/// <summary>
/// Verifies the current board for draw by insufficient material.
/// </summary>
/// <returns></returns>
private bool IsDrawInsufficientMaterial()
{
// "N" is true if there is one White Knight
// "B" is true if there is one White Bishop
// "BW" is true if the White Bishop is on a white square
// "n" is true if there is one Black Knight
// "b" is true if there is one Black Bishop
// "bw" is true if the Black Bishop is on a white square
bool N, B, BW, n, b, bw;
N = B = BW = n = b = bw = false;
// loop through the squares
for (int sqIndex = 0; sqIndex < Board.SquareNo; sqIndex++)
{
if (currentBoard[sqIndex] != null)
{
if (currentBoard[sqIndex] is WhiteKnight)
{
// if there is more than one White Knight there is no draw by insufficient material
if (N)
{
return(false);
}
N = true;
continue;
}
if (currentBoard[sqIndex] is WhiteBishop)
{
// if there is more than one White Bishop there is no draw by insufficient material
if (B)
{
return(false);
}
B = true;
// remember the Bishop square colour
BW = Board.IsWhiteSquare(sqIndex);
continue;
}
if (currentBoard[sqIndex] is BlackKnight)
{
// if there is more than one Black Knight there is no draw by insufficient material
if (n)
{
return(false);
}
n = true;
continue;
}
if (currentBoard[sqIndex] is BlackBishop)
{
// if there are more than one Black Bishop there is no draw by insufficient material
if (b)
{
return(false);
}
b = true;
// remember the Bishop square colour
bw = Board.IsWhiteSquare(sqIndex);
continue;
}
// there will be always the King
if (currentBoard[sqIndex] is IKing)
{
continue;
}
// if there is a piece which is not Bishop, Knight or King there is no draw by insufficient material
return(false);
}
}
// if there are only the kings
if (!B && !b && !N && !n)
{
return(true);
}
// if there are only the kings and one bishop on one side
if ((b && !B && !N && !n) || (B && !b && !n && !N))
{
return(true);
}
// if there are only the kings and one knight on one side
if ((n && !N && !B && !b) || (N && !n && !b && !B))
{
return(true);
}
// if there are only the kings and one bishop on each side, both of them on squares with the same colour
if (B && b && !N && !n && (bw == BW))
{
return(true);
}
return(false);
}