- Reorganized packages so that the computer agents are inside the model package.

- Added support for the player model inside Referee.java; high scores should now persist over a single execution of the program.
- Refactored PlayerModel.java to support game logging. All games are now logged so that we can track overall progress.
- Added scaffolding to allow saving and importing of PlayerModel.java. It is not yet functional, but it will be with two function implementations and then the appropriate calls.

src/model/comPlayer/generator/AlphaBetaMoveGenerator.java

@@ -0,0 +1,126 @@
+package model.comPlayer.generator;
+
+import java.util.Arrays;
+import java.util.List;
+
+import model.Board;
+import model.BoardScorer;
+import model.Move;
+import model.SearchResult;
+
+import org.apache.log4j.Logger;
+
+public class AlphaBetaMoveGenerator implements MoveGenerator {
+	private static final Logger LOGGER = Logger
+			.getLogger(AlphaBetaMoveGenerator.class.getName());
+	private static final int DEFAULT_RECURSIVE_PLAYS = 2;
+
+	private final BoardScorer scorer = new BoardScorer();
+	private final ValidMoveGenerator validMoveGenerator = new ValidMoveGenerator();
+
+	@Override
+	public Move genMove(Board board, boolean asHuman) {
+				
+		if (!asHuman) {
+			return getMaxValue(board, asHuman, DEFAULT_RECURSIVE_PLAYS * 2, Integer.MIN_VALUE,
+					Integer.MAX_VALUE).move;
+		} else {
+			return getMinValue(board, asHuman, DEFAULT_RECURSIVE_PLAYS * 2, Integer.MIN_VALUE,
+					Integer.MAX_VALUE).move;
+		}
+	}
+
+	private SearchResult getMax(SearchResult sr1, SearchResult sr2) {
+		if (sr1.score >= sr2.score) {
+			return sr1;
+		} else {
+			return sr2;
+		}
+	}
+	
+	private SearchResult getMin(SearchResult sr1, SearchResult sr2) {
+		if (sr1.score <= sr2.score) {
+			return sr1;
+		} else {
+			return sr2;
+		}
+	}
+	
+	private SearchResult  getMaxValue(Board board, boolean asHuman, int recursionLevel,
+			int alpha, int beta) {
+		if (recursionLevel < 1) {
+			return new SearchResult(Move.NONE,scorer.getScore(board));
+		}
+
+		List<Move> validMoves = validMoveGenerator.genMoves(board, asHuman,
+				MoveGenerator.ALL_MOVES);
+
+		SearchResult bestResult = new SearchResult(Move.NONE,Integer.MIN_VALUE);
+		
+		for (Move nextMove : validMoves) {
+			Board nextBoard = new Board(board);
+
+			if (!nextBoard.playTile(nextMove.getCell(), nextMove.getColor())) {
+				throw new RuntimeException(
+						"Illegal move attempted during search!");
+			}
+
+			SearchResult searchResult = new SearchResult(nextMove,getMinValue(nextBoard, !asHuman, recursionLevel - 1,
+					alpha, beta).score);
+
+			bestResult = getMax(bestResult,searchResult);
+
+			if (bestResult.score >= beta) {
+				return bestResult;
+			}
+			
+			alpha = Math.max(alpha, bestResult.score);
+		}
+
+		return bestResult;
+	}
+
+	private SearchResult getMinValue(Board board, boolean asHuman, int recursionLevel,
+			int alpha, int beta) {
+		if (recursionLevel < 1) {
+			return new SearchResult(Move.NONE,scorer.getScore(board));
+		}
+
+		List<Move> validMoves = validMoveGenerator.genMoves(board, asHuman,
+				MoveGenerator.ALL_MOVES);
+
+		SearchResult bestResult = new SearchResult(Move.NONE,Integer.MAX_VALUE);
+
+		for (Move nextMove : validMoves) {
+			Board nextBoard = new Board(board);
+
+			if (!nextBoard.playTile(nextMove.getCell(), nextMove.getColor())) {
+				throw new RuntimeException(
+						"Illegal move attempted during search!");
+			}
+
+			SearchResult searchResult = new SearchResult(nextMove,getMaxValue(nextBoard, !asHuman, recursionLevel - 1,
+					alpha, beta).score);
+
+			bestResult = getMin(bestResult,searchResult);
+
+			if (bestResult.score <= alpha) {
+				return bestResult;
+			}
+			
+			beta = Math.min(beta, bestResult.score);
+		}
+
+		return bestResult;
+	}
+
+	/**
+	 * AlphaBetaMoveGenerator2 does not support this method.
+	 */
+	@Override
+	public List<Move> genMoves(Board board, boolean asHuman, int nMoves) {
+		Move[] doNothing = new Move[] { Move.NONE };
+		LOGGER.info("Minimax genMoves() stub returning []");
+		return Arrays.asList(doNothing);
+	}
+}