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<?php
/**
* HTML API: WP_HTML_Open_Elements class
*
* @package WordPress
* @subpackage HTML-API
* @since 6.4.0
*/
/**
* Core class used by the HTML processor during HTML parsing
* for managing the stack of open elements.
*
* This class is designed for internal use by the HTML processor.
*
* > Initially, the stack of open elements is empty. The stack grows
* > downwards; the topmost node on the stack is the first one added
* > to the stack, and the bottommost node of the stack is the most
* > recently added node in the stack (notwithstanding when the stack
* > is manipulated in a random access fashion as part of the handling
* > for misnested tags).
*
* @since 6.4.0
*
* @access private
*
* @see https://html.spec.whatwg.org/#stack-of-open-elements
* @see WP_HTML_Processor
*/
class WP_HTML_Open_Elements {
/**
* Holds the stack of open element references.
*
* @since 6.4.0
*
* @var WP_HTML_Token[]
*/
public $stack = array();
/**
* Whether a P element is in button scope currently.
*
* This class optimizes scope lookup by pre-calculating
* this value when elements are added and removed to the
* stack of open elements which might change its value.
* This avoids frequent iteration over the stack.
*
* @since 6.4.0
*
* @var bool
*/
private $has_p_in_button_scope = false;
/**
* Reports if a specific node is in the stack of open elements.
*
* @since 6.4.0
*
* @param WP_HTML_Token $token Look for this node in the stack.
* @return bool Whether the referenced node is in the stack of open elements.
*/
public function contains_node( $token ) {
foreach ( $this->walk_up() as $item ) {
if ( $token->bookmark_name === $item->bookmark_name ) {
return true;
}
}
return false;
}
/**
* Returns how many nodes are currently in the stack of open elements.
*
* @since 6.4.0
*
* @return int How many node are in the stack of open elements.
*/
public function count() {
return count( $this->stack );
}
/**
* Returns the node at the end of the stack of open elements,
* if one exists. If the stack is empty, returns null.
*
* @since 6.4.0
*
* @return WP_HTML_Token|null Last node in the stack of open elements, if one exists, otherwise null.
*/
public function current_node() {
$current_node = end( $this->stack );
return $current_node ? $current_node : null;
}
/**
* Returns whether an element is in a specific scope.
*
* ## HTML Support
*
* This function skips checking for the termination list because there
* are no supported elements which appear in the termination list.
*
* @since 6.4.0
*
* @see https://html.spec.whatwg.org/#has-an-element-in-the-specific-scope
*
* @param string $tag_name Name of tag check.
* @param string[] $termination_list List of elements that terminate the search.
* @return bool Whether the element was found in a specific scope.
*/
public function has_element_in_specific_scope( $tag_name, $termination_list ) {
foreach ( $this->walk_up() as $node ) {
if ( $node->node_name === $tag_name ) {
return true;
}
switch ( $node->node_name ) {
case 'HTML':
return false;
}
if ( in_array( $node->node_name, $termination_list, true ) ) {
return true;
}
}
return false;
}
/**
* Returns whether a particular element is in scope.
*
* @since 6.4.0
*
* @see https://html.spec.whatwg.org/#has-an-element-in-scope
*
* @param string $tag_name Name of tag to check.
* @return bool Whether given element is in scope.
*/
public function has_element_in_scope( $tag_name ) {
return $this->has_element_in_specific_scope(
$tag_name,
array(
/*
* Because it's not currently possible to encounter
* one of the termination elements, they don't need
* to be listed here. If they were, they would be
* unreachable and only waste CPU cycles while
* scanning through HTML.
*/
)
);
}
/**
* Returns whether a particular element is in list item scope.
*
* @since 6.4.0
*
* @see https://html.spec.whatwg.org/#has-an-element-in-list-item-scope
*
* @throws WP_HTML_Unsupported_Exception Always until this function is implemented.
*
* @param string $tag_name Name of tag to check.
* @return bool Whether given element is in scope.
*/
public function has_element_in_list_item_scope( $tag_name ) {
throw new WP_HTML_Unsupported_Exception( 'Cannot process elements depending on list item scope.' );
return false; // The linter requires this unreachable code until the function is implemented and can return.
}
/**
* Returns whether a particular element is in button scope.
*
* @since 6.4.0
*
* @see https://html.spec.whatwg.org/#has-an-element-in-button-scope
*
* @param string $tag_name Name of tag to check.
* @return bool Whether given element is in scope.
*/
public function has_element_in_button_scope( $tag_name ) {
return $this->has_element_in_specific_scope( $tag_name, array( 'BUTTON' ) );
}
/**
* Returns whether a particular element is in table scope.
*
* @since 6.4.0
*
* @see https://html.spec.whatwg.org/#has-an-element-in-table-scope
*
* @throws WP_HTML_Unsupported_Exception Always until this function is implemented.
*
* @param string $tag_name Name of tag to check.
* @return bool Whether given element is in scope.
*/
public function has_element_in_table_scope( $tag_name ) {
throw new WP_HTML_Unsupported_Exception( 'Cannot process elements depending on table scope.' );
return false; // The linter requires this unreachable code until the function is implemented and can return.
}
/**
* Returns whether a particular element is in select scope.
*
* @since 6.4.0
*
* @see https://html.spec.whatwg.org/#has-an-element-in-select-scope
*
* @throws WP_HTML_Unsupported_Exception Always until this function is implemented.
*
* @param string $tag_name Name of tag to check.
* @return bool Whether given element is in scope.
