package protocol;

import java.util.List;

import java.util.concurrent.BlockingQueue;

import onetomany.bargainingchipsgame.interactions.Offer;
import onetomany.bargainingchipsgame.interactions.OfferBy;

/**
 * A (possibly asynchronous) protocol between two agents An and B.
 * The protocol acts as the postman of delivering messages between the agents and validates their messages.
 * The protocol keeps the one official (synchronized) log of what has happened.
 */
public abstract class BilateralProtocol implements Runnable
{
	// Messaging to and from A and B
	protected BlockingQueue<Offer> fromA;
	protected BlockingQueue<Offer> toA;
	protected BlockingQueue<Offer> fromB;
	protected BlockingQueue<Offer> toB;
	
	protected List<OfferBy> log;
	
	protected abstract boolean validate(Offer o);
	
	@Override
	public void run() 
	{
		String sender = "A";
		
		// Wait for a message from A or B
		try {
			while (true)
			{
				BlockingQueue<Offer> from = from(sender);	// starts with A
				BlockingQueue<Offer> to   = to(sender);		// starts with B
				
				Offer o = from.poll();
				if (o != null)
				{
					if (validate(o))
					{
						log(sender, o);
						to.put(o);
					}
					// else drop!						
				}

				// Swap the queue to check: A <-> B
				sender = swapRole(sender, "A", "B");
			}
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

	private String swapRole(String x, String y, String z) 
	{
		return x.equals(y) ? z : y;
	}
	
	private BlockingQueue<Offer> from(String sender) 
	{
		return "A".equals(sender) ? fromA : fromB;
	}
	
	private BlockingQueue<Offer> to(String sender) 
	{
		return "A".equals(sender) ? toB : toA;
	}

	private void log(String id, Offer o) 
	{
		log.add(new OfferBy(id, o));
	}
	
	protected Offer getLastOffer()
	{
		return log.get(log.size() - 1);
	}

}