using IW4MAdmin.Plugins.Stats.Cheat;
using IW4MAdmin.Plugins.Stats.Models;
using IW4MAdmin.Plugins.Stats.Web.Dtos;
using Microsoft.EntityFrameworkCore;
using SharedLibraryCore;
using SharedLibraryCore.Database;
using SharedLibraryCore.Database.Models;
using SharedLibraryCore.Helpers;
using SharedLibraryCore.Interfaces;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Threading;
using System.Threading.Tasks;

namespace IW4MAdmin.Plugins.Stats.Helpers
{
    public class StatManager
    {
        private readonly ConcurrentDictionary<long, ServerStats> _servers;
        private readonly ILogger _log;
        private static List<EFServer> serverModels;
        private readonly SemaphoreSlim OnProcessingPenalty;
        private readonly SemaphoreSlim OnProcessingSensitive;
        private readonly List<EFClientKill> _hitCache;

        public StatManager(IManager mgr)
        {
            _servers = new ConcurrentDictionary<long, ServerStats>();
            _hitCache = new List<EFClientKill>();
            _log = mgr.GetLogger(0);
            OnProcessingPenalty = new SemaphoreSlim(1, 1);
            OnProcessingSensitive = new SemaphoreSlim(1, 1);
        }

        private void SetupServerIds()
        {
            using (var ctx = new DatabaseContext(disableTracking: true))
            {
                serverModels = ctx.Set<EFServer>().ToList();
            }
        }

        public EFClientStatistics GetClientStats(int clientId, long serverId)
        {
            return _servers[serverId].PlayerStats[clientId];
        }

        public static Expression<Func<EFRating, bool>> GetRankingFunc(long? serverId = null)
        {
            var fifteenDaysAgo = DateTime.UtcNow.AddDays(-15);
            return (r) => r.ServerId == serverId &&
                r.When > fifteenDaysAgo &&
                r.RatingHistory.Client.Level != EFClient.Permission.Banned &&
                r.Newest &&
                r.ActivityAmount >= Plugin.Config.Configuration().TopPlayersMinPlayTime;
        }

        /// <summary>
        /// gets a ranking across all servers for given client id
        /// </summary>
        /// <param name="clientId">client id of the player</param>
        /// <returns></returns>
        public static async Task<int> GetClientOverallRanking(int clientId)
        {
            using (var context = new DatabaseContext(true))
            {
                var clientPerformance = await context.Set<EFRating>()
                    .Where(r => r.RatingHistory.ClientId == clientId)
                    .Where(r => r.ServerId == null)
                    .Where(r => r.Newest)
                    .Select(r => r.Performance)
                    .FirstOrDefaultAsync();

                if (clientPerformance != 0)
                {
                    var iqClientRanking = context.Set<EFRating>()
                        .Where(r => r.RatingHistory.ClientId != clientId)
                        .Where(r => r.Performance > clientPerformance)
                        .Where(GetRankingFunc());

                    return await iqClientRanking.CountAsync() + 1;
                }

                return 0;
            }
        }

        public async Task<List<TopStatsInfo>> GetTopStats(int start, int count, long? serverId = null)
        {
            using (var context = new DatabaseContext(true))
            {
                // setup the query for the clients within the given rating range
                var iqClientRatings = (from rating in context.Set<EFRating>()
                    .Where(GetRankingFunc(serverId))
                                       select new
                                       {
                                           rating.RatingHistory.ClientId,
                                           rating.RatingHistory.Client.CurrentAlias.Name,
                                           rating.RatingHistory.Client.LastConnection,
                                           rating.Performance,
                                       })
                    .OrderByDescending(c => c.Performance)
                    .Skip(start)
                    .Take(count);
#if DEBUG == true
                var clientRatingsSql = iqClientRatings.ToSql();
#endif
                // materialized list
                var clientRatings = await iqClientRatings.ToListAsync();

                // get all the unique client ids that are in the top stats
                var clientIds = clientRatings
                    .GroupBy(r => r.ClientId)
                    .Select(r => r.First().ClientId)
                    .ToList();

                var iqRatingInfo = from rating in context.Set<EFRating>()
                                   where clientIds.Contains(rating.RatingHistory.ClientId)
                                   where rating.ServerId == serverId
                                   select new
                                   {
                                       rating.Ranking,
                                       rating.Performance,
                                       rating.RatingHistory.ClientId,
                                       rating.When
                                   };

#if DEBUG == true
                var ratingQuery = iqRatingInfo.ToSql();
#endif

                var ratingInfo = (await iqRatingInfo.ToListAsync())
                    .GroupBy(r => r.ClientId)
                    .Select(grp => new
                    {
                        grp.Key,
                        Ratings = grp.Select(r => new { r.Performance, r.Ranking, r.When })
                    });

                var iqStatsInfo = (from stat in context.Set<EFClientStatistics>()
                                   where clientIds.Contains(stat.ClientId)
                                   where stat.Kills > 0 || stat.Deaths > 0
                                   group stat by stat.ClientId into s
                                   select new
                                   {
                                       ClientId = s.Key,
                                       Kills = s.Sum(c => c.Kills),
                                       Deaths = s.Sum(c => c.Deaths),
                                       KDR = s.Sum(c => (c.Kills / (double)(c.Deaths == 0 ? 1 : c.Deaths)) * c.TimePlayed) / s.Sum(c => c.TimePlayed),
                                       TotalTimePlayed = s.Sum(c => c.TimePlayed)
                                   });

