<?php
/**
* Parses HTML into a tree of tags.
*
* @package XenForo_Html
*/
class XenForo_Html_Parser
{
/**
* String of HTML to be parsed.
*
* @var string
*/
protected $_html = '';
/**
* Length of the HTML string.
*
* @var integer
*/
protected $_length = 0;
/**
* Current position in the HTML string.
*
* @var integer
*/
protected $_position = 0;
/**
* @var XenForo_Html_Tag
*/
protected $_rootTag = null;
/**
* @var XenForo_Html_Tag
*/
protected $_currentTag = null;
/**
* Constructor. Sets up HTML.
*
* @param string $html HTML to parse
*/
public function __construct($html)
{
$this->_html = $html;
$this->_length = strlen($html);
}
/**
* Parses the HTML.
*
* @return XenForo_Html_Tag The root tag of the tree. This tag isn't really in the tree, so traversal should start with its children.
*/
public function parse()
{
$this->_currentTag = $this->_rootTag = new XenForo_Html_Tag('');
do
{
$text = $this->readUntilString('<');
if ($text === false)
{
break;
}
$this->appendText($text);
$currentPosition = $this->_position;
$this->step();
if (!$this->stateTag())
{
$this->appendText(substr($this->_html, $currentPosition, $this->_position - $currentPosition));
}
}
while ($this->_position < $this->_length);
$this->appendText($this->readUntilEnd());
return $this->_rootTag;
}
/**
* Function is called when entering the tag state. The opening < has been found and passed.
*
* @return boolean True if tag was parsed; if false, the tag is treated as plain text
*/
public function stateTag()
{
switch ($this->peak())
{
case '/': // closing tag
$this->step();
$isClose = true;
break;
case '!': // comment, ignore it
$this->step();
$commentEnd = $this->readUntilString('-->');
if ($commentEnd !== false)
{
$this->step();
$this->step();
$this->step();
}
return true; // tag was handled
default:
$isClose = false;
}
$tagName = $this->readUntilCharacters(" \t\r\n/>");
if ($tagName === '' || $tagName === false)
{
return false;
}
$isSelfClose = false;
$attributes = array();
do
{
switch ($this->step())
{
case '/':
if ($this->peak() == '>')
{
$this->step();
$isSelfClose = true;
}
break 2;
case '>':
break 2;
// otherwise it's whitespace
}
$this->skipWhiteSpace();
if (!$this->stateAttribute($attributes))
{
return false;
}
}
while ($this->_position < $this->_length);
$tagName = strtolower($tagName);
if ($isClose)
{
$this->pushTagClose($tagName);
}
else
{
$childTag = $this->pushTagOpen($tagName, $attributes);
if ($isSelfClose && !$childTag->isVoid())
{
$this->pushTagClose($tagName);
}
}
return true;
}
/**
* Function is called when entering the attribute state.
*
* @param array $attributes Existing attribute list. New attributes are pushed onto this.
*
* @return boolean If false is returned, the containing tag is considered invalid and treated as text
*/
public function stateAttribute(array &$attributes)
{
$attributeName = $this->readUntilCharacters(" \t\r\n/>=");
if ($attributeName === false)
{
return false;
}
if ($this->peak() == '=')
{
$this->step();
$this->skipWhiteSpace();
$delimiter = $this->peak();
switch ($delimiter)
{
case '"':
case "'":
$this->step();
$attributeValue = $this->readUntilString($delimiter);
$this->step();
break;
default:
$attributeValue = $this->readUntilCharacters(" \t\r\n>");
if (substr($attributeValue, -1) == '/' && $this->peak() == '>')
{
// match a "/" in an unquoted attr, unless it's the last value
$attributeValue = substr($attributeValue, 0, -1);
$this->stepBack();
}
}
if ($attributeValue === false)
{
return false;
}
}
else
{
$attributeValue = $attributeName;
}
if ($attributeName !== '')
{
$attributes[strtolower($attributeName)] = $attributeValue;
}
return true;
}
/**
* Parses CSS into its component rules.
*
* @param string $css
*
* @return array Key-value rule pairs
*/
public function parseCss($css)
{
// TODO: this isn't completely correct and should be revisited
$rules = array();
preg_match_all('/(?<=^|\W)([a-z0-9-]+)\s*:\s*?(.*)\s*?(;|$)/siU', $css, $matches, PREG_SET_ORDER);
foreach ($matches AS $match)
{
$match[2] = trim(preg_replace('/!\s*important$/i', '', trim($match[2])));
if (strlen($match[2]) == 0)
{
continue; // parse empty rules, but ignore them
}
$rules[strtolower($match[1])] = $match[2];
}
return $rules;
}
/**
* Read until (but not including) the given string is found.
