Update .gitignore to exclude TypeScript build info and add dist directory. Expand README with project overview, technology stack, prerequisites, and instructions for running and testing the application.

src/HSchool.Protocol/PacketReader.cs

@@ -0,0 +1,75 @@
+using System.Buffers.Binary;
+using System.Text;
+
+namespace HSchool.Protocol;
+
+/// <summary>Little-endian cursor over a received frame. Mirror of <see cref="PacketWriter"/>.</summary>
+public ref struct PacketReader(ReadOnlySpan<byte> buffer)
+{
+    private readonly ReadOnlySpan<byte> _buffer = buffer;
+    private int _position = 0;
+
+    public readonly int Position => _position;
+
+    public readonly int Remaining => _buffer.Length - _position;
+
+    public byte ReadByte()
+    {
+        EnsureAvailable(sizeof(byte));
+        var value = _buffer[_position];
+        _position += sizeof(byte);
+        return value;
+    }
+
+    public MessageType ReadMessageType() => (MessageType)ReadByte();
+
+    public ushort ReadUInt16()
+    {
+        EnsureAvailable(sizeof(ushort));
+        var value = BinaryPrimitives.ReadUInt16LittleEndian(_buffer[_position..]);
+        _position += sizeof(ushort);
+        return value;
+    }
+
+    public uint ReadUInt32()
+    {
+        EnsureAvailable(sizeof(uint));
+        var value = BinaryPrimitives.ReadUInt32LittleEndian(_buffer[_position..]);
+        _position += sizeof(uint);
+        return value;
+    }
+
+    public long ReadInt64()
+    {
+        EnsureAvailable(sizeof(long));
+        var value = BinaryPrimitives.ReadInt64LittleEndian(_buffer[_position..]);
+        _position += sizeof(long);
+        return value;
+    }
+
+    public float ReadSingle()
+    {
+        EnsureAvailable(sizeof(float));
+        var value = BinaryPrimitives.ReadSingleLittleEndian(_buffer[_position..]);
+        _position += sizeof(float);
+        return value;
+    }
+
+    public string ReadShortString()
+    {
+        var byteCount = ReadByte();
+        EnsureAvailable(byteCount);
+        var value = Encoding.UTF8.GetString(_buffer.Slice(_position, byteCount));
+        _position += byteCount;
+        return value;
+    }
+
+    private readonly void EnsureAvailable(int bytes)
+    {
+        if (_position + bytes > _buffer.Length)
+        {
+            throw new ProtocolException(
+                $"Truncated frame: need {bytes} bytes at offset {_position}, only {Remaining} available.");
+        }
+    }
+}