I18N.java

/*
 * This file is part of the OSMembrane project.
 * More informations under www.osmembrane.de
 * 
 * The project is licensed under the GNU GENERAL PUBLIC LICENSE 3.0.
 * for more details about the license see http://www.osmembrane.de/license/
 * 
 * Source: $HeadURL$ ($Revision$)
 * Last changed: $Date$
 */

package de.osmembrane.tools;

import java.text.MessageFormat;
import java.util.Locale;
import java.util.MissingResourceException;
import java.util.Observable;
import java.util.ResourceBundle;

import javax.swing.JComponent;

import de.osmembrane.model.xml.XMLHasDescription;
import de.osmembrane.model.xml.XMLHasDescription.Description;
import de.osmembrane.resources.Constants;

/**
 * Internationalization for OSMembrane.
 * 
 * @author jakob_jarosch
 */
public class I18N extends Observable {

    /**
     * Locale for the current instance.
     */
    private Locale activeLocale;

    /**
     * ResourceBundle where localized Strings are saved.
     */
    private ResourceBundle resourceBundle;

    /**
     * Default-Locale for {@link XMLHasDescription}.
     */
    private Locale defaultLocale;

    /**
     * Implements the Singleton pattern.
     */
    private static I18N instance = new I18N();

    /**
     * Creates a new ResourceBundle with the default locale of the system.
     */
    private I18N() {
        /* use the system default locale */
        setLocale(Locale.getDefault());

        /*
         * use a program default locale 'cause system default may not be
         * translated
         */
        setDefaultLocale(Constants.DEFAULT_LOCALE);
    }

    /**
     * Getter for the Singleton pattern.
     * 
     * @return the one and only instance of I18N
     */
    public static I18N getInstance() {
        return instance;
    }

    /**
     * Updates the locale for the current instance.
     * 
     * @param locale
     *            new locale for ResourceBundle.
     */
    public void setLocale(Locale locale) {
        this.activeLocale = locale;
        Locale.setDefault(locale);
        this.resourceBundle = ResourceBundle.getBundle(
                Constants.RESOURCE_BUNDLE_PATH, this.activeLocale);

        setSwingLocale(locale);

        /* notify the observers that possibly the language has been changed */
        setChanged();
        notifyObservers();
    }

    /**
     * Updates the default locale for the current instance.
     * 
     * @param locale
     *            new defaultLocale for {@link XMLHasDescription}
     */
    protected void setDefaultLocale(Locale locale) {
        this.defaultLocale = locale;

        /* notify the observers that possibly the language has been changed */
        setChanged();
        notifyObservers();
    }

    /**
     * Gives a localized and formatted String for a given key back.
     * 
     * @param key
     *            Key which needs a localized String
     * @param values
     *            Values that should be inserted into the String
     * @return a localized and formatted String
     */
    public String getString(String key, Object... values) {
        String msg;
        try {
            msg = resourceBundle.getString(key);
        } catch (MissingResourceException e) {
            msg = "!" + key + "!";
        }

        if (values.length > 0) {
            return MessageFormat.format(msg, values);
        }

        return msg;
    }

    /**
     * Gives a localized String for a given {@link XMLHasDescription} object
     * back.
     * 
     * @param description
     *            which should be localized
     * @return String for the localized description or null if no localization
     *         was found.
     */
    public String getDescription(XMLHasDescription description) {

        if (description.getDescription() == null) {
            return null;
        }

        /* First try to find activeLocale. */
        for (Description descriptionString : description.getDescription()) {
            if (descriptionString.getLang() != null
                    && descriptionString.getLang().equals(
                            activeLocale.getLanguage())) {
                return descriptionString.getValue().trim();
            }
        }

        /*
         * No translation for the active locale has been found, so try to use
         * the defaultLocale.
         */
        for (Description descriptionString : description.getDescription()) {
            if (descriptionString.getLang().equals(defaultLocale.getLanguage())) {
                return descriptionString.getValue().trim();
            }
        }

        /* No translation found, return null */
        return null;
    }

    /**
     * Sets the language to all swing components.
     * 
     * @param locale
     *            language to be set
     */
    private void setSwingLocale(Locale locale) {
        JComponent.setDefaultLocale(locale);

    }
}