don't craft when return items don't fit in dst

see https://github.com/mt-mods/pipeworks/issues/61

fixes #61

autocrafter.lua

@@ -35,28 +35,62 @@ 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
+	local output_item = craft.output.item
+	-- check if we have enough room in dst for output item(s)
+	-- we'll check replacements later
 	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
+
+	-- since there is no inv:room_for_items() method, we use history/undo system
+	-- see: https://github.com/mt-mods/pipeworks/issues/61
+	-- keep track of stacks we add to dst inventory
+	local history = { output_item }
+	-- add the result into the dst inventory
+	inventory:add_item("dst", output_item)
+
+	-- add any "replacements" as well and keep track of what didn't fit
+	local leftover, replacement, undo, diff
+	for i = 1, 9 do
+		replacement = craft.decremented_input.items[i]
+		if not replacement:is_empty() then
+			leftover = inventory:add_item("dst", replacement)
+			if not leftover:is_empty() then
+				-- hold up, there isn't room, we need to undo
+				undo = true
+				-- adjust count (mostly is just 1) so diff will mostly be 0
+				diff = replacement:get_count() - leftover:get_count()
+				-- make a copy with adjusted count
+				replacement = ItemStack(replacement)
+				replacement:set_count(diff)
+			end
+			-- add to history what had fit
+			table.insert(history, replacement)
+			-- if not all fit, let's not make it worse
+			if undo then break end
+		end
+	end
+
+	if undo then
+		-- we need to remove what we put in dst
+		for _, stack in ipairs(history) do
+				inventory:remove_item("dst", stack)
+		end
+		return false
+	end
+
+	-- consume materials
 	for itemname, number in pairs(consumption) do
 		for _ = 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