feat(elixir): storage location system

lib/components_elixir/inventory/storage_location.ex

@@ -0,0 +1,133 @@
+defmodule ComponentsElixir.Inventory.StorageLocation do
+  @moduledoc """
+  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.
+  """
+  use Ecto.Schema
+  import Ecto.Changeset
+
+  alias ComponentsElixir.Inventory.{StorageLocation, Component}
+
+  schema "storage_locations" do
+    field :name, :string
+    field :description, :string
+    field :qr_code, :string
+    field :is_active, :boolean, default: true
+
+    # 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
+    has_many :components, Component
+
+    timestamps()
+  end
+
+    @doc false
+  def changeset(storage_location, attrs) do
+    storage_location
+    |> cast(attrs, [:name, :description, :parent_id, :is_active])
+    |> validate_required([:name])
+    |> validate_length(:name, min: 1, max: 100)
+    |> validate_length(:description, max: 500)
+    |> foreign_key_constraint(:parent_id)
+    |> validate_no_circular_reference()
+    |> put_qr_code()
+  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
+  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
+
+  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
+
+  @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
+
+  @doc """
+  Returns the QR code format for this storage location.
+  Format: SL:{level}:{qr_code}:{parent_qr_or_ROOT}
+  """
+  def qr_format(storage_location, parent \\ nil) do
+    parent_code = if parent, do: parent.qr_code, else: "ROOT"
+    "SL:#{storage_location.level}:#{storage_location.qr_code}:#{parent_code}"
+  end
+
+  # Private functions for changeset processing
+
+  defp put_qr_code(changeset) do
+    case get_field(changeset, :qr_code) do
+      nil -> put_change(changeset, :qr_code, generate_qr_code())
+      _ -> changeset
+    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 generate_qr_code do
+    # Generate a unique 6-character alphanumeric code
+    chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
+
+    1..6
+    |> Enum.map(fn _ ->
+      chars
+      |> String.graphemes()
+      |> Enum.random()
+    end)
+    |> Enum.join()
+  end
+end