private int Evaluate(HexAIMove move, Game game)
{
int score = random.Next(0, 25); // avoid making every run the same
var state = game.GetCurrentBoardState();
Team ourTeam = state.currentMove;
Team enemy = ourTeam.Enemy();
(BoardState newState, List <Promotion> newPromotions) = move.Speculate(game);
bool weAreChecking = MoveValidator.IsChecking(ourTeam, newState, newPromotions);
bool enemyHasMoves = MoveValidator.HasAnyValidMoves(enemy, newPromotions, newState, state);
if (weAreChecking && !enemyHasMoves)
{
return(int.MaxValue);
}
if (weAreChecking)
{
score += CheckBonus;
}
if (!enemyHasMoves)
{
score -= StalematePenalty;
}
if (move.moveType == MoveType.Attack)
{
var attacker = HexachessagonEngine.GetRealPiece(move.start, state, game.promotions);
var victim = HexachessagonEngine.GetRealPiece(move.target, state, game.promotions);
score += AttackBonus;
score += GetPieceValue(victim) - GetPieceValue(attacker);
}
else if (move.moveType == MoveType.EnPassant)
{
score += EnPassantBonus;
}
else if (move.moveType == MoveType.Move)
{
var mover = state.allPiecePositions[move.start];
if (mover.piece.IsPawn())
{
int ranksForward = move.target.GetNumber() - move.start.GetNumber();
if (ourTeam == Team.Black)
{
ranksForward = -ranksForward;
}
ranksForward *= 5;
score *= ranksForward;
}
}
else
{
// Defend is pretty worthless for a bloodthirsty AI
score -= 10;
}
return(score);
}
/// <summary>
/// Is a piece from <paramref name="checkForTeam"/> attacking the enemy king?
/// </summary>
/// <param name="checkForTeam"></param>
/// <returns>true if the enemy king is threatened</returns>
public static bool IsChecking(Team checkForTeam, BoardState state, List <Promotion> promotions)
{
Team enemy = checkForTeam.Enemy();
if (!state.allPiecePositions.TryGetValue((enemy, Piece.King), out Index enemyKingLoc))
{
return(false);
}
foreach (var rayDirection in EnumArray <HexNeighborDirection> .Values)
{
Index?hex = enemyKingLoc;
(Team team, Piece piece)occupier;
bool isBishopDirection = rayDirection switch
{
HexNeighborDirection.Up => false,
HexNeighborDirection.Down => false,
_ => true
};
bool isRookDirection = !isBishopDirection;
bool isPawnDirection = rayDirection switch
{
HexNeighborDirection.DownLeft => checkForTeam == Team.White,
HexNeighborDirection.DownRight => checkForTeam == Team.White,
HexNeighborDirection.UpLeft => checkForTeam != Team.White,
HexNeighborDirection.UpRight => checkForTeam != Team.White,
_ => false
};
for (int distance = 1; distance < 20; distance++)
{
hex = hex.Value.GetNeighborAt(rayDirection);
if (!hex.HasValue)
{
break;
}
if (state.allPiecePositions.TryGetValue(hex.Value, out occupier))
{
if (occupier.team == checkForTeam)
{
Piece realPiece = HexachessagonEngine.GetRealPiece(occupier, promotions);
if (distance == 1)
{
if (isPawnDirection && realPiece.IsPawn())
{
return(true);
}
if (realPiece == Piece.King)
{
return(true);
}
}
if (isBishopDirection && (realPiece.IsBishop() || realPiece == Piece.Queen))
{
return(true);
}
if (isRookDirection && (realPiece.IsRook() || realPiece == Piece.Queen))
{
return(true);
}
}
break;
}
}
}
foreach ((Index target, MoveType moveType)move in MoveGenerator.GetAllPossibleMoves(enemyKingLoc, Piece.BlackSquire, enemy, state, promotions))
{
if (move.moveType == MoveType.Attack && state.TryGetPiece(move.target, out var occupier))
{
Piece realPiece = HexachessagonEngine.GetRealPiece(occupier, promotions);
if (realPiece.IsSquire())
{
return(true);
}
}
}
foreach ((Index target, MoveType moveType)move in MoveGenerator.GetAllPossibleMoves(enemyKingLoc, Piece.KingsKnight, enemy, state, promotions))
{
if (move.moveType == MoveType.Attack && state.TryGetPiece(move.target, out var occupier))
{
Piece realPiece = HexachessagonEngine.GetRealPiece(occupier, promotions);
if (realPiece.IsKnight())
{
return(true);
}
}
}
for (int i = 1; i < 20; ++i) // Queen/Rook slide left
{
Index hex = new Index(enemyKingLoc.row, enemyKingLoc.col - i);
if (!hex.IsInBounds)
{
break;
}
if (state.TryGetPiece(hex, out (Team team, Piece piece)occupier))
{
if (occupier.team == checkForTeam)
{
Piece realPiece = HexachessagonEngine.GetRealPiece(occupier, promotions);
if (realPiece.IsRook() || realPiece == Piece.Queen)
{
return(true);
}
}
break;
}
}
for (int i = 1; i < 20; i++) // Queen/Rook slide right
{
Index hex = new Index(enemyKingLoc.row, enemyKingLoc.col + i);
if (!hex.IsInBounds)
{
break;
}
if (state.TryGetPiece(hex, out (Team team, Piece piece)occupier))
{
if (occupier.team == checkForTeam)
{
Piece realPiece = HexachessagonEngine.GetRealPiece(occupier, promotions);
if (realPiece.IsRook() || realPiece == Piece.Queen)
{
return(true);
}
}
break;
}
}
return(false);
}