#if DEBUG == true
                var statsInfoSql = iqStatsInfo.ToSql();
#endif
                var topPlayers = await iqStatsInfo.ToListAsync();

                var clientRatingsDict = clientRatings.ToDictionary(r => r.ClientId);
                var finished = topPlayers.Select(s => new TopStatsInfo()
                {
                    ClientId = s.ClientId,
                    Id = (int?)serverId ?? 0,
                    Deaths = s.Deaths,
                    Kills = s.Kills,
                    KDR = Math.Round(s.KDR, 2),
                    LastSeen = Utilities.GetTimePassed(clientRatingsDict[s.ClientId].LastConnection, false),
                    Name = clientRatingsDict[s.ClientId].Name,
                    Performance = Math.Round(clientRatingsDict[s.ClientId].Performance, 2),
                    RatingChange = ratingInfo.First(r => r.Key == s.ClientId).Ratings.First().Ranking - ratingInfo.First(r => r.Key == s.ClientId).Ratings.Last().Ranking,
                    PerformanceHistory = ratingInfo.First(r => r.Key == s.ClientId).Ratings.Count() > 1 ?
                        ratingInfo.First(r => r.Key == s.ClientId).Ratings.OrderBy(r => r.When).Select(r => r.Performance).ToList() :
                       new List<double>() { clientRatingsDict[s.ClientId].Performance, clientRatingsDict[s.ClientId].Performance },
                    TimePlayed = Math.Round(s.TotalTimePlayed / 3600.0, 1).ToString("#,##0"),
                })
                .OrderByDescending(r => r.Performance)
                .ToList();

                // set the ranking numerically
                int i = start + 1;
                foreach (var stat in finished)
                {
                    stat.Ranking = i;
                    i++;
                }

                return finished;
            }
        }

        /// <summary>
        /// Add a server to the StatManager server pool
        /// </summary>
        /// <param name="sv"></param>
        public void AddServer(Server sv)
        {
            // insert the server if it does not exist
            try
            {
                if (serverModels == null)
                {
                    SetupServerIds();
                }

                long serverId = GetIdForServer(sv);
                EFServer server;

                using (var ctx = new DatabaseContext(disableTracking: true))
                {
                    var serverSet = ctx.Set<EFServer>();
                    // get the server from the database if it exists, otherwise create and insert a new one
                    server = serverSet.FirstOrDefault(s => s.ServerId == serverId);

                    // the server might be using legacy server id
                    if (server == null)
                    {
                        server = serverSet.FirstOrDefault(s => s.EndPoint == sv.ToString());

                        if (server != null)
                        {
                            // this provides a way to identify legacy server entries
                            server.EndPoint = sv.ToString();
                            ctx.Update(server);
                            ctx.SaveChanges();
                        }
                    }

                    // server has never been added before
                    if (server == null)
                    {
                        server = new EFServer()
                        {
                            Port = sv.Port,
                            EndPoint = sv.ToString(),
                            ServerId = serverId,
                            GameName = sv.GameName
                        };

                        server = serverSet.Add(server).Entity;
                        // this doesn't need to be async as it's during initialization
                        ctx.SaveChanges();
                    }

                    // we want to set the gamename up if it's never been set, or it changed
                    else if (!server.GameName.HasValue || server.GameName.HasValue && server.GameName.Value != sv.GameName)
                    {
                        server.GameName = sv.GameName;
                        ctx.Entry(server).Property(_prop => _prop.GameName).IsModified = true;
                        ctx.SaveChanges();
                    }
                }

                // check to see if the stats have ever been initialized
                var serverStats = InitializeServerStats(server.ServerId);

                _servers.TryAdd(serverId, new ServerStats(server, serverStats)
                {
                    IsTeamBased = sv.Gametype != "dm"
                });
            }

            catch (Exception e)
            {
                _log.WriteError($"{Utilities.CurrentLocalization.LocalizationIndex["PLUGIN_STATS_ERROR_ADD"]} - {e.Message}");
                _log.WriteDebug(e.GetExceptionInfo());
            }
        }

        /// <summary>
        /// Add Player to the player stats 
        /// </summary>
        /// <param name="pl">Player to add/retrieve stats for</param>
        /// <returns>EFClientStatistic of specified player</returns>
        public async Task<EFClientStatistics> AddPlayer(EFClient pl)
        {
            await OnProcessingSensitive.WaitAsync();

            try
            {
                long serverId = GetIdForServer(pl.CurrentServer);

                if (!_servers.ContainsKey(serverId))
                {
                    _log.WriteError($"[Stats::AddPlayer] Server with id {serverId} could not be found");
                    return null;
                }

                var playerStats = _servers[serverId].PlayerStats;
                var detectionStats = _servers[serverId].PlayerDetections;

                if (playerStats.ContainsKey(pl.ClientId))
                {
                    _log.WriteWarning($"Duplicate ClientId in stats {pl.ClientId}");
                    return playerStats[pl.ClientId];
                }

                // get the client's stats from the database if it exists, otherwise create and attach a new one
                // if this fails we want to throw an exception

                EFClientStatistics clientStats;

                using (var ctx = new DatabaseContext(disableTracking: true))
                {
                    var clientStatsSet = ctx.Set<EFClientStatistics>();
                    clientStats = clientStatsSet
                        .Include(cl => cl.HitLocations)
                        .FirstOrDefault(c => c.ClientId == pl.ClientId && c.ServerId == serverId);

                    if (clientStats == null)
                    {
                        clientStats = new EFClientStatistics()
                        {
                            Active = true,
                            ClientId = pl.ClientId,
                            Deaths = 0,
                            Kills = 0,
                            ServerId = serverId,
                            Skill = 0.0,
                            SPM = 0.0,
                            EloRating = 200.0,
                            HitLocations = Enum.GetValues(typeof(IW4Info.HitLocation)).OfType<IW4Info.HitLocation>().Select(hl => new EFHitLocationCount()
                            {
                                Active = true,
                                HitCount = 0,
                                Location = hl
                            }).ToList()
                        };

