defmodule ExDav.Authenticator do
  @moduledoc """
  Behaviour for CalDAV authenticators.

  Given a `Plug.Conn` and adapter-specific opts, an authenticator decides
  whether the request is authorized and what principal name (CalDAV
  username) to use for storage scoping.

  See `ExDav.Authenticator.Basic` for an HTTP-Basic adapter.
  """

  @callback authenticate(Plug.Conn.t(), opts :: term()) ::
              {:ok, Plug.Conn.t(), principal :: String.t()} | :unauth
end