Implement WHOIS referral chain collection and merging logic (fixes #11)

- Introduced `collectWhoisReferralChain` to gather WHOIS responses while avoiding contradictory data from registrars.
- Updated `lookupDomain` to utilize the new chain collection method, ensuring TLD responses are prioritized.
- Added `mergeWhoisRecords` function to consolidate WHOIS data from multiple sources.
- Enhanced tests for referral handling and merging behavior, ensuring accurate data retention across scenarios.

src/index.ts

@@ -9,8 +9,12 @@ import {
   ianaWhoisServerForTld,
   parseIanaRegistrationInfoUrl,
 } from "./whois/discovery";
+import { mergeWhoisRecords } from "./whois/merge";
 import { normalizeWhois } from "./whois/normalize";
-import { followWhoisReferrals } from "./whois/referral";
+import {
+  collectWhoisReferralChain,
+  followWhoisReferrals,
+} from "./whois/referral";
 
 /**
  * High-level lookup that prefers RDAP and falls back to WHOIS.
@@ -32,7 +36,13 @@ export async function lookupDomain(
 
     // If WHOIS-only, skip RDAP path
     if (!opts?.whoisOnly) {
-      const bases = await getRdapBaseUrlsForTld(tld, opts);
+      let bases = await getRdapBaseUrlsForTld(tld, opts);
+      // Some ccTLD registries publish RDAP only at the registry TLD (e.g., br),
+      // while the public suffix can be multi-label (e.g., com.br). Fallback to last label.
+      if (bases.length === 0 && tld.includes(".")) {
+        const registryTld = tld.split(".").pop() ?? tld;
+        bases = await getRdapBaseUrlsForTld(registryTld, opts);
+      }
       const tried: string[] = [];
       for (const base of bases) {
         tried.push(base);
@@ -80,16 +90,28 @@ export async function lookupDomain(
     }
 
     // Query the TLD server first; optionally follow registrar referrals (multi-hop)
-    const res = await followWhoisReferrals(whoisServer, domain, opts);
+    // Collect the chain and coalesce so we don't lose details when a registrar returns minimal/empty data.
+    const chain = await collectWhoisReferralChain(whoisServer, domain, opts);
+    if (chain.length === 0) {
+      // Fallback to previous behavior as a safety net
+      const res = await followWhoisReferrals(whoisServer, domain, opts);
+      const record: DomainRecord = normalizeWhois(
+        domain,
+        tld,
+        res.text,
+        res.serverQueried,
+        !!opts?.includeRaw,
+      );
+      return { ok: true, record };
+    }
 
-    const record: DomainRecord = normalizeWhois(
-      domain,
-      tld,
-      res.text,
-      res.serverQueried,
-      !!opts?.includeRaw,
+    // Normalize all WHOIS texts in the chain and merge conservatively
+    const normalizedRecords = chain.map((r) =>
+      normalizeWhois(domain, tld, r.text, r.serverQueried, !!opts?.includeRaw),
     );
-    return { ok: true, record };
+    const [first, ...rest] = normalizedRecords;
+    const mergedRecord = rest.length ? mergeWhoisRecords(first, rest) : first;
+    return { ok: true, record: mergedRecord };
   } catch (err: unknown) {
     const message = err instanceof Error ? err.message : String(err);
     return { ok: false, error: message };