WP_HTML_Processor::run_adoption_agency_algorithm()

Source

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.' );
}

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