<?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

 */

final class WP_Hook implements Iterator, ArrayAccess {

	/**

	 * Hook callbacks.

	 *

	 * @since 4.7.0

	 * @var array

	 */

	public $callbacks = 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' => $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 );

		}

		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 = array_keys( $this->callbacks );

		// 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

	 *

	 * @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 ] );

				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

	 *

	 * @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();

		} elseif ( isset( $this->callbacks[ $priority ] ) ) {

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

		}

		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 ] = array_keys( $this->callbacks );

		$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, (int) $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 ] = array_keys( $this->callbacks );

		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 ( is_object( $callback_groups ) && $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;