From 924da28b6b0df89ee1a7947a4018aac31a876311 Mon Sep 17 00:00:00 2001
From: Chris McCord <chris@chrismccord.com>
Date: Wed, 12 Jan 2022 12:27:30 -0500
Subject: [PATCH] Move presence tracking to player

---
 .../presence/phoenix_presence_client.ex       |  4 +-
 lib/live_beats/presence/presence_client.ex    | 58 ++++++++++---------
 lib/live_beats_web/channels/presence.ex       | 41 ++++++-------
 lib/live_beats_web/live/player_live.ex        | 10 +++-
 lib/live_beats_web/live/profile_live.ex       | 23 +++-----
 5 files changed, 67 insertions(+), 69 deletions(-)

diff --git a/lib/live_beats/presence/phoenix_presence_client.ex b/lib/live_beats/presence/phoenix_presence_client.ex
index afda887..d416217 100644
--- a/lib/live_beats/presence/phoenix_presence_client.ex
+++ b/lib/live_beats/presence/phoenix_presence_client.ex
@@ -83,9 +83,9 @@ defmodule Phoenix.Presence.Client do
   defp untrack_pid(state, pid, topic, key) do
     if Map.has_key?(state.topics, topic) do
       state.presence_mod.untrack(pid, topic, key)
-    else
-      state
     end
+
+    state
   end
 
   defp merge_diff(state, topic, %{leaves: leaves, joins: joins}) do
diff --git a/lib/live_beats/presence/presence_client.ex b/lib/live_beats/presence/presence_client.ex
index 0ddec5e..e72c2a2 100644
--- a/lib/live_beats/presence/presence_client.ex
+++ b/lib/live_beats/presence/presence_client.ex
@@ -4,6 +4,31 @@ defmodule LiveBeats.PresenceClient do
   @presence LiveBeatsWeb.Presence
   @pubsub LiveBeats.PubSub
 
+  alias LiveBeats.MediaLibrary
+
+  def track(%MediaLibrary.Profile{} = profile, current_user_id) do
+    Phoenix.Presence.Client.track(
+      "proxy:" <> topic(profile),
+      current_user_id,
+      %{}
+    )
+  end
+
+  def untrack(%MediaLibrary.Profile{} = profile, current_user_id) do
+    Phoenix.Presence.Client.untrack(
+      "proxy:" <> topic(profile),
+      current_user_id
+    )
+  end
+
+  def subscribe(%MediaLibrary.Profile{} = profile) do
+    Phoenix.PubSub.subscribe(@pubsub, topic(profile))
+  end
+
+  def list(%MediaLibrary.Profile{} = profile) do
+    list("proxy:" <> topic(profile))
+  end
+
   def list(topic) do
     @presence.list(topic)
   end
@@ -16,42 +41,21 @@ defmodule LiveBeats.PresenceClient do
 
   @impl Phoenix.Presence.Client
   def handle_join(topic, _key, presence, state) do
-    active_users_topic =
-      topic
-      |> profile_identifier()
-      |> active_users_topic()
-
-    Phoenix.PubSub.local_broadcast(
-      @pubsub,
-      active_users_topic,
-      {__MODULE__, %{user_joined: presence}}
-    )
-
+    local_broadcast(topic, {__MODULE__, %{user_joined: presence}})
     {:ok, state}
   end
 
   @impl Phoenix.Presence.Client
   def handle_leave(topic, _key, presence, state) do
-    active_users_topic =
-      topic
-      |> profile_identifier()
-      |> active_users_topic()
-
-    Phoenix.PubSub.local_broadcast(
-      @pubsub,
-      active_users_topic,
-      {__MODULE__, %{user_left: presence}}
-    )
-
+    local_broadcast(topic, {__MODULE__, %{user_left: presence}})
     {:ok, state}
   end
 
-  defp active_users_topic(user_id) do
-    "active_users:#{user_id}"
+  defp topic(%MediaLibrary.Profile{} = profile) do
+    "active_profiles:#{profile.user_id}"
   end
 
-  defp profile_identifier(topic) do
-    "active_profile:" <> identifier = topic
-    identifier
+  defp local_broadcast("proxy:" <> topic, payload) do
+    Phoenix.PubSub.local_broadcast(@pubsub, topic, payload)
   end
 end
diff --git a/lib/live_beats_web/channels/presence.ex b/lib/live_beats_web/channels/presence.ex
index d203309..a82e228 100644
--- a/lib/live_beats_web/channels/presence.ex
+++ b/lib/live_beats_web/channels/presence.ex
@@ -11,15 +11,30 @@ defmodule LiveBeatsWeb.Presence do
 
   import Phoenix.LiveView.Helpers
   import LiveBeatsWeb.LiveHelpers
-  @pubsub LiveBeats.PubSub
 
