defmodule PowerAssert do
  defmacro __using__(opts) do
    use_ex_unit = Keyword.get(opts, :use_ex_unit, false)

    case use_ex_unit do
      false ->
        quote do
          use ExUnit.Case, unquote(opts)
          import ExUnit.Assertions, except: [assert: 1, assert: 2]
          import PowerAssert.Assertion
        end

      true ->
        quote do
          require PowerAssert.Assertion

          defmacro power_assert(ast, msg \\ nil) do
            quote do
              PowerAssert.Assertion.assert(unquote(ast), unquote(msg))
            end
          end
        end
    end
  end
end