MC refuel

-- refuel_all.lua
-- Consumes all fuel items in inventory until full.

local function isNumber(x) return type(x) == "number" end

local limit = turtle.getFuelLimit()
if not isNumber(limit) then
  print("Fuel is unlimited/disabled on this server. Nothing to do.")
  return
end

local before = turtle.getFuelLevel()

for slot = 1, 16 do
  turtle.select(slot)
  -- Consume items one-by-one so we stop cleanly when full or item isn't fuel.
  while turtle.getItemCount() > 0 do
    local ok = turtle.refuel(1) -- tries to burn a single item
    if not ok then break end
    local lvl = turtle.getFuelLevel()
    if isNumber(lvl) and lvl >= limit then
      break
    end
  end
end

turtle.select(1)
local after = turtle.getFuelLevel()
if isNumber(before) and isNumber(after) then
  print(string.format("Refueled: %d -> %d  (Δ=%d)", before, after, after - before))
else
  print("Refuel complete.")
end