helper functions

lib/vonbraun/util.ex

@@ -10,4 +10,36 @@ defmodule Vonbraun.Util do
   def my_key_id() do
     "#{my_id()}#main-key"
   end
+
+  @doc """
+  For the passed thing, get only the ID. If binary, assumed to be the ID. There
+  should only be one item in list if it is a list, otherwise return an error.
+  """
+  def get_only_id(id) when is_binary(id), do: {:ok, id}
+
+  def get_only_id(%{"@id" => id}) when is_binary(id), do: {:ok, id}
+
+  def get_only_id([thing]) when is_binary(thing) or is_map(thing), do: get_only_id(thing)
+
+  def get_only_id(_), do: :error
+
+  @doc """
+  For the passed property value, assume there should only be one value. If a
+  list, return the item if length of list is one, else error. Any other type,
+  return it as-is.
+  """
+  def get_only_property([property]), do: {:ok, property}
+
+  def get_only_property(property) when is_list(property), do: {:error}
+
+  def get_only_property(property), do: {:ok, property}
+
+  @doc """
+  For a passed value, if it is a bare id
+  """
+  def is_only_id?(object = %{"@id" => id}) when map_size(object) == 1 and is_binary(id), do: true
+
+  def is_only_id?([value]) when not is_list(value), do: is_only_id?(value)
+
+  def is_only_id?(_), do: false
 end