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<?php
/**
 * HTML API: WP_HTML_Processor class
 *
 * @package WordPress
 * @subpackage HTML-API
 * @since 6.4.0
 */

/**
 * Core class used to safely parse and modify an HTML document.
 *
 * The HTML Processor class properly parses and modifies HTML5 documents.
 *
 * It supports a subset of the HTML5 specification, and when it encounters
 * unsupported markup, it aborts early to avoid unintentionally breaking
 * the document. The HTML Processor should never break an HTML document.
 *
 * While the `WP_HTML_Tag_Processor` is a valuable tool for modifying
 * attributes on individual HTML tags, the HTML Processor is more capable
 * and useful for the following operations:
 *
 *  - Querying based on nested HTML structure.
 *
 * Eventually the HTML Processor will also support:
 *  - Wrapping a tag in surrounding HTML.
 *  - Unwrapping a tag by removing its parent.
 *  - Inserting and removing nodes.
 *  - Reading and changing inner content.
 *  - Navigating up or around HTML structure.
 *
 * ## Usage
 *
 * Use of this class requires three steps:
 *
 *   1. Call a static creator method with your input HTML document.
 *   2. Find the location in the document you are looking for.
 *   3. Request changes to the document at that location.
 *
 * Example:
 *
 *     $processor = WP_HTML_Processor::create_fragment( $html );
 *     if ( $processor->next_tag( array( 'breadcrumbs' => array( 'DIV', 'FIGURE', 'IMG' ) ) ) ) {
 *         $processor->add_class( 'responsive-image' );
 *     }
 *
 * #### Breadcrumbs
 *
 * Breadcrumbs represent the stack of open elements from the root
 * of the document or fragment down to the currently-matched node,
 * if one is currently selected. Call WP_HTML_Processor::get_breadcrumbs()
 * to inspect the breadcrumbs for a matched tag.
 *
 * Breadcrumbs can specify nested HTML structure and are equivalent
 * to a CSS selector comprising tag names separated by the child
 * combinator, such as "DIV > FIGURE > IMG".
 *
 * Since all elements find themselves inside a full HTML document
 * when parsed, the return value from `get_breadcrumbs()` will always
 * contain any implicit outermost elements. For example, when parsing
 * with `create_fragment()` in the `BODY` context (the default), any
 * tag in the given HTML document will contain `array( 'HTML', 'BODY', … )`
 * in its breadcrumbs.
 *
 * Despite containing the implied outermost elements in their breadcrumbs,
 * tags may be found with the shortest-matching breadcrumb query. That is,
 * `array( 'IMG' )` matches all IMG elements and `array( 'P', 'IMG' )`
 * matches all IMG elements directly inside a P element. To ensure that no
 * partial matches erroneously match it's possible to specify in a query
 * the full breadcrumb match all the way down from the root HTML element.
 *
 * Example:
 *
 *     $html = '<figure><img><figcaption>A <em>lovely</em> day outside</figcaption></figure>';
 *     //               ----- Matches here.
 *     $processor->next_tag( array( 'breadcrumbs' => array( 'FIGURE', 'IMG' ) ) );
 *
 *     $html = '<figure><img><figcaption>A <em>lovely</em> day outside</figcaption></figure>';
 *     //                                  ---- Matches here.
 *     $processor->next_tag( array( 'breadcrumbs' => array( 'FIGURE', 'FIGCAPTION', 'EM' ) ) );
 *
 *     $html = '<div><img></div><img>';
 *     //                       ----- Matches here, because IMG must be a direct child of the implicit BODY.
 *     $processor->next_tag( array( 'breadcrumbs' => array( 'BODY', 'IMG' ) ) );
 *
 * ## HTML Support
 *
 * This class implements a small part of the HTML5 specification.
 * It's designed to operate within its support and abort early whenever
 * encountering circumstances it can't properly handle. This is
 * the principle way in which this class remains as simple as possible
 * without cutting corners and breaking compliance.
 *
 * ### Supported elements
 *
 * If any unsupported element appears in the HTML input the HTML Processor
 * will abort early and stop all processing. This draconian measure ensures
 * that the HTML Processor won't break any HTML it doesn't fully understand.
 *
 * The HTML Processor supports all elements other than a specific set:
 *
 *  - Any element inside a TABLE.
 *  - Any element inside foreign content, including SVG and MATH.
 *  - Any element outside the IN BODY insertion mode, e.g. doctype declarations, meta, links.
 *
 * ### Supported markup
 *
 * Some kinds of non-normative HTML involve reconstruction of formatting elements and
 * re-parenting of mis-nested elements. For example, a DIV tag found inside a TABLE
 * may in fact belong _before_ the table in the DOM. If the HTML Processor encounters
 * such a case it will stop processing.
 *
 * The following list illustrates some common examples of unexpected HTML inputs that
 * the HTML Processor properly parses and represents:
 *
 *  - HTML with optional tags omitted, e.g. `<p>one<p>two`.
 *  - HTML with unexpected tag closers, e.g. `<p>one </span> more</p>`.
 *  - Non-void tags with self-closing flag, e.g. `<div/>the DIV is still open.</div>`.
 *  - Heading elements which close open heading elements of another level, e.g. `<h1>Closed by </h2>`.
 *  - Elements containing text that looks like other tags but isn't, e.g. `<title>The <img> is plaintext</title>`.
 *  - SCRIPT and STYLE tags containing text that looks like HTML but isn't, e.g. `<script>document.write('<p>Hi</p>');</script>`.
 *  - SCRIPT content which has been escaped, e.g. `<script><!-- document.write('<script>console.log("hi")</script>') --></script>`.
 *
 * ### Unsupported Features
 *
 * This parser does not report parse errors.
 *
 * Normally, when additional HTML or BODY tags are encountered in a document, if there
 * are any additional attributes on them that aren't found on the previous elements,
 * the existing HTML and BODY elements adopt those missing attribute values. This
 * parser does not add those additional attributes.
 *
 * In certain situations, elements are moved to a different part of the document in
 * a process called "adoption" and "fostering." Because the nodes move to a location
 * in the document that the parser had already processed, this parser does not support
 * these situations and will bail.
 *
 * @since 6.4.0
 *
 * @see WP_HTML_Tag_Processor
 * @see https://html.spec.whatwg.org/
 */
class WP_HTML_Processor extends WP_HTML_Tag_Processor {
	/**
	 * The maximum number of bookmarks allowed to exist at any given time.
	 *
	 * HTML processing requires more bookmarks than basic tag processing,
	 * so this class constant from the Tag Processor is overwritten.
	 *
	 * @since 6.4.0
	 *
	 * @var int
	 */
	const MAX_BOOKMARKS = 100;

	/**
	 * Holds the working state of the parser, including the stack of
	 * open elements and the stack of active formatting elements.
	 *
	 * Initialized in the constructor.
	 *
	 * @since 6.4.0
	 *
	 * @var WP_HTML_Processor_State
	 */
	private $state;

	/**
	 * Used to create unique bookmark names.
	 *
	 * This class sets a bookmark for every tag in the HTML document that it encounters.
	 * The bookmark name is auto-generated and increments, starting with `1`. These are
	 * internal bookmarks and are automatically released when the referring WP_HTML_Token
	 * goes out of scope and is garbage-collected.
	 *
	 * @since 6.4.0
	 *
	 * @see WP_HTML_Processor::$release_internal_bookmark_on_destruct
	 *
	 * @var int
	 */
	private $bookmark_counter = 0;

	/**
	 * Stores an explanation for why something failed, if it did.
	 *
	 * @see self::get_last_error
	 *
	 * @since 6.4.0
	 *
	 * @var string|null
	 */
	private $last_error = null;

	/**
	 * Stores context for why the parser bailed on unsupported HTML, if it did.
	 *
	 * @see self::get_unsupported_exception
	 *
	 * @since 6.7.0
	 *
	 * @var WP_HTML_Unsupported_Exception|null
	 */
	private $unsupported_exception = null;

	/**
	 * Releases a bookmark when PHP garbage-collects its wrapping WP_HTML_Token instance.
	 *
	 * This function is created inside the class constructor so that it can be passed to
	 * the stack of open elements and the stack of active formatting elements without
	 * exposing it as a public method on the class.
	 *
	 * @since 6.4.0
	 *
	 * @var Closure|null
	 */
	private $release_internal_bookmark_on_destruct = null;

	/**
	 * Stores stack events which arise during parsing of the
	 * HTML document, which will then supply the "match" events.
	 *
	 * @since 6.6.0
	 *
	 * @var WP_HTML_Stack_Event[]
	 */
	private $element_queue = array();

	/**
	 * Stores the current breadcrumbs.
	 *
	 * @since 6.7.0
	 *
	 * @var string[]
	 */
	private $breadcrumbs = array();

	/**
	 * Current stack event, if set, representing a matched token.
	 *
	 * Because the parser may internally point to a place further along in a document
	 * than the nodes which have already been processed (some "virtual" nodes may have
	 * appeared while scanning the HTML document), this will point at the "current" node
	 * being processed. It comes from the front of the element queue.
	 *
	 * @since 6.6.0
	 *
	 * @var WP_HTML_Stack_Event|null
	 */
	private $current_element = null;

	/**
	 * Context node if created as a fragment parser.
	 *
	 * @var WP_HTML_Token|null
	 */
	private $context_node = null;

	/*
	 * Public Interface Functions
	 */

	/**
	 * Creates an HTML processor in the fragment parsing mode.
	 *
	 * Use this for cases where you are processing chunks of HTML that
	 * will be found within a bigger HTML document, such as rendered
	 * block output that exists within a post, `the_content` inside a
	 * rendered site layout.
	 *
	 * Fragment parsing occurs within a context, which is an HTML element
	 * that the document will eventually be placed in. It becomes important
	 * when special elements have different rules than others, such as inside
	 * a TEXTAREA or a TITLE tag where things that look like tags are text,
	 * or inside a SCRIPT tag where things that look like HTML syntax are JS.
	 *
	 * The context value should be a representation of the tag into which the
	 * HTML is found. For most cases this will be the body element. The HTML
	 * form is provided because a context element may have attributes that
	 * impact the parse, such as with a SCRIPT tag and its `type` attribute.
	 *
	 * ## Current HTML Support
	 *
	 *  - The only supported context is `<body>`, which is the default value.
	 *  - The only supported document encoding is `UTF-8`, which is the default value.
	 *
	 * @since 6.4.0
	 * @since 6.6.0 Returns `static` instead of `self` so it can create subclass instances.
	 *
	 * @param string $html     Input HTML fragment to process.
	 * @param string $context  Context element for the fragment, must be default of `<body>`.
	 * @param string $encoding Text encoding of the document; must be default of 'UTF-8'.
	 * @return static|null The created processor if successful, otherwise null.
	 */
	public static function create_fragment( $html, $context = '<body>', $encoding = 'UTF-8' ) {
		if ( '<body>' !== $context || 'UTF-8' !== $encoding ) {
			return null;
		}

		$processor                             = new static( $html, self::CONSTRUCTOR_UNLOCK_CODE );
		$processor->state->context_node        = array( 'BODY', array() );
		$processor->state->insertion_mode      = WP_HTML_Processor_State::INSERTION_MODE_IN_BODY;
		$processor->state->encoding            = $encoding;
		$processor->state->encoding_confidence = 'certain';

		// @todo Create "fake" bookmarks for non-existent but implied nodes.
		$processor->bookmarks['root-node']    = new WP_HTML_Span( 0, 0 );
		$processor->bookmarks['context-node'] = new WP_HTML_Span( 0, 0 );

		$root_node = new WP_HTML_Token(
			'root-node',
			'HTML',
			false
		);

		$processor->state->stack_of_open_elements->push( $root_node );

		$context_node = new WP_HTML_Token(
			'context-node',
			$processor->state->context_node[0],
			false
		);

		$processor->context_node = $context_node;
		$processor->breadcrumbs  = array( 'HTML', $context_node->node_name );

		return $processor;
	}

	/**
	 * Creates an HTML processor in the full parsing mode.
	 *
	 * It's likely that a fragment parser is more appropriate, unless sending an
	 * entire HTML document from start to finish. Consider a fragment parser with
	 * a context node of `<body>`.
	 *
	 * Since UTF-8 is the only currently-accepted charset, if working with a
	 * document that isn't UTF-8, it's important to convert the document before
	 * creating the processor: pass in the converted HTML.
	 *
	 * @param string      $html                    Input HTML document to process.
	 * @param string|null $known_definite_encoding Optional. If provided, specifies the charset used
	 *                                             in the input byte stream. Currently must be UTF-8.
	 * @return static|null The created processor if successful, otherwise null.
	 */
	public static function create_full_parser( $html, $known_definite_encoding = 'UTF-8' ) {
		if ( 'UTF-8' !== $known_definite_encoding ) {
			return null;
		}

		$processor                             = new static( $html, self::CONSTRUCTOR_UNLOCK_CODE );
		$processor->state->encoding            = $known_definite_encoding;
		$processor->state->encoding_confidence = 'certain';

		return $processor;
	}

	/**
	 * Constructor.
	 *
	 * Do not use this method. Use the static creator methods instead.
	 *
	 * @access private
	 *
	 * @since 6.4.0
	 *
	 * @see WP_HTML_Processor::create_fragment()
	 *
	 * @param string      $html                                  HTML to process.
	 * @param string|null $use_the_static_create_methods_instead This constructor should not be called manually.
	 */
	public function __construct( $html, $use_the_static_create_methods_instead = null ) {
		parent::__construct( $html );

		if ( self::CONSTRUCTOR_UNLOCK_CODE !== $use_the_static_create_methods_instead ) {
			_doing_it_wrong(
				__METHOD__,
				sprintf(
					/* translators: %s: WP_HTML_Processor::create_fragment(). */
					__( 'Call %s to create an HTML Processor instead of calling the constructor directly.' ),
					'<code>WP_HTML_Processor::create_fragment()</code>'
				),
				'6.4.0'
			);
		}

		$this->state = new WP_HTML_Processor_State();

		$this->state->stack_of_open_elements->set_push_handler(
			function ( WP_HTML_Token $token ): void {
				$is_virtual            = ! isset( $this->state->current_token ) || $this->is_tag_closer();
				$same_node             = isset( $this->state->current_token ) && $token->node_name === $this->state->current_token->node_name;
				$provenance            = ( ! $same_node || $is_virtual ) ? 'virtual' : 'real';
				$this->element_queue[] = new WP_HTML_Stack_Event( $token, WP_HTML_Stack_Event::PUSH, $provenance );

				$this->change_parsing_namespace( $token->integration_node_type ? 'html' : $token->namespace );
			}
		);

		$this->state->stack_of_open_elements->set_pop_handler(
			function ( WP_HTML_Token $token ): void {
				$is_virtual            = ! isset( $this->state->current_token ) || ! $this->is_tag_closer();
				$same_node             = isset( $this->state->current_token ) && $token->node_name === $this->state->current_token->node_name;
				$provenance            = ( ! $same_node || $is_virtual ) ? 'virtual' : 'real';
				$this->element_queue[] = new WP_HTML_Stack_Event( $token, WP_HTML_Stack_Event::POP, $provenance );

				$adjusted_current_node = $this->get_adjusted_current_node();

				if ( $adjusted_current_node ) {
					$this->change_parsing_namespace( $adjusted_current_node->integration_node_type ? 'html' : $adjusted_current_node->namespace );
				} else {
					$this->change_parsing_namespace( 'html' );
				}
			}
		);

		/*
		 * Create this wrapper so that it's possible to pass
		 * a private method into WP_HTML_Token classes without
		 * exposing it to any public API.
		 */
		$this->release_internal_bookmark_on_destruct = function ( string $name ): void {
			parent::release_bookmark( $name );
		};
	}

	/**
	 * Stops the parser and terminates its execution when encountering unsupported markup.
	 *
	 * @throws WP_HTML_Unsupported_Exception Halts execution of the parser.
	 *
	 * @since 6.7.0
	 *
	 * @param string $message Explains support is missing in order to parse the current node.
	 */
	private function bail( string $message ) {
		$here  = $this->bookmarks[ $this->state->current_token->bookmark_name ];
		$token = substr( $this->html, $here->start, $here->length );

		$open_elements = array();
		foreach ( $this->state->stack_of_open_elements->stack as $item ) {
			$open_elements[] = $item->node_name;
		}

		$active_formats = array();
		foreach ( $this->state->active_formatting_elements->walk_down() as $item ) {
			$active_formats[] = $item->node_name;
		}

		$this->last_error = self::ERROR_UNSUPPORTED;

		$this->unsupported_exception = new WP_HTML_Unsupported_Exception(
			$message,
			$this->state->current_token->node_name,
			$here->start,
			$token,
			$open_elements,
			$active_formats
		);

		throw $this->unsupported_exception;
	}

	/**
	 * Returns the last error, if any.
	 *
	 * Various situations lead to parsing failure but this class will
	 * return `false` in all those cases. To determine why something
	 * failed it's possible to request the last error. This can be
	 * helpful to know to distinguish whether a given tag couldn't
	 * be found or if content in the document caused the processor
	 * to give up and abort processing.
	 *
	 * Example
	 *
	 *     $processor = WP_HTML_Processor::create_fragment( '<template><strong><button><em><p><em>' );
	 *     false === $processor->next_tag();
	 *     WP_HTML_Processor::ERROR_UNSUPPORTED === $processor->get_last_error();
	 *
	 * @since 6.4.0
	 *
	 * @see self::ERROR_UNSUPPORTED
	 * @see self::ERROR_EXCEEDED_MAX_BOOKMARKS
	 *
	 * @return string|null The last error, if one exists, otherwise null.
	 */
	public function get_last_error(): ?string {
		return $this->last_error;
	}

	/**
	 * Returns context for why the parser aborted due to unsupported HTML, if it did.
	 *
	 * This is meant for debugging purposes, not for production use.
	 *
	 * @since 6.7.0
	 *
	 * @see self::$unsupported_exception
	 *
	 * @return WP_HTML_Unsupported_Exception|null
	 */
	public function get_unsupported_exception() {
		return $this->unsupported_exception;
	}

	/**
	 * Finds the next tag matching the $query.
	 *
	 * @todo Support matching the class name and tag name.
	 *
	 * @since 6.4.0
	 * @since 6.6.0 Visits all tokens, including virtual ones.
	 *
	 * @throws Exception When unable to allocate a bookmark for the next token in the input HTML document.
	 *
	 * @param array|string|null $query {
	 *     Optional. Which tag name to find, having which class, etc. Default is to find any tag.
	 *
	 *     @type string|null $tag_name     Which tag to find, or `null` for "any tag."
	 *     @type string      $tag_closers  'visit' to pause at tag closers, 'skip' or unset to only visit openers.
	 *     @type int|null    $match_offset Find the Nth tag matching all search criteria.
	 *                                     1 for "first" tag, 3 for "third," etc.
	 *                                     Defaults to first tag.
	 *     @type string|null $class_name   Tag must contain this whole class name to match.
	 *     @type string[]    $breadcrumbs  DOM sub-path at which element is found, e.g. `array( 'FIGURE', 'IMG' )`.
	 *                                     May also contain the wildcard `*` which matches a single element, e.g. `array( 'SECTION', '*' )`.
	 * }
	 * @return bool Whether a tag was matched.
	 */
	public function next_tag( $query = null ): bool {
		$visit_closers = isset( $query['tag_closers'] ) && 'visit' === $query['tag_closers'];

		if ( null === $query ) {
			while ( $this->next_token() ) {
				if ( '#tag' !== $this->get_token_type() ) {
					continue;
				}

				if ( ! $this->is_tag_closer() || $visit_closers ) {
					return true;
				}
			}

			return false;
		}

		if ( is_string( $query ) ) {
			$query = array( 'breadcrumbs' => array( $query ) );
		}

		if ( ! is_array( $query ) ) {
			_doing_it_wrong(
				__METHOD__,
				__( 'Please pass a query array to this function.' ),
				'6.4.0'
			);
			return false;
		}

		$needs_class = ( isset( $query['class_name'] ) && is_string( $query['class_name'] ) )
			? $query['class_name']
			: null;

		if ( ! ( array_key_exists( 'breadcrumbs', $query ) && is_array( $query['breadcrumbs'] ) ) ) {
			while ( $this->next_token() ) {
				if ( '#tag' !== $this->get_token_type() ) {
					continue;
				}

				if ( isset( $query['tag_name'] ) && $query['tag_name'] !== $this->get_token_name() ) {
					continue;
				}

				if ( isset( $needs_class ) && ! $this->has_class( $needs_class ) ) {
					continue;
				}

				if ( ! $this->is_tag_closer() || $visit_closers ) {
					return true;
				}
			}

			return false;
		}

		$breadcrumbs  = $query['breadcrumbs'];
		$match_offset = isset( $query['match_offset'] ) ? (int) $query['match_offset'] : 1;

		while ( $match_offset > 0 && $this->next_token() ) {
			if ( '#tag' !== $this->get_token_type() || $this->is_tag_closer() ) {
				continue;
			}

			if ( isset( $needs_class ) && ! $this->has_class( $needs_class ) ) {
				continue;
			}

			if ( $this->matches_breadcrumbs( $breadcrumbs ) && 0 === --$match_offset ) {
				return true;
			}
		}

		return false;
	}

	/**
	 * Ensures internal accounting is maintained for HTML semantic rules while
	 * the underlying Tag Processor class is seeking to a bookmark.
	 *
	 * This doesn't currently have a way to represent non-tags and doesn't process
	 * semantic rules for text nodes. For access to the raw tokens consider using
	 * WP_HTML_Tag_Processor instead.
	 *
	 * @since 6.5.0 Added for internal support; do not use.
	 *
	 * @access private
	 *
	 * @return bool
	 */
	public function next_token(): bool {
		$this->current_element = null;

		if ( isset( $this->last_error ) ) {
			return false;
		}

		/*
		 * Prime the events if there are none.
		 *
		 * @todo In some cases, probably related to the adoption agency
		 *       algorithm, this call to step() doesn't create any new
		 *       events. Calling it again creates them. Figure out why
		 *       this is and if it's inherent or if it's a bug. Looping
		 *       until there are events or until there are no more
		 *       tokens works in the meantime and isn't obviously wrong.
		 */
		if ( empty( $this->element_queue ) && $this->step() ) {
			return $this->next_token();
		}

		// Process the next event on the queue.
		$this->current_element = array_shift( $this->element_queue );
		if ( ! isset( $this->current_element ) ) {
			// There are no tokens left, so close all remaining open elements.
			while ( $this->state->stack_of_open_elements->pop() ) {
				continue;
			}

			return empty( $this->element_queue ) ? false : $this->next_token();
		}

		$is_pop = WP_HTML_Stack_Event::POP === $this->current_element->operation;

		/*
		 * The root node only exists in the fragment parser, and closing it
		 * indicates that the parse is complete. Stop before popping it from
		 * the breadcrumbs.
		 */
		if ( 'root-node' === $this->current_element->token->bookmark_name ) {
			return $this->next_token();
		}

		// Adjust the breadcrumbs for this event.
		if ( $is_pop ) {
			array_pop( $this->breadcrumbs );
		} else {
			$this->breadcrumbs[] = $this->current_element->token->node_name;
		}

		// Avoid sending close events for elements which don't expect a closing.
		if ( $is_pop && ! $this->expects_closer( $this->current_element->token ) ) {
			return $this->next_token();
		}

		return true;
	}

	/**
	 * Indicates if the current tag token is a tag closer.
	 *
	 * Example:
	 *
	 *     $p = WP_HTML_Processor::create_fragment( '<div></div>' );
	 *     $p->next_tag( array( 'tag_name' => 'div', 'tag_closers' => 'visit' ) );
	 *     $p->is_tag_closer() === false;
	 *
	 *     $p->next_tag( array( 'tag_name' => 'div', 'tag_closers' => 'visit' ) );
	 *     $p->is_tag_closer() === true;
	 *
	 * @since 6.6.0 Subclassed for HTML Processor.
	 *
	 * @return bool Whether the current tag is a tag closer.
	 */
	public function is_tag_closer(): bool {
		return $this->is_virtual()
			? ( WP_HTML_Stack_Event::POP === $this->current_element->operation && '#tag' === $this->get_token_type() )
			: parent::is_tag_closer();
	}

