using System;

using System.Collections.Generic;

using System.Linq;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

         var input1 = new[]

        {

            "1 book at 12.49",

            "1 music CD at 14.99",

            "1 chocolate bar at 0.85"

        };

​

        var input2 = new[]

        {

            "1 imported box of chocolates at 10.00",

            "1 imported bottle of perfume at 47.50"

        };

​

        var input3 = new[]

        {

            "1 imported bottle of perfume at 27.99",

            "1 bottle of perfume at 18.99",

            "1 packet of headache pills at 9.75",

            "1 box of imported chocolates at 11.25"

        };

​

​

        ProcessInput(input1);

        Console.WriteLine("--------------------------------------------------");

​

        ProcessInput(input2);

        Console.WriteLine("--------------------------------------------------");

​

        ProcessInput(input3);

        Console.WriteLine("--------------------------------------------------");

    }

​

    private static void ProcessInput(string[] input)

    {

        foreach (var item in input)

        {

            Console.WriteLine(item);

        }

        Console.WriteLine();

​

        var shoppringCart = ItemParser.Parse(input);

​

        var taxCalculator = new TaxCalculator();

        taxCalculator.Calculate(shoppringCart);

​

        //Discounting can be applied here!

        ShopingCartPrinter.Print(shoppringCart);

    }

}

​

enum ProductType

{

    Food,

    Medical,

    Book,

    Other

}

​

class Product

{

​

    private static readonly IDictionary<ProductType, string[]> itemType_Identifiers = new Dictionary<ProductType, string[]>

    {

        {ProductType.Food, new[]{ "chocolate", "chocolates" }},

        {ProductType.Medical, new[]{ "pills" }},

        {ProductType.Book, new[]{ "book" }}

    };

​

    public decimal ShelfPrice { get; set; }

​

    public string Name { get; set; }

​

    public bool IsImported { get { return Name.Contains("imported "); } }

​

    public bool IsTypeOf(ProductType productType)

    {

        return itemType_Identifiers.ContainsKey(productType) &&

            itemType_Identifiers[productType].Any(x => Name.Contains(x));

    }

​

    public override string ToString()

    {

        return string.Format("{0} at {1}", Name, ShelfPrice);

    }

​

}

​

#region Tax

abstract class SalesTax

{

    abstract public bool IsApplicable(Product item);

    abstract public decimal Rate { get; }

​

    public decimal Calculate(Product item)

    {

        if (IsApplicable(item))

        {

            //sales tax are that for a tax rate of n%, a shelf price of p contains (np/100)

            var tax = (item.ShelfPrice * Rate) / 100;

​

            //The rounding rules: rounded up to the nearest 0.05

            tax = Math.Ceiling(tax / 0.05m) * 0.05m;

​

            return tax;

        }

​

        return 0;

    }

}

​

class BasicSalesTax : SalesTax

{

    private ProductType[] _taxExcemptions = new[] { ProductType.Food, ProductType.Medical, ProductType.Book };

​

    public override bool IsApplicable(Product item)

    {

        return !(_taxExcemptions.Any(x => item.IsTypeOf(x)));

    }

​

    public override decimal Rate { get { return 10.00M; } }

}

​

class ImportedDutySalesTax : SalesTax

{

    public override bool IsApplicable(Product item)

    {

        return item.IsImported;

    }

​

    public override decimal Rate { get { return 5.00M; } }

}

​

class TaxCalculator

{

    private SalesTax[] _Taxes = new SalesTax[] { new BasicSalesTax(), new ImportedDutySalesTax() };

​

    public void Calculate(ShoppringCart shoppringCart)

    {

        foreach (var cartItem in shoppringCart.CartItems)

        {

            cartItem.Tax = _Taxes.Sum(x => x.Calculate(cartItem.Product));

        }

    }

}

​

#endregion Tax

​

class ShoppringCart

{

    public IList<ShoppringCartItem> CartItems { get; set; }

​

    public decimal TotalTax { get { return CartItems.Sum(x => x.Tax); } }

​

    public decimal TotalCost { get { return CartItems.Sum(x => x.Cost); } }

}

​

class ShoppringCartItem

{

    public Product Product { get; set; }

​

    public int Quantity { get; set; }

​

    public decimal Tax { get; set; }

​

    public decimal Cost { get { return Quantity * (Tax + Product.ShelfPrice); } }

​

    public override string ToString()

    {

        return string.Format("{0} {1} : {2:N2}", Quantity, Product.Name, Cost);

    }

}

​

class ItemParser

{

    private static readonly string ITEM_ENTRY_REGEX = "(\\d+) ([\\w\\s]* )at (\\d+.\\d{2})";

​

    private static readonly string[] food_identifier = { "chocolate", "chocolates" };

    private static readonly string[] medical_identifier = { "pills" };

    private static readonly string[] book_identifier = { "book" };

​

    public static ShoppringCart Parse(string[] listOfItemfullDesc)

    {

        return new ShoppringCart

        {

            CartItems = listOfItemfullDesc.Select(Parse).ToList(),

        };

    }

​

    public static ShoppringCartItem Parse(string itemfullDesc)

    {

        var regex = new Regex(ITEM_ENTRY_REGEX);

        var match = regex.Match(itemfullDesc);

        if (match.Success)

        {

            var quantity = int.Parse(match.Groups[1].Value);

            var price = decimal.Parse(match.Groups[3].Value);

​

            var itemName = match.Groups[2].Value.Trim();

​

            var shopp = new ShoppringCartItem

            {

                Quantity = quantity,

                Product = new Product { Name = itemName, ShelfPrice = price }

            };

​

            return shopp;

        }

​

        return null;

    }

}

​

class ShopingCartPrinter

{

    public static void Print(ShoppringCart shoppringCart)

    {

        //printe items => 1 chocolate bar: 0.85

        foreach (var cartItem in shoppringCart.CartItems)

        {

            Console.WriteLine(cartItem.ToString());

        }

​

        //print Sales => Taxes: 1.50

        Console.WriteLine("Taxes: {0:N2}", shoppringCart.TotalTax);

​

        //print => Total: 29.83

        Console.WriteLine("Total: {0:N2}", shoppringCart.TotalCost);

    }

}