use nodetimers instead of abm's to run the autocrafters; only run autocrafters when needed

autocrafters will stop() when theres no valid recipe, no dst space or enough src material
it will resume again on inventory or recipe changes

autocrafter.lua

@@ -2,48 +2,106 @@ local autocrafterCache = {}  -- caches some recipe data to avoid to call the slo
 
 local function count_index(invlist)
 	local index = {}
-	for _, stack in ipairs(invlist) do
+	for _, stack in pairs(invlist) do
-		local stack_name = stack:get_name()
+		if not stack:is_empty() then
-		index[stack_name] = (index[stack_name] or 0) + stack:get_count()
+			local stack_name = stack:get_name()
+			index[stack_name] = (index[stack_name] or 0) + stack:get_count()
+		end
 	end
 	return index
 end
 
-local function get_cached_craft(pos)
+local function get_craft(pos, inventory, hash)
-	local hash = minetest.hash_node_position(pos)
+	local hash = hash or minetest.hash_node_position(pos)
-	return hash, autocrafterCache[hash]
+	local craft = autocrafterCache[hash]
+	if not craft then
+		if inventory:is_empty("recipe") then return nil end
+		local recipe = inventory:get_list("recipe")
+		local output, decremented_input = minetest.get_craft_result({method = "normal", width = 3, items = recipe})
+		craft = {recipe = recipe, consumption=count_index(recipe), output = output, decremented_input = decremented_input}
+		autocrafterCache[hash] = craft
+
+	end
+	-- only return crafts that have an actual result
+	if not craft.output.item:is_empty() then
+		return craft
+	end
 end
 
 -- note, that this function assumes allready being updated to virtual items
 -- and doesn't handle recipes with stacksizes > 1
 local function on_recipe_change(pos, inventory)
-	if not inventory then return end
+	-- if we emptied the grid, there's no point in keeping it running or cached
-	local recipe = inventory:get_list("recipe")
+	if inventory:is_empty("recipe") then
-	if not recipe then return end
+		minetest.get_node_timer(pos):stop()
-
+		autocrafterCache[minetest.hash_node_position(pos)] = nil
+		return
+	end
 	local recipe_changed = false
-	local hash, craft = get_cached_craft(pos)
+	local recipe = inventory:get_list("recipe")
 
-	if not craft then
+	local hash = minetest.hash_node_position(pos)
-		recipe_changed = true
+	local craft = autocrafterCache[hash]
-	else
+
+	if craft then
 		-- check if it changed
-		local cached_recipe =  craft.recipe
+		local cached_recipe = craft.recipe
 		for i = 1, 9 do
 			if recipe[i]:get_name() ~= cached_recipe[i]:get_name() then
-				recipe_changed = true
+				autocrafterCache[hash] = nil -- invalidate recipe
+				craft = nil
 				break
 			end
 		end
 	end
 
-	if recipe_changed then
+	local timer = minetest.get_node_timer(pos)
-		local output, decremented_input = minetest.get_craft_result({method = "normal", width = 3, items = recipe})
+	if not timer:is_started() then
-		craft = {recipe = recipe, consumption=count_index(recipe), output = output, decremented_input = decremented_input}
+		timer:start(1)
-		autocrafterCache[hash] = craft
+	end
+end
+
+local function on_inventory_change(pos, inventory)
+	local timer = minetest.get_node_timer(pos)
+	if not timer:is_started() then
+		timer:start(1)
+	end
+end
+
+local function autocraft(inventory, craft)
+	if not craft then return false end
+	local output_item = craft.output.item
+
+	-- check if we have enough room in dst
+	if not inventory:room_for_item("dst", output_item) then return false end
+	local consumption = craft.consumption
+	local inv_index = count_index(inventory:get_list("src"))
+	-- check if we have enough material available
+	for itemname, number in pairs(consumption) do
+		if (not inv_index[itemname]) or inv_index[itemname] < number then return false end
+	end
+	-- consume material
+	for itemname, number in pairs(consumption) do
+		for i = 1, number do -- We have to do that since remove_item does not work if count > stack_max
+			inventory:remove_item("src", ItemStack(itemname))
+		end
 	end
 
