1 files changed, 119 insertions, 0 deletions
diff --git a/lib/ejabberd/config/attr.ex b/lib/ejabberd/config/attr.ex
new file mode 100644
index 000000000..9d17b157d
--- /dev/null
+++ b/lib/ejabberd/config/attr.ex
@@ -0,0 +1,119 @@
+defmodule Ejabberd.Config.Attr do
+  @moduledoc """
+  Module used to work with the attributes parsed from
+  an elixir block (do...end).
+
+  Contains functions for extracting attrs from a block
+  and validation.
+  """
+
+  @type attr :: {atom(), any()}
+
+  @attr_supported [
+    active:
+      [type: :boolean, default: true],
+    git:
+      [type: :string, default: ""],
+    name:
+      [type: :string, default: ""],
+    opts:
+      [type: :list, default: []],
+    dependency:
+      [type: :list, default: []]
+  ]
+
+  @doc """
+  Takes a block with annotations and extracts the list
+  of attributes.
+  """
+  @spec extract_attrs_from_block_with_defaults(any()) :: [attr]
+  def extract_attrs_from_block_with_defaults(block) do
+    block
+    |> extract_attrs_from_block
+    |> put_into_list_if_not_already
+    |> insert_default_attrs_if_missing
+  end
+
+  @doc """
+  Takes an attribute or a list of attrs and validate them.
+
+  Returns a {:ok, attr} or {:error, attr, cause} for each of the attributes.
+  """
+  @spec validate([attr]) :: [{:ok, attr}] | [{:error, attr, atom()}]
+  def validate(attrs) when is_list(attrs), do: Enum.map(attrs, &valid_attr?/1)
+  def validate(attr), do: validate([attr]) |> List.first
+
+  @doc """
+  Returns the type of an attribute, given its name.
+  """
+  @spec get_type_for_attr(atom()) :: atom()
+  def get_type_for_attr(attr_name) do
+    @attr_supported
+    |> Keyword.get(attr_name)
+    |> Keyword.get(:type)
+  end
+
+  @doc """
+  Returns the default value for an attribute, given its name.
+  """
+  @spec get_default_for_attr(atom()) :: any()
+  def get_default_for_attr(attr_name) do
+    @attr_supported
+    |> Keyword.get(attr_name)
+    |> Keyword.get(:default)
+  end
+
+  # Private API
+
+  # Given an elixir block (do...end) returns a list with the annotations
+  # or a single annotation.
+  @spec extract_attrs_from_block(any()) :: [attr] | attr
+  defp extract_attrs_from_block({:__block__, [], attrs}), do: Enum.map(attrs, &extract_attrs_from_block/1)
+  defp extract_attrs_from_block({:@, _, [attrs]}), do: extract_attrs_from_block(attrs)
+  defp extract_attrs_from_block({attr_name, _, [value]}), do: {attr_name, value}
+  defp extract_attrs_from_block(nil), do: []
+
+  # In case extract_attrs_from_block returns a single attribute,
+  # then put it into a list. (Ensures attrs are always into a list).
+  @spec put_into_list_if_not_already([attr] | attr) :: [attr]
+  defp put_into_list_if_not_already(attrs) when is_list(attrs), do: attrs
+  defp put_into_list_if_not_already(attr), do: [attr]
+
+  # Given a list of attributes, it inserts the missing attribute with their
+  # default value.
+  @spec insert_default_attrs_if_missing([attr]) :: [attr]
+  defp insert_default_attrs_if_missing(attrs) do
+    Enum.reduce @attr_supported, attrs, fn({attr_name, _}, acc) ->
+      case Keyword.has_key?(acc, attr_name) do
+        true -> acc
+        false -> Keyword.put(acc, attr_name, get_default_for_attr(attr_name))
+      end
+    end
+  end
+
+  # Given an attribute, validates it and return a tuple with
+  # {:ok, attr} or {:error, attr, cause}
+  @spec valid_attr?(attr) :: {:ok, attr} | {:error, attr, atom()}
+  defp valid_attr?({attr_name, param} = attr) do
+    case Keyword.get(@attr_supported, attr_name) do
+      nil -> {:error, attr, :attr_not_supported}
+      [{:type, param_type} | _] -> case is_of_type?(param, param_type) do
+        true -> {:ok, attr}
+        false -> {:error, attr, :type_not_supported}
+      end
+    end
+  end
+
+  # Given an attribute value and a type, it returns a true
+  # if the value its of the type specified, false otherwise.
+
+  # Usefoul for checking if an attr value respects the type
+  # specified for the annotation.
+  @spec is_of_type?(any(), atom()) :: boolean()
+  defp is_of_type?(param, type) when type == :boolean and is_boolean(param), do: true
+  defp is_of_type?(param, type) when type == :string and is_bitstring(param), do: true
+  defp is_of_type?(param, type) when type == :list and is_list(param), do: true
+  defp is_of_type?(param, type) when type == :atom and is_atom(param), do: true
+  defp is_of_type?(_param, type) when type == :any, do: true
+  defp is_of_type?(_, _), do: false
+end