<?php
/**
* Plugin API: WP_Hook class
*
* @package WordPress
* @subpackage Plugin
* @since 4.7.0
*/

/**
* Core class used to implement action and filter hook functionality.
*
* @since 4.7.0
*
* @see Iterator
* @see ArrayAccess
*/
#[AllowDynamicProperties]
final class WP_Hook implements Iterator, ArrayAccess {

/**
* Hook callbacks.
*
* @since 4.7.0
* @var array
*/
public $callbacks = array();

/**
* Priorities list.
*
* @since 6.4.0
* @var array
*/
protected $priorities = array();

/**
* The priority keys of actively running iterations of a hook.
*
* @since 4.7.0
* @var array
*/
private $iterations = array();

/**
* The current priority of actively running iterations of a hook.
*
* @since 4.7.0
* @var array
*/
private $current_priority = array();

/**
* Number of levels this hook can be recursively called.
*
* @since 4.7.0
* @var int
*/
private $nesting_level = 0;

/**
* Flag for if we're currently doing an action, rather than a filter.
*
* @since 4.7.0
* @var bool
*/
private $doing_action = false;

/**
* Adds a callback function to a filter hook.
*
* @since 4.7.0
*
* @param string $hook_name The name of the filter to add the callback to.
* @param callable $callback The callback to be run when the filter is applied.
* @param int $priority The order in which the functions associated with a particular filter
* are executed. Lower numbers correspond with earlier execution,
* and functions with the same priority are executed in the order
* in which they were added to the filter.
* @param int $accepted_args The number of arguments the function accepts.
*/
public function add_filter( $hook_name, $callback, $priority, $accepted_args ) {
$idx = _wp_filter_build_unique_id( $hook_name, $callback, $priority );

$priority_existed = isset( $this->callbacks[ $priority ] );

$this->callbacks[ $priority ][ $idx ] = array(
'function' => $callback,
'accepted_args' => (int) $accepted_args,
);

// If we're adding a new priority to the list, put them back in sorted order.
if ( ! $priority_existed && count( $this->callbacks ) > 1 ) {
ksort( $this->callbacks, SORT_NUMERIC );
}

$this->priorities = array_keys( $this->callbacks );

if ( $this->nesting_level > 0 ) {
$this->resort_active_iterations( $priority, $priority_existed );
}
}

/**
* Handles resetting callback priority keys mid-iteration.
*
* @since 4.7.0
*
* @param false|int $new_priority Optional. The priority of the new filter being added. Default false,
* for no priority being added.
* @param bool $priority_existed Optional. Flag for whether the priority already existed before the new
* filter was added. Default false.
*/
private function resort_active_iterations( $new_priority = false, $priority_existed = false ) {
$new_priorities = $this->priorities;

// If there are no remaining hooks, clear out all running iterations.
if ( ! $new_priorities ) {
foreach ( $this->iterations as $index => $iteration ) {
$this->iterations[ $index ] = $new_priorities;
}

return;
}

$min = min( $new_priorities );

foreach ( $this->iterations as $index => &$iteration ) {
$current = current( $iteration );

// If we're already at the end of this iteration, just leave the array pointer where it is.
if ( false === $current ) {
continue;
}

$iteration = $new_priorities;

if ( $current < $min ) {
array_unshift( $iteration, $current );
continue;
}

while ( current( $iteration ) < $current ) {
if ( false === next( $iteration ) ) {
break;
}
}

// If we have a new priority that didn't exist, but ::apply_filters() or ::do_action() thinks it's the current priority...
if ( $new_priority === $this->current_priority[ $index ] && ! $priority_existed ) {
/*
* ...and the new priority is the same as what $this->iterations thinks is the previous
* priority, we need to move back to it.
*/

if ( false === current( $iteration ) ) {
// If we've already moved off the end of the array, go back to the last element.
$prev = end( $iteration );
} else {
// Otherwise, just go back to the previous element.
$prev = prev( $iteration );
}

if ( false === $prev ) {
// Start of the array. Reset, and go about our day.
reset( $iteration );
} elseif ( $new_priority !== $prev ) {
// Previous wasn't the same. Move forward again.
next( $iteration );
}
}
}

unset( $iteration );
}

/**
* Removes a callback function from a filter hook.
*
* @since 4.7.0
*
* @param string $hook_name The filter hook to which the function to be removed is hooked.
* @param callable|string|array $callback The callback to be removed from running when the filter is applied.
* This method can be called unconditionally to speculatively remove
* a callback that may or may not exist.
* @param int $priority The exact priority used when adding the original filter callback.
* @return bool Whether the callback existed before it was removed.
*/
public function remove_filter( $hook_name, $callback, $priority ) {
$function_key = _wp_filter_build_unique_id( $hook_name, $callback, $priority );

