using System;

​

using System.Linq;

using System.Collections.Generic;

using Microsoft.Extensions.DependencyInjection;

​

namespace fl.shopper.example

{

    internal class Program

    {

        private static void Main(string[] args)

        {

            var services = ConfigureServices();

            Shopper app = services.GetRequiredService<Shopper>();

            app.GoShopping();

        }

​

        private static ServiceProvider ConfigureServices()

        {

            var serviceProvider = new ServiceCollection()

                .AddSingleton<Shopper>()                

                .AddTransient<IShoppingCart, SimpleShoppingCart>()

                .BuildServiceProvider();

​

            return serviceProvider;

        }

    }

​

    public class Shopper(IShoppingCart cart)

    {                 

        public IShoppingCart Cart = cart;

​

        public void GoShopping()

        {   

            Cart.AddItem(new CartItem ("SHIRT-01", "Red Shirt", 14.99, 1));

            Cart.AddItem(new CartItem ("SHIRT-02", "Blue Shirt", 8.49,3));

            Cart.AddItem(new CartItem ("SHIRT-03", "Green Shirt", 17.99, 7));

            Cart.AddItem(new CartItem ("BELT", "Brown Belt", 22.49, 1));

            Cart.AddItem(new CartItem ("PANTS", "Pants", 14.99, 2));

            // Cart.AddCoupon(new Save15PercentOffEntirePurchase());

            // Cart.AddCoupon(new BuyOneShirtGetOneFreeCoupon());

            Cart.CheckOut();

            Cart.PrintToScreen();

        }

    }

​

    // =======================================================================================================

    // Shopping Cart Configuration

    public interface ICartConfiguration{

        double TaxRate {get;}

    }

    // =======================================================================================================

    // Shopping Cart

    public interface IShoppingCart{

        void AddItem(ICartItem item); 

        void AddCoupon(ICoupon coupon); 

        IReadOnlyList<ICartItem> Items{get;}

        ICartConfiguration Config{get;}

        double SubTotal();

        double Discounts();

        double Tax();

        double Total();

        void CheckOut();

    }

    public class SimpleShoppingCart: IShoppingCart{

        private List<ICartItem> cart_items = new();

        private List<ICoupon> coupons = new();

        public ICartConfiguration Config => default(ICartConfiguration);

        public void AddItem(ICartItem item) => cart_items.Add(item);

        public void AddCoupon(ICoupon coupon) => coupons.Add(coupon);

        public IReadOnlyList<ICartItem> Items => cart_items.AsReadOnly();

        public double SubTotal() => cart_items.Where(x => x is CartItem).Sum(item => item.Cost * item.Qty); 

        public double Tax() => 0; 

        public double Discounts() => cart_items.Where(x => x is DiscountCartItem).Sum(item => item.Cost * item.Qty);    

        public double Total() => SubTotal() + Tax() + Discounts();

        public void CheckOut(){

            recalculate_discounts();

        }

        private void recalculate_discounts(){

            //clear existing discount line items

            cart_items.RemoveAll(x => x is DiscountCartItem);

            foreach(var c in coupons.OrderBy(x => x.AppliesTo)){

                c.Apply(this);  

            }

        }

    }

    // =======================================================================================================

    // CartItems

    public interface ICartItem{

        string Sku{get;}

        string Description{get;}

        double Cost{get;}

        int Qty{get; set;}

    }

    public record class CartItem(string Sku, string Description, double Cost, int Qty) : ICartItem {

        public int Qty {get;set;} = Qty;

    }       

    public record class DiscountCartItem(string Sku, string Description, double Cost, int Qty) : ICartItem {

        public int Qty {get;set;} = Qty;

    }   

    // =======================================================================================================

    // Discount Coupons/Vouchers

    public enum CouponType{

        EachItem,

        AllItems    

    }

    public interface ICoupon{

        CouponType AppliesTo {get;}

        void Apply(IShoppingCart cart);

    }

    public class Save15PercentOffEntirePurchase : ICoupon{

        public CouponType AppliesTo => CouponType.AllItems;

        public void Apply(IShoppingCart cart){

            // calculate 15% coupon/voucher discount on the cart subtotal.

            var discountAmount = cart.SubTotal() * 0.15;

            // create a DiscountCartItem

            var discountItem = new DiscountCartItem("15%OFF", "Save 15% Off Entire Purchase!", -discountAmount, 1);

            // add item to cart

            cart.AddItem(discountItem); 

        }

    }

    public class BuyOneShirtGetOneFreeCoupon : ICoupon{

        public CouponType AppliesTo => CouponType.EachItem;

        public void Apply(IShoppingCart cart){

            // TODO: Implement buy-one-get-one-free logic by adding the appropriate DiscountCartItem (s)

            //

            // Requirements:

            //

            //   - Full Price on Higher-Priced Item: The customer pays the full price for the more expensive item.

            // 

            //   - Free Cheaper Item: The lower-priced item is free, meaning the discount is based on the cost of the less expensive product.

            //           Example:

            //            Item A costs $20.

            //            Item B costs $10.

            // 

            //           With a BOGO deal, the customer pays $20 for Item A and gets Item B free, saving $10.   

        }

    }

​

​

​

​

    public static class CartExtensions{

        public static void PrintToScreen(this IShoppingCart cart){

            const int width = 90;   

            var __ = new string ('-',width);

            Console.WriteLine($"\n🛒 [{cart.GetType().Name}]\n");

            Console.WriteLine(__);

            Console.WriteLine($"{"#",2}    {"SKU",-16} {"Description",-48} {"Qty",-6}  {"Cost",8}");

            Console.WriteLine(__);

            var index = 1;

            foreach(var item in cart.Items.Where(x => x is CartItem))

                Console.WriteLine($"{index++,2}.   {item.Sku,-16} {item.Description,-48}  {item.Qty,-5}  {item.Cost,8:$0.00}");

            var st = $"{"Sub-Total",35}:{cart.SubTotal(),12:$0.00}";

            Console.WriteLine(__);

            Console.WriteLine($"{st,width-2}");

            var discounts = cart.Items.Where(x => x is DiscountCartItem);

            if(discounts.Any())

            {

                Console.WriteLine($"\n{"",2}    {"Discounts:",-16}");

                Console.WriteLine(__);

                foreach(var item in discounts)

                   Console.WriteLine($"{"$",2}    {item.Sku,-16} {item.Description,-48}  {item.Qty,-5}  {item.Cost,8:$0.00}");

            }

            Console.WriteLine(__);

            string[] summary = [//$"{"Sub-Total",35}:{cart.SubTotal(),12:$0.00}",

                                $"{"Discounts",35}:{cart.Discounts(),12:$0.00}",

                                $"{"Tax " + $"({cart.Config?.TaxRate ?? 0:0.00%})",35}:{cart.Tax(),12:$0.00}",

                                $"{"Total",35}:{cart.Total(),12:$0.00}"];

            foreach(var line in summary)

                Console.WriteLine($"{line,width-2}");

        }       

    }

}