JoinQueue (#883)

* JoinQueue stalker port

* fix queues

---------

Co-authored-by: JerryImMouse <toperkas@gmail.com>

Content.Server/_CP14/JoinQueue/JoinQueueManager.cs

@@ -0,0 +1,173 @@
+using System.Linq;
+using Content.Server._CP14.Discord;
+using Content.Server.Connection;
+using Content.Shared._CP14.JoinQueue;
+using Content.Shared.CCVar;
+using Prometheus;
+using Robust.Server.Player;
+using Robust.Shared.Configuration;
+using Robust.Shared.Enums;
+using Robust.Shared.Network;
+using Robust.Shared.Player;
+using Robust.Shared.Timing;
+
+namespace Content.Server._CP14.JoinQueue;
+
+/// <summary>
+///     Manages new player connections when the server is full and queues them up, granting access when a slot becomes free
+/// </summary>
+public sealed class JoinQueueManager
+{
+    private static readonly Gauge QueueCount = Metrics.CreateGauge(
+        "join_queue_count",
+        "Amount of players in queue.");
+
+    private static readonly Counter QueueBypassCount = Metrics.CreateCounter(
+        "join_queue_bypass_count",
+        "Amount of players who bypassed queue by privileges.");
+
+    private static readonly Histogram QueueTimings = Metrics.CreateHistogram(
+        "join_queue_timings",
+        "Timings of players in queue",
+        new HistogramConfiguration()
+        {
+            LabelNames = new[] {"type"},
+            Buckets = Histogram.ExponentialBuckets(1, 2, 14),
+        });
+
+    [Dependency] private readonly IPlayerManager _playerManager = default!;
+    [Dependency] private readonly IConnectionManager _connectionManager = default!;
+    [Dependency] private readonly IConfigurationManager _cfg = default!;
+    [Dependency] private readonly IServerNetManager _netManager = default!;
+    [Dependency] private readonly DiscordAuthManager _discordAuthManager = default!;
+    //[Dependency] private readonly SponsorsManager _sponsors = default!;
+    private ISawmill _sawmill = default!;
+
+    /// <summary>
+    ///     Queue of active player sessions
+    /// </summary>
+    private readonly List<ICommonSession> _queue = new(); // Real Queue class can't delete disconnected users
+
+    private bool _isEnabled = false;
+
+    public int PlayerInQueueCount => _queue.Count;
+    public int ActualPlayersCount => _playerManager.PlayerCount - PlayerInQueueCount; // Now it's only real value with actual players count that in game
+
+    public void Initialize()
+    {
+        _netManager.RegisterNetMessage<MsgQueueUpdate>();
+
+        _cfg.OnValueChanged(CCVars.QueueEnabled, OnQueueCVarChanged, true);
+        _playerManager.PlayerStatusChanged += OnPlayerStatusChanged;
+        _discordAuthManager.PlayerVerified += OnPlayerVerified;
+        _sawmill = Logger.GetSawmill("queue");
+    }
+
+    private void OnQueueCVarChanged(bool value)
+    {
+        _isEnabled = value;
+
+        if (!value)
+        {
+            foreach (var session in _queue)
+            {
+                session.Channel.Disconnect("Queue was disabled");
+            }
+        }
+    }
+
+    private async void OnPlayerVerified(object? sender, ICommonSession session)
+    {
+        if (!_isEnabled)
+        {
+            SendToGame(session);
+            return;
+        }
+
+        var isPrivileged = await _connectionManager.HavePrivilegedJoin(session.UserId);
+        var currentOnline = _playerManager.PlayerCount - 1; // Do not count current session in general online, because we are still deciding her fate
+        var haveFreeSlot = currentOnline < _cfg.GetCVar(CCVars.SoftMaxPlayers);
+        if (isPrivileged || haveFreeSlot)
+        {
+            SendToGame(session);
+
+            if (isPrivileged && !haveFreeSlot)
+            {
+                QueueBypassCount.Inc();
+                _sawmill.Info($"{session.Name} bypassed soft slots by privileges");
+            }
+
+            return;
+        }
+
+        _queue.Add(session);
+        ProcessQueue(false, session.ConnectedTime);
+    }
+
+    private async void OnPlayerStatusChanged(object? sender, SessionStatusEventArgs e)
+    {
+        if (e.NewStatus == SessionStatus.Disconnected)
+        {
+            var wasInQueue = _queue.Remove(e.Session);
+
+            if (!wasInQueue && e.OldStatus != SessionStatus.InGame) // Process queue only if player disconnected from InGame or from queue
+                return;
+
+            ProcessQueue(true, e.Session.ConnectedTime);
+
+            if (wasInQueue)
+                QueueTimings.WithLabels("Unwaited").Observe((DateTime.UtcNow - e.Session.ConnectedTime).TotalSeconds);
+        }
+    }
+
+    /// <summary>
+    ///     If possible, takes the first player in the queue and sends him into the game
+    /// </summary>
+    /// <param name="isDisconnect">Is method called on disconnect event</param>
+    /// <param name="connectedTime">Session connected time for histogram metrics</param>
+    private void ProcessQueue(bool isDisconnect, DateTime connectedTime)
+    {
+        var players = ActualPlayersCount;
+        if (isDisconnect)
+            players--; // Decrease currently disconnected session but that has not yet been deleted
+
+        var haveFreeSlot = players < _cfg.GetCVar(CCVars.SoftMaxPlayers);
+        var queueContains = _queue.Count > 0;
+        if (haveFreeSlot && queueContains)
+        {
+            var session = _queue.First();
+            _queue.Remove(session);
+
+            SendToGame(session);
+
+            QueueTimings.WithLabels("Waited").Observe((DateTime.UtcNow - connectedTime).TotalSeconds);
+        }
+
+        SendUpdateMessages();
+        QueueCount.Set(_queue.Count);
+    }
+
+    /// <summary>
+    ///     Sends messages to all players in the queue with the current state of the queue
+    /// </summary>
+    private void SendUpdateMessages()
+    {
+        for (var i = 0; i < _queue.Count; i++)
+        {
+            _queue[i].Channel.SendMessage(new MsgQueueUpdate
+            {
+                Total = _queue.Count,
+                Position = i + 1,
+            });
+        }
+    }
+
+    /// <summary>
+    ///     Letting player's session into game, change player state
+    /// </summary>
+    /// <param name="s">Player session that will be sent to game</param>
+    private void SendToGame(ICommonSession s)
+    {
+        Timer.Spawn(0, () => _playerManager.JoinGame(s));
+    }
+}