using OECS;

namespace Blackjack;

/// <summary>
/// Renders the current game state to the console.
/// </summary>
public class RenderSystem : ISystem
{
    public void Run(World world)
    {
        var state = world.ReadSingleton<GameState>();

        Console.WriteLine();
        Console.WriteLine("  Blackjack");
        Console.WriteLine("  ═════════");
        Console.WriteLine();
        Console.WriteLine($"  Chips: {state.Chips}  |  Round: {state.RoundNumber}");
        Console.WriteLine();

        // Show dealer's hand.
        var dealerTotal = HandUtil.CalculateHand(world, DealerHandTag.Instance);
        Console.Write("  Dealer: ");
        if (state.Phase == GamePhase.PlayerTurn)
        {
            // Hide first card (hole card) during player's turn.
            Console.Write("?? ");
            PrintHand(world, DealerHandTag.Instance, skipFirst: true);
        }
        else
        {
            PrintHand(world, DealerHandTag.Instance);
            Console.Write($"  ({dealerTotal})");
        }
        Console.WriteLine();

        // Show player's hand.
        var playerTotal = HandUtil.CalculateHand(world, PlayerHandTag.Instance);
        Console.Write("  Player: ");
        PrintHand(world, PlayerHandTag.Instance);
        Console.Write($"  ({playerTotal})");
        Console.WriteLine();
        Console.WriteLine();

        // Status line.
        switch (state.Phase)
        {
            case GamePhase.Betting:
                Console.Write($"  Enter bet (1–{state.Chips}): ");
                break;
            case GamePhase.PlayerTurn:
                Console.Write("  [H]it or [S]tand: ");
                break;
            case GamePhase.RoundOver:
                Console.WriteLine($"  {ResultText(state.Result)}");
                Console.WriteLine();
                Console.Write("  Press Enter for next round...");
                break;
            default:
                break;
        }
    }

    private static void PrintHand(World world, DealerHand hand, bool skipFirst = false)
    {
        PrintHandImpl(world, hand, skipFirst);
    }

    private static void PrintHand(World world, PlayerHand hand)
    {
        PrintHandImpl(world, hand, skipFirst: false);
    }

    private static void PrintHandImpl<T>(World world, T handTag, bool skipFirst)
        where T : struct
    {
        Entity handEntity = Entity.Null;
        using (var iter = world.Select<T>())
        {
            while (iter.MoveNext())
            {
                if (iter.CurrentEntity != World.SingletonEntity)
                {
                    handEntity = iter.CurrentEntity;
                    break;
                }
            }
        }

        if (handEntity == Entity.Null)
            return;

        var cards = world.GetSources<Holds>(handEntity);
        var ordered = cards.OrderByDescending(c =>
        {
            var card = world.ReadComponent<Card>(c);
            return (int)card.Rank;
        }).ToList();

        bool first = true;
        foreach (var cardEntity in ordered)
        {
            if (skipFirst && first)
            {
                first = false;
                continue;
            }
            first = false;
            var card = world.ReadComponent<Card>(cardEntity);
            Console.Write(CardToString(card));
            Console.Write(" ");
        }
    }

    private static string CardToString(Card card)
    {
        var suit = card.Suit switch
        {
            Suit.Hearts => "♥",
            Suit.Diamonds => "♦",
            Suit.Clubs => "♣",
            Suit.Spades => "♠",
            _ => "?"
        };

        var rank = card.Rank switch
        {
            Rank.Ace => "A",
            Rank.Jack => "J",
            Rank.Queen => "Q",
            Rank.King => "K",
            _ => ((int)card.Rank).ToString()
        };

        return $"{rank}{suit}";
    }

    private static string ResultText(RoundResult result) => result switch
    {
        RoundResult.PlayerBust => "You bust! Dealer wins.",
        RoundResult.DealerBust => "Dealer busts! You win!",
        RoundResult.PlayerWin => "You win!",
        RoundResult.DealerWin => "Dealer wins.",
        RoundResult.Push => "Push — it's a tie!",
        RoundResult.Blackjack => "Blackjack!",
        _ => ""
    };
}