// License: GPL. For details, see LICENSE file.
package org.openstreetmap.josm.tools;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.nio.file.InvalidPathException;
import java.text.MessageFormat;
import java.util.HashMap;
import java.util.Locale;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Stream;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;

import org.openstreetmap.josm.data.osm.TagMap;

/**
 * Internationalisation support.
 *
 * @author Immanuel.Scholz
 */
public final class I18n {

    private static final String CORE_TRANS_DIRECTORY = "/data/";
    private static final String PLUGIN_TRANS_DIRECTORY = "data/";

    /**
     * This annotates strings which do not permit a clean i18n. This is mostly due to strings
     * containing two nouns which can occur in singular or plural form.
     * <br>
     * No behaviour is associated with this annotation.
     */
    @Retention(RetentionPolicy.SOURCE)
    public @interface QuirkyPluralString {
    }

    private I18n() {
        // Hide default constructor for utils classes
    }

    /**
     * Enumeration of possible plural modes. It allows us to identify and implement logical conditions of
     * plural forms defined on <a href="https://help.launchpad.net/Translations/PluralForms">Launchpad</a>.
     * See <a href="http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html">CLDR</a>
     * for another complete list.
     * @see #pluralEval
     */
    private enum PluralMode {
        /** Plural = Not 1. This is the default for many languages, including English: 1 day, but 0 days or 2 days. */
        MODE_NOTONE,
        /** No plural. Mainly for Asian languages (Indonesian, Chinese, Japanese, ...) */
        MODE_NONE,
        /** Plural = Greater than 1. For some latin languages (French, Brazilian Portuguese) */
        MODE_GREATERONE,
        /* Special mode for
         * <a href="http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html#ar">Arabic</a>.*/
        MODE_AR,
        /** Special mode for
         * <a href="http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html#cs">Czech</a>. */
        MODE_CS,
        /** Special mode for
         * <a href="http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html#pl">Polish</a>. */
        MODE_PL,
        /* Special mode for
         * <a href="http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html#ro">Romanian</a>.*
        MODE_RO,*/
        /** Special mode for
         * <a href="http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html#lt">Lithuanian</a>. */
        MODE_LT,
        /** Special mode for
         * <a href="http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html#ru">Russian</a>. */
        MODE_RU,
        /** Special mode for
         * <a href="http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html#sk">Slovak</a>. */
        MODE_SK,
        /* Special mode for
         * <a href="http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html#sl">Slovenian</a>.*
        MODE_SL,*/
    }

    private static volatile PluralMode pluralMode = PluralMode.MODE_NOTONE; /* english default */
    private static volatile String loadedCode = "en";

