Initial commit

Assisted-by: GLM 5.3

internal/fediverse/fediverse.go

@@ -0,0 +1,17 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: PolyForm-Noncommercial-1.0.0
+
+// Package fediverse validates the fediverse handle that posts, users and
+// the site configuration carry. It is a leaf so that the configuration
+// and the domain object can share one rule without either importing the
+// other.
+package fediverse
+
+import "regexp"
+
+var handleRe = regexp.MustCompile(`\A@[^@\s]+@[^@\s]+\z`)
+
+// Valid reports whether handle looks like @user@host.
+func Valid(handle string) bool {
+	return handleRe.MatchString(handle)
+}