! function_exists( 'as_enqueue_async_action' ) ) {
			return null;
		}

		return as_enqueue_async_action(
			$this->action,
			[ 'tasks_meta_id' => $this->meta_id ],
			Tasks::GROUP
		);
	}

	/**
	 * Register the recurring task.
	 *
	 * @since 1.5.9
	 *
	 * @return null|string Action ID.
	 */
	protected function register_recurring() {

		if ( ! function_exists( 'as_schedule_recurring_action' ) ) {
			return null;
		}

		return as_schedule_recurring_action(
			$this->timestamp,
			$this->interval,
			$this->action,
			[ 'tasks_meta_id' => $this->meta_id ],
			Tasks::GROUP
		);
	}

	/**
	 * Register the one-time task.
	 *
	 * @since 1.5.9
	 *
	 * @return null|string Action ID.
	 */
	protected function register_once() {

		if ( ! function_exists( 'as_schedule_single_action' ) ) {
			return null;
		}

		return as_schedule_single_action(
			$this->timestamp,
			$this->action,
			[ 'tasks_meta_id' => $this->meta_id ],
			Tasks::GROUP
		);
	}

	/**
	 * Cancel all occurrences of this task.
	 *
	 * @since 1.6.1
	 *
	 * @return null|bool|string Null if no matching action found,
	 *                          false if AS library is missing,
	 *                          true if scheduled task has no params,
	 *                          string of the scheduled action ID if a scheduled action was found and unscheduled.
	 */
	public function cancel() {

		if ( ! function_exists( 'as_unschedule_all_actions' ) ) {
			return false;
		}

		if ( $this->params === null ) {
			as_unschedule_all_actions( $this->action );

			return true;
		}

		$this->meta_id = $this->meta->get_meta_id( $this->action, $this->params );

		if ( $this->meta_id === null ) {
			return null;
		}

		return as_unschedule_action( $this->action, [ 'tasks_meta_id' => $this->meta_id ], Tasks::GROUP );
	}
}