public static IEnumerable<Piece> GetPiecesBetweenY(this Board board, Piece p1, Piece p2)
{
// Make sure they share axis
if (p1.X != p2.X)
return Enumerable.Empty<Piece>();
// Get first and last piece on line
var first = p1.Y < p2.Y ? p1 : p2;
var last = p1.Y < p2.Y ? p2 : p1;
return board.Pieces.Where(p =>
p.Y > first.Y &&
p.Y < last.Y &&
p.X == p1.X &&
p.State != PieceState.Open);
}
/// <summary>
/// Returns a collection of the pieces that are to be turned if the supplied piece is placed
/// </summary>
public IEnumerable<Piece> GetValidConnectingPieces(Piece piece)
{
var connectingPieces = new List<Piece>();
// Create a new traverser and move it one step in current direction
var traverser = new BoardTraverser(this);
foreach (Direction direction in Enum.GetValues(typeof(Direction)))
{
// List to store connecting pieces in current direction
var connectingPiecesInDirection = new List<Piece>();
// Reset traverser
traverser.SetCoords(piece);
traverser.MovePointer(direction);
// Loop while traverser is within bounds of the board
while (!traverser.OutOfBounds)
{
var current = traverser.GetCurrentPiece();
if (current.State == PieceState.Open)
{
break;
}
else if (Piece.HasOppositeStates(current, piece))
{
connectingPiecesInDirection.Add(current);
}
else if (connectingPiecesInDirection.Count > 0 && current.State != PieceState.Open)
{
// If the last connecting piece is of the same color
// and there are opposite colors in between, add to the list
connectingPieces.AddRange(connectingPiecesInDirection);
break;
}
// Move pointer to the next place
traverser.MovePointer(direction);
}
}
return connectingPieces.AsEnumerable();
}
/// <summary>
/// Returns all filled pieces in specified direction in relation to the speicified piece
/// </summary>
public static IEnumerable<Piece> GetPiecesInDirection(this Board board, Piece piece, Direction dir)
{
IEnumerable<Piece> pieces;
switch (dir)
{
case Direction.North:
pieces = board.Pieces.Where(p =>
p.X == piece.X &&
p.Y > piece.Y
);
break;
case Direction.East:
pieces = board.Pieces.Where(p =>
p.X > piece.X &&
p.Y == piece.Y
);
break;
case Direction.South:
pieces = board.Pieces.Where(p =>
p.X == piece.X &&
p.Y < piece.Y
);
break;
case Direction.West:
pieces = board.Pieces.Where(p =>
p.X < piece.X &&
p.Y == piece.Y
);
break;
default:
return Enumerable.Empty<Piece>();
}
// Return only the fields which are not blank
return pieces.Where(p => p.State != PieceState.Open);
}
public void SetCoords(Piece piece)
{
SetCoords(piece.X, piece.Y);
}
/// <summary>
/// Determine if a piece is equal to Piece.Empty
/// </summary>
public static bool IsEmpty(Piece piece)
{
return piece.Equals(Empty);
}
/// <summary>
/// Determine if two pieces are of the opposite color (state). Throws an exception if one of the pieces are open.
/// </summary>
public static bool HasOppositeStates(Piece p1, Piece p2)
{
if (p1.State == PieceState.Open || p2.State == PieceState.Open)
throw new ArgumentException("One of the states are open and therefore has no opposite state");
return p1.State != p2.State;
}
public static bool IsConnectedY(this Board board, Piece p1, Piece p2)
{
return GetPiecesBetweenY(board, p1, p2).Count() == p1.Y - p2.Y;
}
public static bool IsConnectedX(this Board board, Piece p1, Piece p2)
{
return GetPiecesBetweenX(board, p1, p2).Count() == p1.X - p2.X;
}
public void SetPiece(int x, int y, PieceState state)
{
var piece = GetPiece(x, y);
var dummy = new Piece(piece.X, piece.Y);
dummy.SetState(state);
// Throw an exception if the location has already been set
if (piece.State != PieceState.Open)
throw new ArgumentException("Location already set");
// Throw an exception if placement is invalid
if (!IsPlacingAllowed(dummy))
throw new ArgumentException("The piece does not have any valid adjacent pieces");
// Place the piece
piece.SetState(state);
// Turn connecting pieces
var connectingPieces = GetValidConnectingPieces(piece);
foreach (var p in connectingPieces)
{
p.SetState(state);
}
}
/// <summary>
/// Determines if placing of the piece is a valid placement
/// </summary>
public bool IsPlacingAllowed(Piece piece)
{
return GetValidConnectingPieces(piece).Count() > 0;
}