1 files changed, 48 insertions, 0 deletions
diff --git a/packages/backend/src/core/WebfingerService.ts b/packages/backend/src/core/WebfingerService.ts
new file mode 100644
index 0000000000..d2a88be583
--- /dev/null
+++ b/packages/backend/src/core/WebfingerService.ts
@@ -0,0 +1,48 @@
+import { URL } from 'node:url';
+import { Inject, Injectable } from '@nestjs/common';
+import { DI } from '@/di-symbols.js';
+import type { Config } from '@/config.js';
+import { query as urlQuery } from '@/misc/prelude/url.js';
+import { HttpRequestService } from '@/core/HttpRequestService.js';
+
+type ILink = {
+	href: string;
+	rel?: string;
+};
+
+type IWebFinger = {
+	links: ILink[];
+	subject: string;
+};
+
+@Injectable()
+export class WebfingerService {
+	constructor(
+		@Inject(DI.config)
+		private config: Config,
+
+		private httpRequestService: HttpRequestService,
+	) {
+	}
+
+	public async webfinger(query: string): Promise<IWebFinger> {
+		const url = this.genUrl(query);
+
+		return await this.httpRequestService.getJson(url, 'application/jrd+json, application/json') as IWebFinger;
+	}
+
+	private genUrl(query: string): 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})`);
+	}
+}