internal int Minimax(IGameBoard gameBoard, Mark currentMark)
{
var score = EvaluateMove(gameBoard, currentMark);
if (score == winValue || score == loseValue)
{
return(score);
}
if (!gameBoard.HasMovesLeft)
{
return(0);
}
int best;
if (currentMark == aiMark)
{
best = int.MinValue;
foreach (var openLocation in gameBoard.GetOpenLocations())
{
// try the location
gameBoard.PlaceChoice(currentMark, openLocation);
best = Math.Max(best,
this.Minimax(gameBoard, currentMark.GetOpposite()));
// clean up after our dirty self
gameBoard.RemoveChoice(currentMark, openLocation);
}
}
else
{
best = int.MaxValue;
foreach (var openLocation in gameBoard.GetOpenLocations())
{
// try the location
gameBoard.PlaceChoice(currentMark, openLocation);
best = Math.Min(best,
this.Minimax(gameBoard, currentMark.GetOpposite()));
// clean up after our dirty self
gameBoard.RemoveChoice(currentMark, openLocation);
}
}
return(best);
}
public Task PlayTurn(IGameBoard gameBoard, Mark mark)
{
// todo: this feels weird
this.aiMark = mark;
int bestMoveVal = int.MaxValue;
int bestMoveLocation = -1;
foreach (var openLocation in gameBoard.GetOpenLocations())
{
// try the move
gameBoard.PlaceChoice(mark, openLocation);
var moveValue = Minimax(gameBoard, mark.GetOpposite());
if (moveValue < bestMoveVal)
{
bestMoveVal = moveValue;
bestMoveLocation = openLocation;
}
gameBoard.RemoveChoice(mark, openLocation);
}
gameBoard.PlaceChoice(mark, bestMoveLocation);
return(Task.FromResult(0));
}
