using NLog;
using StackExchange.Redis;
using System.Globalization;

namespace MP.IOC.Services
{
    public class MetricsCalcService : BackgroundService
    {
        #region Public Constructors

        /// <summary>
        /// Metodo x calcolo metriche/statistiche di esecuzone realtime
        /// </summary>
        /// <param name="stats"></param>
        /// <param name="config"></param>
        /// <param name="mux"></param>
        public MetricsCalcService(RouteStatsManager stats, IConfiguration config, IConnectionMultiplexer mux)
        {
            _stats = stats;
            _config = config;
            _db = mux.GetDatabase();
            _redisBaseKey = _config.GetValue<string>("ServerConf:RedisBaseKey") ?? "MP_IOC";
        }

        #endregion Public Constructors

        #region Protected Methods

        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            var interval = _config.GetValue<int>("RouteMan:MetricCalcIntervalSeconds", 20);
            while (!stoppingToken.IsCancellationRequested)
            {
                try
                {
                    await Task.Delay(TimeSpan.FromSeconds(interval), stoppingToken);
                    var snapshot = _stats.Snapshot();

                    if (snapshot.Count == 0) continue;

                    var adesso = DateTime.Now;
                    var hourStart = new DateTime(adesso.Year, adesso.Month, adesso.Day, adesso.Hour, 0, 0);
                    var dayStart = new DateTime(adesso.Year, adesso.Month, adesso.Day, 0, 0, 0);

                    foreach (var kv in snapshot)
                    {
                        string dest = "IO";
                        string method = "NA";
                        // verifico se ho chiave completo (dest+method) o parziale
                        string rawKey = kv.Key;
                        if (rawKey.Contains("|"))
                        {
                            var splitVal = rawKey.Split("|");
                            dest = splitVal[0];
                            method = splitVal[1];
                        }
                        else
                        {
                            method = rawKey;
                        }
                        var stat = kv.Value;
                        var count = Interlocked.Read(ref stat.Count);
                        var totalMs = stat.TotalDuration.TotalMilliseconds;
                        var maxMs = stat.MaxDuration.TotalMilliseconds;
                        var minMs = (stat.MinDuration == TimeSpan.MaxValue) ? 0 : stat.MinDuration.TotalMilliseconds;

                        Log.Info($"Dest {dest} | Method {method} | Count {count} | TotalDurationMs {totalMs} | MaxDurationMs {maxMs} | MinDurationMs {minMs}");

                        if (_db == null) continue;

                        // Keys
                        var hourKey = HourBucketKey(dest, method, hourStart);
                        var hoursIndex = HoursIndexKey(dest, method);
                        var dayKey = DayBucketKey(dest, dayStart);
                        var daysIndex = DaysIndexKey(dest);

                        // Use batch to reduce roundtrips
                        var batch = _db.CreateBatch();

                        // Increment hash fields (count and totalMs)
                        var taskHourCount = batch.HashIncrementAsync(hourKey, "count", count);
                        var taskHourTotal = batch.HashIncrementAsync(hourKey, "totalMs", totalMs);
                        var taskHourMax = batch.HashSetAsync(hourKey, "maxMs", maxMs.ToString());
                        var taskHourMin = batch.HashSetAsync(hourKey, "minMs", minMs.ToString());

                        var taskDayCount = batch.HashIncrementAsync(dayKey, "count", count);
                        var taskDayTotal = batch.HashIncrementAsync(dayKey, "totalMs", totalMs);
                        var taskDayMax = batch.HashSetAsync(dayKey, "maxMs", maxMs.ToString());
                        var taskDayMin = batch.HashSetAsync(dayKey, "minMs", minMs.ToString());

                        // Add to sorted set indices with score = epoch seconds of bucket start
                        var hourScore = ToEpochSeconds(hourStart);
                        var dayScore = ToEpochSeconds(dayStart);

                        var taskZAddHour = batch.SortedSetAddAsync(hoursIndex, hourKey, hourScore);
                        var taskZAddDay = batch.SortedSetAddAsync(daysIndex, dayKey, dayScore);

                        // Execute batch
                        batch.Execute();

                        // Await tasks to ensure completion
                        await Task.WhenAll(taskHourCount, taskHourTotal, taskHourMax, taskHourMin,
                                          taskDayCount, taskDayTotal, taskDayMax, taskDayMin,
                                          taskZAddHour, taskZAddDay);
                    }

                    _stats.Clear();
                }
                catch (TaskCanceledException) { }
                catch (Exception ex)
                {
                    Log.Error(ex, "Error flushing metrics");
                }
            }
        }

        #endregion Protected Methods

        #region Private Fields

        private static string _redisBaseKey = "";
        private static Logger Log = LogManager.GetCurrentClassLogger();
        private readonly IConfiguration _config;
        private readonly IDatabase _db;
        private readonly RouteStatsManager _stats;

        #endregion Private Fields

        #region Private Methods

        //private static string DayBucketKey(string dest, string method, DateTime dtRif)
        private static string DayBucketKey(string dest, DateTime dtRif)
        {
            return $"{_redisBaseKey}:stats:day:{dest}:{dtRif.ToString("yyyyMMdd", CultureInfo.InvariantCulture)}";
            //return $"{_redisBaseKey}:stats:day:{dest}:{method}:{dtRif.ToString("yyyyMMdd", CultureInfo.InvariantCulture)}";
        }

        //private static string DaysIndexKey(string dest, string method)
        private static string DaysIndexKey(string dest)
        {
            return $"{_redisBaseKey}:stats:days:{dest}";
            //return $"{_redisBaseKey}:stats:days:{dest}:{method}";
        }

        private static string HourBucketKey(string dest, string method, DateTime dtRif)
        {
            return $"{_redisBaseKey}:stats:hour:{dest}:{method}:{dtRif.ToString("yyyyMMddHH", CultureInfo.InvariantCulture)}";
        }

        private static string HoursIndexKey(string dest, string method)
        {
            return $"{_redisBaseKey}:stats:hours:{dest}:{method}";
        }

        private static long ToEpochSeconds(DateTime dt)
        {
            return new DateTimeOffset(dt).ToUnixTimeSeconds();
        }

        #endregion Private Methods
    }
}