defmodule Aprsme.ShutdownHandlerTest do
  # async: false — shares app env and the named ShutdownHandler process.
  use ExUnit.Case, async: false

  alias Aprsme.ShutdownHandler

  describe "handle_call(:shutting_down?, _, state)" do
    test "reflects the shutting_down flag in state" do
      # Pure callback invocation — no side effects.
      assert {:reply, false, %{shutting_down: false}} =
               ShutdownHandler.handle_call(:shutting_down?, self(), %{
                 shutting_down: false,
                 drain_timeout: 0
               })

      assert {:reply, true, %{shutting_down: true}} =
               ShutdownHandler.handle_call(:shutting_down?, self(), %{
                 shutting_down: true,
                 drain_timeout: 0
               })
    end
  end

  describe "handle_call(:shutdown, _, state)" do
    test "returns :already_shutting_down when already in progress" do
      state = %{shutting_down: true, drain_timeout: 0}

      assert {:reply, :already_shutting_down, ^state} =
               ShutdownHandler.handle_call(:shutdown, self(), state)
    end
  end

  describe "handle_info({:EXIT, pid, reason}, state)" do
    test "is a no-op that keeps state intact" do
      state = %{shutting_down: false, drain_timeout: 0}

      assert {:noreply, ^state} =
               ShutdownHandler.handle_info({:EXIT, self(), :normal}, state)
    end
  end

  describe "shutting_down?/0 without the GenServer running" do
    test "returns false via the rescue clause" do
      # The supervised ShutdownHandler may or may not be running. If the
      # GenServer.call raises, the `rescue _ -> false` kicks in and we get
      # a boolean back either way.
      assert is_boolean(ShutdownHandler.shutting_down?())
    end
  end
end