defmodule Combo.Inertia.Testing do
  @moduledoc """
  Helpers for testing Inertia responses.
  """

  @doc """
  Gets the Inertia component for given `%Plug.Conn{}`.

  ## Example

      use MyApp.Web.ConnCase
      import Combo.Inertia.Testing

      describe "GET /" do
        test "renders the home page", %{conn: conn} do
          conn = get("/")
          assert inertia_component(conn) == "Home"
        end
      end

  """
  @spec inertia_component(Plug.Conn.t()) :: String.t() | nil
  def inertia_component(conn) do
    page = conn.private[:inertia_page] || %{}
    page[:component]
  end

  @doc """
  Gets the Inertia props for given `%Plug.Conn{}`.

  ## Example

      use MyApp.Web.ConnCase
      import Combo.Inertia.Testing

      describe "GET /" do
        test "renders the home page", %{conn: conn} do
          conn = get("/")
          assert %{user: %{id: 1}} = inertia_props(conn)
        end
      end

  """
  @spec inertia_props(Plug.Conn.t()) :: map() | nil
  def inertia_props(conn) do
    page = conn.private[:inertia_page] || %{}
    page[:props]
  end

  @doc """
  Gets the Inertia errors for given `%Plug.Conn{}`.

  If there are errors available in the current page props, they will be returned.
  Otherwise, errors that have been stored in the session will be retrieved.

  ## Example

      use MyApp.Web.ConnCase
      import Combo.Inertia.Testing

      describe "POST /users" do
        test "fails when name empty", %{conn: conn} do
          conn = post("/users", %{"name" => ""})

          assert %{user: %{id: 1}} = inertia_props(conn)
          assert redirected_to(conn) == ~p"/users"
          assert inertia_errors(conn) == %{"name" => "can't be blank"}
        end
      end

  """
  @spec inertia_errors(Plug.Conn.t()) :: map()
  def inertia_errors(conn) do
    page = conn.private[:inertia_page] || %{}

    case page[:props] do
      %{errors: errors} -> errors
      _ -> Plug.Conn.get_session(conn, "inertia_errors", %{})
    end
  end
end