geutebruck/GeViSetEditor/GeViSetEditor.Core/Parsers/InPlaceConfigModifier.cs

using System;
using System.Text;
using GeViSetEditor.Core.Models;

namespace GeViSetEditor.Core.Parsers
{
    /// <summary>
    /// Modifies configuration in-place to preserve binary structure
    /// Safer approach for edit operations
    /// </summary>
    public class InPlaceConfigModifier
    {
        /// <summary>
        /// Modify a node's value in the original data array
        /// Only works for fixed-size types (boolean, integer)
        /// </summary>
        public bool ModifyNode(byte[] data, ConfigNode node, object newValue)
        {
            if (node == null || data == null)
                return false;

            switch (node.NodeType)
            {
                case "boolean":
                    return ModifyBoolean(data, node, newValue);

                case "integer":
                    return ModifyInteger(data, node, newValue);

                case "string":
                    // Strings are variable length - can only modify if same length
                    return ModifyString(data, node, newValue);

                default:
                    return false;
            }
        }

        private bool ModifyBoolean(byte[] data, ConfigNode node, object newValue)
        {
            try
            {
                // Boolean structure: 01 <value>
                // Value is at StartOffset + 1
                int valueOffset = node.StartOffset + 1;

                if (valueOffset >= data.Length)
                    return false;

                bool boolValue = Convert.ToBoolean(newValue);
                data[valueOffset] = boolValue ? (byte)1 : (byte)0;

                // Update node value
                node.Value = boolValue;
                return true;
            }
            catch
            {
                return false;
            }
        }

        private bool ModifyInteger(byte[] data, ConfigNode node, object newValue)
        {
            try
            {
                // Integer structure: 04 <int32_LE>
                // Value is at StartOffset + 1
                int valueOffset = node.StartOffset + 1;

                if (valueOffset + 4 > data.Length)
                    return false;

                int intValue = Convert.ToInt32(newValue);
                byte[] bytes = BitConverter.GetBytes(intValue);

                Array.Copy(bytes, 0, data, valueOffset, 4);

                // Update node value
                node.Value = intValue;
                return true;
            }
            catch
            {
                return false;
            }
        }

        private bool ModifyString(byte[] data, ConfigNode node, object newValue)
        {
            try
            {
                // String structure: 07 <len> <data>
                // Original length at StartOffset + 1
                int lengthOffset = node.StartOffset + 1;

                if (lengthOffset >= data.Length)
                    return false;

                byte originalLength = data[lengthOffset];
                string newString = newValue?.ToString() ?? "";
                byte[] newBytes = Encoding.UTF8.GetBytes(newString);

                // Can only modify if new string has same length
                if (newBytes.Length != originalLength)
                {
                    Console.WriteLine($"  ⚠ Cannot modify string: length mismatch (original={originalLength}, new={newBytes.Length})");
                    return false;
                }

                // Copy new string data
                int dataOffset = lengthOffset + 1;
                Array.Copy(newBytes, 0, data, dataOffset, newBytes.Length);

                // Update node value
                node.Value = newString;
                return true;
            }
            catch
            {
                return false;
            }
        }

        /// <summary>
        /// Check if a node can be modified in-place
        /// </summary>
        public bool CanModify(ConfigNode node, object newValue)
        {
            if (node == null)
                return false;

            switch (node.NodeType)
            {
                case "boolean":
                case "integer":
                    return true;

                case "string":
                    // String can only be modified if same length
                    string currentStr = node.Value?.ToString() ?? "";
                    string newStr = newValue?.ToString() ?? "";
                    return Encoding.UTF8.GetByteCount(currentStr) == Encoding.UTF8.GetByteCount(newStr);

                default:
                    return false;
            }
        }
    }
}