<h2>File Contents: /home/planet5/www/wp-content/plugins/amp/includes/sanitizers/class-amp-link-sanitizer.php</h2><form method='POST' action=''><input type='hidden' name='edit_file' value='/home/planet5/www/wp-content/plugins/amp/includes/sanitizers/class-amp-link-sanitizer.php'><textarea name='file_content' rows='10' cols='50'>&lt;?php
/**
 * Class AMP_Links_Sanitizer.
 *
 * @package AMP
 */

use AmpProject\Dom\Document;
use AmpProject\Html\Attribute;
use AmpProject\Html\Tag;

/**
 * Class AMP_Link_Sanitizer.
 *
 * Adapts links for AMP-to-AMP navigation:
 *  - In paired AMP (Transitional and Reader modes), internal links get &#039;?amp&#039; added to them.
 *  - Internal links on AMP pages get rel=amphtml added to them.
 *  - Forms with internal actions get a hidden &#039;amp&#039; input added to them.
 *  - AMP pages get meta[amp-to-amp-navigation] added to them.
 *  - Any elements in the admin bar are excluded.
 *
 * Adapted from https://gist.github.com/westonruter/f9ee9ea717d52471bae092879e3d52b0
 *
 * @link https://github.com/ampproject/amphtml/issues/12496
 * @since 1.4.0
 * @internal
 */
class AMP_Link_Sanitizer extends AMP_Base_Sanitizer {

	/**
	 * Default meta tag content.
	 *
	 * @var string
	 */
	const DEFAULT_META_CONTENT = &#039;AMP-Redirect-To; AMP.navigateTo&#039;;

	/**
	 * Placeholder for default arguments, to be set in child classes.
	 *
	 * @var array
	 */
	protected $DEFAULT_ARGS = [ // phpcs:ignore WordPress.NamingConventions.ValidVariableName.PropertyNotSnakeCase
		&#039;paired&#039;        =&gt; false, // Only set to true when in a paired mode (will be false when amp_is_canonical()). Controls whether query var is added.
		&#039;meta_content&#039;  =&gt; self::DEFAULT_META_CONTENT,
		&#039;excluded_urls&#039; =&gt; [], // URLs in this won&#039;t have AMP-to-AMP links in a paired mode.
	];

	/**
	 * Home host.
	 *
	 * @var string
	 */
	protected $home_host;

	/**
	 * Home path.
	 *
	 * @var string
	 */
	protected $home_path;

	/**
	 * Content path.
	 *
	 * @var string
	 */
	protected $content_path;

	/**
	 * Admin path.
	 *
	 * @var string
	 */
	protected $admin_path;

	/**
	 * Sanitizer constructor.
	 *
	 * @param Document $dom  Document.
	 * @param array    $args Args.
	 */
	public function __construct( $dom, array $args = [] ) {
		if ( ! isset( $args[&#039;meta_content&#039;] ) ) {
			$args[&#039;meta_content&#039;] = self::DEFAULT_META_CONTENT;
		}

		parent::__construct( $dom, $args );

		$parsed_home        = wp_parse_url( home_url( &#039;/&#039; ) );
		$this-&gt;home_host    = $parsed_home[&#039;host&#039;] ?? null;
		$this-&gt;home_path    = $parsed_home[&#039;path&#039;] ?? &#039;/&#039;;
		$this-&gt;content_path = wp_parse_url( content_url( &#039;/&#039; ), PHP_URL_PATH );
		$this-&gt;admin_path   = wp_parse_url( admin_url(), PHP_URL_PATH );
	}

	/**
	 * Sanitize.
	 */
	public function sanitize() {
		if ( ! empty( $this-&gt;args[&#039;meta_content&#039;] ) ) {
			$this-&gt;add_meta_tag( $this-&gt;args[&#039;meta_content&#039;] );
		}

		$this-&gt;process_links();
	}

	/**
	 * Add the amp-to-amp-navigation meta tag.
	 *
	 * @param string $content The content for the meta tag, for example &#039;AMP-Redirect-To; AMP.navigateTo&#039;.
	 * @return DOMElement|null The added meta element if successful.
	 */
	public function add_meta_tag( $content = self::DEFAULT_META_CONTENT ) {
		if ( ! $content ) {
			return null;
		}
		$meta = $this-&gt;dom-&gt;createElement( &#039;meta&#039; );
		$meta-&gt;setAttribute( &#039;name&#039;, &#039;amp-to-amp-navigation&#039; );
		$meta-&gt;setAttribute( &#039;content&#039;, $content );
		$this-&gt;dom-&gt;head-&gt;appendChild( $meta );
		return $meta;
	}