    /** Map (english/locale) of singular strings **/
    private static volatile Map<String, String> strings;
    /** Map (english/locale) of plural strings **/
    private static volatile Map<String, String[]> pstrings;
    private static Locale originalLocale = Locale.getDefault();
    private static Map<String, PluralMode> languages = new HashMap<>();
    // NOTE: check also WikiLanguage handling in LanguageInfo.java when adding new languages
    static {
        languages.put("ar", PluralMode.MODE_AR);
        languages.put("ast", PluralMode.MODE_NOTONE);
        languages.put("bg", PluralMode.MODE_NOTONE);
        languages.put("be", PluralMode.MODE_RU);
        languages.put("ca", PluralMode.MODE_NOTONE);
        languages.put("ca@valencia", PluralMode.MODE_NOTONE);
        languages.put("cs", PluralMode.MODE_CS);
        languages.put("da", PluralMode.MODE_NOTONE);
        languages.put("de", PluralMode.MODE_NOTONE);
        languages.put("el", PluralMode.MODE_NOTONE);
        languages.put("en_AU", PluralMode.MODE_NOTONE);
        //languages.put("en_CA", PluralMode.MODE_NOTONE);
        languages.put("en_GB", PluralMode.MODE_NOTONE);
        languages.put("es", PluralMode.MODE_NOTONE);
        languages.put("et", PluralMode.MODE_NOTONE);
        //languages.put("eu", PluralMode.MODE_NOTONE);
        languages.put("fa", PluralMode.MODE_NONE);
        languages.put("fi", PluralMode.MODE_NOTONE);
        languages.put("fr", PluralMode.MODE_GREATERONE);
        languages.put("gl", PluralMode.MODE_NOTONE);
        //languages.put("he", PluralMode.MODE_NOTONE);
        languages.put("hu", PluralMode.MODE_NOTONE);
        languages.put("id", PluralMode.MODE_NONE);
        languages.put("is", PluralMode.MODE_NOTONE);
        languages.put("it", PluralMode.MODE_NOTONE);
        languages.put("ja", PluralMode.MODE_NONE);
        languages.put("ko", PluralMode.MODE_NONE);
        languages.put("km", PluralMode.MODE_NONE);
        languages.put("lt", PluralMode.MODE_LT);
        languages.put("mr", PluralMode.MODE_NOTONE);
        languages.put("nb", PluralMode.MODE_NOTONE);
        languages.put("nl", PluralMode.MODE_NOTONE);
        languages.put("pl", PluralMode.MODE_PL);
        languages.put("pt", PluralMode.MODE_NOTONE);
        languages.put("pt_BR", PluralMode.MODE_GREATERONE);
        //languages.put("ro", PluralMode.MODE_RO);
        languages.put("ru", PluralMode.MODE_RU);
        languages.put("sk", PluralMode.MODE_SK);
        //languages.put("sl", PluralMode.MODE_SL);
        languages.put("sr@latin", PluralMode.MODE_RU);
        languages.put("sv", PluralMode.MODE_NOTONE);
        //languages.put("tr", PluralMode.MODE_NONE);
        languages.put("uk", PluralMode.MODE_RU);
        languages.put("vi", PluralMode.MODE_NONE);
        languages.put("zh_CN", PluralMode.MODE_NONE);
        languages.put("zh_TW", PluralMode.MODE_NONE);
    }

    private static final String HIRAGANA = "hira";
    private static final String KATAKANA = "kana";
    private static final String LATIN = "latn";
    private static final String PINYIN = "pinyin";
    private static final String ROMAJI = "rm";

    // Matches ISO-639 two and three letters language codes + scripts
    private static final Pattern LANGUAGE_NAMES = Pattern.compile(
            "name:(\\p{Lower}{2,3})(?:[-_](?i:(" + String.join("|", HIRAGANA, KATAKANA, LATIN, PINYIN, ROMAJI) + ")))?");

    private static String format(String text, Object... objects) {
        if (objects.length == 0 && !text.contains("'")) {
            return text;
        }
        try {
            return MessageFormat.format(text, objects);
        } catch (InvalidPathException e) {
            System.err.println("!!! Unable to format '" + text + "': " + e.getMessage());
            e.printStackTrace();
            return null;
        }
    }

    /**
     * Translates some text for the current locale.
     * These strings are collected by a script that runs on the source code files.
     * After translation, the localizations are distributed with the main program.
     * <br>
     * For example, <code>tr("JOSM''s default value is ''{0}''.", val)</code>.
     * <br>
     * Use {@link #trn} for distinguishing singular from plural text, i.e.,
     * do not use {@code tr(size == 1 ? "singular" : "plural")} nor
     * {@code size == 1 ? tr("singular") : tr("plural")}
     *
     * @param text the text to translate.
     * Must be a string literal. (No constants or local vars.)
     * Can be broken over multiple lines.
     * An apostrophe ' must be quoted by another apostrophe.
     * @param objects the parameters for the string.
     * Mark occurrences in {@code text} with <code>{0}</code>, <code>{1}</code>, ...
     * @return the translated string.
     * @see #trn
     * @see #trc
     * @see #trnc
     */
    public static String tr(String text, Object... objects) {
        if (text == null) return null;
        return format(gettext(text, null), objects);
    }

