import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
import java.io.*;

import java.util.ArrayList;

import org.w3c.dom.*;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;



/**
 * SimplePaintWithXML is a drawing program in which the user can
 * sketch curves.  The user's work can be saved to a file which can later
 * be reopened and edited.  It is also possible to save the user's
 * picture as an image file.
 * 
 * This version of the program saves the user's work in XML format.
 * @author David J. Eck
 */
public class SimplePaintWithXML extends JFrame {

    /**
     * main routine creates a frame of type SimplePaintWithXML
     * and makes it visible on the screen.
     */
    public static void main(String[] args) {
        JFrame window = new SimplePaintWithXML();
        window.setVisible(true);
    }


    /**
     * Constructor creates a window with a 600-by-600 pixel drawing area and
     * sets its location so that it is centered on the screen.  The window is
     * not resizable.  It is not made visible by this constructor.
     */
    public SimplePaintWithXML() {
        super("SimplePaint: Untitled");
        SimplePaintPanel content = new SimplePaintPanel();
        setContentPane(content);
        setJMenuBar(content.createMenuBar());
        pack();
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        setLocation( (screenSize.width - getWidth())/2 , (screenSize.height - getHeight())/2 );
        setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
        setResizable(false);  
    }



    /**
     * An object of type CurveData represents the data required to redraw one
     * of the curves that have been sketched by the user. 
     */
    private static class CurveData {
        Color color;  // The color of the curve.
        boolean symmetric;  // Are horizontal and vertical reflections also drawn?
        ArrayList<Point> points;  // The points on the curve.
    }


    /**
     * An object of type SimplePaintPanel is used as the drawing area in
     * the window.  This class does all the work of the program.
     */
    private class SimplePaintPanel extends JPanel {

        private ArrayList<CurveData> curves;  // A list of all curves in the picture.

        private Color currentColor;  // When a curve is created, its color is taken
                                     //     from this variable.  The value is changed
                                     //     using commands in the "Color" menu.

        private boolean useSymmetry; // When a curve is created, its "symmetric"
                                     // property is copied from this variable.  Its
                                     // value is set by the "Use Symmetry" command in
                                     // the "Control" menu.

        private File editFile;       // The file that is being edited, if any.
                                     // This is set when the user opens a file.
                                     // The name of the file appears in the
                                     // window's title bar.

        private JFileChooser fileDialog;   // The dialog box for all open/save commands.


        /**
         * Constructor.  Sets background color to white, adds a gray border, sets up
         * a listener for mouse and mouse motion events, and sets the preferred size
         * of the panel to be 600-by-600.
         */
        public SimplePaintPanel() {
            curves = new ArrayList<CurveData>();
            currentColor = Color.BLACK;
            setBackground(Color.WHITE);
            setBorder(BorderFactory.createLineBorder(Color.GRAY, 2));
            MouseHandler listener = new MouseHandler();
            addMouseListener(listener);
            addMouseMotionListener(listener);
            setPreferredSize( new Dimension(600,600) );
        }


        /**
         * This class defines the object that is used as a mouse listener and mouse
         * motion listener on this panel.  When the user presses the mouse, a new
         * CurveData object is created and is added to the ArrayList, curves. The
         * color of the curve is copied from currentColor, and the symmetric property
         * of the curve is copied from useSymmetry.  As the user drags the mouse, points
         * are added to the curve.  If the user doesn't move the mouse, there will only
         * be one point in the list of points; since this is not really a curve, the
         * CurveData object is removed in this case from the curves list in the
         * mouseReleased method.
         */
        private class MouseHandler implements MouseListener, MouseMotionListener {
            CurveData currentCurve;
            boolean dragging;
            public void mousePressed(MouseEvent evt) {
                if (dragging)
                    return;
                dragging = true;
                currentCurve = new CurveData();
                currentCurve.color = currentColor;
                currentCurve.symmetric = useSymmetry;
                currentCurve.points = new ArrayList<Point>();
                currentCurve.points.add( new Point(evt.getX(), evt.getY()) );
                curves.add(currentCurve);
            }
            public void mouseDragged(MouseEvent evt) {
                if (!dragging)
                    return;
                currentCurve.points.add( new Point(evt.getX(),evt.getY()) );
                repaint();  // redraw panel with newly added point.
            }
            public void mouseReleased(MouseEvent evt) {
                if (!dragging)
                    return;
                dragging = false;
                if (currentCurve.points.size() < 2)
                    curves.remove(currentCurve);
                currentCurve = null;
            }
            public void mouseClicked(MouseEvent evt) { }
            public void mouseEntered(MouseEvent evt) { }
            public void mouseExited(MouseEvent evt) { }
            public void mouseMoved(MouseEvent evt) { }
        } // end nested class MouseHandler


