private static Bitboard[] InitializeKnightAttacksOrMoves()
{
var result = new Bitboard[ChessConstants.SquareCount];
for (var squareIndex = 0; squareIndex < ChessConstants.SquareCount; squareIndex++)
{
var square = new Square(squareIndex);
var moveSquares = ChessHelper.GetKnightMoveSquares(square);
var bitboard = new Bitboard(moveSquares);
result[squareIndex] = bitboard;
}
return(result);
}
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);
}