source: src/main/java/bargainingchips/protocol/BilateralProtocol.java@ 341

package bargainingchips.protocol;

import java.util.List;

import java.util.ArrayList;
import java.util.concurrent.BlockingQueue;

import bargainingchips.actions.Offer;
import bargainingchips.actions.OfferBy;

/**
 * A (possibly asynchronous) protocol between two agents A 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 final BlockingQueue<OfferBy> from;
        
        // Should be considered final
        protected String nameA;
        protected BlockingQueue<Offer> toA;
        protected String nameB;
        protected BlockingQueue<Offer> toB;
                
        protected final List<OfferBy> log;
        
        public BilateralProtocol(BlockingQueue<OfferBy> from, String nameA,
                        BlockingQueue<Offer> toA, String nameB, BlockingQueue<Offer> toB) {
                super();
                this.from = from;
                this.nameA = nameA;
                this.toA = toA;
                this.nameB = nameB;
                this.toB = toB;
                this.log = new ArrayList<OfferBy>();
        }

        protected abstract ValidationResult validate(OfferBy o);
        
        @Override
        public void run() 
        {
                // Wait for a message from A or B
                try {
                        while (true)
                        {
                                // Wait for a message, avoiding busy wait
                                OfferBy ob = from.take();
                                
                                if (ob != null)
                                {
                                        String sender = ob.getSender();
                                        Offer o = ob.getOffer();
                                        ValidationResult validationResult = validate(ob);
                                        
                                        if (validationResult.isValid())                                         // if the offer was valid
                                        {
                                                log(ob);                                                                                // make it official
                                                BlockingQueue<Offer> to = addressee(sender);    // put it in the right outbox by looking up sender among nameA and nameB
                                                to.put(o);
                                        }
                                        else // drop!
                                                System.err.println("Warning: " + ob + " was not a valid offer and was dropped. Log: " + log.toString());
                                        
                                        // The validation could result in a state where the negotiation ended. 
                                        // We have an outcome, we let both agents know and clean up
                                        if (validationResult.hasEnded())
                                        {
                                                Offer finalOutcome = validationResult.getOutcome();
                                                toA.put(finalOutcome);
                                                toB.put(finalOutcome);
                                                System.out.println("Protocol detected final outcome: " + finalOutcome + 
                                                                ". Notified agents and quitting.");
                                                return;
                                        }
                                }
                        }
                } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                }
        }
        
        /**
         * Gives the correct outbox for the sender
         */
        private BlockingQueue<Offer> addressee(String sender) 
        {
                if (nameA.equals(sender))
                        return toB;
                
                if (nameB.equals(sender))
                        return toA;
                
                throw new IllegalStateException("Sender " + sender + " unknown! Should be either " + nameA + " or " + nameB);
        }

        private void log(OfferBy ob) 
        {
                log.add(ob);
                System.out.println("Logged: " + ob);
        }
        
        protected OfferBy getLastOffer()
        {
                return log.get(log.size() - 1);
        }       

}