fpga: Make rotatable with screwdrivers

mesecons_fpga/depends.txt

@@ -1 +1,2 @@
 mesecons
+screwdriver?

mesecons_fpga/init.lua

@@ -116,6 +116,44 @@ plg.register_nodes({
 	after_dig_node = function(pos, node)
 		mesecon.receptor_off(pos, plg.rules[node.name])
 	end,
+	on_rotate = function(pos, node, user, mode)
+		local abcd1 = {"A", "B", "C", "D"}
+		local abcd2 = {A = 1, B = 2, C = 3, D = 4}
+		local ops = {"op1", "op2", "dst"}
+		local dir = 0
+		if mode == screwdriver.ROTATE_FACE then -- clock-wise
+			dir = 1
+			if user and user:is_player() then
+				minetest.chat_send_player(user:get_player_name(),
+						"FPGA ports have been rotated clockwise.")
+			end
+		elseif mode == screwdriver.ROTATE_AXIS then -- counter-clockwise
+			dir = -1
+			if user and user:is_player() then
+				minetest.chat_send_player(user:get_player_name(),
+						"FPGA ports have been rotated counter-clockwise.")
+			end
+		end
+
+		local meta = minetest.get_meta(pos)
+		local instr = lcore.deserialize(meta:get_string("instr"))
+		for i = 1, #instr do
+			for _, op in ipairs(ops) do
+				local o = instr[i][op]
+				if o and o.type == "io" then
+					local num = abcd2[o.port]
+					num = num + dir
+					if num > 4 then num = 1
+					elseif num < 1 then num = 4 end
+					instr[i][op].port = abcd1[num]
+				end
+			end
+		end
+
+		meta:set_string("instr", lcore.serialize(instr))
+		plg.update_formspec(pos, instr)
+		return true
+	end,
 })