	/**
	 * Indicates if the currently-matched token is virtual, created by a stack operation
	 * while processing HTML, rather than a token found in the HTML text itself.
	 *
	 * @since 6.6.0
	 *
	 * @return bool Whether the current token is virtual.
	 */
	private function is_virtual(): bool {
		return (
			isset( $this->current_element->provenance ) &&
			'virtual' === $this->current_element->provenance
		);
	}

	/**
	 * Indicates if the currently-matched tag matches the given breadcrumbs.
	 *
	 * A "*" represents a single tag wildcard, where any tag matches, but not no tags.
	 *
	 * At some point this function _may_ support a `**` syntax for matching any number
	 * of unspecified tags in the breadcrumb stack. This has been intentionally left
	 * out, however, to keep this function simple and to avoid introducing backtracking,
	 * which could open up surprising performance breakdowns.
	 *
	 * Example:
	 *
	 *     $processor = WP_HTML_Processor::create_fragment( '<div><span><figure><img></figure></span></div>' );
	 *     $processor->next_tag( 'img' );
	 *     true  === $processor->matches_breadcrumbs( array( 'figure', 'img' ) );
	 *     true  === $processor->matches_breadcrumbs( array( 'span', 'figure', 'img' ) );
	 *     false === $processor->matches_breadcrumbs( array( 'span', 'img' ) );
	 *     true  === $processor->matches_breadcrumbs( array( 'span', '*', 'img' ) );
	 *
	 * @since 6.4.0
	 *
	 * @param string[] $breadcrumbs DOM sub-path at which element is found, e.g. `array( 'FIGURE', 'IMG' )`.
	 *                              May also contain the wildcard `*` which matches a single element, e.g. `array( 'SECTION', '*' )`.
	 * @return bool Whether the currently-matched tag is found at the given nested structure.
	 */
	public function matches_breadcrumbs( $breadcrumbs ): bool {
		// Everything matches when there are zero constraints.
		if ( 0 === count( $breadcrumbs ) ) {
			return true;
		}

		// Start at the last crumb.
		$crumb = end( $breadcrumbs );

		if ( '*' !== $crumb && $this->get_tag() !== strtoupper( $crumb ) ) {
			return false;
		}

		for ( $i = count( $this->breadcrumbs ) - 1; $i >= 0; $i-- ) {
			$node  = $this->breadcrumbs[ $i ];
			$crumb = strtoupper( current( $breadcrumbs ) );

			if ( '*' !== $crumb && $node !== $crumb ) {
				return false;
			}

			if ( false === prev( $breadcrumbs ) ) {
				return true;
			}
		}

		return false;
	}

	/**
	 * Indicates if the currently-matched node expects a closing
	 * token, or if it will self-close on the next step.
	 *
	 * Most HTML elements expect a closer, such as a P element or
	 * a DIV element. Others, like an IMG element are void and don't
	 * have a closing tag. Special elements, such as SCRIPT and STYLE,
	 * are treated just like void tags. Text nodes and self-closing
	 * foreign content will also act just like a void tag, immediately
	 * closing as soon as the processor advances to the next token.
	 *
	 * @since 6.6.0
	 *
	 * @param WP_HTML_Token|null $node Optional. Node to examine, if provided.
	 *                                 Default is to examine current node.
	 * @return bool|null Whether to expect a closer for the currently-matched node,
	 *                   or `null` if not matched on any token.
	 */
	public function expects_closer( ?WP_HTML_Token $node = null ): ?bool {
		$token_name = $node->node_name ?? $this->get_token_name();

		if ( ! isset( $token_name ) ) {
			return null;
		}

		$token_namespace        = $node->namespace ?? $this->get_namespace();
		$token_has_self_closing = $node->has_self_closing_flag ?? $this->has_self_closing_flag();

		return ! (
			// Comments, text nodes, and other atomic tokens.
			'#' === $token_name[0] ||
			// Doctype declarations.
			'html' === $token_name ||
			// Void elements.
			self::is_void( $token_name ) ||
			// Special atomic elements.
			( 'html' === $token_namespace && in_array( $token_name, array( 'IFRAME', 'NOEMBED', 'NOFRAMES', 'SCRIPT', 'STYLE', 'TEXTAREA', 'TITLE', 'XMP' ), true ) ) ||
			// Self-closing elements in foreign content.
			( 'html' !== $token_namespace && $token_has_self_closing )
		);
	}

	/**
	 * Steps through the HTML document and stop at the next tag, if any.
	 *
	 * @since 6.4.0
	 *
	 * @throws Exception When unable to allocate a bookmark for the next token in the input HTML document.
	 *
	 * @see self::PROCESS_NEXT_NODE
	 * @see self::REPROCESS_CURRENT_NODE
	 *
	 * @param string $node_to_process Whether to parse the next node or reprocess the current node.
	 * @return bool Whether a tag was matched.
	 */
	public function step( $node_to_process = self::PROCESS_NEXT_NODE ): bool {
		// Refuse to proceed if there was a previous error.
		if ( null !== $this->last_error ) {
			return false;
		}

		if ( self::REPROCESS_CURRENT_NODE !== $node_to_process ) {
			/*
			 * Void elements still hop onto the stack of open elements even though
			 * there's no corresponding closing tag. This is important for managing
			 * stack-based operations such as "navigate to parent node" or checking
			 * on an element's breadcrumbs.
			 *
			 * When moving on to the next node, therefore, if the bottom-most element
			 * on the stack is a void element, it must be closed.
			 */
			$top_node = $this->state->stack_of_open_elements->current_node();
			if ( isset( $top_node ) && ! $this->expects_closer( $top_node ) ) {
				$this->state->stack_of_open_elements->pop();
			}
		}

		if ( self::PROCESS_NEXT_NODE === $node_to_process ) {
			parent::next_token();
			if ( WP_HTML_Tag_Processor::STATE_TEXT_NODE === $this->parser_state ) {
				parent::subdivide_text_appropriately();
			}
		}

		// Finish stepping when there are no more tokens in the document.
		if (
			WP_HTML_Tag_Processor::STATE_INCOMPLETE_INPUT === $this->parser_state ||
			WP_HTML_Tag_Processor::STATE_COMPLETE === $this->parser_state
		) {
			return false;
		}

		$adjusted_current_node = $this->get_adjusted_current_node();
		$is_closer             = $this->is_tag_closer();
		$is_start_tag          = WP_HTML_Tag_Processor::STATE_MATCHED_TAG === $this->parser_state && ! $is_closer;
		$token_name            = $this->get_token_name();

		if ( self::REPROCESS_CURRENT_NODE !== $node_to_process ) {
			$this->state->current_token = new WP_HTML_Token(
				$this->bookmark_token(),
				$token_name,
				$this->has_self_closing_flag(),
				$this->release_internal_bookmark_on_destruct
			);
		}

		$parse_in_current_insertion_mode = (
			0 === $this->state->stack_of_open_elements->count() ||
			'html' === $adjusted_current_node->namespace ||
			(
				'math' === $adjusted_current_node->integration_node_type &&
				(
					( $is_start_tag && ! in_array( $token_name, array( 'MGLYPH', 'MALIGNMARK' ), true ) ) ||
					'#text' === $token_name
				)
			) ||
			(
				'math' === $adjusted_current_node->namespace &&
				'ANNOTATION-XML' === $adjusted_current_node->node_name &&
				$is_start_tag && 'SVG' === $token_name
			) ||
			(
				'html' === $adjusted_current_node->integration_node_type &&
				( $is_start_tag || '#text' === $token_name )
			)
		);

		try {
			if ( ! $parse_in_current_insertion_mode ) {
				return $this->step_in_foreign_content();
			}

			switch ( $this->state->insertion_mode ) {
				case WP_HTML_Processor_State::INSERTION_MODE_INITIAL:
					return $this->step_initial();

				case WP_HTML_Processor_State::INSERTION_MODE_BEFORE_HTML:
					return $this->step_before_html();

				case WP_HTML_Processor_State::INSERTION_MODE_BEFORE_HEAD:
					return $this->step_before_head();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_HEAD:
					return $this->step_in_head();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_HEAD_NOSCRIPT:
					return $this->step_in_head_noscript();

				case WP_HTML_Processor_State::INSERTION_MODE_AFTER_HEAD:
					return $this->step_after_head();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_BODY:
					return $this->step_in_body();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE:
					return $this->step_in_table();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE_TEXT:
					return $this->step_in_table_text();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_CAPTION:
					return $this->step_in_caption();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_COLUMN_GROUP:
					return $this->step_in_column_group();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE_BODY:
					return $this->step_in_table_body();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_ROW:
					return $this->step_in_row();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_CELL:
					return $this->step_in_cell();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_SELECT:
					return $this->step_in_select();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_SELECT_IN_TABLE:
					return $this->step_in_select_in_table();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_TEMPLATE:
					return $this->step_in_template();

				case WP_HTML_Processor_State::INSERTION_MODE_AFTER_BODY:
					return $this->step_after_body();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_FRAMESET:
					return $this->step_in_frameset();

				case WP_HTML_Processor_State::INSERTION_MODE_AFTER_FRAMESET:
					return $this->step_after_frameset();

				case WP_HTML_Processor_State::INSERTION_MODE_AFTER_AFTER_BODY:
					return $this->step_after_after_body();

				case WP_HTML_Processor_State::INSERTION_MODE_AFTER_AFTER_FRAMESET:
					return $this->step_after_after_frameset();

				// This should be unreachable but PHP doesn't have total type checking on switch.
				default:
					$this->bail( "Unaware of the requested parsing mode: '{$this->state->insertion_mode}'." );
			}
		} catch ( WP_HTML_Unsupported_Exception $e ) {
			/*
			 * Exceptions are used in this class to escape deep call stacks that
			 * otherwise might involve messier calling and return conventions.
			 */
			return false;
		}
	}

	/**
	 * Computes the HTML breadcrumbs for the currently-matched node, if matched.
	 *
	 * Breadcrumbs start at the outermost parent and descend toward the matched element.
	 * They always include the entire path from the root HTML node to the matched element.
	 *
	 * @todo It could be more efficient to expose a generator-based version of this function
	 *       to avoid creating the array copy on tag iteration. If this is done, it would likely
	 *       be more useful to walk up the stack when yielding instead of starting at the top.
	 *
	 * Example
	 *
	 *     $processor = WP_HTML_Processor::create_fragment( '<p><strong><em><img></em></strong></p>' );
	 *     $processor->next_tag( 'IMG' );
	 *     $processor->get_breadcrumbs() === array( 'HTML', 'BODY', 'P', 'STRONG', 'EM', 'IMG' );
	 *
	 * @since 6.4.0
	 *
	 * @return string[]|null Array of tag names representing path to matched node, if matched, otherwise NULL.
	 */
	public function get_breadcrumbs(): ?array {
		return $this->breadcrumbs;
	}

	/**
	 * Returns the nesting depth of the current location in the document.
	 *
	 * Example:
	 *
	 *     $processor = WP_HTML_Processor::create_fragment( '<div><p></p></div>' );
	 *     // The processor starts in the BODY context, meaning it has depth from the start: HTML > BODY.
	 *     2 === $processor->get_current_depth();
	 *
	 *     // Opening the DIV element increases the depth.
	 *     $processor->next_token();
	 *     3 === $processor->get_current_depth();
	 *
	 *     // Opening the P element increases the depth.
	 *     $processor->next_token();
	 *     4 === $processor->get_current_depth();
	 *
	 *     // The P element is closed during `next_token()` so the depth is decreased to reflect that.
	 *     $processor->next_token();
	 *     3 === $processor->get_current_depth();
	 *
	 * @since 6.6.0
	 *
	 * @return int Nesting-depth of current location in the document.
	 */
	public function get_current_depth(): int {
		return count( $this->breadcrumbs );
	}

	/**
	 * Normalizes an HTML fragment by serializing it.
	 *
	 * This method assumes that the given HTML snippet is found in BODY context.
	 * For normalizing full documents or fragments found in other contexts, create
	 * a new processor using {@see WP_HTML_Processor::create_fragment} or
	 * {@see WP_HTML_Processor::create_full_parser} and call {@see WP_HTML_Processor::serialize}
	 * on the created instances.
	 *
	 * Many aspects of an input HTML fragment may be changed during normalization.
	 *
	 *  - Attribute values will be double-quoted.
	 *  - Duplicate attributes will be removed.
	 *  - Omitted tags will be added.
	 *  - Tag and attribute name casing will be lower-cased,
	 *    except for specific SVG and MathML tags or attributes.
	 *  - Text will be re-encoded, null bytes handled,
	 *    and invalid UTF-8 replaced with U+FFFD.
	 *  - Any incomplete syntax trailing at the end will be omitted,
	 *    for example, an unclosed comment opener will be removed.
	 *
	 * Example:
	 *
	 *     echo WP_HTML_Processor::normalize( '<a href=#anchor v=5 href="/" enabled>One</a another v=5><!--' );
	 *     // <a href="#anchor" v="5" enabled>One</a>
	 *
	 *     echo WP_HTML_Processor::normalize( '<div></p>fun<table><td>cell</div>' );
	 *     // <div><p></p>fun<table><tbody><tr><td>cell</td></tr></tbody></table></div>
	 *
	 *     echo WP_HTML_Processor::normalize( '<![CDATA[invalid comment]]> syntax < <> "oddities"' );
	 *     // <!--[CDATA[invalid comment]]--> syntax &lt; &lt;&gt; &quot;oddities&quot;
	 *
	 * @since 6.7.0
	 *
	 * @param string $html Input HTML to normalize.
	 *
	 * @return string|null Normalized output, or `null` if unable to normalize.
	 */
	public static function normalize( string $html ): ?string {
		return static::create_fragment( $html )->serialize();
	}

	/**
	 * Returns normalized HTML for a fragment by serializing it.
	 *
	 * This differs from {@see WP_HTML_Processor::normalize} in that it starts with
	 * a specific HTML Processor, which _must_ not have already started scanning;
	 * it must be in the initial ready state and will be in the completed state once
	 * serialization is complete.
	 *
	 * Many aspects of an input HTML fragment may be changed during normalization.
	 *
	 *  - Attribute values will be double-quoted.
	 *  - Duplicate attributes will be removed.
	 *  - Omitted tags will be added.
	 *  - Tag and attribute name casing will be lower-cased,
	 *    except for specific SVG and MathML tags or attributes.
	 *  - Text will be re-encoded, null bytes handled,
	 *    and invalid UTF-8 replaced with U+FFFD.
	 *  - Any incomplete syntax trailing at the end will be omitted,
	 *    for example, an unclosed comment opener will be removed.
	 *
	 * Example:
	 *
	 *     $processor = WP_HTML_Processor::create_fragment( '<a href=#anchor v=5 href="/" enabled>One</a another v=5><!--' );
	 *     echo $processor->serialize();
	 *     // <a href="#anchor" v="5" enabled>One</a>
	 *
	 *     $processor = WP_HTML_Processor::create_fragment( '<div></p>fun<table><td>cell</div>' );
	 *     echo $processor->serialize();
	 *     // <div><p></p>fun<table><tbody><tr><td>cell</td></tr></tbody></table></div>
	 *
	 *     $processor = WP_HTML_Processor::create_fragment( '<![CDATA[invalid comment]]> syntax < <> "oddities"' );
	 *     echo $processor->serialize();
	 *     // <!--[CDATA[invalid comment]]--> syntax &lt; &lt;&gt; &quot;oddities&quot;
	 *
	 * @since 6.7.0
	 *
	 * @return string|null Normalized HTML markup represented by processor,
	 *                     or `null` if unable to generate serialization.
	 */
	public function serialize(): ?string {
		if ( WP_HTML_Tag_Processor::STATE_READY !== $this->parser_state ) {
			wp_trigger_error(
				__METHOD__,
				'An HTML Processor which has already started processing cannot serialize its contents. Serialize immediately after creating the instance.',
				E_USER_WARNING
			);
			return null;
		}

		$html = '';
		while ( $this->next_token() ) {
			$html .= $this->serialize_token();
		}

		if ( null !== $this->get_last_error() ) {
			wp_trigger_error(
				__METHOD__,
				"Cannot serialize HTML Processor with parsing error: {$this->get_last_error()}.",
				E_USER_WARNING
			);
			return null;
		}

		return $html;
	}

	/**
	 * Serializes the currently-matched token.
	 *
	 * This method produces a fully-normative HTML string for the currently-matched token,
	 * if able. If not matched at any token or if the token doesn't correspond to any HTML
	 * it will return an empty string (for example, presumptuous end tags are ignored).
	 *
	 * @see static::serialize()
	 *
	 * @since 6.7.0
	 *
	 * @return string Serialization of token, or empty string if no serialization exists.
	 */
	protected function serialize_token(): string {
		$html       = '';
		$token_type = $this->get_token_type();

		switch ( $token_type ) {
			case '#text':
				$html .= htmlspecialchars( $this->get_modifiable_text(), ENT_QUOTES | ENT_SUBSTITUTE | ENT_HTML5, 'UTF-8' );
				break;

			// Unlike the `<>` which is interpreted as plaintext, this is ignored entirely.
			case '#presumptuous-tag':
				break;

			case '#funky-comment':
			case '#comment':
				$html .= "<!--{$this->get_full_comment_text()}-->";
				break;

			case '#cdata-section':
				$html .= "<![CDATA[{$this->get_modifiable_text()}]]>";
				break;

			case 'html':
				$html .= '<!DOCTYPE html>';
				break;
		}

		if ( '#tag' !== $token_type ) {
			return $html;
		}

		$tag_name       = str_replace( "\x00", "\u{FFFD}", $this->get_tag() );
		$in_html        = 'html' === $this->get_namespace();
		$qualified_name = $in_html ? strtolower( $tag_name ) : $this->get_qualified_tag_name();

		if ( $this->is_tag_closer() ) {
			$html .= "</{$qualified_name}>";
			return $html;
		}

		$attribute_names = $this->get_attribute_names_with_prefix( '' );
		if ( ! isset( $attribute_names ) ) {
			$html .= "<{$qualified_name}>";
			return $html;
		}

		$html .= "<{$qualified_name}";
		foreach ( $attribute_names as $attribute_name ) {
			$html .= " {$this->get_qualified_attribute_name( $attribute_name )}";
			$value = $this->get_attribute( $attribute_name );

			if ( is_string( $value ) ) {
				$html .= '="' . htmlspecialchars( $value, ENT_QUOTES | ENT_SUBSTITUTE | ENT_HTML5 ) . '"';
			}

			$html = str_replace( "\x00", "\u{FFFD}", $html );
		}

		if ( ! $in_html && $this->has_self_closing_flag() ) {
			$html .= ' /';
		}

		$html .= '>';

		// Flush out self-contained elements.
		if ( $in_html && in_array( $tag_name, array( 'IFRAME', 'NOEMBED', 'NOFRAMES', 'SCRIPT', 'STYLE', 'TEXTAREA', 'TITLE', 'XMP' ), true ) ) {
			$text = $this->get_modifiable_text();

			switch ( $tag_name ) {
				case 'IFRAME':
				case 'NOEMBED':
				case 'NOFRAMES':
					$text = '';
					break;

				case 'SCRIPT':
				case 'STYLE':
					break;

				default:
					$text = htmlspecialchars( $text, ENT_QUOTES | ENT_SUBSTITUTE | ENT_HTML5, 'UTF-8' );
			}

			$html .= "{$text}</{$qualified_name}>";
		}

		return $html;
	}

	/**
	 * Parses next element in the 'initial' insertion mode.
	 *
	 * This internal function performs the 'initial' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#the-initial-insertion-mode
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_initial(): bool {
		$token_name = $this->get_token_name();
		$token_type = $this->get_token_type();
		$op_sigil   = '#tag' === $token_type ? ( parent::is_tag_closer() ? '-' : '+' ) : '';
		$op         = "{$op_sigil}{$token_name}";

		switch ( $op ) {
			/*
			 * > A character token that is one of U+0009 CHARACTER TABULATION,
			 * > U+000A LINE FEED (LF), U+000C FORM FEED (FF),
			 * > U+000D CARRIAGE RETURN (CR), or U+0020 SPACE
			 *
			 * Parse error: ignore the token.
			 */
			case '#text':
				if ( parent::TEXT_IS_WHITESPACE === $this->text_node_classification ) {
					return $this->step();
				}
				goto initial_anything_else;
				break;

			/*
			 * > A comment token
			 */
			case '#comment':
			case '#funky-comment':
			case '#presumptuous-tag':
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A DOCTYPE token
			 */
			case 'html':
				$doctype = $this->get_doctype_info();
				if ( null !== $doctype && 'quirks' === $doctype->indicated_compatability_mode ) {
					$this->compat_mode = WP_HTML_Tag_Processor::QUIRKS_MODE;
				}

				/*
				 * > Then, switch the insertion mode to "before html".
				 */
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_BEFORE_HTML;
				$this->insert_html_element( $this->state->current_token );
				return true;
		}

		/*
		 * > Anything else
		 */
		initial_anything_else:
		$this->compat_mode           = WP_HTML_Tag_Processor::QUIRKS_MODE;
		$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_BEFORE_HTML;
		return $this->step( self::REPROCESS_CURRENT_NODE );
	}

	/**
	 * Parses next element in the 'before html' insertion mode.
	 *
	 * This internal function performs the 'before html' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#the-before-html-insertion-mode
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_before_html(): bool {
		$token_name = $this->get_token_name();
		$token_type = $this->get_token_type();
		$is_closer  = parent::is_tag_closer();
		$op_sigil   = '#tag' === $token_type ? ( $is_closer ? '-' : '+' ) : '';
		$op         = "{$op_sigil}{$token_name}";

		switch ( $op ) {
			/*
			 * > A DOCTYPE token
			 */
			case 'html':
				// Parse error: ignore the token.
				return $this->step();

			/*
			 * > A comment token
			 */
			case '#comment':
			case '#funky-comment':
			case '#presumptuous-tag':
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A character token that is one of U+0009 CHARACTER TABULATION,
			 * > U+000A LINE FEED (LF), U+000C FORM FEED (FF),
			 * > U+000D CARRIAGE RETURN (CR), or U+0020 SPACE
			 *
			 * Parse error: ignore the token.
			 */
			case '#text':
				if ( parent::TEXT_IS_WHITESPACE === $this->text_node_classification ) {
					return $this->step();
				}
				goto before_html_anything_else;
				break;

			/*
			 * > A start tag whose tag name is "html"
			 */
			case '+HTML':
				$this->insert_html_element( $this->state->current_token );
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_BEFORE_HEAD;
				return true;

			/*
			 * > An end tag whose tag name is one of: "head", "body", "html", "br"
			 *
			 * Closing BR tags are always reported by the Tag Processor as opening tags.
			 */
			case '-HEAD':
			case '-BODY':
			case '-HTML':
				/*
				 * > Act as described in the "anything else" entry below.
				 */
				goto before_html_anything_else;
				break;
		}

		/*
		 * > Any other end tag
		 */
		if ( $is_closer ) {
			// Parse error: ignore the token.
			return $this->step();
		}

		/*
		 * > Anything else.
		 *
		 * > Create an html element whose node document is the Document object.
		 * > Append it to the Document object. Put this element in the stack of open elements.
		 * > Switch the insertion mode to "before head", then reprocess the token.
		 */
		before_html_anything_else:
		$this->insert_virtual_node( 'HTML' );
		$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_BEFORE_HEAD;
		return $this->step( self::REPROCESS_CURRENT_NODE );
	}

	/**
	 * Parses next element in the 'before head' insertion mode.
	 *
	 * This internal function performs the 'before head' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0 Stub implementation.
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#the-before-head-insertion-mode
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_before_head(): bool {
		$token_name = $this->get_token_name();
		$token_type = $this->get_token_type();
		$is_closer  = parent::is_tag_closer();
		$op_sigil   = '#tag' === $token_type ? ( $is_closer ? '-' : '+' ) : '';
		$op         = "{$op_sigil}{$token_name}";

		switch ( $op ) {
			/*
			 * > A character token that is one of U+0009 CHARACTER TABULATION,
			 * > U+000A LINE FEED (LF), U+000C FORM FEED (FF),
			 * > U+000D CARRIAGE RETURN (CR), or U+0020 SPACE
			 *
			 * Parse error: ignore the token.
			 */
			case '#text':
				if ( parent::TEXT_IS_WHITESPACE === $this->text_node_classification ) {
					return $this->step();
				}
				goto before_head_anything_else;
				break;