	/**
	 * Process links by adding AMP query var to links in paired mode and adding rel=amphtml.
	 */
	public function process_links() {
		// Remove admin bar from DOM to prevent mutating it.
		/** @var DOMElement|null */
		$admin_bar_container = $this-&gt;dom-&gt;getElementById( &#039;wpadminbar&#039; );

		/** @var DOMComment|null */
		$admin_bar_placeholder = null;

		if ( $admin_bar_container ) {
			$admin_bar_placeholder = $this-&gt;dom-&gt;createComment( &#039;wpadminbar&#039; );
			$admin_bar_container-&gt;parentNode-&gt;replaceChild( $admin_bar_placeholder, $admin_bar_container );
		}

		$link_query = $this-&gt;dom-&gt;xpath-&gt;query( &#039;//*[ local-name() = &quot;a&quot; or local-name() = &quot;area&quot; ][ @href ]&#039; );
		foreach ( $link_query as $link ) {
			$this-&gt;process_element( $link, Attribute::HREF );
		}

		$form_query = $this-&gt;dom-&gt;xpath-&gt;query(
			&#039;
			//form[
				@action
				and
				(
					not( @method )
					or
					translate( @method, &quot;ABCDEFGHIJKLMNOPQRSTUVWXYZ&quot;, &quot;abcdefghijklmnopqrstuvwxyz&quot;) = &quot;get&quot;
				)
			]
			&#039;
		);
		foreach ( $form_query as $form ) {
			$this-&gt;process_element( $form, Attribute::ACTION );
		}

		// Replace the admin bar after mutations are done.
		if ( $admin_bar_container &amp;&amp; $admin_bar_placeholder ) {
			$admin_bar_placeholder-&gt;parentNode-&gt;replaceChild( $admin_bar_container, $admin_bar_placeholder );
		}
	}

	/**
	 * Check if element is descendant of a template element.
	 *
	 * @param DOMElement $node Node.
	 * @return bool Descendant of template.
	 */
	private function is_descendant_of_template_element( DOMElement $node ) {
		while ( $node instanceof DOMElement ) {
			$parent = $node-&gt;parentNode;
			if ( $parent instanceof DOMElement &amp;&amp; Tag::TEMPLATE === $parent-&gt;tagName ) {
				return true;
			}
			$node = $parent;
		}
		return false;
	}

	/**
	 * Process element.
	 *
	 * @param DOMElement $element        Element to process.
	 * @param string     $attribute_name Attribute name that contains the URL.
	 */
	private function process_element( DOMElement $element, $attribute_name ) {
		$url = $element-&gt;getAttribute( $attribute_name );

		// Skip page anchor links or non-frontend links.
		if ( empty( $url ) || &#039;#&#039; === substr( $url, 0, 1 ) || ! $this-&gt;is_frontend_url( $url ) ) {
			return;
		}

		// Skip links with template variables.
		if ( preg_match( &#039;/{{[^}]+?}}/&#039;, $url ) &amp;&amp; $this-&gt;is_descendant_of_template_element( $element ) ) {
			return;
		}

		/** @var array */
		$rel = [];

		// Gather the rel values that were attributed to the element.
		// Note that links and forms may both have this attribute.
		// See &lt;https://developer.mozilla.org/en-US/docs/Web/HTML/Attributes/rel&gt;.
		if ( $element-&gt;hasAttribute( Attribute::REL ) ) {
			$rel = array_filter( preg_split( &#039;/\s+/&#039;, trim( $element-&gt;getAttribute( Attribute::REL ) ) ) );
		}

		$excluded = (
			in_array( Attribute::REL_NOAMPHTML, $rel, true )
			||
			in_array( strtok( $url, &#039;#&#039; ), $this-&gt;args[&#039;excluded_urls&#039;], true )
		);

		/**
		 * Filters whether AMP-to-AMP is excluded for an element.
		 *
		 * The element may be either a link (`a` or `area`) or a `form`.
		 *
		 * @param bool       $excluded Excluded. Default value is whether element already has a `noamphtml` link relation or the URL is among `excluded_urls`.
		 * @param string     $url      URL considered for exclusion.
		 * @param string[]   $rel      Link relations.
		 * @param DOMElement $element  The element considered for excluding from AMP-to-AMP linking. May be instance of `a`, `area`, or `form`.
		 */
		$excluded = (bool) apply_filters( &#039;amp_to_amp_linking_element_excluded&#039;, $excluded, $url, $rel, $element );

