minetest-mod-sparktech/sparkcore/lua/energy_distrib.lua

local function round(x)
  if x >= 0 then
    return math.floor(x+0.5)
  else
    return math.ceil(x-0.5)
  end
end

local function wakeup(pos,share)
	--called to test if a node needs to be woken up
	local node = minetest.get_node(pos)
	if (minetest.get_item_group(node.name, "sparktech_energy_wakeup") >= 1) then
		local ntype = minetest.get_item_group(node.name, "spaktech_energy_type")
		local meta = minetest.get_meta(pos)
		local energy = meta:get_int("energy")
		if (energy == share) then return end -- only makes sense if we actually change the energy in the block
		if ntype == 2 then
			if energy == 0 then
				minetest.get_node_timer(pos):start(0.5)
			end
		elseif ntype == 4 then
			if minetest.get_item_group(node.name, "sparktech_energy_wakeup") == energy then -- set the value to when you want to be woken up key
				minetest.get_node_timer(pos):start(0.5)
			end
		end
	end
end

-- internal var net_master stores all slave nodes
-- sparktech_net_passive = are used to follow nets, do not count towards energy
-- sparktech_net_trigger = trigger updates
-- Updates blocks every seconds

local function net_get_slaves(master)
   local slaves = {}
   local meta = minetest.get_meta(master)
   local slave_s = meta:get_string("net_master")
   slave_s = string.sub(slave_s, 2)
   local slave_s_dict = string.split(slave_s, "|")
   for _, val in pairs(slave_s_dict) do
      local cor = string.split(val, ":")
      slaves[#slaves + 1] = { x=tonumber(cor[1]), y=tonumber(cor[2]), z=tonumber(cor[3])}
   end
   return slaves
end

local function net_distribute(pos)
  -- sparktech_energy_type types:
  --   2 - Producer (gets emptied)
  --   3 - Storage  (backup / overflow)
  --   4 - Consumer (gets filled)
  
  local nodes = net_get_slaves(pos)
  nodes[#nodes +1] = pos
  -- all nodes are in local now

  -- Gather all information we need for the three node types
  local energy_pr = 0
  local energy_st = 0
  local energy_co = 0
  local max_energy_pr = 0
  local max_energy_st = 0
  local max_energy_co = 0
  for x = 1, #nodes do
    local ntype = minetest.get_item_group(minetest.get_node(nodes[x]).name, "sparktech_energy_type")
    local nenergy = minetest.get_meta(nodes[x]):get_int("energy")
    local nenergy_max = minetest.get_item_group(minetest.get_node(nodes[x]).name, "sparktech_energy_max")
    if ntype == 2 then
      energy_pr = energy_pr + nenergy
      max_energy_pr = max_energy_pr + nenergy_max
    elseif ntype == 3 then
      energy_st = energy_st + nenergy
      max_energy_st = max_energy_st + nenergy_max
    elseif ntype == 4 then
      energy_co = energy_co + nenergy
      max_energy_co = max_energy_co + nenergy_max
    end
  end
  
  -- now we know all energy in the system, now to distribute it

  local pr_new = energy_pr
  local st_new = energy_st
  local co_new = energy_co

  -- How much energy is available to be put into storage / is missing to fill up the consumers
  local prod_buf = energy_pr - (max_energy_co - energy_co)

  -- Producers -> Consumers transfer
  if prod_buf >= 0 then
    -- Fill up the consumers to their limit
    pr_new = prod_buf
    co_new = co_new + (energy_pr - prod_buf)
  else
    -- Empty the producers into the consumers
    pr_new = 0
    co_new = co_new + energy_pr
  end

  -- Storage -> Consumers and Producers -> Storage transfers
  if prod_buf < 0 then
    -- Fill up the consumers with energy in storage
    local sto_buf = energy_st + prod_buf
    if sto_buf >= 0 then
      st_new = sto_buf
      co_new = co_new + energy_st - sto_buf
    else
      st_new = 0
      co_new = co_new + energy_st
    end
  else
    -- Store excess energy into storage
    local st_cap = max_energy_st - energy_st
    if st_cap >= prod_buf then
      pr_new = 0
      st_new = st_new + prod_buf
    else
      pr_new = prod_buf - st_cap
      st_new = st_new + st_cap
    end
  end 

  -- Now the new energy distribution is known

  -- Apply the later to be improved (maybe) share system to all node types
	local share_pr = pr_new / max_energy_pr;
	local share_st = st_new / max_energy_st;
	local share_co = co_new / max_energy_co;
	for x = 1, #nodes do
		local meta = minetest.get_meta(nodes[x])
		local node = minetest.get_node(nodes[x])
		local ntype = minetest.get_item_group(node.name, "sparktech_energy_type")
		local nmax = minetest.get_item_group(node.name, "sparktech_energy_max")
		if ntype == 2 then --produces
			wakeup(nodes[x], round(share_pr * nmax)) -- TODO: test this
			meta:set_int("energy", round(share_pr * nmax))
		elseif ntype == 3 then --stores
			meta:set_int("energy", round(share_st * nmax))
		elseif ntype == 4 then --consumes
			wakeup(nodes[x], round(share_co * nmax))
			meta:set_int("energy", round(share_co * nmax))
		end
	end
end

local function filter(pos)-- function is called severall times, only run if this is a master node
  local meta = minetest.get_meta(pos)
  local net_master = meta:get_string("net_master")
  if (net_master == nil or net_master == "") then -- if it is not set this is NOT a master node, so we can ignore it eh
    return
  else
    net_distribute(pos)
  end
end		

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