From 1337c4001fc0e384fd9e02ac814484af45a47009 Mon Sep 17 00:00:00 2001
From: Luca Corti <luca@fantacast.it>
Date: Sun, 10 Nov 2024 13:06:29 +0100
Subject: [PATCH] Convert RDE to gen_statem

---
 lib/bgp/server/rde.ex | 35 +++++++++++++++++++++++++++--------
 1 file changed, 27 insertions(+), 8 deletions(-)

diff --git a/lib/bgp/server/rde.ex b/lib/bgp/server/rde.ex
index 7540a39..9ada298 100644
--- a/lib/bgp/server/rde.ex
+++ b/lib/bgp/server/rde.ex
@@ -1,25 +1,44 @@
 defmodule BGP.Server.RDE do
   @moduledoc false
 
+  @behaviour :gen_statem
+
   alias BGP.{Message.UPDATE, Server}
 
-  use GenServer
+  require Logger
+
+  @enforce_keys [:config]
+  defstruct [:config]
 
   @spec start_link(Keyword.t()) :: GenServer.on_start()
   def start_link(args),
-    do: GenServer.start_link(__MODULE__, args, name: Server.rde_for(args[:server]))
+    do: :gen_statem.start_link({:local, Server.rde_for(args[:server])}, __MODULE__, args, [])
+
+  @doc false
+  def child_spec({args, opts}),
+    do: %{id: make_ref(), start: {__MODULE__, :start_link, [{args, opts}]}}
+
+  def child_spec(opts),
+    do: %{id: make_ref(), start: {__MODULE__, :start_link, [opts]}}
 
   @spec process_update(Server.t(), UPDATE.t()) :: :ok
   def process_update(server, update),
     do: GenServer.call(Server.rde_for(server), {:process_update, update})
 
-  @impl GenServer
-  def init(_args) do
-    {:ok, %{rib: MapSet.new(), rib_in: MapSet.new(), rib_out: MapSet.new()}}
+  @impl :gen_statem
+  def callback_mode, do: [:handle_event_function, :state_enter]
+
+  @impl :gen_statem
+  def init(args), do: {:ok, :ready, %__MODULE__{config: args}}
+
+  @impl :gen_statem
+  def handle_event(:enter, old_state, new_state, %__MODULE__{}) do
+    Logger.info("#{old_state} -> #{new_state}")
+    :keep_state_and_data
   end
 
-  @impl GenServer
-  def handle_call({:process_update, %UPDATE{}}, _from, state) do
-    {:reply, :ok, state}
+  @impl :gen_statem
+  def handle_event({:call, from}, {:process_update, %UPDATE{}}, _state, _data) do
+    {:keep_state_and_data, {:reply, from, :ok}}
   end
 end