private static final Position getPassiveAttacker(
BasicChessGameInterface game, Position kingPos, Position lastMovedFrom) {
final boolean straightAttack = areStraightPositions(kingPos, lastMovedFrom);
final boolean diagonalAttack = areDiagonalPositions(kingPos, lastMovedFrom);
if (!straightAttack && !diagonalAttack) {
return null;
}
final int rowStep = signum(lastMovedFrom.row - kingPos.row);
final int columnStep = signum(lastMovedFrom.column - kingPos.column);
int row = lastMovedFrom.row + rowStep;
int column = lastMovedFrom.column + columnStep;
while (row >= 0 && column >= 0 && row < 8 && column < 8) {
final Position pos = Position.get(row, column);
final Figure figure = game.getFigure(pos);
if (figure != null) {
if (figure.isReachable(kingPos, game)) {
return pos;
}
break;
}
row += rowStep;
column += columnStep;
}
return null;
}
private static CheckStatus analyseCheckAfterEnpassent(
SimpleChessBoardInterface game, boolean whiteInCheck, Move lastMove) {
final Position kingPos = game.getKingPosition(whiteInCheck);
final List<Position> attackPositions = new ArrayList<Position>(2);
final Figure attackFigure = game.getFigure(lastMove.to);
Position passiveAttacker = getPassiveAttacker(game, kingPos, lastMove.from);
if (passiveAttacker == null) {
// an attackpath may have opend over the diagonal of the removed pawn
Position removedPawnPos = Position.get(lastMove.from.row, lastMove.to.column);
passiveAttacker = getPassiveAttacker(game, kingPos, removedPawnPos);
}
if (attackFigure.isReachable(kingPos, game)) {
attackPositions.add(attackFigure.getPosition());
}
if (passiveAttacker != null) {
attackPositions.add(passiveAttacker);
}
switch (attackPositions.size()) {
case 0:
return CheckStatus.NO_CHECK;
case 1:
return getPossiblePositions(kingPos, attackPositions.get(0));
case 2:
return CheckStatus.DOUBLE_CHECK;
default:
throw new IllegalStateException(
"more than 2 attackers are impossible " + attackPositions.size());
}
}
private static boolean isCheckByKnight(
final BasicChessGameInterface game,
final Position kingPos,
final List<Position> attackerPos,
final boolean isWhite) {
final int minRow = Math.max(0, kingPos.row - 2);
final int maxRow = Math.min(7, kingPos.row + 2);
final int minColumn = Math.max(0, kingPos.column - 2);
final int maxColumn = Math.min(7, kingPos.column + 2);
for (int row = minRow; row <= maxRow; row++) {
for (int column = minColumn; column <= maxColumn; column++) {
final int vertical_dif = Math.abs(kingPos.row - row);
final int horizontal_dif = Math.abs(kingPos.column - column);
if (vertical_dif + horizontal_dif == 3) {
final Position pos = Position.get(row, column);
final Figure figure = game.getFigure(pos);
if (figure != null && figure.isWhite() != isWhite && figure.isKnight()) {
attackerPos.add(pos);
return true;
}
}
}
}
return false;
}
private static CheckStatus analyseCheckAfterPawnTransform(
SimpleChessBoardInterface game, boolean whiteInCheck, Move lastMove) {
final Position kingPos = game.getKingPosition(whiteInCheck);
final Figure transformedPawn = game.getFigure(lastMove.to);
final List<Position> attackPositions = new ArrayList<Position>(2);
final Position passiveAttacker = getPassiveAttacker(game, kingPos, lastMove.from);
if (transformedPawn.isReachable(kingPos, game)) {
attackPositions.add(lastMove.to);
}
if (passiveAttacker != null && !passiveAttacker.equalsPosition(lastMove.to)) {
attackPositions.add(passiveAttacker);
}
switch (attackPositions.size()) {
case 0:
return CheckStatus.NO_CHECK;
case 1:
return getPossiblePositions(kingPos, attackPositions.get(0));
case 2:
return CheckStatus.DOUBLE_CHECK;
default:
throw new IllegalStateException(
"more than 2 attackers are impossible " + attackPositions.size());
}
}
private static CheckStatus analyseCheckAfterRochade(
SimpleChessBoardInterface game, boolean whiteInCheck, Move lastMove) {
final Position kingPos = game.getKingPosition(whiteInCheck);
final int rock_row = lastMove.to.row;
final int rock_column = lastMove.to.column == 2 ? 3 : 5;
