using Microsoft.EntityFrameworkCore;
using SVSim.Database.Models;

namespace SVSim.Database.Repositories.Mission;

public sealed class MissionCatalogRepository : IMissionCatalogRepository
{
    private readonly SVSimDbContext _db;

    // Process-level cache for the derived MAX(Level) lookup. Cleared on host restart
    // (re-bootstrap is the only legitimate way to mutate the catalog at runtime).
    private static IReadOnlyDictionary<int, int>? _maxLevelCache;
    private static readonly SemaphoreSlim _maxLevelLock = new(1, 1);

    public MissionCatalogRepository(SVSimDbContext db) { _db = db; }

    public Task<List<MissionCatalogEntry>> GetByLotTypeAsync(int lotType, CancellationToken ct) =>
        _db.MissionCatalog.AsNoTracking().Where(e => e.LotType == lotType).ToListAsync(ct);

    public Task<List<MissionCatalogEntry>> GetByIdsAsync(IReadOnlyCollection<int> ids, CancellationToken ct) =>
        _db.MissionCatalog.AsNoTracking().Where(e => ids.Contains(e.Id)).ToListAsync(ct);

    public Task<MissionCatalogEntry?> GetByIdAsync(int id, CancellationToken ct) =>
        _db.MissionCatalog.AsNoTracking().FirstOrDefaultAsync(e => e.Id == id, ct);

    public Task<List<MissionCatalogEntry>> GetByEventTypesAsync(IReadOnlyCollection<string> eventTypes, CancellationToken ct) =>
        _db.MissionCatalog.AsNoTracking()
            .Where(e => e.EventType != null && eventTypes.Contains(e.EventType))
            .ToListAsync(ct);

    public Task<List<AchievementCatalogEntry>> GetAchievementsByEventTypesAsync(IReadOnlyCollection<string> eventTypes, CancellationToken ct) =>
        _db.AchievementCatalog.AsNoTracking()
            .Where(e => e.EventType != null && eventTypes.Contains(e.EventType))
            .ToListAsync(ct);

    public Task<List<int>> GetAllAchievementTypesAsync(CancellationToken ct) =>
        _db.AchievementCatalog.AsNoTracking()
            .Select(e => e.AchievementType).Distinct()
            .ToListAsync(ct);

    public async Task<IReadOnlyDictionary<int, int>> GetMaxLevelByAchievementTypeAsync(CancellationToken ct)
    {
        if (_maxLevelCache is not null) return _maxLevelCache;
        await _maxLevelLock.WaitAsync(ct);
        try
        {
            if (_maxLevelCache is null)
            {
                var pairs = await _db.AchievementCatalog.AsNoTracking()
                    .GroupBy(e => e.AchievementType)
                    .Select(g => new { Type = g.Key, Max = g.Max(e => e.Level) })
                    .ToListAsync(ct);
                _maxLevelCache = pairs.ToDictionary(p => p.Type, p => p.Max);
            }
            return _maxLevelCache;
        }
        finally { _maxLevelLock.Release(); }
    }

    public async Task<IReadOnlyDictionary<int, int>> GetMinLevelByAchievementTypeAsync(CancellationToken ct)
    {
        var pairs = await _db.AchievementCatalog.AsNoTracking()
            .GroupBy(e => e.AchievementType)
            .Select(g => new { Type = g.Key, Min = g.Min(e => e.Level) })
            .ToListAsync(ct);
        return pairs.ToDictionary(p => p.Type, p => p.Min);
    }

    public Task<AchievementCatalogEntry?> GetAchievementAsync(int achievementType, int level, CancellationToken ct) =>
        _db.AchievementCatalog.AsNoTracking()
            .FirstOrDefaultAsync(e => e.AchievementType == achievementType && e.Level == level, ct);

    public Task<List<BattlePassMonthlyMissionEntry>> GetMonthlyMissionsAsync(int year, int month, CancellationToken ct) =>
        _db.BattlePassMonthlyMissions.AsNoTracking()
            .Where(e => e.Year == year && e.Month == month)
            .OrderBy(e => e.OrderNum).ToListAsync(ct);
}