Randomized Quarry

local args = {...}

if #args < 1 then
 print("quarry <size> [height]")
end

function safeRefuel()
 if turtle.getFuelLevel() < 10 then
  print("Attempting to refuel.")
  turtle.refuel()
 end
end

function safeForward()
 if not turtle.dig() then
  turtle.forward()
 end
end

function safeDown()
 if turtle.detectDown() then
  turtle.digDown()
 end
 print("Going down a row.")
 turtle.down()
end

function excavate(radius)
 if radius < 2 then
  error("wrong radius, expected 2 or higher")
 end
 print("Excavating a row.")
 for h = 1,4 do
  for i = 1,radius do
   safeForward()
  end
  safeRefuel()
  turtle.turnRight()
 end
end

function digQuarry(size, height)
 if height < 2 then
  error("wrong height, expected 2 or higher")
 end
 for g = 1,height do
  excavate(size)
  safeDown()
 end
 print("Finished.")
end

if #args == 1 then
 excavate(tonumber(args[1]))
elseif #args == 2 then
 digQuarry(tonumber(args[1]), tonumber(args[2]))
end