Implement handle_leave and handle_join in presence_client

- The profile Liveview is subscribed to active_users topic
- user_joined and user_left events are sent
- Users are added and removed from presences assign

lib/live_beats/accounts.ex

@@ -21,6 +21,10 @@ defmodule LiveBeats.Accounts do
     Repo.all(from u in User, limit: ^Keyword.fetch!(opts, :limit))
   end
 
+  def list_users_by_ids(user_ids) when is_list(user_ids) do
+    Repo.all(from u in User, where: u.id in ^user_ids)
+  end
+
   def lists_users_by_active_profile(id, opts) do
     Repo.all(
       from u in User, where: u.active_profile_user_id == ^id, limit: ^Keyword.fetch!(opts, :limit)

lib/live_beats/presence/presence_client.ex

@@ -1,7 +1,8 @@
 defmodule LiveBeats.PresenceClient do
   @behaviour Phoenix.Presence.Client
 
-  @presence LiveBeats.Presence
+  @presence LiveBeatsWeb.Presence
+  @pubsub LiveBeats.PubSub
 
   def start_link(opts) do
     Phoenix.Presence.Client.start_link(presence: @presence, client: __MODULE__)
@@ -16,13 +17,33 @@ defmodule LiveBeats.PresenceClient do
     {:ok, %{}}
   end
 
-  def handle_join(key, presence, state) do
+  def handle_join(topic, key, meta, state) do
-    # can local pubsub to LVs about new join
+    active_users_topic =
+      topic
+      |> profile_identifier()
+      |> active_users_topic()
+
+    Phoenix.PubSub.broadcast!(@pubsub, active_users_topic, {__MODULE__, %{user_joined: key}})
+
     {:ok, state}
   end
 
-  def handle_leave(key, presence, state) do
+  def handle_leave(topic, key, presence, state) do
-    # can local pubsub to LVs about new leave
+    active_users_topic =
+      topic
+      |> profile_identifier()
+      |> active_users_topic()
+
+    Phoenix.PubSub.broadcast!(@pubsub, active_users_topic, {__MODULE__, %{user_left: key}})
     {:ok, state}
   end
+
+  defp active_users_topic(user_id) do
+    "active_users:#{user_id}"
+  end
+
+  defp profile_identifier(topic) do
+    "active_profile:" <> identifier = topic
+    identifier
+  end
 end

lib/live_beats_web/channels/presence.ex

@@ -10,6 +10,7 @@ defmodule LiveBeatsWeb.Presence do
 
   import Phoenix.LiveView.Helpers
   import LiveBeatsWeb.LiveHelpers
+  @pubsub LiveBeats.PubSub
 
   def listening_now(assigns) do
     ~H"""
@@ -31,4 +32,12 @@ defmodule LiveBeatsWeb.Presence do
     </div>
     """
   end
+
+  def subscribe(user_id) do
+    Phoenix.PubSub.subscribe(@pubsub, topic(user_id))
+  end
+
+  defp topic(profile) do
+    "active_users:#{profile.user_id}"
+  end
 end

lib/live_beats_web/live/profile_live.ex

@@ -87,6 +87,7 @@ defmodule LiveBeatsWeb.ProfileLive do
     if connected?(socket) do
       MediaLibrary.subscribe_to_profile(profile)
       Accounts.subscribe(current_user.id)
+      LiveBeatsWeb.Presence.subscribe(profile)
       Phoenix.Presence.Client.track(topic(profile.user_id),
         current_user.id,
         %{}
@@ -146,6 +147,22 @@ defmodule LiveBeatsWeb.ProfileLive do
     {:noreply, socket}
   end
 
+  def handle_info({LiveBeats.PresenceClient, %{user_joined: user_id}}, socket) do
+    new_user = Accounts.get_user!(user_id)
+    updated_presences =
+    if new_user in socket.assigns.presences do
+      socket.assigns.presences
+    else
+      [new_user | socket.assigns.presences]
+    end
+    {:noreply, assign(socket, :presences, updated_presences)}
+  end
+
+  def handle_info({LiveBeats.PresenceClient, %{user_left: user_id}}, socket) do
+    updated_presences = socket.assign.presences |> Enum.reject(fn user -> user.id == user_id end)
+    {:noreply, assign(socket, :presences, updated_presences)}
+  end
+
   def handle_info({Accounts, %Accounts.Events.ActiveProfileChanged{} = event}, socket) do
     {:noreply, assign(socket, active_profile_id: event.new_profile_user_id)}
   end
@@ -173,14 +190,6 @@ defmodule LiveBeatsWeb.ProfileLive do
 
   def handle_info({Accounts, _}, socket), do: {:noreply, socket}
 
-  def handle_info(
-        %{event: "presence_diff", payload: %{joins: _joins, leaves: _leaves}},
-        %{assigns: %{presences: _users}} = socket
-      ) do
-
-    {:noreply, assign_presences(socket)}
-  end
-
   defp stop_song(socket, song_id) do
     SongRowComponent.send_status(song_id, :stopped)
 
@@ -256,11 +265,11 @@ defmodule LiveBeatsWeb.ProfileLive do
   defp assign_presences(socket) do
     presences = socket.assigns.profile.user_id
     |> topic()
-    |> Presence.list()
+    |> LiveBeats.PresenceClient.list()
-    |> Enum.map(fn {_user_id, user_data} ->
+    |> Enum.map(fn {user_id, _user_data} ->
-      user_data[:metas]
+      user_id
-      |> List.first()
     end)
+    |> Accounts.list_users_by_ids()
 
     assign(socket, presences: presences)
   end
@@ -272,5 +281,5 @@ defmodule LiveBeatsWeb.ProfileLive do
     uri.host <> uri.path
   end
 
-  defp topic(user_id) when is_integer(user_id), do: "profile:#{user_id}"
+  defp topic(user_id) when is_integer(user_id), do: "active_profile:#{user_id}"
 end