields.put("script", script);
    //     fields.put("country", region);
    //     fields.put("variant", variant);
    //     fields.put("extensions", localeExtensions is null ? "" : localeExtensions.getID());
    //     fields.put("hashcode", -1); // place holder just for backward support
    //     out.writeFields();
    // }

    // /**
    //  * Deserializes this <code>Locale</code>.
    //  * @param in the <code>ObjectInputStream</code> to read
    //  * @throws IOException
    //  * @throws ClassNotFoundException
    //  * @throws IllformedLocaleException
    //  */
    // private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
    //     ObjectInputStream.GetField fields = in.readFields();
    //     string language = (string)fields.get("language", "");
    //     string script = (string)fields.get("script", "");
    //     string country = (string)fields.get("country", "");
    //     string variant = (string)fields.get("variant", "");
    //     string extStr = (string)fields.get("extensions", "");
    //     baseLocale = BaseLocale.getInstance(convertOldISOCodes(language), script, country, variant);
    //     if (extStr.length() > 0) {
    //         try {
    //             InternalLocaleBuilder bldr = new InternalLocaleBuilder();
    //             bldr.setExtensions(extStr);
    //             localeExtensions = bldr.getLocaleExtensions();
    //         } catch (LocaleSyntaxException e) {
    //             throw new IllformedLocaleException(e.getMessage());
    //         }
    //     } else {
    //         localeExtensions = null;
    //     }
    // }

    // /**
    //  * Returns a cached <code>Locale</code> instance equivalent to
    //  * the deserialized <code>Locale</code>. When serialized
    //  * language, country and variant fields read from the object data stream
    //  * are exactly "ja", "JP", "JP" or "th", "TH", "TH" and script/extensions
    //  * fields are empty, this method supplies <code>UNICODE_LOCALE_EXTENSION</code>
    //  * "ca"/"japanese" (calendar type is "japanese") or "nu"/"thai" (number script
    //  * type is "thai"). See <a href="Locale.html#special_cases_constructor">Special Cases</a>
    //  * for more information.
    //  *
    //  * @return an instance of <code>Locale</code> equivalent to
    //  * the deserialized <code>Locale</code>.
    //  * @throws java.io.ObjectStreamException
    //  */
    // private Object readResolve() throws java.io.ObjectStreamException {
    //     return getInstance(language, script,
    //             region, variant, localeExtensions);
    // }

    // private static string[] isoLanguages;

    // private static string[] isoCountries;

    private static string convertOldISOCodes(string language) {
        // we accept both the old and the new ISO codes for the languages whose ISO
        // codes have changed, but we always store the OLD code, for backward compatibility
        language = language.toLower();
        if (language == "he") {
            return "iw";
        } else if (language == "yi") {
            return "ji";
        } else if (language == "id") {
            return "in";
        } else {
            return language;
        }
    }

    // private static LocaleExtensions getCompatibilityExtensions(string language,
    //                                                            string script,
    //                                                            string country,
    //                                                            string variant) {
    //     LocaleExtensions extensions = null;
    //     // Special cases for backward compatibility support
    //     if (LocaleUtils.caseIgnoreMatch(language, "ja")
    //             && script.length() == 0
    //             && LocaleUtils.caseIgnoreMatch(country, "jp")
    //             && "JP".equals(variant)) {
    //         // ja_JP_JP -> u-ca-japanese (calendar = japanese)
    //         extensions = LocaleExtensions.CALENDAR_JAPANESE;
    //     } else if (LocaleUtils.caseIgnoreMatch(language, "th")
    //             && script.length() == 0
    //             && LocaleUtils.caseIgnoreMatch(country, "th")
    //             && "TH".equals(variant)) {
    //         // th_TH_TH -> u-nu-thai (numbersystem = thai)
    //         extensions = LocaleExtensions.NUMBER_THAI;
    //     }
    //     return extensions;
    // }

    // /**
    //  * Obtains a localized locale names from a LocaleNameProvider
    //  * implementation.
    //  */
    // private static class LocaleNameGetter
    //     implements LocaleServiceProviderPool.LocalizedObjectGetter<LocaleNameProvider, string> {
    //     private static final LocaleNameGetter INSTANCE = new LocaleNameGetter();

    //     override
    //     string getObject(LocaleNameProvider localeNameProvider,
    //                             Locale locale,
    //                             string key,
    //                             Object... params) {
    //         assert params.length == 3;
    //         int type = (Integer)params[0];
    //         string code = (string)params[1];
    //         string cat = (string)params[2];

    //         switch(type) {
    //         case DISPLAY_LANGUAGE:
    //             return localeNameProvider.getDisplayLanguage(code, locale);
    //         case DISPLAY_COUNTRY:
    //             return localeNameProvider.getDisplayCountry(code, locale);
    //         case DISPLAY_VARIANT:
    //             return localeNameProvider.getDisplayVariant(code, locale);
    //         case DISPLAY_SCRIPT:
    //             return localeNameProvider.getDisplayScript(code, locale);
    //         case DISPLAY_UEXT_KEY:
    //             return localeNameProvider.getDisplayUnicodeExtensionKey(code, locale);
    //         case DISPLAY_UEXT_TYPE:
    //             return localeNameProvider.getDisplayUnicodeExtensionType(code, cat, locale);
    //         default:
    //             assert false; // shouldn't happen
    //         }

