// v0.4.1 - https://github.com/mozilla/readability/commit/28843b6de84447dd6cef04058fda336938e628dc

/* eslint-env es6:false */
/*
 * 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 and node.className.indexOf to deal with SVG and MathML nodes.
	return (!node.style || node.style.display != "none")
	  && !node.hasAttribute("hidden")
	  //check for "fallback-image" so that wikimedia math images are displayed
	  && (!node.hasAttribute("aria-hidden") || node.getAttribute("aria-hidden") != "true" || (node.className && node.className.indexOf && node.className.indexOf("fallback-image") !== -1));
  }
  
  /**
   * Decides whether or not the document is reader-able without parsing the whole thing.
   * @param {Object} options Configuration object.
   * @param {number} [options.minContentLength=140] The minimum node content length used to decide if the document is readerable.
   * @param {number} [options.minScore=20] The minumum cumulated 'score' used to determine if the document is readerable.
   * @param {Function} [options.visibilityChecker=isNodeVisible] The function used to determine if a node is visible.
   * @return {boolean} Whether or not we suspect Readability.parse() will suceeed at returning an article object.
   */
  function isProbablyReaderable(doc, options = {}) {
	// For backward compatibility reasons 'options' can either be a configuration object or the function used
	// to determine if a node is visible.
	if (typeof options == "function") {
	  options = { visibilityChecker: options };
	}
  
	var defaultOptions = { minScore: 20, minContentLength: 140, visibilityChecker: isNodeVisible };
	options = Object.assign(defaultOptions, options);
  
	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 (!options.visibilityChecker(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 < options.minContentLength) {
		return false;
	  }
  
	  score += Math.sqrt(textContentLength - options.minContentLength);
  
	  if (score > options.minScore) {
		return true;
	  }
	  return false;
	});
  }
  
  if (typeof module === "object") {
	module.exports = isProbablyReaderable;
  }