quarry

arg = {...}

if arg[1] ~= nil and arg[2] ~= nil then
  width = arg[1]
  length = arg[2]
else
  term.setTextColor(colors.red)
  print("usage: quarry <width> <length>")
end

x = 0
z = 0
y = 0
facing = 0

function refuel()
  if turtle.getFuelLevel() < 5 then
    turtle.refuel(1)
    return true
  end
end

function step()
  while not turtle.forward() do
    if not refuel() then
      if turtle.detect() then
        turtle.dig()
      else
        turtle.attack()
      end
    end
  end
  if facing == 0 then z = z + 1 end
  if facing == 2 then z = z - 1 end
  if facing == 1 then x = x + 1 end
  if facing == 3 then x = x - 1 end
end

function up()
  while not turtle.up() do
    if not refuel() then
      if turtle.detectUp() then
        turtle.digUp()
      else
        turtle.attackUp()
      end
    end
  end
  y = y + 1
end

function down()
  while not turtle.down() do
    if not refuel() then
      if turtle.detectDown() then
        turtle.digDown()
      else
        turtle.attackDown()
      end
    end
  end
  y = y - 1
end

function turnLeft()
  turtle.turnLeft()
  facing = facing - 1
  if facing < 0 then facing = 0 end
end

function turnRight()
  turtle.turnRight()
  facing = facing + 1
  if facing > 3 then facing = 3 end
end

function turnAround()
  if z == length-1 then
    function turn = turnRight
  elseif z == 0 then
    function turn = turnLeft
  end
  turn()
  step()
  turn()
end

function layer()
  for i = 1,width do
    for j = 1,length do
      step()
    end
    turnAround()
  end
end

function start()
  down()
  layer()
end