Majority.java

package ch.usi.da.paxos.old;
/* 
 * Copyright (c) 2013 Università della Svizzera italiana (USI)
 * 
 * This file is part of URingPaxos.
 *
 * URingPaxos is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * URingPaxos 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with URingPaxos.  If not, see <http://www.gnu.org/licenses/>.
 */

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.atomic.AtomicInteger;

import ch.usi.da.paxos.message.Message;
import ch.usi.da.paxos.storage.Decision;

/**
 * Name: Majority<br>
 * Description: <br>
 * 
 * Creation date: Apr 3, 2012<br>
 * $Id$
 * 
 * @author Samuel Benz benz@geoid.ch
 */
public class Majority {

	private final List<Message> messages = new ArrayList<Message>();
	
	private final Map<Decision,AtomicInteger> values = new HashMap<Decision,AtomicInteger>();
	
	private Decision decision = null;
	
	private int max_ballot = 0;
	
	/**
	 * Empty constructor
	 */
	public Majority(){
	}
	
	/**
	 * Add a message to decide
	 * 
	 * @param m
	 */
	public synchronized void addMessage(Message m){
		messages.add(m);
		if(m.getValue() != null){
			Decision d = new Decision(0,m.getInstance(),m.getBallot(),m.getValue());
			if(!values.containsKey(d)){
				values.put(d,new AtomicInteger(1));
				max_ballot = m.getBallot();
			}else{
				// store highest ballot
				if(m.getBallot() > max_ballot){
					max_ballot = m.getBallot();
					AtomicInteger i = values.get(d);
					i.incrementAndGet();
					values.put(d,i);
				}else{
					values.get(d).incrementAndGet();
				}
			}
			// majority of same value
			for(Entry<Decision,AtomicInteger> entry : values.entrySet()){
				if(entry.getValue().get() >= Configuration.getQuorum()){
					decision = entry.getKey();
					break;
				}
			}
		}
	}
	
	/**
	 * Is quorum
	 * 
	 * @return true if quorum
	 */
	public synchronized boolean isQuorum(){
		if(values.isEmpty()){
			return (messages.size() >= Configuration.getQuorum());
		}else{
			if(decision == null){
				return false;
			}else{
				return true;
			}
		}
	}
	
	/**
	 * Get the value within the majority of the messages
	 * 
	 * @return the majority value or null if not decided
	 */
	public synchronized Decision getMajorityDecision(){
		return decision;
	}
}