the
 * {@link https://www.php.net/manual/en/language.types.boolean.php PHP documentation}. Use
 * the `===` operator for testing the return value of this function.
 *
 * @since 2.1.0
 * @since 5.1.0 Return value added to indicate success or failure.
 * @since 5.7.0 Functionality moved to _wp_cron() to which this becomes a wrapper.
 *
 * @return false|int|void On success an integer indicating number of events spawned (0 indicates no
 *                        events needed to be spawned), false if spawning fails for one or more events or
 *                        void if the function registered _wp_cron() to run on the action.
 */
function wp_cron() {
	if ( did_action( 'wp_loaded' ) ) {
		return _wp_cron();
	}

	add_action( 'wp_loaded', '_wp_cron', 20 );
}

/**
 * Runs scheduled callbacks or spawns cron for all scheduled events.
 *
 * Warning: This function may return Boolean FALSE, but may also return a non-Boolean
 * value which evaluates to FALSE. For information about casting to booleans see the
 * {@link https://www.php.net/manual/en/language.types.boolean.php PHP documentation}. Use
 * the `===` operator for testing the return value of this function.
 *
 * @since 5.7.0
 * @access private
 *
 * @return int|false On success an integer indicating number of events spawned (0 indicates no
 *                   events needed to be spawned), false if spawning fails for one or more events.
 */
function _wp_cron() {
	// Prevent infinite loops caused by lack of wp-cron.php.
	if ( str_contains( $_SERVER['REQUEST_URI'], '/wp-cron.php' )
		|| ( defined( 'DISABLE_WP_CRON' ) && DISABLE_WP_CRON )
	) {
		return 0;
	}

	$crons = wp_get_ready_cron_jobs();
	if ( empty( $crons ) ) {
		return 0;
	}

	$gmt_time = microtime( true );
	$keys     = array_keys( $crons );
	if ( isset( $keys[0] ) && $keys[0] > $gmt_time ) {
		return 0;
	}

	$schedules = wp_get_schedules();
	$results   = array();

	foreach ( $crons as $timestamp => $cronhooks ) {
		if ( $timestamp > $gmt_time ) {
			break;
		}

		foreach ( (array) $cronhooks as $hook => $args ) {
			if ( isset( $schedules[ $hook ]['callback'] )
				&& ! call_user_func( $schedules[ $hook ]['callback'] )
			) {
				continue;
			}

			$results[] = spawn_cron( $gmt_time );
			break 2;
		}
	}

	if ( in_array( false, $results, true ) ) {
		return false;
	}

	return count( $results );
}

/**
 * Retrieves supported event recurrence schedules.
 *
 * The default supported recurrences are 'hourly', 'twicedaily', 'daily', and 'weekly'.
 * A plugin may add more by hooking into the {@see 'cron_schedules'} filter.
 * The filter accepts an array of arrays. The outer array has a key that is the name
 * of the schedule, for example 'monthly'. The value is an array with two keys,
 * one is 'interval' and the other is 'display'.
 *
 * The 'interval' is a number in seconds of when the cron job should run.
 * So for 'hourly' the time is `HOUR_IN_SECONDS` (`60 * 60` or `3600`). For 'monthly',
 * the value would be `MONTH_IN_SECONDS` (`30 * 24 * 60 * 60` or `2592000`).
 *
 * The 'display' is the description. For the 'monthly' key, the 'display'
 * would be `__( 'Once Monthly' )`.
 *
 * For your plugin, you will be passed an array. You can add your
 * schedule by doing the following:
 *
 *     // Filter parameter variable name is 'array'.
 *     $array['monthly'] = array(
 *         'interval' => MONTH_IN_SECONDS,
 *         'display'  => __( 'Once Monthly' )
 *     );
 *
 * @since 2.1.0
 * @since 5.4.0 The 'weekly' schedule was added.
 *
 * @return array {
 *     The array of cron schedules keyed by the schedule name.
 *
 *     @type array ...$0 {
 *         Cron schedule information.
 *
 *         @type int    $interval The schedule interval in seconds.
 *         @type string $display  The schedule display name.
 *     }
 * }
 */
function wp_get_schedules() {
	$schedules = array(
		'hourly'     => array(
			'interval' => HOUR_IN_SECONDS,
			'display'  => __( 'Once Hourly' ),
		),
		'twicedaily' => array(
			'interval' => 12 * HOUR_IN_SECONDS,
			'display'  => __( 'Twice Daily' ),
		),
		'daily'      => array(
			'interval' => DAY_IN_SECONDS,
			'display'  => __( 'Once Daily' ),
		),
		'weekly'     => array(
			'interval' => WEEK_IN_SECONDS,
			'display'  => __( 'Once Weekly' ),
		),
	);

