From 7b416e354fb9423044290c419fbb5b7a35ea3c06 Mon Sep 17 00:00:00 2001
From: meppu <meppu@proton.me>
Date: Wed, 5 Jul 2023 00:52:32 +0300
Subject: [PATCH] handle empty array

---
 README.md                      |  2 +-
 lib/revard/gateway/listener.ex | 28 +++++++++++++++++-----------
 2 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/README.md b/README.md
index b72e6e9..49de19d 100644
--- a/README.md
+++ b/README.md
@@ -104,7 +104,7 @@ To subscribe to one or more users, make use of the `subscribe` event:
 }
 ```
 
-By doing so, you will receive real-time updates for the specified users within the `ids` array.
+By doing so, you will receive real-time updates for the specified users within the `ids` array. If the `ids` is an empty list (`[]`) or `null`, it will unsubscribe from all the subscriptions without returning anything.
 
 To update subscribers, resend the same data with the updated `ids` value.
 
diff --git a/lib/revard/gateway/listener.ex b/lib/revard/gateway/listener.ex
index 3dd9458..3663fe6 100644
--- a/lib/revard/gateway/listener.ex
+++ b/lib/revard/gateway/listener.ex
@@ -48,20 +48,33 @@ defmodule Revard.Gateway.Listener do
     {:ok, state}
   end
 
+  defp match_message(%{"event" => "subscribe", "ids" => nil}, state) do
+    # Unsubscribe all
+    Enum.each(state, &Phoenix.PubSub.unsubscribe(@pubsub, &1))
+
+    {:ok, []}
+  end
+
+  defp match_message(%{"event" => "subscribe", "ids" => []} = message, state) do
+    message
+    |> Map.put("ids", nil)
+    |> match_message(state)
+  end
+
   defp match_message(%{"event" => "subscribe", "ids" => ids}, state) when is_list(ids) do
     # Check format
     if Enum.all?(ids, &check_id/1) do
       # Unsubscribe all
       Enum.each(state, &Phoenix.PubSub.unsubscribe(@pubsub, &1))
 
-      # Subscribe given ones
-      Enum.each(ids, &Phoenix.PubSub.subscribe(@pubsub, &1))
-
       # Debug message
       Logger.debug(
-        "Connection #{inspect(self())} subscribed to following id(s): #{inspect(ids)} (socket)"
+        "Connection #{inspect(self())} subscribing to following id(s): #{inspect(ids)} (socket)"
       )
 
+      # Subscribe given ones
+      Enum.each(ids, &Phoenix.PubSub.subscribe(@pubsub, &1))
+
       # Reply with initial message
       initial_message =
         %{type: "init", data: Revard.Storage.Users.get(ids)}
@@ -73,13 +86,6 @@ defmodule Revard.Gateway.Listener do
     end
   end
 
-  defp match_message(%{"event" => "subscribe", "ids" => nil}, state) do
-    # Unsubscribe all
-    Enum.each(state, &Phoenix.PubSub.unsubscribe(@pubsub, &1))
-
-    {:ok, []}
-  end
-
   defp match_message(_message, state) do
     invalid_payload_error(state)
   end