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

namespace SVSim.EmulatedEntrypoint.Services;

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

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

    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)
    {
        if (pack.GachaPointConfig is null) return;
        if (packNumber <= 0) return;

        // Per-child override wins when set (>0); fall back to the pack's default.
        int perPack = child.OverrideIncreaseGachaPoint > 0
            ? child.OverrideIncreaseGachaPoint
            : pack.GachaPointConfig.IncreaseGachaPoint;
        if (perPack <= 0) return;

        int delta = perPack * packNumber;

        var existing = viewer.GachaPointBalances.FirstOrDefault(b => b.PackId == pack.Id);
        if (existing is null)
        {
            viewer.GachaPointBalances.Add(new ViewerGachaPointBalance
            {
                PackId = pack.Id, Points = delta,
            });
        }
        else
        {
            existing.Points += delta;
        }
    }

    public async Task<ExchangeOutcome> TryExchangeAsync(Viewer viewer, int packId, long cardId)
    {
        var pack = await _db.Packs.FirstOrDefaultAsync(p => p.Id == packId);
        if (pack?.GachaPointConfig is null)
            return ExchangeOutcome.Fail("pack_not_exchangeable");

        int threshold = pack.GachaPointConfig.ExchangeablePoint;
        var balance = viewer.GachaPointBalances.FirstOrDefault(b => b.PackId == packId);
        if (balance is null || balance.Points < threshold)
            return ExchangeOutcome.Fail("insufficient_gacha_points");

        // Validate the card is in the catalog by re-running GetRewardsAsync. This re-uses the
        // same eligibility rules (in-pool + Legendary + has Emblem cosmetic) without
        // duplicating them — and naturally excludes ticket-only packs whose pool we already
        // hide from /pack/info.
        var catalog = await GetRewardsAsync(packId, viewer.Id);
        var entry = catalog.FirstOrDefault(e => e.CardId == cardId);
        if (entry is null)
            return ExchangeOutcome.Fail("card_not_exchangeable");

        if (viewer.GachaPointReceived.Any(r => r.PackId == packId && r.CardId == cardId))
            return ExchangeOutcome.Fail("already_received");

        // Debit balance + mark received. (`balance` is non-null past the earlier guard.)
        balance.Points -= threshold;
        viewer.GachaPointReceived.Add(new ViewerGachaPointReceived
        {
            PackId = packId, CardId = cardId, ReceivedAt = DateTime.UtcNow,
        });

        // Grant the card itself through RewardGrantService — its CardCosmeticReward cascade
        // covers the Emblem (standard legendary) or Skin+Emblem (leader) the catalog
        // advertised. The catalog's reward_list is a wire-shape *display* (what the player
        // sees on /pack/get_gacha_point_rewards) — the actual grant uses the canonical
        // primitive per feedback_reward_grant_service. For leader-card exchanges the catalog
        // also advertises a synthetic Sleeve(=card_id) entry, but that's not in
        // CardCosmeticRewards; if a capture ever shows leader exchanges granting a sleeve
        // row, add that here. Today no leader exchange has been captured.
        var granted = await _grants.ApplyAsync(viewer, UserGoodsType.Card, cardId, 1);
        var rewardList = new List<RewardListEntry>();
        foreach (var g in granted)
        {
            rewardList.Add(new RewardListEntry
            {
                RewardType = g.RewardType, RewardId = g.RewardId, RewardNum = g.RewardNum,
            });
        }

        return ExchangeOutcome.Ok(rewardList);
    }
}
