private List<Stock> getExpiringStockMap(List<Stock> stocks) {
        Map<String, Stock> stockMap = new HashMap<>();
        for (Stock stock : stocks) {
            long notificationDate = DateUtils.subtractDays(stock.getExpirationDate(), stock.getDaysUntilNotif());
            if (DateUtils.onOrBeforeDate(notificationDate, now())) {
                if (stockMap.containsKey(stock.getSupplyCode())) {
                    Stock oldStock = stockMap.get(stock.getSupplyCode());
                    if (oldStock.getExpirationDate() < stock.getExpirationDate()) {
                        stockMap.put(stock.getSupplyCode(), oldStock);
                    } else {
                        stockMap.put(stock.getSupplyCode(), stock);
                    }
                } else {
                    stockMap.put(stock.getSupplyCode(), stock);
                }
            }
        }
        return new ArrayList<>(stockMap.values());
    }