/*
 * #%L
 * gitools-ui-platform
 * %%
 * Copyright (C) 2013 Universitat Pompeu Fabra - Biomedical Genomics group
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as
 * published by the Free Software Foundation, either version 3 of the 
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public 
 * License along with this program.  If not, see
 * <http://www.gnu.org/licenses/gpl-3.0.html>.
 * #L%
 */
package org.gitools.ui.platform.imageviewer;

import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.event.EventListenerList;

/**
 * Stores the x and y coordinate of a pixel. Either both coordinate is positive or zero, indicating a valid pixel,
 * or both are -1, indicating no pixel is selected or should be shown.
 *
 * @author Kazó Csaba
 */
public class PixelModel {

    private final EventListenerList listenerList = new EventListenerList();
    private int x = -1, y = -1;

    /**
     * Adds a {@code ChangeListener} to the model.
     *
     * @param listener the listener to add
     */
    public void addChangeListener(ChangeListener listener) {
        listenerList.add(ChangeListener.class, listener);
    }

    /**
     * Removes a {@code ChangeListener} from the model.
     *
     * @param listener the listener to remove
     */
    public void removeChangeListener(ChangeListener listener) {
        listenerList.remove(ChangeListener.class, listener);
    }

    /**
     * Notifies the registered listeners that the model has changed.
     */
    protected void fireChange() {
        Object[] listeners = listenerList.getListenerList();
        ChangeEvent event = new ChangeEvent(this);
        for (int i = listeners.length - 2; i >= 0; i -= 2) {
            if (listeners[i] == ChangeListener.class) {
                ((ChangeListener) listeners[i + 1]).stateChanged(event);
            }
        }
    }

    /**
     * Changes the pixel stored in this model. If either coordinate is negative, the new value of the model will be
     * (-1, -1).
     *
     * @param x the new x coordinate
     * @param y the new y coordinate
     */
    public void set(int x, int y) {
        if (x < 0 || y < 0) {
            x = -1;
            y = -1;
        }
        if (this.x != x || this.y != y) {
            this.x = x;
            this.y = y;
            fireChange();
        }
    }

    /**
     * Returns the current x coordinate.
     *
     * @return the x coordinate
     */
    public int getX() {
        return x;
    }

    /**
     * Returns the current y coordinate.
     *
     * @return the y coordinate
     */
    public int getY() {
        return y;
    }

    /**
     * Returns whether the pixel is marked as invalid by setting one of the coordinates to -1.
     *
     * @return {@code true} if the model does not have a valid pixel
     */
    public boolean isInvalid() {
        return x < 0;
    }
}