using Microsoft.EntityFrameworkCore;
using SVSim.Database;
using SVSim.Database.Enums;
using SVSim.Database.Models;
using SVSim.EmulatedEntrypoint.Models.Dtos;

namespace SVSim.EmulatedEntrypoint.Services;

public sealed class GachaPointService : IGachaPointService
{
    private readonly SVSimDbContext _db;
    private readonly ICardPoolProvider _pools;

    public GachaPointService(SVSimDbContext db, ICardPoolProvider pools)
    {
        _db = db;
        _pools = pools;
    }

    public async Task<IReadOnlyList<GachaPointRewardDto>> GetRewardsAsync(int packId, long viewerId)
    {
        var pack = await _db.Packs.FirstOrDefaultAsync(p => p.Id == packId);
        if (pack?.GachaPointConfig is null) return Array.Empty<GachaPointRewardDto>();

        var pool = _pools.GetPool(pack);

        // EF Core 8 has no ToHashSetAsync on IQueryable — materialize via ToListAsync then hash.
        var receivedCardIds = (await _db.Viewers
            .Where(v => v.Id == viewerId)
            .SelectMany(v => v.GachaPointReceived)
            .Where(r => r.PackId == packId)
            .Select(r => r.CardId)
            .ToListAsync()).ToHashSet();

        var legendaryCardIds = pool
            .Where(c => c.Rarity == Rarity.Legendary && !c.IsFoil)
            .Select(c => c.Id)
            .ToHashSet();

        // Pull both cosmetic types in one trip. Group by card_id for O(1) lookup below.
        var cosmeticsByCard = await _db.CardCosmeticRewards
            .Where(r => legendaryCardIds.Contains(r.CardId)
                        && (r.Type == CosmeticType.Emblem || r.Type == CosmeticType.Skin))
            .ToListAsync();
        var cosmeticLookup = cosmeticsByCard
            .GroupBy(r => r.CardId)
            .ToDictionary(g => g.Key, g => g.ToList());

        var standard = new List<GachaPointRewardDto>();
        var leader = new List<GachaPointRewardDto>();

        foreach (var card in pool
            .Where(c => c.Rarity == Rarity.Legendary && !c.IsFoil)
            // Neutral cards have Class=null; client wire-encodes them as class_id="0".
            .OrderBy(c => c.Class?.Id ?? 0).ThenBy(c => c.Id))
        {
            if (!cosmeticLookup.TryGetValue(card.Id, out var cosmetics)) continue;
            var emblem = cosmetics.FirstOrDefault(c => c.Type == CosmeticType.Emblem);
            var skin = cosmetics.FirstOrDefault(c => c.Type == CosmeticType.Skin);
            if (emblem is null) continue;   // every gacha-point entry has an emblem

            var classId = (card.Class?.Id ?? 0).ToString();
            var isReceived = receivedCardIds.Contains(card.Id);

            if (IsLeaderCard(skin))
            {
                // Leader card — 3 entries in capture order: Sleeve/Card-cosmetic (type 6),
                // Skin (type 10), Emblem (type 7). The reward_type=6 entry's detail id is the
                // card_id itself, mirroring the prod capture exactly (no Sleeve cosmetic row
                // is required — synthesizing from card.Id is robust to missing rows).
                leader.Add(new GachaPointRewardDto
                {
                    ClassId = classId, CardId = card.Id, IsReceived = isReceived,
                    RewardList =
                    {
                        new GachaPointRewardDetailEntry
                        {
                            RewardType = (int)UserGoodsType.Sleeve, RewardDetailId = card.Id, RewardNumber = 1,
                        },
                        new GachaPointRewardDetailEntry
                        {
                            RewardType = (int)UserGoodsType.Skin,
                            RewardDetailId = skin!.CosmeticId, RewardNumber = 1,
                        },
                        new GachaPointRewardDetailEntry
                        {
                            RewardType = (int)UserGoodsType.Emblem,
                            RewardDetailId = emblem.CosmeticId, RewardNumber = 1,
                        },
                    },
                });
            }
            else
            {
                standard.Add(new GachaPointRewardDto
                {
                    ClassId = classId, CardId = card.Id, IsReceived = isReceived,
                    RewardList =
                    {
                        new GachaPointRewardDetailEntry
                        {
                            RewardType = (int)UserGoodsType.Emblem,
                            RewardDetailId = emblem.CosmeticId,
                            RewardNumber = 1,
                        },
                    },
                });
            }
        }

        // Standard first, then leader — matches the prod capture order for pack 10008.
        standard.AddRange(leader);
        return standard;
    }

    /// <summary>
    /// Leader cards are identified purely by the data shape: a (non-foil legendary) card with
    /// a <see cref="CosmeticType.Skin"/> cosmetic-reward row is a leader card. There is no
    /// is_leader flag, no card-id pattern, no other signal — the presence of the Skin row is
    /// the entire heuristic. Callers must have already filtered to Rarity.Legendary &amp;&amp;
    /// !IsFoil before invoking this.
    /// </summary>
    private static bool IsLeaderCard(CardCosmeticReward? skin) => skin is not null;

    public void Accrue(Viewer viewer, PackConfigEntry pack, PackChildGachaEntry child, int packNumber)
        => throw new NotImplementedException();

    public Task<ExchangeOutcome> TryExchangeAsync(Viewer viewer, int packId, long cardId)
        => throw new NotImplementedException();
}