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

/*
 *  This class listens for changes made to the data in the table via the
 *  TableCellEditor. When editing is started, the value of the cell is saved
 *  When editing is stopped the new value is saved. When the oold and new
 *  values are different, then the provided Action is invoked.
 *
 *  The source of the Action is a TableCellListener instance.
 */
public class TableCellListener implements PropertyChangeListener, Runnable
{
	private JTable table;
	private Action action;

	private int row;
	private int column;
	private Object oldValue;
	private Object newValue;

	/**
	 *  Create a TableCellListener.
	 *
	 *  @param table   the table to be monitored for data changes
	 *  @param action  the Action to invoke when cell data is changed
	 */
	public TableCellListener(JTable table, Action action)
	{
		this.table = table;
		this.action = action;
		this.table.addPropertyChangeListener( this );
	}

	/**
	 *  Create a TableCellListener with a copy of all the data relevant to
	 *  the change of data for a given cell.
	 *
	 *  @param row  the row of the changed cell
	 *  @param column  the column of the changed cell
	 *  @param oldValue  the old data of the changed cell
	 *  @param newValue  the new data of the changed cell
	 */
	private TableCellListener(JTable table, int row, int column, Object oldValue, Object newValue)
	{
		this.table = table;
		this.row = row;
		this.column = column;
		this.oldValue = oldValue;
		this.newValue = newValue;
	}

	/**
	 *  Get the column that was last edited
	 *
	 *  @return the column that was edited
	 */
	public int getColumn()
	{
		return column;
	}

	/**
	 *  Get the new value in the cell
	 *
	 *  @return the new value in the cell
	 */
	public Object getNewValue()
	{
		return newValue;
	}

	/**
	 *  Get the old value of the cell
	 *
	 *  @return the old value of the cell
	 */
	public Object getOldValue()
	{
		return oldValue;
	}

	/**
	 *  Get the row that was last edited
	 *
	 *  @return the row that was edited
	 */
	public int getRow()
	{
		return row;
	}

	/**
	 *  Get the table of the cell that was changed
	 *
	 *  @return the table of the cell that was changed
	 */
	public JTable getTable()
	{
		return table;
	}
//
//  Implement the PropertyChangeListener interface
//
	@Override
	public void propertyChange(PropertyChangeEvent e)
	{
		//  A cell has started/stopped editing

		if ("tableCellEditor".equals(e.getPropertyName()))
		{
			if (table.isEditing())
				processEditingStarted();
			else
				processEditingStopped();
		}
	}

	/*
	 *  Save information of the cell about to be edited
	 */
	private void processEditingStarted()
	{
		//  The invokeLater is necessary because the editing row and editing
		//  column of the table have not been set when the "tableCellEditor"
		//  PropertyChangeEvent is fired.
		//  This results in the "run" method being invoked

		SwingUtilities.invokeLater( this );
	}
	/*
	 *  See above.
	 */
	@Override
	public void run()
	{
		row = table.convertRowIndexToModel( table.getEditingRow() );
		column = table.convertColumnIndexToModel( table.getEditingColumn() );
		oldValue = table.getModel().getValueAt(row, column);
		newValue = null;
	}

	/*
	 *	Update the Cell history when necessary
	 */
	private void processEditingStopped()
	{
		newValue = table.getModel().getValueAt(row, column);

		//  The data has changed, invoke the supplied Action

		if (! newValue.equals(oldValue))
		{
			//  Make a copy of the data in case another cell starts editing
			//  while processing this change

			TableCellListener tcl = new TableCellListener(
				getTable(), getRow(), getColumn(), getOldValue(), getNewValue());

			ActionEvent event = new ActionEvent(
				tcl,
				ActionEvent.ACTION_PERFORMED,
				"");
			action.actionPerformed(event);
		}
	}
}