    //         return null;
    //     }
    // }

    
    // /**
    //  * <code>Builder</code> is used to build instances of <code>Locale</code>
    //  * from values configured by the setters.  Unlike the <code>Locale</code>
    //  * constructors, the <code>Builder</code> checks if a value configured by a
    //  * setter satisfies the syntax requirements defined by the <code>Locale</code>
    //  * class.  A <code>Locale</code> object created by a <code>Builder</code> is
    //  * well-formed and can be transformed to a well-formed IETF BCP 47 language tag
    //  * without losing information.
    //  *
    //  * <p><b>Note:</b> The <code>Locale</code> class does not provide any
    //  * syntactic restrictions on variant, while BCP 47 requires each variant
    //  * subtag to be 5 to 8 alphanumerics or a single numeric followed by 3
    //  * alphanumerics.  The method <code>setVariant</code> throws
    //  * <code>IllformedLocaleException</code> for a variant that does not satisfy
    //  * this restriction. If it is necessary to support such a variant, use a
    //  * Locale constructor.  However, keep in mind that a <code>Locale</code>
    //  * object created this way might lose the variant information when
    //  * transformed to a BCP 47 language tag.
    //  *
    //  * <p>The following example shows how to create a <code>Locale</code> object
    //  * with the <code>Builder</code>.
    //  * <blockquote>
    //  * <pre>
    //  *     Locale aLocale = new Builder().setLanguage("sr").setScript("Latn").setRegion("RS").build();
    //  * </pre>
    //  * </blockquote>
    //  *
    //  * <p>Builders can be reused; <code>clear()</code> resets all
    //  * fields to their default values.
    //  *
    //  * @see Locale#forLanguageTag
    //  */
    // static final class Builder {
    //     private final InternalLocaleBuilder localeBuilder;

    //     /**
    //      * Constructs an empty Builder. The default value of all
    //      * fields, extensions, and private use information is the
    //      * empty string.
    //      */
    //     Builder() {
    //         localeBuilder = new InternalLocaleBuilder();
    //     }

    //     /**
    //      * Resets the <code>Builder</code> to match the provided
    //      * <code>locale</code>.  Existing state is discarded.
    //      *
    //      * <p>All fields of the locale must be well-formed, see {@link Locale}.
    //      *
    //      * <p>Locales with any ill-formed fields cause
    //      * <code>IllformedLocaleException</code> to be thrown, except for the
    //      * following three cases which are accepted for compatibility
    //      * reasons:<ul>
    //      * <li>Locale("ja", "JP", "JP") is treated as "ja-JP-u-ca-japanese"
    //      * <li>Locale("th", "TH", "TH") is treated as "th-TH-u-nu-thai"
    //      * <li>Locale("no", "NO", "NY") is treated as "nn-NO"</ul>
    //      *
    //      * @param locale the locale
    //      * @return This builder.
    //      * @throws IllformedLocaleException if <code>locale</code> has
    //      * any ill-formed fields.
    //      * @throws NullPointerException if <code>locale</code> is null.
    //      */
    //     Builder setLocale(Locale locale) {
    //         try {
    //             localeBuilder.setLocale(locale.baseLocale, locale.localeExtensions);
    //         } catch (LocaleSyntaxException e) {
    //             throw new IllformedLocaleException(e.getMessage(), e.getErrorIndex());
    //         }
    //         return this;
    //     }

    //     /**
    //      * Resets the Builder to match the provided IETF BCP 47
    //      * language tag.  Discards the existing state.  Null and the
    //      * empty string cause the builder to be reset, like {@link
    //      * #clear}.  Grandfathered tags (see {@link
    //      * Locale#forLanguageTag}) are converted to their canonical
    //      * form before being processed.  Otherwise, the language tag
    //      * must be well-formed (see {@link Locale}) or an exception is
    //      * thrown (unlike <code>Locale.forLanguageTag</code>, which
    //      * just discards ill-formed and following portions of the
    //      * tag).
    //      *
    //      * @param languageTag the language tag
    //      * @return This builder.
    //      * @throws IllformedLocaleException if <code>languageTag</code> is ill-formed
    //      * @see Locale#forLanguageTag(string)
    //      */
    //     Builder setLanguageTag(string languageTag) {
    //         ParseStatus sts = new ParseStatus();
    //         LanguageTag tag = LanguageTag.parse(languageTag, sts);
    //         if (sts.isError()) {
    //             throw new IllformedLocaleException(sts.getErrorMessage(), sts.getErrorIndex());
    //         }
    //         localeBuilder.setLanguageTag(tag);
    //         return this;
    //     }

    //     /**
    //      * Sets the language.  If <code>language</code> is the empty string or
    //      * null, the language in this <code>Builder</code> is removed.  Otherwise,
    //      * the language must be <a href="./Locale.html#def_language">well-formed</a>
    //      * or an exception is thrown.
    //      *
    //      * <p>The typical language value is a two or three-letter language
    //      * code as defined in ISO639.
    //      *
    //      * @param language the language
    //      * @return This builder.
    //      * @throws IllformedLocaleException if <code>language</code> is ill-formed
    //      */
    //     Builder setLanguage(string language) {
    //         try {
    //             localeBuilder.setLanguage(language);
    //         } catch (LocaleSyntaxException e) {
    //             throw new IllformedLocaleException(e.getMessage(), e.getErrorIndex());
    //         }
    //         return this;
    //     }

    //     /**
    //      * Sets the script. If <code>script</code> is null or the empty string,
    //      * the script in this <code>Builder</code> is removed.
    //      * Otherwise, the script must be <a href="./Locale.html#def_script">well-formed</a> or an
    //      * exception is thrown.
    //      *
    //      * <p>The typical script value is a four-letter script code as defined by ISO 15924.
    //      *
    //      * @param script the script
    //      * @return This builder.
    //      * @throws IllformedLocaleException if <code>script</code> is ill-formed
    //      */
    //     Builder setScript(string script) {
    //         try {
    //             localeBuilder.setScript(script);
    //         } catch (LocaleSyntaxException e) {
    //             throw new IllformedLocaleException(e.getMessage(), e.getErrorIndex());
    //         }
    //         return this;
    //     }

    //     /**
    //      * Sets the region.  If region is null or the empty string, the region
    //      * in this <code>Builder</code> is removed.  Otherwise,
    //      * the region must be <a href="./Locale.html#def_region">well-formed</a> or an
    //      * exception is thrown.
    //      *
    //      * <p>The typical region value is a two-letter ISO 3166 code or a
    //      * three-digit UN M.49 area code.
    //      *
    //      * <p>The country value in the <code>Locale</code> created by the
    //      * <code>Builder</code> is always normalized to upper case.
    //      *
    //      * @param region the region
    //      * @return This builder.
    //      * @throws IllformedLocaleException if <code>region</code> is ill-formed
    //      */
    //     Builder setRegion(string region) {
    //         try {
    //             localeBuilder.setRegion(region);
    //         } catch (LocaleSyntaxException e) {
    //             throw new IllformedLocaleException(e.getMessage(), e.getErrorIndex());
    //         }
    //         return this;
    //     }