                        // insert if they've not been added
                        clientStats = clientStatsSet.Add(clientStats).Entity;
                        await ctx.SaveChangesAsync();

                        if (!playerStats.TryAdd(clientStats.ClientId, clientStats))
                        {
                            _log.WriteWarning("Adding new client to stats failed");
                        }
                    }

                    else
                    {
                        if (!playerStats.TryAdd(clientStats.ClientId, clientStats))
                        {
                            _log.WriteWarning("Adding pre-existing client to stats failed");
                        }
                    }

                    // migration for previous existing stats
                    if (clientStats.HitLocations.Count == 0)
                    {
                        clientStats.HitLocations = Enum.GetValues(typeof(IW4Info.HitLocation)).OfType<IW4Info.HitLocation>()
                            .Select(hl => new EFHitLocationCount()
                            {
                                Active = true,
                                HitCount = 0,
                                Location = hl
                            })
                            .ToList();

                        ctx.Update(clientStats);
                        await ctx.SaveChangesAsync();
                    }

                    // for stats before rating
                    if (clientStats.EloRating == 0.0)
                    {
                        clientStats.EloRating = clientStats.Skill;
                    }

                    if (clientStats.RollingWeightedKDR == 0)
                    {
                        clientStats.RollingWeightedKDR = clientStats.KDR;
                    }

                    // set these on connecting
                    clientStats.LastActive = DateTime.UtcNow;
                    clientStats.LastStatCalculation = DateTime.UtcNow;
                    clientStats.SessionScore = pl.Score;
                    clientStats.LastScore = pl.Score;

                    if (!detectionStats.TryAdd(pl.ClientId, new Detection(_log, clientStats)))
                    {
                        _log.WriteWarning("Could not add client to detection");
                    }

                    pl.CurrentServer.Logger.WriteInfo($"Adding {pl} to stats");
                }

                return clientStats;
            }

            catch (Exception ex)
            {
                _log.WriteWarning("Could not add client to stats");
                _log.WriteDebug(ex.GetExceptionInfo());
            }

            finally
            {
                OnProcessingSensitive.Release(1);
            }

            return null;
        }

        /// <summary>
        /// Perform stat updates for disconnecting client
        /// </summary>
        /// <param name="pl">Disconnecting client</param>
        /// <returns></returns>
        public async Task RemovePlayer(EFClient pl)
        {
            pl.CurrentServer.Logger.WriteInfo($"Removing {pl} from stats");

            long serverId = GetIdForServer(pl.CurrentServer);
            var playerStats = _servers[serverId].PlayerStats;
            var detectionStats = _servers[serverId].PlayerDetections;
            var serverStats = _servers[serverId].ServerStatistics;

            if (!playerStats.ContainsKey(pl.ClientId))
            {
                pl.CurrentServer.Logger.WriteWarning($"Client disconnecting not in stats {pl}");
                // remove the client from the stats dictionary as they're leaving
                playerStats.TryRemove(pl.ClientId, out _);
                detectionStats.TryRemove(pl.ClientId, out _);
                return;
            }

            // get individual client's stats
            var clientStats = playerStats[pl.ClientId];

            // remove the client from the stats dictionary as they're leaving
            playerStats.TryRemove(pl.ClientId, out _);
            detectionStats.TryRemove(pl.ClientId, out _);

            // sync their stats before they leave
            clientStats = UpdateStats(clientStats);
            await SaveClientStats(clientStats);

            // increment the total play time
            serverStats.TotalPlayTime += pl.ConnectionLength;
        }

        private static async Task SaveClientStats(EFClientStatistics clientStats)
        {
            using (var ctx = new DatabaseContext(disableTracking: true))
            {
                ctx.Update(clientStats);
                await ctx.SaveChangesAsync();
            }
        }

        public void AddDamageEvent(string eventLine, int attackerClientId, int victimClientId, long serverId)
        {
        }

        /// <summary>
        /// Process stats for kill event
        /// </summary>
        /// <returns></returns>
        public async Task AddScriptHit(bool isDamage, DateTime time, EFClient attacker, EFClient victim, long serverId, string map, string hitLoc, string type,
            string damage, string weapon, string killOrigin, string deathOrigin, string viewAngles, string offset, string isKillstreakKill, string Ads,
            string fraction, string visibilityPercentage, string snapAngles)
        {
            Vector3 vDeathOrigin = null;
            Vector3 vKillOrigin = null;
            Vector3 vViewAngles = null;

            try
            {
                vDeathOrigin = Vector3.Parse(deathOrigin);
                vKillOrigin = Vector3.Parse(killOrigin);
                vViewAngles = Vector3.Parse(viewAngles).FixIW4Angles();
            }

            catch (FormatException)
            {
                _log.WriteWarning("Could not parse kill or death origin or viewangle vectors");
                _log.WriteDebug($"Kill - {killOrigin} Death - {deathOrigin} ViewAngle - {viewAngles}");
                await AddStandardKill(attacker, victim);
                return;
            }

            var snapshotAngles = new List<Vector3>();

            try
            {
                foreach (string angle in snapAngles.Split(':', StringSplitOptions.RemoveEmptyEntries))
                {
                    snapshotAngles.Add(Vector3.Parse(angle).FixIW4Angles());
                }
            }

            catch (FormatException)
            {
                _log.WriteWarning("Could not parse snapshot angles");
                return;
            }

