<?php
//phpcs:disable
namespace BWF_Pelago;

/**
 * This class provides functions for converting CSS styles into inline style attributes in your HTML code.
 *
 * For more information, please see the README.md file.
 *
 * @author Cameron Brooks
 * @author Jaime Prado
 * @author Oliver Klee <github@oliverklee.de>
 * @author Roman Ožana <ozana@omdesign.cz>
 * @author Sander Kruger <s.kruger@invessel.com>
 * @author Zoli Szabó <zoli.szabo+github@gmail.com>
 */
class Emogrifier_V1 {
	/**
	 * @var int
	 */
	const CACHE_KEY_CSS = 0;

	/**
	 * @var int
	 */
	const CACHE_KEY_SELECTOR = 1;

	/**
	 * @var int
	 */
	const CACHE_KEY_XPATH = 2;

	/**
	 * @var int
	 */
	const CACHE_KEY_CSS_DECLARATIONS_BLOCK = 3;

	/**
	 * @var int
	 */
	const CACHE_KEY_COMBINED_STYLES = 4;

	/**
	 * for calculating nth-of-type and nth-child selectors
	 *
	 * @var int
	 */
	const INDEX = 0;

	/**
	 * for calculating nth-of-type and nth-child selectors
	 *
	 * @var int
	 */
	const MULTIPLIER = 1;

	/**
	 * @var string
	 */
	const ID_ATTRIBUTE_MATCHER = '/(\\w+)?\\#([\\w\\-]+)/';

	/**
	 * @var string
	 */
	const CLASS_ATTRIBUTE_MATCHER = '/(\\w+|[\\*\\]])?((\\.[\\w\\-]+)+)/';

	/**
	 * Regular expression component matching a static pseudo class in a selector, without the preceding ":",
	 * for which the applicable elements can be determined (by converting the selector to an XPath expression).
	 * (Contains alternation without a group and is intended to be placed within a capturing, non-capturing or lookahead
	 * group, as appropriate for the usage context.)
	 *
	 * @var string
	 */
	const PSEUDO_CLASS_MATCHER = '\\S+\\-(?:child|type\\()|not\\([[:ascii:]]*\\)';

	/**
	 * @var string
	 */
	const CONTENT_TYPE_META_TAG = '<meta http-equiv="Content-Type" content="text/html; charset=utf-8">';

	/**
	 * @var string
	 */
	const DEFAULT_DOCUMENT_TYPE = '<!DOCTYPE html>';

	/**
	 * @var string Regular expression part to match tag names that PHP's DOMDocument implementation is not aware are
	 *      self-closing. These are mostly HTML5 elements, but for completeness <command> (obsolete) and <keygen>
	 *      (deprecated) are also included.
	 *
	 * @see https://bugs.php.net/bug.php?id=73175
	 */
	const PHP_UNRECOGNIZED_VOID_TAGNAME_MATCHER = '(?:command|embed|keygen|source|track|wbr)';

	/**
	 * @var \DOMDocument
	 */
	protected $domDocument = null;

	/**
	 * @var string
	 */
	private $css = '';

	/**
	 * @var bool[]
	 */
	private $excludedSelectors = [];

	/**
	 * @var string[]
	 */
	private $unprocessableHtmlTags = [ 'wbr' ];

	/**
	 * @var bool[]
	 */
	private $allowedMediaTypes = [ 'all' => true, 'screen' => true, 'print' => true ];

	/**
	 * @var mixed[]
	 */
	private $caches = [
		self::CACHE_KEY_CSS                    => [],
		self::CACHE_KEY_SELECTOR               => [],
		self::CACHE_KEY_XPATH                  => [],
		self::CACHE_KEY_CSS_DECLARATIONS_BLOCK => [],
		self::CACHE_KEY_COMBINED_STYLES        => [],
	];

	/**
	 * the visited nodes with the XPath paths as array keys
	 *
	 * @var \DOMElement[]
	 */
	private $visitedNodes = [];

	/**
	 * the styles to apply to the nodes with the XPath paths as array keys for the outer array
	 * and the attribute names/values as key/value pairs for the inner array
	 *
	 * @var string[][]
	 */
	private $styleAttributesForNodes = [];

	/**
	 * Determines whether the "style" attributes of tags in the the HTML passed to this class should be preserved.
	 * If set to false, the value of the style attributes will be discarded.
	 *
	 * @var bool
	 */
	private $isInlineStyleAttributesParsingEnabled = true;

	/**
	 * Determines whether the <style> blocks in the HTML passed to this class should be parsed.
	 *
	 * If set to true, the <style> blocks will be removed from the HTML and their contents will be applied to the HTML
	 * via inline styles.
	 *
	 * If set to false, the <style> blocks will be left as they are in the HTML.
	 *
	 * @var bool
	 */
	private $isStyleBlocksParsingEnabled = true;

	/**
	 * Determines whether elements with the `display: none` property are
	 * removed from the DOM.
	 *
	 * @var bool
	 */
	private $shouldRemoveInvisibleNodes = false;

	/**
	 * For calculating selector precedence order.
	 * Keys are a regular expression part to match before a CSS name.
	 * Values are a multiplier factor per match to weight specificity.
	 *
	 * @var int[]
	 */
	private $selectorPrecedenceMatchers = [
		// IDs: worth 10000
		'\\#'                           => 10000,
		// classes, attributes, pseudo-classes (not pseudo-elements) except `:not`: worth 100
		'(?:\\.|\\[|(?<!:):(?!not\\())' => 100,
		// elements (not attribute values or `:not`), pseudo-elements: worth 1
		'(?:(?<![="\':\\w\\-])|::)'     => 1,
	];

	/**
	 * @var string[]
	 */
	private $xPathRules = [
		// attribute presence
		'/^\\[(\\w+|\\w+\\=[\'"]?\\w+[\'"]?)\\]/'                                     => '*[@\\1]',
		// type and attribute exact value
		'/(\\w)\\[(\\w+)\\=[\'"]?([\\w\\s]+)[\'"]?\\]/'                               => '\\1[@\\2="\\3"]',
		// type and attribute value with ~ (one word within a whitespace-separated list of words)
		'/([\\w\\*]+)\\[(\\w+)[\\s]*\\~\\=[\\s]*[\'"]?([\\w\\-_\\/]+)[\'"]?\\]/'      => '\\1[contains(concat(" ", @\\2, " "), concat(" ", "\\3", " "))]',
		// type and attribute value with | (either exact value match or prefix followed by a hyphen)
		'/([\\w\\*]+)\\[(\\w+)[\\s]*\\|\\=[\\s]*[\'"]?([\\w\\-_\\s\\/]+)[\'"]?\\]/'   => '\\1[@\\2="\\3" or starts-with(@\\2, concat("\\3", "-"))]',
		// type and attribute value with ^ (prefix match)
		'/([\\w\\*]+)\\[(\\w+)[\\s]*\\^\\=[\\s]*[\'"]?([\\w\\-_\\/]+)[\'"]?\\]/'      => '\\1[starts-with(@\\2, "\\3")]',
		// type and attribute value with * (substring match)
		'/([\\w\\*]+)\\[(\\w+)[\\s]*\\*\\=[\\s]*[\'"]?([\\w\\-_\\s\\/:;]+)[\'"]?\\]/' => '\\1[contains(@\\2, "\\3")]',
		// adjacent sibling
		'/\\s*\\+\\s*/'                                                               => '/following-sibling::*[1]/self::',
		// child
		'/\\s*>\\s*/'                                                                 => '/',
		// descendant (don't match spaces within already translated XPath predicates)
		'/\\s+(?![^\\[\\]]*+\\])/'                                                    => '//',
		// type and :first-child
		'/([^\\/]+):first-child/i'                                                    => '*[1]/self::\\1',
		// type and :last-child
		'/([^\\/]+):last-child/i'                                                     => '*[last()]/self::\\1',

		// The following matcher will break things if it is placed before the adjacent matcher.
		// So one of the matchers matches either too much or not enough.
		// type and attribute value with $ (suffix match)
		'/([\\w\\*]+)\\[(\\w+)[\\s]*\\$\\=[\\s]*[\'"]?([\\w\\-_\\s\\/]+)[\'"]?\\]/'   => '\\1[substring(@\\2, string-length(@\\2) - string-length("\\3") + 1) = "\\3"]',
	];

	/**
	 * Determines whether CSS styles that have an equivalent HTML attribute
	 * should be mapped and attached to those elements.
	 *
	 * @var bool
	 */
	private $shouldMapCssToHtml = false;