-  alias LiveBeats.Accounts
+  alias LiveBeats.{Accounts, MediaLibrary}
+
+  def subscribe(%MediaLibrary.Profile{} = profile) do
+    LiveBeats.PresenceClient.subscribe(profile)
+  end
+
+  def fetch(_topic, presences) do
+    users =
+      presences
+      |> Map.keys()
+      |> Accounts.get_users_map()
+      |> Enum.into(%{})
+
+    for {key, %{metas: metas}} <- presences, into: %{} do
+      {key, %{metas: metas, user: users[String.to_integer(key)]}}
+    end
+  end
 
   def listening_now(assigns) do
     ~H"""
     <!-- users -->
     <div class="px-4 mt-6 sm:px-6 lg:px-8">
-      <h2 class="text-gray-500 text-xs font-medium uppercase tracking-wide">Here now</h2>
+      <h2 class="text-gray-500 text-xs font-medium uppercase tracking-wide">Listening now</h2>
       <ul
         id="listening-now"
         phx-update="prepend"
@@ -41,24 +56,4 @@ defmodule LiveBeatsWeb.Presence do
     </div>
     """
   end
-
-  def fetch(_topic, presences) do
-    users =
-      presences
-      |> Map.keys()
-      |> Accounts.get_users_map()
-      |> Enum.into(%{})
-
-    for {key, %{metas: metas}} <- presences, into: %{} do
-      {key, %{metas: metas, user: users[String.to_integer(key)]}}
-    end
-  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
diff --git a/lib/live_beats_web/live/player_live.ex b/lib/live_beats_web/live/player_live.ex
index 5f0a129..66f3955 100644
--- a/lib/live_beats_web/live/player_live.ex
+++ b/lib/live_beats_web/live/player_live.ex
@@ -142,16 +142,22 @@ defmodule LiveBeatsWeb.PlayerLive do
   defp switch_profile(socket, nil) do
     current_user = Accounts.update_active_profile(socket.assigns.current_user, nil)
 
+    if profile = connected?(socket) and socket.assigns.profile do
+      LiveBeats.PresenceClient.untrack(profile, current_user.id)
+    end
+
     socket
     |> assign(current_user: current_user)
     |> assign_profile(nil)
   end
 
   defp switch_profile(socket, profile_user_id) do
+    %{current_user: current_user} = socket.assigns
     profile = get_profile(profile_user_id)
 
     if profile && connected?(socket) do
-      current_user = Accounts.update_active_profile(socket.assigns.current_user, profile.user_id)
+      current_user = Accounts.update_active_profile(current_user, profile.user_id)
+      LiveBeats.PresenceClient.track(profile, current_user.id)
       send(self(), :play_current)
 
       socket
@@ -258,8 +264,6 @@ defmodule LiveBeatsWeb.PlayerLive do
 
   def handle_info({MediaLibrary, _}, socket), do: {:noreply, socket}
 
-  def handle_info(%{event: "presence_diff"}, socket), do: {:noreply, socket}
-
   defp play_song(socket, %Song{} = song, elapsed) do
     socket
     |> push_play(song, elapsed)
diff --git a/lib/live_beats_web/live/profile_live.ex b/lib/live_beats_web/live/profile_live.ex
index ea4ed5b..d7265f6 100644
--- a/lib/live_beats_web/live/profile_live.ex
+++ b/lib/live_beats_web/live/profile_live.ex
@@ -88,12 +88,6 @@ defmodule LiveBeatsWeb.ProfileLive 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,
-        %{}
-      )
     end
 
     active_song_id =
@@ -259,13 +253,16 @@ defmodule LiveBeatsWeb.ProfileLive do
   end
 
   defp assign_presences(socket) do
-    presences =
-      socket.assigns.profile.user_id
-      |> topic()
-      |> LiveBeats.PresenceClient.list()
-      |> Enum.map(fn {_key, meta} -> meta.user end)
+    if profile = socket.assigns.profile do
+      presences =
+        profile
+        |> LiveBeats.PresenceClient.list()
+        |> Enum.map(fn {_key, meta} -> meta.user end)
 
-    assign(socket, presences: presences)
+      assign(socket, presences: presences)
+    else
+      assign(socket, presences: [])
+    end
   end
 
   defp url_text(nil), do: ""
@@ -274,6 +271,4 @@ defmodule LiveBeatsWeb.ProfileLive do
     uri = URI.parse(url_str)
     uri.host <> uri.path
   end
-
-  defp topic(user_id) when is_integer(user_id), do: "active_profile:#{user_id}"
 end