ComputerCraft: right-hand farming0_1

-- #############################
-- Right-hand Farming
-- version 0.1
-- http://hevohevo.hatenablog.com/

-- Features:
-- - Implements Right-hand Maze algorithm
-- - Requires redstone signal for detecting right side wall
-- - Turtle can restart from the last interruption, if this program's name is "startup"

-- TOP View(o: millets,  R: redstone signal, T: Home position)
-- RRRRRRRRRR
-- RooRooRooR
-- RooRooRooR
-- RooRooRooR
-- RooRooRooR
-- R        R
-- RRRRRRRRTR
--        RRR

-- config
MIN_FUEL_LEVEL = 1000
SLEEP_TIME = 300
-- functions
function count_items()
  local sum = 0
  for i=1,16 do
    sum = sum + turtle.getItemCount(i)
  end
  return sum
end

function drop_all()
  for i=1,16 do
    turtle.select(i)
    turtle.dropUp()
  end
  turtle.select(1)
end

function fwd_and_dig()
  if rs.getInput("front") then return end
  turtle.dig()
  turtle.forward()
  turtle.digDown()
end


function get_fuel()
  if turtle.getFuelLevel() < MIN_FUEL_LEVEL then
    turtle.suck()
    turtle.refuel()
    if turtle.getFuelLevel() < MIN_FUEL_LEVEL then
      error("More fuel!")
    end
  end
end

-- main
turtle.select(1)

while true do
while true do
  -- Home Position
  if turtle.detectUp() and count_items() > 0 then
    print('drop')
    drop_all()
    get_fuel()
    turtle.turnRight()
    turtle.turnRight()
    os.sleep(SLEEP_TIME)
    fwd_and_dig()
    break
  end

  if not rs.getInput("right") then
    turtle.turnRight()
    fwd_and_dig()
    break
  end

  if rs.getInput("front") then
    turtle.turnLeft()
    fwd_and_dig()
    break
  end

  fwd_and_dig()
end
end