            var hit = new EFClientKill()
            {
                Active = true,
                AttackerId = attacker.ClientId,
                VictimId = victim.ClientId,
                ServerId = serverId,
                //Map = ParseEnum<IW4Info.MapName>.Get(map, typeof(IW4Info.MapName)),
                DeathOrigin = vDeathOrigin,
                KillOrigin = vKillOrigin,
                DeathType = ParseEnum<IW4Info.MeansOfDeath>.Get(type, typeof(IW4Info.MeansOfDeath)),
                Damage = int.Parse(damage),
                HitLoc = ParseEnum<IW4Info.HitLocation>.Get(hitLoc, typeof(IW4Info.HitLocation)),
                Weapon = ParseEnum<IW4Info.WeaponName>.Get(weapon, typeof(IW4Info.WeaponName)),
                ViewAngles = vViewAngles,
                TimeOffset = long.Parse(offset),
                When = time,
                IsKillstreakKill = isKillstreakKill[0] != '0',
                AdsPercent = float.Parse(Ads, System.Globalization.CultureInfo.InvariantCulture),
                Fraction = double.Parse(fraction, System.Globalization.CultureInfo.InvariantCulture),
                VisibilityPercentage = double.Parse(visibilityPercentage, System.Globalization.CultureInfo.InvariantCulture),
                IsKill = !isDamage,
                AnglesList = snapshotAngles
            };

            if (hit.HitLoc == IW4Info.HitLocation.shield)
            {
                // we don't care about shield hits
                return;
            }

            if (!isDamage)
            {
                await AddStandardKill(attacker, victim);
            }

            if (hit.IsKillstreakKill)
            {
                return;
            }

            // incase the add player event get delayed
            if (!_servers[serverId].PlayerStats.ContainsKey(attacker.ClientId))
            {
                await AddPlayer(attacker);
            }

            var clientDetection = _servers[serverId].PlayerDetections[attacker.ClientId];
            var clientStats = _servers[serverId].PlayerStats[attacker.ClientId];

            // increment their hit count
            if (hit.DeathType == IW4Info.MeansOfDeath.MOD_PISTOL_BULLET ||
                hit.DeathType == IW4Info.MeansOfDeath.MOD_RIFLE_BULLET ||
                hit.DeathType == IW4Info.MeansOfDeath.MOD_HEAD_SHOT)
            {
                clientStats.HitLocations.Single(hl => hl.Location == hit.HitLoc).HitCount += 1;
            }

            if (clientStats.SessionKills % Detection.MAX_TRACKED_HIT_COUNT == 0)
            {
                await SaveClientStats(clientStats);
            }

            try
            {
                if (Plugin.Config.Configuration().StoreClientKills)
                {
                    _hitCache.Add(hit);

                    if (_hitCache.Count > Detection.MAX_TRACKED_HIT_COUNT)
                    {
                        OnProcessingPenalty.Wait();
                        using (var ctx = new DatabaseContext())
                        {
                            ctx.AddRange(_hitCache);
                            await ctx.SaveChangesAsync();
                        }

                        _hitCache.Clear();
                        OnProcessingPenalty.Release();
                    }
                }


                if (Plugin.Config.Configuration().EnableAntiCheat && !attacker.IsBot && attacker.ClientId != victim.ClientId)
                {
                    DetectionPenaltyResult result = new DetectionPenaltyResult() { ClientPenalty = EFPenalty.PenaltyType.Any };
#if DEBUG
                    if (clientDetection.TrackedHits.Count > 0)
#else
                    if (clientDetection.TrackedHits.Count > Detection.MAX_TRACKED_HIT_COUNT)
#endif
                    {
                        while (clientDetection.TrackedHits.Count > 0)
                        {
                            await OnProcessingPenalty.WaitAsync();

                            var oldestHit = clientDetection.TrackedHits.OrderBy(_hits => _hits.TimeOffset).First();
                            clientDetection.TrackedHits.Remove(oldestHit);

                            result = clientDetection.ProcessHit(oldestHit, isDamage);
                            await ApplyPenalty(result, attacker);

                            if (clientDetection.Tracker.HasChanges && result.ClientPenalty != EFPenalty.PenaltyType.Any)
                            {
                                using (var ctx = new DatabaseContext())
                                {
                                    SaveTrackedSnapshots(clientDetection, ctx);
                                    await ctx.SaveChangesAsync();
                                }

                                if (result.ClientPenalty == EFPenalty.PenaltyType.Ban)
                                {
                                    OnProcessingPenalty.Release(1);
                                    break;
                                }
                            }

                            OnProcessingPenalty.Release(1);
                        }
                    }

                    else
                    {
                        clientDetection.TrackedHits.Add(hit);
                    }
                }
            }

            catch (Exception ex)
            {
                _log.WriteError("Could not save hit or AC info");
                _log.WriteDebug(ex.GetExceptionInfo());
            }
        }

        async Task ApplyPenalty(DetectionPenaltyResult penalty, EFClient attacker)
        {
            var penaltyClient = Utilities.IW4MAdminClient(attacker.CurrentServer);
            switch (penalty.ClientPenalty)
            {
                case EFPenalty.PenaltyType.Ban:
                    if (attacker.Level == EFClient.Permission.Banned)
                    {
                        break;
                    }

                    penaltyClient.AdministeredPenalties = new List<EFPenalty>()
                    {
                        new EFPenalty()
                        {
                            AutomatedOffense = penalty.Type == Detection.DetectionType.Bone ?
                                $"{penalty.Type}-{(int)penalty.Location}-{Math.Round(penalty.Value, 2)}@{penalty.HitCount}" :
                                $"{penalty.Type}-{Math.Round(penalty.Value, 2)}@{penalty.HitCount}",
                        }
                    };