			/*
			 * > A comment token
			 */
			case '#comment':
			case '#funky-comment':
			case '#presumptuous-tag':
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A DOCTYPE token
			 */
			case 'html':
				// Parse error: ignore the token.
				return $this->step();

			/*
			 * > A start tag whose tag name is "html"
			 */
			case '+HTML':
				return $this->step_in_body();

			/*
			 * > A start tag whose tag name is "head"
			 */
			case '+HEAD':
				$this->insert_html_element( $this->state->current_token );
				$this->state->head_element   = $this->state->current_token;
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_HEAD;
				return true;

			/*
			 * > An end tag whose tag name is one of: "head", "body", "html", "br"
			 * > Act as described in the "anything else" entry below.
			 *
			 * Closing BR tags are always reported by the Tag Processor as opening tags.
			 */
			case '-HEAD':
			case '-BODY':
			case '-HTML':
				goto before_head_anything_else;
				break;
		}

		if ( $is_closer ) {
			// Parse error: ignore the token.
			return $this->step();
		}

		/*
		 * > Anything else
		 *
		 * > Insert an HTML element for a "head" start tag token with no attributes.
		 */
		before_head_anything_else:
		$this->state->head_element   = $this->insert_virtual_node( 'HEAD' );
		$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_HEAD;
		return $this->step( self::REPROCESS_CURRENT_NODE );
	}

	/**
	 * Parses next element in the 'in head' insertion mode.
	 *
	 * This internal function performs the 'in head' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/multipage/parsing.html#parsing-main-inhead
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_in_head(): bool {
		$token_name = $this->get_token_name();
		$token_type = $this->get_token_type();
		$is_closer  = parent::is_tag_closer();
		$op_sigil   = '#tag' === $token_type ? ( $is_closer ? '-' : '+' ) : '';
		$op         = "{$op_sigil}{$token_name}";

		switch ( $op ) {
			case '#text':
				/*
				 * > A character token that is one of U+0009 CHARACTER TABULATION,
				 * > U+000A LINE FEED (LF), U+000C FORM FEED (FF),
				 * > U+000D CARRIAGE RETURN (CR), or U+0020 SPACE
				 */
				if ( parent::TEXT_IS_WHITESPACE === $this->text_node_classification ) {
					// Insert the character.
					$this->insert_html_element( $this->state->current_token );
					return true;
				}

				goto in_head_anything_else;
				break;

			/*
			 * > A comment token
			 */
			case '#comment':
			case '#funky-comment':
			case '#presumptuous-tag':
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A DOCTYPE token
			 */
			case 'html':
				// Parse error: ignore the token.
				return $this->step();

			/*
			 * > A start tag whose tag name is "html"
			 */
			case '+HTML':
				return $this->step_in_body();

			/*
			 * > A start tag whose tag name is one of: "base", "basefont", "bgsound", "link"
			 */
			case '+BASE':
			case '+BASEFONT':
			case '+BGSOUND':
			case '+LINK':
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A start tag whose tag name is "meta"
			 */
			case '+META':
				$this->insert_html_element( $this->state->current_token );

				/*
				 * > If the active speculative HTML parser is null, then:
				 * >   - If the element has a charset attribute, and getting an encoding from
				 * >     its value results in an encoding, and the confidence is currently
				 * >     tentative, then change the encoding to the resulting encoding.
				 */
				$charset = $this->get_attribute( 'charset' );
				if ( is_string( $charset ) && 'tentative' === $this->state->encoding_confidence ) {
					$this->bail( 'Cannot yet process META tags with charset to determine encoding.' );
				}

				/*
				 * >   - Otherwise, if the element has an http-equiv attribute whose value is
				 * >     an ASCII case-insensitive match for the string "Content-Type", and
				 * >     the element has a content attribute, and applying the algorithm for
				 * >     extracting a character encoding from a meta element to that attribute's
				 * >     value returns an encoding, and the confidence is currently tentative,
				 * >     then change the encoding to the extracted encoding.
				 */
				$http_equiv = $this->get_attribute( 'http-equiv' );
				$content    = $this->get_attribute( 'content' );
				if (
					is_string( $http_equiv ) &&
					is_string( $content ) &&
					0 === strcasecmp( $http_equiv, 'Content-Type' ) &&
					'tentative' === $this->state->encoding_confidence
				) {
					$this->bail( 'Cannot yet process META tags with http-equiv Content-Type to determine encoding.' );
				}

				return true;

			/*
			 * > A start tag whose tag name is "title"
			 */
			case '+TITLE':
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A start tag whose tag name is "noscript", if the scripting flag is enabled
			 * > A start tag whose tag name is one of: "noframes", "style"
			 *
			 * The scripting flag is never enabled in this parser.
			 */
			case '+NOFRAMES':
			case '+STYLE':
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A start tag whose tag name is "noscript", if the scripting flag is disabled
			 */
			case '+NOSCRIPT':
				$this->insert_html_element( $this->state->current_token );
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_HEAD_NOSCRIPT;
				return true;

			/*
			 * > A start tag whose tag name is "script"
			 *
			 * @todo Could the adjusted insertion location be anything other than the current location?
			 */
			case '+SCRIPT':
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > An end tag whose tag name is "head"
			 */
			case '-HEAD':
				$this->state->stack_of_open_elements->pop();
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_AFTER_HEAD;
				return true;

			/*
			 * > An end tag whose tag name is one of: "body", "html", "br"
			 *
			 * BR tags are always reported by the Tag Processor as opening tags.
			 */
			case '-BODY':
			case '-HTML':
				/*
				 * > Act as described in the "anything else" entry below.
				 */
				goto in_head_anything_else;
				break;

			/*
			 * > A start tag whose tag name is "template"
			 *
			 * @todo Could the adjusted insertion location be anything other than the current location?
			 */
			case '+TEMPLATE':
				$this->state->active_formatting_elements->insert_marker();
				$this->state->frameset_ok = false;

				$this->state->insertion_mode                      = WP_HTML_Processor_State::INSERTION_MODE_IN_TEMPLATE;
				$this->state->stack_of_template_insertion_modes[] = WP_HTML_Processor_State::INSERTION_MODE_IN_TEMPLATE;

				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > An end tag whose tag name is "template"
			 */
			case '-TEMPLATE':
				if ( ! $this->state->stack_of_open_elements->contains( 'TEMPLATE' ) ) {
					// @todo Indicate a parse error once it's possible.
					return $this->step();
				}

				$this->generate_implied_end_tags_thoroughly();
				if ( ! $this->state->stack_of_open_elements->current_node_is( 'TEMPLATE' ) ) {
					// @todo Indicate a parse error once it's possible.
				}

				$this->state->stack_of_open_elements->pop_until( 'TEMPLATE' );
				$this->state->active_formatting_elements->clear_up_to_last_marker();
				array_pop( $this->state->stack_of_template_insertion_modes );
				$this->reset_insertion_mode_appropriately();
				return true;
		}

		/*
		 * > A start tag whose tag name is "head"
		 * > Any other end tag
		 */
		if ( '+HEAD' === $op || $is_closer ) {
			// Parse error: ignore the token.
			return $this->step();
		}

		/*
		 * > Anything else
		 */
		in_head_anything_else:
		$this->state->stack_of_open_elements->pop();
		$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_AFTER_HEAD;
		return $this->step( self::REPROCESS_CURRENT_NODE );
	}

	/**
	 * Parses next element in the 'in head noscript' insertion mode.
	 *
	 * This internal function performs the 'in head noscript' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0 Stub implementation.
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#parsing-main-inheadnoscript
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_in_head_noscript(): bool {
		$token_name = $this->get_token_name();
		$token_type = $this->get_token_type();
		$is_closer  = parent::is_tag_closer();
		$op_sigil   = '#tag' === $token_type ? ( $is_closer ? '-' : '+' ) : '';
		$op         = "{$op_sigil}{$token_name}";

		switch ( $op ) {
			/*
			 * > A character token that is one of U+0009 CHARACTER TABULATION,
			 * > U+000A LINE FEED (LF), U+000C FORM FEED (FF),
			 * > U+000D CARRIAGE RETURN (CR), or U+0020 SPACE
			 *
			 * Parse error: ignore the token.
			 */
			case '#text':
				if ( parent::TEXT_IS_WHITESPACE === $this->text_node_classification ) {
					return $this->step_in_head();
				}

				goto in_head_noscript_anything_else;
				break;

			/*
			 * > A DOCTYPE token
			 */
			case 'html':
				// Parse error: ignore the token.
				return $this->step();

			/*
			 * > A start tag whose tag name is "html"
			 */
			case '+HTML':
				return $this->step_in_body();

			/*
			 * > An end tag whose tag name is "noscript"
			 */
			case '-NOSCRIPT':
				$this->state->stack_of_open_elements->pop();
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_HEAD;
				return true;

			/*
			 * > A comment token
			 * >
			 * > A start tag whose tag name is one of: "basefont", "bgsound",
			 * > "link", "meta", "noframes", "style"
			 */
			case '#comment':
			case '#funky-comment':
			case '#presumptuous-tag':
			case '+BASEFONT':
			case '+BGSOUND':
			case '+LINK':
			case '+META':
			case '+NOFRAMES':
			case '+STYLE':
				return $this->step_in_head();

			/*
			 * > An end tag whose tag name is "br"
			 *
			 * This should never happen, as the Tag Processor prevents showing a BR closing tag.
			 */
		}

		/*
		 * > A start tag whose tag name is one of: "head", "noscript"
		 * > Any other end tag
		 */
		if ( '+HEAD' === $op || '+NOSCRIPT' === $op || $is_closer ) {
			// Parse error: ignore the token.
			return $this->step();
		}

		/*
		 * > Anything else
		 *
		 * Anything here is a parse error.
		 */
		in_head_noscript_anything_else:
		$this->state->stack_of_open_elements->pop();
		$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_HEAD;
		return $this->step( self::REPROCESS_CURRENT_NODE );
	}

	/**
	 * Parses next element in the 'after head' insertion mode.
	 *
	 * This internal function performs the 'after head' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0 Stub implementation.
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#the-after-head-insertion-mode
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_after_head(): bool {
		$token_name = $this->get_token_name();
		$token_type = $this->get_token_type();
		$is_closer  = parent::is_tag_closer();
		$op_sigil   = '#tag' === $token_type ? ( $is_closer ? '-' : '+' ) : '';
		$op         = "{$op_sigil}{$token_name}";

		switch ( $op ) {
			/*
			 * > A character token that is one of U+0009 CHARACTER TABULATION,
			 * > U+000A LINE FEED (LF), U+000C FORM FEED (FF),
			 * > U+000D CARRIAGE RETURN (CR), or U+0020 SPACE
			 */
			case '#text':
				if ( parent::TEXT_IS_WHITESPACE === $this->text_node_classification ) {
					// Insert the character.
					$this->insert_html_element( $this->state->current_token );
					return true;
				}
				goto after_head_anything_else;
				break;

			/*
			 * > A comment token
			 */
			case '#comment':
			case '#funky-comment':
			case '#presumptuous-tag':
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A DOCTYPE token
			 */
			case 'html':
				// Parse error: ignore the token.
				return $this->step();

			/*
			 * > A start tag whose tag name is "html"
			 */
			case '+HTML':
				return $this->step_in_body();

			/*
			 * > A start tag whose tag name is "body"
			 */
			case '+BODY':
				$this->insert_html_element( $this->state->current_token );
				$this->state->frameset_ok    = false;
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_BODY;
				return true;

			/*
			 * > A start tag whose tag name is "frameset"
			 */
			case '+FRAMESET':
				$this->insert_html_element( $this->state->current_token );
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_FRAMESET;
				return true;

			/*
			 * > A start tag whose tag name is one of: "base", "basefont", "bgsound",
			 * > "link", "meta", "noframes", "script", "style", "template", "title"
			 *
			 * Anything here is a parse error.
			 */
			case '+BASE':
			case '+BASEFONT':
			case '+BGSOUND':
			case '+LINK':
			case '+META':
			case '+NOFRAMES':
			case '+SCRIPT':
			case '+STYLE':
			case '+TEMPLATE':
			case '+TITLE':
				/*
				 * > Push the node pointed to by the head element pointer onto the stack of open elements.
				 * > Process the token using the rules for the "in head" insertion mode.
				 * > Remove the node pointed to by the head element pointer from the stack of open elements. (It might not be the current node at this point.)
				 */
				$this->bail( 'Cannot process elements after HEAD which reopen the HEAD element.' );
				/*
				 * Do not leave this break in when adding support; it's here to prevent
				 * WPCS from getting confused at the switch structure without a return,
				 * because it doesn't know that `bail()` always throws.
				 */
				break;

			/*
			 * > An end tag whose tag name is "template"
			 */
			case '-TEMPLATE':
				return $this->step_in_head();

			/*
			 * > An end tag whose tag name is one of: "body", "html", "br"
			 *
			 * Closing BR tags are always reported by the Tag Processor as opening tags.
			 */
			case '-BODY':
			case '-HTML':
				/*
				 * > Act as described in the "anything else" entry below.
				 */
				goto after_head_anything_else;
				break;
		}

		/*
		 * > A start tag whose tag name is "head"
		 * > Any other end tag
		 */
		if ( '+HEAD' === $op || $is_closer ) {
			// Parse error: ignore the token.
			return $this->step();
		}

		/*
		 * > Anything else
		 * > Insert an HTML element for a "body" start tag token with no attributes.
		 */
		after_head_anything_else:
		$this->insert_virtual_node( 'BODY' );
		$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_BODY;
		return $this->step( self::REPROCESS_CURRENT_NODE );
	}

	/**
	 * Parses next element in the 'in body' insertion mode.
	 *
	 * This internal function performs the 'in body' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.4.0
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#parsing-main-inbody
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_in_body(): bool {
		$token_name = $this->get_token_name();
		$token_type = $this->get_token_type();
		$op_sigil   = '#tag' === $token_type ? ( parent::is_tag_closer() ? '-' : '+' ) : '';
		$op         = "{$op_sigil}{$token_name}";

		switch ( $op ) {
			case '#text':
				/*
				 * > A character token that is U+0000 NULL
				 *
				 * Any successive sequence of NULL bytes is ignored and won't
				 * trigger active format reconstruction. Therefore, if the text
				 * only comprises NULL bytes then the token should be ignored
				 * here, but if there are any other characters in the stream
				 * the active formats should be reconstructed.
				 */
				if ( parent::TEXT_IS_NULL_SEQUENCE === $this->text_node_classification ) {
					// Parse error: ignore the token.
					return $this->step();
				}

				$this->reconstruct_active_formatting_elements();

				/*
				 * Whitespace-only text does not affect the frameset-ok flag.
				 * It is probably inter-element whitespace, but it may also
				 * contain character references which decode only to whitespace.
				 */
				if ( parent::TEXT_IS_GENERIC === $this->text_node_classification ) {
					$this->state->frameset_ok = false;
				}

				$this->insert_html_element( $this->state->current_token );
				return true;

			case '#comment':
			case '#funky-comment':
			case '#presumptuous-tag':
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A DOCTYPE token
			 * > Parse error. Ignore the token.
			 */
			case 'html':
				return $this->step();

			/*
			 * > A start tag whose tag name is "html"
			 */
			case '+HTML':
				if ( ! $this->state->stack_of_open_elements->contains( 'TEMPLATE' ) ) {
					/*
					 * > Otherwise, for each attribute on the token, check to see if the attribute
					 * > is already present on the top element of the stack of open elements. If
					 * > it is not, add the attribute and its corresponding value to that element.
					 *
					 * This parser does not currently support this behavior: ignore the token.
					 */
				}

				// Ignore the token.
				return $this->step();

			/*
			 * > A start tag whose tag name is one of: "base", "basefont", "bgsound", "link",
			 * > "meta", "noframes", "script", "style", "template", "title"
			 * >
			 * > An end tag whose tag name is "template"
			 */
			case '+BASE':
			case '+BASEFONT':
			case '+BGSOUND':
			case '+LINK':
			case '+META':
			case '+NOFRAMES':
			case '+SCRIPT':
			case '+STYLE':
			case '+TEMPLATE':
			case '+TITLE':
			case '-TEMPLATE':
				return $this->step_in_head();

			/*
			 * > A start tag whose tag name is "body"
			 *
			 * This tag in the IN BODY insertion mode is a parse error.
			 */
			case '+BODY':
				if (
					1 === $this->state->stack_of_open_elements->count() ||
					'BODY' !== ( $this->state->stack_of_open_elements->at( 2 )->node_name ?? null ) ||
					$this->state->stack_of_open_elements->contains( 'TEMPLATE' )
				) {
					// Ignore the token.
					return $this->step();
				}

				/*
				 * > Otherwise, set the frameset-ok flag to "not ok"; then, for each attribute
				 * > on the token, check to see if the attribute is already present on the body
				 * > element (the second element) on the stack of open elements, and if it is
				 * > not, add the attribute and its corresponding value to that element.
				 *
				 * This parser does not currently support this behavior: ignore the token.
				 */
				$this->state->frameset_ok = false;
				return $this->step();

			/*
			 * > A start tag whose tag name is "frameset"
			 *
			 * This tag in the IN BODY insertion mode is a parse error.
			 */
			case '+FRAMESET':
				if (
					1 === $this->state->stack_of_open_elements->count() ||
					'BODY' !== ( $this->state->stack_of_open_elements->at( 2 )->node_name ?? null ) ||
					false === $this->state->frameset_ok
				) {
					// Ignore the token.
					return $this->step();
				}

				/*
				 * > Otherwise, run the following steps:
				 */
				$this->bail( 'Cannot process non-ignored FRAMESET tags.' );
				break;

			/*
			 * > An end tag whose tag name is "body"
			 */
			case '-BODY':
				if ( ! $this->state->stack_of_open_elements->has_element_in_scope( 'BODY' ) ) {
					// Parse error: ignore the token.
					return $this->step();
				}

				/*
				 * > Otherwise, if there is a node in the stack of open elements that is not either a
				 * > dd element, a dt element, an li element, an optgroup element, an option element,
				 * > a p element, an rb element, an rp element, an rt element, an rtc element, a tbody
				 * > element, a td element, a tfoot element, a th element, a thread element, a tr
				 * > element, the body element, or the html element, then this is a parse error.
				 *
				 * There is nothing to do for this parse error, so don't check for it.
				 */

				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_AFTER_BODY;
				return true;

			/*
			 * > An end tag whose tag name is "html"
			 */
			case '-HTML':
				if ( ! $this->state->stack_of_open_elements->has_element_in_scope( 'BODY' ) ) {
					// Parse error: ignore the token.
					return $this->step();
				}

				/*
				 * > Otherwise, if there is a node in the stack of open elements that is not either a
				 * > dd element, a dt element, an li element, an optgroup element, an option element,
				 * > a p element, an rb element, an rp element, an rt element, an rtc element, a tbody
				 * > element, a td element, a tfoot element, a th element, a thread element, a tr
				 * > element, the body element, or the html element, then this is a parse error.
				 *
				 * There is nothing to do for this parse error, so don't check for it.
				 */

				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_AFTER_BODY;
				return $this->step( self::REPROCESS_CURRENT_NODE );

			/*
			 * > A start tag whose tag name is one of: "address", "article", "aside",
			 * > "blockquote", "center", "details", "dialog", "dir", "div", "dl",
			 * > "fieldset", "figcaption", "figure", "footer", "header", "hgroup",
			 * > "main", "menu", "nav", "ol", "p", "search", "section", "summary", "ul"
			 */
			case '+ADDRESS':
			case '+ARTICLE':
			case '+ASIDE':
			case '+BLOCKQUOTE':
			case '+CENTER':
			case '+DETAILS':
			case '+DIALOG':
			case '+DIR':
			case '+DIV':
			case '+DL':
			case '+FIELDSET':
			case '+FIGCAPTION':
			case '+FIGURE':
			case '+FOOTER':
			case '+HEADER':
			case '+HGROUP':
			case '+MAIN':
			case '+MENU':
			case '+NAV':
			case '+OL':
			case '+P':
			case '+SEARCH':
			case '+SECTION':
			case '+SUMMARY':
			case '+UL':
				if ( $this->state->stack_of_open_elements->has_p_in_button_scope() ) {
					$this->close_a_p_element();
				}

				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A start tag whose tag name is one of: "h1", "h2", "h3", "h4", "h5", "h6"
			 */
			case '+H1':
			case '+H2':
			case '+H3':
			case '+H4':
			case '+H5':
			case '+H6':
				if ( $this->state->stack_of_open_elements->has_p_in_button_scope() ) {
					$this->close_a_p_element();
				}

				if (
					in_array(
						$this->state->stack_of_open_elements->current_node()->node_name,
						array( 'H1', 'H2', 'H3', 'H4', 'H5', 'H6' ),
						true
					)
				) {
					// @todo Indicate a parse error once it's possible.
					$this->state->stack_of_open_elements->pop();
				}

				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A start tag whose tag name is one of: "pre", "listing"
			 */
			case '+PRE':
			case '+LISTING':
				if ( $this->state->stack_of_open_elements->has_p_in_button_scope() ) {
					$this->close_a_p_element();
				}

				/*
				 * > If the next token is a U+000A LINE FEED (LF) character token,
				 * > then ignore that token and move on to the next one. (Newlines
				 * > at the start of pre blocks are ignored as an authoring convenience.)
				 *
				 * This is handled in `get_modifiable_text()`.
				 */

				$this->insert_html_element( $this->state->current_token );
				$this->state->frameset_ok = false;
				return true;

			/*
			 * > A start tag whose tag name is "form"
			 */
			case '+FORM':
				$stack_contains_template = $this->state->stack_of_open_elements->contains( 'TEMPLATE' );

				if ( isset( $this->state->form_element ) && ! $stack_contains_template ) {
					// Parse error: ignore the token.
					return $this->step();
				}

				if ( $this->state->stack_of_open_elements->has_p_in_button_scope() ) {
					$this->close_a_p_element();
				}

				$this->insert_html_element( $this->state->current_token );
				if ( ! $stack_contains_template ) {
					$this->state->form_element = $this->state->current_token;
				}

				return true;

			/*
			 * > A start tag whose tag name is "li"
			 * > A start tag whose tag name is one of: "dd", "dt"
			 */
			case '+DD':
			case '+DT':
			case '+LI':
				$this->state->frameset_ok = false;
				$node                     = $this->state->stack_of_open_elements->current_node();
				$is_li                    = 'LI' === $token_name;

				in_body_list_loop:
				/*
				 * The logic for LI and DT/DD is the same except for one point: LI elements _only_
				 * close other LI elements, but a DT or DD element closes _any_ open DT or DD element.
				 */
				if ( $is_li ? 'LI' === $node->node_name : ( 'DD' === $node->node_name || 'DT' === $node->node_name ) ) {
					$node_name = $is_li ? 'LI' : $node->node_name;
					$this->generate_implied_end_tags( $node_name );
					if ( ! $this->state->stack_of_open_elements->current_node_is( $node_name ) ) {
						// @todo Indicate a parse error once it's possible. This error does not impact the logic here.
					}

					$this->state->stack_of_open_elements->pop_until( $node_name );
					goto in_body_list_done;
				}

				if (
					'ADDRESS' !== $node->node_name &&
					'DIV' !== $node->node_name &&
					'P' !== $node->node_name &&
					self::is_special( $node )
				) {
					/*
					 * > If node is in the special category, but is not an address, div,
					 * > or p element, then jump to the step labeled done below.
					 */
					goto in_body_list_done;
				} else {
					/*
					 * > Otherwise, set node to the previous entry in the stack of open elements
					 * > and return to the step labeled loop.
					 */
					foreach ( $this->state->stack_of_open_elements->walk_up( $node ) as $item ) {
						$node = $item;
						break;
					}
					goto in_body_list_loop;
				}

				in_body_list_done:
				if ( $this->state->stack_of_open_elements->has_p_in_button_scope() ) {
					$this->close_a_p_element();
				}

				$this->insert_html_element( $this->state->current_token );
				return true;

			case '+PLAINTEXT':
				if ( $this->state->stack_of_open_elements->has_p_in_button_scope() ) {
					$this->close_a_p_element();
				}

				/*
				 * @todo This may need to be handled in the Tag Processor and turn into
				 *       a single self-contained tag like TEXTAREA, whose modifiable text
				 *       is the rest of the input document as plaintext.
				 */
				$this->bail( 'Cannot process PLAINTEXT elements.' );
				break;

