Events with only one event creator participant can't be left

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

lib/mobilizon/events/events.ex

@@ -582,6 +582,28 @@ defmodule Mobilizon.Events do
     )
   end
 
+  @doc """
+  Returns the list of organizers participants for an event.
+
+  ## Examples
+
+      iex> list_organizers_participants_for_event(id)
+      [%Participant{role: :creator}, ...]
+
+  """
+  def list_organizers_participants_for_event(id, page \\ nil, limit \\ nil) do
+    Repo.all(
+      from(
+        p in Participant,
+        join: e in Event,
+        on: p.event_id == e.id,
+        where: e.id == ^id and p.role == ^:creator,
+        preload: [:actor]
+      )
+      |> paginate(page, limit)
+    )
+  end
+
   @doc """
   Gets a single participant.
 

lib/mobilizon_web/resolvers/event.ex

@@ -100,12 +100,19 @@ defmodule MobilizonWeb.Resolvers.Event do
     with {:is_owned, true, _} <- User.owns_actor(user, actor_id),
          {:ok, %Participant{} = participant} <-
            Mobilizon.Events.get_participant(event_id, actor_id),
-         {:ok, _} <- Mobilizon.Events.delete_participant(participant) do
+         {:only_organizer, false} <-
+           {:only_organizer,
+            Mobilizon.Events.list_organizers_participants_for_event(event_id) |> length == 1},
+         {:ok, _} <-
+           Mobilizon.Events.delete_participant(participant) do
       {:ok, %{event: %{id: event_id}, actor: %{id: actor_id}}}
     else
       {:is_owned, false} ->
         {:error, "Actor id is not owned by authenticated user"}
 
+      {:only_organizer, true} ->
+        {:error, "You can't leave event because you're the only event creator participant"}
+
       {:error, :participant_not_found} ->
         {:error, "Participant not found"}
     end