                    await attacker.Ban(Utilities.CurrentLocalization.LocalizationIndex["PLUGIN_STATS_CHEAT_DETECTED"], penaltyClient, false).WaitAsync(Utilities.DefaultCommandTimeout, attacker.CurrentServer.Manager.CancellationToken);
                    break;
                case EFPenalty.PenaltyType.Flag:
                    if (attacker.Level != EFClient.Permission.User)
                    {
                        break;
                    }

                    string flagReason = penalty.Type == Cheat.Detection.DetectionType.Bone ?
                            $"{penalty.Type}-{(int)penalty.Location}-{Math.Round(penalty.Value, 2)}@{penalty.HitCount}" :
                            $"{penalty.Type}-{Math.Round(penalty.Value, 2)}@{penalty.HitCount}";

                    await attacker.Flag(flagReason, penaltyClient, new TimeSpan(168, 0, 0)).WaitAsync(Utilities.DefaultCommandTimeout, attacker.CurrentServer.Manager.CancellationToken);
                    break;
            }
        }

        void SaveTrackedSnapshots(Detection clientDetection, DatabaseContext ctx)
        {
            // todo: why does this cause duplicate primary key
            _ = clientDetection.Tracker.GetNextChange();
            EFACSnapshot change;
            while ((change = clientDetection.Tracker.GetNextChange()) != default(EFACSnapshot))
            {

                if (change.HitOrigin.Vector3Id > 0)
                {
                    change.HitOriginId = change.HitOrigin.Vector3Id;
                    ctx.Attach(change.HitOrigin);
                }

                else if (change.HitOrigin.Vector3Id == 0)
                {
                    ctx.Add(change.HitOrigin);
                }

                if (change.HitDestination.Vector3Id > 0)
                {
                    change.HitDestinationId = change.HitDestination.Vector3Id;
                    ctx.Attach(change.HitDestination);
                }

                else if (change.HitDestination.Vector3Id == 0)
                {
                    ctx.Add(change.HitOrigin);
                }

                if (change.CurrentViewAngle.Vector3Id > 0)
                {
                    change.CurrentViewAngleId = change.CurrentViewAngle.Vector3Id;
                    ctx.Attach(change.CurrentViewAngle);
                }

                else if (change.CurrentViewAngle.Vector3Id == 0)
                {
                    ctx.Add(change.HitOrigin);
                }

                if (change.LastStrainAngle.Vector3Id > 0)
                {
                    change.LastStrainAngleId = change.LastStrainAngle.Vector3Id;
                    ctx.Attach(change.LastStrainAngle);
                }

                else if (change.LastStrainAngle.Vector3Id == 0)
                {
                    ctx.Add(change.HitOrigin);
                }

                ctx.Add(change);
            }
        }

        public async Task AddStandardKill(EFClient attacker, EFClient victim)
        {
            long serverId = GetIdForServer(attacker.CurrentServer);

            EFClientStatistics attackerStats = null;
            if (!_servers[serverId].PlayerStats.ContainsKey(attacker.ClientId))
            {
                attackerStats = await AddPlayer(attacker);
            }

            else
            {
                attackerStats = _servers[serverId].PlayerStats[attacker.ClientId];
            }

            EFClientStatistics victimStats = null;
            if (!_servers[serverId].PlayerStats.ContainsKey(victim.ClientId))
            {
                victimStats = await AddPlayer(victim);
            }

            else
            {
                victimStats = _servers[serverId].PlayerStats[victim.ClientId];
            }

#if DEBUG
            _log.WriteDebug("Calculating standard kill");
#endif

            // update the total stats
            _servers[serverId].ServerStatistics.TotalKills += 1;

            // this happens when the round has changed
            if (attackerStats.SessionScore == 0)
            {
                attackerStats.LastScore = 0;
            }

            if (victimStats.SessionScore == 0)
            {
                victimStats.LastScore = 0;
            }

            attackerStats.SessionScore = attacker.Score;
            victimStats.SessionScore = victim.Score;

            // calculate for the clients
            CalculateKill(attackerStats, victimStats);
            // this should fix the negative SPM
            // updates their last score after being calculated
            attackerStats.LastScore = attacker.Score;
            victimStats.LastScore = victim.Score;

            // show encouragement/discouragement
            string streakMessage = (attackerStats.ClientId != victimStats.ClientId) ?
                StreakMessage.MessageOnStreak(attackerStats.KillStreak, attackerStats.DeathStreak) :
                StreakMessage.MessageOnStreak(-1, -1);

            if (streakMessage != string.Empty)
            {
                attacker.Tell(streakMessage);
            }

            // fixme: why?
            if (double.IsNaN(victimStats.SPM) || double.IsNaN(victimStats.Skill))
            {
                _log.WriteDebug($"[StatManager::AddStandardKill] victim SPM/SKILL {victimStats.SPM} {victimStats.Skill}");
                victimStats.SPM = 0.0;
                victimStats.Skill = 0.0;
            }

            if (double.IsNaN(attackerStats.SPM) || double.IsNaN(attackerStats.Skill))
            {
                _log.WriteDebug($"[StatManager::AddStandardKill] attacker SPM/SKILL {victimStats.SPM} {victimStats.Skill}");
                attackerStats.SPM = 0.0;
                attackerStats.Skill = 0.0;
            }

            // update their performance 
#if !DEBUG
            if ((DateTime.UtcNow - attackerStats.LastStatHistoryUpdate).TotalMinutes >= 2.5)
#else
            if ((DateTime.UtcNow - attackerStats.LastStatHistoryUpdate).TotalMinutes >= 0.1)
#endif
            {
                attackerStats.LastStatHistoryUpdate = DateTime.UtcNow;
                await UpdateStatHistory(attacker, attackerStats);
            }
        }