$exists = isset( $this->callbacks[ $priority ][ $function_key ] );

if ( $exists ) {
unset( $this->callbacks[ $priority ][ $function_key ] );

if ( ! $this->callbacks[ $priority ] ) {
unset( $this->callbacks[ $priority ] );

$this->priorities = array_keys( $this->callbacks );

if ( $this->nesting_level > 0 ) {
$this->resort_active_iterations();
}
}
}

return $exists;
}

/**
* Checks if a specific callback has been registered for this hook.
*
* When using the `$callback` argument, this function may return a non-boolean value
* that evaluates to false (e.g. 0), so use the `===` operator for testing the return value.
*
* @since 4.7.0
*
* @param string $hook_name Optional. The name of the filter hook. Default empty.
* @param callable|string|array|false $callback Optional. The callback to check for.
* This method can be called unconditionally to speculatively check
* a callback that may or may not exist. Default false.
* @return bool|int If `$callback` is omitted, returns boolean for whether the hook has
* anything registered. When checking a specific function, the priority
* of that hook is returned, or false if the function is not attached.
*/
public function has_filter( $hook_name = '', $callback = false ) {
if ( false === $callback ) {
return $this->has_filters();
}

$function_key = _wp_filter_build_unique_id( $hook_name, $callback, false );

if ( ! $function_key ) {
return false;
}

foreach ( $this->callbacks as $priority => $callbacks ) {
if ( isset( $callbacks[ $function_key ] ) ) {
return $priority;
}
}

return false;
}

/**
* Checks if any callbacks have been registered for this hook.
*
* @since 4.7.0
*
* @return bool True if callbacks have been registered for the current hook, otherwise false.
*/
public function has_filters() {
foreach ( $this->callbacks as $callbacks ) {
if ( $callbacks ) {
return true;
}
}

return false;
}

/**
* Removes all callbacks from the current filter.
*
* @since 4.7.0
*
* @param int|false $priority Optional. The priority number to remove. Default false.
*/
public function remove_all_filters( $priority = false ) {
if ( ! $this->callbacks ) {
return;
}

if ( false === $priority ) {
$this->callbacks = array();
$this->priorities = array();
} elseif ( isset( $this->callbacks[ $priority ] ) ) {
unset( $this->callbacks[ $priority ] );
$this->priorities = array_keys( $this->callbacks );
}

if ( $this->nesting_level > 0 ) {
$this->resort_active_iterations();
}
}

/**
* Calls the callback functions that have been added to a filter hook.
*
* @since 4.7.0
*
* @param mixed $value The value to filter.
* @param array $args Additional parameters to pass to the callback functions.
* This array is expected to include $value at index 0.
* @return mixed The filtered value after all hooked functions are applied to it.
*/
public function apply_filters( $value, $args ) {
if ( ! $this->callbacks ) {
return $value;
}

$nesting_level = $this->nesting_level++;

$this->iterations[ $nesting_level ] = $this->priorities;

$num_args = count( $args );

do {
$this->current_priority[ $nesting_level ] = current( $this->iterations[ $nesting_level ] );

$priority = $this->current_priority[ $nesting_level ];

foreach ( $this->callbacks[ $priority ] as $the_ ) {
if ( ! $this->doing_action ) {
$args[0] = $value;
}

// Avoid the array_slice() if possible.
if ( 0 === $the_['accepted_args'] ) {
$value = call_user_func( $the_['function'] );
} elseif ( $the_['accepted_args'] >= $num_args ) {
$value = call_user_func_array( $the_['function'], $args );
} else {
$value = call_user_func_array( $the_['function'], array_slice( $args, 0, $the_['accepted_args'] ) );
}
}
} while ( false !== next( $this->iterations[ $nesting_level ] ) );

unset( $this->iterations[ $nesting_level ] );
unset( $this->current_priority[ $nesting_level ] );

--$this->nesting_level;

return $value;
}

/**
* Calls the callback functions that have been added to an action hook.
*
* @since 4.7.0
*
* @param array $args Parameters to pass to the callback functions.
*/
public function do_action( $args ) {
$this->doing_action = true;
$this->apply_filters( '', $args );

// If there are recursive calls to the current action, we haven't finished it until we get to the last one.
if ( ! $this->nesting_level ) {
$this->doing_action = false;
}
}