        /**
         * Fills the panel with the current background color and draws all the
         * curves that have been sketched by the user.
         */
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            for ( CurveData curve : curves) {
                g.setColor(curve.color);
                for (int i = 1; i < curve.points.size(); i++) {
                        // Draw a line segment from point number i-1 to point number i.
                    int x1 = curve.points.get(i-1).x;
                    int y1 = curve.points.get(i-1).y;
                    int x2 = curve.points.get(i).x;
                    int y2 = curve.points.get(i).y;
                    g.drawLine(x1,y1,x2,y2);
                    if (curve.symmetric) {
                            // Also draw the horizontal and vertical reflections
                            // of the line segment.
                        int w = getWidth();
                        int h = getHeight();
                        g.drawLine(w-x1,y1,w-x2,y2);
                        g.drawLine(x1,h-y1,x2,h-y2);
                        g.drawLine(w-x1,h-y1,w-x2,h-y2);
                    }
                }
            }
        } // end paintComponent()


        /**
         * Creates a menu bar for use with this panel.  It contains
         * four menus: "File, "Control", "Color", and "BackgroundColor".
         */
        public JMenuBar createMenuBar() {

            /* Create the menu bar object */

            JMenuBar menuBar = new JMenuBar();

            /* Create the menus and add them to the menu bar. */

            JMenu fileMenu = new JMenu("File");
            JMenu controlMenu = new JMenu("Control");
            JMenu colorMenu = new JMenu("Color");
            JMenu bgColorMenu = new JMenu("BackgroundColor");
            menuBar.add(fileMenu);
            menuBar.add(controlMenu);
            menuBar.add(colorMenu);
            menuBar.add(bgColorMenu);

            /* Add commands to the "File" menu.  It contains New, Open, and
             * Save commands.  It also contains a command for saving the user's
             * picture as a PNG image and a command for quitting the program.
             */

            JMenuItem newCommand = new JMenuItem("New");
            fileMenu.add(newCommand);
            newCommand.addActionListener( new ActionListener() {
                public void actionPerformed(ActionEvent evt) {
                    curves = new ArrayList<CurveData>();
                    setBackground(Color.WHITE);
                    useSymmetry = false;
                    currentColor = Color.BLACK;
                    setTitle("SimplePaint: Untitled");
                    editFile = null;
                    repaint();
                }
            });
            fileMenu.addSeparator();
            JMenuItem saveXML = new JMenuItem("Save (XML format)...");
            fileMenu.add(saveXML);
            saveXML.addActionListener( new ActionListener() {
                public void actionPerformed(ActionEvent evt) {
                    doSaveAsXML();
                }
            });
            JMenuItem openXML = new JMenuItem("Open (XML format)...");
            fileMenu.add(openXML);
            openXML.addActionListener( new ActionListener() {
                public void actionPerformed(ActionEvent evt) {
                    doOpenAsXML();
                }
            });
            fileMenu.addSeparator();
            JMenuItem saveImage = new JMenuItem("Save Image...");
            fileMenu.add(saveImage);
            saveImage.addActionListener( new ActionListener() {
                public void actionPerformed(ActionEvent evt) {
                    doSaveImage();
                }
            });
            fileMenu.addSeparator();
            JMenuItem quitCommand = new JMenuItem("Quit");
            fileMenu.add(quitCommand);
            quitCommand.addActionListener( new ActionListener() {
                public void actionPerformed(ActionEvent evt) {
                    System.exit(0);
                }
            });


            /* Add commands to the "Control" menu.  It contains an Undo
             * command that will remove the most recently drawn curve
             * from the list of curves; a "Clear" command that removes
             * all the curves that have been drawn; and a "Use Symmetry"
             * checkbox that determines whether symmetry should be used.
             */

