/// <summary>
/// Updates the hash key depending on a move
/// </summary>
/// <param name="move">The move the hash key is depending on</param>
private void UpdateKey(Move move)
{
// TODO : Merge with MakeMove to avoid duplicate ifs
var pawnKey = State.PawnStructureKey;
var key = State.Key ^ pawnKey;
pawnKey ^= Zobrist.GetZobristSide();
if (_stateList[PositionIndex - 1].EnPassantSquare != ESquare.none)
{
key ^= Zobrist.GetZobristEnPessant(_stateList[PositionIndex - 1].EnPassantSquare.File().AsInt());
}
if (State.EnPassantSquare != ESquare.none)
{
key ^= Zobrist.GetZobristEnPessant(State.EnPassantSquare.File().AsInt());
}
if (move.IsNullMove())
{
key ^= pawnKey;
State.Key = key;
State.PawnStructureKey = pawnKey;
return;
}
var pawnPiece = move.GetMovingPieceType() == EPieceType.Pawn;
if (pawnPiece)
{
pawnKey ^= Zobrist.GetZobristPst(move.GetMovingPiece(), move.GetFromSquare());
}
else
{
key ^= Zobrist.GetZobristPst(move.GetMovingPiece(), move.GetFromSquare());
}
var squareTo = move.GetToSquare();
if (move.IsPromotionMove())
{
key ^= Zobrist.GetZobristPst(move.GetPromotedPiece(), squareTo);
}
else
{
if (pawnPiece)
{
pawnKey ^= Zobrist.GetZobristPst(move.GetMovingPiece(), squareTo);
}
else
{
key ^= Zobrist.GetZobristPst(move.GetMovingPiece(), squareTo);
}
}
if (pawnPiece && move.IsEnPassantMove())
{
pawnKey ^= Zobrist.GetZobristPst(move.GetCapturedPiece().Type() + (State.SideToMove << 3), squareTo + (State.SideToMove.Side == 0 ? 8 : -8));
}
else if (move.IsCaptureMove())
{
if (pawnPiece)
{
pawnKey ^= Zobrist.GetZobristPst(move.GetCapturedPiece(), squareTo);
}
else
{
key ^= Zobrist.GetZobristPst(move.GetCapturedPiece(), squareTo);
}
}
else if (move.IsCastlelingMove())
{
var piece = (EPieces)(EPieceType.Rook + move.GetSideMask());
key ^= Zobrist.GetZobristPst(piece, Position.GetRookCastleFrom(squareTo));
key ^= Zobrist.GetZobristPst(piece, squareTo.GetRookCastleTo());
}
// castleling
// castling rights
if (State.CastlelingRights != _stateList[PositionIndex - 1].CastlelingRights)
{
key ^= Zobrist.GetZobristCastleling(_stateList[PositionIndex - 1].CastlelingRights);
key ^= Zobrist.GetZobristCastleling(State.CastlelingRights);
}
key ^= pawnKey;
State.Key = key;
State.PawnStructureKey = pawnKey;
}