field from assignment calculation

lib/diffo/provider/components/calculations/field_from_assignment.ex

@@ -0,0 +1,35 @@
+# SPDX-FileCopyrightText: 2025 diffo contributors <https://github.com/diffo-dev/diffo/graphs.contributors>
+#
+# SPDX-License-Identifier: MIT
+
+defmodule Diffo.Provider.Calculations.FieldFromAssignment do
+  @moduledoc false
+  use Ash.Resource.Calculation
+
+  @impl true
+  def load(_query, _opts, _context), do: []
+
+  @impl true
+  def calculate(records, opts, _context) do
+    alias_name = opts[:alias]
+    field = opts[:field]
+
+    Enum.map(records, fn record ->
+      record.id
+      |> assignments(alias_name)
+      |> Enum.map(&Map.get(&1, field))
+    end)
+  end
+
+  defp assignments(id, nil) do
+    Diffo.Provider.AssignmentRelationship
+    |> Ash.Query.filter_input(target_id: id)
+    |> Ash.read!(domain: Diffo.Provider)
+  end
+
+  defp assignments(id, alias_name) do
+    Diffo.Provider.AssignmentRelationship
+    |> Ash.Query.filter_input(target_id: id, alias: alias_name)
+    |> Ash.read!(domain: Diffo.Provider)
+  end
+end

test/provider/extension/field_from_assignment_test.exs

@@ -0,0 +1,124 @@
+# SPDX-FileCopyrightText: 2025 diffo contributors <https://github.com/diffo-dev/diffo/graphs.contributors>
+#
+# SPDX-License-Identifier: MIT
+
+defmodule Diffo.Provider.Extension.FieldFromAssignmentTest do
+  @moduledoc false
+  use ExUnit.Case, async: true
+  @moduletag :domain_extended
+
+  alias Diffo.Provider.Assignment
+  alias Diffo.Test.Servo
+
+  setup do
+    AshNeo4j.Sandbox.checkout()
+    on_exit(&AshNeo4j.Sandbox.rollback/0)
+  end
+
+  defp setup_card do
+    updates = [
+      card: [family: :ISAM, model: "EBLT48", technology: :adsl2Plus],
+      ports: [first: 1, last: 48, assignable_type: "ADSL2+"]
+    ]
+
+    {:ok, card} = Servo.build_card(%{})
+    {:ok, card} = Servo.define_card(card, %{characteristic_value_updates: updates})
+    {:ok, card} = Servo.lifecycle_card(card, %{resource_state: :operating})
+    card
+  end
+
+  describe "FieldFromAssignment — aliased" do
+    test "returns field value from the aliased assignment record" do
+      card = setup_card()
+      {:ok, service} = Servo.build_access_service(%{})
+
+      {:ok, _card} =
+        Servo.assign_port(card, %{
+          assignment: %Assignment{
+            assignee_id: service.id,
+            operation: :auto_assign,
+            alias: :primary
+          }
+        })
+
+      service = Ash.load!(service, [:assigned_port], domain: Servo)
+
+      assert length(service.assigned_port) == 1
+      assert hd(service.assigned_port) == 1
+    end
+
+    test "returns empty list when no assignment exists" do
+      {:ok, service} = Servo.build_access_service(%{})
+
+      service = Ash.load!(service, [:assigned_port], domain: Servo)
+
+      assert service.assigned_port == []
+    end
+
+    test "alias filters to only the matching assignment record" do
+      card_a = setup_card()
+      card_b = setup_card()
+      {:ok, service} = Servo.build_access_service(%{})
+
+      {:ok, _card_a} =
+        Servo.assign_port(card_a, %{
+          assignment: %Assignment{
+            assignee_id: service.id,
+            operation: :auto_assign,
+            alias: :primary
+          }
+        })
+
+      {:ok, _card_b} =
+        Servo.assign_port(card_b, %{
+          assignment: %Assignment{
+            assignee_id: service.id,
+            operation: :auto_assign,
+            alias: :secondary
+          }
+        })
+
+      service = Ash.load!(service, [:assigned_port], domain: Servo)
+
+      assert length(service.assigned_port) == 1
+    end
+  end
+
+  describe "FieldFromAssignment — unaliased (all assignments)" do
+    test "returns field values from all assignment records" do
+      card_a = setup_card()
+      card_b = setup_card()
+      {:ok, service} = Servo.build_access_service(%{})
+
+      {:ok, _card_a} =
+        Servo.assign_port(card_a, %{
+          assignment: %Assignment{
+            assignee_id: service.id,
+            operation: :auto_assign,
+            alias: :primary
+          }
+        })
+
+      {:ok, _card_b} =
+        Servo.assign_port(card_b, %{
+          assignment: %Assignment{
+            assignee_id: service.id,
+            operation: :auto_assign,
+            alias: :secondary
+          }
+        })
+
+      service = Ash.load!(service, [:all_assignment_values], domain: Servo)
+
+      assert length(service.all_assignment_values) == 2
+    end
+
+    test "returns empty list when no assignments exist" do
+      {:ok, service} = Servo.build_access_service(%{})
+
+      service = Ash.load!(service, [:all_assignment_values], domain: Servo)
+
+      assert service.all_assignment_values == []
+    end
+  end
+end

test/support/resource/instance/access_service.ex

@@ -45,6 +45,12 @@ defmodule Diffo.Test.Instance.AccessService do
 
     calculate :assigner_names, {:array, :string},
       {Diffo.Provider.Calculations.FieldViaAssignedRelationship, [field: :name]}
+
+    calculate :assigned_port, {:array, :integer},
+      {Diffo.Provider.Calculations.FieldFromAssignment, [alias: :primary, field: :value]}
+
+    calculate :all_assignment_values, {:array, :integer},
+      {Diffo.Provider.Calculations.FieldFromAssignment, [field: :value]}
   end
 
   actions do