        /// <summary>
        /// Update the invidual and average stat history for a client
        /// </summary>
        /// <param name="client">client to update</param>
        /// <param name="clientStats">stats of client that is being updated</param>
        /// <returns></returns>
        private async Task UpdateStatHistory(EFClient client, EFClientStatistics clientStats)
        {
            int currentSessionTime = (int)(DateTime.UtcNow - client.LastConnection).TotalSeconds;

            // don't update their stat history if they haven't played long
            //#if DEBUG == false
            if (currentSessionTime < 60)
            {
                return;
            }
            //#endif

            int currentServerTotalPlaytime = clientStats.TimePlayed + currentSessionTime;

            using (var ctx = new DatabaseContext())
            {
                // select the rating history for client
                var iqHistoryLink = from history in ctx.Set<EFClientRatingHistory>()
                                     .Include(h => h.Ratings)
                                    where history.ClientId == client.ClientId
                                    select history;

                // get the client ratings
                var clientHistory = await iqHistoryLink
                    .FirstOrDefaultAsync() ?? new EFClientRatingHistory()
                    {
                        Active = true,
                        ClientId = client.ClientId,
                        Ratings = new List<EFRating>()
                    };

                // it's the first time they've played
                if (clientHistory.RatingHistoryId == 0)
                {
                    ctx.Add(clientHistory);
                }

                #region INDIVIDUAL_SERVER_PERFORMANCE
                // get the client ranking for the current server
                int individualClientRanking = await ctx.Set<EFRating>()
                   .Where(GetRankingFunc(clientStats.ServerId))
                   // ignore themselves in the query
                   .Where(c => c.RatingHistory.ClientId != client.ClientId)
                   .Where(c => c.Performance > clientStats.Performance)
                   .CountAsync() + 1;

                // limit max history per server to 40
                if (clientHistory.Ratings.Count(r => r.ServerId == clientStats.ServerId) >= 40)
                {
                    // select the oldest one
                    var ratingToRemove = clientHistory.Ratings
                        .Where(r => r.ServerId == clientStats.ServerId)
                        .OrderBy(r => r.When)
                        .First();

                    ctx.Remove(ratingToRemove);
                }

                // set the previous newest to false
                var ratingToUnsetNewest = clientHistory.Ratings
                    .Where(r => r.ServerId == clientStats.ServerId)
                    .OrderByDescending(r => r.When)
                    .FirstOrDefault();

                if (ratingToUnsetNewest != null)
                {
                    if (ratingToUnsetNewest.Newest)
                    {
                        ctx.Update(ratingToUnsetNewest);
                        ctx.Entry(ratingToUnsetNewest).Property(r => r.Newest).IsModified = true;
                        ratingToUnsetNewest.Newest = false;
                    }
                }

                var newServerRating = new EFRating()
                {
                    Performance = clientStats.Performance,
                    Ranking = individualClientRanking,
                    Active = true,
                    Newest = true,
                    ServerId = clientStats.ServerId,
                    RatingHistoryId = clientHistory.RatingHistoryId,
                    ActivityAmount = currentServerTotalPlaytime,
                };

                // add new rating for current server
                ctx.Add(newServerRating);

                #endregion
                #region OVERALL_RATING
                // select all performance & time played for current client
                var iqClientStats = from stats in ctx.Set<EFClientStatistics>()
                                    where stats.ClientId == client.ClientId
                                    where stats.ServerId != clientStats.ServerId
                                    select new
                                    {
                                        stats.Performance,
                                        stats.TimePlayed
                                    };

                var clientStatsList = await iqClientStats.ToListAsync();

                // add the current server's so we don't have to pull it frmo the database
                clientStatsList.Add(new
                {
                    clientStats.Performance,
                    TimePlayed = currentServerTotalPlaytime
                });

                // weight the overall performance based on play time
                double performanceAverage = clientStatsList.Sum(p => (p.Performance * p.TimePlayed)) / clientStatsList.Sum(p => p.TimePlayed);

                // shouldn't happen but just in case the sum of time played is 0
                if (double.IsNaN(performanceAverage))
                {
                    performanceAverage = clientStatsList.Average(p => p.Performance);
                }

                int overallClientRanking = await ctx.Set<EFRating>()
                     .Where(GetRankingFunc())
                     .Where(r => r.RatingHistory.ClientId != client.ClientId)
                     .Where(r => r.Performance > performanceAverage)
                     .CountAsync() + 1;

                // limit max average history to 40
                if (clientHistory.Ratings.Count(r => r.ServerId == null) >= 40)
                {
                    var ratingToRemove = clientHistory.Ratings
                        .Where(r => r.ServerId == null)
                        .OrderBy(r => r.When)
                        .First();

                    ctx.Remove(ratingToRemove);
                }

                // set the previous average newest to false
                ratingToUnsetNewest = clientHistory.Ratings
                    .Where(r => r.ServerId == null)
                    .OrderByDescending(r => r.When)
                    .FirstOrDefault();

                if (ratingToUnsetNewest != null)
                {
                    if (ratingToUnsetNewest.Newest)
                    {
                        ctx.Update(ratingToUnsetNewest);
                        ctx.Entry(ratingToUnsetNewest).Property(r => r.Newest).IsModified = true;
                        ratingToUnsetNewest.Newest = false;
                    }
                }

