From 23565db8334d23f10a05c7db33838c50fefe1764 Mon Sep 17 00:00:00 2001
From: Michael Ries <riesmmm@gmail.com>
Date: Sat, 19 Oct 2024 13:35:36 +0900
Subject: [PATCH] introduce the Gnat.Supervisor macro

---
 config/config.exs                 |  8 ++++
 lib/gnat/connection_supervisor.ex |  4 +-
 lib/gnat/supervisor.ex            | 72 +++++++++++++++++++++++++++++++
 test/gnat/supervisor_test.exs     | 24 +++++++++++
 4 files changed, 106 insertions(+), 2 deletions(-)
 create mode 100644 config/config.exs
 create mode 100644 lib/gnat/supervisor.ex
 create mode 100644 test/gnat/supervisor_test.exs

diff --git a/config/config.exs b/config/config.exs
new file mode 100644
index 0000000..91b175f
--- /dev/null
+++ b/config/config.exs
@@ -0,0 +1,8 @@
+import Config
+
+if Mix.env() == :test do
+  config :gnat, Gnat.SupervisorTest.MyApp.Gnat,
+    connection_settings: [
+      %{}
+    ]
+end
diff --git a/lib/gnat/connection_supervisor.ex b/lib/gnat/connection_supervisor.ex
index 9940bc2..072359d 100644
--- a/lib/gnat/connection_supervisor.ex
+++ b/lib/gnat/connection_supervisor.ex
@@ -13,8 +13,8 @@ defmodule Gnat.ConnectionSupervisor do
     name: :gnat, # (required) the registered named you want to give the Gnat connection
     backoff_period: 4_000, # number of milliseconds to wait between consecutive reconnect attempts (default: 2_000)
     connection_settings: [
-      %{host: '10.0.0.100', port: 4222},
-      %{host: '10.0.0.101', port: 4222},
+      %{host: ~c"10.0.0.100", port: 4222},
+      %{host: ~c"10.0.0.101", port: 4222},
     ]
   }
   ```
diff --git a/lib/gnat/supervisor.ex b/lib/gnat/supervisor.ex
new file mode 100644
index 0000000..161d844
--- /dev/null
+++ b/lib/gnat/supervisor.ex
@@ -0,0 +1,72 @@
+defmodule Gnat.Supervisor do
+  defmacro __using__(opts) do
+    quote do
+      @mod __MODULE__
+
+      use Supervisor
+
+      def start_link(init_arg) do
+        Supervisor.start_link(__MODULE__, init_arg)
+      end
+
+      @impl true
+      def init(_init_arg) do
+        otp_app = unquote(opts)[:otp_app] || raise ArgumentError, "otp_app option is required"
+        config = Application.get_env(otp_app, @mod, [])
+
+        children = [
+          {Gnat.ConnectionSupervisor, connection_opts(config)},
+          consumer_supervisor(config)
+        ]
+        |> List.flatten()
+
+        Supervisor.init(children, strategy: :one_for_one)
+      end
+
+      defp connection_opts(config) do
+        %{
+          name: @mod,
+          connection_settings: Keyword.get(config, :connection_settings)
+        }
+      end
+
+      defp consumer_supervisor(config) do
+        case Keyword.get(config, :topics) do
+          nil -> []
+          topics when is_list(topics) -> [{Gnat.ConsumerSupervisor, topics}]
+          _ -> raise ArgumentError, "Invalid :topics option. Expected a list of topics."
+        end
+      end
+
+      ## Functions that forward to Gnat connection
+
+      def active_subscriptions() do
+        Gnat.active_subscriptions(@mod)
+      end
+
+      def pub(topic, message, opts \\ []) do
+        Gnat.pub(@mod, topic, message, opts)
+      end
+
+      def request(topic, body, opts \\ []) do
+        Gnat.request(@mod, topic, body, opts)
+      end
+
+      def request_multi(topic, body, opts \\ []) do
+        Gnat.request_multi(@mod, topic, body, opts)
+      end
+
+      def server_info() do
+        Gnat.server_info(@mod)
+      end
+
+      def sub(subscriber, topic, opts \\ []) do
+        Gnat.sub(@mod, subscriber, topic, opts)
+      end
+
+      def unsub(sid, opts \\ []) do
+        Gnat.unsub(@mod, sid, opts)
+      end
+    end
+  end
+end
diff --git a/test/gnat/supervisor_test.exs b/test/gnat/supervisor_test.exs
new file mode 100644
index 0000000..55c935e
--- /dev/null
+++ b/test/gnat/supervisor_test.exs
@@ -0,0 +1,24 @@
+defmodule Gnat.SupervisorTest do
+  use ExUnit.Case, async: true
+
+  defmodule MyApp.Gnat do
+    use Gnat.Supervisor, otp_app: :gnat
+  end
+
+  test "it can be supervised" do
+    assert MyApp.Gnat.child_spec([]) == %{
+      id: MyApp.Gnat,
+      start: {MyApp.Gnat, :start_link, [[]]},
+      type: :supervisor
+    }
+  end
+
+  test "when started - it provides an API that does not require a Gnat connection arg" do
+    {:ok, _pid} = MyApp.Gnat.start_link([])
+    :timer.sleep(100)
+    {:ok, _sub} = MyApp.Gnat.sub(self(), "my_app.topic")
+    :ok = MyApp.Gnat.pub("my_app.topic", "ohai")
+    assert_receive {:msg, %{topic: "my_app.topic", body: "ohai"}}
+    assert Supervisor.stop(MyApp.Gnat) == :ok
+  end
+end