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<?php
namespace andreskrey\Readability;
use DOMDocument;
/**
* Class HTMLParser.
*
* A helper class to parse HTML and get a Readability object.
*/
class HTMLParser
{
/**
* @var DOMDocument
*/
private $dom = null;
/**
* @var array
*/
private $metadata = [];
/**
* @var array
*/
private $title = [];
/**
* @var array
*/
private $elementsToScore = [];
/**
* @var array
*/
private $regexps = [
'unlikelyCandidates' => '/banner|combx|comment|community|disqus|extra|foot|header|menu|modal|related|remark|rss|share|shoutbox|sidebar|skyscraper|sponsor|ad-break|agegate|pagination|pager|popup/i',
'okMaybeItsACandidate' => '/and|article|body|column|main|shadow/i',
'extraneous' => '/print|archive|comment|discuss|e[\-]?mail|share|reply|all|login|sign|single|utility/i',
'byline' => '/byline|author|dateline|writtenby|p-author/i',
'replaceFonts' => '/<(\/?)font[^>]*>/gi',
'normalize' => '/\s{2,}/g',
'videos' => '/\/\/(www\.)?(dailymotion|youtube|youtube-nocookie|player\.vimeo)\.com/i',
'nextLink' => '/(next|weiter|continue|>([^\|]|$)|»([^\|]|$))/i',
'prevLink' => '/(prev|earl|old|new|<|«)/i',
'whitespace' => '/^\s*$/',
'hasContent' => '/\S$/',
];
private $defaultTagsToScore = [
'section',
'h2',
'h3',
'h4',
'h5',
'h6',
'p',
'td',
'pre',
];
/**
* @var array
*/
private $alterToDIVExceptions = [
'div',
'article',
'section',
'p',
// TODO, check if this is correct, #text elements do not exist in js
'#text',
];
/**
* Constructor.
*
* @param array $options Options to override the default ones
*/
public function __construct(array $options = [])
{
$defaults = [
'maxTopCandidates' => 5, // Max amount of top level candidates
'articleByLine' => null,
];
$this->environment = Environment::createDefaultEnvironment($defaults);
$this->environment->getConfig()->merge($options);
$this->dom = new DOMDocument('1.0', 'utf-8');
// To avoid having a gazillion of errors on malformed HTMLs
libxml_use_internal_errors(true);
}
/**
* Parse the html. This is the main entry point of the HTMLParser.
*
* @param string $html Full html of the website, page, etc.
*
* #return ? TBD
*/
public function parse($html)
{
$this->loadHTML($html);
$this->removeScripts();
$this->metadata = $this->getMetadata();
$this->title = $this->getTitle();
if (!($root = $this->dom->getElementsByTagName('body')->item(0))) {
throw new \InvalidArgumentException('Invalid HTML was provided');
}
// TODO: Check if this is correct. Originally the body was sent as root but this caused problems because
// the script wasn't able to find nextSiblings to scan the dom tree. Now we are sending the first child.
// Is this correct?
$root = new Readability($root->firstChild);
$this->getNodes($root);
$result = $this->rateNodes($this->elementsToScore);
// Todo, fix return, check for values, maybe create a function to create the return object
return [
'title' => $this->metadata['title'],
'author' => $this->metadata['author'],
'article' => $result
];
}
/**
* @param string $html
*/
private function loadHTML($html)
{
$this->dom->loadHTML($html);
$this->dom->encoding = 'UTF-8';
}
/**
* @return Configuration
*/
public function getConfig()
{
return $this->environment->getConfig();
}
/**
* Removes all the scripts of the html.
*
* @TODO is this really necessary? Readability.js uses it to chop any script that might interfere with their
* system. Is it necessary here?
*/
private function removeScripts()
{
while ($script = $this->dom->getElementsByTagName('script')) {
if ($script->item(0)) {
$script->item(0)->parentNode->removeChild($script->item(0));
} else {
break;
}
}
}
/**
* Tries to guess relevant info from metadata of the html.
*
* @return array Metadata info. May have title, excerpt and or byline.
*/
private function getMetadata()
{
$metadata = [];
foreach ($this->dom->getElementsByTagName('meta') as $meta) {
/* @var Readability $meta */
$name = $meta->getAttribute('name');
$property = $meta->getAttribute('property');
// Select either name or property
$item = ($name ? $name : $property);
if ($item == 'og:title' || $item == 'twitter:title') {
$metadata['title'] = $meta->getAttribute('content');
}
if ($item == 'og:description' || $item == 'twitter:description') {
$metadata['excerpt'] = $meta->getAttribute('content');
}
if ($item == 'author') {
$metadata['byline'] = $meta->getAttribute('content');
}
}
return $metadata;
}
/**
* Get the density of links as a percentage of the content
* This is the amount of text that is inside a link divided by the total text in the node.