    /**
     * Translates some text in a context for the current locale.
     * There can be different translations for the same text within different contexts.
     *
     * @param context string that helps translators to find an appropriate
     * translation for {@code text}.
     * @param text the text to translate.
     * @return the translated string.
     * @see #tr
     * @see #trn
     * @see #trnc
     */
    public static String trc(String context, String text) {
        if (context == null)
            return tr(text);
        if (text == null)
            return null;
        return format(gettext(text, context), (Object) null);
    }

    public static String trcLazy(String context, String text) {
        if (context == null)
            return tr(text);
        if (text == null)
            return null;
        return format(gettextLazy(text, context), (Object) null);
    }

    /**
     * Marks a string for translation (such that a script can harvest
     * the translatable strings from the source files).
     *
     * For example, <code>
     * String[] options = new String[] {marktr("up"), marktr("down")};
     * lbl.setText(tr(options[0]));</code>
     * @param text the string to be marked for translation.
     * @return {@code text} unmodified.
     */
    public static String marktr(String text) {
        return text;
    }

    public static String marktrc(String context, String text) {
        return text;
    }

    /**
     * Translates some text for the current locale and distinguishes between
     * {@code singularText} and {@code pluralText} depending on {@code n}.
     * <br>
     * For instance, {@code trn("There was an error!", "There were errors!", i)} or
     * <code>trn("Found {0} error in {1}!", "Found {0} errors in {1}!", i, Integer.toString(i), url)</code>.
     *
     * @param singularText the singular text to translate.
     * Must be a string literal. (No constants or local vars.)
     * Can be broken over multiple lines.
     * An apostrophe ' must be quoted by another apostrophe.
     * @param pluralText the plural text to translate.
     * Must be a string literal. (No constants or local vars.)
     * Can be broken over multiple lines.
     * An apostrophe ' must be quoted by another apostrophe.
     * @param n a number to determine whether {@code singularText} or {@code pluralText} is used.
     * @param objects the parameters for the string.
     * Mark occurrences in {@code singularText} and {@code pluralText} with <code>{0}</code>, <code>{1}</code>, ...
     * @return the translated string.
     * @see #tr
     * @see #trc
     * @see #trnc
     */
    public static String trn(String singularText, String pluralText, long n, Object... objects) {
        return format(gettextn(singularText, pluralText, null, n), objects);
    }

    /**
     * Translates some text in a context for the current locale and distinguishes between
     * {@code singularText} and {@code pluralText} depending on {@code n}.
     * There can be different translations for the same text within different contexts.
     *
     * @param context string that helps translators to find an appropriate
     * translation for {@code text}.
     * @param singularText the singular text to translate.
     * Must be a string literal. (No constants or local vars.)
     * Can be broken over multiple lines.
     * An apostrophe ' must be quoted by another apostrophe.
     * @param pluralText the plural text to translate.
     * Must be a string literal. (No constants or local vars.)
     * Can be broken over multiple lines.
     * An apostrophe ' must be quoted by another apostrophe.
     * @param n a number to determine whether {@code singularText} or {@code pluralText} is used.
     * @param objects the parameters for the string.
     * Mark occurrences in {@code singularText} and {@code pluralText} with <code>{0}</code>, <code>{1}</code>, ...
     * @return the translated string.
     * @see #tr
     * @see #trc
     * @see #trn
     */
    public static String trnc(String context, String singularText, String pluralText, long n, Object... objects) {
        return format(gettextn(singularText, pluralText, context, n), objects);
    }

    private static String gettext(String text, String ctx, boolean lazy) {
        int i;
        if (ctx == null && text.startsWith("_:") && (i = text.indexOf('\n')) >= 0) {
            ctx = text.substring(2, i-1);
            text = text.substring(i+1);
        }
        if (strings != null) {
            String trans = strings.get(ctx == null ? text : "_:"+ctx+'\n'+text);
            if (trans != null)
                return trans;
        }
        if (pstrings != null) {
            i = pluralEval(1);
            String[] trans = pstrings.get(ctx == null ? text : "_:"+ctx+'\n'+text);
            if (trans != null && trans.length > i)
                return trans[i];
        }
        return lazy ? gettext(text, null) : text;
    }

    private static String gettext(String text, String ctx) {
        return gettext(text, ctx, false);
    }

