internal MoveMapNode AddChild(Square square)
{
MoveMapNode node = new MoveMapNode(this, square);
_children.Add(node);
return(node);
}
public MoveMap(Piece piece)
{
Square start = piece.Square;
_board = piece.Board;
_colour = start.Occupier.Colour;
_root = new MoveMapNode(null, start);
Generate();
}
private void FindEdges(MoveMapNode node, IList <MoveMapNode> output)
{
if (node.Children.Count() == 0)
{
output.Add(node);
}
else
{
foreach (MoveMapNode childNode in node.Children)
{
FindEdges(childNode, output);
}
}
}
public MoveMap(Board board, int row, int column)
{
Square start = board[row, column];
if (start.IsEmpty)
{
throw new ArgumentException("Starting square must be occupied.");
}
_root = new MoveMapNode(null, start);
_board = board;
_colour = start.Occupier.Colour;
Evaluate();
}
private void Generate()
{
// depending on which player we are evaluating moves for, we need to either move up or down the board
int rowStep = _root.Square.Occupier.Colour == PieceColour.Black ? 1 : -1;
int row = _root.Square.Row;
int column = _root.Square.Column;
TestMove(row + rowStep, column + 1, rowStep, _root);
TestMove(row + rowStep, column - 1, rowStep, _root);
// a crowned piece ('king') may move in the reverse direction as well
if (_root.Square.Occupier.IsCrowned)
{
TestMove(row - rowStep, column + 1, -rowStep, _root);
TestMove(row - rowStep, column - 1, -rowStep, _root);
}
// extract the edges (end squares) of each sequence, and remove those that end in an occupied square on the board's edge,
// as those are not valid move targets
// create a path from each edge which enumerates the squares covered by the move
List <MoveMapNode> edges = new List <MoveMapNode>();
FindEdges(_root, edges);
List <Move> moves = new List <Move>();
foreach (MoveMapNode edge in edges.Where(e => e.Square.IsEmpty))
{
Move move = new Move(edge.Root.Square.Occupier);
MoveMapNode node = edge;
while (true)
{
if (node == null)
{
break;
}
move.Add(node.Square.Row, node.Square.Column);
node = node.Parent;
}
moves.Add(move);
}
// exclude any moves that don't take pieces, if at least one does - we *must* take a piece if it's possible
Moves = moves.Any(m => m.PiecesTaken > 0) ? moves.Where(m => m.PiecesTaken > 0) : moves;
}
private void TestMove(int row, int column, int rowStep, MoveMapNode node)
{
if (row < 0 || column < 0 || row > 7 || column > 7)
{
return; // stepped out of bounds, sequence ends
}
Square square = _board[row, column];
if (square.IsEmpty) // sequence ends here
{
node.AddChild(square);
return;
}
else if (square.Occupier.Colour == _colour) // blocked by piece of own colour, not a valid sequence
{
return;
}
else // sequence *may* continue, so recurse down one level in each diagonal direction
{
MoveMapNode childNode = node.AddChild(square);
TestMove(row + rowStep, column + 1, rowStep, childNode);
TestMove(row + rowStep, column - 1, rowStep, childNode);
}
}
public MoveMapNode(MoveMapNode parent, Square square)
{
_parent = parent;
Square = square;
_children = new List <MoveMapNode>();
}