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

/**
 *  This class will retain the caret positioning at the character where
 *  the mouse was clicked.
 */
public class CaretPositionListener implements MouseListener
{
	private boolean dynamicFormatting;

	/**
	 *  Default constructor.
	 */
	public CaretPositionListener()
	{
	}

	/**
	 *  Convenience constructor. This class is automatically added as a
	 *  MouseListener to the specified formatted text fields.
	 */
	public CaretPositionListener(JFormattedTextField... components)
	{
		registerComponent( components );
	}

	/**
	 *
	 */
	public boolean isDynamicFormatting()
	{
		return dynamicFormatting;
	}

	/**
	 *  Indicates that the formatting of the text in the formatted text field
	 *  can change depending on whether the	text field has focus or not.
	 *  The listner must be aware of this so the proper caret position can
	 *  be calculated.
	 *
	 *  @param dynamicFormatting when true dynamic formatting must be considered
	 */
	public void setDynamicFormatting(boolean dynamicFormatting)
	{
		this.dynamicFormatting = dynamicFormatting;
	}


	/**
	 *  Remove listeners from the specified component
	 *
	 *  @param component  the component the listeners are removed from
	 */
	public void deregisterComponent(JFormattedTextField... components)
	{
		for (JFormattedTextField component : components)
			component.removeMouseListener( this );
	}

	/**
	 *  Add the required listeners to the specified component
	 *
	 *  @param component  the component the listeners are added to
	 */
	public void registerComponent(JFormattedTextField... components)
	{
		for (JFormattedTextField component : components)
			component.addMouseListener( this );
	}

	public void mousePressed(final MouseEvent me)
	{
		//  Ignore double click to allow default behavour which will
		//  select the entire text

		if (me.getClickCount() > 1) return;

		final JFormattedTextField ftf = (JFormattedTextField)me.getSource();

		if (dynamicFormatting
		&&  ftf.getValue() != null)
		{
			determineCaretPosition(ftf);
		}
		else
		{
			int offset = ftf.getCaretPosition();
			setCaretPosition(ftf, offset);
		}
	}

	private void determineCaretPosition(final JFormattedTextField ftf)
	{
		int offset = ftf.getCaretPosition();
		String text = ftf.getText();
		String value = ftf.getValue().toString();

		if (text.equals(value))
		{
			setCaretPosition(ftf, offset);
			return;
		}

		int i = 0;
		int j = 0;

		//  Exclude formatting characters

		while (j < offset)
		{
			if (text.charAt(i) == value.charAt(j))
			{
				i++;
				j++;
			}
			else
			{
				offset--;
				i++;
			}
		}

		setCaretPosition(ftf, offset);
	}

	private void setCaretPosition(final JFormattedTextField ftf, final int offset)
	{
		SwingUtilities.invokeLater(new Runnable()
		{
			public void run()
			{
				try
				{
					ftf.setCaretPosition(offset);
				}
				catch (IllegalArgumentException e) {}
			}
		});
	}

	public void mouseClicked(MouseEvent e) {}
	public void mouseEntered(MouseEvent e) {}
	public void mouseExited(MouseEvent e) {}
	public void mouseReleased( MouseEvent e ) {}
}