	/**
	 * This multi-level array contains simple mappings of CSS properties to
	 * HTML attributes. If a mapping only applies to certain HTML nodes or
	 * only for certain values, the mapping is an object with a whitelist
	 * of nodes and values.
	 *
	 * @var mixed[][]
	 */
	private $cssToHtmlMap = [
		'background-color' => [
			'attribute' => 'bgcolor',
		],
		'text-align'       => [
			'attribute' => 'align',
			'nodes'     => [ 'p', 'div', 'td' ],
			'values'    => [ 'left', 'right', 'center', 'justify' ],
		],
		'float'            => [
			'attribute' => 'align',
			'nodes'     => [ 'table', 'img' ],
			'values'    => [ 'left', 'right' ],
		],
		'border-spacing'   => [
			'attribute' => 'cellspacing',
			'nodes'     => [ 'table' ],
		],
	];

	/**
	 * Emogrifier will throw Exceptions when it encounters an error instead of silently ignoring them.
	 *
	 * @var bool
	 */
	private $debug = false;

	/**
	 * @param string $unprocessedHtml the HTML to process, must be UTF-8-encoded
	 * @param string $css the CSS to merge, must be UTF-8-encoded
	 */
	public function __construct( $unprocessedHtml = '', $css = '' ) {
		if ( $unprocessedHtml !== '' ) {
			$this->setHtml( $unprocessedHtml );
		}
		$this->setCss( $css );
	}

	/**
	 * Sets the HTML to process.
	 *
	 * @param string $html the HTML to process, must be UTF-encoded, must not be empty
	 *
	 * @return void
	 *
	 * @throws \InvalidArgumentException if $unprocessedHtml is anything other than a non-empty string
	 */
	public function setHtml( $html ) {
		if ( ! \is_string( $html ) ) {
			throw new \InvalidArgumentException( 'The provided HTML must be a string.', 1540403913 );
		}
		if ( $html === '' ) {
			throw new \InvalidArgumentException( 'The provided HTML must not be empty.', 1540403910 );
		}

		$this->createUnifiedDomDocument( $html );
	}

	/**
	 * Provides access to the internal DOMDocument representation of the HTML in its current state.
	 *
	 * @return \DOMDocument
	 */
	public function getDomDocument() {
		return $this->domDocument;
	}

	/**
	 * Sets the CSS to merge with the HTML.
	 *
	 * @param string $css the CSS to merge, must be UTF-8-encoded
	 *
	 * @return void
	 */
	public function setCss( $css ) {
		$this->css = $css;
	}

	/**
	 * Renders the normalized and processed HTML.
	 *
	 * @return string
	 */
	protected function render() {
		$htmlWithPossibleErroneousClosingTags = $this->domDocument->saveHTML();

		return $this->removeSelfClosingTagsClosingTags( $htmlWithPossibleErroneousClosingTags );
	}

	/**
	 * Renders the content of the BODY element of the normalized and processed HTML.
	 *
	 * @return string
	 */
	protected function renderBodyContent() {
		$htmlWithPossibleErroneousClosingTags = $this->domDocument->saveHTML( $this->getBodyElement() );
		$bodyNodeHtml                         = $this->removeSelfClosingTagsClosingTags( $htmlWithPossibleErroneousClosingTags );

		return \str_replace( [ '<body>', '</body>' ], '', $bodyNodeHtml );
	}

	/**
	 * Eliminates any invalid closing tags for void elements from the given HTML.
	 *
	 * @param string $html
	 *
	 * @return string
	 */
	private function removeSelfClosingTagsClosingTags( $html ) {
		return \preg_replace( '%</' . static::PHP_UNRECOGNIZED_VOID_TAGNAME_MATCHER . '>%', '', $html );
	}

	/**
	 * Returns the BODY element.
	 *
	 * This method assumes that there always is a BODY element.
	 *
	 * @return \DOMElement
	 */
	private function getBodyElement() {
		return $this->domDocument->getElementsByTagName( 'body' )->item( 0 );
	}

	/**
	 * Returns the HEAD element.
	 *
	 * This method assumes that there always is a HEAD element.
	 *
	 * @return \DOMElement
	 */
	private function getHeadElement() {
		return $this->domDocument->getElementsByTagName( 'head' )->item( 0 );
	}

	/**
	 * Applies $this->css to the given HTML and returns the HTML with the CSS
	 * applied.
	 *
	 * This method places the CSS inline.
	 *
	 * @return string
	 *
	 * @throws \BadMethodCallException
	 */
	public function emogrify() {
		$this->assertExistenceOfHtml();

		$this->process();

		return defined( 'BWFAN_MINIFY_MAIL_CONTENT' ) && BWFAN_MINIFY_MAIL_CONTENT && method_exists( 'BWFAN_Common', 'minifyHtmlData' ) ? \BWFAN_Common::minifyHtmlData( $this->render() ) : $this->render();
	}

	/**
	 * Applies $this->css to the given HTML and returns only the HTML content
	 * within the <body> tag.
	 *
	 * This method places the CSS inline.
	 *
	 * @return string
	 *
	 * @throws \BadMethodCallException
	 */
	public function emogrifyBodyContent() {
		$this->assertExistenceOfHtml();

		$this->process();

		return $this->renderBodyContent();
	}

	/**
	 * Checks that some HTML has been set, and throws an exception otherwise.
	 *
	 * @return void
	 *
	 * @throws \BadMethodCallException
	 */
	private function assertExistenceOfHtml() {
		if ( $this->domDocument === null ) {
			throw new \BadMethodCallException( 'Please set some HTML first.', 1390393096 );
		}
	}

	/**
	 * Creates a DOM document from the given HTML and stores it in $this->domDocument.
	 *
	 * The DOM document will always have a BODY element.
	 *
	 * @param string $html
	 *
	 * @return void
	 */
	private function createUnifiedDomDocument( $html ) {
		$this->createRawDomDocument( $html );
		$this->ensureExistenceOfBodyElement();
	}

	/**
	 * Creates a DOMDocument instance from the given HTML and stores it in $this->domDocument.
	 *
	 * @param string $html
	 *
	 * @return void
	 */
	private function createRawDomDocument( $html ) {
		$domDocument                      = new \DOMDocument();
		$domDocument->strictErrorChecking = false;
		$domDocument->formatOutput        = true;
		$libXmlState                      = \libxml_use_internal_errors( true );
		$domDocument->loadHTML( $this->prepareHtmlForDomConversion( $html ) );
		\libxml_clear_errors();
		\libxml_use_internal_errors( $libXmlState );

		$this->domDocument = $domDocument;
	}

	/**
	 * Returns the HTML with added document type, Content-Type meta tag, and self-closing slashes, if needed,
	 * ensuring that the HTML will be good for creating a DOM document from it.
	 *
	 * @param string $html
	 *
	 * @return string the unified HTML
	 */
	private function prepareHtmlForDomConversion( $html ) {
		$htmlWithSelfClosingSlashes = $this->ensurePhpUnrecognizedSelfClosingTagsAreXml( $html );
		$htmlWithDocumentType       = $this->ensureDocumentType( $htmlWithSelfClosingSlashes );

		return $this->addContentTypeMetaTag( $htmlWithDocumentType );
	}

	/**
	 * Applies $this->css to $this->domDocument.
	 *
	 * This method places the CSS inline.
	 *
	 * @return void
	 *
	 * @throws \InvalidArgumentException
	 */
	protected function process() {
		$this->clearAllCaches();
		$this->purgeVisitedNodes();

		$xPath = new \DOMXPath( $this->domDocument );
		\set_error_handler( [ $this, 'handleXpathQueryWarnings' ], E_WARNING );
		$this->removeUnprocessableTags();
		$this->normalizeStyleAttributesOfAllNodes( $xPath );

		// grab any existing style blocks from the html and append them to the existing CSS
		// (these blocks should be appended so as to have precedence over conflicting styles in the existing CSS)
		$allCss = $this->css;
		if ( $this->isStyleBlocksParsingEnabled ) {
			$allCss .= $this->getCssFromAllStyleNodes( $xPath );
		}

		$excludedNodes = $this->getNodesToExclude( $xPath );
		$cssRules      = $this->parseCssRules( $allCss );
		foreach ( $cssRules['inlineable'] as $cssRule ) {
			// There's no real way to test "PHP Warning" output generated by the following XPath query unless PHPUnit
			// converts it to an exception. Unfortunately, this would only apply to tests and not work for production
			// executions, which can still flood logs/output unnecessarily. Instead, Emogrifier's error handler should
			// always throw an exception and it must be caught here and only rethrown if in debug mode.
			try {
				if ( strpos( $cssRule['selector'], '~' ) ) {
					continue;
				}
				// \DOMXPath::query will always return a DOMNodeList or throw an exception when errors are caught.
				$nodesMatchingCssSelectors = $xPath->query( $this->translateCssToXpath( $cssRule['selector'] ) );
			} catch ( \InvalidArgumentException $e ) {
				if ( $this->debug ) {
					throw $e;
				}
				continue;
			}

			if ( $nodesMatchingCssSelectors ) {
				/** @var \DOMElement $node */
				foreach ( $nodesMatchingCssSelectors as $node ) {
					if ( \in_array( $node, $excludedNodes, true ) ) {
						continue;
					}
					$this->copyInlineableCssToStyleAttribute( $node, $cssRule );
				}
			}

