import java.awt.Component;
import java.awt.KeyboardFocusManager;
import java.awt.Toolkit;
import javax.swing.LookAndFeel;
import javax.swing.UIManager;
import javax.swing.text.*;

/**
 *  A single DocumentFilter can be set on an AbstractDocument. There may be
 *  times when you wish to perform multiple filtering of the data as it is
 *  added to a Document. By extending the ChainedDocumentFilter instead of
 *  the DocumentFilter you will receive added flexibility in that the
 *  filter can be used stand alone or with other ChainedDocumentFilters.
 *
 *  Whenever one filter step fails, the chaining of the filters is also
 *  terminated. In this case is it recommended you invoke the
 *  provideErrorFeedback() method to provide user feedback.
 */
abstract class ChainedDocumentFilter extends DocumentFilter
{
	private DocumentFilter filter;

	/**
	 *  Standard constructor for standalone usage
	 */
	public ChainedDocumentFilter()
	{
		this( null );
	}

	/**
	 *	Constructor used when further filtering is required after this
	 *  filter has been applied.
	 */
	public ChainedDocumentFilter(DocumentFilter filter)
	{
		setFilter( filter );
	}

	/**
	 *  Get the next filter in the chain.
	 *
	 *  @return the next filter in the chain
	 */
	public DocumentFilter getFilter()
	{
		return filter;
	}

	/**
	 *	Set the next filter in the chain
	 *
	 *  @param filter
	 */
	public void setFilter(DocumentFilter filter)
	{
		this.filter = filter;
	}

	/**
	 *  Install this filter on the AbstractDocument
	 *
	 *  @param components the text components that will use this filter
	 */
	public void installFilter(JTextComponent... components)
	{
		for (JTextComponent component : components)
		{
			Document doc = component.getDocument();

			if (doc instanceof AbstractDocument)
			{
				((AbstractDocument)doc).setDocumentFilter( this );
			}
		}
	}

	/**
	 *  Remove this filter from the AbstractDocument
	 *
	 *  @param compoents remove the filter from the specified text components
	 */
	public void uninstallFilter(JTextComponent... components)
	{
		for (JTextComponent component : components)
		{
			Document doc = component.getDocument();

			if (doc instanceof AbstractDocument)
			{
				((AbstractDocument)doc).setDocumentFilter( null );
			}
		}
	}

	/**
	 *	Provide appropriate LAF feedback when a filter error occurs.
	 */
	public void provideErrorFeedback()
	{
		LookAndFeel laf = UIManager.getLookAndFeel();

		if (laf == null)
		{
			Toolkit.getDefaultToolkit().beep();
		}
		else
		{
			KeyboardFocusManager fm = KeyboardFocusManager.getCurrentKeyboardFocusManager();
			Component component = fm.getFocusOwner();
			laf.provideErrorFeedback( component );
		}
	}

	@Override
	public void insertString(FilterBypass fb, int offs, String str, AttributeSet a)
		throws BadLocationException
	{
		if (filter == null)
			super.insertString(fb, offs, str, a);
		else
			filter.insertString(fb, offs, str, a);
	}

	@Override
	public void replace(FilterBypass fb, int offs, int length, String str, AttributeSet a)
		throws BadLocationException
	{
		if (filter == null)
			super.replace(fb, offs, length, str, a);
		else
			filter.replace(fb, offs, length, str, a);
	}

	@Override
	public void remove(DocumentFilter.FilterBypass fb, int offset, int length)
		throws BadLocationException
	{
		if (filter == null)
			super.remove(fb, offset, length);
		else
			filter.remove(fb, offset, length);
	}
}