			/*
			 * > A start tag whose tag name is "button"
			 */
			case '+BUTTON':
				if ( $this->state->stack_of_open_elements->has_element_in_scope( 'BUTTON' ) ) {
					// @todo Indicate a parse error once it's possible. This error does not impact the logic here.
					$this->generate_implied_end_tags();
					$this->state->stack_of_open_elements->pop_until( 'BUTTON' );
				}

				$this->reconstruct_active_formatting_elements();
				$this->insert_html_element( $this->state->current_token );
				$this->state->frameset_ok = false;

				return true;

			/*
			 * > An end tag whose tag name is one of: "address", "article", "aside", "blockquote",
			 * > "button", "center", "details", "dialog", "dir", "div", "dl", "fieldset",
			 * > "figcaption", "figure", "footer", "header", "hgroup", "listing", "main",
			 * > "menu", "nav", "ol", "pre", "search", "section", "summary", "ul"
			 */
			case '-ADDRESS':
			case '-ARTICLE':
			case '-ASIDE':
			case '-BLOCKQUOTE':
			case '-BUTTON':
			case '-CENTER':
			case '-DETAILS':
			case '-DIALOG':
			case '-DIR':
			case '-DIV':
			case '-DL':
			case '-FIELDSET':
			case '-FIGCAPTION':
			case '-FIGURE':
			case '-FOOTER':
			case '-HEADER':
			case '-HGROUP':
			case '-LISTING':
			case '-MAIN':
			case '-MENU':
			case '-NAV':
			case '-OL':
			case '-PRE':
			case '-SEARCH':
			case '-SECTION':
			case '-SUMMARY':
			case '-UL':
				if ( ! $this->state->stack_of_open_elements->has_element_in_scope( $token_name ) ) {
					// @todo Report parse error.
					// Ignore the token.
					return $this->step();
				}

				$this->generate_implied_end_tags();
				if ( ! $this->state->stack_of_open_elements->current_node_is( $token_name ) ) {
					// @todo Record parse error: this error doesn't impact parsing.
				}
				$this->state->stack_of_open_elements->pop_until( $token_name );
				return true;

			/*
			 * > An end tag whose tag name is "form"
			 */
			case '-FORM':
				if ( ! $this->state->stack_of_open_elements->contains( 'TEMPLATE' ) ) {
					$node                      = $this->state->form_element;
					$this->state->form_element = null;

					/*
					 * > If node is null or if the stack of open elements does not have node
					 * > in scope, then this is a parse error; return and ignore the token.
					 *
					 * @todo It's necessary to check if the form token itself is in scope, not
					 *       simply whether any FORM is in scope.
					 */
					if (
						null === $node ||
						! $this->state->stack_of_open_elements->has_element_in_scope( 'FORM' )
					) {
						// Parse error: ignore the token.
						return $this->step();
					}

					$this->generate_implied_end_tags();
					if ( $node !== $this->state->stack_of_open_elements->current_node() ) {
						// @todo Indicate a parse error once it's possible. This error does not impact the logic here.
						$this->bail( 'Cannot close a FORM when other elements remain open as this would throw off the breadcrumbs for the following tokens.' );
					}

					$this->state->stack_of_open_elements->remove_node( $node );
					return true;
				} else {
					/*
					 * > If the stack of open elements does not have a form element in scope,
					 * > then this is a parse error; return and ignore the token.
					 *
					 * Note that unlike in the clause above, this is checking for any FORM in scope.
					 */
					if ( ! $this->state->stack_of_open_elements->has_element_in_scope( 'FORM' ) ) {
						// Parse error: ignore the token.
						return $this->step();
					}

					$this->generate_implied_end_tags();

					if ( ! $this->state->stack_of_open_elements->current_node_is( 'FORM' ) ) {
						// @todo Indicate a parse error once it's possible. This error does not impact the logic here.
					}

					$this->state->stack_of_open_elements->pop_until( 'FORM' );
					return true;
				}
				break;

			/*
			 * > An end tag whose tag name is "p"
			 */
			case '-P':
				if ( ! $this->state->stack_of_open_elements->has_p_in_button_scope() ) {
					$this->insert_html_element( $this->state->current_token );
				}

				$this->close_a_p_element();
				return true;

			/*
			 * > An end tag whose tag name is "li"
			 * > An end tag whose tag name is one of: "dd", "dt"
			 */
			case '-DD':
			case '-DT':
			case '-LI':
				if (
					/*
					 * An end tag whose tag name is "li":
					 * If the stack of open elements does not have an li element in list item scope,
					 * then this is a parse error; ignore the token.
					 */
					(
						'LI' === $token_name &&
						! $this->state->stack_of_open_elements->has_element_in_list_item_scope( 'LI' )
					) ||
					/*
					 * An end tag whose tag name is one of: "dd", "dt":
					 * If the stack of open elements does not have an element in scope that is an
					 * HTML element with the same tag name as that of the token, then this is a
					 * parse error; ignore the token.
					 */
					(
						'LI' !== $token_name &&
						! $this->state->stack_of_open_elements->has_element_in_scope( $token_name )
					)
				) {
					/*
					 * This is a parse error, ignore the token.
					 *
					 * @todo Indicate a parse error once it's possible.
					 */
					return $this->step();
				}

				$this->generate_implied_end_tags( $token_name );

				if ( ! $this->state->stack_of_open_elements->current_node_is( $token_name ) ) {
					// @todo Indicate a parse error once it's possible. This error does not impact the logic here.
				}

				$this->state->stack_of_open_elements->pop_until( $token_name );
				return true;

			/*
			 * > An end tag whose tag name is one of: "h1", "h2", "h3", "h4", "h5", "h6"
			 */
			case '-H1':
			case '-H2':
			case '-H3':
			case '-H4':
			case '-H5':
			case '-H6':
				if ( ! $this->state->stack_of_open_elements->has_element_in_scope( '(internal: H1 through H6 - do not use)' ) ) {
					/*
					 * This is a parse error; ignore the token.
					 *
					 * @todo Indicate a parse error once it's possible.
					 */
					return $this->step();
				}

				$this->generate_implied_end_tags();

				if ( ! $this->state->stack_of_open_elements->current_node_is( $token_name ) ) {
					// @todo Record parse error: this error doesn't impact parsing.
				}

				$this->state->stack_of_open_elements->pop_until( '(internal: H1 through H6 - do not use)' );
				return true;

			/*
			 * > A start tag whose tag name is "a"
			 */
			case '+A':
				foreach ( $this->state->active_formatting_elements->walk_up() as $item ) {
					switch ( $item->node_name ) {
						case 'marker':
							break 2;

						case 'A':
							$this->run_adoption_agency_algorithm();
							$this->state->active_formatting_elements->remove_node( $item );
							$this->state->stack_of_open_elements->remove_node( $item );
							break 2;
					}
				}

				$this->reconstruct_active_formatting_elements();
				$this->insert_html_element( $this->state->current_token );
				$this->state->active_formatting_elements->push( $this->state->current_token );
				return true;

			/*
			 * > A start tag whose tag name is one of: "b", "big", "code", "em", "font", "i",
			 * > "s", "small", "strike", "strong", "tt", "u"
			 */
			case '+B':
			case '+BIG':
			case '+CODE':
			case '+EM':
			case '+FONT':
			case '+I':
			case '+S':
			case '+SMALL':
			case '+STRIKE':
			case '+STRONG':
			case '+TT':
			case '+U':
				$this->reconstruct_active_formatting_elements();
				$this->insert_html_element( $this->state->current_token );
				$this->state->active_formatting_elements->push( $this->state->current_token );
				return true;

			/*
			 * > A start tag whose tag name is "nobr"
			 */
			case '+NOBR':
				$this->reconstruct_active_formatting_elements();

				if ( $this->state->stack_of_open_elements->has_element_in_scope( 'NOBR' ) ) {
					// Parse error.
					$this->run_adoption_agency_algorithm();
					$this->reconstruct_active_formatting_elements();
				}

				$this->insert_html_element( $this->state->current_token );
				$this->state->active_formatting_elements->push( $this->state->current_token );
				return true;

			/*
			 * > An end tag whose tag name is one of: "a", "b", "big", "code", "em", "font", "i",
			 * > "nobr", "s", "small", "strike", "strong", "tt", "u"
			 */
			case '-A':
			case '-B':
			case '-BIG':
			case '-CODE':
			case '-EM':
			case '-FONT':
			case '-I':
			case '-NOBR':
			case '-S':
			case '-SMALL':
			case '-STRIKE':
			case '-STRONG':
			case '-TT':
			case '-U':
				$this->run_adoption_agency_algorithm();
				return true;

			/*
			 * > A start tag whose tag name is one of: "applet", "marquee", "object"
			 */
			case '+APPLET':
			case '+MARQUEE':
			case '+OBJECT':
				$this->reconstruct_active_formatting_elements();
				$this->insert_html_element( $this->state->current_token );
				$this->state->active_formatting_elements->insert_marker();
				$this->state->frameset_ok = false;
				return true;

			/*
			 * > A end tag token whose tag name is one of: "applet", "marquee", "object"
			 */
			case '-APPLET':
			case '-MARQUEE':
			case '-OBJECT':
				if ( ! $this->state->stack_of_open_elements->has_element_in_scope( $token_name ) ) {
					// Parse error: ignore the token.
					return $this->step();
				}

				$this->generate_implied_end_tags();
				if ( ! $this->state->stack_of_open_elements->current_node_is( $token_name ) ) {
					// This is a parse error.
				}

				$this->state->stack_of_open_elements->pop_until( $token_name );
				$this->state->active_formatting_elements->clear_up_to_last_marker();
				return true;

			/*
			 * > A start tag whose tag name is "table"
			 */
			case '+TABLE':
				/*
				 * > If the Document is not set to quirks mode, and the stack of open elements
				 * > has a p element in button scope, then close a p element.
				 */
				if (
					WP_HTML_Tag_Processor::QUIRKS_MODE !== $this->compat_mode &&
					$this->state->stack_of_open_elements->has_p_in_button_scope()
				) {
					$this->close_a_p_element();
				}

				$this->insert_html_element( $this->state->current_token );
				$this->state->frameset_ok    = false;
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE;
				return true;

			/*
			 * > An end tag whose tag name is "br"
			 *
			 * This is prevented from happening because the Tag Processor
			 * reports all closing BR tags as if they were opening tags.
			 */

			/*
			 * > A start tag whose tag name is one of: "area", "br", "embed", "img", "keygen", "wbr"
			 */
			case '+AREA':
			case '+BR':
			case '+EMBED':
			case '+IMG':
			case '+KEYGEN':
			case '+WBR':
				$this->reconstruct_active_formatting_elements();
				$this->insert_html_element( $this->state->current_token );
				$this->state->frameset_ok = false;
				return true;

			/*
			 * > A start tag whose tag name is "input"
			 */
			case '+INPUT':
				$this->reconstruct_active_formatting_elements();
				$this->insert_html_element( $this->state->current_token );

				/*
				 * > If the token does not have an attribute with the name "type", or if it does,
				 * > but that attribute's value is not an ASCII case-insensitive match for the
				 * > string "hidden", then: set the frameset-ok flag to "not ok".
				 */
				$type_attribute = $this->get_attribute( 'type' );
				if ( ! is_string( $type_attribute ) || 'hidden' !== strtolower( $type_attribute ) ) {
					$this->state->frameset_ok = false;
				}

				return true;

			/*
			 * > A start tag whose tag name is one of: "param", "source", "track"
			 */
			case '+PARAM':
			case '+SOURCE':
			case '+TRACK':
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A start tag whose tag name is "hr"
			 */
			case '+HR':
				if ( $this->state->stack_of_open_elements->has_p_in_button_scope() ) {
					$this->close_a_p_element();
				}
				$this->insert_html_element( $this->state->current_token );
				$this->state->frameset_ok = false;
				return true;

			/*
			 * > A start tag whose tag name is "image"
			 */
			case '+IMAGE':
				/*
				 * > Parse error. Change the token's tag name to "img" and reprocess it. (Don't ask.)
				 *
				 * Note that this is handled elsewhere, so it should not be possible to reach this code.
				 */
				$this->bail( "Cannot process an IMAGE tag. (Don't ask.)" );
				break;

			/*
			 * > A start tag whose tag name is "textarea"
			 */
			case '+TEXTAREA':
				$this->insert_html_element( $this->state->current_token );

				/*
				 * > If the next token is a U+000A LINE FEED (LF) character token, then ignore
				 * > that token and move on to the next one. (Newlines at the start of
				 * > textarea elements are ignored as an authoring convenience.)
				 *
				 * This is handled in `get_modifiable_text()`.
				 */

				$this->state->frameset_ok = false;

				/*
				 * > Switch the insertion mode to "text".
				 *
				 * As a self-contained node, this behavior is handled in the Tag Processor.
				 */
				return true;

			/*
			 * > A start tag whose tag name is "xmp"
			 */
			case '+XMP':
				if ( $this->state->stack_of_open_elements->has_p_in_button_scope() ) {
					$this->close_a_p_element();
				}

				$this->reconstruct_active_formatting_elements();
				$this->state->frameset_ok = false;

				/*
				 * > Follow the generic raw text element parsing algorithm.
				 *
				 * As a self-contained node, this behavior is handled in the Tag Processor.
				 */
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * A start tag whose tag name is "iframe"
			 */
			case '+IFRAME':
				$this->state->frameset_ok = false;

				/*
				 * > Follow the generic raw text element parsing algorithm.
				 *
				 * As a self-contained node, this behavior is handled in the Tag Processor.
				 */
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A start tag whose tag name is "noembed"
			 * > A start tag whose tag name is "noscript", if the scripting flag is enabled
			 *
			 * The scripting flag is never enabled in this parser.
			 */
			case '+NOEMBED':
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A start tag whose tag name is "select"
			 */
			case '+SELECT':
				$this->reconstruct_active_formatting_elements();
				$this->insert_html_element( $this->state->current_token );
				$this->state->frameset_ok = false;

				switch ( $this->state->insertion_mode ) {
					/*
					 * > If the insertion mode is one of "in table", "in caption", "in table body", "in row",
					 * > or "in cell", then switch the insertion mode to "in select in table".
					 */
					case WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE:
					case WP_HTML_Processor_State::INSERTION_MODE_IN_CAPTION:
					case WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE_BODY:
					case WP_HTML_Processor_State::INSERTION_MODE_IN_ROW:
					case WP_HTML_Processor_State::INSERTION_MODE_IN_CELL:
						$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_SELECT_IN_TABLE;
						break;

					/*
					 * > Otherwise, switch the insertion mode to "in select".
					 */
					default:
						$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_SELECT;
						break;
				}
				return true;

			/*
			 * > A start tag whose tag name is one of: "optgroup", "option"
			 */
			case '+OPTGROUP':
			case '+OPTION':
				if ( $this->state->stack_of_open_elements->current_node_is( 'OPTION' ) ) {
					$this->state->stack_of_open_elements->pop();
				}
				$this->reconstruct_active_formatting_elements();
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A start tag whose tag name is one of: "rb", "rtc"
			 */
			case '+RB':
			case '+RTC':
				if ( $this->state->stack_of_open_elements->has_element_in_scope( 'RUBY' ) ) {
					$this->generate_implied_end_tags();

					if ( $this->state->stack_of_open_elements->current_node_is( 'RUBY' ) ) {
						// @todo Indicate a parse error once it's possible.
					}
				}

				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A start tag whose tag name is one of: "rp", "rt"
			 */
			case '+RP':
			case '+RT':
				if ( $this->state->stack_of_open_elements->has_element_in_scope( 'RUBY' ) ) {
					$this->generate_implied_end_tags( 'RTC' );

					$current_node_name = $this->state->stack_of_open_elements->current_node()->node_name;
					if ( 'RTC' === $current_node_name || 'RUBY' === $current_node_name ) {
						// @todo Indicate a parse error once it's possible.
					}
				}

				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A start tag whose tag name is "math"
			 */
			case '+MATH':
				$this->reconstruct_active_formatting_elements();

				/*
				 * @todo Adjust MathML attributes for the token. (This fixes the case of MathML attributes that are not all lowercase.)
				 * @todo Adjust foreign attributes for the token. (This fixes the use of namespaced attributes, in particular XLink.)
				 *
				 * These ought to be handled in the attribute methods.
				 */
				$this->state->current_token->namespace = 'math';
				$this->insert_html_element( $this->state->current_token );
				if ( $this->state->current_token->has_self_closing_flag ) {
					$this->state->stack_of_open_elements->pop();
				}
				return true;

			/*
			 * > A start tag whose tag name is "svg"
			 */
			case '+SVG':
				$this->reconstruct_active_formatting_elements();

				/*
				 * @todo Adjust SVG attributes for the token. (This fixes the case of SVG attributes that are not all lowercase.)
				 * @todo Adjust foreign attributes for the token. (This fixes the use of namespaced attributes, in particular XLink in SVG.)
				 *
				 * These ought to be handled in the attribute methods.
				 */
				$this->state->current_token->namespace = 'svg';
				$this->insert_html_element( $this->state->current_token );
				if ( $this->state->current_token->has_self_closing_flag ) {
					$this->state->stack_of_open_elements->pop();
				}
				return true;

			/*
			 * > A start tag whose tag name is one of: "caption", "col", "colgroup",
			 * > "frame", "head", "tbody", "td", "tfoot", "th", "thead", "tr"
			 */
			case '+CAPTION':
			case '+COL':
			case '+COLGROUP':
			case '+FRAME':
			case '+HEAD':
			case '+TBODY':
			case '+TD':
			case '+TFOOT':
			case '+TH':
			case '+THEAD':
			case '+TR':
				// Parse error. Ignore the token.
				return $this->step();
		}

		if ( ! parent::is_tag_closer() ) {
			/*
			 * > Any other start tag
			 */
			$this->reconstruct_active_formatting_elements();
			$this->insert_html_element( $this->state->current_token );
			return true;
		} else {
			/*
			 * > Any other end tag
			 */

			/*
			 * Find the corresponding tag opener in the stack of open elements, if
			 * it exists before reaching a special element, which provides a kind
			 * of boundary in the stack. For example, a `</custom-tag>` should not
			 * close anything beyond its containing `P` or `DIV` element.
			 */
			foreach ( $this->state->stack_of_open_elements->walk_up() as $node ) {
				if ( 'html' === $node->namespace && $token_name === $node->node_name ) {
					break;
				}

				if ( self::is_special( $node ) ) {
					// This is a parse error, ignore the token.
					return $this->step();
				}
			}

			$this->generate_implied_end_tags( $token_name );
			if ( $node !== $this->state->stack_of_open_elements->current_node() ) {
				// @todo Record parse error: this error doesn't impact parsing.
			}

			foreach ( $this->state->stack_of_open_elements->walk_up() as $item ) {
				$this->state->stack_of_open_elements->pop();
				if ( $node === $item ) {
					return true;
				}
			}
		}

		$this->bail( 'Should not have been able to reach end of IN BODY processing. Check HTML API code.' );
		// This unnecessary return prevents tools from inaccurately reporting type errors.
		return false;
	}

	/**
	 * Parses next element in the 'in table' insertion mode.
	 *
	 * This internal function performs the 'in table' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#parsing-main-intable
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_in_table(): bool {
		$token_name = $this->get_token_name();
		$token_type = $this->get_token_type();
		$op_sigil   = '#tag' === $token_type ? ( parent::is_tag_closer() ? '-' : '+' ) : '';
		$op         = "{$op_sigil}{$token_name}";

		switch ( $op ) {
			/*
			 * > A character token, if the current node is table,
			 * > tbody, template, tfoot, thead, or tr element
			 */
			case '#text':
				$current_node      = $this->state->stack_of_open_elements->current_node();
				$current_node_name = $current_node ? $current_node->node_name : null;
				if (
					$current_node_name && (
						'TABLE' === $current_node_name ||
						'TBODY' === $current_node_name ||
						'TEMPLATE' === $current_node_name ||
						'TFOOT' === $current_node_name ||
						'THEAD' === $current_node_name ||
						'TR' === $current_node_name
					)
				) {
					/*
					 * If the text is empty after processing HTML entities and stripping
					 * U+0000 NULL bytes then ignore the token.
					 */
					if ( parent::TEXT_IS_NULL_SEQUENCE === $this->text_node_classification ) {
						return $this->step();
					}

					/*
					 * This follows the rules for "in table text" insertion mode.
					 *
					 * Whitespace-only text nodes are inserted in-place. Otherwise
					 * foster parenting is enabled and the nodes would be
					 * inserted out-of-place.
					 *
					 * > If any of the tokens in the pending table character tokens
					 * > list are character tokens that are not ASCII whitespace,
					 * > then this is a parse error: reprocess the character tokens
					 * > in the pending table character tokens list using the rules
					 * > given in the "anything else" entry in the "in table"
					 * > insertion mode.
					 * >
					 * > Otherwise, insert the characters given by the pending table
					 * > character tokens list.
					 *
					 * @see https://html.spec.whatwg.org/#parsing-main-intabletext
					 */
					if ( parent::TEXT_IS_WHITESPACE === $this->text_node_classification ) {
						$this->insert_html_element( $this->state->current_token );
						return true;
					}

					// Non-whitespace would trigger fostering, unsupported at this time.
					$this->bail( 'Foster parenting is not supported.' );
					break;
				}
				break;

			/*
			 * > A comment token
			 */
			case '#comment':
			case '#funky-comment':
			case '#presumptuous-tag':
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A DOCTYPE token
			 */
			case 'html':
				// Parse error: ignore the token.
				return $this->step();

			/*
			 * > A start tag whose tag name is "caption"
			 */
			case '+CAPTION':
				$this->state->stack_of_open_elements->clear_to_table_context();
				$this->state->active_formatting_elements->insert_marker();
				$this->insert_html_element( $this->state->current_token );
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_CAPTION;
				return true;

			/*
			 * > A start tag whose tag name is "colgroup"
			 */
			case '+COLGROUP':
				$this->state->stack_of_open_elements->clear_to_table_context();
				$this->insert_html_element( $this->state->current_token );
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_COLUMN_GROUP;
				return true;

			/*
			 * > A start tag whose tag name is "col"
			 */
			case '+COL':
				$this->state->stack_of_open_elements->clear_to_table_context();

				/*
				 * > Insert an HTML element for a "colgroup" start tag token with no attributes,
				 * > then switch the insertion mode to "in column group".
				 */
				$this->insert_virtual_node( 'COLGROUP' );
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_COLUMN_GROUP;
				return $this->step( self::REPROCESS_CURRENT_NODE );

			/*
			 * > A start tag whose tag name is one of: "tbody", "tfoot", "thead"
			 */
			case '+TBODY':
			case '+TFOOT':
			case '+THEAD':
				$this->state->stack_of_open_elements->clear_to_table_context();
				$this->insert_html_element( $this->state->current_token );
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE_BODY;
				return true;

			/*
			 * > A start tag whose tag name is one of: "td", "th", "tr"
			 */
			case '+TD':
			case '+TH':
			case '+TR':
				$this->state->stack_of_open_elements->clear_to_table_context();
				/*
				 * > Insert an HTML element for a "tbody" start tag token with no attributes,
				 * > then switch the insertion mode to "in table body".
				 */
				$this->insert_virtual_node( 'TBODY' );
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE_BODY;
				return $this->step( self::REPROCESS_CURRENT_NODE );

			/*
			 * > A start tag whose tag name is "table"
			 *
			 * This tag in the IN TABLE insertion mode is a parse error.
			 */
			case '+TABLE':
				if ( ! $this->state->stack_of_open_elements->has_element_in_table_scope( 'TABLE' ) ) {
					return $this->step();
				}

				$this->state->stack_of_open_elements->pop_until( 'TABLE' );
				$this->reset_insertion_mode_appropriately();
				return $this->step( self::REPROCESS_CURRENT_NODE );

			/*
			 * > An end tag whose tag name is "table"
			 */
			case '-TABLE':
				if ( ! $this->state->stack_of_open_elements->has_element_in_table_scope( 'TABLE' ) ) {
					// @todo Indicate a parse error once it's possible.
					return $this->step();
				}

				$this->state->stack_of_open_elements->pop_until( 'TABLE' );
				$this->reset_insertion_mode_appropriately();
				return true;