*
* @param Readability $readability
*
* @return int
*/
public function getLinkDensity($readability)
{
$linkLength = 0;
$textLength = strlen($readability->getTextContent(true));
if (!$textLength) {
return 0;
}
$links = $readability->getAllLinks();
if ($links) {
/** @var Readability $link */
foreach ($links as $link) {
$linkLength += strlen($link->getTextContent(true));
}
}
return $linkLength / $textLength;
}
/**
* Returns the title of the html. Prioritizes the title from the metadata against the title tag.
*
* @return string|null
*/
private function getTitle()
{
if (isset($this->metadata['title'])) {
return $this->metadata['title'];
}
$title = $this->dom->getElementsByTagName('title');
if ($title) {
return $title->item(0)->nodeValue;
}
return null;
}
/**
* Gets nodes from the root element.
*
* @param $node Readability
*/
private function getNodes(Readability $node)
{
while ($node) {
$matchString = $node->getAttribute('class') . ' ' . $node->getAttribute('id');
// Check to see if this node is a byline, and remove it if it is.
if ($this->checkByline($node, $matchString)) {
$node = $node->removeAndGetNext($node);
continue;
}
// Avoid elements that are unlikely to have any useful information.
if (
preg_match($this->regexps['unlikelyCandidates'], $matchString) &&
!preg_match($this->regexps['okMaybeItsACandidate'], $matchString) &&
!$node->tagNameEqualsTo('body') &&
!$node->tagNameEqualsTo('a')
) {
$node = $node->removeAndGetNext($node);
continue;
}
if (in_array(strtolower($node->getTagName()), $this->defaultTagsToScore)) {
$this->elementsToScore[] = $node;
}
// Check for nodes that have only on P node as a child and convert them to a single P node
if ($node->hasSinglePNode()) {
$pNode = $node->getChildren();
$node = $pNode[0];
// If there's any info on the node, add it to the elements to score in the next step.
if ($node->getValue(true)) {
$this->elementsToScore[] = $node;
}
}
// TODO Unfuck this:
$node = $node->getNextNode($node);
}
}
/**
* Assign scores to each node. This function will rate each node and return a Readability object for each one.
*
* @param array $nodes
* @return DOMDocument
*/
private function rateNodes($nodes)
{
$candidates = [];
/** @var Readability $node */
foreach ($nodes as $node) {
// Discard nodes with less than 25 characters, without blank space
if (strlen($node->getValue(true)) < 25) {
continue;
}
$ancestors = $node->getNodeAncestors();
// Exclude nodes with no ancestor
if ($ancestors === 0) {
continue;
}
// Start with a point for the paragraph itself as a base.
$contentScore = 1;
// Add points for any commas within this paragraph.
$contentScore += count(explode(', ', $node->getValue(true)));
// For every 100 characters in this paragraph, add another point. Up to 3 points.
$contentScore += min(floor(strlen($node->getValue(true)) / 100), 3);
// Initialize and score ancestors.
/** @var Readability $ancestor */
foreach ($ancestors as $level => $ancestor) {
$readability = $ancestor->initializeNode();
/*
* Node score divider:
* - parent: 1 (no division)
* - grandparent: 2
* - great grandparent+: ancestor level * 3
*/
if ($level === 0) {
$scoreDivider = 1;
} elseif ($level === 1) {
$scoreDivider = 2;
} else {
$scoreDivider = $level * 3;
}
$currentScore = $readability->getContentScore();
$readability->setContentScore($currentScore + ($contentScore / $scoreDivider));
$candidates[] = $readability;
}
}
/*
* After we've calculated scores, loop through all of the possible
* candidate nodes we found and find the one with the highest score.
*/
$topCandidates = [];
foreach ($candidates as $candidate) {
/*
* Scale the final candidates score based on link density. Good content
* should have a relatively small link density (5% or less) and be mostly
* unaffected by this operation.
*/
$candidate->setContentScore($candidate->getContentScore() * (1 - $this->getLinkDensity($candidate)));
for ($i = 0; $i < $this->getConfig()->getOption('maxTopCandidates'); $i++) {
$aTopCandidate = isset($topCandidates[$i]) ? $topCandidates[$i] : null;
if (!$aTopCandidate || $candidate->getContentScore() > $aTopCandidate->getContentScore()) {
array_splice($topCandidates, $i, 0, [$candidate]);
if (count($topCandidates) > $this->getConfig()->getOption('maxTopCandidates')) {
array_pop($topCandidates);
}
break;
}
}
}
$topCandidate = isset($topCandidates[0]) ? $topCandidates[0] : null;
$neededToCreateTopCandidate = false;
/*
* If we still have no top candidate, just use the body as a last resort.
