Hall Mine Left

shell.run('clear')
local arg1,arg2 = ...
local length = 0
local torch = false
local torchcount = 0
if (arg1 ~= nill) then
  length = arg1
end
if (arg2 ~= nill) then
  if (arg2 == "y") then
    torch = true
  end
end
local invalid = true

function checkFuel()
  if turtle.getFuelLevel() < 100 then
    shell.run("refuel","all")
  end
end

function mineTunnel()
  checkFuel()
  if turtle.detect() then
    repeat turtle.dig() until turtle.forward()
  else
    repeat until turtle.forward()
  end
  if turtle.detectDown() then turtle.digDown() end
  if (torch == true) then
    torchcount = torchcount + 1
    if (torchcount == 7) then
      turtle.select(1)
      turtle.placeDown()
      torchcount = 0
    end
  end
  while turtle.detectUp() do
    turtle.digUp()
    sleep(0.5)
  end
end

if (length == 0) then
  repeat
    print( "How many blocks to mine?" )
    length = tonumber(io.read())
    if (length == 0) then
      shell.run('clear')
      print( "Entry must be larger than " .. length .. ".")
      invalid = true
    end
    if (length > 0) then
      invalid = false
    end
  until invalid == false
end

shell.run('clear')
for i=1,3 do
    mineTunnel()
end
turtle.turnLeft()

for i=1,length do
    mineTunnel()
end

turtle.turnLeft()
for i=1,2 do
    mineTunnel()
end
turtle.turnLeft()
turtle.turnLeft()
turtle.forward()
turtle.forward()
for i=1,3 do
    mineTunnel()
end
turtle.turnRight()
torchcount = 0

for i=1,length do
    mineTunnel()
end
turtle.turnRight()
for i=1,2 do
    mineTunnel()
end
turtle.turnRight()
turtle.turnRight()
turtle.forward()
turtle.forward()