			/*
			 * > An end tag whose tag name is one of: "body", "caption", "col", "colgroup", "html", "tbody", "td", "tfoot", "th", "thead", "tr"
			 */
			case '-BODY':
			case '-CAPTION':
			case '-COL':
			case '-COLGROUP':
			case '-HTML':
			case '-TBODY':
			case '-TD':
			case '-TFOOT':
			case '-TH':
			case '-THEAD':
			case '-TR':
				// Parse error: ignore the token.
				return $this->step();

			/*
			 * > A start tag whose tag name is one of: "style", "script", "template"
			 * > An end tag whose tag name is "template"
			 */
			case '+STYLE':
			case '+SCRIPT':
			case '+TEMPLATE':
			case '-TEMPLATE':
				/*
				 * > Process the token using the rules for the "in head" insertion mode.
				 */
				return $this->step_in_head();

			/*
			 * > A start tag whose tag name is "input"
			 *
			 * > If the token does not have an attribute with the name "type", or if it does, but
			 * > that attribute's value is not an ASCII case-insensitive match for the string
			 * > "hidden", then: act as described in the "anything else" entry below.
			 */
			case '+INPUT':
				$type_attribute = $this->get_attribute( 'type' );
				if ( ! is_string( $type_attribute ) || 'hidden' !== strtolower( $type_attribute ) ) {
					goto anything_else;
				}
				// @todo Indicate a parse error once it's possible.
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A start tag whose tag name is "form"
			 *
			 * This tag in the IN TABLE insertion mode is a parse error.
			 */
			case '+FORM':
				if (
					$this->state->stack_of_open_elements->has_element_in_scope( 'TEMPLATE' ) ||
					isset( $this->state->form_element )
				) {
					return $this->step();
				}

				// This FORM is special because it immediately closes and cannot have other children.
				$this->insert_html_element( $this->state->current_token );
				$this->state->form_element = $this->state->current_token;
				$this->state->stack_of_open_elements->pop();
				return true;
		}

		/*
		 * > Anything else
		 * > Parse error. Enable foster parenting, process the token using the rules for the
		 * > "in body" insertion mode, and then disable foster parenting.
		 *
		 * @todo Indicate a parse error once it's possible.
		 */
		anything_else:
		$this->bail( 'Foster parenting is not supported.' );
	}

	/**
	 * Parses next element in the 'in table text' insertion mode.
	 *
	 * This internal function performs the 'in table text' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0 Stub implementation.
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#parsing-main-intabletext
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_in_table_text(): bool {
		$this->bail( 'No support for parsing in the ' . WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE_TEXT . ' state.' );
	}

	/**
	 * Parses next element in the 'in caption' insertion mode.
	 *
	 * This internal function performs the 'in caption' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#parsing-main-incaption
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_in_caption(): bool {
		$tag_name = $this->get_tag();
		$op_sigil = $this->is_tag_closer() ? '-' : '+';
		$op       = "{$op_sigil}{$tag_name}";

		switch ( $op ) {
			/*
			 * > An end tag whose tag name is "caption"
			 * > A start tag whose tag name is one of: "caption", "col", "colgroup", "tbody", "td", "tfoot", "th", "thead", "tr"
			 * > An end tag whose tag name is "table"
			 *
			 * These tag handling rules are identical except for the final instruction.
			 * Handle them in a single block.
			 */
			case '-CAPTION':
			case '+CAPTION':
			case '+COL':
			case '+COLGROUP':
			case '+TBODY':
			case '+TD':
			case '+TFOOT':
			case '+TH':
			case '+THEAD':
			case '+TR':
			case '-TABLE':
				if ( ! $this->state->stack_of_open_elements->has_element_in_table_scope( 'CAPTION' ) ) {
					// Parse error: ignore the token.
					return $this->step();
				}

				$this->generate_implied_end_tags();
				if ( ! $this->state->stack_of_open_elements->current_node_is( 'CAPTION' ) ) {
					// @todo Indicate a parse error once it's possible.
				}

				$this->state->stack_of_open_elements->pop_until( 'CAPTION' );
				$this->state->active_formatting_elements->clear_up_to_last_marker();
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE;

				// If this is not a CAPTION end tag, the token should be reprocessed.
				if ( '-CAPTION' === $op ) {
					return true;
				}
				return $this->step( self::REPROCESS_CURRENT_NODE );

			/**
			 * > An end tag whose tag name is one of: "body", "col", "colgroup", "html", "tbody", "td", "tfoot", "th", "thead", "tr"
			 */
			case '-BODY':
			case '-COL':
			case '-COLGROUP':
			case '-HTML':
			case '-TBODY':
			case '-TD':
			case '-TFOOT':
			case '-TH':
			case '-THEAD':
			case '-TR':
				// Parse error: ignore the token.
				return $this->step();
		}

		/**
		 * > Anything else
		 * >   Process the token using the rules for the "in body" insertion mode.
		 */
		return $this->step_in_body();
	}

	/**
	 * Parses next element in the 'in column group' insertion mode.
	 *
	 * This internal function performs the 'in column group' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#parsing-main-incolgroup
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_in_column_group(): bool {
		$token_name = $this->get_token_name();
		$token_type = $this->get_token_type();
		$op_sigil   = '#tag' === $token_type ? ( parent::is_tag_closer() ? '-' : '+' ) : '';
		$op         = "{$op_sigil}{$token_name}";

		switch ( $op ) {
			/*
			 * > A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF),
			 * > U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), or U+0020 SPACE
			 */
			case '#text':
				if ( parent::TEXT_IS_WHITESPACE === $this->text_node_classification ) {
					// Insert the character.
					$this->insert_html_element( $this->state->current_token );
					return true;
				}

				goto in_column_group_anything_else;
				break;

			/*
			 * > A comment token
			 */
			case '#comment':
			case '#funky-comment':
			case '#presumptuous-tag':
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A DOCTYPE token
			 */
			case 'html':
				// @todo Indicate a parse error once it's possible.
				return $this->step();

			/*
			 * > A start tag whose tag name is "html"
			 */
			case '+HTML':
				return $this->step_in_body();

			/*
			 * > A start tag whose tag name is "col"
			 */
			case '+COL':
				$this->insert_html_element( $this->state->current_token );
				$this->state->stack_of_open_elements->pop();
				return true;

			/*
			 * > An end tag whose tag name is "colgroup"
			 */
			case '-COLGROUP':
				if ( ! $this->state->stack_of_open_elements->current_node_is( 'COLGROUP' ) ) {
					// @todo Indicate a parse error once it's possible.
					return $this->step();
				}
				$this->state->stack_of_open_elements->pop();
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE;
				return true;

			/*
			 * > An end tag whose tag name is "col"
			 */
			case '-COL':
				// Parse error: ignore the token.
				return $this->step();

			/*
			 * > A start tag whose tag name is "template"
			 * > An end tag whose tag name is "template"
			 */
			case '+TEMPLATE':
			case '-TEMPLATE':
				return $this->step_in_head();
		}

		in_column_group_anything_else:
		/*
		 * > Anything else
		 */
		if ( ! $this->state->stack_of_open_elements->current_node_is( 'COLGROUP' ) ) {
			// @todo Indicate a parse error once it's possible.
			return $this->step();
		}
		$this->state->stack_of_open_elements->pop();
		$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE;
		return $this->step( self::REPROCESS_CURRENT_NODE );
	}

	/**
	 * Parses next element in the 'in table body' insertion mode.
	 *
	 * This internal function performs the 'in table body' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#parsing-main-intbody
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_in_table_body(): bool {
		$tag_name = $this->get_tag();
		$op_sigil = $this->is_tag_closer() ? '-' : '+';
		$op       = "{$op_sigil}{$tag_name}";

		switch ( $op ) {
			/*
			 * > A start tag whose tag name is "tr"
			 */
			case '+TR':
				$this->state->stack_of_open_elements->clear_to_table_body_context();
				$this->insert_html_element( $this->state->current_token );
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_ROW;
				return true;

			/*
			 * > A start tag whose tag name is one of: "th", "td"
			 */
			case '+TH':
			case '+TD':
				// @todo Indicate a parse error once it's possible.
				$this->state->stack_of_open_elements->clear_to_table_body_context();
				$this->insert_virtual_node( 'TR' );
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_ROW;
				return $this->step( self::REPROCESS_CURRENT_NODE );

			/*
			 * > An end tag whose tag name is one of: "tbody", "tfoot", "thead"
			 */
			case '-TBODY':
			case '-TFOOT':
			case '-THEAD':
				if ( ! $this->state->stack_of_open_elements->has_element_in_table_scope( $tag_name ) ) {
					// Parse error: ignore the token.
					return $this->step();
				}

				$this->state->stack_of_open_elements->clear_to_table_body_context();
				$this->state->stack_of_open_elements->pop();
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE;
				return true;

			/*
			 * > A start tag whose tag name is one of: "caption", "col", "colgroup", "tbody", "tfoot", "thead"
			 * > An end tag whose tag name is "table"
			 */
			case '+CAPTION':
			case '+COL':
			case '+COLGROUP':
			case '+TBODY':
			case '+TFOOT':
			case '+THEAD':
			case '-TABLE':
				if (
					! $this->state->stack_of_open_elements->has_element_in_table_scope( 'TBODY' ) &&
					! $this->state->stack_of_open_elements->has_element_in_table_scope( 'THEAD' ) &&
					! $this->state->stack_of_open_elements->has_element_in_table_scope( 'TFOOT' )
				) {
					// Parse error: ignore the token.
					return $this->step();
				}
				$this->state->stack_of_open_elements->clear_to_table_body_context();
				$this->state->stack_of_open_elements->pop();
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE;
				return $this->step( self::REPROCESS_CURRENT_NODE );

			/*
			 * > An end tag whose tag name is one of: "body", "caption", "col", "colgroup", "html", "td", "th", "tr"
			 */
			case '-BODY':
			case '-CAPTION':
			case '-COL':
			case '-COLGROUP':
			case '-HTML':
			case '-TD':
			case '-TH':
			case '-TR':
				// Parse error: ignore the token.
				return $this->step();
		}

		/*
		 * > Anything else
		 * > Process the token using the rules for the "in table" insertion mode.
		 */
		return $this->step_in_table();
	}

	/**
	 * Parses next element in the 'in row' insertion mode.
	 *
	 * This internal function performs the 'in row' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#parsing-main-intr
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_in_row(): bool {
		$tag_name = $this->get_tag();
		$op_sigil = $this->is_tag_closer() ? '-' : '+';
		$op       = "{$op_sigil}{$tag_name}";

		switch ( $op ) {
			/*
			 * > A start tag whose tag name is one of: "th", "td"
			 */
			case '+TH':
			case '+TD':
				$this->state->stack_of_open_elements->clear_to_table_row_context();
				$this->insert_html_element( $this->state->current_token );
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_CELL;
				$this->state->active_formatting_elements->insert_marker();
				return true;

			/*
			 * > An end tag whose tag name is "tr"
			 */
			case '-TR':
				if ( ! $this->state->stack_of_open_elements->has_element_in_table_scope( 'TR' ) ) {
					// Parse error: ignore the token.
					return $this->step();
				}

				$this->state->stack_of_open_elements->clear_to_table_row_context();
				$this->state->stack_of_open_elements->pop();
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE_BODY;
				return true;

			/*
			 * > A start tag whose tag name is one of: "caption", "col", "colgroup", "tbody", "tfoot", "thead", "tr"
			 * > An end tag whose tag name is "table"
			 */
			case '+CAPTION':
			case '+COL':
			case '+COLGROUP':
			case '+TBODY':
			case '+TFOOT':
			case '+THEAD':
			case '+TR':
			case '-TABLE':
				if ( ! $this->state->stack_of_open_elements->has_element_in_table_scope( 'TR' ) ) {
					// Parse error: ignore the token.
					return $this->step();
				}

				$this->state->stack_of_open_elements->clear_to_table_row_context();
				$this->state->stack_of_open_elements->pop();
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE_BODY;
				return $this->step( self::REPROCESS_CURRENT_NODE );

			/*
			 * > An end tag whose tag name is one of: "tbody", "tfoot", "thead"
			 */
			case '-TBODY':
			case '-TFOOT':
			case '-THEAD':
				if ( ! $this->state->stack_of_open_elements->has_element_in_table_scope( $tag_name ) ) {
					// Parse error: ignore the token.
					return $this->step();
				}

				if ( ! $this->state->stack_of_open_elements->has_element_in_table_scope( 'TR' ) ) {
					// Ignore the token.
					return $this->step();
				}

				$this->state->stack_of_open_elements->clear_to_table_row_context();
				$this->state->stack_of_open_elements->pop();
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE_BODY;
				return $this->step( self::REPROCESS_CURRENT_NODE );

			/*
			 * > An end tag whose tag name is one of: "body", "caption", "col", "colgroup", "html", "td", "th"
			 */
			case '-BODY':
			case '-CAPTION':
			case '-COL':
			case '-COLGROUP':
			case '-HTML':
			case '-TD':
			case '-TH':
				// Parse error: ignore the token.
				return $this->step();
		}

		/*
		 * > Anything else
		 * >   Process the token using the rules for the "in table" insertion mode.
		 */
		return $this->step_in_table();
	}

	/**
	 * Parses next element in the 'in cell' insertion mode.
	 *
	 * This internal function performs the 'in cell' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#parsing-main-intd
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_in_cell(): bool {
		$tag_name = $this->get_tag();
		$op_sigil = $this->is_tag_closer() ? '-' : '+';
		$op       = "{$op_sigil}{$tag_name}";

		switch ( $op ) {
			/*
			 * > An end tag whose tag name is one of: "td", "th"
			 */
			case '-TD':
			case '-TH':
				if ( ! $this->state->stack_of_open_elements->has_element_in_table_scope( $tag_name ) ) {
					// Parse error: ignore the token.
					return $this->step();
				}

				$this->generate_implied_end_tags();

				/*
				 * @todo This needs to check if the current node is an HTML element, meaning that
				 *       when SVG and MathML support is added, this needs to differentiate between an
				 *       HTML element of the given name, such as `<center>`, and a foreign element of
				 *       the same given name.
				 */
				if ( ! $this->state->stack_of_open_elements->current_node_is( $tag_name ) ) {
					// @todo Indicate a parse error once it's possible.
				}

				$this->state->stack_of_open_elements->pop_until( $tag_name );
				$this->state->active_formatting_elements->clear_up_to_last_marker();
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_ROW;
				return true;

			/*
			 * > A start tag whose tag name is one of: "caption", "col", "colgroup", "tbody", "td",
			 * > "tfoot", "th", "thead", "tr"
			 */
			case '+CAPTION':
			case '+COL':
			case '+COLGROUP':
			case '+TBODY':
			case '+TD':
			case '+TFOOT':
			case '+TH':
			case '+THEAD':
			case '+TR':
				/*
				 * > Assert: The stack of open elements has a td or th element in table scope.
				 *
				 * Nothing to do here, except to verify in tests that this never appears.
				 */

				$this->close_cell();
				return $this->step( self::REPROCESS_CURRENT_NODE );

			/*
			 * > An end tag whose tag name is one of: "body", "caption", "col", "colgroup", "html"
			 */
			case '-BODY':
			case '-CAPTION':
			case '-COL':
			case '-COLGROUP':
			case '-HTML':
				// Parse error: ignore the token.
				return $this->step();

			/*
			 * > An end tag whose tag name is one of: "table", "tbody", "tfoot", "thead", "tr"
			 */
			case '-TABLE':
			case '-TBODY':
			case '-TFOOT':
			case '-THEAD':
			case '-TR':
				if ( ! $this->state->stack_of_open_elements->has_element_in_table_scope( $tag_name ) ) {
					// Parse error: ignore the token.
					return $this->step();
				}
				$this->close_cell();
				return $this->step( self::REPROCESS_CURRENT_NODE );
		}

		/*
		 * > Anything else
		 * >   Process the token using the rules for the "in body" insertion mode.
		 */
		return $this->step_in_body();
	}

	/**
	 * Parses next element in the 'in select' insertion mode.
	 *
	 * This internal function performs the 'in select' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/multipage/parsing.html#parsing-main-inselect
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_in_select(): bool {
		$token_name = $this->get_token_name();
		$token_type = $this->get_token_type();
		$op_sigil   = '#tag' === $token_type ? ( parent::is_tag_closer() ? '-' : '+' ) : '';
		$op         = "{$op_sigil}{$token_name}";

		switch ( $op ) {
			/*
			 * > Any other character token
			 */
			case '#text':
				/*
				 * > A character token that is U+0000 NULL
				 *
				 * If a text node only comprises null bytes then it should be
				 * entirely ignored and should not return to calling code.
				 */
				if ( parent::TEXT_IS_NULL_SEQUENCE === $this->text_node_classification ) {
					// Parse error: ignore the token.
					return $this->step();
				}

				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A comment token
			 */
			case '#comment':
			case '#funky-comment':
			case '#presumptuous-tag':
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A DOCTYPE token
			 */
			case 'html':
				// Parse error: ignore the token.
				return $this->step();

			/*
			 * > A start tag whose tag name is "html"
			 */
			case '+HTML':
				return $this->step_in_body();

			/*
			 * > A start tag whose tag name is "option"
			 */
			case '+OPTION':
				if ( $this->state->stack_of_open_elements->current_node_is( 'OPTION' ) ) {
					$this->state->stack_of_open_elements->pop();
				}
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A start tag whose tag name is "optgroup"
			 * > A start tag whose tag name is "hr"
			 *
			 * These rules are identical except for the treatment of the self-closing flag and
			 * the subsequent pop of the HR void element, all of which is handled elsewhere in the processor.
			 */
			case '+OPTGROUP':
			case '+HR':
				if ( $this->state->stack_of_open_elements->current_node_is( 'OPTION' ) ) {
					$this->state->stack_of_open_elements->pop();
				}

				if ( $this->state->stack_of_open_elements->current_node_is( 'OPTGROUP' ) ) {
					$this->state->stack_of_open_elements->pop();
				}

				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > An end tag whose tag name is "optgroup"
			 */
			case '-OPTGROUP':
				$current_node = $this->state->stack_of_open_elements->current_node();
				if ( $current_node && 'OPTION' === $current_node->node_name ) {
					foreach ( $this->state->stack_of_open_elements->walk_up( $current_node ) as $parent ) {
						break;
					}
					if ( $parent && 'OPTGROUP' === $parent->node_name ) {
						$this->state->stack_of_open_elements->pop();
					}
				}

				if ( $this->state->stack_of_open_elements->current_node_is( 'OPTGROUP' ) ) {
					$this->state->stack_of_open_elements->pop();
					return true;
				}

				// Parse error: ignore the token.
				return $this->step();

			/*
			 * > An end tag whose tag name is "option"
			 */
			case '-OPTION':
				if ( $this->state->stack_of_open_elements->current_node_is( 'OPTION' ) ) {
					$this->state->stack_of_open_elements->pop();
					return true;
				}

				// Parse error: ignore the token.
				return $this->step();

			/*
			 * > An end tag whose tag name is "select"
			 * > A start tag whose tag name is "select"
			 *
			 * > It just gets treated like an end tag.
			 */
			case '-SELECT':
			case '+SELECT':
				if ( ! $this->state->stack_of_open_elements->has_element_in_select_scope( 'SELECT' ) ) {
					// Parse error: ignore the token.
					return $this->step();
				}
				$this->state->stack_of_open_elements->pop_until( 'SELECT' );
				$this->reset_insertion_mode_appropriately();
				return true;

			/*
			 * > A start tag whose tag name is one of: "input", "keygen", "textarea"
			 *
			 * All three of these tags are considered a parse error when found in this insertion mode.
			 */
			case '+INPUT':
			case '+KEYGEN':
			case '+TEXTAREA':
				if ( ! $this->state->stack_of_open_elements->has_element_in_select_scope( 'SELECT' ) ) {
					// Ignore the token.
					return $this->step();
				}
				$this->state->stack_of_open_elements->pop_until( 'SELECT' );
				$this->reset_insertion_mode_appropriately();
				return $this->step( self::REPROCESS_CURRENT_NODE );

			/*
			 * > A start tag whose tag name is one of: "script", "template"
			 * > An end tag whose tag name is "template"
			 */
			case '+SCRIPT':
			case '+TEMPLATE':
			case '-TEMPLATE':
				return $this->step_in_head();
		}

		/*
		 * > Anything else
		 * >   Parse error: ignore the token.
		 */
		return $this->step();
	}

	/**
	 * Parses next element in the 'in select in table' insertion mode.
	 *
	 * This internal function performs the 'in select in table' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#parsing-main-inselectintable
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_in_select_in_table(): bool {
		$token_name = $this->get_token_name();
		$token_type = $this->get_token_type();
		$op_sigil   = '#tag' === $token_type ? ( parent::is_tag_closer() ? '-' : '+' ) : '';
		$op         = "{$op_sigil}{$token_name}";

		switch ( $op ) {
			/*
			 * > A start tag whose tag name is one of: "caption", "table", "tbody", "tfoot", "thead", "tr", "td", "th"
			 */
			case '+CAPTION':
			case '+TABLE':
			case '+TBODY':
			case '+TFOOT':
			case '+THEAD':
			case '+TR':
			case '+TD':
			case '+TH':
				// @todo Indicate a parse error once it's possible.
				$this->state->stack_of_open_elements->pop_until( 'SELECT' );
				$this->reset_insertion_mode_appropriately();
				return $this->step( self::REPROCESS_CURRENT_NODE );

			/*
			 * > An end tag whose tag name is one of: "caption", "table", "tbody", "tfoot", "thead", "tr", "td", "th"
			 */
			case '-CAPTION':
			case '-TABLE':
			case '-TBODY':
			case '-TFOOT':
			case '-THEAD':
			case '-TR':
			case '-TD':
			case '-TH':
				// @todo Indicate a parse error once it's possible.
				if ( ! $this->state->stack_of_open_elements->has_element_in_table_scope( $token_name ) ) {
					return $this->step();
				}
				$this->state->stack_of_open_elements->pop_until( 'SELECT' );
				$this->reset_insertion_mode_appropriately();
				return $this->step( self::REPROCESS_CURRENT_NODE );
		}

		/*
		 * > Anything else
		 */
		return $this->step_in_select();
	}

	/**
	 * Parses next element in the 'in template' insertion mode.
	 *
	 * This internal function performs the 'in template' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0 Stub implementation.
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#parsing-main-intemplate
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_in_template(): bool {
		$token_name = $this->get_token_name();
		$token_type = $this->get_token_type();
		$is_closer  = $this->is_tag_closer();
		$op_sigil   = '#tag' === $token_type ? ( $is_closer ? '-' : '+' ) : '';
		$op         = "{$op_sigil}{$token_name}";

		switch ( $op ) {
			/*
			 * > A character token
			 * > A comment token
			 * > A DOCTYPE token
			 */
			case '#text':
			case '#comment':
			case '#funky-comment':
			case '#presumptuous-tag':
			case 'html':
				return $this->step_in_body();

			/*
			 * > A start tag whose tag name is one of: "base", "basefont", "bgsound", "link",
			 * > "meta", "noframes", "script", "style", "template", "title"
			 * > An end tag whose tag name is "template"
			 */
			case '+BASE':
			case '+BASEFONT':
			case '+BGSOUND':
			case '+LINK':
			case '+META':
			case '+NOFRAMES':
			case '+SCRIPT':
			case '+STYLE':
			case '+TEMPLATE':
			case '+TITLE':
			case '-TEMPLATE':
				return $this->step_in_head();

			/*
			 * > A start tag whose tag name is one of: "caption", "colgroup", "tbody", "tfoot", "thead"
			 */
			case '+CAPTION':
			case '+COLGROUP':
			case '+TBODY':
			case '+TFOOT':
			case '+THEAD':
				array_pop( $this->state->stack_of_template_insertion_modes );
				$this->state->stack_of_template_insertion_modes[] = WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE;
				$this->state->insertion_mode                      = WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE;
				return $this->step( self::REPROCESS_CURRENT_NODE );

			/*
			 * > A start tag whose tag name is "col"
			 */
			case '+COL':
				array_pop( $this->state->stack_of_template_insertion_modes );
				$this->state->stack_of_template_insertion_modes[] = WP_HTML_Processor_State::INSERTION_MODE_IN_COLUMN_GROUP;
				$this->state->insertion_mode                      = WP_HTML_Processor_State::INSERTION_MODE_IN_COLUMN_GROUP;
				return $this->step( self::REPROCESS_CURRENT_NODE );

