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 AprilTag for quick scanning and identification.
  """
  use Ecto.Schema
  use ComponentsElixir.Inventory.HierarchicalSchema
  import Ecto.Changeset
  import Ecto.Query

  alias ComponentsElixir.Inventory.{StorageLocation, Component}

  schema "storage_locations" do
    field :name, :string
    field :description, :string
    field :apriltag_id, :integer

    # 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, :apriltag_id])
    |> validate_required([:name])
    |> validate_length(:name, min: 1, max: 100)
    |> validate_length(:description, max: 500)
    |> validate_apriltag_id()
    |> foreign_key_constraint(:parent_id)
    |> put_apriltag_id()
  end

  # HierarchicalSchema implementations
  @impl true
  def full_path(%StorageLocation{} = storage_location) do
    Hierarchical.full_path(storage_location, &(&1.parent), path_separator())
  end

  @impl true
  def parent(%StorageLocation{parent: parent}), do: parent

  @impl true
  def children(%StorageLocation{children: children}), do: children

  @impl true
  def path_separator(), do: " / "

  @impl true
  def entity_type(), do: :storage_location

  @doc """
  Returns the AprilTag format for this storage location.
  Returns the AprilTag ID that corresponds to this location.
  """
  def apriltag_format(storage_location) do
    storage_location.apriltag_id
  end

  # Private functions for changeset processing

  defp validate_apriltag_id(changeset) do
    changeset
    |> validate_number(:apriltag_id, greater_than_or_equal_to: 0, less_than_or_equal_to: 586)
    |> unique_constraint(:apriltag_id, message: "AprilTag ID is already in use")
  end

  defp put_apriltag_id(changeset) do
    case get_field(changeset, :apriltag_id) do
      nil -> put_change(changeset, :apriltag_id, get_next_available_apriltag_id())
      _ -> changeset
    end
  end

  defp get_next_available_apriltag_id do
    # Get all used AprilTag IDs
    used_ids = ComponentsElixir.Repo.all(
      from sl in ComponentsElixir.Inventory.StorageLocation,
      where: not is_nil(sl.apriltag_id),
      select: sl.apriltag_id
    )

    # Find the first available ID (0-586)
    0..586
    |> Enum.find(&(&1 not in used_ids))
    |> case do
      nil ->
        # All IDs are used - this should be handled at the application level
        raise "All AprilTag IDs are in use"
      id -> id
    end
  end
end