Ncontracts - Code Challenge

Ncontracts Code Challenge.cs

// Ncontracts Code Challenge
// Please take a look at the code below and refactor it to your liking.
// Please spend no more than 40 minutes on this exercise.
// If you finish early, try adding another calculation for "Office Supply" category.
// Once done, please send me a link to your gists. 

using System;
using System.Collections.Generic;

namespace CodingChallenge.Shopping
{
    public enum ItemCategory
    {
        Unspecified,
        Christmas,
        Food,
        OfficeSupplies
    }

    class Program
    {
        static void Main(string[] args)
        {
            var program = new Program();

            program.ChristmasShoppingAtTheGroceryStore();
            program.BuyingFood();
            program.BuyingOfficeSupplies();
        }

        void BuyingOfficeSupplies()
        {
            var carts = new List<CartItem>
            {
                new OfficeItem("Pens (3-pack)", 4.99m, 10),
                new OfficeItem("Desk", 189m, 1),
                new OfficeItem("Stapler", 7m, 3),
            };

            var calculator = new GroceryStoreCheckoutCalculator();
            var total = calculator.Calculate(carts, new DateTime(2020, 7, 30));
            Console.WriteLine(total);

            var totalInAugust = calculator.Calculate(carts, new DateTime(2020, 8, 30));
            Console.WriteLine(totalInAugust);
        }

        void ChristmasShoppingAtTheGroceryStore()
        {
            var carts = new List<CartItem>
            {
                new ChristmasItem("Lights", 5.99m, 10),
                new ChristmasItem("Tree", 169m, 1),
                new ChristmasItem("Ornaments", 8m, 15),
            };

            var calculator = new GroceryStoreCheckoutCalculator();
            var total = calculator.Calculate(carts, new DateTime(2020, 11, 30));
            Console.WriteLine(total);

            var totalAfterChristmas = calculator.Calculate(carts, new DateTime(2020, 12, 30));
            Console.WriteLine(totalAfterChristmas);
        }

        void BuyingFood()
        {
            var carts = new List<CartItem>
            {
                new FoodItem("Apple", 3.27m, 0.79m),
                new FoodItem("Scallop", 18m, 1.5m),
                new FoodItem("Salad", 6.99m, 1),
                new FoodItem("Ground Beef", 7.99m, 1.5m),
                new FoodItem("Red Wine", 25.99m, 1)
            };

            var calculator = new GroceryStoreCheckoutCalculator();
            var total = calculator.Calculate(carts, new DateTime(2020, 11, 30));
            Console.WriteLine(total);

            var seniorHourTotal = calculator.Calculate(carts, new DateTime(2020, 11, 30, 7, 11, 0));
            Console.WriteLine(seniorHourTotal);
        }
    }

    public class GroceryStoreCheckoutCalculator
    {
        private decimal ChristmasDiscount(int day)
        {
            if (day < 15)
            {
                return 20m;
            }

            if (day <= 25)
            {
                return 60m;
            }

            return 90m;
        }
        
        private decimal DiscountFor(ItemCategory category, DateTime checkOutDate)
        {
            switch (category)
            {
                case ItemCategory.Christmas when checkOutDate.Month == 12:
                    return 1m - ChristmasDiscount(checkOutDate.Day) / 100m;
                case ItemCategory.Food when checkOutDate.TimeOfDay.Hours > 6 && checkOutDate.TimeOfDay.Hours <= 8:
                    // senior discount
                    return 0.9m;
                case ItemCategory.OfficeSupplies when checkOutDate.Month == 8:
                    // back-to-school discount:
                    return 0.85m;
                default:
                    return 1m;
            }
        }

        public decimal Calculate(List<CartItem> carts, DateTime checkOutDate)
        {
            decimal itemTotal = 0m;

            foreach (var item in carts)
            {
                var discount = DiscountFor(item.Category, checkOutDate);
                switch (item.Category)
                {
                    case ItemCategory.Food when item.Weight != 0:
                        itemTotal += item.Weight * item.Price * discount;
                        break;
                    case ItemCategory.Unspecified:
                        // oh no! this should not happen!
                        break;
                    default:
                        itemTotal += item.Quantity * item.Price * discount;
                        break;
                }
            }

            return itemTotal;
        }
    }

    public class OfficeItem : CartItem
    {
        public OfficeItem(string productName, decimal price, int quantity)
        {
            Category = ItemCategory.OfficeSupplies;
            ProductName = productName;
            Price = price;
            Quantity = quantity;
        }
    }

    public class FoodItem : CartItem
    {
        public FoodItem(string productName, decimal price, int quantity)
        {
            Category = ItemCategory.Food;
            ProductName = productName;
            Price = price;
            Quantity = quantity;
        }

        public FoodItem(string productName, decimal price, decimal weight)
        {
            Category = ItemCategory.Food;
            ProductName = productName;
            Price = price;
            Weight = weight;
        }
    }

    public class ChristmasItem : CartItem
    {
        public ChristmasItem(string productName, decimal price, int quantity)
        {
            Category = ItemCategory.Christmas;
            ProductName = productName;
            Price = price;
            Quantity = quantity;
        }
    }

    public class CartItem
    {
        public string ProductName { get; set; }
        public decimal Price { get; set; }
        public int Quantity { get; set; }
        public ItemCategory Category { get; set; }
        public decimal Weight { get; set; }
    }
}