                // add new average rating
                var averageRating = new EFRating()
                {
                    Active = true,
                    Newest = true,
                    Performance = performanceAverage,
                    Ranking = overallClientRanking,
                    ServerId = null,
                    RatingHistoryId = clientHistory.RatingHistoryId,
                    ActivityAmount = clientStatsList.Sum(s => s.TimePlayed)
                };

                ctx.Add(averageRating);
                #endregion

                await ctx.SaveChangesAsync();
            }
        }

        /// <summary>
        /// Performs the incrementation of kills and deaths for client statistics
        /// </summary>
        /// <param name="attackerStats">Stats of the attacker</param>
        /// <param name="victimStats">Stats of the victim</param>
        public void CalculateKill(EFClientStatistics attackerStats, EFClientStatistics victimStats)
        {
            bool suicide = attackerStats.ClientId == victimStats.ClientId;

            // only update their kills if they didn't kill themselves
            if (!suicide)
            {
                attackerStats.Kills += 1;
                attackerStats.SessionKills += 1;
                attackerStats.KillStreak += 1;
                attackerStats.DeathStreak = 0;
            }

            victimStats.Deaths += 1;
            victimStats.SessionDeaths += 1;
            victimStats.DeathStreak += 1;
            victimStats.KillStreak = 0;

            // process the attacker's stats after the kills
            attackerStats = UpdateStats(attackerStats);

            // calulate elo
            if (_servers[attackerStats.ServerId].PlayerStats.Count > 1)
            {
                #region DEPRECATED
                /* var validAttackerLobbyRatings = Servers[attackerStats.ServerId].PlayerStats
                     .Where(cs => cs.Value.ClientId != attackerStats.ClientId)
                     .Where(cs =>
                         Servers[attackerStats.ServerId].IsTeamBased ?
                         cs.Value.Team != attackerStats.Team :
                         cs.Value.Team != IW4Info.Team.Spectator)
                     .Where(cs => cs.Value.Team != IW4Info.Team.Spectator);

                 double attackerLobbyRating = validAttackerLobbyRatings.Count() > 0 ?
                     validAttackerLobbyRatings.Average(cs => cs.Value.EloRating) :
                     attackerStats.EloRating;

                 var validVictimLobbyRatings = Servers[victimStats.ServerId].PlayerStats
                     .Where(cs => cs.Value.ClientId != victimStats.ClientId)
                     .Where(cs =>
                         Servers[attackerStats.ServerId].IsTeamBased ?
                         cs.Value.Team != victimStats.Team :
                         cs.Value.Team != IW4Info.Team.Spectator)
                      .Where(cs => cs.Value.Team != IW4Info.Team.Spectator);

                 double victimLobbyRating = validVictimLobbyRatings.Count() > 0 ?
                     validVictimLobbyRatings.Average(cs => cs.Value.EloRating) :
                     victimStats.EloRating;*/
                #endregion

                double attackerEloDifference = Math.Log(Math.Max(1, victimStats.EloRating)) - Math.Log(Math.Max(1, attackerStats.EloRating));
                double winPercentage = 1.0 / (1 + Math.Pow(10, attackerEloDifference / Math.E));

                // double victimEloDifference = Math.Log(Math.Max(1, attackerStats.EloRating)) - Math.Log(Math.Max(1, victimStats.EloRating));
                // double lossPercentage = 1.0 / (1 + Math.Pow(10, victimEloDifference/ Math.E));

                attackerStats.EloRating += 6.0 * (1 - winPercentage);
                victimStats.EloRating -= 6.0 * (1 - winPercentage);

                attackerStats.EloRating = Math.Max(0, Math.Round(attackerStats.EloRating, 2));
                victimStats.EloRating = Math.Max(0, Math.Round(victimStats.EloRating, 2));
            }

            // update after calculation
            attackerStats.TimePlayed += (int)(DateTime.UtcNow - attackerStats.LastActive).TotalSeconds;
            victimStats.TimePlayed += (int)(DateTime.UtcNow - victimStats.LastActive).TotalSeconds;
            attackerStats.LastActive = DateTime.UtcNow;
            victimStats.LastActive = DateTime.UtcNow;
        }

        /// <summary>
        /// Update the client stats (skill etc)
        /// </summary>
        /// <param name="clientStats">Client statistics</param>
        /// <returns></returns>
        private EFClientStatistics UpdateStats(EFClientStatistics clientStats)
        {
            // prevent NaN or inactive time lowering SPM
            if ((DateTime.UtcNow - clientStats.LastStatCalculation).TotalSeconds / 60.0 < 0.01 ||
                (DateTime.UtcNow - clientStats.LastActive).TotalSeconds / 60.0 > 3 ||
                clientStats.SessionScore == 0)
            {
                // prevents idle time counting
                clientStats.LastStatCalculation = DateTime.UtcNow;
                return clientStats;
            }

            double timeSinceLastCalc = (DateTime.UtcNow - clientStats.LastStatCalculation).TotalSeconds / 60.0;
            double timeSinceLastActive = (DateTime.UtcNow - clientStats.LastActive).TotalSeconds / 60.0;

            int scoreDifference = 0;
            // this means they've been tking or suicide and is the only time they can have a negative SPM
            if (clientStats.RoundScore < 0)
            {
                scoreDifference = clientStats.RoundScore + clientStats.LastScore;
            }

            else if (clientStats.RoundScore > 0 && clientStats.LastScore < clientStats.RoundScore)
            {
                scoreDifference = clientStats.RoundScore - clientStats.LastScore;
            }

            double killSPM = scoreDifference / timeSinceLastCalc;
            double spmMultiplier = 2.934 * Math.Pow(_servers[clientStats.ServerId].TeamCount(clientStats.Team == IW4Info.Team.Allies ? IW4Info.Team.Axis : IW4Info.Team.Allies), -0.454);
            killSPM *= Math.Max(1, spmMultiplier);

