using System;

using Org.BouncyCastle.Crypto.Modes;
using Org.BouncyCastle.Crypto.Parameters;

namespace Org.BouncyCastle.Crypto
{
	/**
	* The AEAD block ciphers already handle buffering internally, so this class
	* just takes care of implementing IBufferedCipher methods.
	*/
	public class BufferedAeadBlockCipher
		: BufferedCipherBase
	{
		private readonly IAeadBlockCipher cipher;

		public BufferedAeadBlockCipher(
			IAeadBlockCipher cipher)
		{
			if (cipher == null)
				throw new ArgumentNullException("cipher");

			this.cipher = cipher;
		}

		public override string AlgorithmName
		{
			get { return cipher.AlgorithmName; }
		}

		/**
		* initialise the cipher.
		*
		* @param forEncryption if true the cipher is initialised for
		*  encryption, if false for decryption.
		* @param param the key and other data required by the cipher.
		* @exception ArgumentException if the parameters argument is
		* inappropriate.
		*/
		public override void Init(
			bool				forEncryption,
			ICipherParameters	parameters)
		{
			if (parameters is ParametersWithRandom)
			{
				parameters = ((ParametersWithRandom) parameters).Parameters;
			}

			cipher.Init(forEncryption, parameters);
		}

		/**
		* return the blocksize for the underlying cipher.
		*
		* @return the blocksize for the underlying cipher.
		*/
		public override int GetBlockSize()
		{
			return cipher.GetBlockSize();
		}

		/**
		* return the size of the output buffer required for an update
		* an input of len bytes.
		*
		* @param len the length of the input.
		* @return the space required to accommodate a call to update
		* with len bytes of input.
		*/
		public override int GetUpdateOutputSize(
			int length)
		{
			return cipher.GetUpdateOutputSize(length);
		}

		/**
		* return the size of the output buffer required for an update plus a
		* doFinal with an input of len bytes.
		*
		* @param len the length of the input.
		* @return the space required to accommodate a call to update and doFinal
		* with len bytes of input.
		*/
		public override int GetOutputSize(
			int length)
		{
			return cipher.GetOutputSize(length);
		}

		/**
		* process a single byte, producing an output block if neccessary.
		*
		* @param in the input byte.
		* @param out the space for any output that might be produced.
		* @param outOff the offset from which the output will be copied.
		* @return the number of output bytes copied to out.
		* @exception DataLengthException if there isn't enough space in out.
		* @exception InvalidOperationException if the cipher isn't initialised.
		*/
		public override int ProcessByte(
			byte	input,
			byte[]	output,
			int		outOff)
		{
			return cipher.ProcessByte(input, output, outOff);
		}

		public override byte[] ProcessByte(
			byte input)
		{
			int outLength = GetUpdateOutputSize(1);

			byte[] outBytes = outLength > 0 ? new byte[outLength] : null;

			int pos = ProcessByte(input, outBytes, 0);

			if (outLength > 0 && pos < outLength)
			{
				byte[] tmp = new byte[pos];
				Array.Copy(outBytes, 0, tmp, 0, pos);
				outBytes = tmp;
			}

			return outBytes;
		}

		public override byte[] ProcessBytes(
			byte[]	input,
			int		inOff,
			int		length)
		{
			if (input == null)
				throw new ArgumentNullException("input");
			if (length < 1)
				return null;

			int outLength = GetUpdateOutputSize(length);

			byte[] outBytes = outLength > 0 ? new byte[outLength] : null;

			int pos = ProcessBytes(input, inOff, length, outBytes, 0);

			if (outLength > 0 && pos < outLength)
			{
				byte[] tmp = new byte[pos];
				Array.Copy(outBytes, 0, tmp, 0, pos);
				outBytes = tmp;
			}

			return outBytes;
		}

		/**
		* process an array of bytes, producing output if necessary.
		*
		* @param in the input byte array.
		* @param inOff the offset at which the input data starts.
		* @param len the number of bytes to be copied out of the input array.
		* @param out the space for any output that might be produced.
		* @param outOff the offset from which the output will be copied.
		* @return the number of output bytes copied to out.
		* @exception DataLengthException if there isn't enough space in out.
		* @exception InvalidOperationException if the cipher isn't initialised.
		*/
		public override int ProcessBytes(
			byte[]	input,
			int		inOff,
			int		length,
			byte[]	output,
			int		outOff)
		{
			return cipher.ProcessBytes(input, inOff, length, output, outOff);
		}

		public override byte[] DoFinal()
		{
			byte[] outBytes = EmptyBuffer;

			int length = GetOutputSize(0);
			if (length > 0)
			{
				outBytes = new byte[length];

				int pos = DoFinal(outBytes, 0);
				if (pos < outBytes.Length)
				{
					byte[] tmp = new byte[pos];
					Array.Copy(outBytes, 0, tmp, 0, pos);
					outBytes = tmp;
				}
			}

			return outBytes;
		}

		public override byte[] DoFinal(
			byte[]	input,
			int		inOff,
			int		inLen)
		{
			if (input == null)
				throw new ArgumentNullException("input");

			int length = GetOutputSize(inLen);

			byte[] outBytes = EmptyBuffer;

			if (length > 0)
			{
				outBytes = new byte[length];

				int pos = (inLen > 0)
					?	ProcessBytes(input, inOff, inLen, outBytes, 0)
					:	0;

				pos += DoFinal(outBytes, pos);

				if (pos < outBytes.Length)
				{
					byte[] tmp = new byte[pos];
					Array.Copy(outBytes, 0, tmp, 0, pos);
					outBytes = tmp;
				}
			}

			return outBytes;
		}

		/**
		* Process the last block in the buffer.
		*
		* @param out the array the block currently being held is copied into.
		* @param outOff the offset at which the copying starts.
		* @return the number of output bytes copied to out.
		* @exception DataLengthException if there is insufficient space in out for
		* the output, or the input is not block size aligned and should be.
		* @exception InvalidOperationException if the underlying cipher is not
		* initialised.
		* @exception InvalidCipherTextException if padding is expected and not found.
		* @exception DataLengthException if the input is not block size
		* aligned.
		*/
		public override int DoFinal(
			byte[]	output,
			int		outOff)
		{
			return cipher.DoFinal(output, outOff);
		}

		/**
		* Reset the buffer and cipher. After resetting the object is in the same
		* state as it was after the last init (if there was one).
		*/
		public override void Reset()
		{
			cipher.Reset();
		}
	}
}
