From 3e066fd23a8f4efbad8bea3764cef42f4ad484a6 Mon Sep 17 00:00:00 2001
From: Nikos Papadakis <nikos@papadakis.xyz>
Date: Sat, 3 Feb 2024 13:11:31 +0200
Subject: [PATCH] subscription

---
 app/lib/prymn/messaging/subscription.ex | 36 +++++++++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100644 app/lib/prymn/messaging/subscription.ex

diff --git a/app/lib/prymn/messaging/subscription.ex b/app/lib/prymn/messaging/subscription.ex
new file mode 100644
index 0000000..04c43fa
--- /dev/null
+++ b/app/lib/prymn/messaging/subscription.ex
@@ -0,0 +1,36 @@
+defmodule Prymn.Messaging.Subscription do
+  use GenServer
+
+  alias Prymn.Messaging
+
+  def start_link(%{agent_id: agent_id, subject: subject} = init_arg) do
+    name = {:via, Registry, {Prymn.Messaging.SubscriptionRegistry, agent_id <> subject}}
+    GenServer.start_link(__MODULE__, init_arg, name: name)
+  end
+
+  @impl true
+  def init(%{agent_id: agent_id, subject: subject, gnat: gnat, reply: reply}) do
+    Process.monitor(reply)
+    subject = "agents.v1.#{agent_id}.#{subject}"
+    {:ok, sub} = Gnat.sub(gnat, self(), subject)
+
+    {:ok, %{reply: reply, sub: sub, gnat: gnat}}
+  end
+
+  @impl true
+  def handle_info({:msg, %{body: body, topic: subject}}, %{reply: reply} = state) do
+    msg = Messaging.Messages.handle_message(subject, body)
+    send(reply, msg)
+
+    {:noreply, state}
+  end
+
+  def handle_info({:DOWN, _ref, :process, _object, _reason}, state) do
+    {:stop, {:shutdown, :gone}, state}
+  end
+
+  @impl true
+  def terminate({:shutdown, _}, state) do
+    Gnat.unsub(state.gnat, state.sub)
+  end
+end