ion that enqueues the CSS Custom Properties coming from theme.json.
 *
 * @since 5.9.0
 */
function wp_enqueue_global_styles_css_custom_properties() {
	wp_register_style( 'global-styles-css-custom-properties', false );
	wp_add_inline_style( 'global-styles-css-custom-properties', wp_get_global_stylesheet( array( 'variables' ) ) );
	wp_enqueue_style( 'global-styles-css-custom-properties' );
}

/**
 * Hooks inline styles in the proper place, depending on the active theme.
 *
 * @since 5.9.1
 * @since 6.1.0 Added the `$priority` parameter.
 *
 * For block themes, styles are loaded in the head.
 * For classic ones, styles are loaded in the body because the wp_head action happens before render_block.
 *
 * @link https://core.trac.wordpress.org/ticket/53494.
 *
 * @param string $style    String containing the CSS styles to be added.
 * @param int    $priority To set the priority for the add_action.
 */
function wp_enqueue_block_support_styles( $style, $priority = 10 ) {
	$action_hook_name = 'wp_footer';
	if ( wp_is_block_theme() ) {
		$action_hook_name = 'wp_head';
	}
	add_action(
		$action_hook_name,
		static function () use ( $style ) {
			echo "<style>$style</style>\n";
		},
		$priority
	);
}

/**
 * Fetches, processes and compiles stored core styles, then combines and renders them to the page.
 * Styles are stored via the style engine API.
 *
 * @link https://developer.wordpress.org/block-editor/reference-guides/packages/packages-style-engine/
 *
 * @since 6.1.0
 *
 * @param array $options {
 *     Optional. An array of options to pass to wp_style_engine_get_stylesheet_from_context().
 *     Default empty array.
 *
 *     @type bool $optimize Whether to optimize the CSS output, e.g., combine rules.
 *                          Default false.
 *     @type bool $prettify Whether to add new lines and indents to output.
 *                          Default to whether the `SCRIPT_DEBUG` constant is defined.
 * }
 */
function wp_enqueue_stored_styles( $options = array() ) {
	$is_block_theme   = wp_is_block_theme();
	$is_classic_theme = ! $is_block_theme;

	/*
	 * For block themes, this function prints stored styles in the header.
	 * For classic themes, in the footer.
	 */
	if (
		( $is_block_theme && doing_action( 'wp_footer' ) ) ||
		( $is_classic_theme && doing_action( 'wp_enqueue_scripts' ) )
	) {
		return;
	}

	$core_styles_keys         = array( 'block-supports' );
	$compiled_core_stylesheet = '';
	$style_tag_id             = 'core';
	// Adds comment if code is prettified to identify core styles sections in debugging.
	$should_prettify = isset( $options['prettify'] ) ? true === $options['prettify'] : defined( 'SCRIPT_DEBUG' ) && SCRIPT_DEBUG;
	foreach ( $core_styles_keys as $style_key ) {
		if ( $should_prettify ) {
			$compiled_core_stylesheet .= "/**\n * Core styles: $style_key\n */\n";
		}
		// Chains core store ids to signify what the styles contain.
		$style_tag_id             .= '-' . $style_key;
		$compiled_core_stylesheet .= wp_style_engine_get_stylesheet_from_context( $style_key, $options );
	}

	// Combines Core styles.
	if ( ! empty( $compiled_core_stylesheet ) ) {
		wp_register_style( $style_tag_id, false );
		wp_add_inline_style( $style_tag_id, $compiled_core_stylesheet );
		wp_enqueue_style( $style_tag_id );
	}

	// Prints out any other stores registered by themes or otherwise.
	$additional_stores = WP_Style_Engine_CSS_Rules_Store::get_stores();
	foreach ( array_keys( $additional_stores ) as $store_name ) {
		if ( in_array( $store_name, $core_styles_keys, true ) ) {
			continue;
		}
		$styles = wp_style_engine_get_stylesheet_from_context( $store_name, $options );
		if ( ! empty( $styles ) ) {
			$key = "wp-style-engine-$store_name";
			wp_register_style( $key, false );
			wp_add_inline_style( $key, $styles );
			wp_enqueue_style( $key );
		}
	}
}

