using System;
using System.Runtime.InteropServices;
using System.Security.Cryptography;
using System.Text;

namespace SHARP
{
    internal class AesGcm
    {
      public byte[] Decrypt(byte[] key, byte[] iv, byte[] aad, byte[] cipherText, byte[] authTag)
      {
        IntPtr num1 = this.OpenAlgorithmProvider(BCrypt.BCRYPT_AES_ALGORITHM, BCrypt.MS_PRIMITIVE_PROVIDER, BCrypt.BCRYPT_CHAIN_MODE_GCM);
        IntPtr hKey;
        IntPtr hglobal = this.ImportKey(num1, key, out hKey);
        BCrypt.BCRYPT_AUTHENTICATED_CIPHER_MODE_INFO pPaddingInfo = new BCrypt.BCRYPT_AUTHENTICATED_CIPHER_MODE_INFO(iv, aad, authTag);
        byte[] pbOutput;
        using (pPaddingInfo)
        {
          byte[] pbIV = new byte[this.MaxAuthTagSize(num1)];
          int pcbResult = 0;
          uint num2 = BCrypt.BCryptDecrypt(hKey, cipherText, cipherText.Length, ref pPaddingInfo, pbIV, pbIV.Length, (byte[]) null, 0, ref pcbResult, 0);
          if (num2 != 0U)
            throw new CryptographicException($"BCrypt.BCryptDecrypt() (get size) failed with status code: {num2}");
          pbOutput = new byte[pcbResult];
          uint num3 = BCrypt.BCryptDecrypt(hKey, cipherText, cipherText.Length, ref pPaddingInfo, pbIV, pbIV.Length, pbOutput, pbOutput.Length, ref pcbResult, 0);
          if ((int) num3 == (int) BCrypt.STATUS_AUTH_TAG_MISMATCH)
            throw new CryptographicException("BCrypt.BCryptDecrypt(): authentication tag mismatch");
          if (num3 != 0U)
            throw new CryptographicException($"BCrypt.BCryptDecrypt() failed with status code:{num3}");
        }
        int num4 = (int) BCrypt.BCryptDestroyKey(hKey);
        Marshal.FreeHGlobal(hglobal);
        int num5 = (int) BCrypt.BCryptCloseAlgorithmProvider(num1, 0U);
        return pbOutput;
      }

      private int MaxAuthTagSize(IntPtr hAlg)
      {
        byte[] property = this.GetProperty(hAlg, BCrypt.BCRYPT_AUTH_TAG_LENGTH);
        return BitConverter.ToInt32(new byte[4]
        {
          property[4],
          property[5],
          property[6],
          property[7]
        }, 0);
      }

      private IntPtr OpenAlgorithmProvider(string alg, string provider, string chainingMode)
      {
        IntPtr phAlgorithm = IntPtr.Zero;
        uint num1 = BCrypt.BCryptOpenAlgorithmProvider(out phAlgorithm, alg, provider, 0U);
        if (num1 != 0U)
          throw new CryptographicException($"BCrypt.BCryptOpenAlgorithmProvider() failed with status code:{num1}");
        byte[] bytes = Encoding.Unicode.GetBytes(chainingMode);
        uint num2 = BCrypt.BCryptSetAlgorithmProperty(phAlgorithm, BCrypt.BCRYPT_CHAINING_MODE, bytes, bytes.Length, 0);
        if (num2 != 0U)
          throw new CryptographicException($"BCrypt.BCryptSetAlgorithmProperty(BCrypt.BCRYPT_CHAINING_MODE, BCrypt.BCRYPT_CHAIN_MODE_GCM) failed with status code:{num2}");
        return phAlgorithm;
      }

      private IntPtr ImportKey(IntPtr hAlg, byte[] key, out IntPtr hKey)
      {
        int int32 = BitConverter.ToInt32(this.GetProperty(hAlg, BCrypt.BCRYPT_OBJECT_LENGTH), 0);
        IntPtr pbKeyObject = Marshal.AllocHGlobal(int32);
        byte[] pbInput = this.Concat(BCrypt.BCRYPT_KEY_DATA_BLOB_MAGIC, BitConverter.GetBytes(1), BitConverter.GetBytes(key.Length), key);
        uint num = BCrypt.BCryptImportKey(hAlg, IntPtr.Zero, BCrypt.BCRYPT_KEY_DATA_BLOB, out hKey, pbKeyObject, int32, pbInput, pbInput.Length, 0U);
        if (num != 0U)
          throw new CryptographicException($"BCrypt.BCryptImportKey() failed with status code:{num}");
        return pbKeyObject;
      }

      private byte[] GetProperty(IntPtr hAlg, string name)
      {
        int pcbResult = 0;
        uint property1 = BCrypt.BCryptGetProperty(hAlg, name, (byte[]) null, 0, ref pcbResult, 0U);
        if (property1 != 0U)
          throw new CryptographicException($"BCrypt.BCryptGetProperty() (get size) failed with status code:{property1}");
        byte[] pbOutput = new byte[pcbResult];
        uint property2 = BCrypt.BCryptGetProperty(hAlg, name, pbOutput, pbOutput.Length, ref pcbResult, 0U);
        if (property2 != 0U)
          throw new CryptographicException($"BCrypt.BCryptGetProperty() failed with status code:{property2}");
        return pbOutput;
      }

      public byte[] Concat(params byte[][] arrays)
      {
        int num = 0;
        foreach (byte[] array in arrays)
        {
          if (array != null)
            num += array.Length;
        }
        byte[] dst = new byte[num - 1 + 1];
        int dstOffset = 0;
        foreach (byte[] array in arrays)
        {
          if (array != null)
          {
            Buffer.BlockCopy((Array) array, 0, (Array) dst, dstOffset, array.Length);
            dstOffset += array.Length;
          }
        }
        return dst;
      }
    }
}