Decider.java

import org.jgrapht.DirectedGraph;
import org.jgrapht.graph.DefaultDirectedGraph;
import org.jgrapht.graph.DefaultEdge;

/**
 * This class uses a graph and the gestures given in the GestureType Enumeration
 * to decide which gesture beats another one.
 * 
 * 
 */
public class Decider {
	public enum Result {
		WIN, DRAW, LOSS
	}
	
	/**
	 * The relations between gestures will be stored in a directed graph like
	 * the Paper-Scissors-Rock chart on this page:
	 * http://en.wikipedia.org/wiki/Rock-paper-scissors
	 */
	DirectedGraph<GestureType, DefaultEdge> graph;

	/**
	 * Decides which gesture wins
	 * 
	 * @param t1
	 *            The first given Gesture
	 * @param t2
	 *            The first given Gesture
	 * @return Result.WIN if t1 is winning against t2, Result.LOSS if t1 looses
	 *         against t2, Result.WIN if t2 is GestureType.NONE, Result.LOSS if
	 *         t1 is GestureType.NONE, Result.DRAW otherwise
	 * 
	 */
	public Result decideWinner(GestureType t1, GestureType t2) {
		// The result of equal gestures is a DRAW
		if (t1 == t2)
			return Result.DRAW;

		// Handle empty (NONE) Gestures
		if (t2 == GestureType.NONE)
			return Result.WIN;
		if (t1 == GestureType.NONE)
			return Result.LOSS;

		// If an Edge is directed from Gesture1 to Gesture2, it means that
		// Gesture1 beats Gesture2. Return WIN in this case, LOSS otherwise.
		if (this.graph.containsEdge(t1, t2)) {
			return Result.WIN;
		}
		return Result.LOSS;
	}

	/**
	 * Constructor for the class. This method will create the graph.
	 */
	public Decider() {
		this.graph = new DefaultDirectedGraph<GestureType, DefaultEdge>(
				DefaultEdge.class);

		// add the Gestures as Nodes/Vertices
		this.graph.addVertex(GestureType.ROCK);
		this.graph.addVertex(GestureType.PAPER);
		this.graph.addVertex(GestureType.SCISSORS);
		this.graph.addVertex(GestureType.LIZARD);
		this.graph.addVertex(GestureType.SPOCK);

		// Scissor beats paper/lizard
		this.graph.addEdge(GestureType.SCISSORS, GestureType.PAPER);
		this.graph.addEdge(GestureType.SCISSORS, GestureType.LIZARD);
		// Paper beats Rock/Spock
		this.graph.addEdge(GestureType.PAPER, GestureType.ROCK);
		this.graph.addEdge(GestureType.PAPER, GestureType.SPOCK);
		// Rock beats Scissors/Lizard
		this.graph.addEdge(GestureType.ROCK, GestureType.SCISSORS);
		this.graph.addEdge(GestureType.ROCK, GestureType.LIZARD);
		// Lizard beats paper/Spock
		this.graph.addEdge(GestureType.LIZARD, GestureType.PAPER);
		this.graph.addEdge(GestureType.LIZARD, GestureType.SPOCK);
		// Spock beats scissors/rock
		this.graph.addEdge(GestureType.SPOCK, GestureType.SCISSORS);
		this.graph.addEdge(GestureType.SPOCK, GestureType.ROCK);
	}
}