			/*
			 * > A start tag whose tag name is "tr"
			 */
			case '+TR':
				array_pop( $this->state->stack_of_template_insertion_modes );
				$this->state->stack_of_template_insertion_modes[] = WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE_BODY;
				$this->state->insertion_mode                      = WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE_BODY;
				return $this->step( self::REPROCESS_CURRENT_NODE );

			/*
			 * > A start tag whose tag name is one of: "td", "th"
			 */
			case '+TD':
			case '+TH':
				array_pop( $this->state->stack_of_template_insertion_modes );
				$this->state->stack_of_template_insertion_modes[] = WP_HTML_Processor_State::INSERTION_MODE_IN_ROW;
				$this->state->insertion_mode                      = WP_HTML_Processor_State::INSERTION_MODE_IN_ROW;
				return $this->step( self::REPROCESS_CURRENT_NODE );
		}

		/*
		 * > Any other start tag
		 */
		if ( ! $is_closer ) {
			array_pop( $this->state->stack_of_template_insertion_modes );
			$this->state->stack_of_template_insertion_modes[] = WP_HTML_Processor_State::INSERTION_MODE_IN_BODY;
			$this->state->insertion_mode                      = WP_HTML_Processor_State::INSERTION_MODE_IN_BODY;
			return $this->step( self::REPROCESS_CURRENT_NODE );
		}

		/*
		 * > Any other end tag
		 */
		if ( $is_closer ) {
			// Parse error: ignore the token.
			return $this->step();
		}

		/*
		 * > An end-of-file token
		 */
		if ( ! $this->state->stack_of_open_elements->contains( 'TEMPLATE' ) ) {
			// Stop parsing.
			return false;
		}

		// @todo Indicate a parse error once it's possible.
		$this->state->stack_of_open_elements->pop_until( 'TEMPLATE' );
		$this->state->active_formatting_elements->clear_up_to_last_marker();
		array_pop( $this->state->stack_of_template_insertion_modes );
		$this->reset_insertion_mode_appropriately();
		return $this->step( self::REPROCESS_CURRENT_NODE );
	}

	/**
	 * Parses next element in the 'after body' insertion mode.
	 *
	 * This internal function performs the 'after body' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0 Stub implementation.
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#parsing-main-afterbody
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_after_body(): bool {
		$tag_name   = $this->get_token_name();
		$token_type = $this->get_token_type();
		$op_sigil   = '#tag' === $token_type ? ( $this->is_tag_closer() ? '-' : '+' ) : '';
		$op         = "{$op_sigil}{$tag_name}";

		switch ( $op ) {
			/*
			 * > A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF),
			 * >   U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), or U+0020 SPACE
			 *
			 * > Process the token using the rules for the "in body" insertion mode.
			 */
			case '#text':
				if ( parent::TEXT_IS_WHITESPACE === $this->text_node_classification ) {
					return $this->step_in_body();
				}
				goto after_body_anything_else;
				break;

			/*
			 * > A comment token
			 */
			case '#comment':
			case '#funky-comment':
			case '#presumptuous-tag':
				$this->bail( 'Content outside of BODY is unsupported.' );
				break;

			/*
			 * > A DOCTYPE token
			 */
			case 'html':
				// Parse error: ignore the token.
				return $this->step();

			/*
			 * > A start tag whose tag name is "html"
			 */
			case '+HTML':
				return $this->step_in_body();

			/*
			 * > An end tag whose tag name is "html"
			 *
			 * > If the parser was created as part of the HTML fragment parsing algorithm,
			 * > this is a parse error; ignore the token. (fragment case)
			 * >
			 * > Otherwise, switch the insertion mode to "after after body".
			 */
			case '-HTML':
				if ( isset( $this->context_node ) ) {
					return $this->step();
				}

				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_AFTER_AFTER_BODY;
				return true;
		}

		/*
		 * > Parse error. Switch the insertion mode to "in body" and reprocess the token.
		 */
		after_body_anything_else:
		$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_BODY;
		return $this->step( self::REPROCESS_CURRENT_NODE );
	}

	/**
	 * Parses next element in the 'in frameset' insertion mode.
	 *
	 * This internal function performs the 'in frameset' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0 Stub implementation.
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#parsing-main-inframeset
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_in_frameset(): bool {
		$tag_name   = $this->get_token_name();
		$token_type = $this->get_token_type();
		$op_sigil   = '#tag' === $token_type ? ( $this->is_tag_closer() ? '-' : '+' ) : '';
		$op         = "{$op_sigil}{$tag_name}";

		switch ( $op ) {
			/*
			 * > A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF),
			 * >   U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), or U+0020 SPACE
			 * >
			 * > Insert the character.
			 *
			 * This algorithm effectively strips non-whitespace characters from text and inserts
			 * them under HTML. This is not supported at this time.
			 */
			case '#text':
				if ( parent::TEXT_IS_WHITESPACE === $this->text_node_classification ) {
					return $this->step_in_body();
				}
				$this->bail( 'Non-whitespace characters cannot be handled in frameset.' );
				break;

			/*
			 * > A comment token
			 */
			case '#comment':
			case '#funky-comment':
			case '#presumptuous-tag':
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A DOCTYPE token
			 */
			case 'html':
				// Parse error: ignore the token.
				return $this->step();

			/*
			 * > A start tag whose tag name is "html"
			 */
			case '+HTML':
				return $this->step_in_body();

			/*
			 * > A start tag whose tag name is "frameset"
			 */
			case '+FRAMESET':
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > An end tag whose tag name is "frameset"
			 */
			case '-FRAMESET':
				/*
				 * > If the current node is the root html element, then this is a parse error;
				 * > ignore the token. (fragment case)
				 */
				if ( $this->state->stack_of_open_elements->current_node_is( 'HTML' ) ) {
					return $this->step();
				}

				/*
				 * > Otherwise, pop the current node from the stack of open elements.
				 */
				$this->state->stack_of_open_elements->pop();

				/*
				 * > If the parser was not created as part of the HTML fragment parsing algorithm
				 * > (fragment case), and the current node is no longer a frameset element, then
				 * > switch the insertion mode to "after frameset".
				 */
				if ( ! isset( $this->context_node ) && ! $this->state->stack_of_open_elements->current_node_is( 'FRAMESET' ) ) {
					$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_AFTER_FRAMESET;
				}

				return true;

			/*
			 * > A start tag whose tag name is "frame"
			 *
			 * > Insert an HTML element for the token. Immediately pop the
			 * > current node off the stack of open elements.
			 * >
			 * > Acknowledge the token's self-closing flag, if it is set.
			 */
			case '+FRAME':
				$this->insert_html_element( $this->state->current_token );
				$this->state->stack_of_open_elements->pop();
				return true;

			/*
			 * > A start tag whose tag name is "noframes"
			 */
			case '+NOFRAMES':
				return $this->step_in_head();
		}

		// Parse error: ignore the token.
		return $this->step();
	}

	/**
	 * Parses next element in the 'after frameset' insertion mode.
	 *
	 * This internal function performs the 'after frameset' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0 Stub implementation.
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#parsing-main-afterframeset
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_after_frameset(): bool {
		$tag_name   = $this->get_token_name();
		$token_type = $this->get_token_type();
		$op_sigil   = '#tag' === $token_type ? ( $this->is_tag_closer() ? '-' : '+' ) : '';
		$op         = "{$op_sigil}{$tag_name}";

		switch ( $op ) {
			/*
			 * > A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF),
			 * >   U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), or U+0020 SPACE
			 * >
			 * > Insert the character.
			 *
			 * This algorithm effectively strips non-whitespace characters from text and inserts
			 * them under HTML. This is not supported at this time.
			 */
			case '#text':
				if ( parent::TEXT_IS_WHITESPACE === $this->text_node_classification ) {
					return $this->step_in_body();
				}
				$this->bail( 'Non-whitespace characters cannot be handled in after frameset' );
				break;

			/*
			 * > A comment token
			 */
			case '#comment':
			case '#funky-comment':
			case '#presumptuous-tag':
				$this->insert_html_element( $this->state->current_token );
				return true;

			/*
			 * > A DOCTYPE token
			 */
			case 'html':
				// Parse error: ignore the token.
				return $this->step();

			/*
			 * > A start tag whose tag name is "html"
			 */
			case '+HTML':
				return $this->step_in_body();

			/*
			 * > An end tag whose tag name is "html"
			 */
			case '-HTML':
				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_AFTER_AFTER_FRAMESET;
				return true;

			/*
			 * > A start tag whose tag name is "noframes"
			 */
			case '+NOFRAMES':
				return $this->step_in_head();
		}

		// Parse error: ignore the token.
		return $this->step();
	}

	/**
	 * Parses next element in the 'after after body' insertion mode.
	 *
	 * This internal function performs the 'after after body' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0 Stub implementation.
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#the-after-after-body-insertion-mode
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_after_after_body(): bool {
		$tag_name   = $this->get_token_name();
		$token_type = $this->get_token_type();
		$op_sigil   = '#tag' === $token_type ? ( $this->is_tag_closer() ? '-' : '+' ) : '';
		$op         = "{$op_sigil}{$tag_name}";

		switch ( $op ) {
			/*
			 * > A comment token
			 */
			case '#comment':
			case '#funky-comment':
			case '#presumptuous-tag':
				$this->bail( 'Content outside of HTML is unsupported.' );
				break;

			/*
			 * > A DOCTYPE token
			 * > A start tag whose tag name is "html"
			 *
			 * > Process the token using the rules for the "in body" insertion mode.
			 */
			case 'html':
			case '+HTML':
				return $this->step_in_body();

			/*
			 * > A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF),
			 * >   U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), or U+0020 SPACE
			 * >
			 * > Process the token using the rules for the "in body" insertion mode.
			 */
			case '#text':
				if ( parent::TEXT_IS_WHITESPACE === $this->text_node_classification ) {
					return $this->step_in_body();
				}
				goto after_after_body_anything_else;
				break;
		}

		/*
		 * > Parse error. Switch the insertion mode to "in body" and reprocess the token.
		 */
		after_after_body_anything_else:
		$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_BODY;
		return $this->step( self::REPROCESS_CURRENT_NODE );
	}

	/**
	 * Parses next element in the 'after after frameset' insertion mode.
	 *
	 * This internal function performs the 'after after frameset' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0 Stub implementation.
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#the-after-after-frameset-insertion-mode
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_after_after_frameset(): bool {
		$tag_name   = $this->get_token_name();
		$token_type = $this->get_token_type();
		$op_sigil   = '#tag' === $token_type ? ( $this->is_tag_closer() ? '-' : '+' ) : '';
		$op         = "{$op_sigil}{$tag_name}";

		switch ( $op ) {
			/*
			 * > A comment token
			 */
			case '#comment':
			case '#funky-comment':
			case '#presumptuous-tag':
				$this->bail( 'Content outside of HTML is unsupported.' );
				break;

			/*
			 * > A DOCTYPE token
			 * > A start tag whose tag name is "html"
			 *
			 * > Process the token using the rules for the "in body" insertion mode.
			 */
			case 'html':
			case '+HTML':
				return $this->step_in_body();

			/*
			 * > A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF),
			 * >   U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), or U+0020 SPACE
			 * >
			 * > Process the token using the rules for the "in body" insertion mode.
			 *
			 * This algorithm effectively strips non-whitespace characters from text and inserts
			 * them under HTML. This is not supported at this time.
			 */
			case '#text':
				if ( parent::TEXT_IS_WHITESPACE === $this->text_node_classification ) {
					return $this->step_in_body();
				}
				$this->bail( 'Non-whitespace characters cannot be handled in after after frameset.' );
				break;

			/*
			 * > A start tag whose tag name is "noframes"
			 */
			case '+NOFRAMES':
				return $this->step_in_head();
		}

		// Parse error: ignore the token.
		return $this->step();
	}

	/**
	 * Parses next element in the 'in foreign content' insertion mode.
	 *
	 * This internal function performs the 'in foreign content' insertion mode
	 * logic for the generalized WP_HTML_Processor::step() function.
	 *
	 * @since 6.7.0 Stub implementation.
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#parsing-main-inforeign
	 * @see WP_HTML_Processor::step
	 *
	 * @return bool Whether an element was found.
	 */
	private function step_in_foreign_content(): bool {
		$tag_name   = $this->get_token_name();
		$token_type = $this->get_token_type();
		$op_sigil   = '#tag' === $token_type ? ( $this->is_tag_closer() ? '-' : '+' ) : '';
		$op         = "{$op_sigil}{$tag_name}";

		/*
		 * > A start tag whose name is "font", if the token has any attributes named "color", "face", or "size"
		 *
		 * This section drawn out above the switch to more easily incorporate
		 * the additional rules based on the presence of the attributes.
		 */
		if (
			'+FONT' === $op &&
			(
				null !== $this->get_attribute( 'color' ) ||
				null !== $this->get_attribute( 'face' ) ||
				null !== $this->get_attribute( 'size' )
			)
		) {
			$op = '+FONT with attributes';
		}

		switch ( $op ) {
			case '#text':
				/*
				 * > A character token that is U+0000 NULL
				 *
				 * This is handled by `get_modifiable_text()`.
				 */

				/*
				 * Whitespace-only text does not affect the frameset-ok flag.
				 * It is probably inter-element whitespace, but it may also
				 * contain character references which decode only to whitespace.
				 */
				if ( parent::TEXT_IS_GENERIC === $this->text_node_classification ) {
					$this->state->frameset_ok = false;
				}

				$this->insert_foreign_element( $this->state->current_token, false );
				return true;

			/*
			 * CDATA sections are alternate wrappers for text content and therefore
			 * ought to follow the same rules as text nodes.
			 */
			case '#cdata-section':
				/*
				 * NULL bytes and whitespace do not change the frameset-ok flag.
				 */
				$current_token        = $this->bookmarks[ $this->state->current_token->bookmark_name ];
				$cdata_content_start  = $current_token->start + 9;
				$cdata_content_length = $current_token->length - 12;
				if ( strspn( $this->html, "\0 \t\n\f\r", $cdata_content_start, $cdata_content_length ) !== $cdata_content_length ) {
					$this->state->frameset_ok = false;
				}

				$this->insert_foreign_element( $this->state->current_token, false );
				return true;

			/*
			 * > A comment token
			 */
			case '#comment':
			case '#funky-comment':
			case '#presumptuous-tag':
				$this->insert_foreign_element( $this->state->current_token, false );
				return true;

			/*
			 * > A DOCTYPE token
			 */
			case 'html':
				// Parse error: ignore the token.
				return $this->step();

			/*
			 * > A start tag whose tag name is "b", "big", "blockquote", "body", "br", "center",
			 * > "code", "dd", "div", "dl", "dt", "em", "embed", "h1", "h2", "h3", "h4", "h5",
			 * > "h6", "head", "hr", "i", "img", "li", "listing", "menu", "meta", "nobr", "ol",
			 * > "p", "pre", "ruby", "s", "small", "span", "strong", "strike", "sub", "sup",
			 * > "table", "tt", "u", "ul", "var"
			 *
			 * > A start tag whose name is "font", if the token has any attributes named "color", "face", or "size"
			 *
			 * > An end tag whose tag name is "br", "p"
			 *
			 * Closing BR tags are always reported by the Tag Processor as opening tags.
			 */
			case '+B':
			case '+BIG':
			case '+BLOCKQUOTE':
			case '+BODY':
			case '+BR':
			case '+CENTER':
			case '+CODE':
			case '+DD':
			case '+DIV':
			case '+DL':
			case '+DT':
			case '+EM':
			case '+EMBED':
			case '+H1':
			case '+H2':
			case '+H3':
			case '+H4':
			case '+H5':
			case '+H6':
			case '+HEAD':
			case '+HR':
			case '+I':
			case '+IMG':
			case '+LI':
			case '+LISTING':
			case '+MENU':
			case '+META':
			case '+NOBR':
			case '+OL':
			case '+P':
			case '+PRE':
			case '+RUBY':
			case '+S':
			case '+SMALL':
			case '+SPAN':
			case '+STRONG':
			case '+STRIKE':
			case '+SUB':
			case '+SUP':
			case '+TABLE':
			case '+TT':
			case '+U':
			case '+UL':
			case '+VAR':
			case '+FONT with attributes':
			case '-BR':
			case '-P':
				// @todo Indicate a parse error once it's possible.
				foreach ( $this->state->stack_of_open_elements->walk_up() as $current_node ) {
					if (
						'math' === $current_node->integration_node_type ||
						'html' === $current_node->integration_node_type ||
						'html' === $current_node->namespace
					) {
						break;
					}

					$this->state->stack_of_open_elements->pop();
				}
				goto in_foreign_content_process_in_current_insertion_mode;
		}

		/*
		 * > Any other start tag
		 */
		if ( ! $this->is_tag_closer() ) {
			$this->insert_foreign_element( $this->state->current_token, false );

			/*
			 * > If the token has its self-closing flag set, then run
			 * > the appropriate steps from the following list:
			 * >
			 * >   ↪ the token's tag name is "script", and the new current node is in the SVG namespace
			 * >         Acknowledge the token's self-closing flag, and then act as
			 * >         described in the steps for a "script" end tag below.
			 * >
			 * >   ↪ Otherwise
			 * >         Pop the current node off the stack of open elements and
			 * >         acknowledge the token's self-closing flag.
			 *
			 * Since the rules for SCRIPT below indicate to pop the element off of the stack of
			 * open elements, which is the same for the Otherwise condition, there's no need to
			 * separate these checks. The difference comes when a parser operates with the scripting
			 * flag enabled, and executes the script, which this parser does not support.
			 */
			if ( $this->state->current_token->has_self_closing_flag ) {
				$this->state->stack_of_open_elements->pop();
			}
			return true;
		}

		/*
		 * > An end tag whose name is "script", if the current node is an SVG script element.
		 */
		if ( $this->is_tag_closer() && 'SCRIPT' === $this->state->current_token->node_name && 'svg' === $this->state->current_token->namespace ) {
			$this->state->stack_of_open_elements->pop();
			return true;
		}

		/*
		 * > Any other end tag
		 */
		if ( $this->is_tag_closer() ) {
			$node = $this->state->stack_of_open_elements->current_node();
			if ( $tag_name !== $node->node_name ) {
				// @todo Indicate a parse error once it's possible.
			}
			in_foreign_content_end_tag_loop:
			if ( $node === $this->state->stack_of_open_elements->at( 1 ) ) {
				return true;
			}

			/*
			 * > If node's tag name, converted to ASCII lowercase, is the same as the tag name
			 * > of the token, pop elements from the stack of open elements until node has
			 * > been popped from the stack, and then return.
			 */
			if ( 0 === strcasecmp( $node->node_name, $tag_name ) ) {
				foreach ( $this->state->stack_of_open_elements->walk_up() as $item ) {
					$this->state->stack_of_open_elements->pop();
					if ( $node === $item ) {
						return true;
					}
				}
			}

			foreach ( $this->state->stack_of_open_elements->walk_up( $node ) as $item ) {
				$node = $item;
				break;
			}

			if ( 'html' !== $node->namespace ) {
				goto in_foreign_content_end_tag_loop;
			}

			in_foreign_content_process_in_current_insertion_mode:
			switch ( $this->state->insertion_mode ) {
				case WP_HTML_Processor_State::INSERTION_MODE_INITIAL:
					return $this->step_initial();

				case WP_HTML_Processor_State::INSERTION_MODE_BEFORE_HTML:
					return $this->step_before_html();

				case WP_HTML_Processor_State::INSERTION_MODE_BEFORE_HEAD:
					return $this->step_before_head();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_HEAD:
					return $this->step_in_head();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_HEAD_NOSCRIPT:
					return $this->step_in_head_noscript();

				case WP_HTML_Processor_State::INSERTION_MODE_AFTER_HEAD:
					return $this->step_after_head();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_BODY:
					return $this->step_in_body();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE:
					return $this->step_in_table();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE_TEXT:
					return $this->step_in_table_text();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_CAPTION:
					return $this->step_in_caption();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_COLUMN_GROUP:
					return $this->step_in_column_group();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE_BODY:
					return $this->step_in_table_body();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_ROW:
					return $this->step_in_row();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_CELL:
					return $this->step_in_cell();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_SELECT:
					return $this->step_in_select();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_SELECT_IN_TABLE:
					return $this->step_in_select_in_table();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_TEMPLATE:
					return $this->step_in_template();

				case WP_HTML_Processor_State::INSERTION_MODE_AFTER_BODY:
					return $this->step_after_body();

				case WP_HTML_Processor_State::INSERTION_MODE_IN_FRAMESET:
					return $this->step_in_frameset();

				case WP_HTML_Processor_State::INSERTION_MODE_AFTER_FRAMESET:
					return $this->step_after_frameset();

				case WP_HTML_Processor_State::INSERTION_MODE_AFTER_AFTER_BODY:
					return $this->step_after_after_body();

				case WP_HTML_Processor_State::INSERTION_MODE_AFTER_AFTER_FRAMESET:
					return $this->step_after_after_frameset();

				// This should be unreachable but PHP doesn't have total type checking on switch.
				default:
					$this->bail( "Unaware of the requested parsing mode: '{$this->state->insertion_mode}'." );
			}
		}

		$this->bail( 'Should not have been able to reach end of IN FOREIGN CONTENT processing. Check HTML API code.' );
		// This unnecessary return prevents tools from inaccurately reporting type errors.
		return false;
	}

	/*
	 * Internal helpers
	 */

	/**
	 * Creates a new bookmark for the currently-matched token and returns the generated name.
	 *
	 * @since 6.4.0
	 * @since 6.5.0 Renamed from bookmark_tag() to bookmark_token().
	 *
	 * @throws Exception When unable to allocate requested bookmark.
	 *
	 * @return string|false Name of created bookmark, or false if unable to create.
	 */
	private function bookmark_token() {
		if ( ! parent::set_bookmark( ++$this->bookmark_counter ) ) {
			$this->last_error = self::ERROR_EXCEEDED_MAX_BOOKMARKS;
			throw new Exception( 'could not allocate bookmark' );
		}

		return "{$this->bookmark_counter}";
	}

	/*
	 * HTML semantic overrides for Tag Processor
	 */

	/**
	 * Indicates the namespace of the current token, or "html" if there is none.
	 *
	 * @return string One of "html", "math", or "svg".
	 */
	public function get_namespace(): string {
		if ( ! isset( $this->current_element ) ) {
			return parent::get_namespace();
		}

		return $this->current_element->token->namespace;
	}

	/**
	 * Returns the uppercase name of the matched tag.
	 *
	 * The semantic rules for HTML specify that certain tags be reprocessed
	 * with a different tag name. Because of this, the tag name presented
	 * by the HTML Processor may differ from the one reported by the HTML
	 * Tag Processor, which doesn't apply these semantic rules.
	 *
	 * Example:
	 *
	 *     $processor = new WP_HTML_Tag_Processor( '<div class="test">Test</div>' );
	 *     $processor->next_tag() === true;
	 *     $processor->get_tag() === 'DIV';
	 *
	 *     $processor->next_tag() === false;
	 *     $processor->get_tag() === null;
	 *
	 * @since 6.4.0
	 *
	 * @return string|null Name of currently matched tag in input HTML, or `null` if none found.
	 */
	public function get_tag(): ?string {
		if ( null !== $this->last_error ) {
			return null;
		}

		if ( $this->is_virtual() ) {
			return $this->current_element->token->node_name;
		}

		$tag_name = parent::get_tag();

		/*
		 * > A start tag whose tag name is "image"
		 * > Change the token's tag name to "img" and reprocess it. (Don't ask.)
		 */
		return ( 'IMAGE' === $tag_name && 'html' === $this->get_namespace() )
			? 'IMG'
			: $tag_name;
	}

	/**
	 * Indicates if the currently matched tag contains the self-closing flag.
	 *
	 * No HTML elements ought to have the self-closing flag and for those, the self-closing
	 * flag will be ignored. For void elements this is benign because they "self close"
	 * automatically. For non-void HTML elements though problems will appear if someone
	 * intends to use a self-closing element in place of that element with an empty body.
	 * For HTML foreign elements and custom elements the self-closing flag determines if
	 * they self-close or not.
	 *
	 * This function does not determine if a tag is self-closing,
	 * but only if the self-closing flag is present in the syntax.
	 *
	 * @since 6.6.0 Subclassed for the HTML Processor.
	 *
	 * @return bool Whether the currently matched tag contains the self-closing flag.
	 */
	public function has_self_closing_flag(): bool {
		return $this->is_virtual() ? false : parent::has_self_closing_flag();
	}