* We also have to copy the body node so it is something we can modify.
*/
if ($topCandidate === null || $topCandidate->tagNameEqualsTo('body')) {
// Move all of the page's children into topCandidate
// TODO TEST THIS!
$topCandidate = new Readability($this->dom->getElementsByTagName('body')->item(0));
$topCandidate->initializeNode();
} elseif ($topCandidate) {
/*
* Because of our bonus system, parents of candidates might have scores
* themselves. They get half of the node. There won't be nodes with higher
* scores than our topCandidate, but if we see the score going *up* in the first
* few steps up the tree, that's a decent sign that there might be more content
* lurking in other places that we want to unify in. The sibling stuff
* below does some of that - but only if we've looked high enough up the DOM
* tree.
*/
// TODO, while calling getParent, the new object should carry its own score.
// Should be calculated when gets created or we must nest all Readability objects to carry their own score?
$parentOfTopCandidate = $topCandidate->getParent();
$lastScore = $topCandidate->getContentScore();
// The scores shouldn't get too low.
$scoreThreshold = $lastScore / 3;
while ($parentOfTopCandidate) {
/* @var Readability $parentOfTopCandidate */
$parentScore = $parentOfTopCandidate->getContentScore();
if ($parentScore < $scoreThreshold) {
break;
}
if ($parentScore > $lastScore) {
// Alright! We found a better parent to use.
$topCandidate = $parentOfTopCandidate;
break;
}
$lastScore = $parentOfTopCandidate->getContentScore();
$parentOfTopCandidate = $parentOfTopCandidate->getParent();
}
}
/*
* Now that we have the top candidate, look through its siblings for content
* that might also be related. Things like preambles, content split by ads
* that we removed, etc.
*/
$articleContent = new DOMDocument();
$articleContent->createElement('div');
$siblingScoreThreshold = max(10, $topCandidate->getContentScore() * 0.2);
$siblings = $topCandidate->getChildren();
/** @var Readability $sibling */
foreach ($siblings as $sibling) {
$append = false;
// TODO Check if this comparison working as expected
// On the original js project it was a simple $sibling == $topCandidate comparison.
if ($this->compareNodes($sibling, $topCandidate)) {
$append = true;
} else {
$contentBonus = 0;
// Give a bonus if sibling nodes and top candidates have the example same classname
if ($sibling->getAttribute('class') === $topCandidate->getAttribute('class') && $topCandidate->getAttribute('class') !== '') {
$contentBonus += $topCandidate->getContentScore() * 0.2;
}
if ($sibling->getContentScore() + $contentBonus >= $siblingScoreThreshold) {
$append = true;
} elseif ($sibling->tagNameEqualsTo('p')) {
$linkDensity = $this->getLinkDensity($sibling);
$nodeContent = $sibling->getTextContent(true);
if (strlen($nodeContent) > 80 && $linkDensity < 0.25) {
$append = true;
// TODO Check if pregmatch is working as expected
} elseif ($nodeContent && strlen($nodeContent) < 80 && $linkDensity === 0 && preg_match('//\.( |$)/', $nodeContent)) {
$append = true;
}
}
}
if ($append) {
if (in_array(strtolower($sibling->getTagName()), $this->alterToDIVExceptions)) {
/*
* We have a node that isn't a common block level element, like a form or td tag.
* Turn it into a div so it doesn't get filtered out later by accident.
*/
// TODO This is not working! Fix!
// $sibling->setNodeName('div');
}
$import = $articleContent->importNode($sibling->getDOMNode(), true);
$articleContent->appendChild($import);
}
}
return $articleContent;
}
private function checkByline($node, $matchString)
{
if (!$this->getConfig()->getOption('articleByLine')) {
return false;
}
$rel = $node->getAttribute('rel');
if ($rel === 'author' || preg_match($this->regexps['byline'], $matchString) && $this->isValidByline($node->getTextContent())) {
$this->metadata['byline'] = trim($node->getTextContent());
return true;
}
return false;
}
private function isValidByline($text)
{
if (gettype($text) == 'string') {
$byline = trim($text);
return (strlen($byline) > 0) && (strlen($text) < 100);
}
return false;
}
private function compareNodes($node1, $node2)
{
if ($node1->getTagName() !== $node2->getTagName()) {
return false;
}
if ($node1->getTextContent() !== $node2->getTextContent()) {
return false;
}
return true;
}
}
|