public static string Encode(IReadOnlyPosition position,
EncodingOptions options = EncodingOptions.None)
{
Debug.Assert(position != null);
var s = new StringBuilder(80);
// Encode the chessboard
var board = Factory.Instance.CreateChessboardArray(position);
for (int row = Chessboard.ROW_MAX; row >= Chessboard.ROW_MIN; --row)
{
int empty_cells = 0;
for (int column = Chessboard.COLUMN_MIN;
column <= Chessboard.COLUMN_MAX; ++column)
{
var cur_cell = new ChessboardCell(row, column);
Players player;
Pieces piece;
if (board.IsPieceAt(cur_cell, out player, out piece))
{
if (empty_cells != 0)
{
s.Append(empty_cells);
empty_cells = 0;
}
s.Append(PieceToChar(player, piece));
}
else
{
++empty_cells;
}
}
if (empty_cells != 0)
{
s.Append(empty_cells);
empty_cells = 0;
}
if (row != Chessboard.ROW_MIN)
{
s.Append(ROWS_SEPARATOR);
}
}
// Encode player to move
s.Append(' ');
s.Append(position.IsWhiteToMove ? FEN_WHITE_TO_MOVE : FEN_BLACK_TO_MOVE);
// Encode castling availability
s.Append(' ');
if (!position.IsCanCastleShort(Players.White)
&& !position.IsCanCastleLong(Players.White)
&& !position.IsCanCastleShort(Players.Black)
&& !position.IsCanCastleLong(Players.Black))
{
s.Append(FEN_NO_ONE_CAN_CASTLE);
}
else
{
if (position.IsCanCastleShort(Players.White))
{
s.Append(FEN_WHITE_CAN_CASTLE_SHORT);
}
if (position.IsCanCastleLong(Players.White))
{
s.Append(FEN_WHITE_CAN_CASTLE_LONG);
}
if (position.IsCanCastleShort(Players.Black))
{
s.Append(FEN_BLACK_CAN_CASTLE_SHORT);
}
if (position.IsCanCastleLong(Players.Black))
{
s.Append(FEN_BLACK_CAN_CASTLE_LONG);
}
}
// Encode en passant caputre possibility
s.Append(' ');
int? capture_en_passant_column = position.CaptureEnPassantColumn;
if (capture_en_passant_column.HasValue)
{
var cell = new ChessboardCell(position.IsWhiteToMove ? 5 : 2,
capture_en_passant_column.Value);
s.Append(cell.ToString());
}
else
{
s.Append(FEN_CANNOT_CAPTURE_EN_PASSANT);
}
s.Append(' ').Append(position.HalfmoveClock);
s.Append(' ').Append(options.HasFlag(EncodingOptions.SetMovesCountToOne)
? 1 : position.FullmoveNumber);
return s.ToString();
}
