/*
    *  Gettext Commons
    *
    *  Copyright (C) 2005  Felix Berger
    *  Copyright (C) 2005  Steffen Pingel
    *
    *  This library is free software; you can redistribute it and/or
    *  modify it under the terms of the GNU Lesser General Public
    *  License as published by the Free Software Foundation; either
   *  version 2.1 of the License, or (at your option) any later version.
   *
   *  This library is distributed in the hope that it will be useful,
   *  but WITHOUT ANY WARRANTY; without even the implied warranty of
   *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   *  Lesser General Public License for more details.
   *
   *  You should have received a copy of the GNU Lesser General Public
   *  License along with this library; if not, write to the Free Software
   *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  package org.xnap.commons.i18n;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.util.Locale;
  import java.util.MissingResourceException;
  import java.util.Properties;
  
  /**
   * Factory class that creates and caches I18n instances.
   * <p>
   * Given a {@link Class} object the factory looks up the resource bundle
   * responsible for handling message translations. The bundle is returned with an
   * {@link I18n} object wrapped around it, which provides the translation
   * methods. The lookup is described at {@link #getI18n(Class,String)}.
   * <p>
   * Use the factory for creating <code>I18n</code> objects to make sure no
   * extraneous objects are created.
   * 
   * @author Felix Berger
   * @author Tammo van Lessen
   * @author Steffen Pingel
   * @since 0.9
   */
  public class I18nFactory {
  
  	private static final String BASENAME_KEY = "basename";
  	
  	/**
  	 * Use the default configuration.
  	 * 
  	 * @since 0.9.1
  	 */
  	public static final int DEFAULT = 0;
  	/**
  	 * Fall back to a default resource bundle that returns the passed text if no
  	 * resource bundle can be located.
  	 * 
  	 * @since 0.9.1
  	 */
  	public static final int FALLBACK = 1 << 0;
  	/**
  	 * Look for files named {@link #PROPS_FILENAME} to determine the basename.
  	 * 
  	 * @since 0.9.1
  	 */
  	public static final int READ_PROPERTIES = 2 << 0;
  	/**
  	 * Do not cache {@link I18n} instance.
  	 * 
  	 * @since 0.9.1
  	 */
  	public static final int NO_CACHE = 4 << 0;
  	
  	/**
  	 * Default name for Message bundles, is "i18n.Messages".
  	 * 
  	 * @since 0.9.1
  	 */
  	public static final String DEFAULT_BASE_NAME = "i18n.Messages";
  	
  	/**
  	 * Filename of the properties file that contains the i18n properties, is
  	 * "i18n.properties".
  	 * 
  	 * @since 0.9
  	 */
  	public static final String PROPS_FILENAME = "i18n.properties";
  	
  	private static final I18nCache i18nCache = new I18nCache();
  
  	private I18nFactory()
  	{
  	}
  
  	/**
  	 * Clears the cache of i18n objects. Used by the test classes.
  	 */
  	static void clearCache()
 	{
 		i18nCache.visit(new I18nCache.Visitor() {
 
 			public void visit(I18n i18n)
 			{
 				I18nManager.getInstance().remove(i18n);
 			}
 		});
 		i18nCache.clear();
 	}
 
 	/**
 	 * Calls {@link #getI18n(Class, Locale) getI18n(clazz, Locale.getDefault())}.
 	 */
 	public static I18n getI18n(final Class clazz)
 	{
 		return getI18n(clazz, Locale.getDefault());
 	}
 
 	/**
 	 * Calls {@link #getI18n(Class, Locale, int) getI18n(clazz, locale,
 	 * READ_PROPERTIES)}.
 	 * 
 	 * @since 0.9.1
 	 */
 	public static I18n getI18n(final Class clazz, final Locale locale)
 	{
 		return getI18n(clazz, locale, READ_PROPERTIES);
 	}
 
 	/**
 	 * Returns the I18n instance responsible for translating messages in the
 	 * package specified by <code>clazz</code>.
 	 * <p>
 	 * Lookup works by iterating upwards in the package hierarchy: First the
 	 * internal cache is asked for an I18n object for a package, otherwise the
 	 * algorithm looks for an <code>i18n.properties</code> file in the
 	 * package. The properties file is queried for a key named
 	 * <code>basename</code> whose value should be the fully qualified
 	 * resource/class name of the resource bundle, e.g
 	 * <code>org.xnap.commons.i18n.Messages</code>.
 	 * <p>
 	 * If after the first iteration no I18n instance has been found, a second
 	 * search begins by looking for resource bundles having the name
 	 * <code>baseName</code>.
 	 * 
 	 * @param clazz
 	 *            the package hierarchy of the clazz and its class loader are
 	 *            used for resolving and loading the resource bundle
 	 * @param baseName
 	 *            the name of the underlying resource bundle
 	 * @param locale
 	 *            the locale of the underlying resource bundle
 	 * @param flags
 	 *            a combination of these configuration flags: {@link #FALLBACK}
 	 * @return created or cached <code>I18n</code> instance
 	 * @throws MissingResourceException
 	 *             if no resource bundle was found
 	 * @since 0.9.1
 	 */
 	public static I18n getI18n(final Class clazz, final Locale locale, final int flags)
 	{
 		ClassLoader classLoader = getClassLoader(clazz.getClassLoader());
 		
