defmodule BlogexTest do
  @moduledoc """
  Behaviour tests for the `Blogex` facade.

  The facade is a thin delegating layer over `Blogex.Registry`, but callers
  (Phoenix controllers, LiveViews) only ever see the answers, so these tests
  assert the answers: the exact module lists, post orderings and tag sets the
  fixtures imply. Asserting `Blogex.x() == Blogex.Registry.x()` would pin the
  delegation instead of the behaviour and would keep passing if both sides
  drifted together.

  Non-async: the registry is configured through the process-global `:blogex`
  application env.
  """
  use ExUnit.Case

  alias Blogex.Test.{AlphaBlog, BetaBlog}

  setup do
    Application.put_env(:blogex, :blogs, [AlphaBlog, BetaBlog])
    on_exit(fn -> Application.delete_env(:blogex, :blogs) end)
  end

  describe "blogs/0" do
    test "returns the configured blog modules" do
      assert Blogex.blogs() == [AlphaBlog, BetaBlog]
    end
  end

  describe "get_blog!/1 and get_blog/1" do
    test "return the module registered for a blog_id" do
      assert Blogex.get_blog!(:alpha) == AlphaBlog
      assert Blogex.get_blog(:beta) == BetaBlog
    end

    test "an unknown blog_id returns nil and raises" do
      assert Blogex.get_blog(:nope) == nil

      assert_raise Blogex.NotFoundError, fn -> Blogex.get_blog!(:nope) end
    end
  end

  describe "all_posts/0" do
    # Newest first across both blogs: beta's 2026-03-15 post, then alpha's
    # 2026-03-01. Drafts (a-draft) and future-dated posts (b-future) are not
    # visible to readers, so neither appears.
    test "merges published posts from every blog, newest first" do
      assert ids(Blogex.all_posts()) == ["b1", "a1"]
    end
  end

  describe "all_posts_unfiltered/0" do
    # Everything, newest first: the 2099 scheduled post, then b1, the alpha
    # draft, and alpha's oldest.
    test "includes drafts and future-dated posts, newest first" do
      assert ids(Blogex.all_posts_unfiltered()) == ["b-future", "b1", "a-draft", "a1"]
    end
  end

  describe "all_tags/0" do
    test "returns the unique tags across blogs, sorted" do
      assert Blogex.all_tags() == ["devops", "elixir"]
    end
  end

  defp ids(posts), do: Enum.map(posts, & &1.id)
end