Working on updated version myself, and it's more complicated as I added new pieces with different actions, but all in all it started pretty simple. I add "score" to each open piece for enemy moves, 100 if it immediately takes a piece, 50 if it creates capture opportunity next move. Then I take those values and "calculate backwards" so any position that would lead to capture next move will get (100/2 - 50 score), any move after that would get (50/2 - +25 score). That way I can look at each piece and check all their possible moves, and pick the highest scoring one.