 		String bundleName = null;
 		if (isReadPropertiesSet(flags)) {
 			String path = clazz.getName();
 			int index;
 			do {
 				index = path.lastIndexOf('.');
 				path = (index != -1) ? path.substring(0, index) : "";
 				bundleName = readFromPropertiesFile(path, locale, classLoader);
 			}
 			while (bundleName == null && index != -1);
 		}
 		
 		if (bundleName == null) {
 			bundleName = DEFAULT_BASE_NAME;
 		}
 		
 		return getI18n("", bundleName, classLoader, locale, flags);
 	}
 
 	/**
 	 * Calls
 	 * {@link #getI18n(Class, String, Locale) getI18n(clazz, bundleName, Locale.getDefault())}.
 	 * 
 	 * @since 0.9
 	 */
 	public static I18n getI18n(final Class clazz, final String bundleName)
 	{
 		return getI18n(clazz, bundleName, Locale.getDefault());
 	}
 
 	/**
 	 * Calls
 	 * {@link #getI18n(Class, String, Locale, int) getI18n(clazz, bundleName, locale, DEFAULT)}.
 	 * 
 	 * @since 0.9.1
 	 */
 	public static I18n getI18n(final Class clazz, final String bundleName, final Locale locale)
 	{
 		return getI18n(clazz, bundleName, locale, DEFAULT);
 	}
 
 	/**
 	 * Calls
 	 * {@link #getI18n(Class, String, Locale) getI18n(getPackageName(clazz), bundleName, clazz.getClassLoader(), locale, DEFAULT)}.
 	 * 
 	 * @since 0.9.1
 	 */
 	public static I18n getI18n(final Class clazz, final String bundleName, final Locale locale, int flags)
 	{
 		return getI18n(clazz.getName(), bundleName, clazz.getClassLoader(), locale, flags);
 	}
 
 	/**
 	 * @since 0.9.1
 	 */
 	public static I18n getI18n(final String path, final String bundleName, final ClassLoader classLoader, final Locale locale,
 			final int flags)
 	{
 		int index;
 		String prefix = path;
 		do {
 			// chop of last segment of path
 			index = prefix.lastIndexOf('.');
 			prefix = (index != -1) ? prefix.substring(0, index) : "";
 			String name = prefix.length() == 0 ? bundleName : prefix + "." + bundleName;
 			
 			// check cache
 			I18n i18n = i18nCache.get(name, locale);
 			if (i18n != null) {
 				return i18n;
 			}
 			
 			// look for resource bundle in class path
 			i18n = findByBaseName(name, locale, getClassLoader(classLoader), flags);
 			if (i18n != null) {
 				if ((flags & NO_CACHE) == 0) {
 					i18nCache.put(name, i18n);
 				}
 				return i18n;
 			}
 		}
 		while (index != -1);
 		
 		// fallback to default bundle
 		if (isFallbackSet(flags)) {
 			I18n i18n = i18nCache.get("", locale);
 			if (i18n == null) {
 				i18n = new I18n(new EmptyResourceBundle(locale));
 				i18nCache.put("", i18n);
 			}
 			return i18n;
 		}
 		
 		throw new MissingResourceException("Resource bundle not found", path, bundleName);
 	}
 
 	static ClassLoader getClassLoader(ClassLoader classLoader) {
 		return (classLoader != null) ? classLoader : ClassLoader.getSystemClassLoader();
 	}
 	
 	/**
 	 * Tries to create an I18n instance from a properties file.
 	 * 
 	 * @param path
 	 * @param loader
 	 * @return null if no properties file was found
 	 * @throws MissingResourceException
 	 *             if properties file was found but specified resource not
 	 */
 	static String readFromPropertiesFile(final String path, final Locale locale, final ClassLoader loader)
 	{
 		Properties props = new Properties();
 		String filename = path.length() == 0 ? PROPS_FILENAME : path.replace('.', '/') + "/" + PROPS_FILENAME;
 		InputStream in = loader.getResourceAsStream(filename);
 		if (in != null) {
 			try {
 				props.load(in);
 			}
 			catch (IOException e) {
 				// XXX now what?
 			}
 			finally {
 				try {
 					in.close();
 				}
 				catch (IOException e) {
 					// this exception is lost
 				}
 			}
 			return props.getProperty(BASENAME_KEY);
 		}
 		return null;
 	}
 
 	/**
 	 * Uses the class loader to look for a messages properties file.
 	 * 
 	 * @param baseName
 	 *            the base name of the resource bundle
 	 * @param path
 	 *            the path that prefixes baseName
 	 * @param loader
 	 *            the class loader used to look up the bundle
 	 * @param flags
 	 * @return the created instance
 	 */
 	static I18n findByBaseName(final String baseName, final Locale locale, final ClassLoader loader, int flags)
 	{
 		try {
 			return createI18n(baseName, locale, loader, flags);
 		}
 		catch (MissingResourceException e) {
 			return null;
 		}
 	}
 
 	/**
 	 * Creates a new i18n instance and registers it with {@link I18nManager}.
 	 * 
 	 * @param baseName
 	 *            the base name of the resource bundle
 	 * @param locale
 	 *            the locale
 	 * @param loader
 	 *            the class loader used to look up the bundle
 	 * @return the created instance
 	 */
 	private static I18n createI18n(final String baseName, final Locale locale, final ClassLoader loader, final int flags)
 	{
 		I18n i18n = new I18n(baseName, locale, loader);
 		if (!isNoCacheSet(flags)) {
 			I18nManager.getInstance().add(i18n);
 		}
 		return i18n;
 	}
 	
 	private static boolean isFallbackSet(final int flags)
 	{
 		return (flags & FALLBACK) != 0;
 	}
 
 	private static boolean isReadPropertiesSet(final int flags)
 	{
 		return (flags & READ_PROPERTIES) != 0;
 	}
 
 	private static boolean isNoCacheSet(final int flags)
 	{
 		return (flags & NO_CACHE) != 0;
 	}
 
 }