Supply converter: demany only the needed power (#577)

Supply converter demands only the needed power to satisfy the demand on the output network. It can still be too much if the output network has other power sources, because supply is not taken in account.

This surplus of energy can be used to charge batteries.

Author: ZettaScript

technic/machines/supply_converter.lua

@@ -120,7 +120,7 @@ local run = function(pos, node, run_stage)
 		return
 	end
 
-	local remain = 0.9
+	local efficiency = 0.9
 	-- Machine information
 	local machine_name  = S("Supply Converter")
 	local meta          = minetest.get_meta(pos)
@@ -133,7 +133,6 @@ local run = function(pos, node, run_stage)
 		enabled = enabled == "1"
 	end
 	enabled = enabled and (meta:get_int("mesecon_mode") == 0 or meta:get_int("mesecon_effect") ~= 0)
-	local demand = enabled and meta:get_int("power") or 0
 
 	local pos_up        = {x=pos.x, y=pos.y+1, z=pos.z}
 	local pos_down      = {x=pos.x, y=pos.y-1, z=pos.z}
@@ -144,14 +143,36 @@ local run = function(pos, node, run_stage)
 	local to   = technic.get_cable_tier(name_down)
 
 	if from and to then
-		local input = meta:get_int(from.."_EU_input")
-		meta:set_int(from.."_EU_demand", demand)
-		meta:set_int(from.."_EU_supply", 0)
-		meta:set_int(to.."_EU_demand", 0)
-		meta:set_int(to.."_EU_supply", input * remain)
-		meta:set_string("infotext", S("@1 (@2 @3 -> @4 @5)", machine_name,
-			technic.EU_string(input), from,
-			technic.EU_string(input * remain), to))
+		-- Get the "to" network switching station for EU demand calculation
+		local network_hash = technic.cables[minetest.hash_node_position(pos_down)]
+		local network = network_hash and minetest.get_position_from_hash(network_hash)
+		local sw_pos = network and {x=network.x,y=network.y+1,z=network.z}
+		local timeout = 0
+		for tier in pairs(technic.machines) do
+			-- Supply converter must be connected to a network
+			timeout = math.max(meta:get_int(tier.."_EU_timeout"), timeout)
+		end
+		if timeout > 0 and sw_pos and minetest.get_node(sw_pos).name == "technic:switching_station" then
+			local sw_meta = minetest.get_meta(sw_pos)
+			local demand = 0
+			if enabled then
+				-- Reverse evaluate the required machine and round to a nice number
+				demand = 100 * math.ceil((sw_meta:get_int("demand") / efficiency) / 100)
+				-- Do not draw more than the limit
+				demand = math.min(demand, meta:get_int("power"))
+			end
+
+			local input = meta:get_int(from.."_EU_input") -- actual input
+			meta:set_int(from.."_EU_demand", demand) -- desired input
+			meta:set_int(from.."_EU_supply", 0)
+			meta:set_int(to.."_EU_demand", 0)
+			meta:set_int(to.."_EU_supply", input * efficiency)
+			meta:set_string("infotext", S("@1 (@2 @3 -> @4 @5)", machine_name,
+				technic.EU_string(input), from,
+				technic.EU_string(input * efficiency), to))
+		else
+			meta:set_string("infotext",S("%s Has No Network"):format(machine_name))
+		end
 	else
 		meta:set_string("infotext", S("%s Has Bad Cabling"):format(machine_name))
 		if to then