	/**
	 * Returns the node name represented by the token.
	 *
	 * This matches the DOM API value `nodeName`. Some values
	 * are static, such as `#text` for a text node, while others
	 * are dynamically generated from the token itself.
	 *
	 * Dynamic names:
	 *  - Uppercase tag name for tag matches.
	 *  - `html` for DOCTYPE declarations.
	 *
	 * Note that if the Tag Processor is not matched on a token
	 * then this function will return `null`, either because it
	 * hasn't yet found a token or because it reached the end
	 * of the document without matching a token.
	 *
	 * @since 6.6.0 Subclassed for the HTML Processor.
	 *
	 * @return string|null Name of the matched token.
	 */
	public function get_token_name(): ?string {
		return $this->is_virtual()
			? $this->current_element->token->node_name
			: parent::get_token_name();
	}

	/**
	 * Indicates the kind of matched token, if any.
	 *
	 * This differs from `get_token_name()` in that it always
	 * returns a static string indicating the type, whereas
	 * `get_token_name()` may return values derived from the
	 * token itself, such as a tag name or processing
	 * instruction tag.
	 *
	 * Possible values:
	 *  - `#tag` when matched on a tag.
	 *  - `#text` when matched on a text node.
	 *  - `#cdata-section` when matched on a CDATA node.
	 *  - `#comment` when matched on a comment.
	 *  - `#doctype` when matched on a DOCTYPE declaration.
	 *  - `#presumptuous-tag` when matched on an empty tag closer.
	 *  - `#funky-comment` when matched on a funky comment.
	 *
	 * @since 6.6.0 Subclassed for the HTML Processor.
	 *
	 * @return string|null What kind of token is matched, or null.
	 */
	public function get_token_type(): ?string {
		if ( $this->is_virtual() ) {
			/*
			 * This logic comes from the Tag Processor.
			 *
			 * @todo It would be ideal not to repeat this here, but it's not clearly
			 *       better to allow passing a token name to `get_token_type()`.
			 */
			$node_name     = $this->current_element->token->node_name;
			$starting_char = $node_name[0];
			if ( 'A' <= $starting_char && 'Z' >= $starting_char ) {
				return '#tag';
			}

			if ( 'html' === $node_name ) {
				return '#doctype';
			}

			return $node_name;
		}

		return parent::get_token_type();
	}

	/**
	 * Returns the value of a requested attribute from a matched tag opener if that attribute exists.
	 *
	 * Example:
	 *
	 *     $p = WP_HTML_Processor::create_fragment( '<div enabled class="test" data-test-id="14">Test</div>' );
	 *     $p->next_token() === true;
	 *     $p->get_attribute( 'data-test-id' ) === '14';
	 *     $p->get_attribute( 'enabled' ) === true;
	 *     $p->get_attribute( 'aria-label' ) === null;
	 *
	 *     $p->next_tag() === false;
	 *     $p->get_attribute( 'class' ) === null;
	 *
	 * @since 6.6.0 Subclassed for HTML Processor.
	 *
	 * @param string $name Name of attribute whose value is requested.
	 * @return string|true|null Value of attribute or `null` if not available. Boolean attributes return `true`.
	 */
	public function get_attribute( $name ) {
		return $this->is_virtual() ? null : parent::get_attribute( $name );
	}

	/**
	 * Updates or creates a new attribute on the currently matched tag with the passed value.
	 *
	 * For boolean attributes special handling is provided:
	 *  - When `true` is passed as the value, then only the attribute name is added to the tag.
	 *  - When `false` is passed, the attribute gets removed if it existed before.
	 *
	 * For string attributes, the value is escaped using the `esc_attr` function.
	 *
	 * @since 6.6.0 Subclassed for the HTML Processor.
	 *
	 * @param string      $name  The attribute name to target.
	 * @param string|bool $value The new attribute value.
	 * @return bool Whether an attribute value was set.
	 */
	public function set_attribute( $name, $value ): bool {
		return $this->is_virtual() ? false : parent::set_attribute( $name, $value );
	}

	/**
	 * Remove an attribute from the currently-matched tag.
	 *
	 * @since 6.6.0 Subclassed for HTML Processor.
	 *
	 * @param string $name The attribute name to remove.
	 * @return bool Whether an attribute was removed.
	 */
	public function remove_attribute( $name ): bool {
		return $this->is_virtual() ? false : parent::remove_attribute( $name );
	}

	/**
	 * Gets lowercase names of all attributes matching a given prefix in the current tag.
	 *
	 * Note that matching is case-insensitive. This is in accordance with the spec:
	 *
	 * > There must never be two or more attributes on
	 * > the same start tag whose names are an ASCII
	 * > case-insensitive match for each other.
	 *     - HTML 5 spec
	 *
	 * Example:
	 *
	 *     $p = new WP_HTML_Tag_Processor( '<div data-ENABLED class="test" DATA-test-id="14">Test</div>' );
	 *     $p->next_tag( array( 'class_name' => 'test' ) ) === true;
	 *     $p->get_attribute_names_with_prefix( 'data-' ) === array( 'data-enabled', 'data-test-id' );
	 *
	 *     $p->next_tag() === false;
	 *     $p->get_attribute_names_with_prefix( 'data-' ) === null;
	 *
	 * @since 6.6.0 Subclassed for the HTML Processor.
	 *
	 * @see https://html.spec.whatwg.org/multipage/syntax.html#attributes-2:ascii-case-insensitive
	 *
	 * @param string $prefix Prefix of requested attribute names.
	 * @return array|null List of attribute names, or `null` when no tag opener is matched.
	 */
	public function get_attribute_names_with_prefix( $prefix ): ?array {
		return $this->is_virtual() ? null : parent::get_attribute_names_with_prefix( $prefix );
	}

	/**
	 * Adds a new class name to the currently matched tag.
	 *
	 * @since 6.6.0 Subclassed for the HTML Processor.
	 *
	 * @param string $class_name The class name to add.
	 * @return bool Whether the class was set to be added.
	 */
	public function add_class( $class_name ): bool {
		return $this->is_virtual() ? false : parent::add_class( $class_name );
	}

	/**
	 * Removes a class name from the currently matched tag.
	 *
	 * @since 6.6.0 Subclassed for the HTML Processor.
	 *
	 * @param string $class_name The class name to remove.
	 * @return bool Whether the class was set to be removed.
	 */
	public function remove_class( $class_name ): bool {
		return $this->is_virtual() ? false : parent::remove_class( $class_name );
	}

	/**
	 * Returns if a matched tag contains the given ASCII case-insensitive class name.
	 *
	 * @since 6.6.0 Subclassed for the HTML Processor.
	 *
	 * @todo When reconstructing active formatting elements with attributes, find a way
	 *       to indicate if the virtually-reconstructed formatting elements contain the
	 *       wanted class name.
	 *
	 * @param string $wanted_class Look for this CSS class name, ASCII case-insensitive.
	 * @return bool|null Whether the matched tag contains the given class name, or null if not matched.
	 */
	public function has_class( $wanted_class ): ?bool {
		return $this->is_virtual() ? null : parent::has_class( $wanted_class );
	}

	/**
	 * Generator for a foreach loop to step through each class name for the matched tag.
	 *
	 * This generator function is designed to be used inside a "foreach" loop.
	 *
	 * Example:
	 *
	 *     $p = WP_HTML_Processor::create_fragment( "<div class='free &lt;egg&lt;\tlang-en'>" );
	 *     $p->next_tag();
	 *     foreach ( $p->class_list() as $class_name ) {
	 *         echo "{$class_name} ";
	 *     }
	 *     // Outputs: "free <egg> lang-en "
	 *
	 * @since 6.6.0 Subclassed for the HTML Processor.
	 */
	public function class_list() {
		return $this->is_virtual() ? null : parent::class_list();
	}

	/**
	 * Returns the modifiable text for a matched token, or an empty string.
	 *
	 * Modifiable text is text content that may be read and changed without
	 * changing the HTML structure of the document around it. This includes
	 * the contents of `#text` nodes in the HTML as well as the inner
	 * contents of HTML comments, Processing Instructions, and others, even
	 * though these nodes aren't part of a parsed DOM tree. They also contain
	 * the contents of SCRIPT and STYLE tags, of TEXTAREA tags, and of any
	 * other section in an HTML document which cannot contain HTML markup (DATA).
	 *
	 * If a token has no modifiable text then an empty string is returned to
	 * avoid needless crashing or type errors. An empty string does not mean
	 * that a token has modifiable text, and a token with modifiable text may
	 * have an empty string (e.g. a comment with no contents).
	 *
	 * @since 6.6.0 Subclassed for the HTML Processor.
	 *
	 * @return string
	 */
	public function get_modifiable_text(): string {
		return $this->is_virtual() ? '' : parent::get_modifiable_text();
	}

	/**
	 * Indicates what kind of comment produced the comment node.
	 *
	 * Because there are different kinds of HTML syntax which produce
	 * comments, the Tag Processor tracks and exposes this as a type
	 * for the comment. Nominally only regular HTML comments exist as
	 * they are commonly known, but a number of unrelated syntax errors
	 * also produce comments.
	 *
	 * @see self::COMMENT_AS_ABRUPTLY_CLOSED_COMMENT
	 * @see self::COMMENT_AS_CDATA_LOOKALIKE
	 * @see self::COMMENT_AS_INVALID_HTML
	 * @see self::COMMENT_AS_HTML_COMMENT
	 * @see self::COMMENT_AS_PI_NODE_LOOKALIKE
	 *
	 * @since 6.6.0 Subclassed for the HTML Processor.
	 *
	 * @return string|null
	 */
	public function get_comment_type(): ?string {
		return $this->is_virtual() ? null : parent::get_comment_type();
	}

	/**
	 * Removes a bookmark that is no longer needed.
	 *
	 * Releasing a bookmark frees up the small
	 * performance overhead it requires.
	 *
	 * @since 6.4.0
	 *
	 * @param string $bookmark_name Name of the bookmark to remove.
	 * @return bool Whether the bookmark already existed before removal.
	 */
	public function release_bookmark( $bookmark_name ): bool {
		return parent::release_bookmark( "_{$bookmark_name}" );
	}

	/**
	 * Moves the internal cursor in the HTML Processor to a given bookmark's location.
	 *
	 * Be careful! Seeking backwards to a previous location resets the parser to the
	 * start of the document and reparses the entire contents up until it finds the
	 * sought-after bookmarked location.
	 *
	 * In order to prevent accidental infinite loops, there's a
	 * maximum limit on the number of times seek() can be called.
	 *
	 * @throws Exception When unable to allocate a bookmark for the next token in the input HTML document.
	 *
	 * @since 6.4.0
	 *
	 * @param string $bookmark_name Jump to the place in the document identified by this bookmark name.
	 * @return bool Whether the internal cursor was successfully moved to the bookmark's location.
	 */
	public function seek( $bookmark_name ): bool {
		// Flush any pending updates to the document before beginning.
		$this->get_updated_html();

		$actual_bookmark_name = "_{$bookmark_name}";
		$processor_started_at = $this->state->current_token
			? $this->bookmarks[ $this->state->current_token->bookmark_name ]->start
			: 0;
		$bookmark_starts_at   = $this->bookmarks[ $actual_bookmark_name ]->start;
		$direction            = $bookmark_starts_at > $processor_started_at ? 'forward' : 'backward';

		/*
		 * If seeking backwards, it's possible that the sought-after bookmark exists within an element
		 * which has been closed before the current cursor; in other words, it has already been removed
		 * from the stack of open elements. This means that it's insufficient to simply pop off elements
		 * from the stack of open elements which appear after the bookmarked location and then jump to
		 * that location, as the elements which were open before won't be re-opened.
		 *
		 * In order to maintain consistency, the HTML Processor rewinds to the start of the document
		 * and reparses everything until it finds the sought-after bookmark.
		 *
		 * There are potentially better ways to do this: cache the parser state for each bookmark and
		 * restore it when seeking; store an immutable and idempotent register of where elements open
		 * and close.
		 *
		 * If caching the parser state it will be essential to properly maintain the cached stack of
		 * open elements and active formatting elements when modifying the document. This could be a
		 * tedious and time-consuming process as well, and so for now will not be performed.
		 *
		 * It may be possible to track bookmarks for where elements open and close, and in doing so
		 * be able to quickly recalculate breadcrumbs for any element in the document. It may even
		 * be possible to remove the stack of open elements and compute it on the fly this way.
		 * If doing this, the parser would need to track the opening and closing locations for all
		 * tokens in the breadcrumb path for any and all bookmarks. By utilizing bookmarks themselves
		 * this list could be automatically maintained while modifying the document. Finding the
		 * breadcrumbs would then amount to traversing that list from the start until the token
		 * being inspected. Once an element closes, if there are no bookmarks pointing to locations
		 * within that element, then all of these locations may be forgotten to save on memory use
		 * and computation time.
		 */
		if ( 'backward' === $direction ) {
			/*
			 * Instead of clearing the parser state and starting fresh, calling the stack methods
			 * maintains the proper flags in the parser.
			 */
			foreach ( $this->state->stack_of_open_elements->walk_up() as $item ) {
				if ( 'context-node' === $item->bookmark_name ) {
					break;
				}

				$this->state->stack_of_open_elements->remove_node( $item );
			}

			foreach ( $this->state->active_formatting_elements->walk_up() as $item ) {
				if ( 'context-node' === $item->bookmark_name ) {
					break;
				}

				$this->state->active_formatting_elements->remove_node( $item );
			}

			parent::seek( 'context-node' );
			$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_BODY;
			$this->state->frameset_ok    = true;
			$this->element_queue         = array();
			$this->current_element       = null;

			if ( isset( $this->context_node ) ) {
				$this->breadcrumbs = array_slice( $this->breadcrumbs, 0, 2 );
			} else {
				$this->breadcrumbs = array();
			}
		}

		// When moving forwards, reparse the document until reaching the same location as the original bookmark.
		if ( $bookmark_starts_at === $this->bookmarks[ $this->state->current_token->bookmark_name ]->start ) {
			return true;
		}

		while ( $this->next_token() ) {
			if ( $bookmark_starts_at === $this->bookmarks[ $this->state->current_token->bookmark_name ]->start ) {
				while ( isset( $this->current_element ) && WP_HTML_Stack_Event::POP === $this->current_element->operation ) {
					$this->current_element = array_shift( $this->element_queue );
				}
				return true;
			}
		}

		return false;
	}

	/**
	 * Sets a bookmark in the HTML document.
	 *
	 * Bookmarks represent specific places or tokens in the HTML
	 * document, such as a tag opener or closer. When applying
	 * edits to a document, such as setting an attribute, the
	 * text offsets of that token may shift; the bookmark is
	 * kept updated with those shifts and remains stable unless
	 * the entire span of text in which the token sits is removed.
	 *
	 * Release bookmarks when they are no longer needed.
	 *
	 * Example:
	 *
	 *     <main><h2>Surprising fact you may not know!</h2></main>
	 *           ^  ^
	 *            \-|-- this `H2` opener bookmark tracks the token
	 *
	 *     <main class="clickbait"><h2>Surprising fact you may no…
	 *                             ^  ^
	 *                              \-|-- it shifts with edits
	 *
	 * Bookmarks provide the ability to seek to a previously-scanned
	 * place in the HTML document. This avoids the need to re-scan
	 * the entire document.
	 *
	 * Example:
	 *
	 *     <ul><li>One</li><li>Two</li><li>Three</li></ul>
	 *                                 ^^^^
	 *                                 want to note this last item
	 *
	 *     $p = new WP_HTML_Tag_Processor( $html );
	 *     $in_list = false;
	 *     while ( $p->next_tag( array( 'tag_closers' => $in_list ? 'visit' : 'skip' ) ) ) {
	 *         if ( 'UL' === $p->get_tag() ) {
	 *             if ( $p->is_tag_closer() ) {
	 *                 $in_list = false;
	 *                 $p->set_bookmark( 'resume' );
	 *                 if ( $p->seek( 'last-li' ) ) {
	 *                     $p->add_class( 'last-li' );
	 *                 }
	 *                 $p->seek( 'resume' );
	 *                 $p->release_bookmark( 'last-li' );
	 *                 $p->release_bookmark( 'resume' );
	 *             } else {
	 *                 $in_list = true;
	 *             }
	 *         }
	 *
	 *         if ( 'LI' === $p->get_tag() ) {
	 *             $p->set_bookmark( 'last-li' );
	 *         }
	 *     }
	 *
	 * Bookmarks intentionally hide the internal string offsets
	 * to which they refer. They are maintained internally as
	 * updates are applied to the HTML document and therefore
	 * retain their "position" - the location to which they
	 * originally pointed. The inability to use bookmarks with
	 * functions like `substr` is therefore intentional to guard
	 * against accidentally breaking the HTML.
	 *
	 * Because bookmarks allocate memory and require processing
	 * for every applied update, they are limited and require
	 * a name. They should not be created with programmatically-made
	 * names, such as "li_{$index}" with some loop. As a general
	 * rule they should only be created with string-literal names
	 * like "start-of-section" or "last-paragraph".
	 *
	 * Bookmarks are a powerful tool to enable complicated behavior.
	 * Consider double-checking that you need this tool if you are
	 * reaching for it, as inappropriate use could lead to broken
	 * HTML structure or unwanted processing overhead.
	 *
	 * @since 6.4.0
	 *
	 * @param string $bookmark_name Identifies this particular bookmark.
	 * @return bool Whether the bookmark was successfully created.
	 */
	public function set_bookmark( $bookmark_name ): bool {
		return parent::set_bookmark( "_{$bookmark_name}" );
	}

	/**
	 * Checks whether a bookmark with the given name exists.
	 *
	 * @since 6.5.0
	 *
	 * @param string $bookmark_name Name to identify a bookmark that potentially exists.
	 * @return bool Whether that bookmark exists.
	 */
	public function has_bookmark( $bookmark_name ): bool {
		return parent::has_bookmark( "_{$bookmark_name}" );
	}

	/*
	 * HTML Parsing Algorithms
	 */

	/**
	 * Closes a P element.
	 *
	 * @since 6.4.0
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#close-a-p-element
	 */
	private function close_a_p_element(): void {
		$this->generate_implied_end_tags( 'P' );
		$this->state->stack_of_open_elements->pop_until( 'P' );
	}

	/**
	 * Closes elements that have implied end tags.
	 *
	 * @since 6.4.0
	 * @since 6.7.0 Full spec support.
	 *
	 * @see https://html.spec.whatwg.org/#generate-implied-end-tags
	 *
	 * @param string|null $except_for_this_element Perform as if this element doesn't exist in the stack of open elements.
	 */
	private function generate_implied_end_tags( ?string $except_for_this_element = null ): void {
		$elements_with_implied_end_tags = array(
			'DD',
			'DT',
			'LI',
			'OPTGROUP',
			'OPTION',
			'P',
			'RB',
			'RP',
			'RT',
			'RTC',
		);

		$no_exclusions = ! isset( $except_for_this_element );

		while (
			( $no_exclusions || ! $this->state->stack_of_open_elements->current_node_is( $except_for_this_element ) ) &&
			in_array( $this->state->stack_of_open_elements->current_node()->node_name, $elements_with_implied_end_tags, true )
		) {
			$this->state->stack_of_open_elements->pop();
		}
	}

	/**
	 * Closes elements that have implied end tags, thoroughly.
	 *
	 * See the HTML specification for an explanation why this is
	 * different from generating end tags in the normal sense.
	 *
	 * @since 6.4.0
	 * @since 6.7.0 Full spec support.
	 *
	 * @see WP_HTML_Processor::generate_implied_end_tags
	 * @see https://html.spec.whatwg.org/#generate-implied-end-tags
	 */
	private function generate_implied_end_tags_thoroughly(): void {
		$elements_with_implied_end_tags = array(
			'CAPTION',
			'COLGROUP',
			'DD',
			'DT',
			'LI',
			'OPTGROUP',
			'OPTION',
			'P',
			'RB',
			'RP',
			'RT',
			'RTC',
			'TBODY',
			'TD',
			'TFOOT',
			'TH',
			'THEAD',
			'TR',
		);

		while ( in_array( $this->state->stack_of_open_elements->current_node()->node_name, $elements_with_implied_end_tags, true ) ) {
			$this->state->stack_of_open_elements->pop();
		}
	}

	/**
	 * Returns the adjusted current node.
	 *
	 * > The adjusted current node is the context element if the parser was created as
	 * > part of the HTML fragment parsing algorithm and the stack of open elements
	 * > has only one element in it (fragment case); otherwise, the adjusted current
	 * > node is the current node.
	 *
	 * @see https://html.spec.whatwg.org/#adjusted-current-node
	 *
	 * @since 6.7.0
	 *
	 * @return WP_HTML_Token|null The adjusted current node.
	 */
	private function get_adjusted_current_node(): ?WP_HTML_Token {
		if ( isset( $this->context_node ) && 1 === $this->state->stack_of_open_elements->count() ) {
			return $this->context_node;
		}

		return $this->state->stack_of_open_elements->current_node();
	}

	/**
	 * Reconstructs the active formatting elements.
	 *
	 * > This has the effect of reopening all the formatting elements that were opened
	 * > in the current body, cell, or caption (whichever is youngest) that haven't
	 * > been explicitly closed.
	 *
	 * @since 6.4.0
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#reconstruct-the-active-formatting-elements
	 *
	 * @return bool Whether any formatting elements needed to be reconstructed.
	 */
	private function reconstruct_active_formatting_elements(): bool {
		/*
		 * > If there are no entries in the list of active formatting elements, then there is nothing
		 * > to reconstruct; stop this algorithm.
		 */
		if ( 0 === $this->state->active_formatting_elements->count() ) {
			return false;
		}

		$last_entry = $this->state->active_formatting_elements->current_node();
		if (

			/*
			 * > If the last (most recently added) entry in the list of active formatting elements is a marker;
			 * > stop this algorithm.
			 */
			'marker' === $last_entry->node_name ||

			/*
			 * > If the last (most recently added) entry in the list of active formatting elements is an
			 * > element that is in the stack of open elements, then there is nothing to reconstruct;
			 * > stop this algorithm.
			 */
			$this->state->stack_of_open_elements->contains_node( $last_entry )
		) {
			return false;
		}

		$this->bail( 'Cannot reconstruct active formatting elements when advancing and rewinding is required.' );
	}

	/**
	 * Runs the reset the insertion mode appropriately algorithm.
	 *
	 * @since 6.7.0
	 *
	 * @see https://html.spec.whatwg.org/multipage/parsing.html#reset-the-insertion-mode-appropriately
	 */
	private function reset_insertion_mode_appropriately(): void {
		// Set the first node.
		$first_node = null;
		foreach ( $this->state->stack_of_open_elements->walk_down() as $first_node ) {
			break;
		}

		/*
		 * > 1. Let _last_ be false.
		 */
		$last = false;
		foreach ( $this->state->stack_of_open_elements->walk_up() as $node ) {
			/*
			 * > 2. Let _node_ be the last node in the stack of open elements.
			 * > 3. _Loop_: If _node_ is the first node in the stack of open elements, then set _last_
			 * >            to true, and, if the parser was created as part of the HTML fragment parsing
			 * >            algorithm (fragment case), set node to the context element passed to
			 * >            that algorithm.
			 * > …
			 */
			if ( $node === $first_node ) {
				$last = true;
				if ( isset( $this->context_node ) ) {
					$node = $this->context_node;
				}
			}

			// All of the following rules are for matching HTML elements.
			if ( 'html' !== $node->namespace ) {
				continue;
			}

			switch ( $node->node_name ) {
				/*
				 * > 4. If node is a `select` element, run these substeps:
				 * >   1. If _last_ is true, jump to the step below labeled done.
				 * >   2. Let _ancestor_ be _node_.
				 * >   3. _Loop_: If _ancestor_ is the first node in the stack of open elements,
				 * >      jump to the step below labeled done.
				 * >   4. Let ancestor be the node before ancestor in the stack of open elements.
				 * >   …
				 * >   7. Jump back to the step labeled _loop_.
				 * >   8. _Done_: Switch the insertion mode to "in select" and return.
				 */
				case 'SELECT':
					if ( ! $last ) {
						foreach ( $this->state->stack_of_open_elements->walk_up( $node ) as $ancestor ) {
							if ( 'html' !== $ancestor->namespace ) {
								continue;
							}

							switch ( $ancestor->node_name ) {
								/*
								 * > 5. If _ancestor_ is a `template` node, jump to the step below
								 * >    labeled _done_.
								 */
								case 'TEMPLATE':
									break 2;