    //     /**
    //      * Sets the variant.  If variant is null or the empty string, the
    //      * variant in this <code>Builder</code> is removed.  Otherwise, it
    //      * must consist of one or more <a href="./Locale.html#def_variant">well-formed</a>
    //      * subtags, or an exception is thrown.
    //      *
    //      * <p><b>Note:</b> This method checks if <code>variant</code>
    //      * satisfies the IETF BCP 47 variant subtag's syntax requirements,
    //      * and normalizes the value to lowercase letters.  However,
    //      * the <code>Locale</code> class does not impose any syntactic
    //      * restriction on variant, and the variant value in
    //      * <code>Locale</code> is case sensitive.  To set such a variant,
    //      * use a Locale constructor.
    //      *
    //      * @param variant the variant
    //      * @return This builder.
    //      * @throws IllformedLocaleException if <code>variant</code> is ill-formed
    //      */
    //     Builder setVariant(string variant) {
    //         try {
    //             localeBuilder.setVariant(variant);
    //         } catch (LocaleSyntaxException e) {
    //             throw new IllformedLocaleException(e.getMessage(), e.getErrorIndex());
    //         }
    //         return this;
    //     }

    //     /**
    //      * Sets the extension for the given key. If the value is null or the
    //      * empty string, the extension is removed.  Otherwise, the extension
    //      * must be <a href="./Locale.html#def_extensions">well-formed</a> or an exception
    //      * is thrown.
    //      *
    //      * <p><b>Note:</b> The key {@link Locale#UNICODE_LOCALE_EXTENSION
    //      * UNICODE_LOCALE_EXTENSION} ('u') is used for the Unicode locale extension.
    //      * Setting a value for this key replaces any existing Unicode locale key/type
    //      * pairs with those defined in the extension.
    //      *
    //      * <p><b>Note:</b> The key {@link Locale#PRIVATE_USE_EXTENSION
    //      * PRIVATE_USE_EXTENSION} ('x') is used for the private use code. To be
    //      * well-formed, the value for this key needs only to have subtags of one to
    //      * eight alphanumeric characters, not two to eight as in the general case.
    //      *
    //      * @param key the extension key
    //      * @param value the extension value
    //      * @return This builder.
    //      * @throws IllformedLocaleException if <code>key</code> is illegal
    //      * or <code>value</code> is ill-formed
    //      * @see #setUnicodeLocaleKeyword(string, string)
    //      */
    //     Builder setExtension(char key, string value) {
    //         try {
    //             localeBuilder.setExtension(key, value);
    //         } catch (LocaleSyntaxException e) {
    //             throw new IllformedLocaleException(e.getMessage(), e.getErrorIndex());
    //         }
    //         return this;
    //     }

    //     /**
    //      * Sets the Unicode locale keyword type for the given key.  If the type
    //      * is null, the Unicode keyword is removed.  Otherwise, the key must be
    //      * non-null and both key and type must be <a
    //      * href="./Locale.html#def_locale_extension">well-formed</a> or an exception
    //      * is thrown.
    //      *
    //      * <p>Keys and types are converted to lower case.
    //      *
    //      * <p><b>Note</b>:Setting the 'u' extension via {@link #setExtension}
    //      * replaces all Unicode locale keywords with those defined in the
    //      * extension.
    //      *
    //      * @param key the Unicode locale key
    //      * @param type the Unicode locale type
    //      * @return This builder.
    //      * @throws IllformedLocaleException if <code>key</code> or <code>type</code>
    //      * is ill-formed
    //      * @throws NullPointerException if <code>key</code> is null
    //      * @see #setExtension(char, string)
    //      */
    //     Builder setUnicodeLocaleKeyword(string key, string type) {
    //         try {
    //             localeBuilder.setUnicodeLocaleKeyword(key, type);
    //         } catch (LocaleSyntaxException e) {
    //             throw new IllformedLocaleException(e.getMessage(), e.getErrorIndex());
    //         }
    //         return this;
    //     }

    //     /**
    //      * Adds a unicode locale attribute, if not already present, otherwise
    //      * has no effect.  The attribute must not be null and must be <a
    //      * href="./Locale.html#def_locale_extension">well-formed</a> or an exception
    //      * is thrown.
    //      *
    //      * @param attribute the attribute
    //      * @return This builder.
    //      * @throws NullPointerException if <code>attribute</code> is null
    //      * @throws IllformedLocaleException if <code>attribute</code> is ill-formed
    //      * @see #setExtension(char, string)
    //      */
    //     Builder addUnicodeLocaleAttribute(string attribute) {
    //         try {
    //             localeBuilder.addUnicodeLocaleAttribute(attribute);
    //         } catch (LocaleSyntaxException e) {
    //             throw new IllformedLocaleException(e.getMessage(), e.getErrorIndex());
    //         }
    //         return this;
    //     }

    //     /**
    //      * Removes a unicode locale attribute, if present, otherwise has no
    //      * effect.  The attribute must not be null and must be <a
    //      * href="./Locale.html#def_locale_extension">well-formed</a> or an exception
    //      * is thrown.
    //      *
    //      * <p>Attribute comparison for removal is case-insensitive.
    //      *
    //      * @param attribute the attribute
    //      * @return This builder.
    //      * @throws NullPointerException if <code>attribute</code> is null
    //      * @throws IllformedLocaleException if <code>attribute</code> is ill-formed
    //      * @see #setExtension(char, string)
    //      */
    //     Builder removeUnicodeLocaleAttribute(string attribute) {
    //         assert(attribute);
    //         try {
    //             localeBuilder.removeUnicodeLocaleAttribute(attribute);
    //         } catch (LocaleSyntaxException e) {
    //             throw new IllformedLocaleException(e.getMessage(), e.getErrorIndex());
    //         }
    //         return this;
    //     }

    //     /**
    //      * Resets the builder to its initial, empty state.
    //      *
    //      * @return This builder.
    //      */
    //     Builder clear() {
    //         localeBuilder.clear();
    //         return this;
    //     }

