package com.melloware.jukes.gui.tool;
   
   import java.net.URL;
   import java.util.HashMap;
   import java.util.Map;
   
   import javax.swing.event.TreeSelectionEvent;
   import javax.swing.event.TreeSelectionListener;
   import javax.swing.tree.DefaultMutableTreeNode;
  import javax.swing.tree.DefaultTreeModel;
  import javax.swing.tree.DefaultTreeSelectionModel;
  import javax.swing.tree.TreeModel;
  import javax.swing.tree.TreeNode;
  import javax.swing.tree.TreePath;
  import javax.swing.tree.TreeSelectionModel;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  import com.melloware.jukes.gui.tool.help.HelpNode;
  import com.melloware.jukes.gui.tool.help.HelpSets;
  
  /**
   * Provides bound bean properties for the help tree model,
   * the help page and the help visibility.
   * <p>
   * Copyright (c) 1999-2007 Melloware, Inc. <http://www.melloware.com>
   * @author Emil A. Lefkof III <info@melloware.com>
   * @version 4.0
   */
  public final class DynamicHelpModule
      extends com.jgoodies.binding.beans.Model {
  
      private static final Log LOG = LogFactory.getLog(DynamicHelpModule.class);
  
      public static final String PROPERTYNAME_HELP_TREE_MODEL = "helpTreeModel";
      public static final String PROPERTYNAME_HELP_PAGE = "helpPage";
      public static final String PROPERTYNAME_HELP_VISIBLE = "helpVisible";
  
      /**
       * Determines whether the dynamic help shall be displayed or hidden.
       *
       * @see #isHelpVisible()
       * @see #setHelpVisible(boolean)
       */
      private boolean helpVisible;
  
      /**
       * Maps domain classes to help roots.
       */
      private final Map helpRegistry;
  
      /**
       * Holds the model for the help tree.
       * It changes everytime the selection changes.
       *
       * @see #getHelpTreeModel()
       * @see #getHelpTreeSelectionModel()
       */
      private TreeModel helpTreeModel;
  
      /**
       * Refers to the single selection model for the help tree.
       * The selection is reset if the help tree model changes.
       *
       * @see #getHelpTreeSelectionModel()
       * @see #getHelpTreeModel()
       */
      private final TreeSelectionModel helpTreeSelectionModel;
  
      /**
       * Holds the URL for the currently selected help page.
       *
       * @see #getHelpPage()
       */
      private URL helpPage;
  
      /**
       * Constructs a <code>DynamicHelpModule</code>
       * with the welcome help set preselected.
       */
      DynamicHelpModule() {
          helpRegistry = new HashMap();
  
          setHelpSet(HelpSets.WELCOME_HELP_SET);
          helpTreeSelectionModel = new DefaultTreeSelectionModel();
          helpTreeSelectionModel.setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION);
          helpTreeSelectionModel.addTreeSelectionListener(new HelpTreeSelectionChangeHandler());
      }
  
      /**
       * Returns the current help page, a URL. This page
       * will be updated if the selection in the help tree changes.
       *
       * @return the URL for the currently selected help page.
       */
      public URL getHelpPage() {
          return helpPage;
      }
 
     /**
      * Returns the tree model for the help tree.
      *
      * @return the tree model for the help tree.
      */
     public TreeModel getHelpTreeModel() {
         return helpTreeModel;
     }
 
     /**
      * Returns the fixed selection model for the navigation tree.
      *
      * @return the fixed selection model for the navigation tree.
      */
     public TreeSelectionModel getHelpTreeSelectionModel() {
         return helpTreeSelectionModel;
     }
 
     /**
      * Sets a new visibility for the help viewer.
      *
      * @param newVisibility   the help page to set
      *
      * @see #isHelpVisible()
      */
     public void setHelpVisible(boolean newVisibility) {
         boolean oldVisibility = isHelpVisible();
         helpVisible = newVisibility;
         firePropertyChange(PROPERTYNAME_HELP_VISIBLE, oldVisibility, newVisibility);
     }
 
     /**
      * Answers whether the dynamic help is visible or not.
      *
      * @return true if the help viewer is visible, false if hidden.
      */
     public boolean isHelpVisible() {
         return helpVisible;
     }
 
     /**
      * Registers a help tree for a domain class.
      */
     @SuppressWarnings("unchecked")
     public void registerHelp(Class domainClass, TreeNode node) {
         Object oldValue = helpRegistry.put(domainClass, node);
         if (oldValue != null) {
             LOG.warn("Duplicate help registered for class " + domainClass);
         }
     }
 
     void updateHelpSet(Object selection) {
         TreeNode helpSet = lookupHelpSet(selection.getClass());
         if (helpSet != null) {
             setHelpSet(helpSet);
         }
     }
 
     /**
      * Sets a URL as new help page. This method is invoked
      * by the HelpTreeSelectionChangeHandler that observes changes in
      * the selection of the help tree.<p>
      *
      * Sets the help to visible.
      *
      * @param newHelpPage   the help page to set
      *
      * @see #getHelpPage()
      */
     private void setHelpPage(URL newHelpPage) {
         URL oldHelpPage = getHelpPage();
         helpPage = newHelpPage;
         if (equals(oldHelpPage, newHelpPage)) {
             return;
         }
 
         firePropertyChange(PROPERTYNAME_HELP_PAGE, oldHelpPage, newHelpPage);
         setHelpVisible(true);
     }
 
     private void setHelpSet(TreeNode helpSet) {
         setHelpTreeModel(new DefaultTreeModel(helpSet));
     }
 
     /**
      * Sets a new tree model for the help tree.
      *
      * @param newModel  the new tree model to set
      */
     private void setHelpTreeModel(TreeModel newModel) {
         TreeModel oldModel = getHelpTreeModel();
         helpTreeModel = newModel;
         firePropertyChange(PROPERTYNAME_HELP_TREE_MODEL, oldModel, newModel);
     }
 
     /**
      * Returns the <code>HelpNode</code> that has been registered
      * for the given domain object class, <code>null</code> if none.
      *
      * @param domainClass   the class associated with the editor to lookup
      * @return the editor associated with the given domain class
      */
     private TreeNode lookupHelpSet(Class domainClass) {
         return (TreeNode)helpRegistry.get(domainClass);
     }
 
     // Listens to changes in the help tree node selection
     // and updates the selection.
     private class HelpTreeSelectionChangeHandler
         implements TreeSelectionListener {
 
         /**
          * The selected node in the help tree has changed.
          * Updates this module's help page.<p>
          *
          * Does nothing if the new tree selection is <code>null</code>.
          *
          * @param evt    the event that describes the change
          */
         public void valueChanged(TreeSelectionEvent evt) {
             TreePath path = evt.getPath();
             DefaultMutableTreeNode selectedNode = (DefaultMutableTreeNode)path.getLastPathComponent();
             HelpNode helpNode = (HelpNode)selectedNode.getUserObject();
             if ((null == helpNode) || helpNode.isChapter()) {
                 return;
             }
 
             setHelpPage(helpNode.getURL());
         }
 
     }
 
 }