/// <summary>
/// Get directions where there's a playable move
/// </summary>
/// <param name="position">Position to check</param>
/// <returns>List of directions</returns>
public List <IntPosition> GetNeighborsDirections(IntPosition position)
{
List <IntPosition> directionsList = new List <IntPosition>();
Player currentPlayer = playerTurn;
Player oppositePlayer = GetOppositePlayer(currentPlayer);
for (int rowDelta = -1; rowDelta <= 1; rowDelta++)
{
for (int columnDelta = -1; columnDelta <= 1; columnDelta++)
{
IntPosition nextPosition = new IntPosition(position.Column + columnDelta, position.Row + rowDelta);
if (IsPositionValid(nextPosition))
{
int slotContentId = gameBoard[nextPosition.Column, nextPosition.Row];
if ((position.Row != nextPosition.Row || position.Column != nextPosition.Column) &&
slotContentId == (int)oppositePlayer &&
IsPositionValid(nextPosition))
{
directionsList.Add(new IntPosition(columnDelta, rowDelta));
}
}
}
}
return(directionsList);
}
/// <summary>
/// Get a list of positions where a pawn has to be flipped, given the position where a new pawn is to be placed.
/// This is basically the effect of a new move on the board.
/// NB: the list does not contain the new pawn.
/// </summary>
/// <param name="pawnPosition">Pawn position</param>
/// <returns>List of positions where to flip pawns</returns>
public List <IntPosition> GetPawnsToFlip(IntPosition pawnPosition)
{
List <IntPosition> pawnsToFlip = new List <IntPosition>();
List <IntPosition> directionsList = GetNeighborsDirections(pawnPosition);
foreach (IntPosition direction in directionsList)
{
List <IntPosition> currentPath = new List <IntPosition>();
Player currentPlayer = playerTurn;
Player oppositePlayer = GetOppositePlayer(currentPlayer);
IntPosition currentPosition = pawnPosition;
currentPosition += direction;
while (IsPositionValid(currentPosition) && gameBoard[currentPosition.Column, currentPosition.Row] == (int)oppositePlayer)
{
currentPath.Add(currentPosition);
currentPosition += direction;
}
if (IsPositionValid(currentPosition) && gameBoard[currentPosition.Column, currentPosition.Row] == (int)currentPlayer)
{
pawnsToFlip.AddRange(currentPath);
}
}
return(pawnsToFlip);
}
/// <summary>
/// Implementation of negamax algorithm with alpha beta pruning. A node is represented by a game board.
/// </summary>
/// <param name="nodeBoard">A particular game state</param>
/// <param name="depth">The maximum tree depth</param>
/// <param name="parentValue">The parent node value</param>
/// <param name="maximizingPlayer">Whether node is a maximizimer or minimizer. True if maximizer. </param>
/// <returns>A tuple containing the value as it's first item and the position corresponding to the best
/// predicted play as it's second item. </returns>
private Tuple <int, IntPosition> AlphaBeta(BoardIA nodeBoard, int depth, int parentValue, bool maximizingPlayer)
{
if (depth == 0 || nodeBoard.IsTerminal())
{
var heuristicValue = nodeBoard.GetHeuristicValue();
return(new Tuple <int, IntPosition>(heuristicValue, new IntPosition(-1, -1)));
}
else
{
int bestValue = maximizingPlayer ? -int.MaxValue : int.MaxValue;
IntPosition bestMove = new IntPosition(-1, -1);
var childPositions = nodeBoard.GetAllPossibleMoves();
foreach (var child in childPositions)
{
var childValue = AlphaBeta(PosToBoard(child, nodeBoard), depth - 1, bestValue, !maximizingPlayer);
int minOrMax = maximizingPlayer ? 1 : -1;
if (childValue.Item1 * minOrMax > bestValue * minOrMax)
{
bestValue = childValue.Item1;
bestMove = child;
if (bestValue * minOrMax > parentValue * minOrMax)
{
break;
}
}
}
return(new Tuple <int, IntPosition>(bestValue, bestMove));
}
}
/// <summary>
/// Initialize all the data of the game
/// </summary>
/// <param name="gridSize">Size of the board</param>
/// <param name="initialPawnsPosition">Initial position of the pawns (top left corner)</param>
public void InitAll(IntPosition gridSize, IntPosition initialPawnsPosition)
{
playerTurn = Player.Black;
InitPlayersData();
InitGameBoard(gridSize, initialPawnsPosition);
InitTimer();
moveHistory = new List <Tuple <List <IntPosition>, Player> >();
}
/// <summary>
/// Check whether the given position is legal.