/**
 * Enqueues a stylesheet for a specific block.
 *
 * If the theme has opted-in to separate-styles loading,
 * then the stylesheet will be enqueued on-render,
 * otherwise when the block inits.
 *
 * @since 5.9.0
 *
 * @param string $block_name The block-name, including namespace.
 * @param array  $args       {
 *     An array of arguments. See wp_register_style() for full information about each argument.
 *
 *     @type string           $handle The handle for the stylesheet.
 *     @type string|false     $src    The source URL of the stylesheet.
 *     @type string[]         $deps   Array of registered stylesheet handles this stylesheet depends on.
 *     @type string|bool|null $ver    Stylesheet version number.
 *     @type string           $media  The media for which this stylesheet has been defined.
 *     @type string|null      $path   Absolute path to the stylesheet, so that it can potentially be inlined.
 * }
 */
function wp_enqueue_block_style( $block_name, $args ) {
	$args = wp_parse_args(
		$args,
		array(
			'handle' => '',
			'src'    => '',
			'deps'   => array(),
			'ver'    => false,
			'media'  => 'all',
		)
	);

	/**
	 * Callback function to register and enqueue styles.
	 *
	 * @param string $content When the callback is used for the render_block filter,
	 *                        the content needs to be returned so the function parameter
	 *                        is to ensure the content exists.
	 * @return string Block content.
	 */
	$callback = static function ( $content ) use ( $args ) {
		// Register the stylesheet.
		if ( ! empty( $args['src'] ) ) {
			wp_register_style( $args['handle'], $args['src'], $args['deps'], $args['ver'], $args['media'] );
		}

		// Add `path` data if provided.
		if ( isset( $args['path'] ) ) {
			wp_style_add_data( $args['handle'], 'path', $args['path'] );

			// Get the RTL file path.
			$rtl_file_path = str_replace( '.css', '-rtl.css', $args['path'] );

			// Add RTL stylesheet.
			if ( file_exists( $rtl_file_path ) ) {
				wp_style_add_data( $args['handle'], 'rtl', 'replace' );

				if ( is_rtl() ) {
					wp_style_add_data( $args['handle'], 'path', $rtl_file_path );
				}
			}
		}

		// Enqueue the stylesheet.
		wp_enqueue_style( $args['handle'] );

		return $content;
	};

	$hook = did_action( 'wp_enqueue_scripts' ) ? 'wp_footer' : 'wp_enqueue_scripts';
	if ( wp_should_load_separate_core_block_assets() ) {
		/**
		 * Callback function to register and enqueue styles.
		 *
		 * @param string $content The block content.
		 * @param array  $block   The full block, including name and attributes.
		 * @return string Block content.
		 */
		$callback_separate = static function ( $content, $block ) use ( $block_name, $callback ) {
			if ( ! empty( $block['blockName'] ) && $block_name === $block['blockName'] ) {
				return $callback( $content );
			}
			return $content;
		};

		/*
		 * The filter's callback here is an anonymous function because
		 * using a named function in this case is not possible.
		 *
		 * The function cannot be unhooked, however, users are still able
		 * to dequeue the stylesheets registered/enqueued by the callback
		 * which is why in this case, using an anonymous function
		 * was deemed acceptable.
		 */
		add_filter( 'render_block', $callback_separate, 10, 2 );
		return;
	}

	/*
	 * The filter's callback here is an anonymous function because
	 * using a named function in this case is not possible.
	 *
	 * The function cannot be unhooked, however, users are still able
	 * to dequeue the stylesheets registered/enqueued by the callback
	 * which is why in this case, using an anonymous function
	 * was deemed acceptable.
	 */
	add_filter( $hook, $callback );