    /* try without context, when context try fails */
    private static String gettextLazy(String text, String ctx) {
        return gettext(text, ctx, true);
    }

    private static String gettextn(String text, String plural, String ctx, long num) {
        int i;
        if (ctx == null && text.startsWith("_:") && (i = text.indexOf('\n')) >= 0) {
            ctx = text.substring(2, i-1);
            text = text.substring(i+1);
        }
        if (pstrings != null) {
            i = pluralEval(num);
            String[] trans = pstrings.get(ctx == null ? text : "_:"+ctx+'\n'+text);
            if (trans != null && trans.length > i)
                return trans[i];
        }

        return num == 1 ? text : plural;
    }

    /**
     * Escapes the special i18n characters <code>'{}</code> with quotes.
     * @param msg unescaped string
     * @return escaped string
     * @since 4477
     */
    public static String escape(String msg) {
        if (msg == null) return null;
        return msg.replace("\'", "\'\'").replace("{", "\'{\'").replace("}", "\'}\'");
    }

    private static URL getTranslationFile(String lang) {
        return I18n.class.getResource(CORE_TRANS_DIRECTORY + lang.replace('@', '-') + ".lang");
    }

    /**
     * Get a list of all available JOSM Translations.
     * @return an array of locale objects.
     */
    public static Stream<Locale> getAvailableTranslations() {
        Stream<String> languages = Stream.concat(
                getTranslationFile("en") != null ? I18n.languages.keySet().stream() : Stream.empty(),
                Stream.of("en"));
        return languages.filter(loc -> getTranslationFile(loc) != null).map(LanguageInfo::getLocale);
    }

    /**
     * Determines if a language exists for the given code.
     * @param code The language code
     * @return {@code true} if a language exists, {@code false} otherwise
     */
    public static boolean hasCode(String code) {
        return languages.containsKey(code);
    }

    static String setupJavaLocaleProviders() {
        // Look up SPI providers first (for JosmDecimalFormatSymbolsProvider).
        // Enable CLDR locale provider on Java 8 to get additional languages, such as Khmer.
        // https://docs.oracle.com/javase/8/docs/technotes/guides/intl/enhancements.8.html#cldr
        // FIXME: This must be updated after we switch to Java 9.
        // See https://docs.oracle.com/javase/9/docs/api/java/util/spi/LocaleServiceProvider.html
        try {
            try {
                // First check we're able to open a stream to our own SPI file
                // Java will fail on Windows if the jar file is in a folder with a space character!
                I18n.class.getResourceAsStream("/META-INF/services/java.text.spi.DecimalFormatSymbolsProvider").close();
                // Don't call Utils.updateSystemProperty to avoid spurious log at startup
                return System.setProperty("java.locale.providers", "SPI,JRE,CLDR");
            } catch (RuntimeException | IOException e) {
                // Don't call Logging class, it may not be fully initialized yet
                System.err.println("Unable to set SPI locale provider: " + e.getMessage());
            }
        } catch (SecurityException e) {
            // Don't call Logging class, it may not be fully initialized yet
            System.err.println("Unable to set locale providers: " + e.getMessage());
        }
        return System.setProperty("java.locale.providers", "JRE,CLDR");
    }

    /**
     * I18n initialization.
     */
    public static void init() {
        setupJavaLocaleProviders();

        /* try initial language settings, may be changed later again */
        if (!load(LanguageInfo.getJOSMLocaleCode())) {
            Locale.setDefault(new Locale("en", Locale.getDefault().getCountry()));
        }
    }