/// </summary>
/// <param name="column">Column number of the position to check</param>
/// <param name="line">Line number of the position to check</param>
/// <param name="isWhite">True if player turn is white</param>
/// <returns>True if move is legal</returns>
public bool IsPlayable(int column, int line, bool isWhite)
{
Player currentPlayer = PlayerTurn;
PlayerTurn = isWhite ? Player.White : Player.Black;
IntPosition positionToCheck = new IntPosition(column, line);
List <IntPosition> playableSlots = GetAllPossibleMoves();
PlayerTurn = currentPlayer;
return(playableSlots.Contains(positionToCheck));
}
/// <summary>
/// Check if a move is stable
/// </summary>
/// <param name="position">Position to check stability</param>
/// <returns>True : stable, False : not stable</returns>
private bool IsMoveStable(IntPosition position, bool isWhite)
{
int[,] gameBoardSave = CopyArray(GameBoard);
List <IntPosition> result = new List <IntPosition>();
int playerId = isWhite ? (int)Player.White : (int)Player.Black;
GameBoard[position.Column, position.Row] = playerId;
List <IntPosition> pawnsToFlip = GetPawnsToFlip(position);
foreach (IntPosition pawnPos in pawnsToFlip)
{
GameBoard[pawnPos.Column, pawnPos.Row] = (int)(GetOppositePlayer((Player)playerId));
}
// Tests valid moves for the opposite players
SwitchPlayer();
for (int rowDelta = -1; rowDelta <= 1; rowDelta++)
{
for (int columnDelta = -1; columnDelta <= 1; columnDelta++)
{
if (!(columnDelta == 0 && rowDelta == 0))
{
try
{
IntPosition nextPosition = new IntPosition(position.Column + columnDelta, position.Row + rowDelta);
while (IsPositionValid(nextPosition) && GameBoard[nextPosition.Column, nextPosition.Row] == playerId)
{
nextPosition = new IntPosition(nextPosition.Column + columnDelta, nextPosition.Row + rowDelta);
}
if (IsPositionValid(nextPosition) && GameBoard[nextPosition.Column, nextPosition.Row] == (int)GetOppositePlayer((Player)playerId))
{
if (IsPossibleMove(nextPosition, new IntPosition(-columnDelta, -rowDelta), result))
{
GameBoard = gameBoardSave;
SwitchPlayer();
return(false);
}
}
}
catch (Exception exc)
{
Console.WriteLine(exc.Message);
}
}
}
}
SwitchPlayer();
GameBoard = gameBoardSave;
return(true);
}
/// <summary>
/// Play a move and alter the board accordingly. Returns true if the move was legal.
/// </summary>
/// <param name="column">The column corresponding to the position of the move</param>
/// <param name="line">The line corresponding to the position of the move</param>
/// <param name="isWhite">True if the current player turn is white</param>
/// <returns>True if move was legal.</returns>
public bool PlayMove(int column, int line, bool isWhite)
{
PlayerTurn = isWhite ? Player.White : Player.Black;
bool IsMoveValid = IsPlayable(column, line, isWhite);
if (IsMoveValid)
{
IntPosition slotPosition = new IntPosition(column, line);
List <IntPosition> pawnsToFlip = GetPawnsToFlip(slotPosition);
pawnsToFlip.Add(slotPosition);
UpdateSlots(pawnsToFlip);
}
return(IsMoveValid);
}
/// <summary>
/// Gets the most recent move stored and plays it backwards.
/// </summary>
/// <returns>
/// A tuple containing the coordinates of the affected slots, which
/// player the move belongs to and the coordinates of the pawn that
/// was added to the board (which now has to be removed).
/// </returns>
public Tuple <List <IntPosition>, Player, IntPosition> UndoMove()
{
var lastMove = moveHistory.Last();
List <IntPosition> slotsToUndo = lastMove.Item1;
Player moveAuthor = lastMove.Item2;
IntPosition lastPawnPosition = slotsToUndo.Last();
slotsToUndo.RemoveAt(slotsToUndo.Count - 1);
foreach (var position in slotsToUndo)
{
GameBoard[position.Column, position.Row] = (int)GetOppositePlayer(moveAuthor);
}
GameBoard[lastPawnPosition.Column, lastPawnPosition.Row] = (int)SlotContent.Nothing;
moveHistory.RemoveAt(moveHistory.Count - 1);
return(Tuple.Create(slotsToUndo, moveAuthor, lastPawnPosition));
}
/// <summary>
/// Init. the game board
/// </summary>
/// <param name="gridSize">Size of the board</param>
/// <param name="initialPawnsPosition">Initial position of the pawns (top left corner)</param>
public void InitGameBoard(IntPosition gridSize, IntPosition initialPawnsPosition)
{
gameBoard = new int[gridSize.Column, gridSize.Row];
for (int row = 0; row < Rows; row++)
{
for (int column = 0; column < Columns; column++)
{
gameBoard[column, row] = (int)SlotContent.Nothing;
}
}
gameBoard[initialPawnsPosition.Column, initialPawnsPosition.Row] = (int)SlotContent.White;
gameBoard[initialPawnsPosition.Column + 1, initialPawnsPosition.Row] = (int)SlotContent.Black;
gameBoard[initialPawnsPosition.Column, initialPawnsPosition.Row + 1] = (int)SlotContent.Black;
gameBoard[initialPawnsPosition.Column + 1, initialPawnsPosition.Row + 1] = (int)SlotContent.White;
}
/// <summary>
/// Creates an AIBoard class given the position of a move to play
/// and the board where the move has to be played.