    //     /**
    //      * Resets the extensions to their initial, empty state.
    //      * Language, script, region and variant are unchanged.
    //      *
    //      * @return This builder.
    //      * @see #setExtension(char, string)
    //      */
    //     Builder clearExtensions() {
    //         localeBuilder.clearExtensions();
    //         return this;
    //     }

    //     /**
    //      * Returns an instance of <code>Locale</code> created from the fields set
    //      * on this builder.
    //      *
    //      * <p>This applies the conversions listed in {@link Locale#forLanguageTag}
    //      * when constructing a Locale. (Grandfathered tags are handled in
    //      * {@link #setLanguageTag}.)
    //      *
    //      * @return A Locale.
    //      */
    //     Locale build() {
    //         BaseLocale baseloc = localeBuilder.getBaseLocale();
    //         LocaleExtensions extensions = localeBuilder.getLocaleExtensions();
    //         if (extensions is null && baseloc.getVariant().length() > 0) {
    //             extensions = getCompatibilityExtensions(baseloc.getLanguage(), baseloc.getScript(),
    //                     baseloc.getRegion(), baseloc.getVariant());
    //         }
    //         return Locale.getInstance(baseloc, extensions);
    //     }
    // }

    // /**
    //  * This enum provides constants to select a filtering mode for locale
    //  * matching. Refer to <a href="http://tools.ietf.org/html/rfc4647">RFC 4647
    //  * Matching of Language Tags</a> for details.
    //  *
    //  * <p>As an example, think of two Language Priority Lists each of which
    //  * includes only one language range and a set of following language tags:
    //  *
    //  * <pre>
    //  *    de (German)
    //  *    de-DE (German, Germany)
    //  *    de-Deva (German, in Devanagari script)
    //  *    de-Deva-DE (German, in Devanagari script, Germany)
    //  *    de-DE-1996 (German, Germany, orthography of 1996)
    //  *    de-Latn-DE (German, in Latin script, Germany)
    //  *    de-Latn-DE-1996 (German, in Latin script, Germany, orthography of 1996)
    //  * </pre>
    //  *
    //  * The filtering method will behave as follows:
    //  *
    //  * <table class="striped">
    //  * <caption>Filtering method behavior</caption>
    //  * <thead>
    //  * <tr>
    //  * <th scope="col">Filtering Mode</th>
    //  * <th scope="col">Language Priority List: {@code "de-DE"}</th>
    //  * <th scope="col">Language Priority List: {@code "de-*-DE"}</th>
    //  * </tr>
    //  * </thead>
    //  * <tbody>
    //  * <tr>
    //  * <th scope="row" style="vertical-align:top">
    //  * {@link FilteringMode#AUTOSELECT_FILTERING AUTOSELECT_FILTERING}
    //  * </th>
    //  * <td style="vertical-align:top">
    //  * Performs <em>basic</em> filtering and returns {@code "de-DE"} and
    //  * {@code "de-DE-1996"}.
    //  * </td>
    //  * <td style="vertical-align:top">
    //  * Performs <em>extended</em> filtering and returns {@code "de-DE"},
    //  * {@code "de-Deva-DE"}, {@code "de-DE-1996"}, {@code "de-Latn-DE"}, and
    //  * {@code "de-Latn-DE-1996"}.
    //  * </td>
    //  * </tr>
    //  * <tr>
    //  * <th scope="row" style="vertical-align:top">
    //  * {@link FilteringMode#EXTENDED_FILTERING EXTENDED_FILTERING}
    //  * </th>
    //  * <td style="vertical-align:top">
    //  * Performs <em>extended</em> filtering and returns {@code "de-DE"},
    //  * {@code "de-Deva-DE"}, {@code "de-DE-1996"}, {@code "de-Latn-DE"}, and
    //  * {@code "de-Latn-DE-1996"}.
    //  * </td>
    //  * <td style="vertical-align:top">Same as above.</td>
    //  * </tr>
    //  * <tr>
    //  * <th scope="row" style="vertical-align:top">
    //  * {@link FilteringMode#IGNORE_EXTENDED_RANGES IGNORE_EXTENDED_RANGES}
    //  * </th>
    //  * <td style="vertical-align:top">
    //  * Performs <em>basic</em> filtering and returns {@code "de-DE"} and
    //  * {@code "de-DE-1996"}.
    //  * </td>
    //  * <td style="vertical-align:top">
    //  * Performs <em>basic</em> filtering and returns {@code null} because
    //  * nothing matches.
    //  * </td>
    //  * </tr>
    //  * <tr>
    //  * <th scope="row" style="vertical-align:top">
    //  * {@link FilteringMode#MAP_EXTENDED_RANGES MAP_EXTENDED_RANGES}
    //  * </th>
    //  * <td style="vertical-align:top">Same as above.</td>
    //  * <td style="vertical-align:top">
    //  * Performs <em>basic</em> filtering and returns {@code "de-DE"} and
    //  * {@code "de-DE-1996"} because {@code "de-*-DE"} is mapped to
    //  * {@code "de-DE"}.
    //  * </td>
    //  * </tr>
    //  * <tr>
    //  * <th scope="row" style="vertical-align:top">
    //  * {@link FilteringMode#REJECT_EXTENDED_RANGES REJECT_EXTENDED_RANGES}
    //  * </th>
    //  * <td style="vertical-align:top">Same as above.</td>
    //  * <td style="vertical-align:top">
    //  * Throws {@link IllegalArgumentException} because {@code "de-*-DE"} is
    //  * not a valid basic language range.
    //  * </td>
    //  * </tr>
    //  * </tbody>
    //  * </table>
    //  *
    //  * @see #filter(List, Collection, FilteringMode)
    //  * @see #filterTags(List, Collection, FilteringMode)
    //  *
    //  */
    // static enum FilteringMode {
    //     /**
    //      * Specifies automatic filtering mode based on the given Language
    //      * Priority List consisting of language ranges. If all of the ranges
    //      * are basic, basic filtering is selected. Otherwise, extended
    //      * filtering is selected.
    //      */
    //     AUTOSELECT_FILTERING,