-	return craft
+	-- craft the result into the dst inventory and add any "replacements" as well
+	inventory:add_item("dst", output_item)
+	for i = 1, 9 do
+		inventory:add_item("dst", craft.decremented_input.items[i])
+	end
+	return true
+end
+
+-- returns false to stop the timer, true to continue running
+-- is started only from start_autocrafter(pos) after sanity checks and cached recipe
+local function run_autocrafter(pos, elapsed)
+	local meta = minetest.get_meta(pos)
+	local inventory = meta:get_inventory()
+	local craft = get_craft(pos, inventory)
+	return autocraft(inventory, craft)
 end
 
 local function update_autocrafter(pos)
@@ -61,51 +119,6 @@ local function update_autocrafter(pos)
 	end
 end
 
-local function autocraft(inventory, craft)
-	local output_item = craft.output.item
-	-- check if we have enough room in dst
-	if not inventory:room_for_item("dst", output_item) then return false end
-
-	local consumption = craft.consumption
-	local inv_index = count_index(inventory:get_list("src"))
-	-- check if we have enough materials available
-	for itemname, number in pairs(consumption) do
-		if (not inv_index[itemname]) or inv_index[itemname] < number then return false end
-	end
-
-	-- consume materials
-	for itemname, number in pairs(consumption) do
-		for i = 1, number do -- We have to do that since remove_item does not work if count > stack_max
-			inventory:remove_item("src", ItemStack(itemname))
-		end
-	end
-
-	-- craft the result into the dst inventory and add any "replacements" as well
-	inventory:add_item("dst", output_item)
-	for i = 1, 9 do
-		inventory:add_item("dst", craft.decremented_input.items[i])
-	end
-	return true
-end
-
-local function run_autocrafter(inventory, pos)
-	if not inventory then return end
-	local recipe = inventory:get_list("recipe")
-	if not recipe then return end
-
-	local _, craft = get_cached_craft(pos)
-	if craft == nil then
-		update_autocrafter(pos) -- only does some unnecessary calls for "old" autocrafters
-		craft = on_recipe_change(pos, inventory)
-	end
-
-	-- skip crafts that have no output
-	local output_item = craft.output.item
-	if output_item:is_empty() then return end
-
-	autocraft(inventory, craft)
-end
-
 minetest.register_node("pipeworks:autocrafter", {
 	description = "Autocrafter", 
 	drawtype = "normal", 
@@ -114,7 +127,9 @@ minetest.register_node("pipeworks:autocrafter", {
 	tube = {insert_object = function(pos, node, stack, direction)
 			local meta = minetest.get_meta(pos)
 			local inv = meta:get_inventory()
-			return inv:add_item("src", stack)
+			local added = inv:add_item("src", stack)
+			on_inventory_change(pos, inv)
+			return added
 		end, 
 		can_insert = function(pos, node, stack, direction)
 			local meta = minetest.get_meta(pos)
@@ -162,6 +177,7 @@ minetest.register_node("pipeworks:autocrafter", {
 			on_recipe_change(pos, inv)
 			return 0
 		else
+			on_inventory_change(pos, inv)
 			return stack:get_count()
 		end
 	end,
@@ -173,6 +189,7 @@ minetest.register_node("pipeworks:autocrafter", {
 			on_recipe_change(pos, inv)
 			return 0
 		else
+			on_inventory_change(pos, inv)
 			return stack:get_count()
 		end
 	end,
@@ -192,15 +209,9 @@ minetest.register_node("pipeworks:autocrafter", {
 			on_recipe_change(pos, inv)
 			return 0
 		else
+			on_inventory_change(pos, inv)
 			return stack:get_count()
 		end
 	end,
-})
+	on_timer = run_autocrafter
-
-minetest.register_abm({nodenames = {"pipeworks:autocrafter"}, interval = 1, chance = 1, 
-			action = function(pos, node)
-				local meta = minetest.get_meta(pos)
-				local inv = meta:get_inventory()
-				run_autocrafter(inv, pos)
-			end
 })