@Override
protected List<Move> _generateMoves() {
// Collect some information to shorten the code later.
final List<Move> result = new ArrayList<>();
final ChessCoord currentCoord = this.getCoord();
final int currentFile = currentCoord.getFile();
final int currentRank = currentCoord.getRank();
final int singleStepTargetRank = currentRank + rankStep;
final boolean isPromoting = singleStepTargetRank == this.promotionRank;
// First check for the normal forward moves
ChessCoord tarCoord = Coords.coord(currentFile, singleStepTargetRank);
// Single step
if (this.getPos().getPieceAt(tarCoord) == null) {
if (isPromoting) {
this.addPromotionMoves(result, tarCoord);
} else {
result.add(new SimpleMove(currentCoord, tarCoord));
}
}
// Double step
if (currentRank == this.startRank) {
tarCoord = Coords.coord(currentFile, currentRank + FIRST_MOVE_FACTOR * rankStep);
if (this.getPos().getPieceAt(tarCoord) == null) {
// We don't bother about checking for being promoted because
// that would mean that the pawn has a one-move promotion, which
// really does not make any sense. This would break this code
// though.
result.add(new SimpleMove(currentCoord, tarCoord));
}
}
// Now deal with taking moves
// Lower file (left)
addPossibleTakingMove(result, currentFile - 1, isPromoting);
// Higher file (right)
addPossibleTakingMove(result, currentFile + 1, isPromoting);
return result;
}
/**
* Private helper method to deal with taking moves to the right and left to the pawn.
*
* <p>This adds the possible move(s) to the passed list in case the passed file valid. Adds
* nothing if the passed file outside the board.
*
* @param moveList The {@code List list} the moves are added to.
* @param targetFile The target file index.
* @param isPromoting Flag stating whether we are promoting at the moment. This could be
* calculated by the method itself but was calculated in the calling context.
*/
private void addPossibleTakingMove(
final List<Move> moveList, final int targetFile, final boolean isPromoting) {
if (ChessRules.fileWithinBounds(targetFile)) {
final ChessCoord tarCoord =
Coords.coord(targetFile, this.getCoord().getRank() + this.rankStep);
final Piece targetCoordPiece = this.getPos().getPieceAt(tarCoord);
// Check whether there is an opposing piece at the target
// coordinate.
if (targetCoordPiece != null && (!this.getColor().equals(targetCoordPiece.getColor()))) {
if (isPromoting) {
addPromotionMoves(moveList, tarCoord);
} else {
moveList.add(new SimpleTakingMove(this.getCoord(), tarCoord));
}
}
// Also check for en passant moves.
else if (this.getCoord().getRank() == this.enPassantRank
&& this.getPos().getEnpassantFile() == targetFile) {
moveList.add(new EnPassantMove(this.getCoord(), tarCoord));
}
}
}