DataStore.java

import java.io.*;
import java.nio.file.Files;
import java.nio.file.StandardCopyOption;
import java.time.LocalDate;
import java.util.ArrayList;

public class DataStore {

    private static final String ORDERS_FILE = "orders.csv";
    private static final String CUSTOMERS_FILE = "customers.csv";
    private static final String PAYMENTS_FILE = "payments.csv";

    // ---------------------------- LOAD METHODS ----------------------------

    public OrderManager loadOrders() {
        OrderManager om = new OrderManager();
        File f = new File(ORDERS_FILE);
        if (!f.exists()) return om;

        try (BufferedReader br = new BufferedReader(new FileReader(f))) {
            String line;
            while ((line = br.readLine()) != null) {
                // Format:
                // id,customerID,customerName,phone,email,address,delivery,orderType,status,paymentStatus,amount,method,address
                String[] x = line.split(",");

                Customer c = new Customer(
                        x[1], x[2], x[3], x[4], x[5]
                );

                Order o = new Order(
                        Integer.parseInt(x[0]),
                        c,
                        LocalDate.parse(x[6]),
                        x[7],
                        x[11],
                        x[12],
                        Double.parseDouble(x[10])
                );
                o.setStatus(x[8]);
                o.setPaymentStatus(x[9]);

                om.getOrdersList().add(o);
            }
        } catch (Exception ignored) {}
        return om;
    }

    public CustomerManager loadCustomers() {
        CustomerManager cm = new CustomerManager();
        File f = new File(CUSTOMERS_FILE);
        if (!f.exists()) return cm;

        try (BufferedReader br = new BufferedReader(new FileReader(f))) {
            String line;
            while ((line = br.readLine()) != null) {
                String[] x = line.split(",");
                Customer c = new Customer(x[0], x[1], x[2], x[3], x[4]);
                cm.getCustomersList().add(c);
            }
        } catch (Exception ignored) {}
        return cm;
    }

    public PaymentManager loadPayments() {
        PaymentManager pm = new PaymentManager();
        File f = new File(PAYMENTS_FILE);
        if (!f.exists()) return pm;

        try (BufferedReader br = new BufferedReader(new FileReader(f))) {
            String line;
            while ((line = br.readLine()) != null) {
                String[] x = line.split(",");
                Payment p = new Payment(
                        Integer.parseInt(x[0]),
                        Integer.parseInt(x[1]),
                        x[2],
                        Double.parseDouble(x[3])
                );
                p.setStatus(x[4]);
                pm.getPaymentsList().add(p);
            }
        } catch (Exception ignored) {}
        return pm;
    }

    // ---------------------------- SAVE METHODS ----------------------------

    public void saveOrders(OrderManager om) {
        backup(ORDERS_FILE);

        try (PrintWriter pw = new PrintWriter(new FileWriter(ORDERS_FILE))) {
            for (Order o : om.getOrdersList()) {
                Customer c = o.customer;
                pw.println(
                        o.getOrderID() + "," +
                        c.getCustomerID() + "," +
                        c.getName() + "," +
                        c.getPhoneNumber() + "," +
                        c.getEmail() + "," +
                        c.getAddress() + "," +
                        o.getDeliveryDate() + "," +
                        o.getOrderType() + "," +
                        o.getStatus() + "," +
                        o.getPaymentStatus() + "," +
                        o.totalAmount + "," +
                        o.method + "," +
                        o.address
                );
            }
        } catch (Exception e) { System.out.println("Error saving orders CSV."); }
    }

    public void saveCustomers(CustomerManager cm) {
        backup(CUSTOMERS_FILE);

        try (PrintWriter pw = new PrintWriter(new FileWriter(CUSTOMERS_FILE))) {
            for (Customer c : cm.getCustomersList()) {
                pw.println(c.getCustomerID() + "," +
                           c.getName() + "," +
                           c.getPhoneNumber() + "," +
                           c.getEmail() + "," +
                           c.getAddress());
            }
        } catch (Exception ignored) {}
    }

    public void savePayments(PaymentManager pm) {
        backup(PAYMENTS_FILE);

        try (PrintWriter pw = new PrintWriter(new FileWriter(PAYMENTS_FILE))) {
            for (Payment p : pm.getPaymentsList()) {
                pw.println(p.getPaymentID() + "," +
                           p.getOrderID() + "," +
                           p.method + "," +
                           p.amount + "," +
                           p.status);
            }
        } catch (Exception ignored) {}
    }

    // ---------------------------- BACKUP ----------------------------

    private void backup(String filename) {
        File f = new File(filename);
        if (!f.exists()) return;

        try {
            Files.copy(f.toPath(), new File(filename + ".bak").toPath(),
                    StandardCopyOption.REPLACE_EXISTING);
        } catch (IOException ignored) {}
    }
}