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Jadex Rules is a small lightweight rule engine, which currently employs the well-known Rete algorithm for highly efficient rule matching. Jadex rules is therefore similar to other rule engines like JESS and Drools. Despite the similarities there are also important differences between these systems: * Jadex Rules is very small and intended to be used as component of other software. Even though rules can be specified in a Java dialect as well as (a small variation of) the CLIPS language its primary usage is on the API level. Jadex Rules is currently the core component of the Jadex BDI reasoning engine. * Jadex Rules cleanly separates between state and rule representation. This allows the state implementation as well as the matcher to be flexibly exchanged. Some experiments have e.g. been conducted with a Jena representation. Regarding the matcher, it is planned to support also the Treat algorithm, which has a lower memory footprint than Rete. * Jadex Rules pays close attention to rule debugging. The state as well as the rete engine can be observed at runtime. The rule debugger provides functionalities to execute a rule program stepwise and also use rule breakpoints to stop the execution at those points.

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package jadex.rules.rulesystem;

import java.util.Collection;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Map;
import java.util.TreeSet;

/**
 *  An agenda that sorts activations according to their priority.
 */
public class PriorityAgenda extends AbstractAgenda
{
	//-------- attributes --------
	
	/** The activations. */
	protected TreeSet activations;
	
	/** The next activation (selected by strategy or manually form outside for debugging). */
	protected Activation next;
	
	/** The map containing the activation order count (for FIFO in case two activations are equal). */
	protected Map counts;
	
	/** The current count. */
	protected long count;
	
	//-------- constructors --------
	
	/**
	 *  Create a new agenda.
	 */
	public PriorityAgenda()
	{
		this.counts = new HashMap();
		
		this.activations = new TreeSet(new Comparator()
		{
			public int compare(Object arg0, Object arg1)
			{
				Activation act0 = (Activation)arg0;
				Activation act1 = (Activation)arg1;
				
//				if(act0==null || act1==null)
//					System.out.println("test");
				
				int ret = act0.getPriority()-act1.getPriority();
				if(ret==0)
				{
					Long tmp0 = (Long)counts.get(act0);
					Long tmp1 = (Long)counts.get(act1);
					long cnt0 = tmp0==null? 0: tmp0.longValue();
					long cnt1 = tmp1==null? 0: tmp1.longValue();
					
					// FIFO
					ret = (int)(cnt1-cnt0);
				}
				
				return ret;
			}
		});
	}
	
//	long	total	= 0;
//	long	last	= 0;
//	long	lasttime	= 0;
	
	/**
	 *  Add a new activation.
	 *  @param act The activation.
	 */
	public void addActivation(Activation act)
	{
//		total	-= System.nanoTime();
//		System.out.println("Add: "+act);
		this.counts.put(act, new Long(count++));
		this.activations.add(act);
		
		state++;
		notifyListeners();

//		total	+= System.nanoTime();
//		long	currenttime	 = System.currentTimeMillis();
//		if(currenttime>lasttime+1000)
//		{
//			if(lasttime!=0)
//				System.out.println("Total agenda time: "+((int)(total/1000000.0))+" ms, "+((int)((total-last)/1000.0)/(currenttime-lasttime))/10.0+"% in last step.");
//			last	= total;
//			lasttime	= currenttime;
//		}		
	}
	
	/**
	 *  Remove an activation
	 *  @param act The activation.
	 */
	public void removeActivation(Activation act)
	{
//		total	-= System.nanoTime();
//		System.out.println("Remove: "+act);
		
		this.activations.remove(act);
		this.counts.remove(act);
		
		if(next==act)
			next = null;
		
//		state++;
		notifyListeners();

//		total	+= System.nanoTime();
//		long	currenttime	 = System.currentTimeMillis();
//		if(currenttime>lasttime+1000)
//		{
//			if(lasttime!=0)
//				System.out.println("Total agenda time: "+((int)(total/1000000.0))+" ms, "+((int)((total-last)/1000.0)/(currenttime-lasttime))/10.0+"% in last step.");
//			lasttime	= currenttime;
//			last	= total;
//		}		
	}
	
	/**
	 *  Get the current activations.
	 *  @return The activations.
	 */
	public Collection getActivations()
	{
		return activations;
	}
	
	/**
	 *  Test if the agenda is empty.
	 *  @return True if is empty.
	 */
	public boolean isEmpty()
	{
		return activations.isEmpty();
	}
	
	/**
	 *  Get the next activation.
	 *  @return The next activation.
	 */ 
	public Activation getNextActivation()
	{
		Activation ret	= next;
		if(ret==null && activations.size()>0)
		{
			ret	= (Activation)activations.last();
		}
		
		assert next==null || activations.contains(next);
		
		return ret;
	}

	/**
	 *  Set the next activation.
	 */ 
	public void setNextActivation(Activation next)
	{
//		System.out.println("Set next: "+next);
		
		if(activations.contains(next))
		{
			this.next	= next;
		}
		else
		{
			throw new RuntimeException("Activation not in agenda: "+next+", "+this);
		}
		notifyListeners();
	}
}