final Position rockPos = Position.get(rock_row, rock_column);
final Figure rock = game.getFigure(rockPos);
if (rock.isReachable(kingPos, game)) return getPossiblePositions(kingPos, rockPos);
return CheckStatus.NO_CHECK;
}
private static boolean isCheckByPawn(
final BasicChessGameInterface game,
final Position kingPos,
final List<Position> attackerPos,
final boolean isWhite) {
final int possiblePawnRow = isWhite ? kingPos.row + 1 : kingPos.row - 1;
if (possiblePawnRow < 0 || possiblePawnRow > 7) return false;
if (kingPos.column != 0) {
final Position pos = Position.get(possiblePawnRow, kingPos.column - 1);
final Figure figure = game.getFigure(pos);
if (figure != null && figure.isWhite() != isWhite && figure.isPawn()) {
attackerPos.add(pos);
return true;
}
}
if (kingPos.column != 7) {
final Position pos = Position.get(possiblePawnRow, kingPos.column + 1);
final Figure figure = game.getFigure(pos);
if (figure != null && figure.isWhite() != isWhite && figure.isPawn()) {
attackerPos.add(pos);
return true;
}
}
return false;
}
private static boolean isCheckByKing(
final BasicChessGameInterface game,
final Position kingPos,
final List<Position> attackerPos) {
final int minRow = Math.max(0, kingPos.row - 1);
final int maxRow = Math.min(7, kingPos.row + 1);
final int minColumn = Math.max(0, kingPos.column - 1);
final int maxColumn = Math.min(7, kingPos.column + 1);
for (int row = minRow; row <= maxRow; row++) {
for (int column = minColumn; column <= maxColumn; column++) {
if (row != kingPos.row || column != kingPos.column) {
final Position pos = Position.get(row, column);
final Figure figure = game.getFigure(pos);
if (figure != null && figure.isKing()) {
attackerPos.add(pos);
return true;
}
}
}
}
return false;
}
public static CheckStatus analyseCheck(
SimpleChessBoardInterface game, boolean whiteInCheck, ExtendedMove lastMove) {
if (lastMove == null) {
return analyseCheck(game, whiteInCheck);
}
if (lastMove.isEnpassent()) return analyseCheckAfterEnpassent(game, whiteInCheck, lastMove);
if (lastMove.isRochade()) return analyseCheckAfterRochade(game, whiteInCheck, lastMove);
if (lastMove.pawnTransformed())
return analyseCheckAfterPawnTransform(game, whiteInCheck, lastMove);
final Position kingPos = game.getKingPosition(whiteInCheck);
final Figure movedFigure = game.getFigure(lastMove.to);
final List<Position> attackPositions = new ArrayList<Position>(2);
if (movedFigure.isReachable(kingPos, game)) {
attackPositions.add(lastMove.to);
}
Position passiveAttacker = getPassiveAttacker(game, kingPos, lastMove.from);
if (passiveAttacker != null) {
attackPositions.add(passiveAttacker);
}
switch (attackPositions.size()) {
case 0:
return CheckStatus.NO_CHECK;
case 1:
return getPossiblePositions(kingPos, attackPositions.get(0));
case 2:
return CheckStatus.DOUBLE_CHECK;
default:
throw new IllegalStateException(
"more than 2 attackers are impossible " + attackPositions.size());
}
}
private static boolean isDoubleHorizontalCheckAfterPawnTransformation(
final BasicChessGameInterface game,
final Position kingPos,
final List<Position> attackerPos,
final boolean isWhite) {
// only possible if the king stod in the columnshadow of a pawn which transformed in the last
// move to rock or queen
final int groundRow = isWhite ? 0 : 7;
if (kingPos.row != groundRow) return false;
Position kingSideAttackerPos = null;
if (kingPos.column != 0) {
final Position leftKingPos = Position.get(groundRow, kingPos.column - 1);
final Figure leftFromKingFigure = game.getFigure(leftKingPos);
if (leftFromKingFigure != null
&& leftFromKingFigure.isWhite() != isWhite
&& (leftFromKingFigure.isQueen() || leftFromKingFigure.isRock())) {
kingSideAttackerPos = leftKingPos;
}
}
if (kingPos.column != 7 && kingSideAttackerPos == null) {
final Position rightKingPos = Position.get(groundRow, kingPos.column + 1);
final Figure rightFromKingFigure = game.getFigure(rightKingPos);
if (rightFromKingFigure != null
&& rightFromKingFigure.isWhite() != isWhite
