feat: ability to browse to any ActivityPub note and have the entire topic chain render

Added methods for going up the inReplyTo chain to parent, asserting the topic, etc.

src/controllers/activitypub/topics.js

@@ -0,0 +1,81 @@
+'use strict';
+
+const user = require('../../user');
+const topics = require('../../topics');
+
+const { notes } = require('../../activitypub');
+// const helpers = require('../helpers');
+// const pagination = require('../../pagination');
+
+const controller = module.exports;
+
+controller.get = async function (req, res, next) {
+	const tid = await notes.assertTopic(req.uid, req.query.resource);
+
+	let postIndex = parseInt(req.params.post_index, 10) || 1;
+	const [
+		// userPrivileges,
+		settings,
+		// topicData,
+	] = await Promise.all([
+		// privileges.topics.get(tid, req.uid),
+		user.getSettings(req.uid),
+		// topics.getTopicData(tid),
+	]);
+
+	const topicData = {
+		tid,
+		postCount: 6,
+		category: {}, // todo
+	};
+
+	let currentPage = parseInt(req.query.page, 10) || 1;
+	const pageCount = Math.max(1, Math.ceil((topicData && topicData.postcount) / settings.postsPerPage));
+	const invalidPagination = (settings.usePagination && (currentPage < 1 || currentPage > pageCount));
+	if (
+		!topicData ||
+		// userPrivileges.disabled ||
+		invalidPagination// ||
+		// (topicData.scheduled && !userPrivileges.view_scheduled)
+	) {
+		return next();
+	}
+
+	if (!req.query.page) {
+		currentPage = calculatePageFromIndex(postIndex, settings);
+	}
+	if (settings.usePagination && req.query.page) {
+		const top = ((currentPage - 1) * settings.postsPerPage) + 1;
+		const bottom = top + settings.postsPerPage;
+		if (!req.params.post_index || (postIndex < top || postIndex > bottom)) {
+			postIndex = top;
+		}
+	}
+	const { start, stop } = calculateStartStop(currentPage, postIndex, settings);
+
+	topicData.posts = await notes.getTopicPosts(tid, req.uid, start, stop);
+	topicData.posts = await topics.addPostData(topicData.posts, req.uid);
+
+	res.render('topic', topicData);
+};
+
+// todo: expose from topic controller?
+function calculatePageFromIndex(postIndex, settings) {
+	return 1 + Math.floor((postIndex - 1) / settings.postsPerPage);
+}
+
+// todo: expose from topic controller?
+function calculateStartStop(page, postIndex, settings) {
+	let startSkip = 0;
+
+	if (!settings.usePagination) {
+		if (postIndex > 1) {
+			page = 1;
+		}
+		startSkip = Math.max(0, postIndex - Math.ceil(settings.postsPerPage / 2));
+	}
+
+	const start = ((page - 1) * settings.postsPerPage) + startSkip;
+	const stop = start + settings.postsPerPage - 1;
+	return { start: Math.max(0, start), stop: Math.max(0, stop) };
+}