$crons );
}

/**
 * Reschedule a recurring event.
 *
 * @since 2.1.0
 *
 * @param int $timestamp Unix timestamp (UTC) for when to run the event.
 * @param string $recurrence How often the event should recur.
 * @param string $hook Action hook to execute when event is run.
 * @param array $args Optional. Arguments to pass to the hook's callback function.
 * @return false|void False if the event does not get rescheduled.
 */
function wp_reschedule_event( $timestamp, $recurrence, $hook, $args = array() ) {
	// Make sure timestamp is a positive integer
	if ( ! is_numeric( $timestamp ) || $timestamp <= 0 ) {
		return false;
	}

	$crons = _get_cron_array();
	$schedules = wp_get_schedules();
	$key = md5( serialize( $args ) );
	$interval = 0;

	// First we try to get it from the schedule
	if ( isset( $schedules[ $recurrence ] ) ) {
		$interval = $schedules[ $recurrence ]['interval'];
	}
	// Now we try to get it from the saved interval in case the schedule disappears
	if ( 0 == $interval ) {
		$interval = $crons[ $timestamp ][ $hook ][ $key ]['interval'];
	}
	// Now we assume something is wrong and fail to schedule
	if ( 0 == $interval ) {
		return false;
	}

	$now = time();

	if ( $timestamp >= $now ) {
		$timestamp = $now + $interval;
	} else {
		$timestamp = $now + ( $interval - ( ( $now - $timestamp ) % $interval ) );
	}

	wp_schedule_event( $timestamp, $recurrence, $hook, $args );
}

/**
 * Unschedule a previously scheduled event.
 *
 * The $timestamp and $hook parameters are required so that the event can be
 * identified.
 *
 * @since 2.1.0
 *
 * @param int $timestamp Unix timestamp (UTC) for when to run the event.
 * @param string $hook Action hook, the execution of which will be unscheduled.
 * @param array $args Arguments to pass to the hook's callback function.
 * Although not passed to a callback function, these arguments are used
 * to uniquely identify the scheduled event, so they should be the same
 * as those used when originally scheduling the event.
 * @return false|void False if the event does not get unscheduled.
 */
function wp_unschedule_event( $timestamp, $hook, $args = array() ) {
	// Make sure timestamp is a positive integer
	if ( ! is_numeric( $timestamp ) || $timestamp <= 0 ) {
		return false;
	}

	$crons = _get_cron_array();
	$key = md5(serialize($args));
	unset( $crons[$timestamp][$hook][$key] );
	if ( empty($crons[$timestamp][$hook]) )
		unset( $crons[$timestamp][$hook] );
	if ( empty($crons[$timestamp]) )
		unset( $crons[$timestamp] );
	_set_cron_array( $crons );
}

/**
 * Unschedules all events attached to the hook with the specified arguments.
 *
 * @since 2.1.0
 *
 * @param string $hook Action hook, the execution of which will be unscheduled.
 * @param array $args Optional. Arguments that were to be passed to the hook's callback function.
 */
function wp_clear_scheduled_hook( $hook, $args = array() ) {
	// Backward compatibility
	// Previously this function took the arguments as discrete vars rather than an array like the rest of the API
	if ( !is_array($args) ) {
		_deprecated_argument( __FUNCTION__, '3.0.0', __('This argument has changed to an array to match the behavior of the other cron functions.') );
		$args = array_slice( func_get_args(), 1 );
	}

	// This logic duplicates wp_next_scheduled()
	// It's required due to a scenario where wp_unschedule_event() fails due to update_option() failing,
	// and, wp_next_scheduled() returns the same schedule in an infinite loop.
	$crons = _get_cron_array();
	if ( empty( $crons ) )
		return;

	$key = md5( serialize( $args ) );
	foreach ( $crons as $timestamp => $cron ) {
		if ( isset( $cron[ $hook ][ $key ] ) ) {
			wp_unschedule_event( $timestamp, $hook, $args );
		}
	}
}

