js/src/extractUrlsWithIndices.js

// Copyright 2018 Twitter, Inc.
// Licensed under the Apache License, Version 2.0
// http://www.apache.org/licenses/LICENSE-2.0

import extractUrl from './regexp/extractUrl';
import invalidUrlWithoutProtocolPrecedingChars from './regexp/invalidUrlWithoutProtocolPrecedingChars';
import idna from './lib/idna';
import validAsciiDomain from './regexp/validAsciiDomain';
import validTcoUrl from './regexp/validTcoUrl';

const DEFAULT_PROTOCOL = 'https://';
const DEFAULT_PROTOCOL_OPTIONS = { extractUrlsWithoutProtocol: true };
const MAX_URL_LENGTH = 4096;
const MAX_TCO_SLUG_LENGTH = 40;

const extractUrlsWithIndices = function(text, options = DEFAULT_PROTOCOL_OPTIONS) {
  if (!text || (options.extractUrlsWithoutProtocol ? !text.match(/\./) : !text.match(/:/))) {
    return [];
  }

  const urls = [];

  while (extractUrl.exec(text)) {
    const before = RegExp.$2;
    let url = RegExp.$3;
    const protocol = RegExp.$4;
    const domain = RegExp.$5;
    const path = RegExp.$7;
    let endPosition = extractUrl.lastIndex;
    const startPosition = endPosition - url.length;

    if (!isValidUrl(url, protocol || DEFAULT_PROTOCOL, domain)) {
      continue;
    }
    // extract ASCII-only domains.
    if (!protocol) {
      if (!options.extractUrlsWithoutProtocol || before.match(invalidUrlWithoutProtocolPrecedingChars)) {
        continue;
      }

      let lastUrl = null;
      let asciiEndPosition = 0;
      domain.replace(validAsciiDomain, function(asciiDomain) {
        const asciiStartPosition = domain.indexOf(asciiDomain, asciiEndPosition);
        asciiEndPosition = asciiStartPosition + asciiDomain.length;
        lastUrl = {
          url: asciiDomain,
          indices: [startPosition + asciiStartPosition, startPosition + asciiEndPosition]
        };
        urls.push(lastUrl);
      });

      // no ASCII-only domain found. Skip the entire URL.
      if (lastUrl == null) {
        continue;
      }

      // lastUrl only contains domain. Need to add path and query if they exist.
      if (path) {
        lastUrl.url = url.replace(domain, lastUrl.url);
        lastUrl.indices[1] = endPosition;
      }
    } else {
      // In the case of t.co URLs, don't allow additional path characters.
      if (url.match(validTcoUrl)) {
        const tcoUrlSlug = RegExp.$1;
        if (tcoUrlSlug && tcoUrlSlug.length > MAX_TCO_SLUG_LENGTH) {
          continue;
        } else {
          url = RegExp.lastMatch;
          endPosition = startPosition + url.length;
        }
      }
      urls.push({
        url: url,
        indices: [startPosition, endPosition]
      });
    }
  }

  return urls;
};

const isValidUrl = function(url, protocol, domain) {
  let urlLength = url.length;
  const punycodeEncodedDomain = idna.toAscii(domain);
  if (!punycodeEncodedDomain || !punycodeEncodedDomain.length) {
    return false;
  }

  urlLength = urlLength + punycodeEncodedDomain.length - domain.length;
  return protocol.length + urlLength <= MAX_URL_LENGTH;
};

export default extractUrlsWithIndices;