*/
public function has_element_in_select_scope( $tag_name ) {
throw new WP_HTML_Unsupported_Exception( 'Cannot process elements depending on select scope.' );
return false; // The linter requires this unreachable code until the function is implemented and can return.
}
/**
* Returns whether a P is in BUTTON scope.
*
* @since 6.4.0
*
* @see https://html.spec.whatwg.org/#has-an-element-in-button-scope
*
* @return bool Whether a P is in BUTTON scope.
*/
public function has_p_in_button_scope() {
return $this->has_p_in_button_scope;
}
/**
* Pops a node off of the stack of open elements.
*
* @since 6.4.0
*
* @see https://html.spec.whatwg.org/#stack-of-open-elements
*
* @return bool Whether a node was popped off of the stack.
*/
public function pop() {
$item = array_pop( $this->stack );
if ( null === $item ) {
return false;
}
$this->after_element_pop( $item );
return true;
}
/**
* Pops nodes off of the stack of open elements until one with the given tag name has been popped.
*
* @since 6.4.0
*
* @see WP_HTML_Open_Elements::pop
*
* @param string $tag_name Name of tag that needs to be popped off of the stack of open elements.
* @return bool Whether a tag of the given name was found and popped off of the stack of open elements.
*/
public function pop_until( $tag_name ) {
foreach ( $this->walk_up() as $item ) {
$this->pop();
if ( $tag_name === $item->node_name ) {
return true;
}
}
return false;
}
/**
* Pushes a node onto the stack of open elements.
*
* @since 6.4.0
*
* @see https://html.spec.whatwg.org/#stack-of-open-elements
*
* @param WP_HTML_Token $stack_item Item to add onto stack.
*/
public function push( $stack_item ) {
$this->stack[] = $stack_item;
$this->after_element_push( $stack_item );
}
/**
* Removes a specific node from the stack of open elements.
*
* @since 6.4.0
*
* @param WP_HTML_Token $token The node to remove from the stack of open elements.
* @return bool Whether the node was found and removed from the stack of open elements.
*/
public function remove_node( $token ) {
foreach ( $this->walk_up() as $position_from_end => $item ) {
if ( $token->bookmark_name !== $item->bookmark_name ) {
continue;
}
$position_from_start = $this->count() - $position_from_end - 1;
array_splice( $this->stack, $position_from_start, 1 );
$this->after_element_pop( $item );
return true;
}
return false;
}
/**
* Steps through the stack of open elements, starting with the top element
* (added first) and walking downwards to the one added last.
*
* This generator function is designed to be used inside a "foreach" loop.
*
* Example:
*
* $html = '<em><strong><a>We are here';
* foreach ( $stack->walk_down() as $node ) {
* echo "{$node->node_name} -> ";
* }
* > EM -> STRONG -> A ->
*
* To start with the most-recently added element and walk towards the top,
* see WP_HTML_Open_Elements::walk_up().
*
* @since 6.4.0
*/
public function walk_down() {
$count = count( $this->stack );
for ( $i = 0; $i < $count; $i++ ) {
yield $this->stack[ $i ];
}
}
/**
* Steps through the stack of open elements, starting with the bottom element
* (added last) and walking upwards to the one added first.
*
* This generator function is designed to be used inside a "foreach" loop.
*
* Example:
*
* $html = '<em><strong><a>We are here';
* foreach ( $stack->walk_up() as $node ) {
* echo "{$node->node_name} -> ";
* }
* > A -> STRONG -> EM ->
*
* To start with the first added element and walk towards the bottom,
* see WP_HTML_Open_Elements::walk_down().
*
* @since 6.4.0
*/
public function walk_up() {
for ( $i = count( $this->stack ) - 1; $i >= 0; $i-- ) {
yield $this->stack[ $i ];
}
}
/*
* Internal helpers.
*/
/**
* Updates internal flags after adding an element.
*
* Certain conditions (such as "has_p_in_button_scope") are maintained here as
* flags that are only modified when adding and removing elements. This allows
* the HTML Processor to quickly check for these conditions instead of iterating
* over the open stack elements upon each new tag it encounters. These flags,
* however, need to be maintained as items are added and removed from the stack.
*
* @since 6.4.0
*
* @param WP_HTML_Token $item Element that was added to the stack of open elements.
*/
public function after_element_push( $item ) {
/*
* When adding support for new elements, expand this switch to trap
* cases where the precalculated value needs to change.
*/
switch ( $item->node_name ) {
case 'BUTTON':
$this->has_p_in_button_scope = false;
break;
case 'P':
$this->has_p_in_button_scope = true;
break;
}
}
/**
* Updates internal flags after removing an element.
*
* Certain conditions (such as "has_p_in_button_scope") are maintained here as
* flags that are only modified when adding and removing elements. This allows
* the HTML Processor to quickly check for these conditions instead of iterating
* over the open stack elements upon each new tag it encounters. These flags,
* however, need to be maintained as items are added and removed from the stack.
*
* @since 6.4.0
*
* @param WP_HTML_Token $item Element that was removed from the stack of open elements.
*/
public function after_element_pop( $item ) {
/*
* When adding support for new elements, expand this switch to trap
* cases where the precalculated value needs to change.
*/
switch ( $item->node_name ) {
case 'BUTTON':
$this->has_p_in_button_scope = $this->has_element_in_button_scope( 'P' );
break;
case 'P':
$this->has_p_in_button_scope = $this->has_element_in_button_scope( 'P' );
break;
}
}
}