defmodule Pointers.Schema do
  @moduledoc "Some macros to help you define schemas."

  defmacro __using__(_) do
    quote do
      use Ecto.Schema
      import Pointers.Schema
    end
  end

  @doc """
  Defines a schema that can be pointed to - one keyed by autogenerated
  ULID that you promise to have run the corresponding migrations for.

  Takes a ULID in text form which is a sentinel value used to identify
  the table. It *must* match the one inserted into `Table` in the
  migrations that create this table.
  """
  defmacro pointable_schema(table, id, autogenerate \\ true, body) do
    Pointers.ULID.cast!(id)
    quote do
      Pointers.Schema.ulid_schema(unquote(table), unquote(autogenerate), unquote(body))
      def table_id(), do: unquote(id)
    end
  end

  @doc """
  Define a trait schema - one that keyed by ULID, is not pointable and
  does not autogenerate IDs. Takes a trait name (atom) which will be
  used to autogenerate alias names *sigh*
  """
  defmacro trait_schema(table, name, body) when is_atom(name) do
    quote do
      Pointers.Schema.ulid_schema(unquote(table), false, unquote(body))
    end
  end

  @doc """
  Define a table schema with a ULID as a primary key but that is not
  participating in the pointers abstraction.
  """
  defmacro ulid_schema(table, autogenerate \\ true, body) do
    quote do
      @primary_key {:id, Pointers.ULID, autogenerate: unquote(autogenerate)}
      @foreign_key_type Pointers.ULID
      @timestamps_opts [type: :utc_datetime_usec, inserted_at: false]
      schema(unquote(table), unquote(body))
    end
  end

end