From 9fbc1b7f7b71cf0eafadd728a6b66cb95a0c35d8 Mon Sep 17 00:00:00 2001
From: taichan <40626578+tai-cha@users.noreply.github.com>
Date: Sat, 17 Aug 2024 15:12:23 +0900
Subject: [PATCH] =?UTF-8?q?enhance(backend):=20head=E3=82=BF=E3=82=B0?=
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* signedGet時にhttpかつalternate属性のlinkがある場合に一回だけfollowして照会する

* Fix: validation position

* Fix import

* Fix tagname

* Update CHANGELOG

* Fix code style

---------

Co-authored-by: syuilo <4439005+syuilo@users.noreply.github.com>
---
 CHANGELOG.md                                  |  1 +
 .../src/core/activitypub/ApRequestService.ts  | 24 +++++++++++++++++--
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6e98f9f193..0de0d40877 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,7 @@
 - Fix: 特定の条件下でノートの削除ボタンが出ないのを修正
 
 ### Server
+- enhance: 照会時にURLがhtmlかつheadタグ内に`rel="alternate"`, `type="application/activity+json"`の`link`タグがある場合に追ってリンク先を照会できるように
 - Enhance: 凍結されたアカウントのフォローリクエストを表示しないように
 - Fix: WSの`readAllNotifications` メッセージが `body` を持たない場合に動作しない問題 #14374
   - 通知ページや通知カラム(デッキ)を開いている状態において、新たに発生した通知が既読されない問題が修正されます。
diff --git a/packages/backend/src/core/activitypub/ApRequestService.ts b/packages/backend/src/core/activitypub/ApRequestService.ts
index 93ac8ce9a7..69b09ba808 100644
--- a/packages/backend/src/core/activitypub/ApRequestService.ts
+++ b/packages/backend/src/core/activitypub/ApRequestService.ts
@@ -6,6 +6,7 @@
 import * as crypto from 'node:crypto';
 import { URL } from 'node:url';
 import { Inject, Injectable } from '@nestjs/common';
+import { Window } from 'happy-dom';
 import { DI } from '@/di-symbols.js';
 import type { Config } from '@/config.js';
 import type { MiUser } from '@/models/User.js';
@@ -180,7 +181,8 @@ export class ApRequestService {
 	 * @param url URL to fetch
 	 */
 	@bindThis
-	public async signedGet(url: string, user: { id: MiUser['id'] }): Promise<unknown> {
+	public async signedGet(url: string, user: { id: MiUser['id'] }, followAlternate?: boolean): Promise<unknown> {
+		const _followAlternate = followAlternate ?? true;
 		const keypair = await this.userKeypairService.getUserKeypair(user.id);
 
 		const req = ApRequestCreator.createSignedGet({
@@ -198,9 +200,27 @@ export class ApRequestService {
 			headers: req.request.headers,
 		}, {
 			throwErrorWhenResponseNotOk: true,
-			validators: [validateContentTypeSetAsActivityPub],
 		});
 
+		//#region リクエスト先がhtmlかつactivity+jsonへのalternate linkタグがあるとき
+		if (res.headers.get('Content-type')?.startsWith('text/html;') && _followAlternate === true) {
+			const html = await res.text();
+			const window = new Window();
+			const document = window.document;
+			document.documentElement.innerHTML = html;
+
+			const alternate = document.querySelector('head > link[rel="alternate"][type="application/activity+json"]');
+			if (alternate) {
+				const href = alternate.getAttribute('href');
+				if (href) {
+					return await this.signedGet(href, user, false);
+				}
+			}
+		}
+		//#endregion
+
+		validateContentTypeSetAsActivityPub(res);
+
 		return await res.json();
 	}
 }