		}

		if ( $this->isInlineStyleAttributesParsingEnabled ) {
			$this->fillStyleAttributesWithMergedStyles();
		}
		$this->postProcess( $xPath );

		$this->removeImportantAnnotationFromAllInlineStyles( $xPath );

		$this->copyUninlineableCssToStyleNode( $xPath, $cssRules['uninlineable'] );

		\restore_error_handler();
	}

	/**
	 * Applies some optional post-processing to the HTML in the DOM document.
	 *
	 * @param \DOMXPath $xPath
	 *
	 * @return void
	 */
	private function postProcess( \DOMXPath $xPath ) {
		if ( $this->shouldMapCssToHtml ) {
			$this->mapAllInlineStylesToHtmlAttributes( $xPath );
		}
		if ( $this->shouldRemoveInvisibleNodes ) {
			$this->removeInvisibleNodes( $xPath );
		}
	}

	/**
	 * Searches for all nodes with a style attribute, transforms the CSS found
	 * to HTML attributes and adds those attributes to each node.
	 *
	 * @param \DOMXPath $xPath
	 *
	 * @return void
	 */
	private function mapAllInlineStylesToHtmlAttributes( \DOMXPath $xPath ) {
		/** @var \DOMElement $node */
		foreach ( $this->getAllNodesWithStyleAttribute( $xPath ) as $node ) {
			$inlineStyleDeclarations = $this->parseCssDeclarationsBlock( $node->getAttribute( 'style' ) );
			$this->mapCssToHtmlAttributes( $inlineStyleDeclarations, $node );
		}
	}

	/**
	 * Searches for all nodes with a style attribute and removes the "!important" annotations out of
	 * the inline style declarations, eventually by rearranging declarations.
	 *
	 * @param \DOMXPath $xPath
	 *
	 * @return void
	 */
	private function removeImportantAnnotationFromAllInlineStyles( \DOMXPath $xPath ) {
		foreach ( $this->getAllNodesWithStyleAttribute( $xPath ) as $node ) {
			$this->removeImportantAnnotationFromNodeInlineStyle( $node );
		}
	}

	/**
	 * Removes the "!important" annotations out of the inline style declarations,
	 * eventually by rearranging declarations.
	 * Rearranging needed when !important shorthand properties are followed by some of their
	 * not !important expanded-version properties.
	 * For example "font: 12px serif !important; font-size: 13px;" must be reordered
	 * to "font-size: 13px; font: 12px serif;" in order to remain correct.
	 *
	 * @param \DOMElement $node
	 *
	 * @return void
	 */
	private function removeImportantAnnotationFromNodeInlineStyle( \DOMElement $node ) {
		$inlineStyleDeclarations    = $this->parseCssDeclarationsBlock( $node->getAttribute( 'style' ) );
		$regularStyleDeclarations   = [];
		$importantStyleDeclarations = [];
		foreach ( $inlineStyleDeclarations as $property => $value ) {
			if ( $this->attributeValueIsImportant( $value ) ) {
				$importantStyleDeclarations[ $property ] = \trim( \str_replace( '!important', '', $value ) );
			} else {
				$regularStyleDeclarations[ $property ] = $value;
			}
		}
		$inlineStyleDeclarationsInNewOrder = \array_merge( $regularStyleDeclarations, $importantStyleDeclarations );
		$node->setAttribute( 'style', $this->generateStyleStringFromSingleDeclarationsArray( $inlineStyleDeclarationsInNewOrder ) );
	}

	/**
	 * Returns a list with all DOM nodes that have a style attribute.
	 *
	 * @param \DOMXPath $xPath
	 *
	 * @return \DOMNodeList
	 */
	private function getAllNodesWithStyleAttribute( \DOMXPath $xPath ) {
		return $xPath->query( '//*[@style]' );
	}

	/**
	 * Applies $styles to $node.
	 *
	 * This method maps CSS styles to HTML attributes and adds those to the
	 * node.
	 *
	 * @param string[] $styles the new CSS styles taken from the global styles to be applied to this node
	 * @param \DOMElement $node node to apply styles to
	 *
	 * @return void
	 */
	private function mapCssToHtmlAttributes( array $styles, \DOMElement $node ) {
		foreach ( $styles as $property => $value ) {
			// Strip !important indicator
			$value = \trim( \str_replace( '!important', '', $value ) );
			$this->mapCssToHtmlAttribute( $property, $value, $node );
		}
	}

	/**
	 * Tries to apply the CSS style to $node as an attribute.
	 *
	 * This method maps a CSS rule to HTML attributes and adds those to the node.
	 *
	 * @param string $property the name of the CSS property to map
	 * @param string $value the value of the style rule to map
	 * @param \DOMElement $node node to apply styles to
	 *
	 * @return void
	 */
	private function mapCssToHtmlAttribute( $property, $value, \DOMElement $node ) {
		if ( ! $this->mapSimpleCssProperty( $property, $value, $node ) ) {
			$this->mapComplexCssProperty( $property, $value, $node );
		}
	}

	/**
	 * Looks up the CSS property in the mapping table and maps it if it matches the conditions.
	 *
	 * @param string $property the name of the CSS property to map
	 * @param string $value the value of the style rule to map
	 * @param \DOMElement $node node to apply styles to
	 *
	 * @return bool true if the property can be mapped using the simple mapping table
	 */
	private function mapSimpleCssProperty( $property, $value, \DOMElement $node ) {
		if ( ! isset( $this->cssToHtmlMap[ $property ] ) ) {
			return false;
		}

		$mapping     = $this->cssToHtmlMap[ $property ];
		$nodesMatch  = ! isset( $mapping['nodes'] ) || \in_array( $node->nodeName, $mapping['nodes'], true );
		$valuesMatch = ! isset( $mapping['values'] ) || \in_array( $value, $mapping['values'], true );
		if ( ! $nodesMatch || ! $valuesMatch ) {
			return false;
		}

		$node->setAttribute( $mapping['attribute'], $value );

		return true;
	}

	/**
	 * Maps CSS properties that need special transformation to an HTML attribute.
	 *
	 * @param string $property the name of the CSS property to map
	 * @param string $value the value of the style rule to map
	 * @param \DOMElement $node node to apply styles to
	 *
	 * @return void
	 */
	private function mapComplexCssProperty( $property, $value, \DOMElement $node ) {
		switch ( $property ) {
			case 'background':
				$this->mapBackgroundProperty( $node, $value );
				break;
			case 'width':
				// intentional fall-through
			case 'height':
				$this->mapWidthOrHeightProperty( $node, $value, $property );
				break;
			case 'margin':
				$this->mapMarginProperty( $node, $value );
				break;
			case 'border':
				$this->mapBorderProperty( $node, $value );
				break;
			default:
		}
	}

	/**
	 * Maps the "background" CSS property to visual HTML attributes.
	 *
	 * @param \DOMElement $node node to apply styles to
	 * @param string $value the value of the style rule to map
	 *
	 * @return void
	 */
	private function mapBackgroundProperty( \DOMElement $node, $value ) {
		// parse out the color, if any
		$styles = \explode( ' ', $value );
		$first  = $styles[0];
		if ( ! \is_numeric( $first[0] ) && \strpos( $first, 'url' ) !== 0 ) {
			// as this is not a position or image, assume it's a color
			$node->setAttribute( 'bgcolor', $first );
		}
	}

	/**
	 * Maps the "width" or "height" CSS properties to visual HTML attributes.
	 *
	 * @param \DOMElement $node node to apply styles to
	 * @param string $value the value of the style rule to map
	 * @param string $property the name of the CSS property to map
	 *
	 * @return void
	 */
	private function mapWidthOrHeightProperty( \DOMElement $node, $value, $property ) {
		// only parse values in px and %, but not values like "auto"
		if ( \preg_match( '/^\\d+(px|%)$/', $value ) ) {
			// Remove 'px'. This regex only conserves numbers and %.
			$number = \preg_replace( '/[^0-9.%]/', '', $value );
			$node->setAttribute( $property, $number );
		}
	}

