WooCommerce ePaybg: Do not allow Pay page reload after customer is sent to ePaybg

wc-epaybg-no-pay-page-reload-after-form-submit

add_action( 'woocommerce_receipt_epaybg', 'vanbo_initiate_epaybg_request_hooks', 9 );
/**
 * Replaces the gateway original action with our own
 */
function vanbo_initiate_epaybg_request_hooks() {
	$gateway = vanbo_get_epaybg_gateway();
	
	if ( false == $gateway ) {
		return;
	}
	
	// Removes the original action
	remove_action( 'woocommerce_receipt_epaybg', array( $gateway, 'receipt_page' ) );
	add_action( 'woocommerce_receipt_epaybg', 'vanbo_epaybg_payment_request_form', 11 );
}

/**
 * Executes the same form action, but skips when the page is loaded with the 'mashsb-refresh' and 'tb-preview' parameters.
 *
 * The page should be loaded only once and any reloading of the page will result in a different invoice number,
 * which in turn will affect the response handling of the gateway. This behavior should not be allowed
 * and that is why we resorted to this workaround
 *
 * @param int $order_id
 */
function vanbo_epaybg_payment_request_form( $order_id ) {
	$gateway = vanbo_get_epaybg_gateway();
	
	if ( false == $gateway ) {
		return;
	}
	
	if ( is_ajax() ) {
		return;
	}
	
	echo '<p>' . __( 'Thank you for your order, please click the button below to pay with ePay.bg.', 'wc_epaybg' ) . '</p>';
	
	echo $gateway->generate_epaybg_form( $order_id );
}

/**
 * @return WC_Gateway_Epaybg|false False will be returned if the gateway is not active on the site.
 */
function vanbo_get_epaybg_gateway() {
	foreach ( WC()->payment_gateways()->payment_gateways() as $gateway ) {
		if ( 'epaybg' == $gateway->id ) {
			return $gateway;
		}
	}
	
	return false;
}