	// Enqueue assets in the editor.
	add_action( 'enqueue_block_assets', $callback );
}

/**
 * Loads classic theme styles on classic themes in the frontend.
 *
 * This is needed for backwards compatibility for button blocks specifically.
 *
 * @since 6.1.0
 */
function wp_enqueue_classic_theme_styles() {
	if ( ! wp_theme_has_theme_json() ) {
		$suffix = wp_scripts_get_suffix();
		wp_register_style( 'classic-theme-styles', '/' . WPINC . "/css/classic-themes$suffix.css" );
		wp_style_add_data( 'classic-theme-styles', 'path', ABSPATH . WPINC . "/css/classic-themes$suffix.css" );
		wp_enqueue_style( 'classic-theme-styles' );
	}
}

/**
 * Loads classic theme styles on classic themes in the editor.
 *
 * This is needed for backwards compatibility for button blocks specifically.
 *
 * @since 6.1.0
 *
 * @param array $editor_settings The array of editor settings.
 * @return array A filtered array of editor settings.
 */
function wp_add_editor_classic_theme_styles( $editor_settings ) {
	if ( wp_theme_has_theme_json() ) {
		return $editor_settings;
	}

	$suffix               = wp_scripts_get_suffix();
	$classic_theme_styles = ABSPATH . WPINC . "/css/classic-themes$suffix.css";

	/*
	 * This follows the pattern of get_block_editor_theme_styles,
	 * but we can't use get_block_editor_theme_styles directly as it
	 * only handles external files or theme files.
	 */
	$classic_theme_styles_settings = array(
		'css'            => file_get_contents( $classic_theme_styles ),
		'__unstableType' => 'core',
		'isGlobalStyles' => false,
	);

	// Add these settings to the start of the array so that themes can override them.
	array_unshift( $editor_settings['styles'], $classic_theme_styles_settings );

	return $editor_settings;
}

/**
 * Removes leading and trailing _empty_ script tags.
 *
 * This is a helper meant to be used for literal script tag construction
 * within `wp_get_inline_script_tag()` or `wp_print_inline_script_tag()`.
 * It removes the literal values of "<script>" and "</script>" from
 * around an inline script after trimming whitespace. Typlically this
 * is used in conjunction with output buffering, where `ob_get_clean()`
 * is passed as the `$contents` argument.
 *
 * Example:
 *
 *     // Strips exact literal empty SCRIPT tags.
 *     $js = '<script>sayHello();</script>;
 *     'sayHello();' === wp_remove_surrounding_empty_script_tags( $js );
 *
 *     // Otherwise if anything is different it warns in the JS console.
 *     $js = '<script type="text/javascript">console.log( "hi" );</script>';
 *     'console.error( ... )' === wp_remove_surrounding_empty_script_tags( $js );
 *
 * @private
 * @since 6.4.0
 *
 * @see wp_print_inline_script_tag()
 * @see wp_get_inline_script_tag()
 *
 * @param string $contents Script body with manually created SCRIPT tag literals.
 * @return string Script body without surrounding script tag literals, or
 *                original contents if both exact literals aren't present.
 */
function wp_remove_surrounding_empty_script_tags( $contents ) {
	$contents = trim( $contents );
	$opener   = '<SCRIPT>';
	$closer   = '</SCRIPT>';

	if (
		strlen( $contents ) > strlen( $opener ) + strlen( $closer ) &&
		strtoupper( substr( $contents, 0, strlen( $opener ) ) ) === $opener &&
		strtoupper( substr( $contents, -strlen( $closer ) ) ) === $closer
	) {
		return substr( $contents, strlen( $opener ), -strlen( $closer ) );
	} else {
		$error_message = __( 'Expected string to start with script tag (without attributes) and end with script tag, with optional whitespace.' );
		_doing_it_wrong( __FUNCTION__, $error_message, '6.4' );
		return sprintf( 'console.error(%s)', wp_json_encode( __( 'Function wp_remove_surrounding_empty_script_tags() used incorrectly in PHP.' ) . ' ' . $error_message ) );
	}
}
se;
		}

