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

import java.io.File;

import java.util.List;
import java.util.ArrayList;
import java.util.Iterator;

/**
 * ImageViewer is the main class of the image viewer application. It builds and
 * displays the application GUI and initialises all other components.
 *
 * To start the application, create an object of this class.
 *
 * @author Gede
 * @version 3.0(29/11/2018)
 */
public class ImageViewer
{
    // static fields:
    private static final String VERSION = "Version 3.0";
    private static JFileChooser fileChooser = new JFileChooser(System.getProperty("user.dir"));

    // fields:
    private JFrame frame;
    private ImagePanel imagePanel;
    private JLabel filenameLabel;
    private JLabel statusLabel;
    private JButton smallerButton;
    private JButton largerButton;
    private OFImage currentImage;

    private List<Filter> filters;

    /**
     * Create an ImageViewer and display its GUI on screen.
     */
    public ImageViewer()
    {
        currentImage = null;
        filters = createFilters();
        makeFrame();
    }


    // ---- implementation of menu functions ----

    /**
     * Open function: open a file chooser to select a new image file,
     * and then display the chosen image.
     */
    private void openFile()
    {
        int returnVal = fileChooser.showOpenDialog(frame);

        if(returnVal != JFileChooser.APPROVE_OPTION) {
            return;  // cancelled
        }
        File selectedFile = fileChooser.getSelectedFile();
        currentImage = ImageFileManager.loadImage(selectedFile);

        if(currentImage == null) {   // image file was not a valid image
            JOptionPane.showMessageDialog(frame,
                    "The file was not in a recognized image file format.",
                    "Image Load Error",
                    JOptionPane.ERROR_MESSAGE);
            return;
        }

        imagePanel.setImage(currentImage);
        setButtonsEnabled(true);
        showFilename(selectedFile.getPath());
        showStatus("File loaded.");
        frame.pack();
    }

    /**
     * Close function: close the current image.
     */
    private void close()
    {
        currentImage = null;
        imagePanel.clearImage();
        showFilename(null);
        setButtonsEnabled(false);
    }

    /**
     * Save As function: save the current image to a file.
     */
    private void saveAs()
    {
        if(currentImage != null) {
            int returnVal = fileChooser.showSaveDialog(frame);

            if(returnVal != JFileChooser.APPROVE_OPTION) {
                return;  // cancelled
            }
            File selectedFile = fileChooser.getSelectedFile();
            ImageFileManager.saveImage(currentImage, selectedFile);

            showFilename(selectedFile.getPath());
        }
    }

    /**
     * Quit function: quit the application.
     */
    private void quit()
    {
        System.exit(0);
    }

    /**
     * Apply a given filter to the current image.
     *
     * @param filter   The filter object to be applied.
     */
    private void applyFilter(Filter filter)
    {
        if(currentImage != null) {
            filter.apply(currentImage);
            frame.repaint();
            showStatus("Applied: " + filter.getName());
        }
        else {
            showStatus("No image loaded.");
        }
    }

    /**
     * 'About' function: show the 'about' box.
     */
    private void showAbout()
    {
        JOptionPane.showMessageDialog(frame,
                    "ImageViewer\n" + VERSION,
                    "About ImageViewer",
                    JOptionPane.INFORMATION_MESSAGE);
    }

    /**
     * Make the current picture larger.
     */
    private void makeLarger()
    {
        if(currentImage != null) {
            // create new image with double size
            int width = currentImage.getWidth();
            int height = currentImage.getHeight();
            OFImage newImage = new OFImage(width * 2, height * 2);

            // copy pixel data into new image
            for(int y = 0; y < height; y++) {
                for(int x = 0; x < width; x++) {
                    Color col = currentImage.getPixel(x, y);
                    newImage.setPixel(x * 2, y * 2, col);
                    newImage.setPixel(x * 2 + 1, y * 2, col);
                    newImage.setPixel(x * 2, y * 2 + 1, col);
                    newImage.setPixel(x * 2+1, y * 2 + 1, col);
                }
            }

            currentImage = newImage;
            imagePanel.setImage(currentImage);
            frame.pack();
        }
    }

    /**
     * Make the current picture smaller.
     */
    private void makeSmaller()
    {
        if(currentImage != null) {
            // create new image with double size
            int width = currentImage.getWidth() / 2;
            int height = currentImage.getHeight() / 2;
            OFImage newImage = new OFImage(width, height);

            // copy pixel data into new image
            for(int y = 0; y < height; y++) {
                for(int x = 0; x < width; x++) {
                    newImage.setPixel(x, y, currentImage.getPixel(x * 2, y * 2));
                }
            }

            currentImage = newImage;
            imagePanel.setImage(currentImage);
            frame.pack();
        }
    }

    // ---- support methods ----

    /**
     * Show the file name of the current image in the fils display label.
     * 'null' may be used as a parameter if no file is currently loaded.
     *
     * @param filename  The file name to be displayed, or null for 'no file'.
     */
    private void showFilename(String filename)
    {
        if(filename == null) {
            filenameLabel.setText("No file displayed.");
        }
        else {
            filenameLabel.setText("File: " + filename);
        }
    }

