ComputerCraft: auto_refuel_0_2

-- #########################################
-- auto refuel
-- version 0.2
-- http://hevohevo.hatenablog.com/

-- You should prepare many many fuel items for the lovely turtle.
-- By default setting (in CC1.6):
--  Turtle FuelLimit is 10000 (e.g., 125 charcoal)
--  Advanced Turtle FuelLimit is 100000 (e.g., 1250 charcoal)

-- #############################
-- Config
local suck = turtle.suckDown
local drop = turtle.dropDown

-- #############################
-- Functions

function myRefuel(goal_level)
  local old_level = turtle.getFuelLevel()
  turtle.refuel(1)
  local new_level = turtle.getFuelLevel()
  if new_level < goal_level then
    local goal_num = (goal_level - new_level)/(new_level - old_level)
    if  goal_num > 0 and goal_num <= turtle.getItemCount(turtle.getSelectedSlot()) then
      turtle.refuel(math.floor(goal_num))
      if turtle.getFuelLevel() < goal_level then turtle.refuel(1) end
    else
      turtle.refuel()
    end
  end
end

function dropAll()
  for i=1,16 do
    if turtle.getItemCount(i) > 0 then
      turtle.select(i)
      drop()
    end
  end
end

-- include({1,2,3}, 2) => true
function include(tbl, elem)
  for k,v in pairs(tbl) do
    if elem == v then return true end
  end
  return false
end

-- #############################
-- main
local limit_level = turtle.getFuelLimit()

-- see ComputerCraft.cfg
if not limit_level or limit_level == 0 then
  error("no FuelLimit")
end

local args = {...}
local goal_level = limit_level

if #args == 0 then
  print("FuelLimit is ",limit_level)
  print(turtle.getFuelLevel(),'/',limit_level)
  while true do
    write("\nReally? (y/n): ")
    local str = read()
    if include({"n", "N","no","No","NO"}, str)then
      error("terminated")
    elseif include({"y", "Y","yes","YES","Yes"}, str) then
      break
    end
  end
else
  goal_level = tonumber(args[1])
  if goal_level > limit_level then
    error("Fuel Limit is "..limit_level)
  end
end

turtle.select(1)
while (goal_level > turtle.getFuelLevel()) and suck() do
  myRefuel(goal_level)
  print(turtle.getFuelLevel(), '/' , goal_level)
end
print(turtle.getFuelLevel(), '/' , goal_level)
dropAll()