using UtopiaCanteenSystem.Models;

namespace UtopiaCanteenSystem.Services;

/// <summary>
/// Resolves current meal session from production (MySQL meal_schedule). Caches schedules per site for 60 seconds.
/// No SQLite; scan validation uses production data only.
/// </summary>
public class DbMealSessionResolver : IMealSessionResolver
{
    private readonly IMealScheduleService _mealScheduleService;
    private readonly TimeSpan _cacheTtl = TimeSpan.FromSeconds(60);

    private readonly Dictionary<string, (List<MealSchedule> Schedules, DateTime ExpiryUtc)> _cache = new(StringComparer.OrdinalIgnoreCase);
    private readonly object _cacheLock = new();

    public DbMealSessionResolver(IMealScheduleService mealScheduleService)
    {
        _mealScheduleService = mealScheduleService;
    }

    /// <inheritdoc />
    public MealSession GetCurrentSession(DateTime nowLocal, string siteId)
    {
        var normalizedSite = (siteId ?? string.Empty).Trim();
        if (string.IsNullOrEmpty(normalizedSite))
            normalizedSite = "01";
        if (normalizedSite.Length == 1 && char.IsDigit(normalizedSite[0]))
            normalizedSite = normalizedSite.PadLeft(2, '0');

        var schedules = GetSchedulesForSiteCached(normalizedSite);
        var t = nowLocal.TimeOfDay;

        foreach (var s in schedules)
        {
            if (!TryParseTime(s.StartTime, out var start) || !TryParseTime(s.EndTime, out var end))
                continue;
            if (t >= start && t < end)
                return (MealSession)s.MealSession;
        }

        return MealSession.None;
    }

    private List<MealSchedule> GetSchedulesForSiteCached(string siteId)
    {
        lock (_cacheLock)
        {
            if (_cache.TryGetValue(siteId, out var entry) && DateTime.UtcNow < entry.ExpiryUtc)
                return entry.Schedules;
        }

        var list = _mealScheduleService.GetActiveSchedulesForSite(siteId).ToList();

        lock (_cacheLock)
        {
            _cache[siteId] = (list, DateTime.UtcNow.Add(_cacheTtl));
        }

        return list;
    }

    private static bool TryParseTime(string value, out TimeSpan time)
    {
        time = TimeSpan.Zero;
        if (string.IsNullOrWhiteSpace(value))
            return false;
        return TimeSpan.TryParse(value.Trim(), null, out time)
               || TimeSpan.TryParse(value.Trim().Replace(".", ":"), null, out time);
    }
}