using System;
using System.Reflection;
using System.Security.Cryptography;

namespace GostCryptography.Reflection
{
    static class CryptographyUtils
    {
        private static readonly object ObjToHashAlgorithmMethodSync = new object();
        private static volatile MethodInfo _objToHashAlgorithmMethod;

        public static HashAlgorithm ObjToHashAlgorithm(object hashAlg)
        {
            if (hashAlg == null)
            {
                throw ExceptionUtility.ArgumentNull(nameof(hashAlg));
            }

            HashAlgorithm hashAlgorithm = null;

            if (_objToHashAlgorithmMethod == null)
            {
                lock (ObjToHashAlgorithmMethodSync)
                {
                    if (_objToHashAlgorithmMethod == null)
                    {
                        var utilsType = Type.GetType("System.Security.Cryptography.Utils");

                        if (utilsType != null)
                        {
                            _objToHashAlgorithmMethod = utilsType.GetMethod("ObjToHashAlgorithm", BindingFlags.Static | BindingFlags.NonPublic, null, new[] { typeof(object) }, null);
                        }
                    }
                }
            }

            if (_objToHashAlgorithmMethod != null)
            {
                try
                {
                    hashAlgorithm = _objToHashAlgorithmMethod.Invoke(null, new[] { hashAlg }) as HashAlgorithm;
                }
                catch (TargetInvocationException exception)
                {
                    if (exception.InnerException != null)
                    {
                        throw exception.InnerException;
                    }

                    throw;
                }
            }

            return hashAlgorithm;
        }
    }
}