import { isIP, SocketAddress } from 'node:net';
import { domainToASCII } from 'node:url';
export function normalizeHost(value: string): string | null {
const trimmedLower = trimToNull(value)?.toLowerCase();
if (!trimmedLower) return null;
const first = takeFirstHostValue(trimmedLower);
if (!first) return null;
for (const resolveCandidate of [
() => normalizeSocketAddress(first),
() => parseHostWithUrl(first),
() => normalizeBracketedIpv6(first),
]) {
const candidate = resolveCandidate();
if (candidate !== null) return candidate;
}
if (isIpV6Literal(first)) {
return normalizeHostname(first);
}
return normalizeHostname(stripPortIfPresent(first));
}
function takeFirstHostValue(value: string): string | null {
// Faster than split(',') for large forwarded headers; preserves behavior.
const commaIndex = value.indexOf(',');
const first = commaIndex === -1 ? value : value.slice(0, commaIndex);
return first ? trimToNull(first) : null;
}
function stripIpv6Brackets(value: string): string | null {
if (!value.startsWith('[')) return null;
const end = value.indexOf(']');
if (end === -1) return null;
return value.slice(1, end);
}
function stripPortIfPresent(value: string): string {
const colonIndex = value.indexOf(':');
if (colonIndex === -1) return value;
return value.slice(0, colonIndex);
}
function isIpV6Literal(value: string): boolean {
return isIP(value) === 6;
}
function normalizeSocketAddress(value: string): string | null {
const socketAddress = SocketAddress.parse(value);
if (!socketAddress) return null;
return normalizeHostname(socketAddress.address);
}
function normalizeBracketedIpv6(value: string): string | null {
const ipv6 = stripIpv6Brackets(value);
if (!ipv6) return null;
return normalizeHostname(ipv6);
}
function normalizeHostname(value: string): string | null {
const trimmed = trimToNull(value)?.toLowerCase();
if (!trimmed) return null;
if (isIP(trimmed)) return stripTrailingDots(trimmed);
const ascii = domainToASCII(trimmed);
return ascii ? stripTrailingDots(ascii) : null;
}
function parseHostWithUrl(value: string): string | null {
const candidateUrl = `http://${value}`;
if (!URL.canParse(candidateUrl)) return null;
try {
const parsed = new URL(candidateUrl);
return normalizeHostname(parsed.hostname);
} catch {
return null;
}
}
function trimToNull(value: string): string | null {
const trimmed = value.trim();
return trimmed ? trimmed : null;
}
function stripTrailingDots(value: string): string {
// Keep loop (rather than regex) to preserve exact behavior and avoid hidden allocations.
let result = value;
while (result.endsWith('.')) result = result.slice(0, -1);
return result;
}
