index.js

import punycode from 'punycode/punycode.js';
import rules from './data/rules.js';

//
// Parse rules from file.
//
const rulesByPunySuffix = rules.reduce(
  (map, rule) => {
    const suffix = rule.replace(/^(\*\.|\!)/, '');
    const punySuffix = punycode.toASCII(suffix);
    const firstChar = rule.charAt(0);

    if (map.has(punySuffix)) {
      throw new Error(`Multiple rules found for ${rule} (${punySuffix})`);
    }

    map.set(punySuffix, {
      rule,
      suffix,
      punySuffix,
      wildcard: firstChar === '*',
      exception: firstChar === '!'
    });

    return map;
  },
  new Map(),
);

//
// Find rule for a given domain.
//
const findRule = (domain) => {
  const punyDomain = punycode.toASCII(domain);
  const punyDomainChunks = punyDomain.split('.');

  for (let i = 0; i < punyDomainChunks.length; i++) {
    const suffix = punyDomainChunks.slice(i).join('.');
    const matchingRules = rulesByPunySuffix.get(suffix);
    if (matchingRules) {
      return matchingRules;
    }
  }

  return null;
};

//
// Error codes and messages.
//
export const errorCodes = {
  DOMAIN_TOO_SHORT: 'Domain name too short.',
  DOMAIN_TOO_LONG: 'Domain name too long. It should be no more than 255 chars.',
  LABEL_STARTS_WITH_DASH: 'Domain name label can not start with a dash.',
  LABEL_ENDS_WITH_DASH: 'Domain name label can not end with a dash.',
  LABEL_TOO_LONG: 'Domain name label should be at most 63 chars long.',
  LABEL_TOO_SHORT: 'Domain name label should be at least 1 character long.',
  LABEL_INVALID_CHARS: 'Domain name label can only contain alphanumeric characters or dashes.'
};

//
// Validate domain name and throw if not valid.
//
// From wikipedia:
//
// Hostnames are composed of series of labels concatenated with dots, as are all
// domain names. Each label must be between 1 and 63 characters long, and the
// entire hostname (including the delimiting dots) has a maximum of 255 chars.
//
// Allowed chars:
//
// * `a-z`
// * `0-9`
// * `-` but not as a starting or ending character
// * `.` as a separator for the textual portions of a domain name
//
// * http://en.wikipedia.org/wiki/Domain_name
// * http://en.wikipedia.org/wiki/Hostname
//
const validate = (input) => {
  // Before we can validate we need to take care of IDNs with unicode chars.
  const ascii = punycode.toASCII(input);

  if (ascii.length < 1) {
    return 'DOMAIN_TOO_SHORT';
  }
  if (ascii.length > 255) {
    return 'DOMAIN_TOO_LONG';
  }

  // Check each part's length and allowed chars.
  const labels = ascii.split('.');
  let label;

  for (let i = 0; i < labels.length; ++i) {
    label = labels[i];
    if (!label.length) {
      return 'LABEL_TOO_SHORT';
    }
    if (label.length > 63) {
      return 'LABEL_TOO_LONG';
    }
    if (label.charAt(0) === '-') {
      return 'LABEL_STARTS_WITH_DASH';
    }
    if (label.charAt(label.length - 1) === '-') {
      return 'LABEL_ENDS_WITH_DASH';
    }
    if (!/^[a-z0-9\-_]+$/.test(label)) {
      return 'LABEL_INVALID_CHARS';
    }
  }
};

//
// Public API
//

//
// Parse domain.
//
export const parse = (input) => {
  if (typeof input !== 'string') {
    throw new TypeError('Domain name must be a string.');
  }

  // Force domain to lowercase.
  let domain = input.slice(0).toLowerCase();

  // Handle FQDN.
  // TODO: Simply remove trailing dot?
  if (domain.charAt(domain.length - 1) === '.') {
    domain = domain.slice(0, domain.length - 1);
  }

  // Validate and sanitise input.
  const error = validate(domain);
  if (error) {
    return {
      input: input,
      error: {
        message: errorCodes[error],
        code: error
      }
    };
  }

  const parsed = {
    input: input,
    tld: null,
    sld: null,
    domain: null,
    subdomain: null,
    listed: false
  };

  const domainParts = domain.split('.');

  // Non-Internet TLD
  if (domainParts[domainParts.length - 1] === 'local') {
    return parsed;
  }

  const handlePunycode = () => {
    if (!/xn--/.test(domain)) {
      return parsed;
    }
    if (parsed.domain) {
      parsed.domain = punycode.toASCII(parsed.domain);
    }
    if (parsed.subdomain) {
      parsed.subdomain = punycode.toASCII(parsed.subdomain);
    }
    return parsed;
  };

  const rule = findRule(domain);

  // Unlisted tld.
  if (!rule) {
    if (domainParts.length < 2) {
      return parsed;
    }
    parsed.tld = domainParts.pop();
    parsed.sld = domainParts.pop();
    parsed.domain = [parsed.sld, parsed.tld].join('.');
    if (domainParts.length) {
      parsed.subdomain = domainParts.pop();
    }

    return handlePunycode();
  }

  // At this point we know the public suffix is listed.
  parsed.listed = true;

  const tldParts = rule.suffix.split('.');
  const privateParts = domainParts.slice(0, domainParts.length - tldParts.length);

  if (rule.exception) {
    privateParts.push(tldParts.shift());
  }

  parsed.tld = tldParts.join('.');

  if (!privateParts.length) {
    return handlePunycode();
  }

  if (rule.wildcard) {
    tldParts.unshift(privateParts.pop());
    parsed.tld = tldParts.join('.');
  }

  if (!privateParts.length) {
    return handlePunycode();
  }

  parsed.sld = privateParts.pop();
  parsed.domain = [parsed.sld, parsed.tld].join('.');

  if (privateParts.length) {
    parsed.subdomain = privateParts.join('.');
  }

  return handlePunycode();
};

//
// Get domain.
//
export const get = (domain) => {
  if (!domain) {
    return null;
  }
  return parse(domain).domain || null;
};

//
// Check whether domain belongs to a known public suffix.
//
export const isValid = (domain) => {
  const parsed = parse(domain);
  return Boolean(parsed.domain && parsed.listed);
};

//
// List of rules from known public suffixes.
//
export { default as rules } from './data/rules.js';

export default { parse, get, isValid, rules };