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/activitypub/notes.js

@@ -0,0 +1,82 @@
+'use strict';
+
+const winston = require('winston');
+
+const db = require('../database');
+const posts = require('../posts');
+
+const activitypub = module.parent.exports;
+const Notes = module.exports;
+
+// todo: when asserted, notes aren't added to a global sorted set
+// also, db.exists call is probably expensive
+Notes.assert = async (uid, input) => {
+	// Ensures that each note has been saved to the database
+	await Promise.all(input.map(async (item) => {
+		const id = activitypub.helpers.isUri(item) ? item : item.id;
+		const key = `post:${id}`;
+		const exists = await db.exists(key);
+		winston.verbose(`[activitypub/notes.assert] Asserting note id ${id}`);
+
+		let postData;
+		if (!exists) {
+			winston.verbose(`[activitypub/notes.assert] Not found, saving note to database`);
+			const object = activitypub.helpers.isUri(item) ? await activitypub.get(uid, item) : item;
+			postData = await activitypub.mocks.post(object);
+			if (postData) {
+				await db.setObject(key, postData);
+			}
+		}
+	}));
+};
+
+Notes.getParentChain = async (uid, input) => {
+	// Traverse upwards via `inReplyTo` until you find the root-level Note
+	const id = activitypub.helpers.isUri(input) ? input : input.id;
+
+	const chain = new Set();
+	const traverse = async (uid, id) => {
+		const exists = await db.exists(`post:${id}`);
+		if (exists) {
+			const { toPid, timestamp } = await posts.getPostFields(id, ['toPid', 'timestamp']);
+			chain.add({ id, timestamp });
+			if (toPid) {
+				await traverse(uid, toPid);
+			}
+		} else {
+			let object = await activitypub.get(uid, id);
+			object = await activitypub.mocks.post(object);
+			if (object) {
+				chain.add({ id, timestamp: object.timestamp });
+				if (object.hasOwnProperty('toPid') && object.toPid) {
+					await traverse(uid, object.toPid);
+				}
+			}
+		}
+	};
+
+	await traverse(uid, id);
+	return chain;
+};
+
+Notes.assertTopic = async (uid, id) => {
+	// Given the id of any post, traverses up (and soon, down) to cache the entire threaded context
+	const chain = Array.from(await Notes.getParentChain(uid, id));
+	const tid = chain[chain.length - 1].id;
+
+	const sorted = chain.sort((a, b) => a.timestamp - b.timestamp);
+	const [ids, timestamps] = [
+		sorted.map(n => n.id),
+		sorted.map(n => n.timestamp),
+	];
+
+	await db.sortedSetAdd(`topicRemote:${tid}`, timestamps, ids);
+	await Notes.assert(uid, chain);
+
+	return tid;
+};
+
+Notes.getTopicPosts = async (tid, uid, start, stop) => {
+	const pids = await db.getSortedSetRange(`topicRemote:${tid}`, start, stop);
+	return await posts.getPostsByPids(pids, uid);
+};