    /**
     * I18n initialization for plugins.
     * @param source file path/name of the JAR or Zip file containing translation strings
     * @since 4159
     */
    public static void addTexts(File source) {
        if ("en".equals(loadedCode))
            return;
        final ZipEntry enfile = new ZipEntry(PLUGIN_TRANS_DIRECTORY + "en.lang");
        final ZipEntry langfile = new ZipEntry(PLUGIN_TRANS_DIRECTORY + loadedCode + ".lang");
        try (
            ZipFile zipFile = new ZipFile(source, StandardCharsets.UTF_8);
            InputStream orig = zipFile.getInputStream(enfile);
            InputStream trans = zipFile.getInputStream(langfile)
        ) {
            if (orig != null && trans != null)
                load(orig, trans, true);
        } catch (IOException | InvalidPathException e) {
            Logging.trace(e);
        }
    }

    private static boolean load(String l) {
        if ("en".equals(l) || "en_US".equals(l)) {
            strings = null;
            pstrings = null;
            loadedCode = "en";
            pluralMode = PluralMode.MODE_NOTONE;
            return true;
        }
        URL en = getTranslationFile("en");
        if (en == null)
            return false;
        URL tr = getTranslationFile(l);
        if (tr == null || !languages.containsKey(l)) {
            return false;
        }
        try (
            InputStream enStream = Utils.openStream(en);
            InputStream trStream = Utils.openStream(tr)
        ) {
            if (load(enStream, trStream, false)) {
                pluralMode = languages.get(l);
                loadedCode = l;
                return true;
            }
        } catch (IOException e) {
            // Ignore exception
            Logging.trace(e);
        }
        return false;
    }

    private static boolean load(InputStream en, InputStream tr, boolean add) {
        Map<String, String> s;
        Map<String, String[]> p;
        if (add) {
            s = strings;
            p = pstrings;
        } else {
            s = new HashMap<>();
            p = new HashMap<>();
        }
        /* file format:
           Files are always a group. English file and translated file must provide identical datasets.

           for all single strings:
           {
             unsigned short (2 byte) stringlength
               - length 0 indicates missing translation
               - length 0xFFFE indicates translation equal to original, but otherwise is equal to length 0
             string
           }
           unsigned short (2 byte) 0xFFFF (marks end of single strings)
           for all multi strings:
           {
             unsigned char (1 byte) stringcount
               - count 0 indicates missing translations
               - count 0xFE indicates translations equal to original, but otherwise is equal to length 0
             for stringcount
               unsigned short (2 byte) stringlength
               string
           }
         */
        try {
            InputStream ens = new BufferedInputStream(en);
            InputStream trs = new BufferedInputStream(tr);
            byte[] enlen = new byte[2];
            byte[] trlen = new byte[2];
            boolean multimode = false;
            byte[] str = new byte[4096];
            for (;;) {
                if (multimode) {
                    int ennum = ens.read();
                    int trnum = trs.read();
                    if (trnum == 0xFE) /* marks identical string, handle equally to non-translated */
                        trnum = 0;
                    if ((ennum == -1 && trnum != -1) || (ennum != -1 && trnum == -1)) /* files do not match */
                        return false;
                    if (ennum == -1) {
                        break;
                    }
                    String[] enstrings = new String[ennum];
                    for (int i = 0; i < ennum; ++i) {
                        int val = ens.read(enlen);
                        if (val != 2) /* file corrupt */
                            return false;
                        val = (enlen[0] < 0 ? 256+enlen[0] : enlen[0])*256+(enlen[1] < 0 ? 256+enlen[1] : enlen[1]);
                        if (val > str.length) {
                            str = new byte[val];
                        }
                        int rval = ens.read(str, 0, val);
                        if (rval != val) /* file corrupt */
                            return false;
                        enstrings[i] = new String(str, 0, val, StandardCharsets.UTF_8);
                    }
                    String[] trstrings = new String[trnum];
                    for (int i = 0; i < trnum; ++i) {
                        int val = trs.read(trlen);
                        if (val != 2) /* file corrupt */
                            return false;
                        val = (trlen[0] < 0 ? 256+trlen[0] : trlen[0])*256+(trlen[1] < 0 ? 256+trlen[1] : trlen[1]);
                        if (val > str.length) {
                            str = new byte[val];
                        }
                        int rval = trs.read(str, 0, val);
                        if (rval != val) /* file corrupt */
                            return false;
                        trstrings[i] = new String(str, 0, val, StandardCharsets.UTF_8);
                    }
                    if (trnum > 0 && !p.containsKey(enstrings[0])) {
                        p.put(enstrings[0], trstrings);
                    }
                } else {
                    int enval = ens.read(enlen);
                    int trval = trs.read(trlen);
                    if (enval != trval) /* files do not match */
                        return false;
                    if (enval == -1) {
                        break;
                    }
                    if (enval != 2) /* files corrupt */
                        return false;
                    enval = (enlen[0] < 0 ? 256+enlen[0] : enlen[0])*256+(enlen[1] < 0 ? 256+enlen[1] : enlen[1]);
                    trval = (trlen[0] < 0 ? 256+trlen[0] : trlen[0])*256+(trlen[1] < 0 ? 256+trlen[1] : trlen[1]);
                    if (trval == 0xFFFE) /* marks identical string, handle equally to non-translated */
                        trval = 0;
                    if (enval == 0xFFFF) {
                        multimode = true;
                        if (trval != 0xFFFF) /* files do not match */
                            return false;
                    } else {
                        if (enval > str.length) {
                            str = new byte[enval];
                        }
                        if (trval > str.length) {
                            str = new byte[trval];
                        }
                        int val = ens.read(str, 0, enval);
                        if (val != enval) /* file corrupt */
                            return false;
                        String enstr = new String(str, 0, enval, StandardCharsets.UTF_8);
                        if (trval != 0) {
                            val = trs.read(str, 0, trval);
                            if (val != trval) /* file corrupt */
                                return false;
                            String trstr = new String(str, 0, trval, StandardCharsets.UTF_8);
                            if (!s.containsKey(enstr))
                                s.put(enstr, trstr);
                        }
                    }
                }
            }
        } catch (IOException e) {
            Logging.trace(e);
            return false;
        }
        if (!s.isEmpty()) {
            strings = s;
            pstrings = p;
            return true;
        }
        return false;
    }

