refactoring

Resolve #7779

packages/backend/src/remote/webfinger.ts

@@ -0,0 +1,34 @@
+import { URL } from 'url';
+import { getJson } from '@/misc/fetch';
+import { query as urlQuery } from '@/prelude/url';
+
+type ILink = {
+	href: string;
+	rel?: string;
+};
+
+type IWebFinger = {
+	links: ILink[];
+	subject: string;
+};
+
+export default async function(query: string): Promise<IWebFinger> {
+	const url = genUrl(query);
+
+	return await getJson(url, 'application/jrd+json, application/json');
+}
+
+function genUrl(query: string) {
+	if (query.match(/^https?:\/\//)) {
+		const u = new URL(query);
+		return `${u.protocol}//${u.hostname}/.well-known/webfinger?` + urlQuery({ resource: query });
+	}
+
+	const m = query.match(/^([^@]+)@(.*)/);
+	if (m) {
+		const hostname = m[2];
+		return `https://${hostname}/.well-known/webfinger?` + urlQuery({ resource: `acct:${query}` });
+	}
+
+	throw new Error(`Invalid query (${query})`);
+}