Магазин

using System;
using System.Numerics;

namespace Shop
{
    class Program
    {
        static void Main(string[] args)
        {
            const string CommandShowSellerGoods = "1";
            const string CommandSellGoods = "2";
            const string CommandShowPlayerInventory = "3";
            const string CommandExit = "4";

            bool isWork = true;
            Seller seller = new Seller();
            Player player = new Player();
            Menu menu = new Menu(seller.GetProducts());

            while (isWork)
            {
                Console.Clear();
                Console.WriteLine($"{CommandShowSellerGoods}. Показать список товаров." +
                    $"\n{CommandSellGoods}. Продать товар." +
                    $"\n{CommandShowPlayerInventory}. Показать сумку покупателя." +
                    $"\n{CommandExit}. Выйти");

                switch (Console.ReadLine())
                {
                    case CommandShowSellerGoods:
                        seller.ShowAllItems();
                        break;

                    case CommandSellGoods:
                        menu.TryRun(seller, player);
                        break;

                    case CommandShowPlayerInventory:
                        player.ShowAllItems();
                        break;

                    case CommandExit:
                        isWork = false;
                        break;

                    default:
                        Console.WriteLine("Ошибка, такого пункта меню нет");
                        break;
                }

                Console.ReadKey();
                Console.Clear();
            }
        }
    }

    class Trader
    {
        protected List<Product> Products = new List<Product>();
        protected int Money = 0;

        virtual public void ShowAllItems()
        {
            if (Products.Count > 0)
            {
                foreach (Product item in Products)
                {
                    item.ShowInfo();
                }
            }
            else
            {
                Console.WriteLine($"Инвентарь пуст.");
            }
        }
    }

    class Seller : Trader
    {
        public Seller()
        {
            Products.Add(new Product("Выход", 0));
            Products.Add(new Product("Хлеб", 12));
            Products.Add(new Product("Овес", 4));
            Products.Add(new Product("Сыр", 118));
            Products.Add(new Product("Яйца", 32));
            Products.Add(new Product("Чай", 23));
        }

        public List<Product> GetProducts()
        {
            return Products;
        }

        public void TakeMoney(int payment)
        {
            Money += payment;
        }

        public void Sell(int index)
        {
            Product product = Products[index];
            Products.Remove(product);
            Money += product.Price;
        }

        public override void ShowAllItems()
        {
            if (Products.Count > 1)
            {
                foreach (Product item in Products)
                {
                    if(item.Name == "Выход")
                    {
                        continue;
                    }
                    else
                    {
                        item.ShowInfo();
                    }
                }
            }
            else
            {
                Console.WriteLine($"Инвентарь пуст.");
            }
        }
    }

    class Player : Trader
    {
        private int _moneyToPay;

        public int Money { get; private set; } = 5000;

        public void AddGoods(Product product)
        {
            Products.Add(product);
        }

        public bool CheckSolvency(Product product)
        {
            _moneyToPay = product.Price;

            if (Money >= _moneyToPay)
            {
                return true;
            }
            else
            {
                _moneyToPay = 0;
                return false;
            }
        }

        public int Pay()
        {
            Money -= _moneyToPay;
            return _moneyToPay;
        }
    }

    class Product
    {
        public Product(string name, int price)
        {
            Name = name;
            Price = price;
        }

        public string Name { get; private set; }
        public int Price { get; private set; }

        public void ShowInfo()
        {
            Console.WriteLine($"Название товара: {Name}, цена: {Price}.");
        }
    }

    class Menu
    {
        private List<Product> _items;
        private int _selectedItemIndex;

        public Menu(List<Product> items)
        {
            _items = items;
            _selectedItemIndex = 0;
        }

        private void Display()
        {
            Console.Clear();
            Console.WriteLine("Управление ▲, ▼, Enter, Esc.");

            for (int i = 0; i < _items.Count; i++)
            {
                int isequenceNumber = i;
                var currentItem = _items[i];
                if (i == _selectedItemIndex)
                {
                    Console.ForegroundColor = ConsoleColor.Black;
                    Console.BackgroundColor = ConsoleColor.Gray;

                    if(i == 0)
                    {
                        Console.WriteLine($"{isequenceNumber}. {currentItem.Name}.");
                    }
                    else
                    {
                        Console.WriteLine($"{isequenceNumber}. {currentItem.Name}, Цена: {currentItem.Price}");
                    }
                }
                else
                {
                    if (i == 0)
                    {
                        Console.WriteLine($"{isequenceNumber}. {currentItem.Name}.");
                    }
                    else
                    {
                        Console.WriteLine($"{isequenceNumber}. {currentItem.Name}, Цена: {currentItem.Price}");
                    }
                }

                Console.ResetColor();
            }
        }

        public void MoveUp()
        {
            _selectedItemIndex--;

            if (_selectedItemIndex < 0)
            {
                _selectedItemIndex = _items.Count - 1;
            }
        }

        public void MoveDown()
        {
            _selectedItemIndex++;

            if (_selectedItemIndex >= _items.Count)
            {
                _selectedItemIndex = 0;
            }
        }

        public void СhooseGoods(Seller seller, Player player, ref bool isExit)
        {
            Product product = _items[_selectedItemIndex];

            if(_selectedItemIndex == 0)
            {
                isExit = false;
            }
            else
            {
                if (player.CheckSolvency(product))
                {
                    seller.Sell(_selectedItemIndex);
                    player.AddGoods(product);
                    seller.TakeMoney(player.Pay());
                    MoveUp();

                    Console.WriteLine($"Осталось денег: {player.Money}.");
                    Console.ReadKey();
                }
                else
                {
                    Console.WriteLine("Не хватает денег.");
                    Console.ReadKey();
                }
            }
        }

        public void TryRun(Seller seller, Player player)
        {
            if(_items.Count> 1)
            {
                Run(seller, player);
            }
            else
            {
                Console.WriteLine("В магазине нет товаров.");
            }
        }

        public void Run(Seller seller, Player player)
        {
            const ConsoleKey KeyMoveUp = ConsoleKey.UpArrow;
            const ConsoleKey KeyMoveDown = ConsoleKey.DownArrow;
            const ConsoleKey KeyPressingEnter = ConsoleKey.Enter;
            const ConsoleKey KeyPressingEscape = ConsoleKey.Escape;

            bool isWork = true;

            while (isWork)
            {
                Display();
                ConsoleKeyInfo keyInfo;
                keyInfo = Console.ReadKey(true);

                switch (keyInfo.Key)
                {
                    case KeyMoveUp:
                        MoveUp();
                        break;

                    case KeyMoveDown:
                        MoveDown();
                        break;

                    case KeyPressingEnter:
                        СhooseGoods(seller, player, ref isWork);
                        break;

                    case KeyPressingEscape:
                        isWork = false;
                        break;
                }
            }
        }
    }
}