using System;

namespace Org.BouncyCastle.Crypto.Tls
{
    internal class DtlsEpoch
    {
        private readonly DtlsReplayWindow mReplayWindow = new DtlsReplayWindow();

        private readonly int mEpoch;
        private readonly TlsCipher mCipher;

        private long mSequenceNumber = 0;

        internal DtlsEpoch(int epoch, TlsCipher cipher)
        {
            if (epoch < 0)
                throw new ArgumentException("must be >= 0", "epoch");
            if (cipher == null)
                throw new ArgumentNullException("cipher");

            this.mEpoch = epoch;
            this.mCipher = cipher;
        }

        internal long AllocateSequenceNumber()
        {
            lock (this)
            {
                if (mSequenceNumber >= (1L << 48))
                    throw new TlsFatalAlert(AlertDescription.internal_error);

                return mSequenceNumber++;
            }
        }

        internal TlsCipher Cipher
        {
            get { return mCipher; }
        }

        internal int Epoch
        {
            get { return mEpoch; }
        }

        internal DtlsReplayWindow ReplayWindow
        {
            get { return mReplayWindow; }
        }

        internal long SequenceNumber
        {
            get { lock(this) return mSequenceNumber; }
        }
    }
}