&& (rightFromKingFigure.isQueen() || rightFromKingFigure.isRock())) {
kingSideAttackerPos = rightKingPos;
}
}
if (kingSideAttackerPos == null) return false;
final int rowStep = isWhite ? 1 : -1;
final int toRow = isWhite ? 7 : 0;
int row = groundRow;
do {
row += rowStep;
final Position pos = Position.get(row, kingPos.column);
final Figure figure = game.getFigure(pos);
if (figure == null) continue;
// either figure says 'chess' or king is not in danger
if (figure.isWhite() != isWhite && (figure.isRock() || figure.isQueen())) {
attackerPos.add(kingSideAttackerPos);
attackerPos.add(pos);
return true;
}
} while (row != toRow);
return false;
}
private static boolean isCheckByRockOrQueen(
final BasicChessGameInterface game,
final Position kingPos,
final List<Position> attackerPos,
final boolean isWhite) {
if (isDoubleHorizontalCheckAfterPawnTransformation(game, kingPos, attackerPos, isWhite))
return true;
// da die Bauerntransformation jetzt ausgeschlossen ist,
// darf nach dem Fund eines Angreifer aufgehört werden
for (int row = kingPos.row + 1; row < 8; row++) { // vertikale Reihe
final Position pos = Position.get(row, kingPos.column);
final Figure figure = game.getFigure(pos);
if (figure == null) continue;
if (figure.isWhite() == isWhite) break;
if (figure.isRock() || figure.isQueen()) {
attackerPos.add(pos);
return true;
}
break;
}
for (int row = kingPos.row - 1; row >= 0; row--) { // vertikale Reihe
final Position pos = Position.get(row, kingPos.column);
final Figure figure = game.getFigure(pos);
if (figure == null) continue;
if (figure.isWhite() == isWhite) break;
if (figure.isRock() || figure.isQueen()) {
attackerPos.add(pos);
return true;
}
break;
}
for (int column = kingPos.column + 1; column < 8; column++) { // horizontale Reihe
final Position pos = Position.get(kingPos.row, column);
final Figure figure = game.getFigure(pos);
if (figure == null) continue;
if (figure.isWhite() == isWhite) break;
if (figure.isRock() || figure.isQueen()) {
attackerPos.add(pos);
return true;
}
break;
}
for (int column = kingPos.column - 1; column >= 0; column--) { // horizontale Reihe
final Position pos = Position.get(kingPos.row, column);
final Figure figure = game.getFigure(pos);
if (figure == null) continue;
if (figure.isWhite() == isWhite) break;
if (figure.isRock() || figure.isQueen()) {
attackerPos.add(pos);
return true;
}
break;
}
return false;
}
private static boolean isCheckByBishopOrQueen(
final BasicChessGameInterface game,
final Position kingPos,
final List<Position> attackerPos,
final boolean isWhite) {
int column, row;
column = kingPos.column + 1;
row = kingPos.row + 1;
while (column < 8 && row < 8) {
final Position pos = Position.get(row, column);
row++;
column++;
final Figure figure = game.getFigure(pos);
if (figure == null) continue;
if (figure.isWhite() == isWhite) break;
if (figure.isBishop() || figure.isQueen()) {
attackerPos.add(pos);
return true;
}
break;
}
column = kingPos.column - 1;
row = kingPos.row + 1;
while (column >= 0 && row < 8) {
final Position pos = Position.get(row, column);
row++;
column--;
final Figure figure = game.getFigure(pos);
if (figure == null) continue;
if (figure.isWhite() == isWhite) break;
if (figure.isBishop() || figure.isQueen()) {
attackerPos.add(pos);
return true;
}
break;
}
column = kingPos.column + 1;
row = kingPos.row - 1;
while (column < 8 && row >= 0) {
final Position pos = Position.get(row, column);
row--;
column++;
final Figure figure = game.getFigure(pos);
if (figure == null) continue;
if (figure.isWhite() == isWhite) break;
if (figure.isBishop() || figure.isQueen()) {
attackerPos.add(pos);
return true;
}
break;
}
column = kingPos.column - 1;
row = kingPos.row - 1;
while (column >= 0 && row >= 0) {
final Position pos = Position.get(row, column);
row--;
column--;
final Figure figure = game.getFigure(pos);
if (figure == null) continue;
if (figure.isWhite() == isWhite) break;
if (figure.isBishop() || figure.isQueen()) {
attackerPos.add(pos);
return true;
}
break;
}
return false;
}