WE

function turn(left, mirrored)
  if left ~= mirrored then
    turtle.turnLeft()
  else
    turtle.turnRight()
  end
end

function digAll(depthleft)
  if turtle.detect() then
    turtle.dig()
  end
  if turtle.detectUp() and depthleft > 1 then
    turtle.digUp()
  end
  if turtle.detectDown() and depthleft > 2 then
    turtle.digDown()
  end
end

function nextSlotIfEmpty()
  while turtle.getItemCount() == 0 do
    turtle.select(turtle.getSelectedSlot() + 1)
  end
end

function place()
  nextSlotIfEmpty()
  turtle.place()
end
function placeUp()
  nextSlotIfEmpty()
  turtle.placeUp()
end
function placeDown()
  nextSlotIfEmpty()
  turtle.placeDown()
end

function placeAll(height)
  turtle.place()
  if height > 1 then
    turtle.placeDown()
  end
  if height > 2 then
    turtle.placeUp()
  end
end

function move()
  if turtle.detect() then
    return false
  end
  while not turtle.forward() do
    turtle.attack()
  end
  return true
end
function moveDown()
  if turtle.detectDown() then
    return false
  end
  while not turtle.down() do
    turtle.attackDown()
  end
  return true
end
function moveUp()
  if turtle.detectUp() then
    return false
  end
  while not turtle.up() do
    turtle.attackUp()
  end
  return true
end
function moveBack()
  if not turtle.back() then
    turtle.turnLeft()
    turtle.turnLeft()
    if turtle.detect() then
      return false
    end
    while not turtle.forward() do
      turtle.attack()
    end
    turtle.turnRight()
    turtle.turnRight()
    return true
  end
end

function Dmove()
  if turtle.detect() then
    if not turtle.dig() then
      return false
    end
  end
  while not turtle.forward() do
    turtle.attack()
  end
  return true
end
function DmoveDown()
  if turtle.detectDown() then
    if not turtle.digDown() then
      return false
    end
  end
  while not turtle.down() do
    turtle.attackDown()
  end
  return true
end
function DmoveUp()
  if turtle.detectUp() then
    if not turtle.digUp() then
      return false
    end
  end
  while not turtle.up() do
    turtle.attackUp()
  end
  return true
end
function DmoveBack()
  if not turtle.back() then
    turtle.turnLeft()
    turtle.turnLeft()
    if turtle.detect() then
      if not turtle.dig() then
        return false
      end
    end
    while not turtle.forward() do
      turtle.attack()
    end
    turtle.turnRight()
    turtle.turnRight()
    return true
  end
end


local cube = {
  help = "cube <length> <width> <depth> [left]"
}

function cube.fuel(length, width, depth)
  length = tonumber(length)
  width = tonumber(width)
  depth = tonumber(depth)
  return depth + math.ceil(depth / 3) * (length * width - 1)
end

function cube.run(length, width, depth, mirrored)
  length = tonumber(length)
  width = tonumber(width)
  depth = tonumber(depth)
  if mirrored ~= true then mirrored = false end
  local depthleft = depth
  local direction = false

  while depthleft > 0 do
    if turtle.detectDown() then
      turtle.digDown()
    end
    moveDown()
    if depthleft > 1 then
      if turtle.detectDown() then
        turtle.digDown()
      end
      moveDown()
    end
    if depthleft > 2 then
      turtle.digDown()
    end


    local x = 1
    local y = 1
    while true do
      if x >= length then --turn
        if y >= width then --down
          if turtle.detectUp() and depthleft > 1 then
            turtle.digUp()
          end
          if turtle.detectDown() and depthleft > 2 then
            turtle.digDown()
          end
          turtle.turnLeft()
          turtle.turnLeft()
          if depthleft > 2 then
            turtle.down()
          end
          depthleft = depthleft - 3
          break
        end
        turn(direction, mirrored)
        digAll(depthleft)
        move()
        turn(direction, mirrored)
        digAll(depthleft)
        move()
        y = y + 1
        x = 1
        direction = not direction
      else
        digAll(depthleft)
        move()
      end
      x = x + 1
    end
  end
end


local wall = {
  help = "wall <length> <width> <height> [left]"
}

function wall.fuel(length, width, height)
  length = tonumber(length)
  width = tonumber(width)
  height = tonumber(height)
  return height + math.ceil(height / 3) * (2 * length + 2 * width - 1)
end

function wall.run(length, width, height, mirrored)
  length = tonumber(length)
  width = tonumber(width)
  height = tonumber(height)
  if mirrored ~= true then mirrored = false end
  Dmove()
  turtle.turnLeft()
  turtle.turnLeft()
  while height > 0 do
    if height > 1 then
      DmoveUp()
      placeDown()
      if height > 2 then
        placeUp()
      end
    end
    local direction = 0
    while direction < 4 do
      local i = 1
      while i < (direction % 2 == 0 and length or width) do
        DmoveBack()
        placeAll(height)
        i = i + 1
      end
      turn(true, mirrored)
      direction = direction + 1
    end

  end
end


function getCommand(command)
  if command == "help" then return help end
  if command == "wall" then return wall end
  if command == "cube" then return cube end
  return nil
end

local help = {
  help = "help <command>"
}

function help.run(command)
  local result = getCommand(command)
  if result == nil then
    print("help: command not found")
  else
    print("usage: " .. result.help)
  end
end


args = {...}
local command = getCommand(table.remove(args, 1))
if command == nil then
  print("command not found")
  return
end
if command.fuel ~= nil then
  local required = command.fuel(unpack(args))
  local now = turtle.getFuelLevel()
  if required > now then
    print("not enough fuel: " .. required .. " needed, has " .. now .. " (" .. (required - now) .. " short)")
    return
  end
end
command.run(unpack(args))