    /**
     * Sets the default locale (see {@link Locale#setDefault(Locale)} to the local
     * given by <code>localName</code>.
     *
     * Ignored if localeName is null. If the locale with name <code>localName</code>
     * isn't found the default local is set to <code>en</code> (english).
     *
     * @param localeName the locale name. Ignored if null.
     */
    public static void set(String localeName) {
        if (localeName != null) {
            Locale l = LanguageInfo.getLocale(localeName, true);
            if (load(LanguageInfo.getJOSMLocaleCode(l))) {
                Locale.setDefault(l);
            } else {
                if (!"en".equals(l.getLanguage())) {
                    Logging.info(tr("Unable to find translation for the locale {0}. Reverting to {1}.",
                            LanguageInfo.getDisplayName(l), LanguageInfo.getDisplayName(Locale.getDefault())));
                } else {
                    strings = null;
                    pstrings = null;
                }
            }
        }
    }

    /**
     * Updates the default locale: overrides the numbering system, if defined in internal boundaries.xml for the current language/country.
     * @since 16109
     */
    public static void initializeNumberingFormat() {
        Locale l = Locale.getDefault();
        TagMap tags = Territories.getCustomTags(l.getCountry());
        if (tags != null) {
            String numberingSystem = tags.get("ldml:nu:" + l.getLanguage());
            if (numberingSystem != null && !numberingSystem.equals(l.getExtension(Locale.UNICODE_LOCALE_EXTENSION))) {
                Locale.setDefault(new Locale.Builder()
                        .setLanguage(l.getLanguage())
                        .setRegion(l.getCountry())
                        .setVariant(l.getVariant())
                        .setExtension(Locale.UNICODE_LOCALE_EXTENSION, numberingSystem)
                        .build());
            }
        }
    }

