From 60ec42cb9c5f362e01ca2fb506ac153e00d5caa1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?marcin=20miko=C5=82ajczak?= <git@mkljczk.pl>
Date: Sat, 12 Oct 2024 23:45:18 +0200
Subject: [PATCH] Add metadata provider for ActivityPub alternate links
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Signed-off-by: marcin mikołajczak <git@mkljczk.pl>
---
 changelog.d/activity-pub-metadata.add         |  1 +
 lib/pleroma/web/metadata.ex                   |  1 +
 .../web/metadata/providers/activity_pub.ex    | 19 +++++++++++
 .../metadata/providers/activity_pub_test.exs  | 34 +++++++++++++++++++
 4 files changed, 55 insertions(+)
 create mode 100644 changelog.d/activity-pub-metadata.add
 create mode 100644 lib/pleroma/web/metadata/providers/activity_pub.ex
 create mode 100644 test/pleroma/web/metadata/providers/activity_pub_test.exs

diff --git a/changelog.d/activity-pub-metadata.add b/changelog.d/activity-pub-metadata.add
new file mode 100644
index 000000000..2ad3d7b2d
--- /dev/null
+++ b/changelog.d/activity-pub-metadata.add
@@ -0,0 +1 @@
+Add metadata provider for ActivityPub alternate links
diff --git a/lib/pleroma/web/metadata.ex b/lib/pleroma/web/metadata.ex
index 59d018730..4ee7c41ec 100644
--- a/lib/pleroma/web/metadata.ex
+++ b/lib/pleroma/web/metadata.ex
@@ -7,6 +7,7 @@ defmodule Pleroma.Web.Metadata do
 
   def build_tags(params) do
     providers = [
+      Pleroma.Web.Metadata.Providers.ActivityPub,
       Pleroma.Web.Metadata.Providers.RelMe,
       Pleroma.Web.Metadata.Providers.RestrictIndexing
       | activated_providers()
diff --git a/lib/pleroma/web/metadata/providers/activity_pub.ex b/lib/pleroma/web/metadata/providers/activity_pub.ex
new file mode 100644
index 000000000..1759a5a0d
--- /dev/null
+++ b/lib/pleroma/web/metadata/providers/activity_pub.ex
@@ -0,0 +1,19 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2024 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.Metadata.Providers.ActivityPub do
+  alias Pleroma.Web.Metadata.Providers.Provider
+
+  @behaviour Provider
+
+  @impl Provider
+  def build_tags(%{object: %{data: %{"id" => object_id}}}) do
+    [{:link, [rel: "alternate", type: "application/activity+json", href: object_id], []}]
+  end
+
+  @impl Provider
+  def build_tags(%{user: user}) do
+    [{:link, [rel: "alternate", type: "application/activity+json", href: user.ap_id], []}]
+  end
+end
diff --git a/test/pleroma/web/metadata/providers/activity_pub_test.exs b/test/pleroma/web/metadata/providers/activity_pub_test.exs
new file mode 100644
index 000000000..c379ec092
--- /dev/null
+++ b/test/pleroma/web/metadata/providers/activity_pub_test.exs
@@ -0,0 +1,34 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2024 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.Metadata.Providers.ActivityPubTest do
+  use Pleroma.DataCase
+  import Pleroma.Factory
+
+  alias Pleroma.Web.CommonAPI
+  alias Pleroma.Web.Metadata.Providers.ActivityPub
+
+  setup do: clear_config([Pleroma.Web.Metadata, :unfurl_nsfw])
+
+  test "it renders a link for user info" do
+    user = insert(:user)
+    res = ActivityPub.build_tags(%{user: user})
+
+    assert res == [
+             {:link, [rel: "alternate", type: "application/activity+json", href: user.ap_id], []}
+           ]
+  end
+
+  test "it renders a link for a post" do
+    user = insert(:user)
+    {:ok, %{id: activity_id, object: object}} = CommonAPI.post(user, %{status: "hi"})
+
+    result = ActivityPub.build_tags(%{object: object, user: user, activity_id: activity_id})
+
+    assert [
+             {:link,
+              [rel: "alternate", type: "application/activity+json", href: object.data["id"]], []}
+           ] == result
+  end
+end