Add "Never Connected" and "Disconnected" fields

apps/astarte_appengine_api/lib/astarte_appengine_api/stats/devices_stats.ex

@@ -19,6 +19,8 @@
 defmodule Astarte.AppEngine.API.Stats.DevicesStats do
   defstruct [
     :total_devices,
-    :connected_devices
+    :connected_devices,
+    :disconnected_devices,
+    :never_connected_devices
   ]
 end

apps/astarte_appengine_api/lib/astarte_appengine_api/stats/queries.ex

@@ -25,10 +25,14 @@ defmodule Astarte.AppEngine.API.Stats.Queries do
   def get_devices_stats(realm) do
     Xandra.Cluster.run(:xandra, fn conn ->
       with {:ok, total_devices_count} <- get_total_devices_count(conn, realm),
-           {:ok, connected_devices_count} <- get_connected_devices_count(conn, realm) do
+           {:ok, connected_devices_count} <- get_connected_devices_count(conn, realm),
+           {:ok, disconnected_devices_count} <- get_disconnected_devices_count(conn, realm),
+           {:ok, never_connected_devices_count} <- get_never_connected_devices_count(conn, realm) do
         stats = %DevicesStats{
           total_devices: total_devices_count,
-          connected_devices: connected_devices_count
+          connected_devices: connected_devices_count,
+          disconnected_devices: disconnected_devices_count,
+          never_connected_devices: never_connected_devices_count
         }
 
         {:ok, stats}
@@ -71,6 +75,40 @@ defmodule Astarte.AppEngine.API.Stats.Queries do
     end
   end
 
+
+  defp get_disconnected_devices_count(conn, realm) do
+    query = """
+    SELECT count(device_id)
+    FROM :realm.devices
+    WHERE connected=false
+    ALLOW FILTERING
+    """
+
+    with {:ok, prepared} <- prepare_with_realm(conn, realm, query),
+         {:ok, %Xandra.Page{} = page} <- Xandra.execute(conn, prepared, %{}) do
+      [%{"system.count(device_id)" => count}] = Enum.to_list(page)
+
+      {:ok, count}
+    end
+  end
+
+  defp get_never_connected_devices_count(conn, realm) do
+    query = """
+    SELECT device_id, last_connection
+    FROM :realm.devices
+    """
+
+    with {:ok, prepared} <- prepare_with_realm(conn, realm, query),
+         {:ok, %Xandra.Page{} = page} <- Xandra.execute(conn, prepared, %{}) do
+      devices = Enum.to_list(page)
+      never_connected_count = devices
+      |> Enum.filter(fn %{"last_connection" => nil} -> true; _ -> false end)
+      |> length()
+
+      {:ok, never_connected_count}
+    end
+  end
+
   # TODO: copypasted from Groups.Queries, this is going to be moved to Astarte.DataAccess
   # when we move everything to Xandra
   defp prepare_with_realm(conn, realm_name, query) do

apps/astarte_appengine_api/lib/astarte_appengine_api_web/views/stats_view.ex

@@ -27,7 +27,9 @@ defmodule Astarte.AppEngine.APIWeb.StatsView do
   def render("devices_stats.json", %{devices_stats: devices_stats}) do
     %{
       total_devices: devices_stats.total_devices,
-      connected_devices: devices_stats.connected_devices
+      connected_devices: devices_stats.connected_devices,
+      disconnected_devices: devices_stats.disconnected_devices,
+      never_connected_devices: devices_stats.never_connected_devices
     }
   end
 end