Port NBT impl from LibAC Dart

NBT/API/StringReader.cs

@@ -0,0 +1,196 @@
+using System;
+using System.Text;
+
+namespace LibAC.NBT.API
+{
+    public class StringReader
+    {
+        private readonly string _buffer;
+        private int _position = 0;
+        private int _lastPosition = 0;
+        private bool _quotedString = false;
+
+        public StringReader(string buffer)
+        {
+            _buffer = buffer;
+        }
+
+        // Check if there's more to read
+        public bool CanRead => _CanRead();
+
+        private bool _CanRead()
+        {
+            SkipWhitespace();
+            return _position < _buffer.Length;
+        }
+
+        // Get the number of chars seeked
+        public int Seeked => _lastPosition - _position;
+
+        // Read the next character
+        public char Next()
+        {
+            if (CanRead)
+            {
+                SkipWhitespace();
+                return _buffer[_position++];
+            }
+            else
+            {
+                throw new Exception("End of buffer reached");
+            }
+        }
+
+        // Generates a snapshot of the text location if applicable
+        public string GetSnapshot()
+        {
+            if (CanRead)
+            {
+                if (_position + 64 < _buffer.Length)
+                {
+                    return _buffer.Substring(_position, 64);
+                }
+                else
+                {
+                    return _buffer.Substring(_position);
+                }
+            }
+            else
+            {
+                return string.Empty;
+            }
+        }
+
+        // Peek the next character without advancing the position
+        public char Peek()
+        {
+            SkipWhitespace();
+            if (CanRead)
+            {
+                return _buffer[_position];
+            }
+            else
+            {
+                throw new Exception("End of buffer reached");
+            }
+        }
+
+        // Skip any whitespace characters
+        public void SkipWhitespace()
+        {
+            if (_quotedString) return; // We need whitespace for strings
+            while (_position < _buffer.Length && IsWhitespace(_buffer[_position]))
+            {
+                _position++;
+            }
+        }
+
+        // Check if a character is a whitespace
+        private bool IsWhitespace(char character)
+        {
+            return char.IsWhiteSpace(character);
+        }
+
+        // Read until a specific character is found
+        public string ReadUntil(char stopChar, int maxChars)
+        {
+            var result = new StringBuilder();
+            int index = 0;
+            while (CanRead && Peek() != stopChar && index < maxChars)
+            {
+                result.Append(Next().ToString());
+                index++;
+            }
+            return result.ToString();
+        }
+
+        // Read a string enclosed in double quotes
+        public string ReadQuotedString()
+        {
+            _quotedString = true;
+            if (Next() != '"')
+            {
+                throw new Exception("Expected double quotes at the start of a string");
+            }
+            var result = new StringBuilder();
+            while (CanRead)
+            {
+                char character = Next();
+                if (character == '"')
+                {
+                    break;
+                }
+                result.Append(character.ToString());
+            }
+            _quotedString = false;
+            return result.ToString();
+        }
+
+        // Read a number (int or double)
+        public string ReadNumber()
+        {
+            var result = new StringBuilder();
+            while (CanRead && (IsDigit(Peek()) || Peek() == '.' || Peek() == '-'))
+            {
+                result.Append(Next().ToString());
+            }
+            return result.ToString();
+        }
+
+        // Check if a character is a digit
+        private bool IsDigit(char character)
+        {
+            return char.IsDigit(character);
+        }
+
+        // Read an unquoted string (used for keys in SNBT)
+        public string ReadUnquotedString()
+        {
+            var result = new StringBuilder();
+            while (CanRead &&
+                   !IsWhitespace(Peek()) &&
+                   Peek() != ':' &&
+                   Peek() != ',' &&
+                   Peek() != '{' &&
+                   Peek() != '}' &&
+                   Peek() != '[' &&
+                   Peek() != ']')
+            {
+                result.Append(Next().ToString());
+            }
+            return result.ToString();
+        }
+
+        public string ReadString()
+        {
+            if (Peek() == '"')
+            {
+                return ReadQuotedString();
+            }
+            else
+            {
+                return ReadUnquotedString();
+            }
+        }
+
+        // Read a specific character and throw an exception if it's not found
+        public void Expect(char expectedChar)
+        {
+            if (char.ToLower(Next()) != char.ToLower(expectedChar))
+            {
+                throw new Exception($"Expected {expectedChar}");
+            }
+        }
+
+        public void StartSeek()
+        {
+            _lastPosition = _position;
+        }
+
+        public void EndSeek()
+        {
+            _position = _lastPosition;
+            _lastPosition = 0;
+        }
+    }
+}