Record when admin views a chatroom and send more events.

We expect "previousRoom" and "nextRoom" in the payload
when a user joins a room topic. We use this to record
a timestamp of when admin has viewed both rooms. This
means we record when an admin both leaves a previous
room and joins a new room.

We then publish two more events every time an
anonymous user sends a message. The "lobby_list" event
for updating the user's last message sent and timestamp
and the "notifications" event for triggering browser
notifications. We'll get into more detail on that
once we work on the frontend.

Author: gjaldon

web/channels/room_channel.ex

@@ -11,15 +11,19 @@ defmodule PhoenixChat.RoomChannel do
         |> Repo.all
         |> Enum.map(&message_payload/1)
         |> Enum.reverse
-      send(self, :after_join)
+      send(self, {:after_join, payload})
       {:ok, %{messages: messages}, socket}
     end)
   end
 
-  def handle_info(:after_join, socket) do
+  def handle_info({:after_join, payload}, socket) do
     # We create the anonymous user in our DB if its `uuid` does not match
     # any existing record.
     get_or_create_anonymous_user!(socket)
+
+    # We record when admin views a room
+    update_last_viewed_at(payload["previousRoom"])
+    update_last_viewed_at(payload["nextRoom"])
     {:noreply, socket}
   end
 
@@ -30,21 +34,56 @@ defmodule PhoenixChat.RoomChannel do
     changeset = Message.changeset(%Message{}, payload)
 
     case Repo.insert(changeset) do
+      # This branch gets triggered when a message is sent by an anonymous user
+      {:ok, %{anonymous_user_id: uuid} = message} when not is_nil(uuid) ->
+        user = Repo.preload(message, :anonymous_user).anonymous_user
+        message_payload = message_payload(message, user)
+        broadcast! socket, "message", message_payload
+
+        # Apart from sending the message, we want to update the lobby list
+        # with the last message sent by the user and its timestamp
+        Endpoint.broadcast_from! self, "admin:active_users",
+          "lobby_list", user_payload({user, message})
+
+        # We also send the message via the "notifications" event. This event
+        # will be listened to in the frontend and will publish an Notification
+        # via the browser when admin is not viewing the sender's chatroom.
+        Endpoint.broadcast_from! self, "admin:active_users",
+          "notifications", message_payload
+
+      # This branch gets triggered when a message is sent by admin
       {:ok, message} ->
-        payload = message_payload(message)
-        broadcast! socket, "message", payload
-        {:reply, :ok, socket}
+        broadcast! socket, "message", message_payload(message)
       {:error, changeset} ->
         {:reply, {:error, %{errors: changeset}}, socket}
     end
   end
 
-  defp message_payload(message) do
-    from = message.user_id || message.from
+  defp update_last_viewed_at(nil), do: nil #noop
+
+  defp update_last_viewed_at(uuid) do
+    user = Repo.get(AnonymousUser, uuid)
+    changeset = AnonymousUser.last_viewed_changeset(user)
+    user = Repo.update!(changeset)
+    Endpoint.broadcast_from! self, "admin:active_users",
+      "lobby_list", user_payload(user)
+  end
+
+  defp message_payload(%{anonymous_user_id: nil} = message) do
+    %{body: message.body,
+      timestamp: message.timestamp,
+      room: message.room,
+      from: message.user_id,
+      id: message.id}
+  end
+
+  defp message_payload(message, user \\ nil) do
+    user = user || Repo.preload(message, :anonymous_user).anonymous_user
     %{body: message.body,
       timestamp: message.timestamp,
       room: message.room,
-      from: from,
+      from: user.name,
+      uuid: user.id,
       id: message.id}
   end
 end