Server handler opts (#41)

* Add an option to pass an argument to the handler

README.md

@@ -18,7 +18,7 @@ of dependencies in `mix.exs`:
 ```elixir
 def deps do
   [
-    {:membrane_rtsp, "~> 0.7.2"}
+    {:membrane_rtsp, "~> 0.8.0"}
   ]
 end
 ```

lib/membrane_rtsp/server.ex

@@ -28,15 +28,16 @@ defmodule Membrane.RTSP.Server do
 
   alias __MODULE__.Conn
 
-  @type server_config :: [
-          handler: module(),
-          name: term(),
-          port: :inet.port_number(),
-          address: :inet.ip_address(),
-          udp_rtp_port: :inet.port_number(),
-          udp_rtcp_port: :inet.port_number(),
-          session_timeout: non_neg_integer()
-        ]
+  @type server_option ::
+          {:handler, module()}
+          | {:handler_config, term()}
+          | {:name, term()}
+          | {:port, :inet.port_number()}
+          | {:address, :inet.ip_address()}
+          | {:udp_rtp_port, :inet.port_number()}
+          | {:udp_rtcp_port, :inet.port_number()}
+          | {:session_timeout, non_neg_integer()}
+  @type server_config :: [server_option()]
 
   @doc """
   Start an instance of the RTSP server.
@@ -54,6 +55,7 @@ defmodule Membrane.RTSP.Server do
   ## Options
     - `handler` - An implementation of the behaviour `Membrane.RTSP.Server.Handler`. Refer to the module
     documentation for more details. This field is required.
+    - `handler_config` - Term that will be passed as an argument to `init/1` callback of the handler. Defaults to `nil`.
     - `name` - Used for name registration of the server. Defaults to `nil`.
     - `port` - The port where the server will listen for client connections. Defaults to: `554`
     - `address` - Specify the address where the `tcp` and `udp` sockets will be bound. Defaults to `:any`.
@@ -115,6 +117,7 @@ defmodule Membrane.RTSP.Server do
     state = %{
       socket: socket,
       handler: config[:handler],
+      handler_state: config[:handler].init(config[:handler_config]),
       udp_rtp_socket: udp_rtp_socket,
       udp_rtcp_socket: udp_rtcp_socket,
       client_conns: %{},
@@ -136,7 +139,7 @@ defmodule Membrane.RTSP.Server do
   def handle_info({:new_connection, client_socket}, state) do
     child_state =
       state
-      |> Map.take([:handler, :session_timeout, :udp_rtp_socket, :udp_rtcp_socket])
+      |> Map.take([:handler, :handler_state, :session_timeout, :udp_rtp_socket, :udp_rtcp_socket])
       |> Map.put(:socket, client_socket)
 
     case Conn.start(child_state) do

lib/membrane_rtsp/server/conn.ex

@@ -18,7 +18,8 @@ defmodule Membrane.RTSP.Server.Conn do
     state = %Logic.State{
       socket: config.socket,
       request_handler: config.handler,
-      request_handler_state: config.handler.handle_open_connection(config.socket),
+      request_handler_state:
+        config.handler.handle_open_connection(config.socket, config.handler_state),
       rtp_socket: config.udp_rtp_socket,
       rtcp_socket: config.udp_rtcp_socket,
       session_timeout: config.session_timeout

lib/membrane_rtsp/server/handler.ex

@@ -53,7 +53,7 @@ defmodule Membrane.RTSP.Server.Handler do
 
   ## State
   The handler may need to keep some state between the callback calls. To achieve this, the returned value from
-  `c:handle_open_connection/1` callback will be used as a state and will be the last argument for the other callbacks.
+  `c:init/1` callback will be used as a state and will be the last argument for the other callbacks.
 
   > #### `Missing callbacks in the handler` {: .info}
   >
@@ -64,6 +64,10 @@ defmodule Membrane.RTSP.Server.Handler do
   > `GET_PARAMETER` is used to keep the session alive and the server is responsible for setting session timeout
   >
   > The other methods are not yet implemented.
+
+  ## `use Membrane.RTSP.Server.Handler` {: .info}
+  When you `use Membrane.RTSP.Server.Handler`, the module will set `@behaviour Membrane.RTSP.Server.Handler` and
+  define the default implementation for `init/1` callback.
   """
 
   alias Membrane.RTSP.{Request, Response}
@@ -72,6 +76,7 @@ defmodule Membrane.RTSP.Server.Handler do
   Any term that will be used to keep state between the callbacks.
   """
   @type state :: term()
+  @type config :: term()
   @type control_path :: binary()
   @type ssrc :: non_neg_integer()
   @type conn :: :inet.socket()
@@ -106,12 +111,20 @@ defmodule Membrane.RTSP.Server.Handler do
         }
 
   @doc """
-  Callback called when a new connection is established.
+  Optional callback called when the server is initialized.
+
+  The argument is a term passed to the server as the `handler_config` option. 
+  The returned value will be used as a state and passed as the last 
+  argument to the subsequent callbacks.
 
-  The returned value is used as a state and is passed as the last argument to
-  the subsequent callbacks
+  Default behavior is to return the argument unchanged.
   """
-  @callback handle_open_connection(conn()) :: state()
+  @callback init(config()) :: state()
+
+  @doc """
+  Callback called when a new connection is established.
+  """
+  @callback handle_open_connection(conn(), state()) :: state()
 
   @doc """
   Callback called when a connection is closed.
@@ -160,4 +173,17 @@ defmodule Membrane.RTSP.Server.Handler do
   the session.
   """
   @callback handle_teardown(state()) :: {Response.t(), state()}
+
+  @optional_callbacks init: 1
+
+  defmacro __using__(_options) do
+    quote do
+      @behaviour unquote(__MODULE__)
+
+      @impl true
+      def init(config), do: config
+
+      defoverridable init: 1
+    end
+  end
 end

mix.exs

@@ -1,7 +1,7 @@
 defmodule Membrane.RTSP.MixProject do
   use Mix.Project
 
-  @version "0.7.2"
+  @version "0.8.0"
   @github_url "https://github.com/membraneframework/membrane_rtsp"
 
   def project do