package org.jivesoftware.smackx.jingle;

import org.jivesoftware.smack.packet.IQ;
import org.jivesoftware.smackx.packet.Jingle;

/**
 * Implement the Jingle Session state using the State Behavioral pattern. (From
 * the book Design Patterns, AKA GoF.) These classes also employ the Flyweight
 * and Singleton patterns as recommended for the State pattern by GoF.
 * 
 * There seems to be three ways to go with the State pattern in Java: interface,
 * abstract class and enums. Most of the accepted models use abstract classes.
 * It wasn't clear to me that any of the three models was superior, so I went
 * with the most common example.
 * 
 * @author Jeff Williams
 */
public abstract class JingleSessionState {

	/**
	 * Called when entering the state.
	 */
	public static JingleSessionState getInstance() {
		// Since we can never instantiate this class there is nothing to return
		// (ever).
		return null;
	}

	/**
	 * Called when entering the state.
	 */
	public abstract void enter();

	/**
	 * Called when exiting the state.
	 */
	public abstract void exit();

	/**
	 * Process an incoming Jingle Packet. When you look at the GoF State pattern
	 * this method roughly corresponds to example on p310: ProcessOctect().
	 */
	public abstract IQ processJingle(JingleSession session, Jingle jingle,
			JingleActionEnum action);

	/**
	 * For debugging just emit the short name of the class.
	 */
	@Override
	public String toString() {
		return this.getClass().getSimpleName();
	}
}