/**
 * Unschedules all events attached to the hook.
 *
 * Can be useful for plugins when deactivating to clean up the cron queue.
 *
 * @since 4.9.0
 *
 * @param string $hook Action hook, the execution of which will be unscheduled.
 */
function wp_unschedule_hook( $hook ) {
	$crons = _get_cron_array();

	foreach( $crons as $timestamp => $args ) {
		unset( $crons[ $timestamp ][ $hook ] );

		if ( empty( $crons[ $timestamp ] ) ) {
			unset( $crons[ $timestamp ] );
		}
	}

	_set_cron_array( $crons );
}

/**
 * Retrieve the next timestamp for an event.
 *
 * @since 2.1.0
 *
 * @param string $hook Action hook to execute when event is run.
 * @param array $args Optional. Arguments to pass to the hook's callback function.
 * @return false|int The Unix timestamp of the next time the scheduled event will occur.
 */
function wp_next_scheduled( $hook, $args = array() ) {
	$crons = _get_cron_array();
	$key = md5(serialize($args));
	if ( empty($crons) )
		return false;
	foreach ( $crons as $timestamp => $cron ) {
		if ( isset( $cron[$hook][$key] ) )
			return $timestamp;
	}
	return false;
}

/**
 * Sends a request to run cron through HTTP request that doesn't halt page loading.
 *
 * @since 2.1.0
 *
 * @param int $gmt_time Optional. Unix timestamp (UTC). Default 0 (current time is used).
 */
function spawn_cron( $gmt_time = 0 ) {
	if ( ! $gmt_time )
		$gmt_time = microtime( true );

	if ( defined('DOING_CRON') || isset($_GET['doing_wp_cron']) )
		return;

	/*
	 * Get the cron lock, which is a Unix timestamp of when the last cron was spawned
	 * and has not finished running.
	 *
	 * Multiple processes on multiple web servers can run this code concurrently,
	 * this lock attempts to make spawning as atomic as possible.
	 */
	$lock = get_transient('doing_cron');

	if ( $lock > $gmt_time + 10 * MINUTE_IN_SECONDS )
		$lock = 0;

	// don't run if another process is currently running it or more than once every 60 sec.
	if ( $lock + WP_CRON_LOCK_TIMEOUT > $gmt_time )
		return;

	//sanity check
	$crons = _get_cron_array();
	if ( !is_array($crons) )
		return;

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

	if ( defined( 'ALTERNATE_WP_CRON' ) && ALTERNATE_WP_CRON ) {
		if ( 'GET' !== $_SERVER['REQUEST_METHOD'] || defined( 'DOING_AJAX' ) ||  defined( 'XMLRPC_REQUEST' ) ) {
			return;
		}

		$doing_wp_cron = sprintf( '%.22F', $gmt_time );
		set_transient( 'doing_cron', $doing_wp_cron );

		ob_start();
		wp_redirect( add_query_arg( 'doing_wp_cron', $doing_wp_cron, wp_unslash( $_SERVER['REQUEST_URI'] ) ) );
		echo ' ';

		// flush any buffers and send the headers
		while ( @ob_end_flush() );
		flush();

		WP_DEBUG ? include_once( ABSPATH . 'wp-cron.php' ) : @include_once( ABSPATH . 'wp-cron.php' );
		return;
	}

	// Set the cron lock with the current unix timestamp, when the cron is being spawned.
	$doing_wp_cron = sprintf( '%.22F', $gmt_time );
	set_transient( 'doing_cron', $doing_wp_cron );

