Cron_Runner

class Cron_Runner {
	const START_CRON    = 'bigcommerce_start_import';
	const CONTINUE_CRON = 'bigcommerce_continue_import';

	/**
	 * @return void
	 * @action self::START_CRON
	 */
	public function start_import() {
		$lock = new Lock();
		if ( $lock->get_lock() ) {
			return; // another process has claimed it
		}

		$status  = new Status();
		$current = $status->current_status();
		if ( $current[ 'status' ] !== Status::NOT_STARTED ) {
			return; // it's already running
		}

		$lock->set_lock();
		do_action( 'bigcommerce/import/start' );
		$this->schedule_next();
		$lock->release_lock();
	}

	/**
	 * @return void
	 * @action self::CONTINUE_CRON
	 */
	public function continue_import() {

		$status  = new Status();
		$current = $status->current_status();
		if ( $current[ 'status' ] === Status::NOT_STARTED ) {
			return; // nothing to continue
		}

		$lock = new Lock();
		if ( $lock->get_lock() ) {
			return; // another process has claimed it
		}
		$lock->set_lock();
		do_action( 'bigcommerce/import/before', $current[ 'status' ] );
		do_action( 'bigcommerce/import/run', $current[ 'status' ] );
		do_action( 'bigcommerce/import/after', $current[ 'status' ] );
		$this->schedule_next();
		$lock->release_lock();
	}

	/**
	 * When an ajax request to get the current import status comes in,
	 * run the next step in the process by triggering the scheduled
	 * cron job.
	 *
	 * Runs at priority 5, before the ajax response handler
	 *
	 * @return void
	 * @action Import_Status::AJAX_ACTION_IMPORT_STATUS 5
	 */
	public function ajax_continue_import() {
		try {
			// in case there's already an event scheduled, remove it
			wp_unschedule_hook( self::CONTINUE_CRON );

			// Then fire the action that the cron would have fired on the schedule.
			do_action( self::CONTINUE_CRON );

			// This will have the side effect of scheduling the next run, so the
			// cron can continue to run if the user leaves the page and the Ajax
			// requests stop coming.
		} catch ( \Exception $e ) {
			$message = __( 'The server sent an unexpected response. We’ll keep trying, so dont’t worry. If the problem persists, try turning on error logging in the Diagnostics settings panel.', 'bigcommerce' );
			if ( WP_DEBUG && $e->getMessage() ) {
				$message .= ' ' . sprintf( __( 'Error message: %s', 'bigcommerce' ), $e->getMessage() );
			}
			wp_send_json_error( [
				'code'    => 'internal_server_error',
				'message' => $message,
			], 500 );
		}
	}

	private function schedule_next() {
		$status  = new Status();
		$current = $status->current_status();

		$scheduler = new Cron_Scheduler();
		if ( $current[ 'status' ] === Status::NOT_STARTED ) {
			$scheduler->schedule_next_import();
		} else {
			$scheduler->schedule_next_batch();
		}
	}
}