From 26a7c51a9a6419bc718176f1a7244a50a1599b44 Mon Sep 17 00:00:00 2001
From: Julian Lam <julian@nodebb.org>
Date: Fri, 5 Jul 2024 15:33:06 -0400
Subject: [PATCH] feat: AP note replies collection, closes #12675

---
 src/activitypub/mocks.js              |  2 +-
 src/controllers/activitypub/actors.js | 22 ++++++++++++++++++++++
 src/routes/activitypub.js             |  1 +
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/src/activitypub/mocks.js b/src/activitypub/mocks.js
index e262834f3a..7e9051d74d 100644
--- a/src/activitypub/mocks.js
+++ b/src/activitypub/mocks.js
@@ -403,7 +403,7 @@ Mocks.note = async (post) => {
 		source,
 		tag,
 		attachment,
-		// replies: {}  todo...
+		replies: `${id}/replies`,
 	};
 
 	return object;
diff --git a/src/controllers/activitypub/actors.js b/src/controllers/activitypub/actors.js
index f173fda30b..8fe89f38e5 100644
--- a/src/controllers/activitypub/actors.js
+++ b/src/controllers/activitypub/actors.js
@@ -62,6 +62,28 @@ Actors.note = async function (req, res) {
 	res.status(200).json(payload);
 };
 
+Actors.replies = async function (req, res) {
+	const page = parseInt(req.query.page, 10);
+	const replies = await activitypub.helpers.generateCollection({
+		set: `pid:${req.params.pid}:replies`,
+		page,
+		perPage: meta.config.postsPerPage,
+		url: `${nconf.get('url')}/post/${req.params.pid}/replies`,
+	});
+
+	const object = {
+		'@context': 'https://www.w3.org/ns/activitystreams',
+		id: `${nconf.get('url')}/post/${req.params.pid}/replies${replies.orderedItems && page ? `?page=${page}` : ''}`,
+		url: `${nconf.get('url')}/post/${req.params.pid}`,
+		...replies,
+	}
+
+	// Convert pids to urls
+	replies.orderedItems = replies.orderedItems.map(pid => (utils.isNumber(pid) ? `${nconf.get('url')}/post/${pid}` : pid));
+
+	res.status(200).json(object);
+};
+
 Actors.topic = async function (req, res, next) {
 	const allowed = await privileges.topics.can('topics:read', req.params.tid, activitypub._constants.uid);
 	if (!allowed) {
diff --git a/src/routes/activitypub.js b/src/routes/activitypub.js
index 9f32715ebc..851da933da 100644
--- a/src/routes/activitypub.js
+++ b/src/routes/activitypub.js
@@ -35,6 +35,7 @@ module.exports = function (app, middleware, controllers) {
 	app.get('/uid/:uid/followers', [...middlewares, middleware.assert.user], controllers.activitypub.getFollowers);
 
 	app.get('/post/:pid', [...middlewares, middleware.assert.post], controllers.activitypub.actors.note);
+	app.get('/post/:pid/replies', [...middlewares, middleware.assert.post], controllers.activitypub.actors.replies);
 
 	app.get('/topic/:tid/:slug?', [...middlewares, middleware.assert.topic], controllers.activitypub.actors.topic);