	/**
	 * Filters the non-default cron schedules.
	 *
	 * @since 2.1.0
	 *
	 * @param array $new_schedules {
	 *     An array of non-default cron schedules keyed by the schedule name. Default empty array.
	 *
	 *     @type array ...$0 {
	 *         Cron schedule information.
	 *
	 *         @type int    $interval The schedule interval in seconds.
	 *         @type string $display  The schedule display name.
	 *     }
	 * }
	 */
	return array_merge( apply_filters( 'cron_schedules', array() ), $schedules );
}

/**
 * Retrieves the name of the recurrence schedule for an event.
 *
 * @see wp_get_schedules() for available schedules.
 *
 * @since 2.1.0
 * @since 5.1.0 {@see 'get_schedule'} filter added.
 *
 * @param string $hook Action hook to identify the event.
 * @param array  $args Optional. Arguments passed to the event's callback function.
 *                     Default empty array.
 * @return string|false Schedule name on success, false if no schedule.
 */
function wp_get_schedule( $hook, $args = array() ) {
	$schedule = false;
	$event    = wp_get_scheduled_event( $hook, $args );

	if ( $event ) {
		$schedule = $event->schedule;
	}

	/**
	 * Filters the schedule name for a hook.
	 *
	 * @since 5.1.0
	 *
	 * @param string|false $schedule Schedule for the hook. False if not found.
	 * @param string       $hook     Action hook to execute when cron is run.
	 * @param array        $args     Arguments to pass to the hook's callback function.
	 */
	return apply_filters( 'get_schedule', $schedule, $hook, $args );
}

/**
 * Retrieves cron jobs ready to be run.
 *
 * Returns the results of _get_cron_array() limited to events ready to be run,
 * ie, with a timestamp in the past.
 *
 * @since 5.1.0
 *
 * @return array[] Array of cron job arrays ready to be run.
 */
function wp_get_ready_cron_jobs() {
	/**
	 * Filter to override retrieving ready cron jobs.
	 *
	 * Returning an array will short-circuit the normal retrieval of ready
	 * cron jobs, causing the function to return the filtered value instead.
	 *
	 * @since 5.1.0
	 *
	 * @param null|array[] $pre Array of ready cron tasks to return instead. Default null
	 *                          to continue using results from _get_cron_array().
	 */
	$pre = apply_filters( 'pre_get_ready_cron_jobs', null );

	if ( null !== $pre ) {
		return $pre;
	}

	$crons    = _get_cron_array();
	$gmt_time = microtime( true );
	$results  = array();

	foreach ( $crons as $timestamp => $cronhooks ) {
		if ( $timestamp > $gmt_time ) {
			break;
		}

		$results[ $timestamp ] = $cronhooks;
	}

	return $results;
}

//
// Private functions.
//

/**
 * Retrieves cron info array option.
 *
 * @since 2.1.0
 * @since 6.1.0 Return type modified to consistently return an array.
 * @access private
 *
 * @return array[] Array of cron events.
 */
function _get_cron_array() {
	$cron = get_option( 'cron' );
	if ( ! is_array( $cron ) ) {
		return array();
	}

	if ( ! isset( $cron['version'] ) ) {
		$cron = _upgrade_cron_array( $cron );
	}

	unset( $cron['version'] );

	return $cron;
}

/**
 * Updates the cron option with the new cron array.
 *
 * @since 2.1.0
 * @since 5.1.0 Return value modified to outcome of update_option().
 * @since 5.7.0 The `$wp_error` parameter was added.
 *
 * @access private
 *
 * @param array[] $cron     Array of cron info arrays from _get_cron_array().
 * @param bool    $wp_error Optional. Whether to return a WP_Error on failure. Default false.
 * @return bool|WP_Error True if cron array updated. False or WP_Error on failure.
 */
function _set_cron_array( $cron, $wp_error = false ) {
	if ( ! is_array( $cron ) ) {
		$cron = array();
	}

	$cron['version'] = 2;

	$result = update_option( 'cron', $cron );

	if ( $wp_error && ! $result ) {
		return new WP_Error(
			'could_not_set',
			__( 'The cron event list could not be saved.' )
		);
	}

	return $result;
}

/**
 * Upgrades a cron info array.
 *
 * This function upgrades the cron info array to version 2.
 *
 * @since 2.1.0
 * @access private
 *
 * @param array $cron Cron info array from _get_cron_array().
 * @return array An upgraded cron info array.
 */
function _upgrade_cron_array( $cron ) {
	if ( isset( $cron['version'] ) && 2 === $cron['version'] ) {
		return $cron;
	}

	$new_cron = array();

	foreach ( (array) $cron as $timestamp => $hooks ) {
		foreach ( (array) $hooks as $hook => $args ) {
			$key = md5( serialize( $args['args'] ) );

			$new_cron[ $timestamp ][ $hook ][ $key ] = $args;
		}
	}

	$new_cron['version'] = 2;

	update_option( 'cron', $new_cron );

	return $new_cron;
}