using System;
using System.IO;
using System.Text;

namespace Raksha.Bcpg.Sig
{
	/**
	* Class provided a NotationData object according to
	* RFC2440, Chapter 5.2.3.15. Notation Data
	*/
	public class NotationData
		: SignatureSubpacket
	{
		public const int HeaderFlagLength = 4;
		public const int HeaderNameLength = 2;
		public const int HeaderValueLength = 2;

		public NotationData(
			bool	critical,
			byte[]	data)
			: base(SignatureSubpacketTag.NotationData, critical, data)
		{
		}

		public NotationData(
			bool	critical,
			bool	humanReadable,
			string	notationName,
			string	notationValue)
			: base(SignatureSubpacketTag.NotationData, critical,
				createData(humanReadable, notationName, notationValue))
		{
		}

		private static byte[] createData(
			bool	humanReadable,
			string	notationName,
			string	notationValue)
		{
			MemoryStream os = new MemoryStream();

			// (4 octets of flags, 2 octets of name length (M),
			// 2 octets of value length (N),
			// M octets of name data,
			// N octets of value data)

			// flags
			os.WriteByte(humanReadable ? (byte)0x80 : (byte)0x00);
			os.WriteByte(0x0);
			os.WriteByte(0x0);
			os.WriteByte(0x0);

			byte[] nameData, valueData = null;
			int nameLength, valueLength;

			nameData = Encoding.UTF8.GetBytes(notationName);
			nameLength = System.Math.Min(nameData.Length, 0xFF);

			valueData = Encoding.UTF8.GetBytes(notationValue);
			valueLength = System.Math.Min(valueData.Length, 0xFF);

			// name length
			os.WriteByte((byte)(nameLength >> 8));
			os.WriteByte((byte)(nameLength >> 0));

			// value length
			os.WriteByte((byte)(valueLength >> 8));
			os.WriteByte((byte)(valueLength >> 0));

			// name
			os.Write(nameData, 0, nameLength);

			// value
			os.Write(valueData, 0, valueLength);

			return os.ToArray();
		}

		public bool IsHumanReadable
		{
			get { return data[0] == (byte)0x80; }
		}

		public string GetNotationName()
		{
			int nameLength = ((data[HeaderFlagLength] << 8) + (data[HeaderFlagLength + 1] << 0));
			int namePos = HeaderFlagLength + HeaderNameLength + HeaderValueLength;

			return Encoding.UTF8.GetString(data, namePos, nameLength);
		}

		public string GetNotationValue()
		{
			int nameLength = ((data[HeaderFlagLength] << 8) + (data[HeaderFlagLength + 1] << 0));
			int valueLength = ((data[HeaderFlagLength + HeaderNameLength] << 8) + (data[HeaderFlagLength + HeaderNameLength + 1] << 0));
			int valuePos = HeaderFlagLength + HeaderNameLength + HeaderValueLength + nameLength;

			return Encoding.UTF8.GetString(data, valuePos, valueLength);
		}

		public byte[] GetNotationValueBytes()
		{
			int nameLength = ((data[HeaderFlagLength] << 8) + (data[HeaderFlagLength + 1] << 0));
			int valueLength = ((data[HeaderFlagLength + HeaderNameLength] << 8) + (data[HeaderFlagLength + HeaderNameLength + 1] << 0));
			int valuePos = HeaderFlagLength + HeaderNameLength + HeaderValueLength + nameLength;

			byte[] bytes = new byte[valueLength];
			Array.Copy(data, valuePos, bytes, 0, valueLength);
			return bytes;
		}
	}
}