/// </summary>
/// <param name="position">The position of the pawn to play on the board</param>
/// <param name="sourceBoard">The board where the move takes place</param>
/// <returns>A new AIBoard with the updated game state</returns>
private BoardIA PosToBoard(IntPosition position, BoardIA sourceBoard)
{
int[,] gameState = new int[9, 7];
for (int i = 0; i < 9; i++)
{
for (int j = 0; j < 7; j++)
{
gameState[i, j] = sourceBoard.GameBoard[i, j];
}
}
BoardIA newBoard = new BoardIA
{
GameBoard = gameState,
PlayerTurn = sourceBoard.PlayerTurn
};
newBoard.PlayMove(position.Column, position.Row, sourceBoard.PlayerTurn == Player.White);
newBoard.SwitchPlayer();
return(newBoard);
}
/// <summary>
/// Walk the game board to get all possible moves for the current player.
/// </summary>
/// <returns>
/// A list containing the position of each playable slot.
/// </returns>
public List <IntPosition> GetAllPossibleMoves()
{
List <IntPosition> possibleMovesList = new List <IntPosition>();
for (int rowIndex = 0; rowIndex < Rows; rowIndex++)
{
for (int columnIndex = 0; columnIndex < Columns; columnIndex++)
{
IntPosition currentSlot = new IntPosition(columnIndex, rowIndex);
int slotContentId = gameBoard[currentSlot.Column, currentSlot.Row];
if (slotContentId == (int)playerTurn)
{
List <IntPosition> currentSlotPossibleMovesList = GetNeighborsDirections(currentSlot);
List <IntPosition> movements = new List <IntPosition>();
foreach (IntPosition direction in currentSlotPossibleMovesList)
{
if (IsPossibleMove(currentSlot, direction, movements))
{
IntPosition possibleMove = movements[movements.Count - 1];
possibleMovesList.Add(possibleMove);
}
movements.Clear();
}
}
}
}
if (possibleMovesList.Count == 0)
{
SkipCurrentPlayerTurn();
}
else
{
CurrentPlayerData.HasSkippedLastTurn = false;
}
return(possibleMovesList);
}
/// <summary>
/// Check if there's a valid move in the given direction, if true, the "positions" list is filled with all the positions of the valid move
/// </summary>
/// <param name="pawnPosition">Position to check</param>
/// <param name="direction">Direction to check</param>
/// <param name="positions">Empty list given by the user, filled with severals position if there's a valid move</param>
/// <returns></returns>
public bool IsPossibleMove(IntPosition pawnPosition, IntPosition direction, List <IntPosition> positions)
{
IntPosition currentPosition = pawnPosition;
bool result = false;
Player currentPlayer = playerTurn;
Player oppositePlayer = GetOppositePlayer(currentPlayer);
positions.Add(pawnPosition);
currentPosition += direction;
while (IsPositionValid(currentPosition) && gameBoard[currentPosition.Column, currentPosition.Row] == (int)oppositePlayer)
{
positions.Add(currentPosition);
currentPosition += direction;
}
if (result = IsPositionValid(currentPosition) && (gameBoard[currentPosition.Column, currentPosition.Row] == (int)SlotContent.Nothing))
{
positions.Add(currentPosition);
}
return(result);
}
/// <summary>
/// Overloaded constructor: can define the size of the board and the initial position of the pawns (top left corner)
/// </summary>
/// <param name="gridSize">Size of the board</param>
/// <param name="initialPawnsPosition">Initial position of the pawns (top left corner)</param>
public OthelloLogic(IntPosition gridSize, IntPosition initialPawnsPosition)
{
InitAll(gridSize, initialPawnsPosition);
}
/// <summary>
/// Check if the position is inside the board
/// </summary>
/// <param name="position">Position to check</param>
/// <returns>True if the position is inside board, false otherwise</returns>
public bool IsPositionValid(IntPosition position)
{
return(position.Row >= 0 && position.Row < Rows && position.Column >= 0 && position.Column < Columns);
}
