using System;
using System.Text;

namespace ModelRenderer.Scripts.Common
{
    public class ByteToStringUtils
    {
        public static string UshortArrayToUnicodeString(ushort[] ushortArray)
        {
            if (ushortArray == null || ushortArray.Length == 0)
                return string.Empty;

            // Determine actual length up to the first null terminator
            int codeUnitCount = ushortArray.Length;
            for (int i = 0; i < ushortArray.Length; i++)
            {
                if (ushortArray[i] == 0)
                {
                    codeUnitCount = i;
                    break;
                }
            }

            if (codeUnitCount == 0)
                return string.Empty;

            // Convert ushort code units to a byte array (UTF-16LE expected)
            byte[] byteArray = new byte[codeUnitCount * 2];
            Buffer.BlockCopy(ushortArray, 0, byteArray, 0, byteArray.Length);

            // Convert bytes to string using Unicode (UTF-16LE)
            try
            {
                return Encoding.Unicode.GetString(byteArray);
            }
            catch (Exception ex)
            {
                UnityEngine.Debug.LogError($"Error converting bytes to Unicode string: {ex.Message}");
                return string.Empty;
            }
        }

        public static string UshortArrayToCP936String(ushort[] ushortArray)
        {
            if (ushortArray == null || ushortArray.Length == 0)
                return string.Empty;
    
            // First convert ushort array to byte array
            // Each ushort (16 bits) can be up to two bytes in GBK
            byte[] byteArray = new byte[ushortArray.Length * 2];
            
            Buffer.BlockCopy(ushortArray, 0, byteArray, 0, byteArray.Length);

            return ByteArrayToCP936String(byteArray);
        }
        
        public static string ByteArrayToCP936String(byte[] byteArray)
        {
            if (byteArray == null || byteArray.Length == 0)
                return string.Empty;

            try
            {
                // Code page 936 is the code page for Simplified Chinese (GB2312/GBK)
                // You may need to import System.Text.Encoding.CodePages package for Unity/modern .NET
                Encoding cp936Encoding = Encoding.GetEncoding(936);

                // Trim at first null terminator, if present
                int length = byteArray.Length;
                for (int i = 0; i < byteArray.Length; i++)
                {
                    if (byteArray[i] == 0)
                    {
                        length = i;
                        break;
                    }
                }

                if (length <= 0)
                    return string.Empty;

                // Convert the byte array to a string using code page 936 encoding
                return cp936Encoding.GetString(byteArray, 0, length);
            }
            catch (Exception ex)
            {
                UnityEngine.Debug.LogError($"Error converting bytes to CP936 string: {ex.Message}");
                return string.Empty;
            }
        }

        public static string ByteArrayToUnicodeString(byte[] byteArray)
        {
            if (byteArray == null || byteArray.Length == 0)
                return string.Empty;

            // Trim at first null terminator (two-byte aligned not guaranteed; treat any 0 byte as terminator)
            int length = byteArray.Length;
            for (int i = 0; i < byteArray.Length; i++)
            {
                if (byteArray[i] == 0)
                {
                    length = i;
                    break;
                }
            }

            if (length <= 0)
                return string.Empty;

            return Encoding.Unicode.GetString(byteArray, 0, length);
        }

        public static string ByteArrayToUTF8String(byte[] byteArray)
        {
            if (byteArray == null || byteArray.Length == 0)
                return string.Empty;

            // Trim at first null terminator
            int length = byteArray.Length;
            for (int i = 0; i < byteArray.Length; i++)
            {
                if (byteArray[i] == 0)
                {
                    length = i;
                    break;
                }
            }

            if (length <= 0)
                return string.Empty;

            try
            {
                return Encoding.UTF8.GetString(byteArray, 0, length);
            }
            catch (Exception ex)
            {
                UnityEngine.Debug.LogError($"Error converting bytes to UTF-8 string: {ex.Message}");
                return string.Empty;
            }
        }
    }
}