add presence client

lib/live_beats/application.ex

@@ -20,9 +20,10 @@ defmodule LiveBeats.Application do
       #start presence
       LiveBeatsWeb.Presence,
       # Start the Endpoint (http/https)
-      LiveBeatsWeb.Endpoint
+      LiveBeatsWeb.Endpoint,
       # Start a worker by calling: LiveBeats.Worker.start_link(arg)
       # {LiveBeats.Worker, arg}
+      {Phoenix.Presence.Client, client: LiveBeats.PresenceClient, pubsub: LiveBeats.PubSub, presence: LiveBeats.Presence}
     ]
 
     # See https://hexdocs.pm/elixir/Supervisor.html

lib/live_beats/presence/phoenix_presence_client.ex

@@ -0,0 +1,85 @@
+defmodule Phoenix.Presence.Client do
+  use GenServer
+
+  @doc """
+  TODO
+
+  ## Options
+
+    * `:pubsub` - The required name of the pubsub server
+    * `:presence` - The required name of the presence module
+    * `:client` - The required callback module
+  """
+  def start_link(opts) do
+    GenServer.start_link(__MODULE__, opts, name: PresenceClient)
+  end
+
+  def track(topic, key, meta) do
+    GenServer.call(PresenceClient, {:track, self(), topic, key, meta})
+  end
+
+  def untrack(topic, key) do
+    GenServer.call(PresenceClient, {:untrack, self(), topic, key})
+  end
+
+  def init(opts) do
+    client = Keyword.fetch!(opts, :client)
+    client_state = client.init(%{})
+
+    state = %{
+      topics: %{},
+      client: client,
+      pubsub: Keyword.fetch!(opts, :pubsub),
+      presence_mod: Keyword.fetch!(opts, :presence),
+      client_state: client_state
+    }
+
+    {:ok, state}
+  end
+
+  def handle_info(%{topic: topic, event: "presence_diff", payload: diff}, state) do
+    {:noreply, merge_diff(state, topic, diff)}
+  end
+
+  def handle_call({:track, pid, topic, key, meta}, _from, state) do
+    {:reply, :ok, track_pid(state, pid, topic, key, meta)}
+  end
+
+  def handle_call({:untrack, pid, topic, key}, _from, state) do
+    {:reply, :ok, untrack_pid(state, pid, topic, key)}
+  end
+
+  defp track_pid(state, pid, topic, key, meta) do
+    case Map.fetch(state.topics, topic) do
+      {:ok, presences} ->
+        state.presence_mod.track(pid, topic, key, meta)
+        # update topics state...
+        # new_state
+        state
+
+      :error ->
+        # subscribe to topic we weren't yet tracking
+        Phoenix.PubSub.subscribe(state.pubsub, topic)
+        # new_state
+        state
+    end
+  end
+
+  defp untrack_pid(state, pid, topic, key) do
+    state.presence_mod.untrack(pid, topic, key)
+    # remove presence from state.topics
+    # if no more presences for given topic, unsubscribe
+    #   Phoenix.PubSub.unsubscribe(state.pubsub, topic)
+    # new_state
+    state
+  end
+
+  defp merge_diff(state, topic, diff) do
+    # merge diff into state.topics
+    # invoke state.client.handle_join|handle_leave
+    # if no more presences for given topic, unsubscribe
+    #   Phoenix.PubSub.unsubscribe(state.pubsub, topic)
+    # new_state
+    state
+  end
+end

lib/live_beats/presence/presence_client.ex

@@ -0,0 +1,28 @@
+defmodule LiveBeats.PresenceClient do
+  @behaviour Phoenix.Presence.Client
+
+  @presence LiveBeats.Presence
+
+  def start_link(opts) do
+    Phoenix.Presence.Client.start_link(presence: @presence, client: __MODULE__)
+  end
+
+  def list(topic) do
+    @presence.list(topic)
+  end
+
+  def init(_opts) do
+    # user-land state
+    {:ok, %{}}
+  end
+
+  def handle_join(key, presence, state) do
+    # can local pubsub to LVs about new join
+    {:ok, state}
+  end
+
+  def handle_leave(key, presence, state) do
+    # can local pubsub to LVs about new leave
+    {:ok, state}
+  end
+end

lib/live_beats_web/live/profile_live.ex

@@ -87,11 +87,9 @@ defmodule LiveBeatsWeb.ProfileLive do
     if connected?(socket) do
       MediaLibrary.subscribe_to_profile(profile)
       Accounts.subscribe(current_user.id)
-      LiveBeatsWeb.Presence.track(
-        self(),
-        topic(profile.user_id),
+      Phoenix.Presence.Client.track(topic(profile.user_id),
         current_user.id,
-        current_user
+        %{}
       )
     end