		$enqueued_text = $this->lexical_updates[ $comparable_name ]->text;

		// Removed attributes erase the entire span.
		if ( '' === $enqueued_text ) {
			return null;
		}

		/*
		 * Boolean attribute updates are just the attribute name without a corresponding value.
		 *
		 * This value might differ from the given comparable name in that there could be leading
		 * or trailing whitespace, and that the casing follows the name given in `set_attribute`.
		 *
		 * Example:
		 *
		 *     $p->set_attribute( 'data-TEST-id', 'update' );
		 *     'update' === $p->get_enqueued_attribute_value( 'data-test-id' );
		 *
		 * Detect this difference based on the absence of the `=`, which _must_ exist in any
		 * attribute containing a value, e.g. `<input type="text" enabled />`.
		 *                                            ¹           ²
		 *                                       1. Attribute with a string value.
		 *                                       2. Boolean attribute whose value is `true`.
		 */
		$equals_at = strpos( $enqueued_text, '=' );
		if ( false === $equals_at ) {
			return true;
		}

		/*
		 * Finally, a normal update's value will appear after the `=` and
		 * be double-quoted, as performed incidentally by `set_attribute`.
		 *
		 * e.g. `type="text"`
		 *           ¹²    ³
		 *        1. Equals is here.
		 *        2. Double-quoting starts one after the equals sign.
		 *        3. Double-quoting ends at the last character in the update.
		 */
		$enqueued_value = substr( $enqueued_text, $equals_at + 2, -1 );
		return html_entity_decode( $enqueued_value );
	}

	/**
	 * Returns the value of a requested attribute from a matched tag opener if that attribute exists.
	 *
	 * Example:
	 *
	 *     $p = new WP_HTML_Tag_Processor( '<div enabled class="test" data-test-id="14">Test</div>' );
	 *     $p->next_tag( array( 'class_name' => 'test' ) ) === 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 6.2.0
	 *
	 * @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 ) {
		if ( null === $this->tag_name_starts_at ) {
			return null;
		}

		$comparable = strtolower( $name );

		/*
		 * For every attribute other than `class` it's possible to perform a quick check if
		 * there's an enqueued lexical update whose value takes priority over what's found in
		 * the input document.
		 *
		 * The `class` attribute is special though because of the exposed helpers `add_class`
		 * and `remove_class`. These form a builder for the `class` attribute, so an additional
		 * check for enqueued class changes is required in addition to the check for any enqueued
		 * attribute values. If any exist, those enqueued class changes must first be flushed out
		 * into an attribute value update.
		 */
		if ( 'class' === $name ) {
			$this->class_name_updates_to_attributes_updates();
		}

		// Return any enqueued attribute value updates if they exist.
		$enqueued_value = $this->get_enqueued_attribute_value( $comparable );
		if ( false !== $enqueued_value ) {
			return $enqueued_value;
		}

		if ( ! isset( $this->attributes[ $comparable ] ) ) {
			return null;
		}

		$attribute = $this->attributes[ $comparable ];

		/*
		 * This flag distinguishes an attribute with no value
		 * from an attribute with an empty string value. For
		 * unquoted attributes this could look very similar.
		 * It refers to whether an `=` follows the name.
		 *
		 * e.g. <div boolean-attribute empty-attribute=></div>
		 *           ¹                 ²
		 *        1. Attribute `boolean-attribute` is `true`.
		 *        2. Attribute `empty-attribute` is `""`.
		 */
		if ( true === $attribute->is_true ) {
			return true;
		}