            JMenuItem undo = new JMenuItem("Undo");
            controlMenu.add(undo);
            undo.addActionListener( new ActionListener() {
                public void actionPerformed(ActionEvent evt) {
                    if (curves.size() > 0) {
                        curves.remove( curves.size() - 1);
                        repaint();  // Redraw without the curve that has been removed.
                    }
                }
            });
            JMenuItem clear = new JMenuItem("Clear");
            controlMenu.add(clear);
            clear.addActionListener( new ActionListener() {
                public void actionPerformed(ActionEvent evt) {
                    curves = new ArrayList<CurveData>();
                    repaint();  // Redraw with no curves shown.
                }
            });
            JCheckBoxMenuItem sym = new JCheckBoxMenuItem("Use Symmetry");
            controlMenu.add(sym);
            sym.addActionListener( new ActionListener() {
                public void actionPerformed(ActionEvent evt) {
                    useSymmetry = ((JCheckBoxMenuItem)evt.getSource()).isSelected();
                        // This does not affect the current drawing; it affects
                        // curves that are drawn in the future.
                }
            });

            /**
             * Add commands to the "Color" menu.  The menu contains commands for
             * setting the current drawing color.  When the user chooses one of these
             * commands, it has not immediate effect on the drawing.  It just sets
             * the color that will be used for future drawing.
             */

            colorMenu.add(makeColorMenuItem("Black", Color.BLACK));
            colorMenu.add(makeColorMenuItem("White", Color.WHITE));
            colorMenu.add(makeColorMenuItem("Red", Color.RED));
            colorMenu.add(makeColorMenuItem("Green", Color.GREEN));
            colorMenu.add(makeColorMenuItem("Blue", Color.BLUE));
            colorMenu.add(makeColorMenuItem("Cyan", Color.CYAN));
            colorMenu.add(makeColorMenuItem("Magenta", Color.MAGENTA));
            colorMenu.add(makeColorMenuItem("Yellow", Color.YELLOW));
            JMenuItem customColor = new JMenuItem("Custom...");
            colorMenu.add(customColor);
            customColor.addActionListener( new ActionListener() { 
                    // The "Custom..." color command lets the user select the current
                    // drawing color using a JColorChoice dialog.
                public void actionPerformed(ActionEvent evt) {
                    Color c = JColorChooser.showDialog(SimplePaintPanel.this,
                            "Select Drawing Color", currentColor);
                    if (c != null)
                        currentColor = c;
                }
            });

            /**
             * Add commands to the "BackgroundColor" menu.  The menu contains commands
             * for setting the background color of the panel.  When the user chooses
             * one of these commands, the panel is immediately redrawn with the new
             * background color.  Any curves that have been drawn are still there.
             */

            bgColorMenu.add(makeBgColorMenuItem("Black", Color.BLACK));
            bgColorMenu.add(makeBgColorMenuItem("White", Color.WHITE));
            bgColorMenu.add(makeBgColorMenuItem("Red", Color.RED));
            bgColorMenu.add(makeBgColorMenuItem("Green", Color.GREEN));
            bgColorMenu.add(makeBgColorMenuItem("Blue", Color.BLUE));
            bgColorMenu.add(makeBgColorMenuItem("Cyan", Color.CYAN));
            bgColorMenu.add(makeBgColorMenuItem("Magenta", Color.MAGENTA));
            bgColorMenu.add(makeBgColorMenuItem("Yellow", Color.YELLOW));
            JMenuItem customBgColor = new JMenuItem("Custom...");
            bgColorMenu.add(customBgColor);
            customBgColor.addActionListener( new ActionListener() { 
                public void actionPerformed(ActionEvent evt) {
                    Color c = JColorChooser.showDialog(SimplePaintPanel.this,
                            "Select Background Color", getBackground());
                    if (c != null)
                        setBackground(c);
                }
            });

            /* Return the menu bar that has been constructed. */

            return menuBar;

        } // end createMenuBar


        /**
         * This utility method is used to create a JMenuItem that sets the
         * current drawing color.
         * @param command  the text that will appear in the menu
         * @param color  the drawing color that is selected by this command.  (Note that
         *    this parameter is "final" for a technical reason: This is a requirement for
         *    a local variable that is used in an anonymous inner class.)
         * @return  the JMenuItem that has been created.
         */
        private JMenuItem makeBgColorMenuItem(String command, final Color color) {
            JMenuItem item = new JMenuItem(command);
            item.addActionListener( new ActionListener()  {
                public void actionPerformed(ActionEvent evt) {
                    setBackground(color);
                }
            });
            return item;
        }


