local function validate(pos)
  local meta = minetest.get_meta(pos)
  if meta:get_string("sparktech_energy_trig") == "" then
    meta:set_string("sparktech_energy_trig", "yyxxzz")
  end
end

local function execution_check(pos, fromdir)
  local ret = false
  if minetest.get_item_group(minetest.get_node(pos).name, "sparktech_energy_conductor") > 0 then
    validate(pos)
    local nodemeta = minetest.get_meta(pos)
    local dir = 0
    if fromdir % 2 == 0 then
      dir = fromdir - 1
    else
      dir = fromdir + 1
    end

    local string = nodemeta:get_string("sparktech_energy_trig")
    local letter = string:sub(dir, dir)
    if letter:byte() >= 97 and letter:byte() <= 122 then
      nodemeta:set_string("sparktech_energy_trig", "" .. string:sub(1, dir - 1) .. letter:upper() .. string:sub(dir + 1, 6))
      ret = true
    else
      nodemeta:set_string("sparktech_energy_trig", "" .. string:sub(1, dir - 1) .. letter:lower() .. string:sub(dir + 1, 6))
    end
  end
  return ret
end

local function energy_logic(node, pos)
  local node_m = minetest.get_meta(pos)
  local node_con = minetest.get_item_group(node.name, "sparktech_energy_conductor")
  local node_in = minetest.get_item_group(node.name, "sparktech_energy_in")
  local node_out = minetest.get_item_group(node.name, "sparktech_energy_out")
  local node_max = minetest.get_item_group(node.name, "sparktech_energy_max")

  local top = {x = pos.x, y = pos.y + 1, z = pos.z}
  local bottom = {x = pos.x, y = pos.y - 1, z = pos.z}
  local left = {x = pos.x - 1, y = pos.y, z = pos.z}
  local right = {x = pos.x + 1, y = pos.y, z = pos.z}
  local front = {x = pos.x, y = pos.y, z = pos.z - 1}
  local back = {x = pos.x, y = pos.y, z = pos.z + 1}

  local dir = {top, bottom, left, right, front, back}
  local edir = {}

  for k = 1, 6 do
    if execution_check(dir[k], k) then
      edir[#edir + 1] = dir[k]
      local string = node_m:get_string("sparktech_energy_trig")
      node_m:set_string("sparktech_energy_trig", "" .. string:sub(1, k - 1) .. string:sub(k, k):upper() .. string:sub(k + 1, 6))
    else
      local string = node_m:get_string("sparktech_energy_trig")
      node_m:set_string("sparktech_energy_trig", "" .. string:sub(1, k - 1) .. string:sub(k, k):lower() .. string:sub(k + 1, 6))
    end
  end

  for _, k in pairs(edir) do
    local node_e = node_m:get_int("energy")
    local i = minetest.get_node(k)
    local i_m = minetest.get_meta(k)
    local i_e = i_m:get_int("energy")
    local i_con = minetest.get_item_group(i.name, "sparktech_energy_conductor")
    local i_in = minetest.get_item_group(i.name, "sparktech_energy_in")
    local i_out = minetest.get_item_group(i.name, "sparktech_energy_out")
    local i_max = minetest.get_item_group(i.name, "sparktech_energy_max")
    local node_r = node_e / node_max
    local i_r = i_e / i_max
    local trans_n = 0
    local trans_i = 0

    if node_con == 2 and i_con ~= 2 then
      trans_n = - node_e
      trans_i = node_e
    elseif i_con == 2 and node_con ~= 2 then
      trans_n = i_e
      trans_i = - i_e
    elseif i_con == 4 and node_con ~= 4 then
      trans_n = - node_e
      trans_i = node_e
    elseif node_con == 4 and i_con ~= 4 then
      trans_n = i_e
      trans_i = - i_e
    elseif node_con ~= 4 and i_con ~= 4 then
      local ch = math.ceil((node_max * i_e - i_max * node_e) / (node_max + i_max))
      trans_n = ch
      trans_i = -ch
    end

    if trans_n + node_e > node_max then
      local ch = trans_n - (node_max - node_e)
      trans_n = trans_n - ch
      trans_i = trans_i + ch
    end
    if trans_i + i_e > i_max then
      local ch = trans_i - (i_max - i_e)
      trans_n = trans_n + ch
      trans_i = trans_i - ch
    end

    i_m:set_int("energy", i_m:get_int("energy") + trans_i)
    node_m:set_int("energy", node_m:get_int("energy") + trans_n)
  end
end

minetest.register_abm({
	nodenames = {"group:sparktech_energy_conductor"},
	interval = 1.0,
  chance = 1,
  catch_up = true,
  action = function(pos, node, active_object_count, active_object_count_wider)
    validate(pos)
    energy_logic(node, pos)
  end
})

minetest.register_on_placenode(function(pos, newnode, placer, oldnode, itemstack, pointed_thing)
  if minetest.get_item_group(itemstack:get_name(), "sparktech_energy_storeonbreak") > 0 then
    local meta = minetest.get_meta(pos)
    meta:set_int("energy", itemstack:get_metadata() or 0)
  end
end)