/*
    * Copyright 2006-2012 smartics, Kronseder & Reiner GmbH
    *
    * Licensed under the Apache License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    *     http://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package de.smartics.maven.util.report;
  
  import java.util.Locale;
  import java.util.MissingResourceException;
  import java.util.ResourceBundle;
  
  /**
   * Helps to fetch labels to render reports. Labels are taken from two resource
   * bundles: a standard and a default one. If a key is not found in the standard
   * bundle, it is fetched from the default bundle. If it is not found there
   * either the key is returned verbatim.
   *
   * @author <a href="mailto:robert.reiner@smartics.de">Robert Reiner</a>
   * @version $Revision:591 $
   */
  public class MessageHelper
  {
    // ********************************* Fields *********************************
  
    // --- constants ------------------------------------------------------------
  
    // --- members --------------------------------------------------------------
  
    /**
     * The report title ID.
     */
    private final String reportTitleId;
  
    /**
     * The report description ID.
     */
    private final String reportDescriptionId;
  
    /**
     * The primary message bundle to use. May be <code>null</code> so that all
     * labels are provided by the {@link #defaultMessages}.
     */
    private final ResourceBundle messages;
  
    /**
     * The default messages that are used if the {@link #messages} contain no
     * value for a given key.
     */
    private final ResourceBundle defaultMessages;
  
    // ****************************** Initializer *******************************
  
    // ****************************** Constructors ******************************
  
    /**
     * Default constructor.
     *
     * @param reportTitleId the localized report title.
     * @param reportDescriptionId the localized report description.
     * @param messages the primary message bundle to use.
     * @param defaultMessages the default messages that are used if the
     *          {@link #messages} contain no value for a given key.
     * @throws NullPointerException if <code>defaultMessages</code> is
     *           <code>null</code>.
     */
    public MessageHelper(final String reportTitleId,
        final String reportDescriptionId, final ResourceBundle messages,
        final ResourceBundle defaultMessages) throws NullPointerException
    {
      checkArguments(defaultMessages);
      this.reportTitleId = reportTitleId;
      this.reportDescriptionId = reportDescriptionId;
      this.messages = messages;
      this.defaultMessages = defaultMessages;
    }
  
    // ****************************** Inner Classes *****************************
  
    // ********************************* Methods ********************************
  
    // --- init -----------------------------------------------------------------
  
    private static void checkArguments(final ResourceBundle defaultMessages)
      throws NullPointerException
    {
      if (defaultMessages == null)
      {
        throw new NullPointerException(
            "The default resource bundle must not be 'null'.");
     }
   }
 
   // --- get&set --------------------------------------------------------------
 
   /**
    * Returns the localized report title.
    *
    * @return the localized report title.
    */
   public String getReportTitleId()
   {
     return reportTitleId;
   }
 
   /**
    * Returns the localized report description.
    *
    * @return the localized report description.
    */
   public String getReportDescriptionId()
   {
     return reportDescriptionId;
   }
 
   /**
    * Returns the locale the message helper provides messages for.
    *
    * @return the locale of the resource bundles.
    */
   public Locale getLocale()
   {
     return defaultMessages.getLocale();
   }
 
   // --- business -------------------------------------------------------------
 
   /**
    * Returns the label for the given <code>key</code>.
    *
    * @param key the key to the requested label.
    * @return the label to the <code>key</code> or the <code>key</code>, if no
    *         label is found for that <code>key</code>.
    */
   public String getLabel(final String key)
   {
     return getLabel(key, key);
   }
 
   /**
    * Returns the label for the given <code>key</code>.
    *
    * @param key the key to the requested label.
    * @param defaultLabel the label to return if no label is found by the
    *          <code>key</code>.
    * @return the label to the <code>key</code> or the <code>defaultLabel</code>,
    *         if no label is found for that <code>key</code>.
    */
   public String getLabel(final String key, final String defaultLabel)
   {
     String label = getStringFromMessages(key);
     if (label == null)
     {
       label = getStringFromDefaultMessages(key, defaultLabel);
     }
     return label;
   }
 
   private String getStringFromDefaultMessages(final String key,
       final String defaultLabel)
   {
     try
     {
       return defaultMessages.getString(key);
     }
     catch (final MissingResourceException e)
     {
       return defaultLabel;
     }
   }
 
   private String getStringFromMessages(final String key)
   {
     if (messages != null)
     {
       try
       {
         return messages.getString(key);
       }
       catch (final MissingResourceException e)
       {
         // Return null at the end
       }
     }
     return null;
   }
 
   // --- object basics --------------------------------------------------------
 
 }