PIbd-22_Shabunov_O.A._AutoWorkshop/AutoWorkshopFileImplement/DataFileSingleton.cs

using AutoWorkshopFileImplement.Models;
using System.Xml.Linq;

namespace AutoWorkshopFileImplement
{
    public class DataFileSingleton
    {
        private static DataFileSingleton? _instance;
        
        private readonly string ComponentFileName = "Component.xml";
        private readonly string OrderFileName = "Order.xml";
        private readonly string RepairFileName = "Repair.xml";
        private readonly string ShopFileName = "Shop.xml";

        public List<Component> Components { get; private set; }        
        public List<Order> Orders { get; private set; }        
        public List<Repair> Repairs { get; private set; }
        public List<Shop> Shops { get; private set; }

        private DataFileSingleton()
        {
            Components  = LoadData(ComponentFileName, "Component", x => Component.Create(x)!)!;
            Repairs     = LoadData(RepairFileName, "Repair", x => Repair.Create(x)!)!;
            Orders      = LoadData(OrderFileName, "Order", x => Order.Create(x)!)!;
            Shops       = LoadData(ShopFileName, "Shop", x => Shop.Create(x)!)!;
        }
        
        public static DataFileSingleton GetInstance()
        {
            if (_instance == null)
            {
                _instance = new DataFileSingleton();
            }
            
            return _instance;
        }

        public void SaveComponents() => SaveData(Components, ComponentFileName, "Components", x => x.GetXElement);
        public void SaveRepairs() => SaveData(Repairs, RepairFileName, "Repairs", x => x.GetXElement);
        public void SaveOrders() => SaveData(Orders, OrderFileName, "Orders", x => x.GetXElement);
        public void SaveShops() => SaveData(Shops, ShopFileName, "Shops", x => x.GetXElement);

        private static List<T>? LoadData<T>(string FileName, string XmlNodeName, Func<XElement, T> SelectFunction)
        {
            if (File.Exists(FileName))
            {
                return XDocument.Load(FileName)?.Root?.Elements(XmlNodeName)?.Select(SelectFunction)?.ToList();
            }
            
            return new List<T>();
        }
        
        private static void SaveData<T>(List<T> Data, string FileName, string XmlNodeName, Func<T, XElement> SelectFunction)
        {
            if (Data != null)
            {
                new XDocument(new XElement(XmlNodeName, Data.Select(SelectFunction).ToArray())).Save(FileName);
            }
        }
    }
}