Harvest Cactus 0_2

-- ######################################
-- harvest cactus
-- version 0.2
-- http://hevohevo.hatenablog.com/

-- Turtle goes forward and harvests cactuses basically.
-- When he reaches an order block, run the order; stop, turn right, turn left.

-- I recommend that this program names "startup".

-- ############### Side View
--   T: Trutle, C: Cactus
-- T=> C
--     C
--     C

-- ############### Top View:
--   T: Trutle, C: Cactus, S: Block for stopping(e.g. a chest),
--   R: Block for turning right, L: Block for turning left

-- R   R
--    R   R
-- C C C C
-- C C C C
-- C C C C
-- C C C C
--
--ST
--      LR
--   L

-- Config
BLOCK_TURN_LEFT = 13
BLOCK_TURN_RIGHT = 14
BLOCK_STOP = 15
FUEL = 16

MIN_FUEL_LEVEL = 100
SLEEP_TIME = 600 -- seconds

function get_cactus()
  turtle.select(1)
  turtle.forward()
  turtle.suck()
  turtle.dig()
  turtle.digDown()
end

while true do
  repeat   -- start
    get_cactus()
    turtle.select(BLOCK_TURN_RIGHT)
    if turtle.compare() then turtle.turnRight() end

    turtle.select(BLOCK_TURN_LEFT)
    if turtle.compare() then turtle.turnLeft() end

    turtle.select(BLOCK_STOP)
  until turtle.compare()    -- end

  -- drop cactus to the chest
  for i=1,12 do
    turtle.select(i)
    if not turtle.drop() then break end
  end

  turtle.turnRight()
  os.sleep(SLEEP_TIME)
end