	/**
	 * Filters the cron request arguments.
	 *
	 * @since 3.5.0
	 * @since 4.5.0 The `$doing_wp_cron` parameter was added.
	 *
	 * @param array $cron_request_array {
	 *     An array of cron request URL arguments.
	 *
	 *     @type string $url  The cron request URL.
	 *     @type int    $key  The 22 digit GMT microtime.
	 *     @type array  $args {
	 *         An array of cron request arguments.
	 *
	 *         @type int  $timeout   The request timeout in seconds. Default .01 seconds.
	 *         @type bool $blocking  Whether to set blocking for the request. Default false.
	 *         @type bool $sslverify Whether SSL should be verified for the request. Default false.
	 *     }
	 * }
	 * @param string $doing_wp_cron The unix timestamp of the cron lock.
	 */
	$cron_request = apply_filters( 'cron_request', array(
		'url'  => add_query_arg( 'doing_wp_cron', $doing_wp_cron, site_url( 'wp-cron.php' ) ),
		'key'  => $doing_wp_cron,
		'args' => array(
			'timeout'   => 0.01,
			'blocking'  => false,
			/** This filter is documented in wp-includes/class-wp-http-streams.php */
			'sslverify' => apply_filters( 'https_local_ssl_verify', false )
		)
	), $doing_wp_cron );

	wp_remote_post( $cron_request['url'], $cron_request['args'] );
}

/**
 * Run scheduled callbacks or spawn cron for all scheduled events.
 *
 * @since 2.1.0
 */
function wp_cron() {
	// Prevent infinite loops caused by lack of wp-cron.php
	if ( strpos($_SERVER['REQUEST_URI'], '/wp-cron.php') !== false || ( defined('DISABLE_WP_CRON') && DISABLE_WP_CRON ) )
		return;

	if ( false === $crons = _get_cron_array() )
		return;

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

	$schedules = wp_get_schedules();
	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;
			spawn_cron( $gmt_time );
			break 2;
		}
	}
}

/**
 * Retrieve supported event recurrence schedules.
 *
 * The default supported recurrences are 'hourly', 'twicedaily', and 'daily'. 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 or for
 * example 'weekly'. 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 3600 or 60*60. For weekly, the value would be
 * 60*60*24*7 or 604800. The value of 'interval' would then be 604800.
 *
 * The 'display' is the description. For the 'weekly' key, the 'display' would
 * be `__( 'Once Weekly' )`.
 *
 * For your plugin, you will be passed an array. you can easily add your
 * schedule by doing the following.
 *
 *     // Filter parameter variable name is 'array'.
 *     $array['weekly'] = array(
 *         'interval' => 604800,
 *     	   'display'  => __( 'Once Weekly' )
 *     );
 *
 *
 * @since 2.1.0
 *
 * @return array
 */
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' ) ),
	);
	/**
	 * Filters the non-default cron schedules.
	 *
	 * @since 2.1.0
	 *
	 * @param array $new_schedules An array of non-default cron schedules. Default empty.
	 */
	return array_merge( apply_filters( 'cron_schedules', array() ), $schedules );
}

/**
 * Retrieve the recurrence schedule for an event.
 *
 * @see wp_get_schedules() for available schedules.
 *
 * @since 2.1.0
 *
 * @param string $hook Action hook to identify the event.
 * @param array $args Optional. Arguments passed to the event's callback function.
 * @return string|false False, if no schedule. Schedule name on success.
 */
function wp_get_schedule($hook, $args = array()) {
	$crons = _get_cron_array();
	$key = md5(serialize($args));
	if ( empty($crons) )
		return false;
	foreach ( $crons as $timestamp => $cron ) {
		if ( isset( $cron[$hook][$key] ) )
			return $cron[$hook][$key]['schedule'];
	}
	return false;
}

//
// Private functions
//

/**
 * Retrieve cron info array option.
 *
 * @since 2.1.0
 * @access private
 *
 * @return false|array CRON info array.
 */
function _get_cron_array()  {
	$cron = get_option('cron');
	if ( ! is_array($cron) )
		return false;

	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
 * @access private
 *
 * @param array $cron Cron info array from _get_cron_array().
 */
function _set_cron_array($cron) {
	$cron['version'] = 2;
	update_option( 'cron', $cron );
}

/**
 * Upgrade 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;
}