@helia/verified-fetch/src/utils/dnslink-label.ts

A fetch-like API for obtaining verified & trustless IPFS content on the web

/**
 * For DNSLink see https://specs.ipfs.tech/http-gateways/subdomain-gateway/#host-request-header
 * DNSLink names include . which means they must be inlined into a single DNS label to provide unique origin and work with wildcard TLS certificates.
 */

// DNS label can have up to 63 characters, consisting of alphanumeric
// characters or hyphens -, but it must not start or end with a hyphen.
const dnsLabelRegex = /^[a-zA-Z0-9]([a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?$/

/**
 * Checks if label looks like inlined DNSLink.
 * (https://specs.ipfs.tech/http-gateways/subdomain-gateway/#host-request-header)
 */
export function isInlinedDnsLink (label: string): boolean {
  return dnsLabelRegex.test(label) && label.includes('-') && !label.includes('.')
}

/**
 * DNSLink label decoding
 * - Every standalone - is replaced with .
 * - Every remaining -- is replaced with -
 *
 * @example en-wikipedia--on--ipfs-org -> en.wikipedia-on-ipfs.org
 */
export function decodeDNSLinkLabel (label: string): string {
  return label.replace(/--/g, '%').replace(/-/g, '.').replace(/%/g, '-')
}

/**
 * DNSLink label encoding
 * - Every - is replaced with --
 * - Every . is replaced with -
 *
 * @example en.wikipedia-on-ipfs.org -> en-wikipedia--on--ipfs-org
 */
export function encodeDNSLinkLabel (name: string): string {
  return name.replace(/-/g, '--').replace(/\./g, '-')
}