Phoenix Liveview Auth

# Bad — excluding Phoenix.Controller breaks the plug functions,
# which need plain redirect/2 and put_flash/3
import Phoenix.LiveView
import Phoenix.Controller, except: [redirect: 2, put_flash: 3]

# Good — import Phoenix.Controller normally for the plugs;
# fully qualify inside on_mount hooks instead
import Phoenix.Controller

def on_mount(:require_authenticated_user, _params, session, socket) do
  # ...
  Phoenix.LiveView.redirect(socket, to: ~p"/")
  Phoenix.LiveView.put_flash(socket, :error, "...")
end

def require_authenticated_user(conn, _opts) do
  # plain redirect/2 and put_flash/3 here come from Phoenix.Controller
  conn |> put_flash(:error, "...") |> redirect(to: ~p"/users/log-in")
end

# Phoenix 1.8+ pattern — Scope struct
defmodule MyApp.Scope do
  defstruct [:user]
end

# In LiveView — access user through scope
def mount(_params, _session, socket) do
  user = socket.assigns.current_scope.user
  {:ok, assign(socket, :posts, Posts.list_posts(user))}
end

# In templates — @current_scope is always assigned once on_mount has
# run, so dot access is safe; guard .user since the scope may wrap no user
<%= if @current_scope && @current_scope.user do %>
  <p>Welcome, <%= @current_scope.user.email %></p>
<% end %>

# Bad — crashes when current_scope.user is nil (guest visitor)
<%= @current_scope.user.email %>

# Good — guard .user, not the current_scope lookup
<%= if @current_scope && @current_scope.user do %>
  <%= @current_scope.user.email %>
<% end %>

<%= if assigns[:current_scope] && @current_scope.user do %>
  <%= @current_scope.user.email %>
<% end %>

describe "require_authenticated_user" do
  test "redirects if not logged in", %{conn: conn} do
    assert {:error, {:redirect, %{to: "/users/log-in"}}} =
             live(conn, ~p"/dashboard")
  end

  test "renders page when authenticated", %{conn: conn} do
    user = user_fixture()
    conn = log_in_user(conn, user)

    {:ok, _lv, html} = live(conn, ~p"/dashboard")
    assert html =~ "Dashboard"
  end
end

describe "redirect_if_authenticated" do
  test "redirects if already logged in", %{conn: conn} do
    user = user_fixture()
    conn = log_in_user(conn, user)

    assert {:error, {:redirect, %{to: "/"}}} =
             live(conn, ~p"/users/log-in")
  end
end

describe "on_mount: :require_authenticated_user" do
  test "authenticates user from session", %{conn: conn} do
    user = user_fixture()
    token = Accounts.generate_user_session_token(user)

    assert {:cont, updated_socket} =
             UserAuth.on_mount(
               :require_authenticated_user,
               %{},
               %{"user_token" => token},
               %LiveView.Socket{
                 endpoint: MyAppWeb.Endpoint,
                 assigns: %{__changed__: %{}}
               }
             )

    assert updated_socket.assigns.current_scope.user.id == user.id
  end

  test "redirects when no session token" do
    assert {:halt, updated_socket} =
             UserAuth.on_mount(
               :require_authenticated_user,
               %{},
               %{},
               %LiveView.Socket{
                 endpoint: MyAppWeb.Endpoint,
                 assigns: %{__changed__: %{}, flash: %{}}
               }
             )

    assert updated_socket.redirected == {:redirect, %{to: "/users/log-in"}}
  end
end