		$raw_value = substr( $this->html, $attribute->value_starts_at, $attribute->value_length );

		return html_entity_decode( $raw_value );
	}

	/**
	 * 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 6.2.0
	 *
	 * @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 ) {
		if ( $this->is_closing_tag || null === $this->tag_name_starts_at ) {
			return null;
		}

		$comparable = strtolower( $prefix );

		$matches = array();
		foreach ( array_keys( $this->attributes ) as $attr_name ) {
			if ( str_starts_with( $attr_name, $comparable ) ) {
				$matches[] = $attr_name;
			}
		}
		return $matches;
	}

	/**
	 * Returns the uppercase name of the matched tag.
	 *
	 * Example:
	 *
	 *     $p = new WP_HTML_Tag_Processor( '<div class="test">Test</div>' );
	 *     $p->next_tag() === true;
	 *     $p->get_tag() === 'DIV';
	 *
	 *     $p->next_tag() === false;
	 *     $p->get_tag() === null;
	 *
	 * @since 6.2.0
	 *
	 * @return string|null Name of currently matched tag in input HTML, or `null` if none found.
	 */
	public function get_tag() {
		if ( null === $this->tag_name_starts_at ) {
			return null;
		}

		$tag_name = substr( $this->html, $this->tag_name_starts_at, $this->tag_name_length );

		return strtoupper( $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 6.3.0
	 *
	 * @return bool Whether the currently matched tag contains the self-closing flag.
	 */
	public function has_self_closing_flag() {
		if ( ! $this->tag_name_starts_at ) {
			return false;
		}

		return '/' === $this->html[ $this->tag_ends_at - 1 ];
	}

	/**
	 * Indicates if the current tag token is a tag closer.
	 *
	 * Example:
	 *
	 *     $p = new WP_HTML_Tag_Processor( '<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 6.2.0
	 *
	 * @return bool Whether the current tag is a tag closer.
	 */
	public function is_tag_closer() {
		return $this->is_closing_tag;
	}

	/**
	 * 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 6.2.0
	 * @since 6.2.1 Fix: Only create a single update for multiple calls with case-variant attribute names.
	 *
	 * @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 ) {
		if ( $this->is_closing_tag || null === $this->tag_name_starts_at ) {
			return false;
		}

		/*
		 * WordPress rejects more characters than are strictly forbidden
		 * in HTML5. This is to prevent additional security risks deeper
		 * in the WordPress and plugin stack. Specifically the
		 * less-than (<) greater-than (>) and ampersand (&) aren't allowed.
		 *
		 * The use of a PCRE match enables looking for specific Unicode
		 * code points without writing a UTF-8 decoder. Whereas scanning
		 * for one-byte characters is trivial (with `strcspn`), scanning
		 * for the longer byte sequences would be more complicated. Given
		 * that this shouldn't be in the hot path for execution, it's a
		 * reasonable compromise in efficiency without introducing a
		 * noticeable impact on the overall system.
		 *
		 * @see https://html.spec.whatwg.org/#attributes-2
		 *
		 * @TODO as the only regex pattern maybe we should take it out? are
		 *       Unicode patterns available broadly in Core?
		 */
		if ( preg_match(
			'~[' .
				// Syntax-like characters.
				'"\'>&</ =' .
				// Control characters.
				'\x{00}-\x{1F}' .
				// HTML noncharacters.
				'\x{FDD0}-\x{FDEF}' .
				'\x{FFFE}\x{FFFF}\x{1FFFE}\x{1FFFF}\x{2FFFE}\x{2FFFF}\x{3FFFE}\x{3FFFF}' .
				'\x{4FFFE}\x{4FFFF}\x{5FFFE}\x{5FFFF}\x{6FFFE}\x{6FFFF}\x{7FFFE}\x{7FFFF}' .
				'\x{8FFFE}\x{8FFFF}\x{9FFFE}\x{9FFFF}\x{AFFFE}\x{AFFFF}\x{BFFFE}\x{BFFFF}' .
				'\x{CFFFE}\x{CFFFF}\x{DFFFE}\x{DFFFF}\x{EFFFE}\x{EFFFF}\x{FFFFE}\x{FFFFF}' .
				'\x{10FFFE}\x{10FFFF}' .
			']~Ssu',
			$name
		) ) {
			_doing_it_wrong(
				__METHOD__,
				__( 'Invalid attribute name.' ),
				'6.2.0'
			);