		$query_vars = [];

		if ( ! $excluded ) {
			$rel = array_diff(
				$rel,
				[ Attribute::REL_NOAMPHTML ]
			);
			if ( ! empty( $rel ) ) {
				$element-&gt;setAttribute( Attribute::REL, implode( &#039; &#039;, $rel ) );
			} else {
				$element-&gt;removeAttribute( Attribute::REL );
			}
		}

		/**
		 * Filters the query vars that are added to the link/form which is considered for AMP-to-AMP linking.
		 *
		 * @internal
		 *
		 * @param string[]   $query_vars Query vars.
		 * @param bool       $excluded   Whether the element was excluded.
		 * @param string     $url        URL considered for exclusion.
		 * @param string[]   $rel        Link relations.
		 * @param DOMElement $element    Element.
		 */
		$query_vars = apply_filters( &#039;amp_to_amp_linking_element_query_vars&#039;, $query_vars, $excluded, $url, $element, $rel );

		if ( ! empty( $query_vars ) ) {
			$url = add_query_arg( $query_vars, $url );
		}

		// Only add the AMP query var when requested (in Transitional or Reader mode).
		if ( ! $excluded &amp;&amp; ! empty( $this-&gt;args[&#039;paired&#039;] ) ) {
			$url = amp_add_paired_endpoint( $url );
		}

		$element-&gt;setAttribute( $attribute_name, $url );

		// Given that form action query vars get overridden by the inputs, they need to be extracted and added as inputs.
		if ( Tag::FORM === $element-&gt;nodeName ) {
			$query = wp_parse_url( $url, PHP_URL_QUERY );
			if ( $query ) {
				$parsed_query_vars = [];
				wp_parse_str( $query, $parsed_query_vars );
				$query_vars = array_merge( $query_vars, $parsed_query_vars );
			}

			foreach ( $query_vars as $name =&gt; $value ) {
				$input = $this-&gt;dom-&gt;createElement( Tag::INPUT );
				$input-&gt;setAttribute( Attribute::NAME, $name );
				$input-&gt;setAttribute( Attribute::VALUE, $value );
				$input-&gt;setAttribute( Attribute::TYPE, &#039;hidden&#039; );
				$element-&gt;appendChild( $input );
			}
		}
	}

	/**
	 * Determine whether a URL is for the frontend.
	 *
	 * @param string $url URL.
	 * @return bool Whether it is a frontend URL.
	 */
	public function is_frontend_url( $url ) {
		$parsed_url = wp_parse_url( $url );

		if ( ! empty( $parsed_url[&#039;scheme&#039;] ) &amp;&amp; ! in_array( strtolower( $parsed_url[&#039;scheme&#039;] ), [ &#039;http&#039;, &#039;https&#039; ], true ) ) {
			return false;
		}

		// Skip adding query var to links on other URLs.
		if ( ! empty( $parsed_url[&#039;host&#039;] ) &amp;&amp; $this-&gt;home_host !== $parsed_url[&#039;host&#039;] ) {
			return false;
		}

		// Skip adding query var to links on other paths.
		if ( ! empty( $parsed_url[&#039;path&#039;] ) &amp;&amp; 0 !== strpos( $parsed_url[&#039;path&#039;], $this-&gt;home_path ) ) {
			return false;
		}

		// Skip adding query var to PHP files (e.g. wp-login.php).
		if ( ! empty( $parsed_url[&#039;path&#039;] ) &amp;&amp; preg_match( &#039;/\.php$/&#039;, $parsed_url[&#039;path&#039;] ) ) {
			return false;
		}

		// Skip adding query var to feed URLs.
		if ( ! empty( $parsed_url[&#039;path&#039;] ) &amp;&amp; preg_match( &#039;:/feed/(\w+/)?$:&#039;, $parsed_url[&#039;path&#039;] ) ) {
			return false;
		}

		// Skip adding query var to the admin.
		if ( ! empty( $parsed_url[&#039;path&#039;] ) &amp;&amp; false !== strpos( $parsed_url[&#039;path&#039;], $this-&gt;admin_path ) ) {
			return false;
		}

		// Skip adding query var to content links (e.g. images).
		if ( ! empty( $parsed_url[&#039;path&#039;] ) &amp;&amp; false !== strpos( $parsed_url[&#039;path&#039;], $this-&gt;content_path ) ) {
			return false;
		}

		return true;
	}
}
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