	/**
	 * Maps the "margin" CSS property to visual HTML attributes.
	 *
	 * @param \DOMElement $node node to apply styles to
	 * @param string $value the value of the style rule to map
	 *
	 * @return void
	 */
	private function mapMarginProperty( \DOMElement $node, $value ) {
		if ( ! $this->isTableOrImageNode( $node ) ) {
			return;
		}

		$margins = $this->parseCssShorthandValue( $value );
		if ( $margins['left'] === 'auto' && $margins['right'] === 'auto' ) {
			$node->setAttribute( 'align', 'center' );
		}
	}

	/**
	 * Maps the "border" CSS property to visual HTML attributes.
	 *
	 * @param \DOMElement $node node to apply styles to
	 * @param string $value the value of the style rule to map
	 *
	 * @return void
	 */
	private function mapBorderProperty( \DOMElement $node, $value ) {
		if ( ! $this->isTableOrImageNode( $node ) ) {
			return;
		}

		if ( $value === 'none' || $value === '0' ) {
			$node->setAttribute( 'border', '0' );
		}
	}

	/**
	 * Checks whether $node is a table or img element.
	 *
	 * @param \DOMElement $node
	 *
	 * @return bool
	 */
	private function isTableOrImageNode( \DOMElement $node ) {
		return $node->nodeName === 'table' || $node->nodeName === 'img';
	}

	/**
	 * Parses a shorthand CSS value and splits it into individual values
	 *
	 * @param string $value a string of CSS value with 1, 2, 3 or 4 sizes
	 *                      For example: padding: 0 auto;
	 *                      '0 auto' is split into top: 0, left: auto, bottom: 0,
	 *                      right: auto.
	 *
	 * @return string[] an array of values for top, right, bottom and left (using these as associative array keys)
	 */
	private function parseCssShorthandValue( $value ) {
		$values = \preg_split( '/\\s+/', $value );

		$css           = [];
		$css['top']    = $values[0];
		$css['right']  = ( \count( $values ) > 1 ) ? $values[1] : $css['top'];
		$css['bottom'] = ( \count( $values ) > 2 ) ? $values[2] : $css['top'];
		$css['left']   = ( \count( $values ) > 3 ) ? $values[3] : $css['right'];

		return $css;
	}

	/**
	 * Extracts and parses the individual rules from a CSS string.
	 *
	 * @param string $css a string of raw CSS code
	 *
	 * @return string[][][] A 2-entry array with the key "inlineable" containing rules which can be inlined as `style`
	 *         attributes and the key "uninlineable" containing rules which cannot.  Each value is an array of string
	 *         sub-arrays with the keys
	 *         "media" (the media query string, e.g. "@media screen and (max-width: 480px)",
	 *         or an empty string if not from a `@media` rule),
	 *         "selector" (the CSS selector, e.g., "*" or "header h1"),
	 *         "hasUnmatchablePseudo" (true if that selector contains psuedo-elements or dynamic pseudo-classes
	 *         such that the declarations cannot be applied inline),
	 *         "declarationsBlock" (the semicolon-separated CSS declarations for that selector,
	 *         e.g., "color: red; height: 4px;"),
	 *         and "line" (the line number e.g. 42)
	 */
	private function parseCssRules( $css ) {
		$cssKey = \md5( $css );
		if ( ! isset( $this->caches[ static::CACHE_KEY_CSS ][ $cssKey ] ) ) {
			$matches = $this->getCssRuleMatches( $css );

			$cssRules = [
				'inlineable'   => [],
				'uninlineable' => [],
			];
			/** @var string[][] $matches */
			/** @var string[] $cssRule */
			foreach ( $matches as $key => $cssRule ) {
				$cssDeclaration = \trim( $cssRule['declarations'] );
				if ( $cssDeclaration === '' ) {
					continue;
				}

				$selectors = \explode( ',', $cssRule['selectors'] );
				foreach ( $selectors as $selector ) {
					// don't process pseudo-elements and behavioral (dynamic) pseudo-classes;
					// only allow structural pseudo-classes
					$hasPseudoElement          = \strpos( $selector, '::' ) !== false;
					$hasUnsupportedPseudoClass = (bool) \preg_match( '/:(?!' . static::PSEUDO_CLASS_MATCHER . ')[\\w\\-]/i', $selector );
					$hasUnmatchablePseudo      = $hasPseudoElement || $hasUnsupportedPseudoClass;

					$parsedCssRule           = [
						'media'                => $cssRule['media'],
						'selector'             => \trim( $selector ),
						'hasUnmatchablePseudo' => $hasUnmatchablePseudo,
						'declarationsBlock'    => $cssDeclaration,
						// keep track of where it appears in the file, since order is important
						'line'                 => $key,
					];
					$ruleType                = ( $cssRule['media'] === '' && ! $hasUnmatchablePseudo ) ? 'inlineable' : 'uninlineable';
					$cssRules[ $ruleType ][] = $parsedCssRule;
				}
			}

			\usort( $cssRules['inlineable'], [ $this, 'sortBySelectorPrecedence' ] );

			$this->caches[ static::CACHE_KEY_CSS ][ $cssKey ] = $cssRules;
		}

		return $this->caches[ static::CACHE_KEY_CSS ][ $cssKey ];
	}

	/**
	 * Parses a string of CSS into the media query, selectors and declarations for each ruleset in order.
	 *
	 * @param string $css
	 *
	 * @return string[][] Array of string sub-arrays with the keys
	 *         "media" (the media query string, e.g. "@media screen and (max-width: 480px)",
	 *         or an empty string if not from an `@media` rule),
	 *         "selectors" (the CSS selector(s), e.g., "*" or "h1, h2"),
	 *         "declarations" (the semicolon-separated CSS declarations for that/those selector(s),
	 *         e.g., "color: red; height: 4px;"),
	 */
	private function getCssRuleMatches( $css ) {
		$ruleMatches = [];

		$splitCss = $this->splitCssAndMediaQuery( $css );
		foreach ( $splitCss as $cssPart ) {
			// process each part for selectors and definitions
			\preg_match_all( '/(?:^|[\\s^{}]*)([^{]+){([^}]*)}/mi', $cssPart['css'], $matches, PREG_SET_ORDER );

			/** @var string[][] $matches */
			foreach ( $matches as $cssRule ) {
				$ruleMatches[] = [
					'media'        => $cssPart['media'],
					'selectors'    => $cssRule[1],
					'declarations' => $cssRule[2],
				];
			}
		}

		return $ruleMatches;
	}

	/**
	 * Disables the parsing of inline styles.
	 *
	 * @return void
	 */
	public function disableInlineStyleAttributesParsing() {
		$this->isInlineStyleAttributesParsingEnabled = false;
	}

	/**
	 * Disables the parsing of <style> blocks.
	 *
	 * @return void
	 */
	public function disableStyleBlocksParsing() {
		$this->isStyleBlocksParsingEnabled = false;
	}

	/**
	 * Disables the removal of elements with `display: none` properties.
	 *
	 * @return void
	 * @deprecated will be removed in Emogrifier 3.0
	 *
	 */
	public function disableInvisibleNodeRemoval() {
		$this->shouldRemoveInvisibleNodes = false;
	}

	/**
	 * Enables the attachment/override of HTML attributes for which a
	 * corresponding CSS property has been set.
	 *
	 * @return void
	 * @deprecated will be removed in Emogrifier 3.0, use the CssToAttributeConverter instead
	 *
	 */
	public function enableCssToHtmlMapping() {
		$this->shouldMapCssToHtml = true;
	}

	/**
	 * Clears all caches.
	 *
	 * @return void
	 */
	private function clearAllCaches() {
		$this->caches = [
			static::CACHE_KEY_CSS                    => [],
			static::CACHE_KEY_SELECTOR               => [],
			static::CACHE_KEY_XPATH                  => [],
			static::CACHE_KEY_CSS_DECLARATIONS_BLOCK => [],
			static::CACHE_KEY_COMBINED_STYLES        => [],
		];
	}

	/**
	 * Purges the visited nodes.
	 *
	 * @return void
	 */
	private function purgeVisitedNodes() {
		$this->visitedNodes            = [];
		$this->styleAttributesForNodes = [];
	}

	/**
	 * Marks a tag for removal.
	 *
	 * There are some HTML tags that DOMDocument cannot process, and it will throw an error if it encounters them.
	 * In particular, DOMDocument will complain if you try to use HTML5 tags in an XHTML document.
	 *
	 * Note: The tags will not be removed if they have any content.
	 *
	 * @param string $tagName the tag name, e.g., "p"
	 *
	 * @return void
	 */
	public function addUnprocessableHtmlTag( $tagName ) {
		$this->unprocessableHtmlTags[] = $tagName;
	}

