public function process_payment( $order_id ) {
    $order = wc_get_order( $order_id );
    $cart_total = WC()->cart->total;
    // code to capture payment and status
    if(success){
        $order->payment_complete();
        return array(
            'result'  => 'success',
            'redirect'  => $this->get_return_url( $order )
        );
    }
    else{
        wc_add_notice( "Unable to process.", 'error' );
        return array(
            'result'  => 'failure',
            'message' => 'Unable to process.',
        );
    }

}