			return false;
		}

		/*
		 * > The values "true" and "false" are not allowed on boolean attributes.
		 * > To represent a false value, the attribute has to be omitted altogether.
		 *     - HTML5 spec, https://html.spec.whatwg.org/#boolean-attributes
		 */
		if ( false === $value ) {
			return $this->remove_attribute( $name );
		}

		if ( true === $value ) {
			$updated_attribute = $name;
		} else {
			$escaped_new_value = esc_attr( $value );
			$updated_attribute = "{$name}=\"{$escaped_new_value}\"";
		}

		/*
		 * > 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
		 *
		 * @see https://html.spec.whatwg.org/multipage/syntax.html#attributes-2:ascii-case-insensitive
		 */
		$comparable_name = strtolower( $name );

		if ( isset( $this->attributes[ $comparable_name ] ) ) {
			/*
			 * Update an existing attribute.
			 *
			 * Example – set attribute id to "new" in <div id="initial_id" />:
			 *
			 *     <div id="initial_id"/>
			 *          ^-------------^
			 *          start         end
			 *     replacement: `id="new"`
			 *
			 *     Result: <div id="new"/>
			 */
			$existing_attribute                        = $this->attributes[ $comparable_name ];
			$this->lexical_updates[ $comparable_name ] = new WP_HTML_Text_Replacement(
				$existing_attribute->start,
				$existing_attribute->end,
				$updated_attribute
			);
		} else {
			/*
			 * Create a new attribute at the tag's name end.
			 *
			 * Example – add attribute id="new" to <div />:
			 *
			 *     <div/>
			 *         ^
			 *         start and end
			 *     replacement: ` id="new"`
			 *
			 *     Result: <div id="new"/>
			 */
			$this->lexical_updates[ $comparable_name ] = new WP_HTML_Text_Replacement(
				$this->tag_name_starts_at + $this->tag_name_length,
				$this->tag_name_starts_at + $this->tag_name_length,
				' ' . $updated_attribute
			);
		}

		/*
		 * Any calls to update the `class` attribute directly should wipe out any
		 * enqueued class changes from `add_class` and `remove_class`.
		 */
		if ( 'class' === $comparable_name && ! empty( $this->classname_updates ) ) {
			$this->classname_updates = array();
		}

		return true;
	}

	/**
	 * Remove an attribute from the currently-matched tag.
	 *
	 * @since 6.2.0
	 *
	 * @param string $name The attribute name to remove.
	 * @return bool Whether an attribute was removed.
	 */
	public function remove_attribute( $name ) {
		if ( $this->is_closing_tag ) {
			return false;
		}

		/*
		 * > 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
		 *
		 * @see https://html.spec.whatwg.org/multipage/syntax.html#attributes-2:ascii-case-insensitive
		 */
		$name = strtolower( $name );

		/*
		 * Any calls to update the `class` attribute directly should wipe out any
		 * enqueued class changes from `add_class` and `remove_class`.
		 */
		if ( 'class' === $name && count( $this->classname_updates ) !== 0 ) {
			$this->classname_updates = array();
		}

		/*
		 * If updating an attribute that didn't exist in the input
		 * document, then remove the enqueued update and move on.
		 *
		 * For example, this might occur when calling `remove_attribute()`
		 * after calling `set_attribute()` for the same attribute
		 * and when that attribute wasn't originally present.
		 */
		if ( ! isset( $this->attributes[ $name ] ) ) {
			if ( isset( $this->lexical_updates[ $name ] ) ) {
				unset( $this->lexical_updates[ $name ] );
			}
			return false;
		}

