// File: VertPanel.java
// Classes: VertPanel
// Author: Kedar Patankar

package edu.neu.ccs.demeter.tools.apstudio.graphedit;

import java.awt.Panel;
import java.awt.Cursor;
import java.awt.Container;
import java.awt.BorderLayout;

import javax.swing.event.HyperlinkListener;
import javax.swing.event.HyperlinkEvent;

import javax.swing.JEditorPane;
import javax.swing.SwingUtilities;
import javax.swing.JScrollPane;
import javax.swing.JViewport;

import java.net.URL;
import java.net.MalformedURLException;
import java.io.IOException;

/* Purpose : Display the help in html style */

public class HtmlPanel extends Panel implements HyperlinkListener 
{
	JEditorPane html;

    public HtmlPanel(String basePage) 
	{
		setLayout(new BorderLayout());
		try 
		{
			URL url = new URL(basePage);
			html = new JEditorPane(url);
			html.setEditable(false);
			html.addHyperlinkListener(this);
			JScrollPane scroller = new JScrollPane();
			JViewport vp = scroller.getViewport();
			vp.add(html);
			vp.setScrollMode(JViewport.BLIT_SCROLL_MODE);
			add(scroller, BorderLayout.CENTER);
		} 
		catch (MalformedURLException e) 
		{
			System.out.println("Malformed URL: " + e.getMessage());
		} 
		catch (IOException e) 
		{	
			System.out.println(e.getMessage());
		}
    }

    /**
     * Notification of a change relative to a 
     * hyperlink.
     */
    public void hyperlinkUpdate(HyperlinkEvent e) 
	{
		if (e.getEventType() == HyperlinkEvent.EventType.ACTIVATED) 
		{
			linkActivated(e.getURL());
		}
    }

    /**
     * Follows the reference in an
     * link.  The given url is the requested reference.
     * By default this calls <a href="#setPage">setPage</a>,
     * and if an exception is thrown the original previous
     * document is restored and a beep sounded.  If an 
     * attempt was made to follow a link, but it represented
     * a malformed url, this method will be called with a
     * null argument.
     *
     * @param u the URL to follow
     */
    protected void linkActivated(URL u) 
	{
		Cursor c = html.getCursor();
		Cursor waitCursor = Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR);
		html.setCursor(waitCursor);
		SwingUtilities.invokeLater(new PageLoader(u, c));
    }

    /**
     * temporary class that loads synchronously (although
     * later than the request so that a cursor change
     * can be done).
     */
    class PageLoader implements Runnable 
	{
		PageLoader(URL u, Cursor c) 
		{
			url = u;
			cursor = c;
		}

        public void run() 
		{
			if (url == null) 
			{
				// restore the original cursor
				html.setCursor(cursor);
				// PENDING(prinz) remove this hack when 
				// automatic validation is activated.
				Container parent = html.getParent();
				parent.repaint();
			} 
			else 
			{
				javax.swing.text.Document doc = html.getDocument();
				try 
				{
					html.setPage(url);
				} 
				catch (IOException ioe) 
				{
					html.setDocument(doc);
					getToolkit().beep();
					System.err.println(ioe);
				} 
				finally 
				{
					// schedule the cursor to revert after
					// the paint has happended.
					url = null;
					SwingUtilities.invokeLater(this);
				}
			}
		}
		URL url;
		Cursor cursor;
    }
} /* end class HtmlPanel */