								/*
								 * > 6. If _ancestor_ is a `table` node, switch the insertion mode to
								 * >    "in select in table" and return.
								 */
								case 'TABLE':
									$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_SELECT_IN_TABLE;
									return;
							}
						}
					}
					$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_SELECT;
					return;

				/*
				 * > 5. If _node_ is a `td` or `th` element and _last_ is false, then switch the
				 * >    insertion mode to "in cell" and return.
				 */
				case 'TD':
				case 'TH':
					if ( ! $last ) {
						$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_CELL;
						return;
					}
					break;

					/*
					* > 6. If _node_ is a `tr` element, then switch the insertion mode to "in row"
					* >    and return.
					*/
				case 'TR':
					$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_ROW;
					return;

				/*
				 * > 7. If _node_ is a `tbody`, `thead`, or `tfoot` element, then switch the
				 * >    insertion mode to "in table body" and return.
				 */
				case 'TBODY':
				case 'THEAD':
				case 'TFOOT':
					$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE_BODY;
					return;

				/*
				 * > 8. If _node_ is a `caption` element, then switch the insertion mode to
				 * >    "in caption" and return.
				 */
				case 'CAPTION':
					$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_CAPTION;
					return;

				/*
				 * > 9. If _node_ is a `colgroup` element, then switch the insertion mode to
				 * >    "in column group" and return.
				 */
				case 'COLGROUP':
					$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_COLUMN_GROUP;
					return;

				/*
				 * > 10. If _node_ is a `table` element, then switch the insertion mode to
				 * >     "in table" and return.
				 */
				case 'TABLE':
					$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_TABLE;
					return;

				/*
				 * > 11. If _node_ is a `template` element, then switch the insertion mode to the
				 * >     current template insertion mode and return.
				 */
				case 'TEMPLATE':
					$this->state->insertion_mode = end( $this->state->stack_of_template_insertion_modes );
					return;

				/*
				 * > 12. If _node_ is a `head` element and _last_ is false, then switch the
				 * >     insertion mode to "in head" and return.
				 */
				case 'HEAD':
					if ( ! $last ) {
						$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_HEAD;
						return;
					}
					break;

				/*
				 * > 13. If _node_ is a `body` element, then switch the insertion mode to "in body"
				 * >     and return.
				 */
				case 'BODY':
					$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_BODY;
					return;

				/*
				 * > 14. If _node_ is a `frameset` element, then switch the insertion mode to
				 * >     "in frameset" and return. (fragment case)
				 */
				case 'FRAMESET':
					$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_FRAMESET;
					return;

				/*
				 * > 15. If _node_ is an `html` element, run these substeps:
				 * >     1. If the head element pointer is null, switch the insertion mode to
				 * >        "before head" and return. (fragment case)
				 * >     2. Otherwise, the head element pointer is not null, switch the insertion
				 * >        mode to "after head" and return.
				 */
				case 'HTML':
					$this->state->insertion_mode = isset( $this->state->head_element )
						? WP_HTML_Processor_State::INSERTION_MODE_AFTER_HEAD
						: WP_HTML_Processor_State::INSERTION_MODE_BEFORE_HEAD;
					return;
			}
		}

		/*
		 * > 16. If _last_ is true, then switch the insertion mode to "in body"
		 * >     and return. (fragment case)
		 *
		 * This is only reachable if `$last` is true, as per the fragment parsing case.
		 */
		$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_BODY;
	}

	/**
	 * Runs the adoption agency algorithm.
	 *
	 * @since 6.4.0
	 *
	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
	 *
	 * @see https://html.spec.whatwg.org/#adoption-agency-algorithm
	 */
	private function run_adoption_agency_algorithm(): void {
		$budget       = 1000;
		$subject      = $this->get_tag();
		$current_node = $this->state->stack_of_open_elements->current_node();

		if (
			// > If the current node is an HTML element whose tag name is subject
			$current_node && $subject === $current_node->node_name &&
			// > the current node is not in the list of active formatting elements
			! $this->state->active_formatting_elements->contains_node( $current_node )
		) {
			$this->state->stack_of_open_elements->pop();
			return;
		}

		$outer_loop_counter = 0;
		while ( $budget-- > 0 ) {
			if ( $outer_loop_counter++ >= 8 ) {
				return;
			}

			/*
			 * > Let formatting element be the last element in the list of active formatting elements that:
			 * >   - is between the end of the list and the last marker in the list,
			 * >     if any, or the start of the list otherwise,
			 * >   - and has the tag name subject.
			 */
			$formatting_element = null;
			foreach ( $this->state->active_formatting_elements->walk_up() as $item ) {
				if ( 'marker' === $item->node_name ) {
					break;
				}

				if ( $subject === $item->node_name ) {
					$formatting_element = $item;
					break;
				}
			}

			// > If there is no such element, then return and instead act as described in the "any other end tag" entry above.
			if ( null === $formatting_element ) {
				$this->bail( 'Cannot run adoption agency when "any other end tag" is required.' );
			}

			// > If formatting element is not in the stack of open elements, then this is a parse error; remove the element from the list, and return.
			if ( ! $this->state->stack_of_open_elements->contains_node( $formatting_element ) ) {
				$this->state->active_formatting_elements->remove_node( $formatting_element );
				return;
			}

			// > If formatting element is in the stack of open elements, but the element is not in scope, then this is a parse error; return.
			if ( ! $this->state->stack_of_open_elements->has_element_in_scope( $formatting_element->node_name ) ) {
				return;
			}

			/*
			 * > Let furthest block be the topmost node in the stack of open elements that is lower in the stack
			 * > than formatting element, and is an element in the special category. There might not be one.
			 */
			$is_above_formatting_element = true;
			$furthest_block              = null;
			foreach ( $this->state->stack_of_open_elements->walk_down() as $item ) {
				if ( $is_above_formatting_element && $formatting_element->bookmark_name !== $item->bookmark_name ) {
					continue;
				}

				if ( $is_above_formatting_element ) {
					$is_above_formatting_element = false;
					continue;
				}

				if ( self::is_special( $item ) ) {
					$furthest_block = $item;
					break;
				}
			}

			/*
			 * > If there is no furthest block, then the UA must first pop all the nodes from the bottom of the
			 * > stack of open elements, from the current node up to and including formatting element, then
			 * > remove formatting element from the list of active formatting elements, and finally return.
			 */
			if ( null === $furthest_block ) {
				foreach ( $this->state->stack_of_open_elements->walk_up() as $item ) {
					$this->state->stack_of_open_elements->pop();

					if ( $formatting_element->bookmark_name === $item->bookmark_name ) {
						$this->state->active_formatting_elements->remove_node( $formatting_element );
						return;
					}
				}
			}

			$this->bail( 'Cannot extract common ancestor in adoption agency algorithm.' );
		}

		$this->bail( 'Cannot run adoption agency when looping required.' );
	}

	/**
	 * Runs the "close the cell" algorithm.
	 *
	 * > Where the steps above say to close the cell, they mean to run the following algorithm:
	 * >   1. Generate implied end tags.
	 * >   2. If the current node is not now a td element or a th element, then this is a parse error.
	 * >   3. Pop elements from the stack of open elements stack until a td element or a th element has been popped from the stack.
	 * >   4. Clear the list of active formatting elements up to the last marker.
	 * >   5. Switch the insertion mode to "in row".
	 *
	 * @see https://html.spec.whatwg.org/multipage/parsing.html#close-the-cell
	 *
	 * @since 6.7.0
	 */
	private function close_cell(): void {
		$this->generate_implied_end_tags();
		// @todo Parse error if the current node is a "td" or "th" element.
		foreach ( $this->state->stack_of_open_elements->walk_up() as $element ) {
			$this->state->stack_of_open_elements->pop();
			if ( 'TD' === $element->node_name || 'TH' === $element->node_name ) {
				break;
			}
		}
		$this->state->active_formatting_elements->clear_up_to_last_marker();
		$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_ROW;
	}

	/**
	 * Inserts an HTML element on the stack of open elements.
	 *
	 * @since 6.4.0
	 *
	 * @see https://html.spec.whatwg.org/#insert-a-foreign-element
	 *
	 * @param WP_HTML_Token $token Name of bookmark pointing to element in original input HTML.
	 */
	private function insert_html_element( WP_HTML_Token $token ): void {
		$this->state->stack_of_open_elements->push( $token );
	}

	/**
	 * Inserts a foreign element on to the stack of open elements.
	 *
	 * @since 6.7.0
	 *
	 * @see https://html.spec.whatwg.org/#insert-a-foreign-element
	 *
	 * @param WP_HTML_Token $token                     Insert this token. The token's namespace and
	 *                                                 insertion point will be updated correctly.
	 * @param bool          $only_add_to_element_stack Whether to skip the "insert an element at the adjusted
	 *                                                 insertion location" algorithm when adding this element.
	 */
	private function insert_foreign_element( WP_HTML_Token $token, bool $only_add_to_element_stack ): void {
		$adjusted_current_node = $this->get_adjusted_current_node();

		$token->namespace = $adjusted_current_node ? $adjusted_current_node->namespace : 'html';

		if ( $this->is_mathml_integration_point() ) {
			$token->integration_node_type = 'math';
		} elseif ( $this->is_html_integration_point() ) {
			$token->integration_node_type = 'html';
		}

		if ( false === $only_add_to_element_stack ) {
			/*
			 * @todo Implement the "appropriate place for inserting a node" and the
			 *       "insert an element at the adjusted insertion location" algorithms.
			 *
			 * These algorithms mostly impacts DOM tree construction and not the HTML API.
			 * Here, there's no DOM node onto which the element will be appended, so the
			 * parser will skip this step.
			 *
			 * @see https://html.spec.whatwg.org/#insert-an-element-at-the-adjusted-insertion-location
			 */
		}

		$this->insert_html_element( $token );
	}

	/**
	 * Inserts a virtual element on the stack of open elements.
	 *
	 * @since 6.7.0
	 *
	 * @param string      $token_name    Name of token to create and insert into the stack of open elements.
	 * @param string|null $bookmark_name Optional. Name to give bookmark for created virtual node.
	 *                                   Defaults to auto-creating a bookmark name.
	 * @return WP_HTML_Token Newly-created virtual token.
	 */
	private function insert_virtual_node( $token_name, $bookmark_name = null ): WP_HTML_Token {
		$here = $this->bookmarks[ $this->state->current_token->bookmark_name ];
		$name = $bookmark_name ?? $this->bookmark_token();

		$this->bookmarks[ $name ] = new WP_HTML_Span( $here->start, 0 );

		$token = new WP_HTML_Token( $name, $token_name, false );
		$this->insert_html_element( $token );
		return $token;
	}

	/*
	 * HTML Specification Helpers
	 */

	/**
	 * Indicates if the current token is a MathML integration point.
	 *
	 * @since 6.7.0
	 *
	 * @see https://html.spec.whatwg.org/#mathml-text-integration-point
	 *
	 * @return bool Whether the current token is a MathML integration point.
	 */
	private function is_mathml_integration_point(): bool {
		$current_token = $this->state->current_token;
		if ( ! isset( $current_token ) ) {
			return false;
		}

		if ( 'math' !== $current_token->namespace || 'M' !== $current_token->node_name[0] ) {
			return false;
		}

		$tag_name = $current_token->node_name;

		return (
			'MI' === $tag_name ||
			'MO' === $tag_name ||
			'MN' === $tag_name ||
			'MS' === $tag_name ||
			'MTEXT' === $tag_name
		);
	}

	/**
	 * Indicates if the current token is an HTML integration point.
	 *
	 * Note that this method must be an instance method with access
	 * to the current token, since it needs to examine the attributes
	 * of the currently-matched tag, if it's in the MathML namespace.
	 * Otherwise it would be required to scan the HTML and ensure that
	 * no other accounting is overlooked.
	 *
	 * @since 6.7.0
	 *
	 * @see https://html.spec.whatwg.org/#html-integration-point
	 *
	 * @return bool Whether the current token is an HTML integration point.
	 */
	private function is_html_integration_point(): bool {
		$current_token = $this->state->current_token;
		if ( ! isset( $current_token ) ) {
			return false;
		}

		if ( 'html' === $current_token->namespace ) {
			return false;
		}

		$tag_name = $current_token->node_name;

		if ( 'svg' === $current_token->namespace ) {
			return (
				'DESC' === $tag_name ||
				'FOREIGNOBJECT' === $tag_name ||
				'TITLE' === $tag_name
			);
		}

		if ( 'math' === $current_token->namespace ) {
			if ( 'ANNOTATION-XML' !== $tag_name ) {
				return false;
			}

			$encoding = $this->get_attribute( 'encoding' );

			return (
				is_string( $encoding ) &&
				(
					0 === strcasecmp( $encoding, 'application/xhtml+xml' ) ||
					0 === strcasecmp( $encoding, 'text/html' )
				)
			);
		}

		$this->bail( 'Should not have reached end of HTML Integration Point detection: check HTML API code.' );
		// This unnecessary return prevents tools from inaccurately reporting type errors.
		return false;
	}

	/**
	 * Returns whether an element of a given name is in the HTML special category.
	 *
	 * @since 6.4.0
	 *
	 * @see https://html.spec.whatwg.org/#special
	 *
	 * @param WP_HTML_Token|string $tag_name Node to check, or only its name if in the HTML namespace.
	 * @return bool Whether the element of the given name is in the special category.
	 */
	public static function is_special( $tag_name ): bool {
		if ( is_string( $tag_name ) ) {
			$tag_name = strtoupper( $tag_name );
		} else {
			$tag_name = 'html' === $tag_name->namespace
				? strtoupper( $tag_name->node_name )
				: "{$tag_name->namespace} {$tag_name->node_name}";
		}

		return (
			'ADDRESS' === $tag_name ||
			'APPLET' === $tag_name ||
			'AREA' === $tag_name ||
			'ARTICLE' === $tag_name ||
			'ASIDE' === $tag_name ||
			'BASE' === $tag_name ||
			'BASEFONT' === $tag_name ||
			'BGSOUND' === $tag_name ||
			'BLOCKQUOTE' === $tag_name ||
			'BODY' === $tag_name ||
			'BR' === $tag_name ||
			'BUTTON' === $tag_name ||
			'CAPTION' === $tag_name ||
			'CENTER' === $tag_name ||
			'COL' === $tag_name ||
			'COLGROUP' === $tag_name ||
			'DD' === $tag_name ||
			'DETAILS' === $tag_name ||
			'DIR' === $tag_name ||
			'DIV' === $tag_name ||
			'DL' === $tag_name ||
			'DT' === $tag_name ||
			'EMBED' === $tag_name ||
			'FIELDSET' === $tag_name ||
			'FIGCAPTION' === $tag_name ||
			'FIGURE' === $tag_name ||
			'FOOTER' === $tag_name ||
			'FORM' === $tag_name ||
			'FRAME' === $tag_name ||
			'FRAMESET' === $tag_name ||
			'H1' === $tag_name ||
			'H2' === $tag_name ||
			'H3' === $tag_name ||
			'H4' === $tag_name ||
			'H5' === $tag_name ||
			'H6' === $tag_name ||
			'HEAD' === $tag_name ||
			'HEADER' === $tag_name ||
			'HGROUP' === $tag_name ||
			'HR' === $tag_name ||
			'HTML' === $tag_name ||
			'IFRAME' === $tag_name ||
			'IMG' === $tag_name ||
			'INPUT' === $tag_name ||
			'KEYGEN' === $tag_name ||
			'LI' === $tag_name ||
			'LINK' === $tag_name ||
			'LISTING' === $tag_name ||
			'MAIN' === $tag_name ||
			'MARQUEE' === $tag_name ||
			'MENU' === $tag_name ||
			'META' === $tag_name ||
			'NAV' === $tag_name ||
			'NOEMBED' === $tag_name ||
			'NOFRAMES' === $tag_name ||
			'NOSCRIPT' === $tag_name ||
			'OBJECT' === $tag_name ||
			'OL' === $tag_name ||
			'P' === $tag_name ||
			'PARAM' === $tag_name ||
			'PLAINTEXT' === $tag_name ||
			'PRE' === $tag_name ||
			'SCRIPT' === $tag_name ||
			'SEARCH' === $tag_name ||
			'SECTION' === $tag_name ||
			'SELECT' === $tag_name ||
			'SOURCE' === $tag_name ||
			'STYLE' === $tag_name ||
			'SUMMARY' === $tag_name ||
			'TABLE' === $tag_name ||
			'TBODY' === $tag_name ||
			'TD' === $tag_name ||
			'TEMPLATE' === $tag_name ||
			'TEXTAREA' === $tag_name ||
			'TFOOT' === $tag_name ||
			'TH' === $tag_name ||
			'THEAD' === $tag_name ||
			'TITLE' === $tag_name ||
			'TR' === $tag_name ||
			'TRACK' === $tag_name ||
			'UL' === $tag_name ||
			'WBR' === $tag_name ||
			'XMP' === $tag_name ||

			// MathML.
			'math MI' === $tag_name ||
			'math MO' === $tag_name ||
			'math MN' === $tag_name ||
			'math MS' === $tag_name ||
			'math MTEXT' === $tag_name ||
			'math ANNOTATION-XML' === $tag_name ||

			// SVG.
			'svg DESC' === $tag_name ||
			'svg FOREIGNOBJECT' === $tag_name ||
			'svg TITLE' === $tag_name
		);
	}

	/**
	 * Returns whether a given element is an HTML Void Element
	 *
	 * > area, base, br, col, embed, hr, img, input, link, meta, source, track, wbr
	 *
	 * @since 6.4.0
	 *
	 * @see https://html.spec.whatwg.org/#void-elements
	 *
	 * @param string $tag_name Name of HTML tag to check.
	 * @return bool Whether the given tag is an HTML Void Element.
	 */
	public static function is_void( $tag_name ): bool {
		$tag_name = strtoupper( $tag_name );

		return (
			'AREA' === $tag_name ||
			'BASE' === $tag_name ||
			'BASEFONT' === $tag_name || // Obsolete but still treated as void.
			'BGSOUND' === $tag_name || // Obsolete but still treated as void.
			'BR' === $tag_name ||
			'COL' === $tag_name ||
			'EMBED' === $tag_name ||
			'FRAME' === $tag_name ||
			'HR' === $tag_name ||
			'IMG' === $tag_name ||
			'INPUT' === $tag_name ||
			'KEYGEN' === $tag_name || // Obsolete but still treated as void.
			'LINK' === $tag_name ||
			'META' === $tag_name ||
			'PARAM' === $tag_name || // Obsolete but still treated as void.
			'SOURCE' === $tag_name ||
			'TRACK' === $tag_name ||
			'WBR' === $tag_name
		);
	}

	/**
	 * Gets an encoding from a given string.
	 *
	 * This is an algorithm defined in the WHAT-WG specification.
	 *
	 * Example:
	 *
	 *     'UTF-8' === self::get_encoding( 'utf8' );
	 *     'UTF-8' === self::get_encoding( "  \tUTF-8 " );
	 *     null    === self::get_encoding( 'UTF-7' );
	 *     null    === self::get_encoding( 'utf8; charset=' );
	 *
	 * @see https://encoding.spec.whatwg.org/#concept-encoding-get
	 *
	 * @todo As this parser only supports UTF-8, only the UTF-8
	 *       encodings are detected. Add more as desired, but the
	 *       parser will bail on non-UTF-8 encodings.
	 *
	 * @since 6.7.0
	 *
	 * @param string $label A string which may specify a known encoding.
	 * @return string|null Known encoding if matched, otherwise null.
	 */
	protected static function get_encoding( string $label ): ?string {
		/*
		 * > Remove any leading and trailing ASCII whitespace from label.
		 */
		$label = trim( $label, " \t\f\r\n" );

		/*
		 * > If label is an ASCII case-insensitive match for any of the labels listed in the
		 * > table below, then return the corresponding encoding; otherwise return failure.
		 */
		switch ( strtolower( $label ) ) {
			case 'unicode-1-1-utf-8':
			case 'unicode11utf8':
			case 'unicode20utf8':
			case 'utf-8':
			case 'utf8':
			case 'x-unicode20utf8':
				return 'UTF-8';

			default:
				return null;
		}
	}

	/*
	 * Constants that would pollute the top of the class if they were found there.
	 */

	/**
	 * Indicates that the next HTML token should be parsed and processed.
	 *
	 * @since 6.4.0
	 *
	 * @var string
	 */
	const PROCESS_NEXT_NODE = 'process-next-node';

	/**
	 * Indicates that the current HTML token should be reprocessed in the newly-selected insertion mode.
	 *
	 * @since 6.4.0
	 *
	 * @var string
	 */
	const REPROCESS_CURRENT_NODE = 'reprocess-current-node';

	/**
	 * Indicates that the current HTML token should be processed without advancing the parser.
	 *
	 * @since 6.5.0
	 *
	 * @var string
	 */
	const PROCESS_CURRENT_NODE = 'process-current-node';

	/**
	 * Indicates that the parser encountered unsupported markup and has bailed.
	 *
	 * @since 6.4.0
	 *
	 * @var string
	 */
	const ERROR_UNSUPPORTED = 'unsupported';

	/**
	 * Indicates that the parser encountered more HTML tokens than it
	 * was able to process and has bailed.
	 *
	 * @since 6.4.0
	 *
	 * @var string
	 */
	const ERROR_EXCEEDED_MAX_BOOKMARKS = 'exceeded-max-bookmarks';

	/**
	 * Unlock code that must be passed into the constructor to create this class.
	 *
	 * This class extends the WP_HTML_Tag_Processor, which has a public class
	 * constructor. Therefore, it's not possible to have a private constructor here.
	 *
	 * This unlock code is used to ensure that anyone calling the constructor is
	 * doing so with a full understanding that it's intended to be a private API.
	 *
	 * @access private
	 */
	const CONSTRUCTOR_UNLOCK_CODE = 'Use WP_HTML_Processor::create_fragment() instead of calling the class constructor directly.';
}
			
			


Thanks For 0xGh05T - DSRF14 - Mr.Dan07 - Leri01 - FxshX7 - AlkaExploiter - xLoveSyndrome'z - Acep Gans'z

JMDS TRACK – Just Another Diagnostics Lab Site

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JMDS TRACK Cameroon

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Fleet management

  1. Reduce the operting cost and the unavailability of your vehicles
  2. reduce the fuel consumption of your fleet
  3. Improve the driving dehavior and safety of your drivers
  4. optimize the utilization rate of your equipment 
  5. protect your vehicle against theft
  6. Improve the quality of your customer service


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Assets management

  1. Track the roaming of your equipment
  2. Optimise the management of your assets on site and during transport
  3. Secure the transport of your goods
  4. Make your team responsible for preventing the loss of tools, equipment
  5. Take a real-time inventory of your equipment on site
  6. Easily find your mobile objects or equipment



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Antitheft solutions

  1. Secure your vehicles and machinery and increase your chances of recovering them in the event of theft
  2. Protect your assets and reduce the costs associated with their loss
  3. Combine immobiliser and driver identification and limit the risk of theft
  4. Identify fuel theft and reduce costs
  5. Protect your goods and take no more risks
  6. Be alerted to abnormal events

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 Douala BP cité 

     and

Yaoundé Total Essos


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What makes us different from others

  • young and dynamic team
  • call center 24/24 7/7
  • roaming throughout Africa
  • team of developers who can develop customer-specific solutions
  • diversity of services
  • reactive and prompt after-sales service when soliciting a customer or a malfunction
  • Free Maintenance and installation in the cities of Douala and Yaounde

https://youtu.be/xI1cz_Jh2x8

15+
years of experience in GPS system development, production and deployment.

15 Collaborators

More than 15 employees dedicated to the research and development of new applications and to customer care

5 000 Vehicles and mobile assets

5 000 vehicles and mobile assets under management, in Africa

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Bon SAV , SATISFAIT DU TRAITEMENT DES REQUETES

M DIPITA CHRISTIAN
Logistic Safety Manager Road Safety Manager
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Nous restons satisfait dans l’ensemble des prestations relatives a la couverture de notre parc automobile

Hervé Frédéric NDENGUE
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5/5
L’APPLICATION EMIXIS est convivial A L’utilisation
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CUSTOMER

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