feat: ability to query remote users by webfinger handle

src/activitypub/helpers.js

@@ -15,6 +15,7 @@ const ttl = require('../cache/ttl');
 const user = require('../user');
 const activitypub = require('.');
 
+const webfingerRegex = /^(@|acct:)?\w+@.+$/;
 const webfingerCache = ttl({ ttl: 1000 * 60 * 60 * 24 }); // 24 hours
 
 const Helpers = module.exports;
@@ -33,6 +34,21 @@ Helpers.isUri = (value) => {
 	});
 };
 
+Helpers.isWebfinger = (value) => {
+	// N.B. returns normalized handle, so truthy check!
+	if (webfingerRegex.test(value) && !Helpers.isUri(value)) {
+		if (value.startsWith('@')) {
+			return value.slice(1);
+		} else if (value.startsWith('acct:')) {
+			return value.slice(5);
+		}
+
+		return value;
+	}
+
+	return false;
+};
+
 Helpers.query = async (id) => {
 	const isUri = Helpers.isUri(id);
 	// username@host ids use acct: URI schema