docs: Add documents for openflow actions

lib/openflow/actions/output.ex

@@ -1,31 +1,67 @@
 defmodule Openflow.Action.Output do
-  defstruct(
-    port_number: 0,
-    max_len: :no_buffer
-  )
+  @moduledoc """
+  Action for sends packets out `port_number`.
+  """
+
+  defstruct port_number: 0,
+            max_len: :no_buffer
 
   alias __MODULE__
 
+  @type port_no ::
+          0..0xFFFFFFFF
+          | :max
+          | :in_port
+          | :table
+          | :normal
+          | :flood
+          | :all
+          | :controller
+          | :local
+          | :any
+
+  @type max_len :: 0..0xFFFFFFFF | :no_buffer | :max
+
+  @type t :: %Output{port_number: port_no(), max_len: max_len()}
+
+  @spec ofpat() :: 0
   def ofpat, do: 0
 
+  @doc """
+  Create a new output action structure
+
+  ## Options:
+    - `port_number`: port number that sends a packet from
+    - `max_len`: byte length of the packet that sends to the controller
+
+  ## Example
+
+  ```elixir
+  iex> %Output{port_number: 1, max_len: :no_buffer} = Output.new(1)
+  ```
+  """
+  @spec new([port_number: port_no, max_len: max_len()] | port_no()) :: Output.t()
   def new(options \\ [])
 
-  def new(port) when not is_list(port) do
-    new(port_number: port)
-  end
+  @spec new(port :: port_no()) :: Output.t()
+  def new(port) when is_atom(port) or is_integer(port),
+    do: new(port_number: port)
 
+  @spec new(options :: [port_number: port_no(), max_len: max_len()]) :: Output.t()
   def new(options) when is_list(options) do
     port_no = options[:port_number] || raise "port_number must be specified"
     max_len = options[:max_len] || :no_buffer
     %Output{port_number: port_no, max_len: max_len}
   end
 
+  @spec to_binary(Output.t()) :: <<_::16, _::_*8>>
   def to_binary(%Output{port_number: port_no, max_len: max_len}) do
     port_no_int = Openflow.Utils.get_enum(port_no, :openflow13_port_no)
     max_len = Openflow.Utils.get_enum(max_len, :controller_max_len)
     <<0::16, 16::16, port_no_int::32, max_len::16, 0::size(6)-unit(8)>>
   end
 
+  @spec read(<<_::16, _::_*8>>) :: Output.t()
   def read(<<0::16, 16::16, port_no_int::32, max_len::16, _pad::size(6)-unit(8)>>) do
     port_no = Openflow.Utils.get_enum(port_no_int, :openflow13_port_no)
     max_len = Openflow.Utils.get_enum(max_len, :controller_max_len)