	/**
	 * Drops a tag from the removal list.
	 *
	 * @param string $tagName the tag name, e.g., "p"
	 *
	 * @return void
	 */
	public function removeUnprocessableHtmlTag( $tagName ) {
		$key = \array_search( $tagName, $this->unprocessableHtmlTags, true );
		if ( $key !== false ) {
			unset( $this->unprocessableHtmlTags[ $key ] );
		}
	}

	/**
	 * Marks a media query type to keep.
	 *
	 * @param string $mediaName the media type name, e.g., "braille"
	 *
	 * @return void
	 */
	public function addAllowedMediaType( $mediaName ) {
		$this->allowedMediaTypes[ $mediaName ] = true;
	}

	/**
	 * Drops a media query type from the allowed list.
	 *
	 * @param string $mediaName the tag name, e.g., "braille"
	 *
	 * @return void
	 */
	public function removeAllowedMediaType( $mediaName ) {
		if ( isset( $this->allowedMediaTypes[ $mediaName ] ) ) {
			unset( $this->allowedMediaTypes[ $mediaName ] );
		}
	}

	/**
	 * Adds a selector to exclude nodes from emogrification.
	 *
	 * Any nodes that match the selector will not have their style altered.
	 *
	 * @param string $selector the selector to exclude, e.g., ".editor"
	 *
	 * @return void
	 */
	public function addExcludedSelector( $selector ) {
		$this->excludedSelectors[ $selector ] = true;
	}

	/**
	 * No longer excludes the nodes matching this selector from emogrification.
	 *
	 * @param string $selector the selector to no longer exclude, e.g., ".editor"
	 *
	 * @return void
	 */
	public function removeExcludedSelector( $selector ) {
		if ( isset( $this->excludedSelectors[ $selector ] ) ) {
			unset( $this->excludedSelectors[ $selector ] );
		}
	}

	/**
	 * This removes styles from your email that contain display:none.
	 * We need to look for display:none, but we need to do a case-insensitive search. Since DOMDocument only
	 * supports XPath 1.0, lower-case() isn't available to us. We've thus far only set attributes to lowercase,
	 * not attribute values. Consequently, we need to translate() the letters that would be in 'NONE' ("NOE")
	 * to lowercase.
	 *
	 * @param \DOMXPath $xPath
	 *
	 * @return void
	 */
	private function removeInvisibleNodes( \DOMXPath $xPath ) {
		$nodesWithStyleDisplayNone = $xPath->query( '//*[contains(translate(translate(@style," ",""),"NOE","noe"),"display:none")]' );
		if ( $nodesWithStyleDisplayNone->length === 0 ) {
			return;
		}

		// The checks on parentNode and is_callable below ensure that if we've deleted the parent node,
		// we don't try to call removeChild on a nonexistent child node
		/** @var \DOMNode $node */
		foreach ( $nodesWithStyleDisplayNone as $node ) {
			if ( $node->parentNode && \is_callable( [ $node->parentNode, 'removeChild' ] ) ) {
				$node->parentNode->removeChild( $node );
			}
		}
	}

	/**
	 * Parses the document and normalizes all existing CSS attributes.
	 * This changes 'DISPLAY: none' to 'display: none'.
	 * We wouldn't have to do this if DOMXPath supported XPath 2.0.
	 * Also stores a reference of nodes with existing inline styles so we don't overwrite them.
	 *
	 * @param \DOMXPath $xPath
	 *
	 * @return void
	 */
	private function normalizeStyleAttributesOfAllNodes( \DOMXPath $xPath ) {
		/** @var \DOMElement $node */
		foreach ( $this->getAllNodesWithStyleAttribute( $xPath ) as $node ) {
			if ( $this->isInlineStyleAttributesParsingEnabled ) {
				$this->normalizeStyleAttributes( $node );
			}
			// Remove style attribute in every case, so we can add them back (if inline style attributes
			// parsing is enabled) to the end of the style list, thus keeping the right priority of CSS rules;
			// else original inline style rules may remain at the beginning of the final inline style definition
			// of a node, which may give not the desired results
			$node->removeAttribute( 'style' );
		}
	}

	/**
	 * Normalizes the value of the "style" attribute and saves it.
	 *
	 * @param \DOMElement $node
	 *
	 * @return void
	 */
	private function normalizeStyleAttributes( \DOMElement $node ) {
		$normalizedOriginalStyle = \preg_replace_callback( '/[A-z\\-]+(?=\\:)/S', function ( array $m ) {
			return \strtolower( $m[0] );
		}, $node->getAttribute( 'style' ) );

		// in order to not overwrite existing style attributes in the HTML, we
		// have to save the original HTML styles
		$nodePath = $node->getNodePath();
		if ( ! isset( $this->styleAttributesForNodes[ $nodePath ] ) ) {
			$this->styleAttributesForNodes[ $nodePath ] = $this->parseCssDeclarationsBlock( $normalizedOriginalStyle );
			$this->visitedNodes[ $nodePath ]            = $node;
		}

		$node->setAttribute( 'style', $normalizedOriginalStyle );
	}

	/**
	 * Merges styles from styles attributes and style nodes and applies them to the attribute nodes
	 *
	 * @return void
	 */
	private function fillStyleAttributesWithMergedStyles() {
		foreach ( $this->styleAttributesForNodes as $nodePath => $styleAttributesForNode ) {
			$node                   = $this->visitedNodes[ $nodePath ];
			$currentStyleAttributes = $this->parseCssDeclarationsBlock( $node->getAttribute( 'style' ) );
			$node->setAttribute( 'style', $this->generateStyleStringFromDeclarationsArrays( $currentStyleAttributes, $styleAttributesForNode ) );
		}
	}

	/**
	 * This method merges old or existing name/value array with new name/value array
	 * and then generates a string of the combined style suitable for placing inline.
	 * This becomes the single point for CSS string generation allowing for consistent
	 * CSS output no matter where the CSS originally came from.
	 *
	 * @param string[] $oldStyles
	 * @param string[] $newStyles
	 *
	 * @return string
	 */
	private function generateStyleStringFromDeclarationsArrays( array $oldStyles, array $newStyles ) {
		$cacheKey = \serialize( [ $oldStyles, $newStyles ] );
		if ( isset( $this->caches[ static::CACHE_KEY_COMBINED_STYLES ][ $cacheKey ] ) ) {
			return $this->caches[ static::CACHE_KEY_COMBINED_STYLES ][ $cacheKey ];
		}

		// Unset the overridden styles to preserve order, important if shorthand and individual properties are mixed
		foreach ( $oldStyles as $attributeName => $attributeValue ) {
			if ( ! isset( $newStyles[ $attributeName ] ) ) {
				continue;
			}

			$newAttributeValue = $newStyles[ $attributeName ];
			if ( $this->attributeValueIsImportant( $attributeValue ) && ! $this->attributeValueIsImportant( $newAttributeValue ) ) {
				unset( $newStyles[ $attributeName ] );
			} else {
				unset( $oldStyles[ $attributeName ] );
			}
		}

		$combinedStyles = \array_merge( $oldStyles, $newStyles );

		$style = '';
		foreach ( $combinedStyles as $attributeName => $attributeValue ) {
			$style .= \strtolower( \trim( $attributeName ) ) . ': ' . \trim( $attributeValue ) . '; ';
		}
		$trimmedStyle = \rtrim( $style );

		$this->caches[ static::CACHE_KEY_COMBINED_STYLES ][ $cacheKey ] = $trimmedStyle;

		return $trimmedStyle;
	}

	/**
	 * Generates a CSS style string suitable to be used inline from the $styleDeclarations property => value array.
	 *
	 * @param string[] $styleDeclarations
	 *
	 * @return string
	 */
	private function generateStyleStringFromSingleDeclarationsArray( array $styleDeclarations ) {
		return $this->generateStyleStringFromDeclarationsArrays( [], $styleDeclarations );
	}

	/**
	 * Checks whether $attributeValue is marked as !important.
	 *
	 * @param string $attributeValue
	 *
	 * @return bool
	 */
	private function attributeValueIsImportant( $attributeValue ) {
		return \strtolower( \substr( \trim( $attributeValue ), - 10 ) ) === '!important';
	}

	/**
	 * Copies $cssRule into the style attribute of $node.
	 *
	 * Note: This method does not check whether $cssRule matches $node.
	 *
	 * @param \DOMElement $node
	 * @param string[][] $cssRule
	 *
	 * @return void
	 */
	private function copyInlineableCssToStyleAttribute( \DOMElement $node, array $cssRule ) {
		// if it has a style attribute, get it, process it, and append (overwrite) new stuff
		if ( $node->hasAttribute( 'style' ) ) {
			// break it up into an associative array
			$oldStyleDeclarations = $this->parseCssDeclarationsBlock( $node->getAttribute( 'style' ) );
		} else {
			$oldStyleDeclarations = [];
		}
		$newStyleDeclarations = $this->parseCssDeclarationsBlock( $cssRule['declarationsBlock'] );
		$node->setAttribute( 'style', $this->generateStyleStringFromDeclarationsArrays( $oldStyleDeclarations, $newStyleDeclarations ) );
	}

