package edu.hws.eck.mdb;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.StringTokenizer;
import java.util.prefs.*;

/**
 * This class is used to run the Mandelbrot viewer program as a standalone
 * application.  The main routine creates a window of type MandelbrotFrame.
 * and shows it on the screen.  This class also works with "preferences."
 * When the program exits, it saves the current window size and location to
 * the user's Java preferences.  It also saves the currently selected
 * directory in the JFileChooser that is used when the user saves and opens
 * files.   These values are restored from the user's preferences the next time 
 * the program starts.
 */
public class Main {

    public static void main(String[] args) {
        final MandelbrotFrame frame = new MandelbrotFrame();
        applyPreferences(frame);
        frame.adjustToScreenIfNecessary();
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.addWindowListener( new WindowAdapter() {
                 // When the window is disposed, this event handler will
                 // be notified.  It will save current settings to the
                 // user's preferences and terminate the program.
            public void windowClosed(WindowEvent evt) {
                frame.getMandelbrotPanel().getDisplay().shutDownThreads();
                savePreferences(frame);
                System.exit(0);
            }
        });
        frame.setVisible(true);
    }

    
    /**
     * Called when the program ends to try to save window bounds and current
     * directory to user's preferences, so they can be restored the next
     * time the program is run.  Since this is not a critical function, errors
     * are ignored.  If an error occurs, the data simply won't be saved.
     */
    private static void savePreferences(MandelbrotFrame frame) {
        try {
            String pathName = "/edu/hws/eck/mdb";
               // The pathname uniquely identifies this program.  (It is unique
               // because it comes from the package name, which should not be used
               // for any other program under Java's package naming guidelines.
            Preferences root = Preferences.userRoot();
            Preferences node = root.node(pathName);
               // This "node" holds the preferences associated with the pathName.
               // Preferences take the form of key/value pairs, with put() and
               // get() operations for changing/reading values.
            Rectangle bounds = frame.getBounds();
            String boundsString = bounds.x + "," + bounds.y + "," 
                                        + bounds.width + "," + bounds.height;
            node.put("mandelbrot.window.bounds", boundsString);  
            Menus menus = (Menus)frame.getJMenuBar();
            String currentDir = menus.getSelectedDirectoryInFileChooser();
            if (currentDir != null)
                node.put("mandelbort.filechooser.directory", currentDir); 
        }
        catch (Exception e) {
        }
    }
    
    
    /**
     * This method is called when the program starts to read and apply the
     * preferences that were saved the last time the program ran.  Since
     * this is not a critical function, errors are ignored.  If an error
     * occurs, preferences will simply not be restored.
     */
    private static void applyPreferences(MandelbrotFrame frame) {
        try {
            String pathName = "/edu/hws/eck/mdb";  // Identifies prefs for this program.
            Preferences root = Preferences.userRoot();
            if (! root.nodeExists(pathName) )
                return;  // There are no saved prefs for this program yet.
            Preferences node = root.node(pathName);
            String boundsString = node.get("mandelbrot.window.bounds",null);
            if (boundsString != null) {
                   // Try to restore window bounds, ignoring any error.
                String[] bounds = explode(boundsString,",");
                try {
                    int x = Integer.parseInt(bounds[0]);
                    int y = Integer.parseInt(bounds[1]);
                    int w = Integer.parseInt(bounds[2]);
                    int h = Integer.parseInt(bounds[3]);
                    if (w > 5000 || h > 5000)
                        throw new NumberFormatException();  // unreasonable values.
                    frame.setBounds(x,y,w,h);
                    frame.adjustToScreenIfNecessary();
                }
                catch (NumberFormatException e) {
                }
            }
            Menus menus = (Menus)frame.getJMenuBar();
            String directory = node.get("mandelbort.filechooser.directory", null);
            if (directory != null) {
                   // Try to restore the current directory.
                menus.setSelectedDirectoryInFileChooser(directory);
            }
        }
        catch (Exception e) {
        }
    }
    
    
    /**
     * A convenience method that breaks up a string into tokens, where
     * the tokens are substrings separated by specified delimiters.
     * For example, explode("ab,cde,f,ghij", ",") produces an array
     * of the four substrings "ab"  "cde"  "f"  "ghi".
     */
    private static String[] explode(String str, String separators) {
        StringTokenizer tokenizer = new StringTokenizer(str, separators);
        int ct = tokenizer.countTokens();
        String[] tokens = new String[ct];
        for (int i = 0; i < ct; i++)
            tokens[i] = tokenizer.nextToken();
        return tokens;
    }
    
}
