From d7aa432cca86c7a4663d5e5b16c2580d5e63f214 Mon Sep 17 00:00:00 2001
From: Thomas Citharel <tcit@tcit.fr>
Date: Mon, 18 Apr 2022 16:59:07 +0200
Subject: [PATCH] Fix receiving Flag activities on federated events

Signed-off-by: Thomas Citharel <tcit@tcit.fr>
---
 lib/federation/activity_pub/transmogrifier.ex |  3 +-
 .../activity_stream/converter/flag.ex         | 67 +++++++++++--------
 2 files changed, 42 insertions(+), 28 deletions(-)

diff --git a/lib/federation/activity_pub/transmogrifier.ex b/lib/federation/activity_pub/transmogrifier.ex
index 55137ade5..2d904ad1a 100644
--- a/lib/federation/activity_pub/transmogrifier.ex
+++ b/lib/federation/activity_pub/transmogrifier.ex
@@ -41,7 +41,8 @@ defmodule Mobilizon.Federation.ActivityPub.Transmogrifier do
       params = %{
         reporter_id: params["reporter"].id,
         reported_id: params["reported"].id,
-        comments_ids: params["comments"] |> Enum.map(& &1.id),
+        comments_ids:
+          if(params["comments"], do: params["comments"] |> Enum.map(& &1.id), else: []),
         content: params["content"] || "",
         additional: %{
           "cc" => [params["reported"].url]
diff --git a/lib/federation/activity_stream/converter/flag.ex b/lib/federation/activity_stream/converter/flag.ex
index 290551e02..4ff34f678 100644
--- a/lib/federation/activity_stream/converter/flag.ex
+++ b/lib/federation/activity_stream/converter/flag.ex
@@ -67,33 +67,9 @@ defmodule Mobilizon.Federation.ActivityStream.Converter.Flag do
   def as_to_model(%{"object" => objects} = object) do
     with {:ok, %Actor{} = reporter} <-
            ActivityPubActor.get_or_fetch_actor_by_url(object["actor"]),
-         %Actor{} = reported <-
-           Enum.reduce_while(objects, nil, fn url, _ ->
-             case ActivityPubActor.get_or_fetch_actor_by_url(url) do
-               {:ok, %Actor{} = actor} ->
-                 {:halt, actor}
-
-               _ ->
-                 {:cont, nil}
-             end
-           end),
-         event <-
-           Enum.reduce_while(objects, nil, fn url, _ ->
-             case Events.get_event_by_url(url) do
-               %Event{} = event ->
-                 {:halt, event}
-
-               _ ->
-                 {:cont, nil}
-             end
-           end),
-
-         # Remove the reported actor and the event from the object list.
-         comments <-
-           Enum.filter(objects, fn url ->
-             !(url == reported.url || (!is_nil(event) && event.url == url))
-           end),
-         comments <- Enum.map(comments, &Discussions.get_comment_from_url/1) do
+         %Actor{} = reported <- find_reported(objects),
+         event <- find_event(objects),
+         comments <- find_comments(objects, reported, event) do
       %{
         "reporter" => reporter,
         "uri" => object["id"],
@@ -104,4 +80,41 @@ defmodule Mobilizon.Federation.ActivityStream.Converter.Flag do
       }
     end
   end
+
+  @spec find_reported(list(String.t())) :: Actor.t() | nil
+  defp find_reported(objects) do
+    Enum.reduce_while(objects, nil, fn url, _ ->
+      case ActivityPubActor.get_or_fetch_actor_by_url(url) do
+        {:ok, %Actor{} = actor} ->
+          {:halt, actor}
+
+        _ ->
+          {:cont, nil}
+      end
+    end)
+  end
+
+  # Remove the reported actor and the event from the object list.
+  @spec find_comments(list(String.t()), Actor.t() | nil, Event.t() | nil) :: list(Comment.t())
+  defp find_comments(objects, reported, event) do
+    objects
+    |> Enum.filter(fn url ->
+      !((!is_nil(reported) && url == reported.url) || (!is_nil(event) && event.url == url))
+    end)
+    |> Enum.map(&Discussions.get_comment_from_url/1)
+    |> Enum.filter(& &1)
+  end
+
+  @spec find_event(list(String.t())) :: Event.t() | nil
+  defp find_event(objects) do
+    Enum.reduce_while(objects, nil, fn url, _ ->
+      case Events.get_event_by_url(url) do
+        %Event{} = event ->
+          {:halt, event}
+
+        _ ->
+          {:cont, nil}
+      end
+    end)
+  end
 end