refactor(elixir): hierarchical refactor

to extract common code patterns from
category/storage location systems

lib/components_elixir/inventory/storage_location.ex

@@ -3,9 +3,10 @@ defmodule ComponentsElixir.Inventory.StorageLocation do
   Schema for storage locations with hierarchical organization.
 
   Storage locations can be nested (shelf -> drawer -> box) and each
-  has a unique QR code for quick scanning and identification.
+  has a unique AprilTag for quick scanning and identification.
   """
   use Ecto.Schema
+  use ComponentsElixir.Inventory.HierarchicalSchema
   import Ecto.Changeset
   import Ecto.Query
 
@@ -16,10 +17,6 @@ defmodule ComponentsElixir.Inventory.StorageLocation do
     field :description, :string
     field :apriltag_id, :integer
 
-    # Computed/virtual fields - not stored in database
-    field :level, :integer, virtual: true
-    field :path, :string, virtual: true
-
     # Only parent relationship is stored
     belongs_to :parent, StorageLocation
     has_many :children, StorageLocation, foreign_key: :parent_id
@@ -37,47 +34,26 @@ defmodule ComponentsElixir.Inventory.StorageLocation do
     |> validate_length(:description, max: 500)
     |> validate_apriltag_id()
     |> foreign_key_constraint(:parent_id)
-    |> validate_no_circular_reference()
     |> put_apriltag_id()
   end
 
-  # Prevent circular references (location being its own ancestor)
-  defp validate_no_circular_reference(changeset) do
-    case get_change(changeset, :parent_id) do
-      nil -> changeset
-      parent_id ->
-        location_id = changeset.data.id
-        if location_id && would_create_cycle?(location_id, parent_id) do
-          add_error(changeset, :parent_id, "cannot be a descendant of this location")
-        else
-          changeset
-        end
-    end
+  # HierarchicalSchema implementations
+  @impl true
+  def full_path(%StorageLocation{} = storage_location) do
+    Hierarchical.full_path(storage_location, &(&1.parent), path_separator())
   end
 
-  defp would_create_cycle?(location_id, parent_id) do
-    # Check if parent_id is the same as location_id or any of its descendants
-    location_id == parent_id or
-    (parent_id && is_descendant_of?(parent_id, location_id))
-  end
+  @impl true
+  def parent(%StorageLocation{parent: parent}), do: parent
 
-  defp is_descendant_of?(potential_descendant, ancestor_id) do
-    case ComponentsElixir.Repo.get(StorageLocation, potential_descendant) do
-      nil -> false
-      %{parent_id: nil} -> false
-      %{parent_id: ^ancestor_id} -> true
-      %{parent_id: parent_id} -> is_descendant_of?(parent_id, ancestor_id)
-    end
-  end
+  @impl true
+  def children(%StorageLocation{children: children}), do: children
 
-  @doc """
-  Returns the full hierarchical path as a human-readable string.
-  """
-  def full_path(storage_location) do
-    storage_location.path
-    |> String.split("/")
-    |> Enum.join(" → ")
-  end
+  @impl true
+  def path_separator(), do: " / "
+
+  @impl true
+  def entity_type(), do: :storage_location
 
   @doc """
   Returns the AprilTag format for this storage location.
@@ -102,28 +78,6 @@ defmodule ComponentsElixir.Inventory.StorageLocation do
     end
   end
 
-  # Compute the hierarchy level based on parent chain
-  def compute_level(%StorageLocation{parent_id: nil}), do: 0
-  def compute_level(%StorageLocation{parent: %StorageLocation{} = parent}) do
-    compute_level(parent) + 1
-  end
-  def compute_level(%StorageLocation{parent_id: parent_id}) when not is_nil(parent_id) do
-    # Parent not loaded, fetch it
-    parent = ComponentsElixir.Inventory.get_storage_location!(parent_id)
-    compute_level(parent) + 1
-  end
-
-  # Compute the full path based on parent chain
-  def compute_path(%StorageLocation{name: name, parent_id: nil}), do: name
-  def compute_path(%StorageLocation{name: name, parent: %StorageLocation{} = parent}) do
-    "#{compute_path(parent)}/#{name}"
-  end
-  def compute_path(%StorageLocation{name: name, parent_id: parent_id}) when not is_nil(parent_id) do
-    # Parent not loaded, fetch it
-    parent = ComponentsElixir.Inventory.get_storage_location!(parent_id)
-    "#{compute_path(parent)}/#{name}"
-  end
-
   defp get_next_available_apriltag_id do
     # Get all used AprilTag IDs
     used_ids = ComponentsElixir.Repo.all(