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

namespace SVSim.Database.Repositories.BattlePass;

public sealed class BattlePassRepository : IBattlePassRepository
{
    private readonly SVSimDbContext _db;

    // Process-level cache for the immutable level curve. Bootstrap re-baseline = host restart = cache cleared.
    private static IReadOnlyList<BattlePassLevelEntry>? _curveCache;
    private static readonly SemaphoreSlim _curveCacheLock = new(1, 1);

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

    public async Task<BattlePassSeasonEntry?> GetActiveSeasonAsync(DateTimeOffset when, CancellationToken ct)
    {
        // Use UtcDateTime for the LINQ comparison so the query translates on both Postgres and
        // SQLite. DateTimeOffset arithmetic in LINQ isn't supported by the SQLite provider;
        // DateTime (UTC) is stored and compared as ISO-8601 text which SQLite handles fine.
        var utcNow = when.UtcDateTime;
        var candidates = await _db.BattlePassSeasons
            .AsNoTracking()
            .ToListAsync(ct);
        return candidates
            .Where(s => s.StartDate.UtcDateTime <= utcNow && s.EndDate.UtcDateTime > utcNow)
            .OrderByDescending(s => s.StartDate)
            .FirstOrDefault();
    }

    public Task<BattlePassSeasonEntry?> GetSeasonAsync(int seasonId, CancellationToken ct) =>
        _db.BattlePassSeasons.AsNoTracking().FirstOrDefaultAsync(s => s.Id == seasonId, ct);

    public async Task<List<BattlePassRewardEntry>> GetSeasonRewardsAsync(int seasonId, CancellationToken ct) =>
        await _db.BattlePassRewards.AsNoTracking()
            .Where(r => r.SeasonId == seasonId)
            .OrderBy(r => r.Track).ThenBy(r => r.Level)
            .ToListAsync(ct);

    public async Task<IReadOnlyList<BattlePassLevelEntry>> GetLevelCurveAsync(CancellationToken ct)
    {
        if (_curveCache is not null) return _curveCache;
        await _curveCacheLock.WaitAsync(ct);
        try
        {
            if (_curveCache is null)
            {
                _curveCache = await _db.BattlePassLevels.AsNoTracking()
                    .OrderBy(e => e.Level)
                    .ToListAsync(ct);
            }
            return _curveCache;
        }
        finally { _curveCacheLock.Release(); }
    }

    /// <summary>
    /// Drops the process-level level-curve cache. Tests that seed BattlePassLevels after the
    /// cache has already been populated (by an earlier test's HTTP call) must call this before
    /// re-seeding so the next read fetches fresh rows.
    /// </summary>
    internal static void ResetLevelCurveCache() => _curveCache = null;
}
