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

using Org.BouncyCastle.Math;

namespace Org.BouncyCastle.Asn1
{
    public class DerObjectIdentifier
        : Asn1Object
    {
		private static readonly Regex OidRegex = new Regex(@"\A[0-2](\.[0-9]+)+\z");

		private readonly string identifier;

		/**
         * return an Oid from the passed in object
         *
         * @exception ArgumentException if the object cannot be converted.
         */
        public static DerObjectIdentifier GetInstance(
            object obj)
        {
            if (obj == null || obj is DerObjectIdentifier)
            {
                return (DerObjectIdentifier) obj;
            }

			throw new ArgumentException("illegal object in GetInstance: " + obj.GetType().Name, "obj");
        }

		/**
         * return an object Identifier from a tagged object.
         *
         * @param obj the tagged object holding the object we want
         * @param explicitly true if the object is meant to be explicitly
         *              tagged false otherwise.
         * @exception ArgumentException if the tagged object cannot
         *               be converted.
         */
        public static DerObjectIdentifier GetInstance(
            Asn1TaggedObject	obj,
            bool				explicitly)
        {
            return GetInstance(obj.GetObject());
        }

		public DerObjectIdentifier(
            string identifier)
        {
			if (identifier == null)
				throw new ArgumentNullException("identifier");
			if (!OidRegex.IsMatch(identifier))
				throw new FormatException("string " + identifier + " not an OID");

			this.identifier = identifier;
        }

		// TODO Change to ID?
		public string Id
        {
            get { return identifier; }
        }

		public virtual DerObjectIdentifier Branch(string branchID)
		{
			return new DerObjectIdentifier(identifier + "." + branchID);
		}

        /**
         * Return  true if this oid is an extension of the passed in branch, stem.
         * @param stem the arc or branch that is a possible parent.
         * @return  true if the branch is on the passed in stem, false otherwise.
         */
        public virtual bool On(DerObjectIdentifier stem)
        {
            string id = Id, stemId = stem.Id;
            return id.Length > stemId.Length && id[stemId.Length] == '.' && id.StartsWith(stemId);
        }

        internal DerObjectIdentifier(
            byte[] bytes)
            : this(MakeOidStringFromBytes(bytes))
        {
        }

		private void WriteField(
            Stream	outputStream,
            long	fieldValue)
        {
			byte[] result = new byte[9];
			int pos = 8;
			result[pos] = (byte)(fieldValue & 0x7f);
			while (fieldValue >= (1L << 7))
			{
				fieldValue >>= 7;
				result[--pos] = (byte)((fieldValue & 0x7f) | 0x80);
			}
			outputStream.Write(result, pos, 9 - pos);
        }

		private void WriteField(
			Stream		outputStream,
			BigInteger	fieldValue)
		{
			int byteCount = (fieldValue.BitLength + 6) / 7;
			if (byteCount == 0)
			{
				outputStream.WriteByte(0);
			}
			else
			{
				BigInteger tmpValue = fieldValue;
				byte[] tmp = new byte[byteCount];
				for (int i = byteCount-1; i >= 0; i--)
				{
					tmp[i] = (byte) ((tmpValue.IntValue & 0x7f) | 0x80);
					tmpValue = tmpValue.ShiftRight(7);
				}
				tmp[byteCount-1] &= 0x7f;
				outputStream.Write(tmp, 0, tmp.Length);
			}
		}

        internal override void Encode(
            DerOutputStream derOut)
        {
            OidTokenizer tok = new OidTokenizer(identifier);
            MemoryStream bOut = new MemoryStream();
            DerOutputStream dOut = new DerOutputStream(bOut);

			string token = tok.NextToken();
            int first = int.Parse(token);

			token = tok.NextToken();
            int second = int.Parse(token);

            WriteField(bOut, first * 40 + second);

            while (tok.HasMoreTokens)
            {
				token = tok.NextToken();
				if (token.Length < 18)
				{
					WriteField(bOut, Int64.Parse(token));
				}
				else
				{
					WriteField(bOut, new BigInteger(token));
				}
			}

            dOut.Dispose();

			derOut.WriteEncoded(Asn1Tags.ObjectIdentifier, bOut.ToArray());
        }

		protected override int Asn1GetHashCode()
		{
            return identifier.GetHashCode();
        }

		protected override bool Asn1Equals(
			Asn1Object asn1Object)
		{
			DerObjectIdentifier other = asn1Object as DerObjectIdentifier;

			if (other == null)
				return false;

			return this.identifier.Equals(other.identifier);
        }

		public override string ToString()
		{
			return identifier;
		}

		private static string MakeOidStringFromBytes(
			byte[] bytes)
		{
			StringBuilder	objId = new StringBuilder();
			long			value = 0;
			BigInteger		bigValue = null;
			bool			first = true;

			for (int i = 0; i != bytes.Length; i++)
			{
				int b = bytes[i];

				if (value < 0x80000000000000L)
				{
					value = value * 128 + (b & 0x7f);
					if ((b & 0x80) == 0)             // end of number reached
					{
						if (first)
						{
							switch ((int)value / 40)
							{
								case 0:
									objId.Append('0');
									break;
								case 1:
									objId.Append('1');
									value -= 40;
									break;
								default:
									objId.Append('2');
									value -= 80;
									break;
							}
							first = false;
						}

						objId.Append('.');
						objId.Append(value);
						value = 0;
					}
				}
				else
				{
					if (bigValue == null)
					{
						bigValue = BigInteger.ValueOf(value);
					}
					bigValue = bigValue.ShiftLeft(7);
					bigValue = bigValue.Or(BigInteger.ValueOf(b & 0x7f));
					if ((b & 0x80) == 0)
					{
						objId.Append('.');
						objId.Append(bigValue);
						bigValue = null;
						value = 0;
					}
				}
			}

			return objId.ToString();
		}
	}
}