minetest-mod-sparktech/sparkmachine/lua/metalfurnace.lua

local NAME = minetest.get_current_modname()
local MAX_ENERGY = 300
local modifier = 10 -- Cooking cost modifier
local time_modifier = 1.5 -- Cooking time modifier

local formspec = sparktech.add_inventory(6,1.5,
	"list[current_name;source;0,0;2,1;]" ..
	"list[current_name;product;7.5,0;2,1;]")

local function is_smeltable(items)
	local cooked
	local aftercooked
	cooked, aftercooked = minetest.get_craft_result({method = "cooking", width = 1, items = items})
	return cooked.time ~= 0
end

local function is_item_allowed(pos, target, _, stack)
	if target ~= "source" then return 0 end --so no items get moved into the produce inventory by the user

	if stack == nil or not is_smeltable({stack}) then --invalid or unsmeltable items dont get in
		return 0
	else
		return stack:get_count()
	end
end

local function is_item_allowed_move(pos, src, sidx, target, tidx, c, p)
	local meta = minetest.get_meta(pos)
	local inv = meta:get_inventory()
	local stack = inv:get_stack(src, sidx)
	return is_item_allowed(pos, target, tidx, stack, p)
end

local function ongetitem(pos)
	local meta = minetest.get_meta(pos)
	if meta:get_int("energy") < modifier then return end
	local timer = minetest.get_node_timer(pos)
	timer:start(1.0)
end

local function update_formspec(pos)
  local meta = minetest.get_meta(pos)
  	local inventory = meta:get_inventory()
	local cfmsp = formspec

	local energy = meta:get_int("energy")
	
	cfmsp = cfmsp ..
	  sparktech.makebar("energy2.png", 0, 1.125, 9.75, 0.25,
			    energy, minetest.get_item_group(MAX_ENERGY)
			    , 0)

	for item=0, 1 do
	  local cooked
	  local aftercooked
	  local progress = meta:get_int("progress_" .. (item+1))	
	  cooked, aftercooked = minetest.get_craft_result({method = "cooking", width = 1, items = {inventory:get_stack("source", (item +1))}})
	  
	  cfmsp = cfmsp ..
	    sparktech.makebar("progress2.png", item * 1.25, 0, 1, 1,
			      progress, math.ceil(cooked.time * time_modifier), 0)
	end
	
	meta:set_string("formspec", cfmsp)
end

local function mytime(pos, elapsed)
	local meta = minetest.get_meta(pos)
	local energy = meta:get_int("energy")
	local inventory = meta:get_inventory()
	local source = inventory:get_list("source")
	local product = inventory:get_list("product")

	for item=1,2 do
		if energy >= modifier then
			local cooked
			local aftercooked
			local progress = meta:get_int("progress_" .. item)
			cooked, aftercooked = minetest.get_craft_result({method = "cooking", width = 1, items = {inventory:get_stack("source", item)}})
			--source and product assigned
			if progress >= math.ceil(cooked.time * time_modifier) then
				if inventory:room_for_item("product", cooked.item) then
					inventory:add_item("product", cooked.item)
					inventory:set_stack("source", item, aftercooked.items[1])
					meta:set_int("progress_" .. item, 0)
				end
			else
				meta:set_int("progress_" .. item, progress + 1)
				energy = energy - modifier
			end
		end
	end

	meta:set_int("energy", energy)
	
	update_formspec(pos) -- Later this should only be done when a player looks into the block
	
	--TODO: for the formspec code, if it is marked as active update it here
	local has_items = false -- Keep updating if there are still items
	for _, e in pairs(meta:get_inventory():get_list("source")) do
		has_items = has_items or not e:is_empty()
	end
	if has_items then
		minetest.get_node_timer(pos):start(1.0) -- it was determined that a new cycle is required, this is the case if energy and material to cook is available
	end
	return
end

local function maytake(pos, listname, index, stack, player)
	local meta = minetest.get_meta(pos)
	if listname == "product" then 
		return tonumber(stack:get_count()) --sure, take the stuff that the furnace has cooked for you :D
	end
	-- TODO: code to stop people from taking halfcooked items, they'd burn their fingers
end

minetest.register_node( NAME .. ":lv_furnace", {
	description = "Electric furnace",

	tiles = {
		NAME .. "_steel_sideplate.png",
		NAME .. "_steel_sideplate.png",
		NAME .. "_steel_sideplate.png",
		NAME .. "_steel_sideplate.png",
		NAME .. "_steel_backplate.png",
		NAME .. "_furnace_frontplate.png"
	},
	paramtype2 = "facedir",

	groups = {
		sparktech_techy = WRENCHABLE,
		sparktech_energy_type = ENERGY_CONSUMER,
		sparktech_net_trigger = TRUE,
		sparktech_energy_max = MAX_ENERGY,
		sparktech_energy_wakeup = 10
	},

	on_timer = mytime, -- add a mytimer function
	 allow_metadata_inventory_take = maytake,

	--on_righclick = function(pos, node, player, itemstack, pointed_thing)
	--TODO show formspec here, and store that a formspec is open in meta, the mytimer function schould update the formspec if it is open, recievefields schould mark it as closed

	--end,

	on_construct = function(pos, placer)
	  local meta = minetest.get_meta(pos)
	  meta:set_string("formspec",formspec) --gonna replace this with crafting the formspec on rightclick instead
	  local inventory = meta:get_inventory()
	  inventory:set_size('source',2)
	  inventory:set_size('product',2)
	end,

	on_rightclick = function(pos, clicker) -- Requires Version >0.4.16 to trigger because a custom formspec is set
	  return false
	end,

	allow_metadata_inventory_put = is_item_allowed,
	allow_metadata_inventory_move = is_item_allowed_move,
	allow_metadata_inventory_take = function(_, _, _, stack) return stack:get_count() end, -- Might want to improve this
	--on_metadata_inventory_move = ongetitem, --doesnt seem necesarry to me, if the item moves in the inventory schould not change the cooking process
	on_metadata_inventory_put = ongetitem
})