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)
+}

internal/fediverse/fediverse_test.go

@@ -0,0 +1,21 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: PolyForm-Noncommercial-1.0.0
+
+package fediverse
+
+import "testing"
+
+func TestValid(t *testing.T) {
+	good := []string{"@user@host.social", "@a@b", "@petr@social.example.org"}
+	for _, handle := range good {
+		if !Valid(handle) {
+			t.Errorf("Valid(%q) = false, want true", handle)
+		}
+	}
+	bad := []string{"", "user@host", "@user", "@@host", "@user@", "@user @host", "@user@ho st", "u@h"}
+	for _, handle := range bad {
+		if Valid(handle) {
+			t.Errorf("Valid(%q) = true, want false", handle)
+		}
+	}
+}