src/main/java/de/uapcore/sudoku/ActionHandler.java

/*
 * Copyright 2013 Mike Becker. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

package de.uapcore.sudoku;

import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.IOException;

/**
 * Handles all user issued actions in the application.
 */
public final class ActionHandler implements ActionListener {

    public static final String SAVE = "save";
    public static final String CHECK = "check";
    public static final String SOLVE = "solve";

    public static final String NEW = "new";
    public static final String OPEN = "open";
    public static final String SAVE_AS = "save as";
    public static final String QUIT = "quit";
    public static final String ABOUT = "about";

    private final Field field;
    private final Solver solver;
    private final DocumentHandler doc;

    /**
     * Constructs a new action handler instance.
     *
     * @param f a reference to the playing field
     */
    public ActionHandler(Field f) {
        field = f;
        solver = new Solver();
        doc = new DocumentHandler();
    }

    /**
     * Prompts the user for a file name.
     * <p>
     * If the user chooses an existing file, they are asked whether the file should be overwritten.
     *
     * @return true if the user approves a chosen file name
     */
    private boolean chooseSaveFilename() {
        JFileChooser fc = new JFileChooser(".");
        fc.setMultiSelectionEnabled(false);
        if (fc.showSaveDialog(field) == JFileChooser.APPROVE_OPTION) {
            File f = fc.getSelectedFile();
            if (f.exists()) {
                int result = JOptionPane.showConfirmDialog(field,
                        "Bereits existierende Datei überschreiben?", "Sudoku",
                        JOptionPane.YES_NO_OPTION);
                if (result == JOptionPane.YES_OPTION) {
                    doc.setFilename(f.getAbsolutePath());
                    return true;
                } else {
                    return false;
                }
            } else {
                doc.setFilename(f.getAbsolutePath());
                return true;
            }
        } else {
            return false;
        }
    }

    /**
     * Prompts the user for a file to open and, if approved, loads that file.
     */
    private void open() {
        JFileChooser fc = new JFileChooser(".");
        fc.setMultiSelectionEnabled(false);
        if (fc.showOpenDialog(field) == JFileChooser.APPROVE_OPTION) {
            File f = fc.getSelectedFile();
            doc.setFilename(f.getAbsolutePath());
            try {
                doc.load(field);
            } catch (IOException e) {
                JOptionPane.showMessageDialog(field,
                        "Datei konnte nicht geladen werden: " + e.getMessage(),
                        "Sudoku", JOptionPane.ERROR_MESSAGE);
            }
        }
    }

    /**
     * Attempts to save the Sudoku field to a file.
     * <p>
     * If necessary, the user is prompted for a file name.
     * <p>
     * The field must be solvable, otherwise it cannot be saved.
     *
     * @param rename true if the user shall always be prompted, even if a file name is already known
     * @return true if the user approves the chosen file name
     */
    private boolean save(boolean rename) {
        if (!doc.isFilenameSet() || rename) {
            if (!chooseSaveFilename()) {
                return false;
            }
        }
        if (solver.check(field)) {
            try {
                doc.save(field);
            } catch (IOException e) {
                JOptionPane.showMessageDialog(field,
                        "Datei konnte nicht gespeichert werden: " + e.getMessage(),
                        "Sudoku", JOptionPane.ERROR_MESSAGE);
            }
            return true;
        } else {
            JOptionPane.showMessageDialog(field,
                    "Das Feld kann mit Fehlern nicht gespeichert werden!",
                    "Sudoku", JOptionPane.ERROR_MESSAGE);
            return false;
        }
    }

    /**
     * Checks the Sudoku field and displays the result as a dialog box.
     */
    private void check() {
        if (solver.check(field)) {
            JOptionPane.showMessageDialog(field, "Überprüfung erfolgreich!",
                    "Sudoku", JOptionPane.INFORMATION_MESSAGE);
        } else {
            JOptionPane.showMessageDialog(field, "Das Feld enthält Fehler!",
                    "Sudoku", JOptionPane.WARNING_MESSAGE);
        }
    }

    /**
     * Solves the field or displays an error dialog if the field is not solvable.
     */
    private void solve() {
        if (!solver.check(field) || !solver.solve(field)) {
            JOptionPane.showMessageDialog(field, "Das Feld ist nicht lösbar!",
                    "Sudoku", JOptionPane.WARNING_MESSAGE);
        }
    }

    /**
     * Checks whether there are unsaved changes and asks the user to save the field.
     *
     * @return true if there are no unsaved changes or the user actively decides to continue - false, otherwise
     */
    private boolean saveUnsaved() {
        boolean proceed = false;
        if (field.isAnyCellModified()) {
            int result = JOptionPane.showConfirmDialog(field,
                    "Das Feld ist ungespeichert - jetzt speichern?",
                    "Sudoku", JOptionPane.YES_NO_CANCEL_OPTION);
            if (result == JOptionPane.YES_OPTION) {
                if (save(false)) {
                    proceed = true;
                }
            } else if (result == JOptionPane.NO_OPTION) {
                proceed = true;
            }
        } else {
            proceed = true;
        }

        return proceed;
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        switch (e.getActionCommand()) {
            case NEW:
                if (saveUnsaved()) {
                    doc.clearFilename();
                    field.clear();
                }
                break;
            case OPEN:
                open();
                break;
            case SAVE:
                save(false);
                break;
            case SAVE_AS:
                save(true);
                break;
            case CHECK:
                check();
                break;
            case SOLVE:
                solve();
                break;
            case QUIT:
                if (saveUnsaved()) {
                    System.exit(0);
                }
                break;
            case ABOUT:
                JOptionPane.showMessageDialog(field,
                        "Sudoku - Copyright (c) 2013 Mike Becker\nwww.uap-core.de" +
                                "\nPublished under the BSD License",
                        "Sudoku", JOptionPane.INFORMATION_MESSAGE);
                break;
            default:
                throw new UnsupportedOperationException(
                        "unknown action: " + e.getActionCommand());
        }
    }

}