    private static int pluralEval(long n) {
        switch(pluralMode) {
        case MODE_NOTONE: /* bg, da, de, el, en, en_AU, en_CA, en_GB, es, et, eu, fi, gl, is, it, iw_IL, mr, nb, nl, sv */
            return (n != 1) ? 1 : 0;
        case MODE_NONE: /* id, vi, ja, km, tr, zh_CN, zh_TW */
            return 0;
        case MODE_GREATERONE: /* fr, pt_BR */
            return (n > 1) ? 1 : 0;
        case MODE_CS:
            return (n == 1) ? 0 : (((n >= 2) && (n <= 4)) ? 1 : 2);
        case MODE_AR:
            return ((n == 0) ? 0 : ((n == 1) ? 1 : ((n == 2) ? 2 : ((((n % 100) >= 3)
                    && ((n % 100) <= 10)) ? 3 : ((((n % 100) >= 11) && ((n % 100) <= 99)) ? 4 : 5)))));
        case MODE_PL:
            return (n == 1) ? 0 : (((((n % 10) >= 2) && ((n % 10) <= 4))
                    && (((n % 100) < 10) || ((n % 100) >= 20))) ? 1 : 2);
        //case MODE_RO:
        //    return ((n == 1) ? 0 : ((((n % 100) > 19) || (((n % 100) == 0) && (n != 0))) ? 2 : 1));
        case MODE_LT:
            return ((n % 10) == 1) && ((n % 100) != 11) ? 0 : (((n % 10) >= 2)
                    && (((n % 100) < 10) || ((n % 100) >= 20)) ? 1 : 2);
        case MODE_RU:
            return (((n % 10) == 1) && ((n % 100) != 11)) ? 0 : (((((n % 10) >= 2)
                    && ((n % 10) <= 4)) && (((n % 100) < 10) || ((n % 100) >= 20))) ? 1 : 2);
        case MODE_SK:
            return (n == 1) ? 1 : (((n >= 2) && (n <= 4)) ? 2 : 0);
        //case MODE_SL:
        //    return (((n % 100) == 1) ? 1 : (((n % 100) == 2) ? 2 : ((((n % 100) == 3)
        //            || ((n % 100) == 4)) ? 3 : 0)));
        }
        return 0;
    }

    /**
     * Returns the map of singular translations.
     * @return the map of singular translations.
     * @since 13761
     */
    public static Map<String, String> getSingularTranslations() {
        return new HashMap<>(strings);
    }

    /**
     * Returns the map of plural translations.
     * @return the map of plural translations.
     * @since 13761
     */
    public static Map<String, String[]> getPluralTranslations() {
        return new HashMap<>(pstrings);
    }

    /**
     * Returns the original default locale found when the JVM started.
     * Used to guess real language/country of current user disregarding language chosen in JOSM preferences.
     * @return the original default locale found when the JVM started
     * @since 14013
     */
    public static Locale getOriginalLocale() {
        return originalLocale;
    }

    /**
     * Returns the localized name of the given script. Only scripts used in the OSM database are known.
     * @param script Writing system
     * @return the localized name of the given script, or null
     * @since 15501
     */
    public static String getLocalizedScript(String script) {
        if (script != null) {
            switch (script.toLowerCase(Locale.ENGLISH)) {
                case HIRAGANA:
                    return /* I18n: a Japanese syllabary */ tr("Hiragana");
                case KATAKANA:
                    return /* I18n: a Japanese syllabary */ tr("Katakana");
                case LATIN:
                    return /* I18n: usage of latin letters/script for usually non-latin languages */ tr("Latin");
                case PINYIN:
                    return /* I18n: official romanization system for Standard Chinese */ tr("Pinyin");
                case ROMAJI:
                    return /* I18n: a Japanese syllabary (latin script) */  tr("Rōmaji");
                default:
                    Logging.warn("Unsupported script: {0}", script);
            }
        }
        return null;
    }

    /**
     * Returns the localized name of the given language and optional script.
     * @param language Language
     * @return the pair of localized name + known state of the given language, or null
     * @since 15501
     */
    public static Pair<String, Boolean> getLocalizedLanguageName(String language) {
        Matcher m = LANGUAGE_NAMES.matcher(language);
        if (m.matches()) {
            String code = m.group(1);
            String label = new Locale(code).getDisplayLanguage();
            boolean knownNameKey = !code.equals(label);
            String script = getLocalizedScript(m.group(2));
            if (script != null) {
                label += " (" + script + ")";
            }
            return new Pair<>(label, knownNameKey);
        }
        return null;
    }
}