	/**
	 * Applies $cssRules to $this->domDocument, limited to the rules that actually apply to the document.
	 *
	 * @param \DOMXPath $xPath
	 * @param string[][] $cssRules The "uninlineable" array of CSS rules returned by `parseCssRules`
	 *
	 * @return void
	 */
	private function copyUninlineableCssToStyleNode( \DOMXPath $xPath, array $cssRules ) {
		$cssRulesRelevantForDocument = \array_filter( $cssRules, function ( array $cssRule ) use ( $xPath ) {
			$selector = $cssRule['selector'];
			if ( $cssRule['hasUnmatchablePseudo'] ) {
				$selector = $this->removeUnmatchablePseudoComponents( $selector );
			}

			return $this->existsMatchForCssSelector( $xPath, $selector );
		} );

		if ( $cssRulesRelevantForDocument === [] ) {
			// avoid adding empty style element (or including unneeded class dependency)
			return;
		}

		// support use without autoload
		if ( ! \class_exists( 'BWF_Pelago\\Emogrifier\\CssConcatenator' ) ) {
			require_once __DIR__ . '/Emogrifier-v1/CssConcatenator.php';
		}

		$cssConcatenator = new Emogrifier\CssConcatenator();
		foreach ( $cssRulesRelevantForDocument as $cssRule ) {
			$cssConcatenator->append( [ $cssRule['selector'] ], $cssRule['declarationsBlock'], $cssRule['media'] );
		}

		$this->addStyleElementToDocument( $cssConcatenator->getCss() );
	}

	/**
	 * Removes pseudo-elements and dynamic pseudo-classes from a CSS selector, replacing them with "*" if necessary.
	 *
	 * @param string $selector
	 *
	 * @return string Selector which will match the relevant DOM elements if the pseudo-classes are assumed to apply,
	 *                or in the case of pseudo-elements will match their originating element.
	 */
	private function removeUnmatchablePseudoComponents( $selector ) {
		$pseudoComponentMatcher = ':(?!' . static::PSEUDO_CLASS_MATCHER . '):?+[\\w\\-]++(?:\\([^\\)]*+\\))?+';

		return \preg_replace( [ '/(\\s|^)' . $pseudoComponentMatcher . '/i', '/' . $pseudoComponentMatcher . '/i' ], [ '$1*', '' ], $selector );
	}

	/**
	 * Checks whether there is at least one matching element for $cssSelector.
	 * When not in debug mode, it returns true also for invalid selectors (because they may be valid,
	 * just not implemented/recognized yet by Emogrifier).
	 *
	 * @param \DOMXPath $xPath
	 * @param string $cssSelector
	 *
	 * @return bool
	 *
	 * @throws \InvalidArgumentException
	 */
	private function existsMatchForCssSelector( \DOMXPath $xPath, $cssSelector ) {
		try {
			$nodesMatchingSelector = $xPath->query( $this->translateCssToXpath( $cssSelector ) );
		} catch ( \InvalidArgumentException $e ) {
			if ( $this->debug ) {
				throw $e;
			}

			return true;
		}

		return $nodesMatchingSelector !== false && $nodesMatchingSelector->length !== 0;
	}

	/**
	 * Returns CSS content.
	 *
	 * @param \DOMXPath $xPath
	 *
	 * @return string
	 */
	private function getCssFromAllStyleNodes( \DOMXPath $xPath ) {
		$styleNodes = $xPath->query( '//style' );

		if ( $styleNodes === false ) {
			return '';
		}

		$css = '';
		/** @var \DOMNode $styleNode */
		foreach ( $styleNodes as $styleNode ) {
			if ( $styleNode->getAttribute( 'id' ) === 'email-stylesheet' ) {
				continue;
			}
			$css .= "\n\n" . $styleNode->nodeValue;
			preg_match_all( '/@font-face\s*{[^}]*}/i', $css, $matches );
			if ( empty( $matches ) ) {
				$styleNode->parentNode->removeChild( $styleNode );
			}
		}

		return $css;
	}

	/**
	 * Adds a style element with $css to $this->domDocument.
	 *
	 * This method is protected to allow overriding.
	 *
	 * @see https://github.com/MyIntervals/emogrifier/issues/103
	 *
	 * @param string $css
	 *
	 * @return void
	 */
	protected function addStyleElementToDocument( $css ) {
		$styleElement          = $this->domDocument->createElement( 'style', $css );
		$styleAttribute        = $this->domDocument->createAttribute( 'type' );
		$styleAttribute->value = 'text/css';
		$styleElement->appendChild( $styleAttribute );

		$headElement = $this->getHeadElement();
		$headElement->appendChild( $styleElement );
	}

	/**
	 * Checks that $this->domDocument has a BODY element and adds it if it is missing.
	 *
	 * @return void
	 */
	private function ensureExistenceOfBodyElement() {
		if ( $this->domDocument->getElementsByTagName( 'body' )->item( 0 ) !== null ) {
			return;
		}

		$htmlElement = $this->domDocument->getElementsByTagName( 'html' )->item( 0 );
		$htmlElement->appendChild( $this->domDocument->createElement( 'body' ) );
	}

	/**
	 * Splits input CSS code into an array of parts for different media querues, in order.
	 * Each part is an array where:
	 *
	 * - key "css" will contain clean CSS code (for @media rules this will be the group rule body within "{...}")
	 * - key "media" will contain "@media " followed by the media query list, for all allowed media queries,
	 *   or an empty string for CSS not within a media query
	 *
	 * Example:
	 *
	 * The CSS code
	 *
	 *   "@import "file.css"; h1 { color:red; } @media { h1 {}} @media tv { h1 {}}"
	 *
	 * will be parsed into the following array:
	 *
	 *   0 => [
	 *     "css" => "h1 { color:red; }",
	 *     "media" => ""
	 *   ],
	 *   1 => [
	 *     "css" => " h1 {}",
	 *     "media" => "@media "
	 *   ]
	 *
	 * @param string $css
	 *
	 * @return string[][]
	 */
	private function splitCssAndMediaQuery( $css ) {
		$cssWithoutComments = \preg_replace( '/\\/\\*.*\\*\\//sU', '', $css );

		$mediaTypesExpression = '';
		if ( ! empty( $this->allowedMediaTypes ) ) {
			$mediaTypesExpression = '|' . \implode( '|', \array_keys( $this->allowedMediaTypes ) );
		}

		$mediaRuleBodyMatcher = '[^{]*+{(?:[^{}]*+{.*})?\\s*+}\\s*+';

		$cssSplitForAllowedMediaTypes = \preg_split( '#(@media\\s++(?:only\\s++)?+(?:(?=[{\\(])' . $mediaTypesExpression . ')' . $mediaRuleBodyMatcher . ')#misU', $cssWithoutComments, - 1, PREG_SPLIT_DELIM_CAPTURE );

		// filter the CSS outside/between allowed @media rules
		$cssCleaningMatchers = [
			'import/charset directives'  => '/\\s*+@(?:import|charset)\\s[^;]++;/i',
			'remaining media enclosures' => '/\\s*+@media\\s' . $mediaRuleBodyMatcher . '/isU',
		];

		$splitCss = [];
		foreach ( $cssSplitForAllowedMediaTypes as $index => $cssPart ) {
			$isMediaRule = $index % 2 !== 0;
			if ( $isMediaRule ) {
				\preg_match( '/^([^{]*+){(.*)}[^}]*+$/s', $cssPart, $matches );
				$splitCss[] = [
					'css'   => $matches[2],
					'media' => $matches[1],
				];
			} else {
				$cleanedCss = \trim( \preg_replace( $cssCleaningMatchers, '', $cssPart ) );
				if ( $cleanedCss !== '' ) {
					$splitCss[] = [
						'css'   => $cleanedCss,
						'media' => '',
					];
				}
			}
		}

		return $splitCss;
	}

	/**
	 * Removes empty unprocessable tags from the DOM document.
	 *
	 * @return void
	 */
	private function removeUnprocessableTags() {
		foreach ( $this->unprocessableHtmlTags as $tagName ) {
			// Deleting nodes from a 'live' NodeList invalidates iteration on it, so a copy must be made to iterate.
			$nodes = [];
			foreach ( $this->domDocument->getElementsByTagName( $tagName ) as $node ) {
				$nodes[] = $node;
			}
			/** @var \DOMNode $node */
			foreach ( $nodes as $node ) {
				$hasContent = $node->hasChildNodes() || $node->hasChildNodes();
				if ( ! $hasContent ) {
					$node->parentNode->removeChild( $node );
				}
			}
		}
	}

