fix: Adds packet logging (#836)

### Enabling Packet Logging
`[packetlogging on` and target the user.
Supports command modifiers such as:
`[online packetlogging on where accesslevel = player`

Logs are saved in `path/<ip address>/packets.log`. It is a simple append-format log with no date splitting.

Projects/Server/Network/NetState/NetState.cs

@@ -73,6 +73,7 @@ namespace Server.Network
         internal ParserState _parserState = ParserState.AwaitingNextPacket;
         internal ProtocolState _protocolState = ProtocolState.AwaitingSeed;
         internal GCHandle _handle;
+        private bool _packetLogging;
 
         internal enum ParserState
         {
@@ -97,6 +98,13 @@ namespace Server.Network
             Error
         }
 
+        private static string _packetLoggingPath;
+
+        public static void Configure()
+        {
+            _packetLoggingPath = ServerConfiguration.GetSetting("netstate.packetLoggingPath", Path.Combine(Core.BaseDirectory, "Packets"));
+        }
+
         public static void Initialize()
         {
             Timer.DelayCall(TimeSpan.FromMinutes(1), TimeSpan.FromMinutes(1.5), CheckAllAlive);
@@ -142,6 +150,21 @@ namespace Server.Network
             CreatedCallback?.Invoke(this);
         }
 
+        // Only use this for debugging. This will make your server very slow!
+        public bool PacketLogging
+        {
+            get => _packetLogging;
+            set
+            {
+                _packetLogging = value;
+
+                if (_packetLogging)
+                {
+                    StartPacketLog();
+                }
+            }
+        }
+
         public DateTime ConnectedOn { get; }
 
         public TimeSpan ConnectedFor => Core.Now - ConnectedOn;
@@ -486,6 +509,11 @@ namespace Server.Network
                     buffer.CopyFrom(span);
                 }
 
+                if (PacketLogging)
+                {
+                    LogPacket(span, ReadOnlySpan<byte>.Empty, span.Length, false);
+                }
+
                 SendPipe.Writer.Advance((uint)length);
 
                 if (!_flushQueued)
@@ -506,6 +534,48 @@ namespace Server.Network
             }
         }
 
+        private void StartPacketLog()
+        {
+            try
+            {
+                var logDir = Path.Combine(_packetLoggingPath, _toString);
+                PathUtility.EnsureDirectory(logDir);
+                var logPath = Path.Combine(logDir, "packets.log");
+                using var op = new StreamWriter(logPath, true);
+
+                op.WriteLine(">>>>>>>>>> Logging started {0:yyyy/MM/dd HH:mm::ss} <<<<<<<<<<", Core.Now);
+                op.WriteLine();
+                op.WriteLine();
+            }
+            catch (Exception e)
+            {
+                Console.WriteLine(e);
+            }
+        }
+
+        private void LogPacket(ReadOnlySpan<byte> first, ReadOnlySpan<byte> second, int totalLength, bool incoming)
+        {
+            try
+            {
+                var logDir = Path.Combine(_packetLoggingPath, _toString);
+                PathUtility.EnsureDirectory(logDir);
+                var logPath = Path.Combine(logDir, "packets.log");
+
+                const string incomingStr = "Client -> Server";
+                const string outgoingStr = "Server -> Client";
+
+                using var sw = new StreamWriter(logPath, true);
+                sw.WriteLine($"{Core.Now:HH:mm:ss.ffff}: {(incoming ? incomingStr : outgoingStr)} 0x{first[0]:X2} (Length: {totalLength})");
+                sw.FormatBuffer(first, second, totalLength);
+                sw.WriteLine();
+                sw.WriteLine();
+            }
+            catch
+            {
+                // ignored
+            }
+        }
+
         public void HandleReceive()
         {
             if (!_running)
@@ -760,6 +830,11 @@ namespace Server.Network
 
             UpdatePacketCount(packetId);
 
+            if (PacketLogging)
+            {
+                LogPacket(packetReader.First, packetReader.Second, packetLength, true);
+            }
+
             handler.OnReceive(this, packetReader, ref packetLength);
 
             prof?.Finish(packetLength);