/**
* Processes the functions hooked into the 'all' hook.
*
* @since 4.7.0
*
* @param array $args Arguments to pass to the hook callbacks. Passed by reference.
*/
public function do_all_hook( &$args ) {
$nesting_level = $this->nesting_level++;
$this->iterations[ $nesting_level ] = $this->priorities;

do {
$priority = current( $this->iterations[ $nesting_level ] );

foreach ( $this->callbacks[ $priority ] as $the_ ) {
call_user_func_array( $the_['function'], $args );
}
} while ( false !== next( $this->iterations[ $nesting_level ] ) );

unset( $this->iterations[ $nesting_level ] );
--$this->nesting_level;
}

/**
* Return the current priority level of the currently running iteration of the hook.
*
* @since 4.7.0
*
* @return int|false If the hook is running, return the current priority level.
* If it isn't running, return false.
*/
public function current_priority() {
if ( false === current( $this->iterations ) ) {
return false;
}

return current( current( $this->iterations ) );
}

/**
* Normalizes filters set up before WordPress has initialized to WP_Hook objects.
*
* The `$filters` parameter should be an array keyed by hook name, with values
* containing either:
*
* - A `WP_Hook` instance
* - An array of callbacks keyed by their priorities
*
* Examples:
*
* $filters = array(
* 'wp_fatal_error_handler_enabled' => array(
* 10 => array(
* array(
* 'accepted_args' => 0,
* 'function' => function() {
* return false;
* },
* ),
* ),
* ),
* );
*
* @since 4.7.0
*
* @param array $filters Filters to normalize. See documentation above for details.
* @return WP_Hook[] Array of normalized filters.
*/
public static function build_preinitialized_hooks( $filters ) {
/** @var WP_Hook[] $normalized */
$normalized = array();

foreach ( $filters as $hook_name => $callback_groups ) {
if ( $callback_groups instanceof WP_Hook ) {
$normalized[ $hook_name ] = $callback_groups;
continue;
}

$hook = new WP_Hook();

// Loop through callback groups.
foreach ( $callback_groups as $priority => $callbacks ) {

// Loop through callbacks.
foreach ( $callbacks as $cb ) {
$hook->add_filter( $hook_name, $cb['function'], $priority, $cb['accepted_args'] );
}
}

$normalized[ $hook_name ] = $hook;
}

return $normalized;
}

/**
* Determines whether an offset value exists.
*
* @since 4.7.0
*
* @link https://www.php.net/manual/en/arrayaccess.offsetexists.php
*
* @param mixed $offset An offset to check for.
* @return bool True if the offset exists, false otherwise.
*/
#[ReturnTypeWillChange]
public function offsetExists( $offset ) {
return isset( $this->callbacks[ $offset ] );
}

/**
* Retrieves a value at a specified offset.
*
* @since 4.7.0
*
* @link https://www.php.net/manual/en/arrayaccess.offsetget.php
*
* @param mixed $offset The offset to retrieve.
* @return mixed If set, the value at the specified offset, null otherwise.
*/
#[ReturnTypeWillChange]
public function offsetGet( $offset ) {
return isset( $this->callbacks[ $offset ] ) ? $this->callbacks[ $offset ] : null;
}

/**
* Sets a value at a specified offset.
*
* @since 4.7.0
*
* @link https://www.php.net/manual/en/arrayaccess.offsetset.php
*
* @param mixed $offset The offset to assign the value to.
* @param mixed $value The value to set.
*/
#[ReturnTypeWillChange]
public function offsetSet( $offset, $value ) {
if ( is_null( $offset ) ) {
$this->callbacks[] = $value;
} else {
$this->callbacks[ $offset ] = $value;
}

$this->priorities = array_keys( $this->callbacks );
}

/**
* Unsets a specified offset.
*
* @since 4.7.0
*
* @link https://www.php.net/manual/en/arrayaccess.offsetunset.php
*
* @param mixed $offset The offset to unset.
*/
#[ReturnTypeWillChange]
public function offsetUnset( $offset ) {
unset( $this->callbacks[ $offset ] );
$this->priorities = array_keys( $this->callbacks );
}

/**
* Returns the current element.
*
* @since 4.7.0
*
* @link https://www.php.net/manual/en/iterator.current.php
*
* @return array Of callbacks at current priority.
*/
#[ReturnTypeWillChange]
public function current() {
return current( $this->callbacks );
}

/**
* Moves forward to the next element.
*
* @since 4.7.0
*
* @link https://www.php.net/manual/en/iterator.next.php
*
* @return array Of callbacks at next priority.
*/
#[ReturnTypeWillChange]
public function next() {
return next( $this->callbacks );
}

/**
* Returns the key of the current element.
*
* @since 4.7.0
*
* @link https://www.php.net/manual/en/iterator.key.php
*
* @return mixed Returns current priority on success, or NULL on failure
*/
#[ReturnTypeWillChange]
public function key() {
return key( $this->callbacks );
}

/**
* Checks if current position is valid.
*
* @since 4.7.0
*
* @link https://www.php.net/manual/en/iterator.valid.php
*
* @return bool Whether the current position is valid.
*/
#[ReturnTypeWillChange]
public function valid() {
return key( $this->callbacks ) !== null;
}

/**
* Rewinds the Iterator to the first element.
*
* @since 4.7.0
*
* @link https://www.php.net/manual/en/iterator.rewind.php
*/
#[ReturnTypeWillChange]
public function rewind() {
reset( $this->callbacks );
}
}