From 34d55e2ddad35175afe30b067427b52afca51dda Mon Sep 17 00:00:00 2001
From: Johann150 <johann.galle@protonmail.com>
Date: Fri, 28 Apr 2023 23:47:48 +0200
Subject: [PATCH] server: better matching for MFM mentions

When rendering the HTML for outgoing activities, the mentions are now
matched case insensitive and should also work properly for IDNs. The
username is also compared case insensitive. Mentions of local users
are also handled properly independed of whether the hostname was given
or omitted.

The query to get mentions is now also only executed once instead of
for each mention individually.

Changelog: Fixed
---
 packages/backend/src/mfm/to-html.ts | 58 +++++++++++++++++------------
 1 file changed, 35 insertions(+), 23 deletions(-)

diff --git a/packages/backend/src/mfm/to-html.ts b/packages/backend/src/mfm/to-html.ts
index 830bfac52..06acaeceb 100644
--- a/packages/backend/src/mfm/to-html.ts
+++ b/packages/backend/src/mfm/to-html.ts
@@ -4,6 +4,7 @@ import config from '@/config/index.js';
 import { UserProfiles } from '@/models/index.js';
 import { extractMentions } from '@/misc/extract-mentions.js';
 import { intersperse } from '@/prelude/array.js';
+import { toPunyNullable } from '@/misc/convert-host.js';
 
 // Transforms MFM to HTML, given the MFM text and a list of user IDs that are
 // mentioned in the text. If the list of mentions is not given, all mentions
@@ -14,6 +15,19 @@ export async function toHtml(mfmText: string, mentions?: string[]): Promise<stri
 		return null;
 	}
 
+	let mentionedUsers = [];
+	const ids = mentions ?? extractMentions(nodes);
+	if (ids.length > 0) {
+		mentionedUsers = await UserProfiles.createQueryBuilder('user_profile')
+			.leftJoin('user_profile.user', 'user')
+			.select('user.usernameLower', 'username')
+			.addSelect('user.host', 'host')
+			// links should preferably use user friendly urls, only fall back to AP ids
+			.addSelect('COALESCE(user_profile.url, user.uri)', 'url')
+			.where('"userId" IN (:...ids)', { ids })
+			.getRawMany();
+	}
+
 	const doc = new JSDOM('').window.document;
 
 	const handlers: { [K in mfm.MfmNode['type']]: (node: mfm.NodeType<K>) => Promise<Node> } = {
@@ -103,30 +117,28 @@ export async function toHtml(mfmText: string, mentions?: string[]): Promise<stri
 		},
 
 		async mention(node): Promise<HTMLElement | Text> {
-			const { username, host, acct } = node.props;
-			const ids = mentions ?? extractMentions(nodes);
-			if (ids.length > 0) {
-				const mentionedUsers = await UserProfiles.createQueryBuilder('user_profile')
-					.leftJoin('user_profile.user', 'user')
-					.select('user.username', 'username')
-					.addSelect('user.host', 'host')
-					// links should preferably use user friendly urls, only fall back to AP ids
-					.addSelect('COALESCE(user_profile.url, user.uri)', 'url')
-					.where('"userId" IN (:...ids)', { ids })
-					.getRawMany();
-				const userInfo = mentionedUsers.find(user => user.username === username && user.host === host);
-				if (userInfo != null) {
-					// Mastodon microformat: span.h-card > a.u-url.mention
-					const a = doc.createElement('a');
-					a.href = userInfo.url ?? `${config.url}/${acct}`;
-					a.className = 'u-url mention';
-					a.textContent = acct;
+			let { username, host, acct } = node.props;
+			// normalize username and host for searching the user
+			username = username.toLowerCase();
+			host = toPunyNullable(host);
+			// Discard host if it is the local host. Otherwise mentions of local users where the
+			// hostname is not omitted are not handled correctly.
+			if (host == config.hostname) {
+				host = null;
+			}
+			const userInfo = mentionedUsers.find(user => user.username === username && user.host === host);
+			if (userInfo != null) {
+				// Mastodon microformat: span.h-card > a.u-url.mention
+				const a = doc.createElement('a');
+				// The fallback will only be used for local users, so the host part can be discarded.
+				a.href = userInfo.url ?? `${config.url}/@${username}`;
+				a.className = 'u-url mention';
+				a.textContent = acct;
 
-					const card = doc.createElement('span');
-					card.className = 'h-card';
-					card.appendChild(a);
-					return card;
-				}
+				const card = doc.createElement('span');
+				card.className = 'h-card';
+				card.appendChild(a);
+				return card;
 			}
 			// this user does not actually exist
 			return doc.createTextNode(acct);