understated

defmodule Understated.StatePath do
  @doc ~S"""

  Pushes a new state onto the current state path.

  ## Examples

      iex> Understated.StatePath.push_state("", "new_state")
      "new_state"

      iex> Understated.StatePath.push_state("old_state", "new_state")
      "old_state.new_state"

  """
  def push_state(path, new_state) when path == "", do: new_state
  def push_state(path, new_state), do: "#{path}.#{new_state}"

  @doc ~S"""

  Pops a state off the current state path.

  ## Examples

      iex> Understated.StatePath.pop_state("", "to_pop")
      ""

      iex> Understated.StatePath.pop_state("to_pop", "to_pop")
      ""

      iex> Understated.StatePath.pop_state("not_to_pop.to_pop", "to_pop")
      "not_to_pop"

      iex> Understated.StatePath.pop_state("not_to_pop", "to_pop")
      "not_to_pop"

  """
  def pop_state(path, to_pop) when path == to_pop, do: ""
  def pop_state(path, to_pop), do: String.replace_trailing(path, ".#{to_pop}", "")
end