---

using System;
using System.Collections.Generic;
using System.Linq;

namespace ExpiryTracker
{
    public class ProductRepository
    {
        private static List<Product> products = new List<Product>();
        private static int nextId = 1;

        public void Add(Product product)
        {
            product.Id = nextId;
            nextId++;

            products.Add(product);
        }

        public void Update(Product product)
        {
            Product existingProduct = products.FirstOrDefault(p => p.Id == product.Id);

            if (existingProduct != null)
            {
                existingProduct.ProductName = product.ProductName;
                existingProduct.ProductionDate = product.ProductionDate;
                existingProduct.ExpiryDate = product.ExpiryDate;
                existingProduct.Quantity = product.Quantity;
            }
        }

        public void Delete(int id)
        {
            Product product = products.FirstOrDefault(p => p.Id == id);

            if (product != null)
            {
                products.Remove(product);
            }
        }

        public List<Product> GetAll()
        {
            return products
                .OrderBy(p => p.ExpiryDate)
                .ToList();
        }

        public List<Product> GetExpired()
        {
            return products
                .Where(p => p.ExpiryDate.Date < DateTime.Today)
                .OrderBy(p => p.ExpiryDate)
                .ToList();
        }

        public List<Product> GetFiltered(string name, DateTime? dateFrom, DateTime? dateTo, bool onlyExpired)
        {
            IEnumerable<Product> result = products;

            if (!string.IsNullOrWhiteSpace(name))
            {
                result = result.Where(p =>
                    p.ProductName != null &&
                    p.ProductName.ToLower().Contains(name.Trim().ToLower())
                );
            }

            if (dateFrom.HasValue)
            {
                result = result.Where(p => p.ExpiryDate.Date >= dateFrom.Value.Date);
            }

            if (dateTo.HasValue)
            {
                result = result.Where(p => p.ExpiryDate.Date <= dateTo.Value.Date);
            }

            if (onlyExpired)
            {
                result = result.Where(p => p.ExpiryDate.Date < DateTime.Today);
            }

            return result
                .OrderBy(p => p.ExpiryDate)
                .ToList();
        }
    }
}