/*
 * GraphSearchApp.java
 *
 *     An applet to display a graph search algorithm.
 *
 * Copyright (c) Renaud Waldura, Thu Jun 15 03:48:14 1995
 */


import awt.Graphics;
import awt.Color;

import graph.*;
import geometry.Rect;



/**
 * An applet to display a graph search algorithm
 */

class GraphSearchApp
    extends browser.Applet
    implements Runnable, GraphSearchDisplay
{

    private
    Graph g;			// the graph

    private 
    Thread search;		// the search thread

    private
    boolean suspended = false;  // the search thread is suspended

    private
    String alg_name;            // the search algorithm name
    
    private
    int sleep_time;		// search speed

    private
    String error_message;       // an error message used when initializing failed

    private
    Rect clip;			// the painting "clipping region"


    /**
     * initialize the applet
     */
    public 
    void init ()	
    {
        java.io.InputStream is = null;
        
        try
        {            
            String s = getAttribute("VERTICES");
            if (s == null) throw new Exception("Applet attribute is mandatory: VERTICES");
            
            int vertices = Integer.valueOf(s).intValue();

            s = getAttribute("DIRECTED");
            if (s == null) throw new Exception("Applet attribute is mandatory: DIRECTED");
            
            boolean directed = s.equalsIgnoreCase("TRUE");

            s = getAttribute("GRAPH");
            if (s == null) throw new Exception("Applet attribute is mandatory: GRAPH");

            is = new net.www.html.URL(documentURL, s).openStream();            
            g = new Graph(vertices, directed, is);

            s = getAttribute("ALGORITHM");
            
            alg_name = "graph." + ((s == null) ? "DFS" : s.toUpperCase()) + "earch";
	
            s = getAttribute("SPEED");
            sleep_time = (s == null) ? 1000 : 5000 / Integer.valueOf(s).intValue();

            error_message = null;            
        }
        catch (Exception e)
        {
            g = null;
            alg_name = null;
            error_message = e.toString();

            if (is != null) is.close();            
        }        
    }


    /**
     * User clicked the applet: start/stop the search
     */
    public synchronized
    void mouseUp (int x, int y)
    {
	if (search == null)
	{
	    search = new Thread(this);
	    search.start();
	}
	else if (!suspended && search.isAlive())
	{
	    search.suspend();
	    suspended = true;   // after suspend(), isAlive() returns true !!
	}
	else
	{
	    search.resume();
	    suspended = false;
	}

	refresh(null);
    }

    /**
     * The run() method is executed by the ``search'' thread
     */
    public
    void run ()
    {
        if (g == null || alg_name == null) return;        
        
        GraphSearch algorithm = (GraphSearch) new(alg_name);
        
	algorithm.init(this);

	algorithm.search(g);	// here is the meat

	refresh(null);        
    }

    /**
     * Stops the search by stopping the thread.
     */
    public synchronized
    void stop ()
    {
	if (search != null)
	{
	    if (search.isAlive()) search.stop(); 
	    search = null;
	}
    }
    

    /**
     * This method is called to refresh the graph.
     */
    public synchronized
    void refresh (Rect r)
    {
	clip = r;	
	repaint();

	if (!suspended && search.isAlive()) Thread.sleep(sleep_time);
    }
    
    /**
     * Clip the drawing region to a graph vertex.
     */
    public
    void update (Graphics g)
    {
	if (clip != null)
	    g.clipRect(clip.origin.x, clip.origin.y, clip.width, clip.height);
	else
	    g.clearRect(0, 0, width, height);

	paint(g);
    }

    /**
     * Draws the graph at this time of the search.
     */
    public 
    void paint (Graphics g) 
    {
        if (error_message == null)
        {    
            this.g.draw(g);

            g.paint3DRect(0, 0, width - 1, height - 1, false, 
                          suspended || search == null ||
                          (search != null && !search.isAlive()));
        }
        else
            g.drawString("Error: " + error_message, 10, 10);
   }

}