util.lua

local function turn(direction, count)
  if direction ~= "left" and direction ~= "right" then
    error("Invalid direction: " .. direction)
  end

  local count = count or 1
  local success, msg = nil, nil

  for i = 1, count do
    if direction == "left" then
      success, msg = turtle.turnLeft()
    else
      success, msg = turtle.turnRight()
    end
    if not success then
      error(msg)
    end
  end
end

local function checkFull()
  for i = 1, 16 do
    if turtle.getItemSpace(i) > 0 then
      return false
    end
  end
  return true
end

local function dig(direction, returnFacing)
  while checkFull() do
    print("Inventory full...")
    local event, key, is_held = os.pullEvent("key")
  end

  if returnFacing == nil then
    returnFacing = true
  end

  local success, msg = nil, nil

  if direction == "up" then
    if turtle.detectUp() then
      success, msg = turtle.digUp()
    end
  elseif direction == "down" then
    if turtle.detectDown() then
      success, msg = turtle.digDown()
    end
  elseif direction == "left" then
    turtle.turnLeft()
    if turtle.detect() then
      success, msg = turtle.dig()
    end
    if returnFacing then
      turtle.turnRight()
    end
  elseif direction == "right" then
    turtle.turnRight()
    if turtle.detect() then
      success, msg = turtle.dig()
    end
    if returnFacing then
      turtle.turnLeft()
    end
  elseif turtle.detect() then
    success, msg = turtle.dig()
  end

  if not success and not msg == "Nothing to dig here" then
    error(msg)
  end
end

local function go(direction)
  local success, msg = nil, nil

  if direction == "up" then
    dig("up")
    success, msg = turtle.up()
  elseif direction == "down" then
    dig("down")
    success, msg = turtle.down()
  elseif direction == "forward" then
    dig()
    success, msg = turtle.forward()
  elseif direction == "back" then
    turn("right", 2)
    dig()
    success, msg = turtle.forward()
    turn("right", 2)
  elseif direction == "left" then
    turn("left")
    dig()
    success, msg = turtle.forward()
    turn("right")
  elseif direction == "right" then
    turn("right")
    dig()
    success, msg = turtle.forward()
    turn("left")
  else
    error("Invalid direction: " .. direction)
  end

  if not success then
    error(msg)
  end
end

return {
  turn = turn,
  dig = dig,
  go = go
}