    //     /**
    //      * Specifies extended filtering.
    //      */
    //     EXTENDED_FILTERING,

    //     /**
    //      * Specifies basic filtering: Note that any extended language ranges
    //      * included in the given Language Priority List are ignored.
    //      */
    //     IGNORE_EXTENDED_RANGES,

    //     /**
    //      * Specifies basic filtering: If any extended language ranges are
    //      * included in the given Language Priority List, they are mapped to the
    //      * basic language range. Specifically, a language range starting with a
    //      * subtag {@code "*"} is treated as a language range {@code "*"}. For
    //      * example, {@code "*-US"} is treated as {@code "*"}. If {@code "*"} is
    //      * not the first subtag, {@code "*"} and extra {@code "-"} are removed.
    //      * For example, {@code "ja-*-JP"} is mapped to {@code "ja-JP"}.
    //      */
    //     MAP_EXTENDED_RANGES,

    //     /**
    //      * Specifies basic filtering: If any extended language ranges are
    //      * included in the given Language Priority List, the list is rejected
    //      * and the filtering method throws {@link IllegalArgumentException}.
    //      */
    //     REJECT_EXTENDED_RANGES
    // };

    // /**
    //  * This class expresses a <em>Language Range</em> defined in
    //  * <a href="http://tools.ietf.org/html/rfc4647">RFC 4647 Matching of
    //  * Language Tags</a>. A language range is an identifier which is used to
    //  * select language tag(s) meeting specific requirements by using the
    //  * mechanisms described in <a href="Locale.html#LocaleMatching">Locale
    //  * Matching</a>. A list which represents a user's preferences and consists
    //  * of language ranges is called a <em>Language Priority List</em>.
    //  *
    //  * <p>There are two types of language ranges: basic and extended. In RFC
    //  * 4647, the syntax of language ranges is expressed in
    //  * <a href="http://tools.ietf.org/html/rfc4234">ABNF</a> as follows:
    //  * <blockquote>
    //  * <pre>
    //  *     basic-language-range    = (1*8ALPHA *("-" 1*8alphanum)) / "*"
    //  *     extended-language-range = (1*8ALPHA / "*")
    //  *                               *("-" (1*8alphanum / "*"))
    //  *     alphanum                = ALPHA / DIGIT
    //  * </pre>
    //  * </blockquote>
    //  * For example, {@code "en"} (English), {@code "ja-JP"} (Japanese, Japan),
    //  * {@code "*"} (special language range which matches any language tag) are
    //  * basic language ranges, whereas {@code "*-CH"} (any languages,
    //  * Switzerland), {@code "es-*"} (Spanish, any regions), and
    //  * {@code "zh-Hant-*"} (Traditional Chinese, any regions) are extended
    //  * language ranges.
    //  *
    //  * @see #filter
    //  * @see #filterTags
    //  * @see #lookup
    //  * @see #lookupTag
    //  *
    //  */
    // static final class LanguageRange {

    //    /**
    //     * A constant holding the maximum value of weight, 1.0, which indicates
    //     * that the language range is a good fit for the user.
    //     */
    //     static final double MAX_WEIGHT = 1.0;

    //    /**
    //     * A constant holding the minimum value of weight, 0.0, which indicates
    //     * that the language range is not a good fit for the user.
    //     */
    //     static final double MIN_WEIGHT = 0.0;

    //     private final string range;
    //     private final double weight;

    //     private int hash;

    //     /**
    //      * Constructs a {@code LanguageRange} using the given {@code range}.
    //      * Note that no validation is done against the IANA Language Subtag
    //      * Registry at time of construction.
    //      *
    //      * <p>This is equivalent to {@code LanguageRange(range, MAX_WEIGHT)}.
    //      *
    //      * @param range a language range
    //      * @throws NullPointerException if the given {@code range} is
    //      *     {@code null}
    //      * @throws IllegalArgumentException if the given {@code range} does not
    //      * comply with the syntax of the language range mentioned in RFC 4647
    //      */
    //     LanguageRange(string range) {
    //         this(range, MAX_WEIGHT);
    //     }

    //     /**
    //      * Constructs a {@code LanguageRange} using the given {@code range} and
    //      * {@code weight}. Note that no validation is done against the IANA
    //      * Language Subtag Registry at time of construction.
    //      *
    //      * @param range  a language range
    //      * @param weight a weight value between {@code MIN_WEIGHT} and
    //      *     {@code MAX_WEIGHT}
    //      * @throws NullPointerException if the given {@code range} is
    //      *     {@code null}
    //      * @throws IllegalArgumentException if the given {@code range} does not
    //      * comply with the syntax of the language range mentioned in RFC 4647
    //      * or if the given {@code weight} is less than {@code MIN_WEIGHT}
    //      * or greater than {@code MAX_WEIGHT}
    //      */
    //     LanguageRange(string range, double weight) {
    //         if (range is null) {
    //             throw new NullPointerException();
    //         }
    //         if (weight < MIN_WEIGHT || weight > MAX_WEIGHT) {
    //             throw new IllegalArgumentException("weight=" ~ weight);
    //         }

    //         range = range.toLowerCase(Locale.ROOT);

    //         // Do syntax check.
    //         bool isIllFormed = false;
    //         string[] subtags = range.split("-");
    //         if (isSubtagIllFormed(subtags[0], true)
    //             || range.endsWith("-")) {
    //             isIllFormed = true;
    //         } else {
    //             for (int i = 1; i < subtags.length; i++) {
    //                 if (isSubtagIllFormed(subtags[i], false)) {
    //                     isIllFormed = true;
    //                     break;
    //                 }
    //             }
    //         }
    //         if (isIllFormed) {
    //             throw new IllegalArgumentException("range=" ~ range);
    //         }

    //         this.range = range;
    //         this.weight = weight;
    //     }

    //     private static bool isSubtagIllFormed(string subtag,
    //                                              bool isFirstSubtag) {
    //         if (subtag.equals("") || subtag.length() > 8) {
    //             return true;
    //         } else if (subtag.equals("*")) {
    //             return false;
    //         }
    //         char[] charArray = subtag.toCharArray();
    //         if (isFirstSubtag) { // ALPHA
    //             for (char c : charArray) {
    //                 if (c < 'a' || c > 'z') {
    //                     return true;
    //                 }
    //             }
    //         } else { // ALPHA / DIGIT
    //             for (char c : charArray) {
    //                 if (c < '0' || (c > '9' && c < 'a') || c > 'z') {
    //                     return true;
    //                 }
    //             }
    //         }
    //         return false;
    //     }

