using OECS;

namespace Game.CardWars;

/// <summary>
/// Shared utility methods for querying and manipulating the game world.
/// </summary>
public static class GameUtil
{
    public static Entity FindEntity<T>(World world) where T : struct
    {
        using var iter = world.Select<T>();
        while (iter.MoveNext())
        {
            if (iter.CurrentEntity != World.SingletonEntity)
                return iter.CurrentEntity;
        }
        return Entity.Null;
    }

    public static List<Entity> FindAllEntities<T>(World world) where T : struct
    {
        var list = new List<Entity>();
        using var iter = world.Select<T>();
        while (iter.MoveNext())
        {
            if (iter.CurrentEntity != World.SingletonEntity)
                list.Add(iter.CurrentEntity);
        }
        return list;
    }

    /// <summary>Draw the top card from a deck and add it to the player's hand.</summary>
    public static bool DrawCard(World world, Entity deck, Entity player)
    {
        var cards = world.GetSources<InDeck>(deck);
        if (cards.Count == 0) return false;

        var cardEntity = cards.First();
        world.RemoveComponent<InDeck>(cardEntity);
        world.AddComponent(cardEntity, new HeldBy { Source = cardEntity, Target = player });
        return true;
    }

    /// <summary>Shuffle cards in a deck using Fisher-Yates with the given seed.</summary>
    public static void ShuffleDeck(World world, Entity deck, ref uint seed)
    {
        var cards = world.GetSources<InDeck>(deck).ToArray();
        for (int i = cards.Length - 1; i > 0; i--)
        {
            int j = Mulberry32.NextInt(ref seed, 0, i);
            (cards[i], cards[j]) = (cards[j], cards[i]);
        }
        for (int i = cards.Length - 1; i >= 0; i--)
            world.RemoveComponent<InDeck>(cards[i]);
        for (int i = 0; i < cards.Length; i++)
            world.AddComponent(cards[i], new InDeck { Source = cards[i], Target = deck });
    }

    /// <summary>Get all field cards for a player.</summary>
    public static List<Entity> GetFieldCards(World world, Entity player)
    {
        return world.GetSources<OnField>(player).ToList();
    }

    /// <summary>Get all cards in a player's hand.</summary>
    public static List<Entity> GetHandCards(World world, Entity player)
    {
        return world.GetSources<HeldBy>(player).ToList();
    }

    /// <summary>Calculate a player's total battle power.</summary>
    public static int CalculatePower(World world, Entity player)
    {
        int total = 0;

        // Leader power.
        using var leaderIter = world.Select<Leader>();
        while (leaderIter.MoveNext())
        {
            if (leaderIter.CurrentEntity == World.SingletonEntity) continue;
            var onFieldSources = world.GetSources<OnField>(player);
            if (onFieldSources.Contains(leaderIter.CurrentEntity))
            {
                if (world.TryGetComponent<Card>(leaderIter.CurrentEntity, out var leaderCard))
                    total += leaderCard.Rank;
            }
        }

        // Find the player's banner.
        var banner = CardEffectHelpers.GetBanner(world, player);
        bool bannerHasHorn = banner != Entity.Null && world.HasComponent<Horn>(banner);
        bool bannerHasSkull = banner != Entity.Null && world.HasComponent<Skull>(banner);

        // Field cards.
        var fieldCards = GetFieldCards(world, player);
        int poweredCount = 0;
        foreach (var card in fieldCards)
        {
            if (!world.TryGetComponent<Card>(card, out var cardData)) continue;
            if (cardData.FaceDown) continue;
            if (cardData.Rank <= 0) continue;

            poweredCount++;
            int rank = cardData.Rank;
            if (world.HasComponent<Horn>(card))
                rank *= 2;
            if (world.HasComponent<Skull>(card))
                rank = 0;

            total += rank;
        }

        if (bannerHasHorn) total += poweredCount;
        if (bannerHasSkull) total -= poweredCount;

        return total;
    }

    /// <summary>Move all field cards (except leaders and banners) to the discard pile.</summary>
    public static void DiscardField(World world, Entity player, Entity discardDeck)
    {
        var fieldCards = GetFieldCards(world, player);

        var toDiscard = new List<Entity>();
        foreach (var card in fieldCards)
        {
            // Keep leaders and banners on the field.
            if (world.HasComponent<Leader>(card)) continue;
            if (world.HasComponent<Banner>(card)) continue;
            toDiscard.Add(card);
        }

        foreach (var card in toDiscard)
        {
            world.RemoveComponent<OnField>(card);
            world.RemoveComponent<Card>(card);
            world.AddComponent(card, new InDeck { Source = card, Target = discardDeck });
        }

        // Destroy horns and skulls placed on discarded cards.
        var tokenTargets = new HashSet<Entity>();
        foreach (var card in toDiscard)
        {
            foreach (var token in world.GetSources<PlacedOn>(card))
                tokenTargets.Add(token);
        }
        foreach (var token in tokenTargets)
            world.DestroyEntity(token);
    }

    /// <summary>Recycle discard pile into draw pile.</summary>
    public static void RecycleDiscard(World world, Entity drawDeck, Entity discardDeck)
    {
        var cards = world.GetSources<InDeck>(discardDeck).ToList();
        foreach (var card in cards)
        {
            world.RemoveComponent<InDeck>(card);
            world.AddComponent(card, new InDeck { Source = card, Target = drawDeck });
        }
    }
}