Add a useful properties others can subscribe to

lib/nerves_hub_link/application.ex

@@ -22,6 +22,12 @@ defmodule NervesHubLink.Application do
     }
 
     children = [
+      {PropertyTable,
+       name: NervesHubLink,
+       properties: [
+         {["status"], :disconnected},
+         {["update_available"], nil}
+       ]},
       {UpdateManager, fwup_config},
       Connection,
       {Socket, config}

lib/nerves_hub_link/connection.ex

@@ -95,6 +95,7 @@ defmodule NervesHubLink.Connection do
   """
   @spec connected() :: :ok
   def connected() do
+    PropertyTable.put(NervesHubLink, ["status"], :connected)
     Agent.update(__MODULE__, fn _ -> {:connected, current_time()} end)
   end
 
@@ -103,6 +104,8 @@ defmodule NervesHubLink.Connection do
   """
   @spec disconnected() :: :ok
   def disconnected() do
+    PropertyTable.put(NervesHubLink, ["status"], :disconnected)
+
     # If we are already in a disconnected state, then don't
     # overwrite the existing value so we can measure from
     # the first point of disconnect

lib/nerves_hub_link/socket.ex

@@ -262,6 +262,8 @@ defmodule NervesHubLink.Socket do
   end
 
   defp handle_join_reply(%{"firmware_url" => url} = update) when is_binary(url) do
+    PropertyTable.put(NervesHubLink, ["update_available"], true)
+
     case NervesHubLinkCommon.Message.UpdateInfo.parse(update) do
       {:ok, %NervesHubLinkCommon.Message.UpdateInfo{} = info} ->
         UpdateManager.apply_update(info)
@@ -272,7 +274,10 @@ defmodule NervesHubLink.Socket do
     end
   end
 
-  defp handle_join_reply(_), do: :noop
+  defp handle_join_reply(_) do
+    PropertyTable.put(NervesHubLink, ["update_available"], false)
+    :noop
+  end
 
   defp maybe_join_console(socket) do
     if socket.assigns.remote_iex do

mix.exs

@@ -103,6 +103,7 @@ defmodule NervesHubLink.MixProject do
       {:nerves_runtime, "~> 0.8"},
       {:nerves_hub_link_common, "~> 0.4"},
       {:nerves_hub_ca_store, "~> 1.0.0"},
+      {:property_table, "~> 0.2"},
       {:slipstream, "~> 1.0 or ~> 0.8"},
       {:x509, "~> 0.5"}
     ]