using ComputersShopFileImplement.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Xml.Linq;

namespace ComputersShopFileImplement
{
	public class DataFileSingleton
	{
		private static DataFileSingleton? instance;
		private readonly string ComponentFileName = "Component.xml";
		private readonly string OrderFileName = "Order.xml";
		private readonly string ComputerFileName = "Computer.xml";
		private readonly string ClientFileName = "Client.xml";
        private readonly string ImplementerFileName = "Implementer.xml";

        public List<Component> Components { get; private set; }
		public List<Order> Orders { get; private set; }
		public List<Computer> Computers { get; private set; }
		public List<Client> Clients { get; private set; }
        public List<Implementer> Implementers { get; private set; }

        public static DataFileSingleton GetInstance()
		{
			if (instance == null)
			{
				instance = new DataFileSingleton();
			}
			return instance;
		}
		public void SaveComponents() => SaveData(Components, ComponentFileName, "Components", x => x.GetXElement);
		public void SaveComputers() => SaveData(Computers, ComputerFileName, "Computers", x => x.GetXElement);
		public void SaveOrders() => SaveData(Orders, OrderFileName, "Orders", x => x.GetXElement);
		public void SaveClients() => SaveData(Clients, OrderFileName, "Clients", x => x.GetXElement);
        public void SaveImplementers() => SaveData(Implementers, ImplementerFileName, "Implementers", x => x.GetXElement);

        private DataFileSingleton()
		{
			Components = LoadData(ComponentFileName, "Component", x => Component.Create(x)!)!;
			Computers = LoadData(ComputerFileName, "Computer", x => Computer.Create(x)!)!;
			Orders = LoadData(OrderFileName, "Order", x => Order.Create(x)!)!;
			Clients = LoadData(ClientFileName, "Client", x => Client.Create(x)!)!;
            Implementers = LoadData(ImplementerFileName, "Implementer", x => Implementer.Create(x)!)!;
        }
        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);
			}
		}
	}
}