SingleFile/extension/lib/readability/Readability-readerable.js

/* eslint-env es6:false */
/* globals exports */
/*
 * Copyright (c) 2010 Arc90 Inc
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * This code is heavily based on Arc90's readability.js (1.7.1) script
 * available at: http://code.google.com/p/arc90labs-readability
 */

var REGEXPS = {
    // NOTE: These two regular expressions are duplicated in
    // Readability.js. Please keep both copies in sync.
    unlikelyCandidates: /-ad-|ai2html|banner|breadcrumbs|combx|comment|community|cover-wrap|disqus|extra|footer|gdpr|header|legends|menu|related|remark|replies|rss|shoutbox|sidebar|skyscraper|social|sponsor|supplemental|ad-break|agegate|pagination|pager|popup|yom-remote/i,
    okMaybeItsACandidate: /and|article|body|column|content|main|shadow/i,
  };
  
  function isNodeVisible(node) {
    // Have to null-check node.style to deal with SVG and MathML nodes.
    return (!node.style || node.style.display != "none") && !node.hasAttribute("hidden")
      && (!node.hasAttribute("aria-hidden") || node.getAttribute("aria-hidden") != "true");
  }
  
  /**
   * Decides whether or not the document is reader-able without parsing the whole thing.
   *
   * @return boolean Whether or not we suspect Readability.parse() will suceeed at returning an article object.
   */
  function isProbablyReaderable(doc, isVisible) {
    if (!isVisible) {
      isVisible = isNodeVisible;
    }
  
    var nodes = doc.querySelectorAll("p, pre");
  
    // Get <div> nodes which have <br> node(s) and append them into the `nodes` variable.
    // Some articles' DOM structures might look like
    // <div>
    //   Sentences<br>
    //   <br>
    //   Sentences<br>
    // </div>
    var brNodes = doc.querySelectorAll("div > br");
    if (brNodes.length) {
      var set = new Set(nodes);
      [].forEach.call(brNodes, function(node) {
        set.add(node.parentNode);
      });
      nodes = Array.from(set);
    }
  
    var score = 0;
    // This is a little cheeky, we use the accumulator 'score' to decide what to return from
    // this callback:
    return [].some.call(nodes, function(node) {
      if (!isVisible(node))
        return false;
  
      var matchString = node.className + " " + node.id;
      if (REGEXPS.unlikelyCandidates.test(matchString) &&
          !REGEXPS.okMaybeItsACandidate.test(matchString)) {
        return false;
      }
  
      if (node.matches("li p")) {
        return false;
      }
  
      var textContentLength = node.textContent.trim().length;
      if (textContentLength < 140) {
        return false;
      }
  
      score += Math.sqrt(textContentLength - 140);
  
      if (score > 20) {
        return true;
      }
      return false;
    });
  }
  
  if (typeof exports === "object") {
    exports.isProbablyReaderable = isProbablyReaderable;
  }