Turtle Tunnel

--[[Fuel must be placed in slot 15, torches must be placed in slot 16.]]
-- Create the function for refueling
function checkFuel()
  if turtle.getFuelLevel() <= 20 then
        if turtle.getItemCount(15) == 0 then
    print("Out of fuel.")
    exit()
  else
   turtle.select(15)
          turtle.refuel(1)
          turtle.select(1)
end --if
end --if
end --checkFuel()

-- Create the turnAround function
function turnAround()
  turtle.turnRight()
  turtle.turnRight()
end --turnAround()

-- Digs the tunnel for the given length
function tunnel(givenLength)
  local torchDistance = 0
  for index = 1,givenLength do
    if turtle.detect() then
        repeat
            turtle.dig()
            sleep(0.50)
        until turtle.detect() == false
end --if
    turtle.forward()
    if turtle.detectUp() then
	repeat
	    turtle.digUp()
	    sleep(0.50)
	until turtle.detectUp() == false
end --if
    turtle.turnLeft()
    if turtle.detect() then
	repeat
	    turtle.dig()
	    sleep(0.50)
        until turtle.detect() == false
end --if
    turtle.up()
    if turtle.detect() then
	repeat
	    turtle.dig()
	    sleep(0.50)
	until turtle.detect() == false
end--if
    turtle.turnRight()
    turtle.turnRight()
    if turtle.detect() then
	repeat
	    turtle.dig()
	    sleep(0.50)
	until turtle.detect() == false
end
    turtle.down()
    if turtle.detect() then
	repeat
	    turtle.dig()
	    sleep(0.50)
	until turtle.detect() == false
end
    turtle.turnLeft()
torchDistance = torchDistance + 1
-- attempts to place a block below
        turtle.select(1)
        turtle.placeDown()
-- Places a torch every 9 blocks
        if torchDistance == 9 then
          print("Placing torch...")
   turtle.select(16)
          turnAround()
          turtle.place()
          turnAround()
          torchDistance = 0
          checkFuel()
        end --if
  end --for
-- Sends the turtle back to the start
        turtle.up()
turnAround()
        for index = 1,givenLength do
          checkFuel()
   if not turtle.detect() then
  turtle.forward()
          else
         repeat
        turtle.dig()
           turtle.sleep(0.25)
  until turtle.detect() == false
  turtle.forward()
          end --if
        end --for
        turtle.down()
turnAround()
end --tunnel()

-- Main script
print("Input tunnel length:")
local length = read()
print("Starting excavation...")
checkFuel()
tunnel(length)
term.clear()
print("The tunnel has been excavated!")