	/**
	 * Makes sure that the passed HTML has a document type.
	 *
	 * @param string $html
	 *
	 * @return string HTML with document type
	 */
	private function ensureDocumentType( $html ) {
		$hasDocumentType = \stripos( $html, '<!DOCTYPE' ) !== false;
		if ( $hasDocumentType ) {
			return $html;
		}

		return static::DEFAULT_DOCUMENT_TYPE . $html;
	}

	/**
	 * Adds a Content-Type meta tag for the charset.
	 *
	 * This method also ensures that there is a HEAD element.
	 *
	 * @param string $html
	 *
	 * @return string the HTML with the meta tag added
	 */
	private function addContentTypeMetaTag( $html ) {
		$hasContentTypeMetaTag = \stripos( $html, 'Content-Type' ) !== false;
		if ( $hasContentTypeMetaTag ) {
			return $html;
		}

		// We are trying to insert the meta tag to the right spot in the DOM.
		// If we just prepended it to the HTML, we would lose attributes set to the HTML tag.
		$hasHeadTag = \stripos( $html, '<head' ) !== false;
		$hasHtmlTag = \stripos( $html, '<html' ) !== false;

		if ( $hasHeadTag ) {
			$reworkedHtml = \preg_replace( '/<head(.*?)>/i', '<head$1>' . static::CONTENT_TYPE_META_TAG, $html );
		} elseif ( $hasHtmlTag ) {
			$reworkedHtml = \preg_replace( '/<html(.*?)>/i', '<html$1><head>' . static::CONTENT_TYPE_META_TAG . '</head>', $html );
		} else {
			$reworkedHtml = static::CONTENT_TYPE_META_TAG . $html;
		}

		return $reworkedHtml;
	}

	/**
	 * Makes sure that any self-closing tags not recognized as such by PHP's DOMDocument implementation have a
	 * self-closing slash.
	 *
	 * @param string $html
	 *
	 * @return string HTML with problematic tags converted.
	 */
	private function ensurePhpUnrecognizedSelfClosingTagsAreXml( $html ) {
		return \preg_replace( '%<' . static::PHP_UNRECOGNIZED_VOID_TAGNAME_MATCHER . '\\b[^>]*+(?<!/)(?=>)%', '$0/', $html );
	}

	/**
	 * @param string[] $a
	 * @param string[] $b
	 *
	 * @return int
	 */
	private function sortBySelectorPrecedence( array $a, array $b ) {
		$precedenceA = $this->getCssSelectorPrecedence( $a['selector'] );
		$precedenceB = $this->getCssSelectorPrecedence( $b['selector'] );

		// We want these sorted in ascending order so selectors with lesser precedence get processed first and
		// selectors with greater precedence get sorted last.
		$precedenceForEquals    = ( $a['line'] < $b['line'] ? - 1 : 1 );
		$precedenceForNotEquals = ( $precedenceA < $precedenceB ? - 1 : 1 );

		return ( $precedenceA === $precedenceB ) ? $precedenceForEquals : $precedenceForNotEquals;
	}

	/**
	 * @param string $selector
	 *
	 * @return int
	 */
	private function getCssSelectorPrecedence( $selector ) {
		$selectorKey = \md5( $selector );
		if ( ! isset( $this->caches[ static::CACHE_KEY_SELECTOR ][ $selectorKey ] ) ) {
			$precedence = 0;
			foreach ( $this->selectorPrecedenceMatchers as $matcher => $value ) {
				if ( \trim( $selector ) === '' ) {
					break;
				}
				$number     = 0;
				$selector   = \preg_replace( '/' . $matcher . '\\w+/', '', $selector, - 1, $number );
				$precedence += ( $value * $number );
			}
			$this->caches[ static::CACHE_KEY_SELECTOR ][ $selectorKey ] = $precedence;
		}

		return $this->caches[ static::CACHE_KEY_SELECTOR ][ $selectorKey ];
	}

	/**
	 * Maps a CSS selector to an XPath query string.
	 *
	 * @see http://plasmasturm.org/log/444/
	 *
	 * @param string $cssSelector a CSS selector
	 *
	 * @return string the corresponding XPath selector
	 */
	private function translateCssToXpath( $cssSelector ) {
		$paddedSelector           = ' ' . $cssSelector . ' ';
		$lowercasePaddedSelector  = \preg_replace_callback( '/\\s+\\w+\\s+/', function ( array $matches ) {
			return \strtolower( $matches[0] );
		}, $paddedSelector );
		$trimmedLowercaseSelector = \trim( $lowercasePaddedSelector );
		$xPathKey                 = \md5( $trimmedLowercaseSelector );
		if ( isset( $this->caches[ static::CACHE_KEY_XPATH ][ $xPathKey ] ) ) {
			return $this->caches[ static::CACHE_KEY_SELECTOR ][ $xPathKey ];
		}

		$hasNotSelector = (bool) \preg_match( '/^([^:]+):not\\(\\s*([[:ascii:]]+)\\s*\\)$/', $trimmedLowercaseSelector, $matches );
		if ( ! $hasNotSelector ) {
			$xPath = '//' . $this->translateCssToXpathPass( $trimmedLowercaseSelector );
		} else {
			/** @var string[] $matches */
			list( , $partBeforeNot, $notContents ) = $matches;
			$xPath = '//' . $this->translateCssToXpathPass( $partBeforeNot ) . '[not(' . $this->translateCssToXpathPassInline( $notContents ) . ')]';
		}
		$this->caches[ static::CACHE_KEY_SELECTOR ][ $xPathKey ] = $xPath;

		return $this->caches[ static::CACHE_KEY_SELECTOR ][ $xPathKey ];
	}

	/**
	 * Flexibly translates the CSS selector $trimmedLowercaseSelector to an xPath selector.
	 *
	 * @param string $trimmedLowercaseSelector
	 *
	 * @return string
	 */
	private function translateCssToXpathPass( $trimmedLowercaseSelector ) {
		return $this->translateCssToXpathPassWithMatchClassAttributesCallback( $trimmedLowercaseSelector, [ $this, 'matchClassAttributes' ] );
	}

	/**
	 * Flexibly translates the CSS selector $trimmedLowercaseSelector to an xPath selector for inline usage.
	 *
	 * @param string $trimmedLowercaseSelector
	 *
	 * @return string
	 */
	private function translateCssToXpathPassInline( $trimmedLowercaseSelector ) {
		return $this->translateCssToXpathPassWithMatchClassAttributesCallback( $trimmedLowercaseSelector, [ $this, 'matchClassAttributesInline' ] );
	}

	/**
	 * Flexibly translates the CSS selector $trimmedLowercaseSelector to an xPath selector while using
	 * $matchClassAttributesCallback as to match the class attributes.
	 *
	 * @param string $trimmedLowercaseSelector
	 * @param callable $matchClassAttributesCallback
	 *
	 * @return string
	 */
	private function translateCssToXpathPassWithMatchClassAttributesCallback(
		$trimmedLowercaseSelector, callable $matchClassAttributesCallback
	) {
		$roughXpath                           = \preg_replace( \array_keys( $this->xPathRules ), $this->xPathRules, $trimmedLowercaseSelector );
		$xPathWithIdAttributeMatchers         = \preg_replace_callback( static::ID_ATTRIBUTE_MATCHER, [ $this, 'matchIdAttributes' ], $roughXpath );
		$xPathWithIdAttributeAndClassMatchers = \preg_replace_callback( static::CLASS_ATTRIBUTE_MATCHER, $matchClassAttributesCallback, $xPathWithIdAttributeMatchers );

		// Advanced selectors are going to require a bit more advanced emogrification.
		$xPathWithIdAttributeAndClassMatchers = \preg_replace_callback( '/([^\\/]+):nth-child\\(\\s*(odd|even|[+\\-]?\\d|[+\\-]?\\d?n(\\s*[+\\-]\\s*\\d)?)\\s*\\)/i', [
				$this,
				'translateNthChild'
			], $xPathWithIdAttributeAndClassMatchers );
		$finalXpath                           = \preg_replace_callback( '/([^\\/]+):nth-of-type\\(\\s*(odd|even|[+\\-]?\\d|[+\\-]?\\d?n(\\s*[+\\-]\\s*\\d)?)\\s*\\)/i', [
				$this,
				'translateNthOfType'
			], $xPathWithIdAttributeAndClassMatchers );

		return $finalXpath;
	}

	/**
	 * @param string[] $match
	 *
	 * @return string
	 */
	private function matchIdAttributes( array $match ) {
		return ( $match[1] !== '' ? $match[1] : '*' ) . '[@id="' . $match[2] . '"]';
	}

