using System;

using System.Collections.Generic;

using System.Linq;

​

var game = new Game();

game.Run();

​

sealed class Game

{

    public void Run()

    {

        Console.WriteLine("Welcome to Blackjack!");

        var cardDeck = new CardDeck();

        var player = new Player(cardDeck);

        var dealer = new Dealer(cardDeck);

        player.Play();

        dealer.Play();

        CheckWinCondition(player, dealer);

    }

    private static void CheckWinCondition(Player player, Dealer dealer)

    {

        if (player.IsBusted && dealer.IsBusted)

        {

            Console.WriteLine("Draw! Both the player and the dealer busted.");

        }

        else if (dealer.IsBusted)

        {

            Console.WriteLine("Win! The dealer bust.");

        }

        else if (player.IsBusted)

        {

            Console.WriteLine("Lose! You bust.");

        }

        else if (player.HandTotal == dealer.HandTotal)

        {

            Console.WriteLine("Draw! You have the same score.");    

        }

        else if (player.HandTotal > dealer.HandTotal)

        {

            Console.WriteLine("Win! You beat the dealer."); 

        }

        else

        {

            Console.WriteLine("Lose! The dealer beat you.");    

        }

    }

}

​

sealed class Player

{

    private readonly Hand _hand;

    public Player(CardDeck cardDeck)

    {

        _hand = new Hand(cardDeck);

    }

    public int HandTotal => _hand.HandTotal;

    public bool IsBusted => _hand.IsBusted;

    public void Play()

    {

        Console.WriteLine($"Your hand: {string.Join(", ", _hand.Cards.Select(card => card.Type))} ({_hand.HandTotal})");

        while (!IsBusted)

        {

            Console.WriteLine("Please enter your choice (hit or call)");

            var input = Console.ReadLine().ToLowerInvariant();

            if (input is "h" or "hit")

            {

                var drawnCard = _hand.DrawCard();

                Console.WriteLine($"You drew a {drawnCard.Type}, your new hand total is {_hand.HandTotal}");

            }

            else if (input is "c" or "call")

            {

                break;

            }

        }

    }

}

​

sealed class Dealer

{

    private readonly Hand _hand;

    public Dealer(CardDeck cardDeck)

    {

        _hand = new Hand(cardDeck);

    }

    public int HandTotal => _hand.HandTotal;

    public bool IsBusted => _hand.IsBusted;

    public void Play()

    {

        Console.WriteLine($"Dealer's hand: {string.Join(", ", _hand.Cards.Select(card => card.Type))} ({_hand.HandTotal})");

        while (!IsBusted && _hand.HandTotal <= 16)

        {

            var drawnCard = _hand.DrawCard();

            Console.WriteLine($"Dealer drew a {drawnCard.Type}, their new hand total is {_hand.HandTotal}");

        }

    }

}

​

sealed class Hand

{

    private readonly CardDeck _cardDeck;

    private readonly List<Card> _hand;

    public Hand(CardDeck cardDeck)

    {

        _cardDeck = cardDeck;

        _hand = [ cardDeck.DrawCard(), cardDeck.DrawCard() ];

        HandTotal = GetHandTotal();

    }

​

    public int HandTotal { get; private set; }

    public IReadOnlyList<Card> Cards => _hand.AsReadOnly();

    public bool IsBusted => IsHandBusted(HandTotal);

    public Card DrawCard()

    {

        var card = _cardDeck.DrawCard();

        _hand.Add(card);

        HandTotal = GetHandTotal();

        return card;

    }

    private int GetHandTotal()

    {

        var handTotal = _hand.Sum(card => card.Value);

        if (IsHandBusted(handTotal))

        {

            var numberOfAces = _hand.Count(card => card.Type == CardType.Ace);

            for (int i = 0; i < numberOfAces && IsHandBusted(handTotal); i++) // decrease value of aces from 11 to 1

            {

                handTotal -= 10;    

            }

        }

        return handTotal;

    }

    private static bool IsHandBusted(int handTotal)

    {

        return handTotal > 21;

    }

}

​

sealed class CardDeck

{

    private readonly Random _random;

    private readonly Stack<Card> _cards;

    public CardDeck()

    {

        _random = new Random();

        _cards = InitializeDeck();

    }

    public Card DrawCard()

    {

        return _cards.Pop();

    }

    private Stack<Card> InitializeDeck()

    {

        var allCards = new List<Card>();

        foreach (var cardType in Enum.GetValues<CardType>())

        {

            var card = new Card

            {

                Type = cardType,

                Value = GetCardValue(cardType),

            };

            for (int i = 0; i < 4; i++)

            {

                allCards.Add(card);

            }

        }

        Shuffle(allCards);

        return new Stack<Card>(allCards);

    }

    private void Shuffle(List<Card> cards)

    {

        for (var i = 0; i < 100; i++)

        {

            var oldCardIndex = _random.Next(0, cards.Count);

            var newCardIndex = _random.Next(0, cards.Count);

            var oldCard = cards[oldCardIndex];

            var newCard = cards[newCardIndex];

            cards[oldCardIndex] = newCard;

            cards[newCardIndex] = oldCard;

        }

    }

    private static int GetCardValue(CardType cardType)

    {

        return cardType switch

        {

            CardType.Ace => 11,

            CardType.Jack or CardType.Queen or CardType.King => 10,

            _ => (int)cardType

        };

    }

}

​

sealed class Card

{

    public CardType Type { get; init; }

    public int Value { get; init; }

}

​

enum CardType

{

    N2 = 2,

    N3,

    N4,

    N5,

    N6,

    N7,

    N8,

    N9,

    N10,

    Jack,

    Queen,

    King,

    Ace,

}

​