chore: strict Subdomain Validation with Detailed Error Messages (#42)

Co-authored-by: userAdityaa <aditya.chaudhary1558@gmail.com> Co-committed-by: userAdityaa <aditya.chaudhary1558@gmail.com>
2026-04-21 13:09:37 +00:00
parent bc79da34cf
commit a26bc1127d
4 changed files with 137 additions and 53 deletions
@@ -0,0 +1,22 @@
+const SUBDOMAIN_LABEL_MAX_LEN = 63
+const RESERVED_SUBDOMAIN_LABELS = new Set(["api", "admin"])
+
+export function validateSubdomainLabel(subdomain: string): string | null {
+  if (subdomain.length === 0) {
+    return "subdomain is required"
+  }
+  if (subdomain.length > SUBDOMAIN_LABEL_MAX_LEN) {
+    return "subdomain must be 63 characters or fewer"
+  }
+  if (subdomain.startsWith("-") || subdomain.endsWith("-")) {
+    return "subdomain cannot start or end with a hyphen"
+  }
+  if (RESERVED_SUBDOMAIN_LABELS.has(subdomain)) {
+    return "subdomain is reserved"
+  }
+  if (!/^[a-z0-9-]+$/.test(subdomain)) {
+    return "subdomain may only contain lowercase letters, numbers, and hyphens"
+  }
+
+  return null
+}