public Position Read(string fenString)
{
try
{
PieceArray whitePieces = new PieceArray(0),
blackPieces = new PieceArray(1);
var chunks = fenString.Split();
bool isChess960 = !chunks[2].ToLower().Any(c => c == 'q' || c == 'k');
var boardChunks = chunks[0].Split(new[] { '/' });
for (int rank = 0; rank < Constants.BoardRanks; rank++)
{
var rankChunk = boardChunks[rank];
int file = 0;
foreach (var item in rankChunk)
{
if (int.TryParse(item.ToString(), out var gap))
{
file += gap;
}
else
{
int square = rank * Constants.BoardFiles + file;
int piece = NotationHelper.GetPiece(item);
if ((piece & Piece.White) != 0)
{
whitePieces.Add(piece & Piece.TypeMask, square);
}
else
{
blackPieces.Add(piece & Piece.TypeMask, square);
}
file++;
}
}
}
GameState initialGameState = new GameState();
if (chunks[2] != "-")
{
initialGameState[0] = NotationHelper.GetCastlingOptions(chunks[2], true, isChess960, whitePieces.Rooks, whitePieces.King);
initialGameState[1] = NotationHelper.GetCastlingOptions(chunks[2], false, isChess960, blackPieces.Rooks, blackPieces.King);
}
if (chunks[3] != "-")
{
initialGameState.EnPassantSquare = NotationHelper.ParseSquare(chunks[3]);
}
int totalMoves = 1;
if (chunks.Length > 4)
{
initialGameState.HalfMoveClock = int.Parse(chunks[4]);
totalMoves = int.Parse(chunks[5]);
}
return(new Position(whitePieces, blackPieces, initialGameState)
{
WhiteToMove = chunks[1].ToLower() == "w",
TotalMoves = totalMoves,
IsChess960 = isChess960
});
}
catch (Exception e)
{
throw new FormatException($"Wrong fen string: {fenString}", e);
}
}
