Ecto cond

ecto_cond.ex

defmodule Ecto.Extension.Query.API do
  defmacro cond_(do: block) do
    bindings =
      Enum.reduce(block, [], fn
        {:->, _, [[clause], branch]}, acc ->
          [branch, clause | acc]
      end)
      |> Enum.reverse()

    bindings_number = length(bindings)

    sql =
      [
        "CASE",
        List.duplicate(" WHEN ? THEN ?", div(bindings_number, 2)),
        " END"
      ]
      |> IO.iodata_to_binary()

    quote do
      fragment(unquote(sql), unquote_splicing(bindings))
    end
  end
end

defmodule QTest do
  import Ecto.Extension.Query.API
  import Ecto.Query

  def test do
    from users in "users",
      select: %{
        email: users.email,
        role_label:
          cond_ do
            users.role == "director" -> "DIRECTOR!"
            true -> type(users.role, :string)
          end
      }
  end
end