    /**
     * Show a message in the status bar at the bottom of the screen.
     * @param text The message to be displayed.
     */
    private void showStatus(String text)
    {
        statusLabel.setText(text);
    }

    /**
     * Enable or disable all toolbar buttons.
     *
     * @param status  'true' to enable the buttons, 'false' to disable.
     */
    private void setButtonsEnabled(boolean status)
    {
        smallerButton.setEnabled(status);
        largerButton.setEnabled(status);
    }

    /**
     * Create a list with all the known filters.
     * @return The list of filters.
     */
    private List<Filter> createFilters()
    {
        List<Filter> filterList = new ArrayList<Filter>();
        filterList.add(new DarkerFilter("Darker"));
        filterList.add(new LighterFilter("Lighter"));
        filterList.add(new ThresholdFilter("Threshold"));
        filterList.add(new FishEyeFilter("Fish Eye"));

        return filterList;
    }

    // ---- swing stuff to build the frame and all its components ----

    /**
     * Create the Swing frame and its content.
     */
    private void makeFrame()
    {
        frame = new JFrame("ImageViewer");
        JPanel contentPane = (JPanel)frame.getContentPane();
        contentPane.setBorder(new EmptyBorder(6, 6, 6, 6));

        makeMenuBar(frame);

        // Specify the layout manager with nice spacing
        contentPane.setLayout(new BorderLayout(6, 6));

        // Create the image pane in the center
        imagePanel = new ImagePanel();
        imagePanel.setBorder(new EtchedBorder());
        contentPane.add(imagePanel, BorderLayout.CENTER);

        // Create two labels at top and bottom for the file name and status message
        filenameLabel = new JLabel();
        contentPane.add(filenameLabel, BorderLayout.NORTH);

        statusLabel = new JLabel(VERSION);
        contentPane.add(statusLabel, BorderLayout.SOUTH);

        // Create the toolbar with the buttons
        JPanel toolbar = new JPanel();
        toolbar.setLayout(new GridLayout(0, 1));

        smallerButton = new JButton("Smaller");
        smallerButton.addActionListener(new ActionListener() {
                               public void actionPerformed(ActionEvent e) { makeSmaller(); }
                           });
        toolbar.add(smallerButton);

        largerButton = new JButton("Larger");
        largerButton.addActionListener(new ActionListener() {
                               public void actionPerformed(ActionEvent e) { makeLarger(); }
                           });
        toolbar.add(largerButton);

        // Add toolbar into panel with flow layout for spacing
        JPanel flow = new JPanel();
        flow.add(toolbar);

        contentPane.add(flow, BorderLayout.WEST);

        // building is done - arrange the components
        showFilename(null);
        setButtonsEnabled(false);
        frame.pack();

        // place the frame at the center of the screen and show
        Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
        frame.setLocation(d.width/2 - frame.getWidth()/2, d.height/2 - frame.getHeight()/2);
        frame.setVisible(true);
    }

    /**
     * Create the main frame's menu bar.
     *
     * @param frame   The frame that the menu bar should be added to.
     */
    private void makeMenuBar(JFrame frame)
    {
        final int SHORTCUT_MASK =
            Toolkit.getDefaultToolkit().getMenuShortcutKeyMask();

        JMenuBar menubar = new JMenuBar();
        frame.setJMenuBar(menubar);

        JMenu menu;
        JMenuItem item;

        // create the File menu
        menu = new JMenu("File");
        menubar.add(menu);

        item = new JMenuItem("Open...");
            item.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_O, SHORTCUT_MASK));
            item.addActionListener(new ActionListener() {
                               public void actionPerformed(ActionEvent e) { openFile(); }
                           });
        menu.add(item);

        item = new JMenuItem("Close");
            item.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_W, SHORTCUT_MASK));
            item.addActionListener(new ActionListener() {
                               public void actionPerformed(ActionEvent e) { close(); }
                           });
        menu.add(item);
        menu.addSeparator();

        item = new JMenuItem("Save As...");
            item.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_S, SHORTCUT_MASK));
            item.addActionListener(new ActionListener() {
                               public void actionPerformed(ActionEvent e) { saveAs(); }
                           });
        menu.add(item);
        menu.addSeparator();

        item = new JMenuItem("Quit");
            item.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_Q, SHORTCUT_MASK));
            item.addActionListener(new ActionListener() {
                               public void actionPerformed(ActionEvent e) { quit(); }
                           });
        menu.add(item);

        // create the Filter menu
        menu = new JMenu("Filter");
        menubar.add(menu);

        for(final Filter filter : filters) {
            item = new JMenuItem(filter.getName());
            item.addActionListener(new ActionListener() {
                                public void actionPerformed(ActionEvent e) {
                                    applyFilter(filter);
                                }
                           });
             menu.add(item);
         }

        // create the Help menu
        menu = new JMenu("Help");
        menubar.add(menu);

        item = new JMenuItem("About ImageViewer...");
            item.addActionListener(new ActionListener() {
                               public void actionPerformed(ActionEvent e) { showAbout(); }
                           });
        menu.add(item);
    }
}