		/*
		 * Removes an existing tag attribute.
		 *
		 * Example – remove the attribute id from <div id="main"/>:
		 *    <div id="initial_id"/>
		 *         ^-------------^
		 *         start         end
		 *    replacement: ``
		 *
		 *    Result: <div />
		 */
		$this->lexical_updates[ $name ] = new WP_HTML_Text_Replacement(
			$this->attributes[ $name ]->start,
			$this->attributes[ $name ]->end,
			''
		);

		// Removes any duplicated attributes if they were also present.
		if ( null !== $this->duplicate_attributes && array_key_exists( $name, $this->duplicate_attributes ) ) {
			foreach ( $this->duplicate_attributes[ $name ] as $attribute_token ) {
				$this->lexical_updates[] = new WP_HTML_Text_Replacement(
					$attribute_token->start,
					$attribute_token->end,
					''
				);
			}
		}

		return true;
	}

	/**
	 * Adds a new class name to the currently matched tag.
	 *
	 * @since 6.2.0
	 *
	 * @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 ) {
		if ( $this->is_closing_tag ) {
			return false;
		}

		if ( null !== $this->tag_name_starts_at ) {
			$this->classname_updates[ $class_name ] = self::ADD_CLASS;
		}

		return true;
	}

	/**
	 * Removes a class name from the currently matched tag.
	 *
	 * @since 6.2.0
	 *
	 * @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 ) {
		if ( $this->is_closing_tag ) {
			return false;
		}

		if ( null !== $this->tag_name_starts_at ) {
			$this->classname_updates[ $class_name ] = self::REMOVE_CLASS;
		}

		return true;
	}

	/**
	 * Returns the string representation of the HTML Tag Processor.
	 *
	 * @since 6.2.0
	 *
	 * @see WP_HTML_Tag_Processor::get_updated_html()
	 *
	 * @return string The processed HTML.
	 */
	public function __toString() {
		return $this->get_updated_html();
	}

	/**
	 * Returns the string representation of the HTML Tag Processor.
	 *
	 * @since 6.2.0
	 * @since 6.2.1 Shifts the internal cursor corresponding to the applied updates.
	 * @since 6.4.0 No longer calls subclass method `next_tag()` after updating HTML.
	 *
	 * @return string The processed HTML.
	 */
	public function get_updated_html() {
		$requires_no_updating = 0 === count( $this->classname_updates ) && 0 === count( $this->lexical_updates );

		/*
		 * When there is nothing more to update and nothing has already been
		 * updated, return the original document and avoid a string copy.
		 */
		if ( $requires_no_updating ) {
			return $this->html;
		}

		/*
		 * Keep track of the position right before the current tag. This will
		 * be necessary for reparsing the current tag after updating the HTML.
		 */
		$before_current_tag = $this->tag_name_starts_at - 1;

		/*
		 * 1. Apply the enqueued edits and update all the pointers to reflect those changes.
		 */
		$this->class_name_updates_to_attributes_updates();
		$before_current_tag += $this->apply_attributes_updates( $before_current_tag );

		/*
		 * 2. Rewind to before the current tag and reparse to get updated attributes.
		 *
		 * At this point the internal cursor points to the end of the tag name.
		 * Rewind before the tag name starts so that it's as if the cursor didn't
		 * move; a call to `next_tag()` will reparse the recently-updated attributes
		 * and additional calls to modify the attributes will apply at this same
		 * location, but in order to avoid issues with subclasses that might add
		 * behaviors to `next_tag()`, the internal methods should be called here
		 * instead.
		 *
		 * It's important to note that in this specific place there will be no change
		 * because the processor was already at a tag when this was called and it's
		 * rewinding only to the beginning of this very tag before reprocessing it
		 * and its attributes.
		 *
		 * <p>Previous HTML<em>More HTML</em></p>
		 *                 ↑  │ back up by the length of the tag name plus the opening <
		 *                 └←─┘ back up by strlen("em") + 1 ==> 3
		 */
		$this->bytes_already_parsed = $before_current_tag;
		$this->parse_next_tag();
		// Reparse the attributes.
		while ( $this->parse_next_attribute() ) {
			continue;
		}

