public ErrorCondition Move(AnnotatedMove move) => Move(move.Move);
// Parses a move, but does not determine validity
public static bool TryParseMove(string input, BoardState state, ulong piecesOnCurrentSide, out AnnotatedMove result)
{
// ✔ Account for castling (O-O, O-O-O)
// ✔ Account for regular move (a4, Ng8)
// ✔ Account for long-form move (Nb1 c3, Nb1-c3)
// ✔ Account for long-form capture (Ne2xa4)
// ✔ Account for short-form capture (Nxg4, axb4)
// ✔ Account for disambiguation (Ngg4)
// ✔ Account for piece promotions (e8=Q)
// ✔ Account for promoted piece must be own colour
// ✔ Account for if pawn moves to end without specifying promotion
// ✔ Account for if non-pawn specifies promotion
// ✔ Account for if promotion piece tries to become pawn
// ✔ Account for if specify promotion when not at end
// ✔ Account for state change marks (Na4+, e2#)
// ✔ Account for annotations (Na4!, e2??, b5!?)
// ✔ Account for whitespace (Ne2 x a4) - fail in this case
// ✔ Account for invalid ranks/files - fail in this case
var trimmedInput = input.AsSpan().Trim();
if (trimmedInput.IsEmpty || trimmedInput.IndexOf(' ') != -1)
{
result = AnnotatedMove.Empty;
return(false);
}
var isWhiteMove = piecesOnCurrentSide == state.WhitePieces;
var moveNotation = TrimMoveDescriptors(trimmedInput);
if (moveNotation.IsEmpty)
{
result = AnnotatedMove.Empty;
return(false);
}
var moveDescriptors = moveNotation.Length == trimmedInput.Length
? ReadOnlySpan <char> .Empty
: trimmedInput.Slice(moveNotation.Length);
var promotion = GetPromotion(moveDescriptors, isWhiteMove);
if (promotion != SquareContents.Empty)
{
moveDescriptors = moveDescriptors.Length > 2 ? moveDescriptors.Slice(2) : ReadOnlySpan <char> .Empty;
}
var annotation = GetAnnotation(moveDescriptors);
var attackState = GetAttackState(moveDescriptors);
// Handle castling
if (TryHandleCastling(moveNotation, isWhiteMove, out var move))
{
result = new AnnotatedMove(move, annotation, attackState);
return(true);
}
// Read leading piece designation
char pieceDesignation;
if (PieceDesignations.Contains(moveNotation[0]))
{
pieceDesignation = moveNotation[0];
moveNotation = moveNotation.Slice(1);
}
else
{
pieceDesignation = Constants.PieceNotation.Pawn;
}
int squareIdx = moveNotation.Length - 1;
// Get end square (must be present)
var parsedState = new ParsedMoveState();
parsedState.EndRank = moveNotation[squareIdx--] - '0';
parsedState.EndFile = Char.ToLower(moveNotation[squareIdx--]);
var lastRankForColor = isWhiteMove ? Constants.Board.NumberOfRows : 1;
if (promotion != 0)
{
if (
pieceDesignation != Constants.PieceNotation.Pawn || // promoted non-pawn
(promotion & SquareContents.Pawn) != 0 || // promoted to invalid piece (pawn)
parsedState.EndRank != lastRankForColor // promoted but not at end
)
{
result = AnnotatedMove.Empty;
return(false);
}
parsedState.PromotedPiece = promotion;
}
else if (pieceDesignation == Constants.PieceNotation.Pawn && parsedState.EndRank == lastRankForColor)
{
// Moved pawn to end without promoting
result = AnnotatedMove.Empty;
return(false);
}
// Ignore delimiter (if present)
bool isCapture = false;
if (squareIdx >= 0 && SquareDelimiters.Contains(moveNotation[squareIdx]))
{
isCapture = moveNotation[squareIdx] == Constants.MoveType.Capture;
squareIdx--;
}
// Read start squares (if present)
if (squareIdx >= 0 && Char.IsDigit(moveNotation[squareIdx]))
{
parsedState.StartRank = moveNotation[squareIdx--] - '0';
}
if (squareIdx >= 0 && Char.IsLetter(moveNotation[squareIdx]))
{
parsedState.StartFile = Char.ToLower(moveNotation[squareIdx--]);
}
if (parsedState.StartRank != 0 && parsedState.StartFile != 0)
{
var valid = IsMoveValid(parsedState);
result = valid ? new AnnotatedMove(parsedState.ToMove(), annotation, attackState) : AnnotatedMove.Empty;
return(valid);
}
if (TryInferStartSquare(state, piecesOnCurrentSide, isWhiteMove, isCapture, pieceDesignation, ref parsedState))
{
var valid = IsMoveValid(parsedState);
result = valid ? new AnnotatedMove(parsedState.ToMove(), annotation, attackState) : AnnotatedMove.Empty;
return(valid);
}
result = AnnotatedMove.Empty;
return(false);
}
public static bool Equals(AnnotatedMove a, AnnotatedMove b)
{
return(a.Annotation == b.Annotation &&
a.AttackState == b.AttackState &&
a == b);
}