        /**
         * This utility method is used to create a JMenuItem that sets the
         * background color of the panel.
         * @param command  the text that will appear in the menu
         * @param color  the background color that is selected by this command.
         * @return  the JMenuItem that has been created.
         */
        private JMenuItem makeColorMenuItem(String command, final Color color) {
            JMenuItem item = new JMenuItem(command);
            item.addActionListener( new ActionListener()  {
                public void actionPerformed(ActionEvent evt) {
                    currentColor = color;
                }
            });
            return item;
        }


        /**
         * Save the user's image to a file in XML format. Files created by this method
         * can be read back into the program using the doOpenAsXML() method.
         */
        private void doSaveAsXML() {
            if (fileDialog == null)      
                fileDialog = new JFileChooser(); 
            File selectedFile;  //Initially selected file name in the dialog.
            if (editFile == null)
                selectedFile = new File("sketchData.xml");
            else
                selectedFile = new File(editFile.getName());
            fileDialog.setSelectedFile(selectedFile); 
            fileDialog.setDialogTitle("Select File to be Saved");
            int option = fileDialog.showSaveDialog(this);
            if (option != JFileChooser.APPROVE_OPTION)
                return;  // User canceled or clicked the dialog's close box.
            selectedFile = fileDialog.getSelectedFile();
            if (selectedFile.exists()) {  // Ask the user whether to replace the file.
                int response = JOptionPane.showConfirmDialog( this,
                        "The file \"" + selectedFile.getName()
                        + "\" already exists.\nDo you want to replace it?", 
                        "Confirm Save",
                        JOptionPane.YES_NO_OPTION, 
                        JOptionPane.WARNING_MESSAGE );
                if (response != JOptionPane.YES_OPTION)
                    return;  // User does not want to replace the file.
            }
            PrintWriter out; 
            try {
                FileOutputStream stream = new FileOutputStream(selectedFile); 
                out = new PrintWriter( stream );
            }
            catch (Exception e) {
                JOptionPane.showMessageDialog(this,
                        "Sorry, but an error occurred while trying to open the file:\n" + e);
                return;
            }
            try {
                out.println("<?xml version=\"1.0\"?>");
                out.println("<simplepaint version=\"1.0\">");
                Color bgColor = getBackground();
                out.println("   <background red='" + bgColor.getRed() + "' green='" +
                        bgColor.getGreen() + "' blue='" + bgColor.getBlue() + "'/>");
                for (CurveData c : curves) {
                    out.println("   <curve>");
                    out.println("      <color red='" + c.color.getRed() + "' green='" +
                            c.color.getGreen() + "' blue='" + c.color.getBlue() + "'/>");
                    out.println("      <symmetric>" + c.symmetric + "</symmetric>");
                    for (Point pt : c.points)
                        out.println("      <point x='" + pt.x + "' y='" + pt.y + "'/>");
                    out.println("   </curve>");
                }
                out.println("</simplepaint>");
                out.close();
                editFile = selectedFile;
                setTitle("SimplePaint: " + editFile.getName());
            }
            catch (Exception e) {
                JOptionPane.showMessageDialog(this,
                        "Sorry, but an error occurred while trying to write the text:\n" + e);
            }    
        }