*
* @param string $string
*
* @return false|string False if the string is not found; otherwise, text to string
*/
public function readUntilString($string)
{
$foundPosition = strpos($this->_html, $string, $this->_position);
if ($foundPosition === false)
{
return false;
}
else if ($foundPosition == $this->_position)
{
return '';
}
else
{
$string = substr($this->_html, $this->_position, $foundPosition - $this->_position);
$this->_position = $foundPosition;
return $string;
}
}
/**
* Read until one of the characters is found.
*
* @param string $characters List of characters
*
* @return false|string False if the none of the characters are found; otherwise, text to first character found
*/
public function readUntilCharacters($characters)
{
$length = strcspn($this->_html, $characters, $this->_position);
if ($length == 0)
{
return '';
}
else if ($length + $this->_position == $this->_length)
{
return false;
}
else
{
$string = substr($this->_html, $this->_position, $length);
$this->_position += $length;
return $string;
}
}
/**
* Skip over any amount of whitespace.
*/
public function skipWhiteSpace()
{
$length = strspn($this->_html, " \t\r\n", $this->_position);
$this->_position += $length;
}
/**
* Read until the end of the string.
*
* @return false|string False if at the end; otherwise, text until end
*/
public function readUntilEnd()
{
if ($this->_position >= $this->_length)
{
return false;
}
$string = substr($this->_html, $this->_position);
$this->_position = $this->_length;
return $string;
}
/**
* Read the current character and advance one position.
*
* @return string
*/
public function step()
{
if (!isset($this->_html[$this->_position]))
{
return false;
}
$value = $this->_html[$this->_position];
$this->_position++;
return $value;
}
public function stepBack()
{
if ($this->_position > 0)
{
$this->_position--;
}
}
/**
* Peak at the current character without changing the current position.
*
* @return false|string False if past the end; character otherwise
*/
public function peak()
{
if (isset($this->_html[$this->_position]))
{
return $this->_html[$this->_position];
}
else
{
return false;
}
}
/**
* Appends text to the current tag. Text is cleaned of HTML entities first.
*
* @param string|false $text Text to append; false is ignored
*/
public function appendText($text)
{
if ($text !== '' && $text !== false)
{
$this->_currentTag->appendText($this->decodeEntities($text));
}
}
/**
* Push a tag close to the current tag and have it return the new
* value for the current tag.
*
* @param string $tagName
*/
public function pushTagClose($tagName)
{
$this->_currentTag = $this->_currentTag->closeTag($tagName);
if (!$this->_currentTag)
{
$this->_currentTag = $this->_rootTag;
}
}
/**
* Push a tag open.
*
* @param string $tagName
* @param array $attributes Key-value attributes; cleaned of HTML entities within function
*
* @return XenForo_Html_Tag Child tag that was added
*/
public function pushTagOpen($tagName, array $attributes)
{
$cleanAttributes = array();
foreach ($attributes AS $attributeName => $attribute)
{
$cleanAttributes[$this->decodeEntities($attributeName)] = $this->decodeEntities($attribute);
}
if (!empty($cleanAttributes['style']))
{
$cleanAttributes['style'] = $this->parseCss($cleanAttributes['style']);
}
$childTag = $this->_currentTag->addChildTag($tagName, $cleanAttributes);
if (!$childTag->isVoid())
{
$this->_currentTag = $childTag;
}
return $childTag;
}
/**
* Decodes HTML entities in a string. Note that non-breaking spaces are treated as normal spaces.
*
* @param string $string
*
* @return string Decoded string
*/
public function decodeEntities($string)
{
return html_entity_decode($string, ENT_QUOTES, 'UTF-8');
}
/**
* Debug helper to print the tag tree in HTML format.
*
* @param XenForo_Html_Tag $tag Current/root tag
* @param string $prefix Prefix for each line
*/
public function printTags(XenForo_Html_Tag $tag, $prefix = '')
{
echo $prefix . 'Tag: ' . $tag->tagName() . ' ' . json_encode($tag->attributes()) . "<br />\n";
$childPrefix = "$prefix ";
foreach($tag->children() AS $child)
{
if ($child instanceof XenForo_Html_Tag)
{
$this->printTags($child, $childPrefix);
}
else
{
echo $childPrefix . "'" . htmlspecialchars($child) . "'<br />\n";
}
}
}
}