refactor(appengine): add custom DateTime type

default Ecto types only allow full second or microsecond precision,
but cql timestamps use millisecond precision. To avoid precision errors,
a new Ecto DateTime type has been created, which allows millisecond
precision (althogh no check is made: Xandra handles that itself).

this change reverts some changes made to the tests in
b27c5a4, restoring the millisecond
precision of the device status

Signed-off-by: Francesco Noacco <francesco.noacco@secomind.com>

Author: noaccOS

apps/astarte_appengine_api/lib/astarte_appengine_api/datetime.ex

@@ -0,0 +1,43 @@
+#
+# This file is part of Astarte.
+#
+# Copyright 2025 SECO Mind Srl
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+defmodule Astarte.AppEngine.API.DateTime do
+  @moduledoc """
+  Ecto type for DateTimes with millisecond precision.
+  """
+  use Ecto.Type
+
+  @type t :: DateTime.t()
+
+  @doc false
+  def type, do: :utc_datetime_msec
+
+  @spec load(t() | any()) :: {:ok, t()} | :error
+  def load(%DateTime{} = datetime), do: {:ok, datetime}
+  def load(timestamp) when is_integer(timestamp), do: {:ok, DateTime.from_unix!(timestamp)}
+  def load(_other), do: :error
+
+  # xandra accepts both integers and datetimes, it can do the job for us
+  @spec dump(t() | any()) :: {:ok, t()} | :error
+  def dump(%DateTime{} = datetime), do: {:ok, datetime}
+  def dump(timestamp) when is_integer(timestamp), do: {:ok, timestamp}
+  def dump(_other), do: :error
+
+  @spec cast(t() | any()) :: {:ok, t()} | :error
+  def cast(datetime_or_timestamp_or_any), do: load(datetime_or_timestamp_or_any)
+end

apps/astarte_appengine_api/lib/astarte_appengine_api/devices/device.ex

@@ -18,6 +18,7 @@
 
 defmodule Astarte.AppEngine.API.Devices.Device do
   use TypedEctoSchema
+  alias Astarte.AppEngine.API.DateTime, as: DateTimeMs
   alias Astarte.AppEngine.API.UUID
 
   @primary_key {:device_id, UUID, autogenerate: false}
@@ -39,16 +40,16 @@ defmodule Astarte.AppEngine.API.Devices.Device do
       types: [:string, :integer],
       value: :integer
 
-    field :first_credentials_request, :utc_datetime_usec
-    field :first_registration, :utc_datetime_usec
+    field :first_credentials_request, DateTimeMs
+    field :first_registration, DateTimeMs
     field :groups, Exandra.Map, key: :string, value: UUID
     field :inhibit_credentials_request, :boolean
     field :introspection, Exandra.Map, key: :string, value: :integer
     field :introspection_minor, Exandra.Map, key: :string, value: :integer
-    field :last_connection, :utc_datetime_usec
+    field :last_connection, DateTimeMs
     field :last_credentials_request_ip, Exandra.Inet
 
-    field :last_disconnection, :utc_datetime_usec
+    field :last_disconnection, DateTimeMs
     field :last_seen_ip, Exandra.Inet
 
     field :old_introspection,

apps/astarte_appengine_api/lib/astarte_appengine_api/realms/individual_property.ex

@@ -18,31 +18,32 @@
 
 defmodule Astarte.AppEngine.API.Realms.IndividualProperty do
   use TypedEctoSchema
+  alias Astarte.AppEngine.API.DateTime, as: DateTimeMs
   alias Astarte.AppEngine.API.UUID
 
   @primary_key false
   typed_schema "individual_properties" do
-    field :reception, :utc_datetime_usec, virtual: true
+    field :reception, DateTimeMs, virtual: true
     field :device_id, UUID, primary_key: true
     field :interface_id, UUID, primary_key: true
     field :endpoint_id, UUID, primary_key: true
     field :path, :string, primary_key: true
-    field :reception_timestamp, :utc_datetime_usec
+    field :reception_timestamp, DateTimeMs
     field :reception_timestamp_submillis, :integer
     field :double_value, :float
     field :integer_value, :integer
     field :boolean_value, :boolean
     field :longinteger_value, :integer
     field :string_value, :string
     field :binaryblob_value, :binary
-    field :datetime_value, :utc_datetime_usec
+    field :datetime_value, DateTimeMs
     field :doublearray_value, {:array, :float}
     field :integerarray_value, {:array, :integer}
     field :booleanarray_value, {:array, :boolean}
     field :longintegerarray_value, {:array, :integer}
     field :stringarray_value, {:array, :string}
     field :binaryblobarray_value, {:array, :binary}
-    field :datetimearray_value, {:array, :utc_datetime_usec}
+    field :datetimearray_value, {:array, DateTimeMs}
   end
 
   def reception(individual_property) do