package ch.werner_randelshofer.gui.event;

/*
Copyright (C) 1999 Werner Randelshofer
werner.randelshofer@mythen.ch
http://www.mythen.ch/w.randelshofer/
    
Permission to use this release of EventListenerList is hereby
granted without fee provided that the complete copyright
notice and this permission notice appear in all copies
and in supporting documentation.
*/

import java.io.*;
import java.util.*;

/**
EventListenerList from javax.swing.event.EventListenerList.

@author	Werner Randelshofer, Staldenmattweg 2, CH-6405 Immensee, Switzerland.
@version	1.0	20.02.1999	Copied from JDK 1.2.
*/
public class EventListenerList
	{
	/* A null array to be shared by all empty listener lists*/
	private final static Object[] NULL_ARRAY = new Object[0];
	/* The list of ListenerType - Listener pairs */
	protected Object[] listenerList = NULL_ARRAY;

	/**
	 * This passes back the event listener list as an array
	 * of ListenerType - listener pairs.  Note that for 
	 * performance reasons, this implementation passes back 
	 * the actual data structure in which the listner data
	 * is stored internally!  
	 * This method is guaranteed to pass back a non-null
	 * array, so that no null-checking is required in 
	 * fire methods.  A zero-length array of Object should
	 * be returned if there are currently no listeners.
	 * 
	 * WARNING!!! Absolutely NO modification of
	 * the data contained in this array should be made -- if
	 * any such manipulation is necessary, it should be done
	 * on a copy of the array returned rather than the array 
	 * itself.
	 */
	public Object[] getListenerList()
		{ return listenerList; }

	/**
	 * Return the total number of listeners for this listenerlist
	 */
	public int getListenerCount()
		{ return listenerList.length/2; }

	/**
	 * Return the total number of listeners of the supplied type 
	 * for this listenerlist.
	 */
	public int getListenerCount(Class t)
		{
		int count = 0;
		Object[] lList = listenerList;
		for (int i = 0; i < lList.length; i+=2)
			{
			if (t == (Class)lList[i])
				count++;
			}
		return count;
		}
	/**
	 * Add the listener as a listener of the specified type.
	 * @param t the type of the listener to be added
	 * @param l the listener to be added
	 */
	public synchronized void add(Class t, EventListener l)
		{
		if (!t.isInstance(l))
			{
			throw new IllegalArgumentException("Listener " + l +
				" is not of type " + t);
			}
		if (l ==null)
			{
			throw new IllegalArgumentException("Listener " + l +
				" is null");
			}
		if (listenerList == NULL_ARRAY)
			{
			// if this is the first listener added, 
			// initialize the lists
			listenerList = new Object[] { t, l };
			}
		else
			{
			// Otherwise copy the array and add the new listener
			int i = listenerList.length;
			Object[] tmp = new Object[i+2];
			System.arraycopy(listenerList, 0, tmp, 0, i);

			tmp[i] = t;
			tmp[i+1] = l;

			listenerList = tmp;
			}
		}

	/**
	 * Remove the listener as a listener of the specified type.
	 * @param t the type of the listener to be removed
	 * @param l the listener to be removed
	 */
	public synchronized void remove(Class t, EventListener l)
		{
		if (!t.isInstance(l))
			{
			throw new IllegalArgumentException("Listener " + l +
				" is not of type " + t);
			}
		if (l ==null)
			{
			throw new IllegalArgumentException("Listener " + l +
				" is null");
			}

		// Is l on the list?
		int index = -1;
		for (int i = listenerList.length-2; i>=0; i-=2)
			{
			if ((listenerList[i]==t) && (listenerList[i+1].equals(l) == true))
				{
				index = i;
				break;
				}
			}
	
		// If so,  remove it
		if (index != -1)
			{
			Object[] tmp = new Object[listenerList.length-2];
			// Copy the list up to index
			System.arraycopy(listenerList, 0, tmp, 0, index);
			// Copy from two past the index, up to
			// the end of tmp (which is two elements
			// shorter than the old list)
			if (index < tmp.length)
				System.arraycopy(listenerList, index+2, tmp, index, 
					tmp.length - index);
			// set the listener array to the new array or null
			listenerList = (tmp.length == 0) ? NULL_ARRAY : tmp;
			}
		}
	}