local function move(f)
    if turtle.getFuelLevel() == 0 then
        for slot=1,16 do
            turtle.select(slot)
            if turtle.refuel(0) then
                turtle.refuel(1)
                break
            end
        end
        if turtle.getFuelLevel() == 0 then
            print("No fuel, stopping...")
            return false
        end
    end
    -- mooooooveeee soooooo4aaaaraaa
    while not f() do
      turtle.dig()
      turtle.attack()
      sleep(1)
    end
end

-- return true if item count in slot 2 == 64
local function refill2()
  local cobbleCount = turtle.getItemCount(2)
  local refillCount = 64 - cobbleCount
  if (cobbleCount == 0) then
        print("Out of tunnel buildblock: place buildblock in slot 2 to continue")
        repeat
            sleep(1)
        until (turtle.getItemCount(2) > 0)
  else
    for n = 3,16 do
      turtle.select(2)
      if (turtle.compareTo(n) == true) then
                turtle.select(n)
                if (refillCount > turtle.getItemCount(n)) then
                    turtle.transferTo(2, turtle.getItemCount(n))
                    refillCount = 64 - turtle.getItemCount(2)
                else
                    turtle.transferTo(2, refillCount)
                    break
                end
       end
    end
  end
  return turtle.getItemCount(2) == 64
end


local function place()
  if not turtle.detect() then
    refill2()
    turtle.select(2)
    turtle.place()
    return true
  end
  return false
end


local function placeUp()
  if not turtle.detectUp() then
    refill2()
    turtle.select(2)
    turtle.placeUp()
    return true
  end
  return false
end


local function placeDown()
  if not turtle.detectDown() then
    refill2()
    turtle.select(2)
    turtle.placeDown()
    return true
  end
  return false
end


function emptyStash()
    for slot=3,16 do
        inSlot = turtle.getItemDetail(slot)
        if inSlot.name == "minecraft:cobblestone" then
            turtle.select(slot)
            turtle.drop()
        end
    end
end


local function dig()
    while turtle.detect() do
        turtle.dig()
    end
end


local function digUp()
    while turtle.detectUp() do
        turtle.digUp()
    end
end

-- 1 floor step
local function step1()
  dig()
  move(turtle.forward)
  placeDown()
end

-- 2 floor step
local function step2()
  dig()
  move(turtle.forward)
  placeUp()
end


local function placeTorch()
  turtle.select(1)
  if turtle.getItemCount() < 1 then
    print("No torches in slot 1, place torches in slot 1")
    return false
  end
  turtle.turnRight()
  turtle.place()
  turtle.turnLeft()
  return true
end


-- MAIN
local args = { ... }
local length = 0
local width = 3
local depth = 0

if #args < 1 then
  print( "Usage: tunnel <length> [width, default 3]" )
  return
else
  length = tonumber( args[1] )
  if length < 1 then
    print( "Tunnel length must be > 0" )
    return
  end
end

if #args > 1 then
  width = tonumber( args[2] )
  if width < 1 then
    print( "Tunnel width must be > 0" )
    return
  end
end

print( "Tunnelling: length="..length.." width="..width.." height=2" )

for i=1,length do
  step1(false)

  turtle.turnRight()

  for j=2,width do
    step1()
    if (i % 7 == 0) and (j % 7 == 0) then
      placeTorch()
    end
  end

  place()
  digUp()
  move(turtle.up)
  place()
  placeUp()

  turtle.turnRight()
  turtle.turnRight()

  for j=2,width do
    step2()
  end

  place()
  move(turtle.down)
  place()
  turtle.turnRight()

  if (i == 2) or (i % 7 == 0) then
    placeTorch()
  end

  depth = depth + 1

  if refill2() then
    emptyStash()
  end
end

print( "Returning to start..." )

-- Return to where we started
turtle.turnLeft()
turtle.turnLeft()
while depth > 0 do
  move(turtle.forward)
  depth = depth - 1
end
turtle.turnRight()
turtle.turnRight()

print( "Tunnel complete." )