    //     /**
    //      * Returns the language range of this {@code LanguageRange}.
    //      *
    //      * @return the language range.
    //      */
    //     string getRange() {
    //         return range;
    //     }

    //     /**
    //      * Returns the weight of this {@code LanguageRange}.
    //      *
    //      * @return the weight value.
    //      */
    //     double getWeight() {
    //         return weight;
    //     }

    //     /**
    //      * Parses the given {@code ranges} to generate a Language Priority List.
    //      *
    //      * <p>This method performs a syntactic check for each language range in
    //      * the given {@code ranges} but doesn't do validation using the IANA
    //      * Language Subtag Registry.
    //      *
    //      * <p>The {@code ranges} to be given can take one of the following
    //      * forms:
    //      *
    //      * <pre>
    //      *   "Accept-Language: ja,en;q=0.4"  (weighted list with Accept-Language prefix)
    //      *   "ja,en;q=0.4"                   (weighted list)
    //      *   "ja,en"                         (prioritized list)
    //      * </pre>
    //      *
    //      * In a weighted list, each language range is given a weight value.
    //      * The weight value is identical to the "quality value" in
    //      * <a href="http://tools.ietf.org/html/rfc2616">RFC 2616</a>, and it
    //      * expresses how much the user prefers  the language. A weight value is
    //      * specified after a corresponding language range followed by
    //      * {@code ";q="}, and the default weight value is {@code MAX_WEIGHT}
    //      * when it is omitted.
    //      *
    //      * <p>Unlike a weighted list, language ranges in a prioritized list
    //      * are sorted in the descending order based on its priority. The first
    //      * language range has the highest priority and meets the user's
    //      * preference most.
    //      *
    //      * <p>In either case, language ranges are sorted in descending order in
    //      * the Language Priority List based on priority or weight. If a
    //      * language range appears in the given {@code ranges} more than once,
    //      * only the first one is included on the Language Priority List.
    //      *
    //      * <p>The returned list consists of language ranges from the given
    //      * {@code ranges} and their equivalents found in the IANA Language
    //      * Subtag Registry. For example, if the given {@code ranges} is
    //      * {@code "Accept-Language: iw,en-us;q=0.7,en;q=0.3"}, the elements in
    //      * the list to be returned are:
    //      *
    //      * <pre>
    //      *  <b>Range</b>                                   <b>Weight</b>
    //      *    "iw" (older tag for Hebrew)             1.0
    //      *    "he" (new preferred code for Hebrew)    1.0
    //      *    "en-us" (English, United States)        0.7
    //      *    "en" (English)                          0.3
    //      * </pre>
    //      *
    //      * Two language ranges, {@code "iw"} and {@code "he"}, have the same
    //      * highest priority in the list. By adding {@code "he"} to the user's
    //      * Language Priority List, locale-matching method can find Hebrew as a
    //      * matching locale (or language tag) even if the application or system
    //      * offers only {@code "he"} as a supported locale (or language tag).
    //      *
    //      * @param ranges a list of comma-separated language ranges or a list of
    //      *     language ranges in the form of the "Accept-Language" header
    //      *     defined in <a href="http://tools.ietf.org/html/rfc2616">RFC
    //      *     2616</a>
    //      * @return a Language Priority List consisting of language ranges
    //      *     included in the given {@code ranges} and their equivalent
    //      *     language ranges if available. The list is modifiable.
    //      * @throws NullPointerException if {@code ranges} is null
    //      * @throws IllegalArgumentException if a language range or a weight
    //      *     found in the given {@code ranges} is ill-formed
    //      */
    //     static List<LanguageRange> parse(string ranges) {
    //         return LocaleMatcher.parse(ranges);
    //     }

    //     /**
    //      * Parses the given {@code ranges} to generate a Language Priority
    //      * List, and then customizes the list using the given {@code map}.
    //      * This method is equivalent to
    //      * {@code mapEquivalents(parse(ranges), map)}.
    //      *
    //      * @param ranges a list of comma-separated language ranges or a list
    //      *     of language ranges in the form of the "Accept-Language" header
    //      *     defined in <a href="http://tools.ietf.org/html/rfc2616">RFC
    //      *     2616</a>
    //      * @param map a map containing information to customize language ranges
    //      * @return a Language Priority List with customization. The list is
    //      *     modifiable.
    //      * @throws NullPointerException if {@code ranges} is null
    //      * @throws IllegalArgumentException if a language range or a weight
    //      *     found in the given {@code ranges} is ill-formed
    //      * @see #parse(string)
    //      * @see #mapEquivalents
    //      */
    //     static List<LanguageRange> parse(string ranges,
    //                                             Map<string, List<string>> map) {
    //         return mapEquivalents(parse(ranges), map);
    //     }

