/*
 This file is part of the software framework JStatCom, 
 a library for building applications for data based analysis.

 Copyright (C) 2000-2005  Markus Kraetzig

 This library is free software; you can redistribute it and/or modify
 it under the terms of the GNU Lesser General Public License as
 published by the Free Software Foundation; either version 2.1 of the
 License, or (at your option) any later version.

 This library 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
 Lesser General Public License for more details.

 You should have received a copy of the GNU Lesser General Public
 License along with this library; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 USA
 */

package com.jstatcom.model;
/**
 * Events of this type are fired by JSCData objects to
 * notify listeners like JSCSymbol objects about changes of
 * various kinds. Instances of this class are constructed via the
 * static valueOf factory methods. 
 * 

 * Usage Note:

 * The events that are fired by the JSCData objects are intended
 * for internal communication only. Events do not occur in the EventDispatchingThread.
 * Clients should rather listen to changes in JSCSymbol objects, especially
 * if GUI related actions are performed.
 *
 * @author Markus Kraetzig
 */
public class JSCDataEvent {
	private final JSCData source;
	private final JSCDataEventTypes type;
	private final Object newValue;
	private final Object oldValue;

	/**
	 * JSCDataEvent constructor.
	 */
	private JSCDataEvent(
		JSCData source,
		JSCDataEventTypes type,
		boolean newVal) {
		this(source, type, new Boolean(!newVal), new Boolean(newVal));

	}

	/**
	 * Creates a JSCDataEvent.
	 *
	 * @param source   the source data object
	 * @param type     the type of this event
	 * @param oldValue the value before the change
	 * @param newValue the value after the change
	 */
	public JSCDataEvent(
		JSCData source,
		JSCDataEventTypes type,
		Object oldValue,
		Object newValue) {
		super();

		this.source = source;
		this.type = type;
		this.oldValue = oldValue;
		this.newValue = newValue;
	}

	/**
	 * Gets the value after the change.
	 * 
	 * @return an arbitrary object 
	 */
	public final Object getNewValue() {
		return newValue;
	}

	/**
	 * Gets the value before the change.
	 * 
	 * @return an arbitrary object 
	 */
	public final Object getOldValue() {
		return oldValue;
	}

	/**
	 * Gets the data object where the event was fired from.
	 * 
	 * @return a JSCData object 
	 */
	public final JSCData getSource() {
		return source;
	}

	/**
	 * Gets the type of this event.
	 * 
	 * @return one of  JSCDataEventTypes 
	 */
	public final JSCDataEventTypes getType() {
		return type;
	}

	/**
	 * Gets a string representation of this.
	 * 
	 * @return informative string representation
	 */
	public String toString() {
		return super.toString()
			+ " [source:name="
			+ source.name()
			+ ",type="
			+ source.type()
			+ ";evttype="
			+ type
			+ "]";
	}

	/**
	 * Gets an instance of this for events of type JSCDataEventTypes.VALUE_CHANGED.
	 *
	 * @param source the source from which the event is fired
	 * @param oldValue the value before the change
	 * @param newValue the value after the change
	 *
	 * @return a changed event
	 */
	public static JSCDataEvent valueOfChanged(
		JSCData source,
		Object oldValue,
		Object newValue) {

		return new JSCDataEvent(
			source,
			JSCDataEventTypes.VALUE_CHANGED,
			oldValue,
			newValue);
	}

	/**
	 * Gets an instance of this for events of type JSCDataEventTypes.EMPTY_STATE.
	 *
	 * @param source the source from which the event is fired
	 * @param isEmptyNow true if source is empty
	 * @return a cleared event
	 */
	public static JSCDataEvent valueOfEmptyState(
		JSCData source,
		boolean isEmptyNow) {

		return new JSCDataEvent(
			source,
			JSCDataEventTypes.EMPTY_STATE,
			isEmptyNow);
	}
	/**
	 * Gets the value after the change as a boolean.
	 * 
	 * @return true if new value is a Boolean that is true,
	 * 			false otherwise
	 */
	public final boolean isSourceEmpty() {

		if (newValue instanceof Boolean)
			return ((Boolean) newValue).booleanValue();

		if (newValue == null)
			return false;

		// called last to avoid synchronization overhead if possible
		return source.isEmpty();
	}
}