Prevent last admin from being deleted (#694)

* Prevent last admin from being deleted

* fix tests

apps/fz_http/lib/fz_http/users.ex

@@ -32,6 +32,10 @@ defmodule FzHttp.Users do
     Repo.exists?(from u in User, where: u.id == ^user_id)
   end
 
+  def list_admins do
+    Repo.all(from User, where: [role: :admin])
+  end
+
   def get_user!(email: email) do
     Repo.get_by!(User, email: email)
   end

apps/fz_http/lib/fz_http_web/controllers/user_controller.ex

@@ -10,6 +10,12 @@ defmodule FzHttpWeb.UserController do
   def delete(conn, _params) do
     user = Authentication.get_current_user(conn)
 
+    with %{role: :admin} <- user do
+      unless length(Users.list_admins()) > 1 do
+        raise "Cannot delete one last admin"
+      end
+    end
+
     case Users.delete_user(user) do
       {:ok, _user} ->
         FzHttpWeb.Endpoint.broadcast("users_socket:#{user.id}", "disconnect", %{})

apps/fz_http/lib/fz_http_web/live/setting_live/account.html.heex

@@ -84,7 +84,7 @@
 
   <%# This is purposefully a synchronous form in order to easily clear the session %>
   <%= form_for @changeset, Routes.user_path(@socket, :delete), [id: "delete-account", method: :delete], fn _f -> %>
-    <%= submit(class: "button is-danger", data: [confirm: "Are you sure?"]) do %>
+    <%= submit(class: "button is-danger", data: [confirm: "Are you sure?"], disabled: !@allow_delete) do %>
       <span class="icon is-small">
         <i class="fas fa-trash"></i>
       </span>

apps/fz_http/lib/fz_http_web/live/setting_live/account_live.ex

@@ -25,7 +25,8 @@ defmodule FzHttpWeb.SettingLive.Account do
 
   @impl Phoenix.LiveView
   def handle_params(_params, _url, socket) do
-    {:noreply, socket}
+    admins = Users.list_admins()
+    {:noreply, assign(socket, :allow_delete, length(admins) > 1)}
   end
 
   @impl Phoenix.LiveView

apps/fz_http/test/fz_http_web/controllers/user_controller_test.exs

@@ -1,7 +1,11 @@
 defmodule FzHttpWeb.UserControllerTest do
   use FzHttpWeb.ConnCase, async: true
 
-  alias FzHttp.Users
+  alias FzHttp.{Users, UsersFixtures}
+
+  setup do
+    {:ok, extra_admin: UsersFixtures.user()}
+  end
 
   describe "when user signed in" do
     test "deletes the user", %{admin_conn: conn} do
@@ -9,9 +13,24 @@ defmodule FzHttpWeb.UserControllerTest do
 
       assert redirected_to(test_conn) == Routes.root_path(test_conn, :index)
     end
+
+    test "prevents deletion if no extra admin", %{admin_conn: conn, extra_admin: extra_admin} do
+      Users.delete_user(extra_admin)
+
+      assert_raise(RuntimeError, fn ->
+        delete(conn, Routes.user_path(conn, :delete))
+      end)
+    end
   end
 
   describe "when user is already deleted" do
+    setup do
+      # this allows there to be 2 admins left after the main test admin is
+      # deleted, so that the deletion doesn't raise
+      _yet_another_admin = UsersFixtures.user()
+      :ok
+    end
+
     test "returns 404", %{admin_user: user, admin_conn: conn} do
       user.id
       |> Users.get_user!()