best_move: BitMove = undefined,
    ply: usize = 0,
    var buf: [16]u8 = undefined;

    fn searchPosition(self: *@This(), depth: usize) Str {
        const ALPHA = -5000;
        const BETA = 5000;
        _ = self.negamax(ALPHA, BETA, depth) catch unreachable;

        return std.fmt.bufPrint(&buf, "bestmove {s}{s}{s}\n", .{
            @tagName(self.best_move.source),
            @tagName(self.best_move.target),
            if (self.best_move.prom != .none) @tagName(self.best_move.prom) else "",
        }) catch unreachable;
    }
    fn negamax(self: *@This(), alpha_orig: isize, beta_orig: isize, depth: usize) !isize {
        if (depth == 0) return self.evaluate();
        var alpha = alpha_orig;
        var beta = beta_orig;
        // TODO
        // nodes += 1;
        var best_sofar: BitMove = undefined;
        var ml = try MoveList.init(0);
        try self.generateMoves(&ml);
        for (ml.slice()) |move, idx| {
            var bck: GameState = undefined;
            self.backup(&bck);
            self.ply += 1;
            if (!self.makeMove(move, .all)) {
                self.ply -= 1;
                self.restore(&bck);
                continue;
            }
            const score = -try self.negamax(-beta, -alpha, depth - 1);
            self.ply -= 1;
            self.restore(&bck);
            // fail-hard beta cutoff
            if (score >= beta) {
                // node (move) fails high
                return beta;
            }
            // found a better move
            if (score > alpha) {
                // PV (principal validation) node
                alpha = score;
                // if root move
                if (self.ply == 0) {
                    best_sofar = ml.get(idx);
                }
            }
        }
        if (alpha_orig != alpha) {
            // init best move
            self.best_move = best_sofar;
        }
        // node (move) fails low
        return alpha;
    }

    }
    fn searchPosition(self: @This(), depth: u4) Str {
        _ = self;
        _ = depth;
        return "bestmove d2d4\n";

    pub fn parseGo(self: @This(), in: Str) !Str {

    pub fn parseGo(self: *@This(), in: Str) !Str {

test "searchPosition" {
    var gs = try GameState.init(null);
    gs.show();
    std.debug.print("{s}", .{gs.searchPosition(4)});
}