cachex

defmodule Cachex.Actions.Empty do
  @moduledoc false
  # This module controls the action implementation for the `:empty?` command,

  # which checks whether the cache is currently empty or not. This action is

  # currently sugar around the `:size` command, which normalizing the numeric

  # results back into boolean values.


  # we need our imports

  use Cachex.Actions

  # add some aliases

  alias Cachex.Actions.Size
  alias Cachex.State

  @doc """

  Checks whether the cache contains any records.



  If the cache is not empty, we return a false response. It should be noted here

  that emptiness is determined by overall cache size, regardless of key expiration.

  Thus it may be that you have a non-empty cache, yet be unable to retrieve any

  keys due to on-demand expiration.



  We delegate this action internally to the Size action and simply cast the numeric

  value in the response into a boolean for consumption.



  There are currently no recognised options, the argument only exists for future

  proofing.

  """
  defaction empty?(%State{ } = state, options) do
    state
    |> Size.execute(@notify_false)
    |> handle_size
  end

  # Handles the casting of the size values back into booleans. If the size is

  # more than 0, we return false. If it's 0, we return true. There will never

  # be anything accepted below 0, so we don't need to worry about it.

  defp handle_size({ :ok, 0 }), do: { :ok, true }
  defp handle_size(_other_val), do: { :ok, false }

end