defmodule KeenAuth.Plug do
  @behaviour Plug

  alias Plug.Conn
  alias KeenAuth.Config

  @private_config_key :keen_auth_config

  def init(config), do: config

  def call(conn, config) do
    put_config(conn, config)
  end

  @doc """
  Put the provided config as a private key in the connection.
  """
  @spec put_config(Conn.t(), Config.t()) :: Conn.t()
  def put_config(conn, config) do
    Conn.put_private(conn, @private_config_key, config)
  end

  @doc """
  Fetch configuration from the private key in the connection.

  It'll raise an error if configuration hasn't been set as a private key.
  """
  @spec fetch_config(Conn.t()) :: Config.t()
  def fetch_config(%{private: private}) do
    private[@private_config_key] || no_config_error!()
  end

  @spec no_config_error!() :: no_return()
  defp no_config_error!,
    do: Config.raise_error("KeenAuth configuration not found in connection. Please use a KeenAuth plug that puts the KeenAuth configuration in the plug connection.")
end