        /**
         * Read image data from a file into the drawing area.  The format
         * of the file must be the same as that used in the doSaveAsXML()
         * method.
         */
        private void doOpenAsXML() {
            if (fileDialog == null)
                fileDialog = new JFileChooser();
            fileDialog.setDialogTitle("Select File to be Opened");
            fileDialog.setSelectedFile(null);  // No file is initially selected.
            int option = fileDialog.showOpenDialog(this);
            if (option != JFileChooser.APPROVE_OPTION)
                return;  // User canceled or clicked the dialog's close box.
            File selectedFile = fileDialog.getSelectedFile();
            Document xmldoc;
            try {
                DocumentBuilder docReader = DocumentBuilderFactory.newInstance().newDocumentBuilder();
                xmldoc = docReader.parse(selectedFile);
            }
            catch (Exception e) {
                JOptionPane.showMessageDialog(this,
                        "Sorry, but an error occurred while trying to read the file:\n" + e);
                return;
            }
            try {
                Color newBackground = Color.WHITE;
                ArrayList<CurveData> newCurves = new ArrayList<CurveData>();
                Element rootElement = xmldoc.getDocumentElement();
                if ( ! rootElement.getNodeName().equals("simplepaint") )
                    throw new Exception("File is not a SimplePaint file.");
                String version = rootElement.getAttribute("version");
                try {
                    double versionNumber = Double.parseDouble(version);
                    if (versionNumber > 1.0)
                        throw new Exception("File requires a newer version of SimplePaint.");
                }
                catch (NumberFormatException e) {
                }
                NodeList nodes = rootElement.getChildNodes();
                for (int i = 0; i < nodes.getLength(); i++) {
                    if (nodes.item(i) instanceof Element) {
                        Element element = (Element)nodes.item(i);
                        if (element.getTagName().equals("background")) {
                            int r = Integer.parseInt(element.getAttribute("red"));
                            int g = Integer.parseInt(element.getAttribute("green"));
                            int b = Integer.parseInt(element.getAttribute("blue"));
                            newBackground = new Color(r,g,b);
                        }
                        else if (element.getTagName().equals("curve")) {
                            CurveData curve = new CurveData();
                            curve.color = Color.BLACK;
                            curve.points = new ArrayList<Point>();
                            newCurves.add(curve);
                            NodeList curveNodes = element.getChildNodes();
                            for (int j = 0; j < curveNodes.getLength(); j++) {
                                if (curveNodes.item(j) instanceof Element) {
                                    Element curveElement = (Element)curveNodes.item(j);
                                    if (curveElement.getTagName().equals("color")) {
                                        int r = Integer.parseInt(curveElement.getAttribute("red"));
                                        int g = Integer.parseInt(curveElement.getAttribute("green"));
                                        int b = Integer.parseInt(curveElement.getAttribute("blue"));
                                        curve.color = new Color(r,g,b);
                                    }
                                    else if (curveElement.getTagName().equals("point")) {
                                        int x = Integer.parseInt(curveElement.getAttribute("x"));
                                        int y = Integer.parseInt(curveElement.getAttribute("y"));
                                        curve.points.add(new Point(x,y));
                                    }
                                    else if (curveElement.getTagName().equals("symmetric")) {
                                        String content = curveElement.getTextContent();
                                        if (content.equals("true"))
                                            curve.symmetric = true;
                                    }
                                }
                            }
                        }
                    }
                }
                curves = newCurves;
                setBackground(newBackground);
                repaint();
                editFile = selectedFile;
                setTitle("SimplePaint: " + editFile.getName());
            }
            catch (Exception e) {
                JOptionPane.showMessageDialog(this,
                        "Sorry, but an error occurred while trying to read the data:\n" + e);
            }    
        }


        /**
         * Saves the user's sketch as an image file in PNG format.
         */
        private void doSaveImage() {
            if (fileDialog == null)      
                fileDialog = new JFileChooser(); 
            fileDialog.setSelectedFile(new File("sketch.png")); 
            fileDialog.setDialogTitle("Select File to be Saved");
            int option = fileDialog.showSaveDialog(this);
            if (option != JFileChooser.APPROVE_OPTION)
                return;  // User canceled or clicked the dialog's close box.
            File selectedFile = fileDialog.getSelectedFile();
            if (selectedFile.exists()) {  // Ask the user whether to replace the file.
                int response = JOptionPane.showConfirmDialog( this,
                        "The file \"" + selectedFile.getName()
                        + "\" already exists.\nDo you want to replace it?", 
                        "Confirm Save",
                        JOptionPane.YES_NO_OPTION, 
                        JOptionPane.WARNING_MESSAGE );
                if (response != JOptionPane.YES_OPTION)
                    return;  // User does not want to replace the file.
            }
            try {
                BufferedImage image;  // A copy of the sketch will be drawn here.
                image = new BufferedImage(600,600,BufferedImage.TYPE_INT_RGB);
                Graphics g = image.getGraphics();  // For drawing onto the image.
                paintComponent(g);
                g.dispose();
                boolean hasPNG = ImageIO.write(image,"PNG",selectedFile);
                if ( ! hasPNG )
                    throw new Exception("PNG format not available.");
            }
            catch (Exception e) {
                JOptionPane.showMessageDialog(this,
                        "Sorry, but an error occurred while trying to write the image:\n" + e);
            }    
        }


    }

} // end SimplePaintWithXML