private int getScoreForEndPosition(Player player) {
int returnValue = -1;
if (player.isInStaleMate() || itsBoard.isThirdOccuranceOfPosition()) returnValue = 500;
else if (player.isInCheckMate()) {
if (player == itsPlayer) returnValue = 0;
else returnValue = 1000;
}
return returnValue;
}
public void search(ChessBoard board, Player player) {
itsTable = new PositionHashTable();
itsMoves.clear();
itsPlayer = player;
itsBoard = board;
Collection moves = getAllMoves(player);
for (Iterator i = moves.iterator(); i.hasNext(); ) {
AbstractMove move = (AbstractMove) i.next();
move.getPiece().findMoves_safe();
move = player.movePiece(move);
itsBoard.recordPosition();
String positionCode = itsBoard.getPositionCode() + player.getColor();
int score = examineMove(move, player, itsSearchQuality, positionCode);
move.setScore(score);
itsMoves.add(move);
itsBoard.removeLastPosition();
player.reverseMove(move);
}
}
private Collection getAllMoves(Player player) {
Collection moves = new HashSet();
for (Iterator p = player.getPieces().iterator(); p.hasNext(); ) {
Piece piece = (Piece) p.next();
SquareInterface startSquare = piece.getLocation();
for (Iterator s = piece.getMoveOptions().iterator(); s.hasNext(); ) {
SquareInterface square = (SquareInterface) s.next();
moves.add(new Move(piece, startSquare, square));
}
}
return moves;
}
private int examineMove(AbstractMove theMove, Player player, int depth, String position) {
Player player2 = player.getOpponent();
player2.findAllMoves(theMove.isCheck());
int endPositionScore = getScoreForEndPosition(player2);
if (endPositionScore != -1) {
itsTable.add(position, endPositionScore);
return endPositionScore;
} else if (depth == 1) {
int score = itsScorer.getScore(itsBoard, itsPlayer);
itsTable.add(position, score);
return score;
} else {
int bestScore = 1234;
Collection moves = getAllMoves(player2);
for (Iterator i = moves.iterator(); i.hasNext(); ) {
AbstractMove move = (AbstractMove) i.next();
move.getPiece().findMoves_safe();
move = player2.movePiece(move);
String newPosition = itsBoard.getPositionCode() + player2.getColor();
int thisScore = -321;
boolean hasIt = itsTable.has(newPosition);
if (hasIt) {
thisScore = itsTable.getScore();
} else {
thisScore = examineMove(move, player2, depth - 1, newPosition);
itsTable.add(newPosition, thisScore);
}
bestScore = compareScores(player2, bestScore, thisScore);
player2.reverseMove(move);
}
return bestScore;
}
}