/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You 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 org.apache.log4j.chainsaw.help;
  
  import org.apache.log4j.LogManager;
  import org.apache.log4j.Logger;
  import org.apache.log4j.chainsaw.ChainsawConstants;
  
  import java.beans.PropertyChangeEvent;
  import java.beans.PropertyChangeListener;
  import java.beans.PropertyChangeSupport;
  import java.io.File;
  import java.net.URL;
  
  
  /**
   * Singleton help manager where objects can register to display
   * Help for something, an independant viewer can register to
   * be notified when the requested Help URL changes and can display
   * it appropriately. This class effectively decouples the help requester
   * from the help implementation (if any!)
   *
   * @author Paul Smith <psmith@apache.org>
   */
  public final class HelpManager {
  
      private static final HelpManager instance = new HelpManager();
      private HelpLocator helpLocator = new HelpLocator();
      private URL helpURL;
      private final PropertyChangeSupport propertySupport =
          new PropertyChangeSupport(this);
      private final Logger logger = LogManager.getLogger(HelpManager.class);
  
      private HelpManager() {
  
  //    TODO setup all the base URLs in the default.properties and configure in ApplicationPreferenceModel
  
          try {
  
              if (System.getProperty("log4j.chainsaw.localDocs") != null) {
                  logger.info("Adding HelpLocator for localDocs property=" +
                      System.getProperty("log4j.chainsaw.localDocs"));
                  helpLocator.installLocator(new URL(
                      System.getProperty("log4j.chainsaw.localDocs")));
              } else if (new File("docs/api").exists()) {
                  File dir = new File("docs/api");
                  logger.info("Detected Local JavaDocs at " + dir.toString());
                  helpLocator.installLocator(dir.toURI().toURL());
              } else {
                  logger.warn("Could not find any local JavaDocs, you might want to consider running 'ant javadoc'. The release version will be able to access Javadocs from the Apache website.");
              }
          } catch (Exception e) {
              // TODO: handle exception
          }
  
          helpLocator.installClassloaderLocator(this.getClass().getClassLoader());
  //      helpLocator.installLocator(new URL());
      }
  
      /**
       * The current Help URL that should be displayed, and is
       * a PropertyChangeListener supported property.
       * <p>
       * This method ALWAYS fires property change events
       * even if the value is the same (the oldvalue
       * of the event will be null)
       *
       * @param helpURL
       */
      public void setHelpURL(URL helpURL) {
          this.helpURL = helpURL;
          firePropertyChange("helpURL", null, this.helpURL);
      }
  
      /**
       * @param listener
       */
      public void addPropertyChangeListener(PropertyChangeListener listener) {
          propertySupport.addPropertyChangeListener(listener);
      }
  
      /**
       * @param propertyName
       * @param listener
      */
     public synchronized void addPropertyChangeListener(String propertyName,
                                                        PropertyChangeListener listener) {
         propertySupport.addPropertyChangeListener(propertyName, listener);
     }
 
     /**
      * @param evt
      */
     public void firePropertyChange(PropertyChangeEvent evt) {
         propertySupport.firePropertyChange(evt);
     }
 
     /**
      * @param propertyName
      * @param oldValue
      * @param newValue
      */
     public void firePropertyChange(String propertyName, boolean oldValue,
                                    boolean newValue) {
         propertySupport.firePropertyChange(propertyName, oldValue, newValue);
     }
 
     /**
      * @param propertyName
      * @param oldValue
      * @param newValue
      */
     public void firePropertyChange(String propertyName, int oldValue,
                                    int newValue) {
         propertySupport.firePropertyChange(propertyName, oldValue, newValue);
     }
 
     /**
      * @param propertyName
      * @param oldValue
      * @param newValue
      */
     public void firePropertyChange(String propertyName, Object oldValue,
                                    Object newValue) {
         propertySupport.firePropertyChange(propertyName, oldValue, newValue);
     }
 
     /**
      * @param listener
      */
     public synchronized void removePropertyChangeListener(
         PropertyChangeListener listener) {
         propertySupport.removePropertyChangeListener(listener);
     }
 
     /**
      * @param propertyName
      * @param listener
      */
     public synchronized void removePropertyChangeListener(String propertyName,
                                                           PropertyChangeListener listener) {
         propertySupport.removePropertyChangeListener(propertyName, listener);
     }
 
     /**
      *
      */
     public static HelpManager getInstance() {
 
         return instance;
     }
 
     /**
      * Given a class, and that it belongs within the org.apache.log4j project,
      * sets the URL to the JavaDoc for that class.
      *
      * @param c
      */
     public void showHelpForClass(Class c) {
 
         URL url = getHelpForClass(c);
         setHelpURL(url);
     }
 
     /**
      * Determines the most appropriate Help resource for a particular class
      * or returns ChainsawConstants.URL_PAGE_NOT_FOUND if there is no resource located.
      *
      * @return URL
      */
     public URL getHelpForClass(Class c) {
 
         String name = c.getName();
         name = name.replace('.', '/') + ".html";
 
         URL url = helpLocator.findResource(name);
         logger.debug("located help resource for '" + name + "' at " +
             ((url == null) ? "" : url.toExternalForm()));
 
         return (url != null) ? url : ChainsawConstants.URL_PAGE_NOT_FOUND;
 
     }
 }