/// <summary>
/// Implementation of the minimax algorithm. Determines the best move for the current
/// board by playing every move combination until the end of the game.
/// </summary>
public static Space GetBestMove(GameBoard gb, Player p)
{
Space? bestSpace = null;
List<Space> openSpaces = gb.OpenSquares;
GameBoard newBoard;
for (int i = 0; i < openSpaces.Count; i++)
{
newBoard = gb.Clone();
Space newSpace = openSpaces[i];
newBoard[newSpace.X, newSpace.Y] = p;
if (newBoard.Winner == Player.Open && newBoard.OpenSquares.Count > 0)
{
Space tempMove = GetBestMove(newBoard, ((Player)(-(int)p))); //a little hacky, inverts the current player
newSpace.Rank = tempMove.Rank;
}
else
{
if (newBoard.Winner == Player.Open)
newSpace.Rank = 0;
else if (newBoard.Winner == Player.X)
newSpace.Rank = -1;
else if (newBoard.Winner == Player.O)
newSpace.Rank = 1;
}
//If the new move is better than our previous move, take it
if (bestSpace == null ||
(p == Player.X && newSpace.Rank < ((Space)bestSpace).Rank) ||
(p == Player.O && newSpace.Rank > ((Space)bestSpace).Rank))
{
bestSpace = newSpace;
}
}
return (Space)bestSpace;
}