    //     /**
    //      * Generates a new customized Language Priority List using the given
    //      * {@code priorityList} and {@code map}. If the given {@code map} is
    //      * empty, this method returns a copy of the given {@code priorityList}.
    //      *
    //      * <p>In the map, a key represents a language range whereas a value is
    //      * a list of equivalents of it. {@code '*'} cannot be used in the map.
    //      * Each equivalent language range has the same weight value as its
    //      * original language range.
    //      *
    //      * <pre>
    //      *  An example of map:
    //      *    <b>Key</b>                            <b>Value</b>
    //      *      "zh" (Chinese)                 "zh",
    //      *                                     "zh-Hans"(Simplified Chinese)
    //      *      "zh-HK" (Chinese, Hong Kong)   "zh-HK"
    //      *      "zh-TW" (Chinese, Taiwan)      "zh-TW"
    //      * </pre>
    //      *
    //      * The customization is performed after modification using the IANA
    //      * Language Subtag Registry.
    //      *
    //      * <p>For example, if a user's Language Priority List consists of five
    //      * language ranges ({@code "zh"}, {@code "zh-CN"}, {@code "en"},
    //      * {@code "zh-TW"}, and {@code "zh-HK"}), the newly generated Language
    //      * Priority List which is customized using the above map example will
    //      * consists of {@code "zh"}, {@code "zh-Hans"}, {@code "zh-CN"},
    //      * {@code "zh-Hans-CN"}, {@code "en"}, {@code "zh-TW"}, and
    //      * {@code "zh-HK"}.
    //      *
    //      * <p>{@code "zh-HK"} and {@code "zh-TW"} aren't converted to
    //      * {@code "zh-Hans-HK"} nor {@code "zh-Hans-TW"} even if they are
    //      * included in the Language Priority List. In this example, mapping
    //      * is used to clearly distinguish Simplified Chinese and Traditional
    //      * Chinese.
    //      *
    //      * <p>If the {@code "zh"}-to-{@code "zh"} mapping isn't included in the
    //      * map, a simple replacement will be performed and the customized list
    //      * won't include {@code "zh"} and {@code "zh-CN"}.
    //      *
    //      * @param priorityList user's Language Priority List
    //      * @param map a map containing information to customize language ranges
    //      * @return a new Language Priority List with customization. The list is
    //      *     modifiable.
    //      * @throws NullPointerException if {@code priorityList} is {@code null}
    //      * @see #parse(string, Map)
    //      */
    //     static List<LanguageRange> mapEquivalents(
    //                                           List<LanguageRange>priorityList,
    //                                           Map<string, List<string>> map) {
    //         return LocaleMatcher.mapEquivalents(priorityList, map);
    //     }

    //     /**
    //      * Returns a hash code value for the object.
    //      *
    //      * @return  a hash code value for this object.
    //      */
    //     override
    //     int hashCode() {
    //         int h = hash;
    //         if (h == 0) {
    //             h = 17;
    //             h = 37*h + range.hashCode();
    //             long bitsWeight = Double.doubleToLongBits(weight);
    //             h = 37*h + (int)(bitsWeight ^ (bitsWeight >>> 32));
    //             if (h != 0) {
    //                 hash = h;
    //             }
    //         }
    //         return h;
    //     }

    //     /**
    //      * Compares this object to the specified object. The result is true if
    //      * and only if the argument is not {@code null} and is a
    //      * {@code LanguageRange} object that contains the same {@code range}
    //      * and {@code weight} values as this object.
    //      *
    //      * @param obj the object to compare with
    //      * @return  {@code true} if this object's {@code range} and
    //      *     {@code weight} are the same as the {@code obj}'s; {@code false}
    //      *     otherwise.
    //      */
    //     override
    //     bool equals(Object obj) {
    //         if (this is obj) {
    //             return true;
    //         }
    //         if (!(obj instanceof LanguageRange)) {
    //             return false;
    //         }
    //         LanguageRange other = (LanguageRange)obj;
    //         return hash == other.hash
    //                && range.equals(other.range)
    //                && weight == other.weight;
    //     }

    //     /**
    //      * Returns an informative string representation of this {@code LanguageRange}
    //      * object, consisting of language range and weight if the range is
    //      * weighted and the weight is less than the max weight.
    //      *
    //      * @return a string representation of this {@code LanguageRange} object.
    //      */
    //     override
    //     string toString() {
    //         return (weight == MAX_WEIGHT) ? range : range ~ ";q=" ~ weight;
    //     }
    // }

    // /**
    //  * Returns a list of matching {@code Locale} instances using the filtering
    //  * mechanism defined in RFC 4647.
    //  *
    //  * This filter operation on the given {@code locales} ensures that only
    //  * unique matching locale(s) are returned.
    //  *
    //  * @param priorityList user's Language Priority List in which each language
    //  *     tag is sorted in descending order based on priority or weight
    //  * @param locales {@code Locale} instances used for matching
    //  * @param mode filtering mode
    //  * @return a list of {@code Locale} instances for matching language tags
    //  *     sorted in descending order based on priority or weight, or an empty
    //  *     list if nothing matches. The list is modifiable.
    //  * @throws NullPointerException if {@code priorityList} or {@code locales}
    //  *     is {@code null}
    //  * @throws IllegalArgumentException if one or more extended language ranges
    //  *     are included in the given list when
    //  *     {@link FilteringMode#REJECT_EXTENDED_RANGES} is specified
    //  *
    //  */
    // static List<Locale> filter(List<LanguageRange> priorityList,
    //                                   Collection<Locale> locales,
    //                                   FilteringMode mode) {
    //     return LocaleMatcher.filter(priorityList, locales, mode);
    // }

    // /**
    //  * Returns a list of matching {@code Locale} instances using the filtering
    //  * mechanism defined in RFC 4647. This is equivalent to
    //  * {@link #filter(List, Collection, FilteringMode)} when {@code mode} is
    //  * {@link FilteringMode#AUTOSELECT_FILTERING}.
    //  *
    //  * This filter operation on the given {@code locales} ensures that only
    //  * unique matching locale(s) are returned.
    //  *
    //  * @param priorityList user's Language Priority List in which each language
    //  *     tag is sorted in descending order based on priority or weight
    //  * @param locales {@code Locale} instances used for matching
    //  * @return a list of {@code Locale} instances for matching language tags
    //  *     sorted in descending order based on priority or weight, or an empty
    //  *     list if nothing matches. The list is modifiable.
    //  * @throws NullPointerException if {@code priorityList} or {@code locales}
    //  *     is {@code null}
    //  *
    //  */
    // static List<Locale> filter(List<LanguageRange> priorityList,
    //                                   Collection<Locale> locales) {
    //     return filter(priorityList, locales, FilteringMode.AUTOSELECT_FILTERING);
    // }

