Refactor domain lookup to utilize getDomainParts for TLD extraction and enhance WHOIS query handling with fallback options for multi-label public suffixes. Updated utility functions for improved clarity and functionality.

src/lookup.ts

@@ -2,7 +2,7 @@ import { normalizeRdap } from "./normalize-rdap.js";
 import { normalizeWhois } from "./normalize-whois.js";
 import { fetchRdapDomain, getRdapBaseUrlsForTld } from "./rdap.js";
 import type { DomainRecord, LookupOptions, LookupResult } from "./types.js";
-import { extractTld, isLikelyDomain, toISO } from "./utils.js";
+import { getDomainParts, isLikelyDomain, toISO } from "./utils.js";
 import {
   extractWhoisReferral,
   ianaWhoisServerForTld,
@@ -21,7 +21,7 @@ export async function lookupDomain(
     if (!isLikelyDomain(domain)) {
       return { ok: false, error: "Input does not look like a domain" };
     }
-    const tld = extractTld(domain);
+    const { publicSuffix, tld } = getDomainParts(domain);
     // Avoid non-null assertion: fallback to a stable ISO string if parsing ever fails
     const now =
       toISO(new Date()) ?? new Date().toISOString().replace(/\.\d{3}Z$/, "Z");
@@ -60,6 +60,7 @@ export async function lookupDomain(
     if (!whoisServer) {
       return { ok: false, error: "No WHOIS server discovered for TLD" };
     }
+    // Query the TLD server first; if it returns a referral, we follow it below.
     let res = await whoisQuery(whoisServer, domain, opts);
     if (opts?.followWhoisReferral !== false) {
       const referral = extractWhoisReferral(res.text);
@@ -71,6 +72,30 @@ export async function lookupDomain(
         }
       }
     }
+
+    // If TLD registry returns no match and there was no referral, try multi-label public suffix candidates
+    if (
+      publicSuffix.includes(".") &&
+      /no match|not found/i.test(res.text) &&
+      opts?.followWhoisReferral !== false
+    ) {
+      const candidates = [
+        `whois.nic.${publicSuffix.toLowerCase()}`,
+        // Widely used by many second-level public suffix registries
+        "whois.centralnic.com",
+      ];
+      for (const server of candidates) {
+        try {
+          const alt = await whoisQuery(server, domain, opts);
+          if (alt.text && !/error/i.test(alt.text)) {
+            res = alt;
+            break;
+          }
+        } catch {
+          // try next
+        }
+      }
+    }
     const record: DomainRecord = normalizeWhois(
       domain,
       tld,

src/utils.ts

@@ -192,10 +192,7 @@ export function sleep(ms: number): Promise<void> {
 export function extractTld(domain: string): string {
   const lower = domain.trim().toLowerCase();
   try {
-    const parsed = psl.parse?.(lower);
-    if (!("tld" in parsed)) {
-      return lower;
-    }
+    const parsed = psl.parse?.(lower) as { tld?: string };
     const suffix = parsed?.tld;
     if (suffix) {
       const labels = String(suffix).split(".").filter(Boolean);
@@ -208,6 +205,24 @@ export function extractTld(domain: string): string {
   return parts[parts.length - 1] ?? lower;
 }
 
+export function getDomainParts(domain: string): { publicSuffix: string; tld: string } {
+  const lower = domain.toLowerCase().trim();
+  let publicSuffix: string | undefined;
+  try {
+    const parsed = psl.parse?.(lower) as { tld?: string };
+    publicSuffix = parsed?.tld;
+  } catch {
+    // ignore
+  }
+  if (!publicSuffix) {
+    const parts = lower.split(".").filter(Boolean);
+    publicSuffix = parts.length ? parts[parts.length - 1] : lower;
+  }
+  const labels = publicSuffix.split(".").filter(Boolean);
+  const tld = labels.length ? labels[labels.length - 1] : publicSuffix;
+  return { publicSuffix, tld };
+}
+
 export function isLikelyDomain(input: string): boolean {
   return /^[a-z0-9.-]+$/i.test(input) && input.includes(".");
 }