		$tag_ends_at                = strpos( $this->html, '>', $this->bytes_already_parsed );
		$this->tag_ends_at          = $tag_ends_at;
		$this->bytes_already_parsed = $tag_ends_at;

		return $this->html;
	}

	/**
	 * Parses tag query input into internal search criteria.
	 *
	 * @since 6.2.0
	 *
	 * @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 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 class name to match.
	 *     @type string      $tag_closers  "visit" or "skip": whether to stop on tag closers, e.g. </div>.
	 * }
	 */
	private function parse_query( $query ) {
		if ( null !== $query && $query === $this->last_query ) {
			return;
		}

		$this->last_query          = $query;
		$this->sought_tag_name     = null;
		$this->sought_class_name   = null;
		$this->sought_match_offset = 1;
		$this->stop_on_tag_closers = false;

		// A single string value means "find the tag of this name".
		if ( is_string( $query ) ) {
			$this->sought_tag_name = $query;
			return;
		}

		// An empty query parameter applies no restrictions on the search.
		if ( null === $query ) {
			return;
		}

		// If not using the string interface, an associative array is required.
		if ( ! is_array( $query ) ) {
			_doing_it_wrong(
				__METHOD__,
				__( 'The query argument must be an array or a tag name.' ),
				'6.2.0'
			);
			return;
		}

		if ( isset( $query['tag_name'] ) && is_string( $query['tag_name'] ) ) {
			$this->sought_tag_name = $query['tag_name'];
		}

		if ( isset( $query['class_name'] ) && is_string( $query['class_name'] ) ) {
			$this->sought_class_name = $query['class_name'];
		}

		if ( isset( $query['match_offset'] ) && is_int( $query['match_offset'] ) && 0 < $query['match_offset'] ) {
			$this->sought_match_offset = $query['match_offset'];
		}

		if ( isset( $query['tag_closers'] ) ) {
			$this->stop_on_tag_closers = 'visit' === $query['tag_closers'];
		}
	}


	/**
	 * Checks whether a given tag and its attributes match the search criteria.
	 *
	 * @since 6.2.0
	 *
	 * @return bool Whether the given tag and its attribute match the search criteria.
	 */
	private function matches() {
		if ( $this->is_closing_tag && ! $this->stop_on_tag_closers ) {
			return false;
		}

		// Does the tag name match the requested tag name in a case-insensitive manner?
		if ( null !== $this->sought_tag_name ) {
			/*
			 * String (byte) length lookup is fast. If they aren't the
			 * same length then they can't be the same string values.
			 */
			if ( strlen( $this->sought_tag_name ) !== $this->tag_name_length ) {
				return false;
			}

			/*
			 * Check each character to determine if they are the same.
			 * Defer calls to `strtoupper()` to avoid them when possible.
			 * Calling `strcasecmp()` here tested slowed than comparing each
			 * character, so unless benchmarks show otherwise, it should
			 * not be used.
			 *
			 * It's expected that most of the time that this runs, a
			 * lower-case tag name will be supplied and the input will
			 * contain lower-case tag names, thus normally bypassing
			 * the case comparison code.
			 */
			for ( $i = 0; $i < $this->tag_name_length; $i++ ) {
				$html_char = $this->html[ $this->tag_name_starts_at + $i ];
				$tag_char  = $this->sought_tag_name[ $i ];

				if ( $html_char !== $tag_char && strtoupper( $html_char ) !== $tag_char ) {
					return false;
				}
			}
		}

		if ( null !== $this->sought_class_name && ! $this->has_class( $this->sought_class_name ) ) {
			return false;
		}

		return true;
	}
}