    // /**
    //  * Returns a list of matching languages tags using the basic filtering
    //  * mechanism defined in RFC 4647.
    //  *
    //  * This filter operation on the given {@code tags} ensures that only
    //  * unique matching tag(s) are returned with preserved case. In case of
    //  * duplicate matching tags with the case difference, the first matching
    //  * tag with preserved case is returned.
    //  * For example, "de-ch" is returned out of the duplicate matching tags
    //  * "de-ch" and "de-CH", if "de-ch" is checked first for matching in the
    //  * given {@code tags}. Note that if the given {@code tags} is an unordered
    //  * {@code Collection}, the returned matching tag out of duplicate tags is
    //  * subject to change, depending on the implementation of the
    //  * {@code Collection}.
    //  *
    //  * @param priorityList user's Language Priority List in which each language
    //  *     tag is sorted in descending order based on priority or weight
    //  * @param tags language tags
    //  * @param mode filtering mode
    //  * @return a list of matching language tags sorted in descending order
    //  *     based on priority or weight, or an empty list if nothing matches.
    //  *     The list is modifiable.
    //  * @throws NullPointerException if {@code priorityList} or {@code tags} is
    //  *     {@code null}
    //  * @throws IllegalArgumentException if one or more extended language ranges
    //  *     are included in the given list when
    //  *     {@link FilteringMode#REJECT_EXTENDED_RANGES} is specified
    //  *
    //  */
    // static List<string> filterTags(List<LanguageRange> priorityList,
    //                                       Collection<string> tags,
    //                                       FilteringMode mode) {
    //     return LocaleMatcher.filterTags(priorityList, tags, mode);
    // }

    // /**
    //  * Returns a list of matching languages tags using the basic filtering
    //  * mechanism defined in RFC 4647. This is equivalent to
    //  * {@link #filterTags(List, Collection, FilteringMode)} when {@code mode}
    //  * is {@link FilteringMode#AUTOSELECT_FILTERING}.
    //  *
    //  * This filter operation on the given {@code tags} ensures that only
    //  * unique matching tag(s) are returned with preserved case. In case of
    //  * duplicate matching tags with the case difference, the first matching
    //  * tag with preserved case is returned.
    //  * For example, "de-ch" is returned out of the duplicate matching tags
    //  * "de-ch" and "de-CH", if "de-ch" is checked first for matching in the
    //  * given {@code tags}. Note that if the given {@code tags} is an unordered
    //  * {@code Collection}, the returned matching tag out of duplicate tags is
    //  * subject to change, depending on the implementation of the
    //  * {@code Collection}.
    //  *
    //  * @param priorityList user's Language Priority List in which each language
    //  *     tag is sorted in descending order based on priority or weight
    //  * @param tags language tags
    //  * @return a list of matching language tags sorted in descending order
    //  *     based on priority or weight, or an empty list if nothing matches.
    //  *     The list is modifiable.
    //  * @throws NullPointerException if {@code priorityList} or {@code tags} is
    //  *     {@code null}
    //  *
    //  */
    // static List<string> filterTags(List<LanguageRange> priorityList,
    //                                       Collection<string> tags) {
    //     return filterTags(priorityList, tags, FilteringMode.AUTOSELECT_FILTERING);
    // }

    // /**
    //  * Returns a {@code Locale} instance for the best-matching language
    //  * tag using the lookup mechanism defined in RFC 4647.
    //  *
    //  * @param priorityList user's Language Priority List in which each language
    //  *     tag is sorted in descending order based on priority or weight
    //  * @param locales {@code Locale} instances used for matching
    //  * @return the best matching <code>Locale</code> instance chosen based on
    //  *     priority or weight, or {@code null} if nothing matches.
    //  * @throws NullPointerException if {@code priorityList} or {@code tags} is
    //  *     {@code null}
    //  *
    //  */
    // static Locale lookup(List<LanguageRange> priorityList,
    //                             Collection<Locale> locales) {
    //     return LocaleMatcher.lookup(priorityList, locales);
    // }

    // /**
    //  * Returns the best-matching language tag using the lookup mechanism
    //  * defined in RFC 4647.
    //  *
    //  * This lookup operation on the given {@code tags} ensures that the
    //  * first matching tag with preserved case is returned.
    //  *
    //  * @param priorityList user's Language Priority List in which each language
    //  *     tag is sorted in descending order based on priority or weight
    //  * @param tags language tangs used for matching
    //  * @return the best matching language tag chosen based on priority or
    //  *     weight, or {@code null} if nothing matches.
    //  * @throws NullPointerException if {@code priorityList} or {@code tags} is
    //  *     {@code null}
    //  *
    //  */
    // static string lookupTag(List<LanguageRange> priorityList,
    //                                Collection<string> tags) {
    //     return LocaleMatcher.lookupTag(priorityList, tags);
    // }

}

/**
 * Enum for locale categories.  These locale categories are used to get/set
 * the default locale for the specific functionality represented by the
 * category.
 *
 * @see #getDefault(LocaleCategory)
 * @see #setDefault(LocaleCategory, Locale)
 */
struct LocaleCategory {

    /**
     * Category used to represent the default locale for
     * displaying user interfaces.
     */
   enum LocaleCategory DISPLAY = LocaleCategory("user.language.display",
            "user.script.display",
            "user.country.display",
            "user.variant.display",
            "user.extensions.display");

    /**
     * Category used to represent the default locale for
     * formatting dates, numbers, and/or currencies.
     */
   enum LocaleCategory FORMAT = LocaleCategory("user.language.format",
           "user.script.format",
           "user.country.format",
           "user.variant.format",
           "user.extensions.format");

    this(string languageKey, string scriptKey, string countryKey,
            string variantKey, string extensionsKey) {
        this.languageKey = languageKey;
        this.scriptKey = scriptKey;
        this.countryKey = countryKey;
        this.variantKey = variantKey;
        this.extensionsKey = extensionsKey;
    }

   string languageKey;
   string scriptKey;
   string countryKey;
   string variantKey;
   string extensionsKey;

   //  bool opEquals(const LocaleCategory h) nothrow {
   //      return this.languageKey == h.languageKey && 
   //       // this.scriptKey == h.scriptKey &&
   //       this.countryKey == h.countryKey;
   //  }

   //  bool opEquals(ref const LocaleCategory h) nothrow {
   //      return this.languageKey == h.languageKey && 
   //       // this.scriptKey == h.scriptKey &&
   //       this.countryKey == h.countryKey;
   //  }
}