            // update this for ac tracking
            clientStats.SessionSPM = killSPM;

            // calculate how much the KDR should weigh
            // 1.637 is a Eddie-Generated number that weights the KDR nicely
            double currentKDR = clientStats.SessionDeaths == 0 ? clientStats.SessionKills : clientStats.SessionKills / clientStats.SessionDeaths;
            double alpha = Math.Sqrt(2) / Math.Min(600, Math.Max(clientStats.Kills + clientStats.Deaths, 1));
            clientStats.RollingWeightedKDR = (alpha * currentKDR) + (1.0 - alpha) * clientStats.KDR;
            double KDRWeight = Math.Round(Math.Pow(clientStats.RollingWeightedKDR, 1.637 / Math.E), 3);

            // calculate the weight of the new play time against last 10 hours of gameplay
            int totalPlayTime = (clientStats.TimePlayed == 0) ?
                (int)(DateTime.UtcNow - clientStats.LastActive).TotalSeconds :
                clientStats.TimePlayed + (int)(DateTime.UtcNow - clientStats.LastActive).TotalSeconds;

            double SPMAgainstPlayWeight = timeSinceLastCalc / Math.Min(600, (totalPlayTime / 60.0));

            // calculate the new weight against average times the weight against play time
            clientStats.SPM = (killSPM * SPMAgainstPlayWeight) + (clientStats.SPM * (1 - SPMAgainstPlayWeight));

            if (clientStats.SPM < 0)
            {
                _log.WriteWarning("[StatManager:UpdateStats] clientStats SPM < 0");
                _log.WriteDebug($"{scoreDifference}-{clientStats.RoundScore} - {clientStats.LastScore} - {clientStats.SessionScore}");
                clientStats.SPM = 0;
            }

            clientStats.SPM = Math.Round(clientStats.SPM, 3);
            clientStats.Skill = Math.Round((clientStats.SPM * KDRWeight), 3);

            // fixme: how does this happen?
            if (double.IsNaN(clientStats.SPM) || double.IsNaN(clientStats.Skill))
            {
                _log.WriteWarning("[StatManager::UpdateStats] clientStats SPM/Skill NaN");
                _log.WriteDebug($"{killSPM}-{KDRWeight}-{totalPlayTime}-{SPMAgainstPlayWeight}-{clientStats.SPM}-{clientStats.Skill}-{scoreDifference}");
                clientStats.SPM = 0;
                clientStats.Skill = 0;
            }

            clientStats.LastStatCalculation = DateTime.UtcNow;
            //clientStats.LastScore = clientStats.SessionScore;

            return clientStats;
        }

        public EFServerStatistics InitializeServerStats(long serverId)
        {
            EFServerStatistics serverStats;

            using (var ctx = new DatabaseContext(disableTracking: true))
            {
                var serverStatsSet = ctx.Set<EFServerStatistics>();
                serverStats = serverStatsSet.FirstOrDefault(s => s.ServerId == serverId);

                if (serverStats == null)
                {
                    _log.WriteDebug($"Initializing server stats for {serverId}");
                    // server stats have never been generated before
                    serverStats = new EFServerStatistics()
                    {
                        ServerId = serverId,
                        TotalKills = 0,
                        TotalPlayTime = 0,
                    };

                    serverStats = serverStatsSet.Add(serverStats).Entity;
                    ctx.SaveChanges();
                }
            }

            return serverStats;
        }

        public void ResetKillstreaks(long serverId)
        {
            var serverStats = _servers[serverId];

            foreach (var stat in serverStats.PlayerStats.Values)
            {
                stat.StartNewSession();
            }
        }

        public void ResetStats(int clientId, long serverId)
        {
            var stats = _servers[serverId].PlayerStats[clientId];
            stats.Kills = 0;
            stats.Deaths = 0;
            stats.SPM = 0;
            stats.Skill = 0;
            stats.TimePlayed = 0;
            stats.EloRating = 200;
        }

        public async Task AddMessageAsync(int clientId, long serverId, string message)
        {
            // the web users can have no account
            if (clientId < 1)
            {
                return;
            }

            using (var ctx = new DatabaseContext(disableTracking: true))
            {
                ctx.Set<EFClientMessage>().Add(new EFClientMessage()
                {
                    ClientId = clientId,
                    Message = message,
                    ServerId = serverId,
                    TimeSent = DateTime.UtcNow
                });

                await ctx.SaveChangesAsync();
            }
        }

        public async Task Sync(Server sv)
        {
            long serverId = GetIdForServer(sv);

            using (var ctx = new DatabaseContext(disableTracking: true))
            {
                var serverSet = ctx.Set<EFServer>();
                serverSet.Update(_servers[serverId].Server);

                var serverStatsSet = ctx.Set<EFServerStatistics>();
                serverStatsSet.Update(_servers[serverId].ServerStatistics);

                await ctx.SaveChangesAsync();
            }
        }

        public void SetTeamBased(long serverId, bool isTeamBased)
        {
            _servers[serverId].IsTeamBased = isTeamBased;
        }

        public static long GetIdForServer(Server server)
        {
            if ($"{server.IP}:{server.Port.ToString()}" == "66.150.121.184:28965")
            {
                return 886229536;
            }

            long id = HashCode.Combine(server.IP, server.Port);
            id = id < 0 ? Math.Abs(id) : id;
            long? serverId;

            serverId = serverModels.FirstOrDefault(_server => _server.ServerId == server.EndPoint ||
                _server.EndPoint == server.ToString() ||
                _server.ServerId == id)?.ServerId;

            if (!serverId.HasValue)
            {
                return id;
            }

            return serverId.Value;
        }
    }
}