Build Bridge

i=1
turtle.select(i)
while true do
 if turtle.getItemCount(i)==0 then
   i=i+1
   turtle.select(i)
  end
 if i==17 then
  turtle.reboot()
 end
 if turtle.detectUp() == true then
  turtle.digUp()
  else
   if  turtle.detectDown() == false then
    turtle.placeDown()
    else
     if turtle.detect() == true then
    turtle.dig()
    else
     turtle.forward()
     end
    end
  end
end