skip resolving preview when a link is known to be recursive

packages/frontend/src/utility/extract-preview-urls.ts

@@ -0,0 +1,32 @@
+/*
+ * SPDX-FileCopyrightText: hazelnoot and other Sharkey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { host } from '@@/js/config.js';
+import type * as Misskey from 'misskey-js';
+import type * as mfm from '@transfem-org/sfm-js';
+import { extractUrlFromMfm } from '@/utility/extract-url-from-mfm.js';
+
+/**
+ * Extracts all previewable URLs from a note.
+ */
+export function extractPreviewUrls(note: Misskey.entities.Note, contents: mfm.MfmNode[]): string[] {
+	const links = extractUrlFromMfm(contents);
+	return links.filter(url =>
+		// Remote note
+		url !== note.url &&
+		url !== note.uri &&
+		// Local note
+		url !== `https://${host}/notes/${note.id}` &&
+		// Remote renote or quote
+		url !== note.renote?.url &&
+		url !== note.renote?.uri &&
+		// Local renote or quote
+		url !== `https://${host}/notes/${note.renote?.id}` &&
+		// Remote renote *of* a quote
+		url !== note.renote?.renote?.url &&
+		url !== note.renote?.renote?.uri &&
+		// Local renote *of* a quote
+		url !== `https://${host}/notes/${note.renote?.renote?.id}`);
+}