Make sure people can't join an event with limited participants

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

lib/mobilizon/events/events.ex

@@ -762,6 +762,17 @@ defmodule Mobilizon.Events do
     |> Repo.aggregate(:count, :id)
   end
 
+  @doc """
+  Counts participant participants.
+  """
+  @spec count_participant_participants(integer | String.t()) :: integer
+  def count_participant_participants(event_id) do
+    event_id
+    |> count_participants_query()
+    |> filter_participant_role()
+    |> Repo.aggregate(:count, :id)
+  end
+
   @doc """
   Counts unapproved participants.
   """
@@ -1457,6 +1468,11 @@ defmodule Mobilizon.Events do
     from(p in query, where: p.role not in ^[:not_approved, :rejected])
   end
 
+  @spec filter_participant_role(Ecto.Query.t()) :: Ecto.Query.t()
+  defp filter_participant_role(query) do
+    from(p in query, where: p.role == ^:participant)
+  end
+
   @spec filter_unapproved_role(Ecto.Query.t()) :: Ecto.Query.t()
   defp filter_unapproved_role(query) do
     from(p in query, where: p.role == ^:not_approved)

lib/mobilizon_web/resolvers/event.ex

@@ -170,6 +170,9 @@ defmodule MobilizonWeb.Resolvers.Event do
            |> Map.put(:actor, Person.proxify_pictures(actor)) do
       {:ok, participant}
     else
+      {:maximum_attendee_capacity, _} ->
+        {:error, "The event has already reached it's maximum capacity"}
+
       {:has_event, _} ->
         {:error, "Event with this ID #{inspect(event_id)} doesn't exist"}
 

lib/service/activity_pub/activity_pub.ex

@@ -411,8 +411,16 @@ defmodule Mobilizon.Service.ActivityPub do
 
   def join(object, actor, local \\ true)
 
-  def join(%Event{} = event, %Actor{} = actor, local) do
-    with role <- Mobilizon.Events.get_default_participant_role(event),
+  def join(%Event{options: options} = event, %Actor{} = actor, local) do
+    # TODO Refactor me for federation
+    with maximum_attendee_capacity <-
+           Map.get(options, :maximum_attendee_capacity, 2_000_000) || false,
+         {:maximum_attendee_capacity, true} <-
+           {:maximum_attendee_capacity,
+            !maximum_attendee_capacity ||
+              Mobilizon.Events.count_participant_participants(event.id) <
+                maximum_attendee_capacity},
+         role <- Mobilizon.Events.get_default_participant_role(event),
          {:ok, %Participant{} = participant} <-
            Mobilizon.Events.create_participant(%{
              role: role,