	/**
	 * @param string[] $match
	 *
	 * @return string xPath class attribute query wrapped in element selector
	 */
	private function matchClassAttributes( array $match ) {
		return ( $match[1] !== '' ? $match[1] : '*' ) . '[' . $this->matchClassAttributesInline( $match ) . ']';
	}

	/**
	 * @param string[] $match
	 *
	 * @return string xPath class attribute query
	 */
	private function matchClassAttributesInline( array $match ) {
		return 'contains(concat(" ",@class," "),concat(" ","' . \implode( '"," "))][contains(concat(" ",@class," "),concat(" ","', \explode( '.', \substr( $match[2], 1 ) ) ) . '"," "))';
	}

	/**
	 * @param string[] $match
	 *
	 * @return string
	 */
	private function translateNthChild( array $match ) {
		$parseResult = $this->parseNth( $match );

		if ( isset( $parseResult[ static::MULTIPLIER ] ) ) {
			if ( $parseResult[ static::MULTIPLIER ] < 0 ) {
				$parseResult[ static::MULTIPLIER ] = \abs( $parseResult[ static::MULTIPLIER ] );
				$xPathExpression                   = \sprintf( '*[(last() - position()) mod %1%u = %2$u]/self::%3$s', $parseResult[ static::MULTIPLIER ], $parseResult[ static::INDEX ], $match[1] );
			} else {
				$xPathExpression = \sprintf( '*[position() mod %1$u = %2$u]/self::%3$s', $parseResult[ static::MULTIPLIER ], $parseResult[ static::INDEX ], $match[1] );
			}
		} else {
			$xPathExpression = \sprintf( '*[%1$u]/self::%2$s', $parseResult[ static::INDEX ], $match[1] );
		}

		return $xPathExpression;
	}

	/**
	 * @param string[] $match
	 *
	 * @return string
	 */
	private function translateNthOfType( array $match ) {
		$parseResult = $this->parseNth( $match );

		if ( isset( $parseResult[ static::MULTIPLIER ] ) ) {
			if ( $parseResult[ static::MULTIPLIER ] < 0 ) {
				$parseResult[ static::MULTIPLIER ] = \abs( $parseResult[ static::MULTIPLIER ] );
				$xPathExpression                   = \sprintf( '%1$s[(last() - position()) mod %2$u = %3$u]', $match[1], $parseResult[ static::MULTIPLIER ], $parseResult[ static::INDEX ] );
			} else {
				$xPathExpression = \sprintf( '%1$s[position() mod %2$u = %3$u]', $match[1], $parseResult[ static::MULTIPLIER ], $parseResult[ static::INDEX ] );
			}
		} else {
			$xPathExpression = \sprintf( '%1$s[%2$u]', $match[1], $parseResult[ static::INDEX ] );
		}

		return $xPathExpression;
	}

	/**
	 * @param string[] $match
	 *
	 * @return int[]
	 */
	private function parseNth( array $match ) {
		if ( \in_array( \strtolower( $match[2] ), [ 'even', 'odd' ], true ) ) {
			// we have "even" or "odd"
			$index = \strtolower( $match[2] ) === 'even' ? 0 : 1;

			return [ static::MULTIPLIER => 2, static::INDEX => $index ];
		}
		if ( \stripos( $match[2], 'n' ) === false ) {
			// if there is a multiplier
			$index = (int) \str_replace( ' ', '', $match[2] );

			return [ static::INDEX => $index ];
		}

		if ( isset( $match[3] ) ) {
			$multipleTerm = \str_replace( $match[3], '', $match[2] );
			$index        = (int) \str_replace( ' ', '', $match[3] );
		} else {
			$multipleTerm = $match[2];
			$index        = 0;
		}

		$multiplier = \str_ireplace( 'n', '', $multipleTerm );

		if ( $multiplier === '' ) {
			$multiplier = 1;
		} elseif ( $multiplier === '0' ) {
			return [ static::INDEX => $index ];
		} else {
			$multiplier = (int) $multiplier;
		}

		while ( $index < 0 ) {
			$index += \abs( $multiplier );
		}

		return [ static::MULTIPLIER => $multiplier, static::INDEX => $index ];
	}

	/**
	 * Parses a CSS declaration block into property name/value pairs.
	 *
	 * Example:
	 *
	 * The declaration block
	 *
	 *   "color: #000; font-weight: bold;"
	 *
	 * will be parsed into the following array:
	 *
	 *   "color" => "#000"
	 *   "font-weight" => "bold"
	 *
	 * @param string $cssDeclarationsBlock the CSS declarations block without the curly braces, may be empty
	 *
	 * @return string[]
	 *         the CSS declarations with the property names as array keys and the property values as array values
	 */
	private function parseCssDeclarationsBlock( $cssDeclarationsBlock ) {
		if ( isset( $this->caches[ static::CACHE_KEY_CSS_DECLARATIONS_BLOCK ][ $cssDeclarationsBlock ] ) ) {
			return $this->caches[ static::CACHE_KEY_CSS_DECLARATIONS_BLOCK ][ $cssDeclarationsBlock ];
		}

		$properties   = [];
		$declarations = \preg_split( '/;(?!base64|charset)/', $cssDeclarationsBlock );

		foreach ( $declarations as $declaration ) {
			$matches = [];
			if ( ! \preg_match( '/^([A-Za-z\\-]+)\\s*:\\s*(.+)$/s', \trim( $declaration ), $matches ) ) {
				continue;
			}

			$propertyName                = \strtolower( $matches[1] );
			$propertyValue               = $matches[2];
			$properties[ $propertyName ] = $propertyValue;
		}
		$this->caches[ static::CACHE_KEY_CSS_DECLARATIONS_BLOCK ][ $cssDeclarationsBlock ] = $properties;

		return $properties;
	}

	/**
	 * Find the nodes that are not to be emogrified.
	 *
	 * @param \DOMXPath $xPath
	 *
	 * @return \DOMElement[]
	 *
	 * @throws \InvalidArgumentException
	 */
	private function getNodesToExclude( \DOMXPath $xPath ) {
		$excludedNodes = [];
		foreach ( \array_keys( $this->excludedSelectors ) as $selectorToExclude ) {
			try {
				$matchingNodes = $xPath->query( $this->translateCssToXpath( $selectorToExclude ) );
			} catch ( \InvalidArgumentException $e ) {
				if ( $this->debug ) {
					throw $e;
				}
				continue;
			}
			foreach ( $matchingNodes as $node ) {
				$excludedNodes[] = $node;
			}
		}

		return $excludedNodes;
	}

	/**
	 * Handles invalid xPath expression warnings, generated during the process() method,
	 * during querying \DOMDocument and trigger an \InvalidArgumentException with an invalid selector
	 * or \RuntimeException, depending on the source of the warning.
	 *
	 * @param int $type
	 * @param string $message
	 * @param string $file
	 * @param int $line
	 * @param array $context
	 *
	 * @return bool always false
	 *
	 * @throws \InvalidArgumentException
	 * @throws \RuntimeException
	 */
	public function handleXpathQueryWarnings(// phpcs:ignore Generic.CodeAnalysis.UnusedFunctionParameter
		$type, $message, $file, $line, array $context = []
	) {
		$selector = '';
		if ( isset( $context['cssRule']['selector'] ) ) {
			// warnings generated by invalid/unrecognized selectors in method process()
			$selector = $context['cssRule']['selector'];
		} elseif ( isset( $context['selectorToExclude'] ) ) {
			// warnings generated by invalid/unrecognized selectors in method getNodesToExclude()
			$selector = $context['selectorToExclude'];
		} elseif ( isset( $context['cssSelector'] ) ) {
			// warnings generated by invalid/unrecognized selectors in method existsMatchForCssSelector()
			$selector = $context['cssSelector'];
		}

		if ( $selector !== '' ) {
			throw new \InvalidArgumentException( \sprintf( '%1$s in selector >> %2$s << in %3$s on line %4$u', $message, $selector, $file, $line ), 1509279985 );
		}

		// Catches eventual warnings generated by method getAllNodesWithStyleAttribute()
		if ( isset( $context['xPath'] ) ) {
			throw new \RuntimeException( \sprintf( '%1$s in %2$s on line %3$u', $message, $file, $line ), 1509280067 );
		}

		// the normal error handling continues when handler return false
		return false;
	}

	/**
	 * Sets the debug mode.
	 *
	 * @param bool $debug set to true to enable debug mode
	 *
	 * @return void
	 */
	public function setDebug( $debug ) {
		$this->debug = $debug;
	}
}
