Support activity+json request for activity

lib/pleroma/web/activity_pub/activity_pub_controller.ex

@@ -54,6 +54,19 @@ def object(conn, %{"uuid" => uuid}) do
     end
   end
 
+  def activity(conn, %{"uuid" => uuid}) do
+    with ap_id <- o_status_url(conn, :activity, uuid),
+         %Activity{} = activity <- Activity.normalize(ap_id),
+         {_, true} <- {:public?, ActivityPub.is_public?(activity)} do
+      conn
+      |> put_resp_header("content-type", "application/activity+json")
+      |> json(ObjectView.render("object.json", %{object: activity}))
+    else
+      {:public?, false} ->
+        {:error, :not_found}
+    end
+  end
+
   def following(conn, %{"nickname" => nickname, "page" => page}) do
     with %User{} = user <- User.get_cached_by_nickname(nickname),
          {:ok, user} <- Pleroma.Web.WebFinger.ensure_keys_present(user) do

lib/pleroma/web/ostatus/ostatus_controller.ex

@@ -112,6 +112,9 @@ def object(conn, %{"uuid" => uuid}) do
   end
 
   def activity(conn, %{"uuid" => uuid}) do
+    if get_format(conn) == "activity+json" do
+      ActivityPubController.call(conn, :activity)
+    else
       with id <- o_status_url(conn, :activity, uuid),
            {_, %Activity{} = activity} <- {:activity, Activity.normalize(id)},
            {_, true} <- {:public?, ActivityPub.is_public?(activity)},
@@ -131,6 +134,7 @@ def activity(conn, %{"uuid" => uuid}) do
           e
       end
     end
+  end
 
   def notice(conn, %{"id" => id}) do
     with {_, %Activity{} = activity} <- {:activity, Repo.get(Activity, id)},

test/web/activity_pub/activity_pub_controller_test.exs

@@ -89,6 +89,32 @@ test "it returns 404 for tombstone objects", %{conn: conn} do
     end
   end
 
+  describe "/activities/:uuid" do
+    test "it returns a json representation of the activity", %{conn: conn} do
+      activity = insert(:note_activity)
+      uuid = String.split(activity.data["id"], "/") |> List.last()
+
+      conn =
+        conn
+        |> put_req_header("accept", "application/activity+json")
+        |> get("/activities/#{uuid}")
+
+      assert json_response(conn, 200) == ObjectView.render("object.json", %{object: activity})
+    end
+
+    test "it returns 404 for non-public activities", %{conn: conn} do
+      activity = insert(:direct_note_activity)
+      uuid = String.split(activity.data["id"], "/") |> List.last()
+
+      conn =
+        conn
+        |> put_req_header("accept", "application/activity+json")
+        |> get("/activities/#{uuid}")
+
+      assert json_response(conn, 404)
+    end
+  end
+
   describe "/inbox" do
     test "it inserts an incoming activity into the database", %{conn: conn} do
       data = File.read!("test/fixtures/mastodon-post-activity.json") |> Poison.decode!()