ComputerCraft: block_program

-- Turtle always keeps moving forward.
-- You can program physically by setting some blocks!
local max_step = 10 -- for your safety
local min_fuel_level = 1000 -- maintain this minimum fuel levels
local sleep_time = 10 -- define "os.sleep(sleep_time)" in your block_ruls
local wait_time = 1 -- wait [wait_time] seconds for each step

-- define your block_rules. Turtle can't braek these blocks.
local front_rule = {}
front_rule["minecraft:cobblestone"] = turtle.turnRight
front_rule["minecraft:stonebrick"] = turtle.turnLeft
front_rule["minecraft:stone_brick_stairs"] = turtle.up
front_rule["minecraft:stone_stairs"] = turtle.down -- cobblestone stairs
front_rule["minecraft:chest"] = os.shutdown

local top_rule = {}
top_rule["minecraft:glass"] = function() os.sleep(sleep_time) end
top_rule["minecraft:chest"] = function()
  while turtle.suckUp(1) and (turtle.getFuelLevel() < min_fuel_level) do
    if turtle.getFuelLevel() < min_fuel_level then os.shutdown() end  -- the fuel level is low, and shutdown
  end
end

local bottom_rule = {}
bottom_rule["minecraft:glass"] = function() os.sleep(sleep_time) end
bottom_rule["minecraft:chest"] = function()
  for i=16,1,-1 do
    turtle.select(i)
    local success, msg = turtle.dropDown()
    if not(success) and string.find(msg, "space") then os.shutdown() end -- the chest is full, and shutdown
  end
end

-- sub functions
function get_func(inspect_func, rule)
  inspect_func = inspect_func or turtle.inspect
  local success, info = inspect_func()
  local bname = info["name"]
  if success then
    return rule[ bname ], bname
  else
    return nil
  end
end

function exec_func(inspect_func, rule)
  local func, bname = get_func(inspect_func, rule)
  if func then
    print("  ",bname)
    return func()
  end
  return nil
end

function safe_dig(dig_func, inspect_func, rule)
  if get_func(inspect_func, rule) then
    print("decline to dig"); return false
  else
    local success, msg = dig_func()
    print("  dig ->",success,"(",msg,")")
    return success, msg
  end
end

function go_fwd() -- dig the top,bottom,front. and go forward.
  while safe_dig(turtle.digUp, turtle.inspectUp, top_rule) do os.sleep() end -- prepare for a sand or a gravel
  safe_dig(turtle.digDown, turtle.inspectDown, bottom_rule)
  while safe_dig(turtle.dig, turtle.inspect, front_rule) do os.sleep() end -- prepare for a sand or a gravel
  return turtle.forward()
end

-- Main
turtle.select(1)
for step=1,max_step do
  print(step,":")
  print(" -top"); exec_func(turtle.inspectUp, top_rule)
  print(" -bottom"); exec_func(turtle.inspectDown, bottom_rule)
  print(" -front"); exec_func(turtle.inspect, front_rule)
  go_fwd()
  os.sleep(wait_time)
end