Mining

function refuel(quantity)
 for i1 = 1, 16, 1 do
  turtle.select(i1)
  if turtle.refuel(quantity) then
   break
  else
   if i1==16 then
    return true
   end
  end
 end
 turtle.select(1)
end

function checkfuelstart()
 print ("Checking Fuel Level...")
 fuelpre = turtle.getFuelLevel()
 if fuelpre < 5 then
  print ("Fuel low, trying to refuel...")
  refuel(1)
 else
  print ("Fuel alright!")
 end
 fuelpost = turtle.getFuelLevel()
 if fuelpost==fuelpre then
  print ("There's no fuel in my inventory")
  print ("or my Fuel is below 5!")
  print ("Anyways, trying to move on...")
  if turtle.getFuelLevel()==0 then
   print("No Fuel left. Please refill!")
   return true
  end
 else
  print ("Fuel Level:")
  print (fuelpost)
  print ("Fuel Checking done!")
  return false
  end
end

function checkfuel()
 fuelpre1 = turtle.getFuelLevel()
 if turtle.getFuelLevel()<5 then
  if refuel(1) then
   turtle.select(1)
   term.clear()
   term.setCursorPos(1,1)
   print("No Fuel anymore! Aborted.")
   error()
  end
 end
 fuelpost1 = turtle.getFuelLevel()
 if fuelpost==fuelpre then
  if turtle.getFuelLevel()<5 then
   return true
  end
 else
 return false
 end
end

function torch()
 turtle.turnRight()
 turtle.turnRight()
 turtle.select(16)
 turtle.place()
 turtle.select(1)
 turtle.turnLeft()
 turtle.turnLeft()
end

print ("Starting up...")
sleep(0.5)
counter = 0
print ("How far shall I dig(Integer)?")
length = read()
completestring = "Alright, digging ".. length .. " blocks!"
print (completestring)
print ("Shall I place torches(y/n)?")
state = read()
if state=="y" then
 state=true
 print ("Alright, placing torches!")
else
 state=false
 print ("Alright, not placing torches!")
end
if checkfuelstart() then
 turtle.select(1)
 term.clear()
 term.setCursorPos(1,1)
 print("No Fuel. Aborted.")
 error()
else
if state then
 torch()
end
 for i = 1, length, 1 do
 counter = counter+1
 if counter==10 then
  counter = 0
  if state then
   torch()
  end
 end
  if math.fmod(i, 2)==0 then
   if checkfuel() then
    turtle.select(1)
    term.clear()
    term.setCursorPos(1,1)
    print("No Fuel. Aborted.")
    error()
   end
  end
  while turtle.placeDown() do
   if turtle.getItemCount(1)==0 then
     turtle.select(2)
     turtle.transferTo(1,64)
     turtle.select(1)
   end
   turtle.placeDown()
   sleep(0.8)
  end
  while turtle.detect() do
   turtle.dig()
   sleep(0.6)
  end
  while turtle.detectUp() do
   turtle.digUp()
   sleep(0.2)
  end
  turtle.forward()
  turtle.digUp()
 end
 turtle.select(1)
 term.clear()
 term.setCursorPos(1,1)
 print("Turtle stopped. Done.")
end