defmodule MvWeb.MemberLive.IndexPaginationTest do
  @moduledoc """
  §1.7 — Mount loads only one keyset page, not the whole table.
  §1.8 — phx-viewport-bottom fetches and appends the next page; once the last
  page is reached no further fetch is issued.
  """
  use MvWeb.ConnCase, async: false

  import Phoenix.LiveViewTest

  alias Mv.Helpers.SystemActor

  require Ash.Query

  # Matches the :overview default_limit / @page_limit in the LiveView.
  @page_limit 50

  defp seed_members(n) do
    actor = SystemActor.get_system_actor()

    Enum.each(1..n, fn i ->
      # Zero-padded names keep first_name-ascending order deterministic.
      idx = String.pad_leading(Integer.to_string(i), 4, "0")

      {:ok, _} =
        Mv.Membership.create_member(
          %{first_name: "Page#{idx}", last_name: "Member", email: "page#{idx}@example.com"},
          actor: actor
        )
    end)
  end

  defp row_count(html) do
    ~r/<tr[^>]*id="row-/ |> Regex.scan(html) |> length()
  end

  test "mount loads exactly one page when more members exist", %{conn: conn} do
    seed_members(@page_limit + 10)
    conn = conn_with_oidc_user(conn)
    {:ok, _view, html} = live(conn, ~p"/members")

    assert row_count(html) == @page_limit
    # More rows remain, so the infinite-scroll sentinel is armed.
    assert html =~ ~s(phx-viewport-bottom="load_more")
  end

  test "viewport-bottom appends the next page and stops at the last page", %{conn: conn} do
    seed_members(@page_limit + 10)
    conn = conn_with_oidc_user(conn)
    {:ok, view, html} = live(conn, ~p"/members")

    assert row_count(html) == @page_limit

    # Fetch the next page: the remaining rows are appended to the stream.
    html_after = render_hook(view, "load_more", %{})
    assert row_count(html_after) == @page_limit + 10

    # Last page reached: the sentinel is disarmed and a further fetch is a no-op.
    refute html_after =~ ~s(phx-viewport-bottom="load_more")
    html_again = render_hook(view, "load_more", %{})
    assert row_count(html_again) == @page_limit + 10
  end

  test "selecting a row from a later page re-renders it as checked", %{conn: conn} do
    seed_members(@page_limit + 10)
    conn = conn_with_oidc_user(conn)
    {:ok, view, _html} = live(conn, ~p"/members")

    # Load the second page so its rows are in the loaded window.
    render_hook(view, "load_more", %{})

    # The highest-index member sorts last and lives on the second page.
    actor = SystemActor.get_system_actor()

    last_member =
      Mv.Membership.Member
      |> Ash.Query.sort(first_name: :asc)
      |> Ash.read!(actor: actor)
      |> List.last()

    html = render_click(view, "select_member", %{"id" => last_member.id})

    # The re-streamed row for a later-page member reflects the selection.
    assert html =~ ~s(id="row-#{last_member.id}")
    assert has_element?(view, ~s(tr#row-#{last_member.id} input[type="checkbox"][checked]))
  end

  test "single page does not arm the infinite-scroll sentinel", %{conn: conn} do
    seed_members(3)
    conn = conn_with_oidc_user(conn)
    {:ok, _view, html} = live(conn, ~p"/members")

    assert row_count(html) == 3
    refute html =~ ~s(phx-viewport-bottom="load_more")
  end
end