smine

local m = peripheral.find("modem")
local senderID = os.getComputerLabel() == nil and "ID:" .. os.getComputerID() or os.getComputerLabel()
local channels = {
      ["stdout"] = 1000,
      ["stdin"] = 1001,
      ["witherout"] = 1010,
      ["witherin"] = 1011
    }
m.open(channels.stdin)
local ticks = 0

local function checkStop()
  if ticks % 4 == 0 then
    os.startTimer(0.15)
    local a, b, c, d, e
    repeat
      evt, face, sendCh, replyCh, msg, dist = os.pullEvent()
      if evt == "modem_message" and msg.type == "cmd" and msg.cmd == "sigterm" and (msg.receiver == nil or (type(msg.receiver) == "string" and string.match(senderID, msg.receiver))) then
        return true
      end
    until evt == "timer"
  end
  return false
end

local function tryRefuel()
  while turtle.getFuelLevel() < 1 do
    for i = 1, 16 do
      turtle.select(i)
      turtle.refuel(1)
      if turtle.getFuelLevel() > 0 then
        break
      end
    end
    turtle.select(1)
  end
end

local function forward()
  if checkStop() then
    error()
  end
  tryRefuel()
  while not turtle.forward() do
    sleep(.25)
    turtle.dig()
  end
end

while true do
  turtle.digDown()
  turtle.dig()
  turtle.digUp()
  forward()
end