public static void GetFenSnippet([NotNull] this PiecePosition position, [NotNull] StringBuilder resultBuilder)
{
if (position is null)
{
throw new ArgumentNullException(nameof(position));
}
if (resultBuilder is null)
{
throw new ArgumentNullException(nameof(resultBuilder));
}
var emptySquareCount = new ValueContainer <int>(0);
void WriteEmptySquareCount()
{
//// ReSharper disable once InvertIf
if (emptySquareCount.Value > 0)
{
resultBuilder.Append(emptySquareCount.Value);
emptySquareCount.Value = 0;
}
}
for (var rank = ChessConstants.RankCount - 1; rank >= 0; rank--)
{
if (rank < ChessConstants.RankCount - 1)
{
resultBuilder.Append(ChessConstants.FenRankSeparator);
}
for (var file = 0; file < ChessConstants.FileCount; file++)
{
var square = new Square(file, rank);
var piece = position[square];
if (piece == Piece.None)
{
emptySquareCount.Value++;
continue;
}
WriteEmptySquareCount();
var fenChar = piece.GetFenChar();
resultBuilder.Append(fenChar);
}
WriteEmptySquareCount();
}
}
public bool IsSamePosition(StandardGamePosition other)
{
if (ReferenceEquals(this, other))
{
return(true);
}
if (other is null)
{
return(false);
}
return(ZobristKey == other.ZobristKey &&
CastlingOptions == other.CastlingOptions &&
ActiveSide == other.ActiveSide &&
EnPassantCaptureInfo == other.EnPassantCaptureInfo &&
PiecePosition.IsSamePosition(other.PiecePosition));
}
public override string ToString() => PiecePosition.GetFenSnippet();
private static bool TryCreateInternal(
[NotNull] string fen,
out string errorDetails,
out StandardGamePosition result)
{
if (fen.IsNullOrWhiteSpace())
{
errorDetails = "The FEN cannot be empty.";
result = null;
return(false);
}
var fenSnippets = fen
.Trim()
.Split(ChessConstants.FenSnippetSeparator.AsArray(), StringSplitOptions.None);
if (fenSnippets.Length != ChessConstants.FenSnippetCount)
{
errorDetails = "Invalid FEN format.";
result = null;
return(false);
}
var piecePositionFen = fenSnippets[0];
if (!PiecePosition.TryCreate(piecePositionFen, out var piecePosition))
{
errorDetails = "Invalid position of pieces.";
result = null;
return(false);
}
var activeSideSnippet = fenSnippets[1];
if (!ChessConstants.FenSnippetToGameSideMap.TryGetValue(activeSideSnippet, out var activeSide))
{
errorDetails = "Invalid active side.";
result = null;
return(false);
}
var castlingOptions = CastlingOptions.None;
var castlingOptionsSnippet = fenSnippets[2];
if (castlingOptionsSnippet != ChessConstants.NoneCastlingOptionsFenSnippet)
{
var castlingOptionsSnippetSet = OmnifactotumCollectionExtensions.ToHashSet(castlingOptionsSnippet);
foreach (var optionChar in castlingOptionsSnippetSet)
{
if (!ChessConstants.FenCharCastlingOptionMap.TryGetValue(optionChar, out var option))
{
errorDetails = "Invalid castling options.";
result = null;
return(false);
}
castlingOptions |= option;
}
}
EnPassantCaptureInfo2?enPassantCaptureInfo = null;
var enPassantCaptureTargetSnippet = fenSnippets[3];
if (enPassantCaptureTargetSnippet != ChessConstants.NoEnPassantCaptureFenSnippet)
{
const string InvalidEnPassant = "Invalid en-passant.";
var captureSquare = Square.TryFromAlgebraic(enPassantCaptureTargetSnippet);
if (!captureSquare.HasValue)
{
errorDetails = InvalidEnPassant;
result = null;
return(false);
}
var enPassantInfo =
ChessConstants.GameSideToDoublePushInfoMap.Values.SingleOrDefault(
obj => obj.CaptureTargetRank == captureSquare.Value.Rank);
if (enPassantInfo is null)
{
errorDetails = InvalidEnPassant;
result = null;
return(false);
}
enPassantCaptureInfo = new EnPassantCaptureInfo2(
captureSquare.Value,
new Square(captureSquare.Value.File, enPassantInfo.EndRank));
}
var halfMovesBy50MoveRuleSnippet = fenSnippets[4];
if (!ChessHelper.TryParseInt(halfMovesBy50MoveRuleSnippet, out var halfMovesBy50MoveRule) ||
halfMovesBy50MoveRule < 0)
{
errorDetails = "Invalid half move counter for the 50 move rule.";
result = null;
return(false);
}
var fullMoveIndexSnippet = fenSnippets[5];
if (!ChessHelper.TryParseInt(fullMoveIndexSnippet, out var fullMoveIndex) || fullMoveIndex <= 0)
{
errorDetails = "Invalid move index.";
result = null;
return(false);
}
result = new StandardGamePosition(
piecePosition,
activeSide,
fullMoveIndex,
castlingOptions,
enPassantCaptureInfo,
halfMovesBy50MoveRule);
errorDetails = null;
return(true);
}