using System;
using Org.BouncyCastle.Crypto.Digests;
using Org.BouncyCastle.Crypto.Macs;
using Org.BouncyCastle.Crypto.Parameters;

namespace ModernKeePassLib.Cryptography.Hash
{
    public class HMACSHA256: IDisposable
    {
        private readonly HMac _hmac;

        public byte[] Hash
        {
            get
            {
                byte[] resBuf = new byte[_hmac.GetMacSize()];
                _hmac.DoFinal(resBuf, 0);
                return resBuf;
            }
        }

        public HMACSHA256(byte[] key)
        {
            _hmac = new HMac(new Sha256Digest());
            _hmac.Init(new KeyParameter(key));
        }

        public byte[] ComputeHash(byte[] value)
        {
            if (value == null) throw new ArgumentNullException(nameof(value));

            byte[] resBuf = new byte[_hmac.GetMacSize()];
            _hmac.BlockUpdate(value, 0, value.Length);
            _hmac.DoFinal(resBuf, 0);

            return resBuf;
        }

        public void Dispose()
        {
            _hmac.Reset();
        }

        internal void TransformBlock(byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset        )
        {
            _hmac.BlockUpdate(inputBuffer, inputOffset, inputCount);
        }

        internal void TransformFinalBlock(byte[] inputBuffer, int inputOffset, int inputCount)
        {
            _hmac.DoFinal(inputBuffer, inputOffset);
        }

        internal void Initialize()
        {
            _hmac.Reset();
        }
    }
}